SC-300 Pro Kit Manual

SC-300 Pro Kit Manual
Vinmetrica SC-300 Pro Kit™
User Manual
Vinmetrica SC-300* Pro Kit is a simple and robust device that provides high accuracy in determination
of sulfite (SO2), pH and titratable acidity (TA) levels in wine. These are essential parameters to control
in the effort to make high quality wines. The Pro kit includes lab accessories for the SC-300 Analyzer.
Table of Contents:
Materials Provided in the Kit............................................................................................................... 2
Things you will need............................................................................................................................ 2
Why Test for SO2, pH and TA?............................................................................................................ 3
Theory of Operation............................................................................................................................. 4
Setup.................................................................................................................................................... 5
Setting up the SC-300 for the first time................................................................................... 5
Assembling the Pro Kit Equipment......................................................................................... 6
Burette Maintenance................................................................................................................ 8
Burette Reading ....................................................................................................................... 9
Instrument Operation....................................................................................................................... 10
Procedures........................................................................................................................................... 12
Measuring Free Sulfite (SO2) by Titration.............................................................................. 12
Measuring Total Sulfite (SO2) by Titration.............................................................................. 15
Calibration of pH ..................................................................................................................... 15
Measuring pH........................................................................................................................... 16
Measuring Titratable Acidity (TA) by Titration....................................................................... 16
Finishing up............................................................................................................................. 18
Warranties, Liabilities & Hazards.................................................................................................... 19
Appendix A - Test Mode..................................................................................................................... 20
Appendix B - Sulfite & TA Adjustments...........................................................................................22
Appendix C1 - Troubleshooting: pH and TA Issues....................................................................... 23
Appendix C2 - Troubleshooting: SO2 Issues................................................................................... 25
*
US Patent pending
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Materials provided in the kit:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Vinmetrica SC-300 SO2/pH instrument
(Part number SC-300-1)
SO2 Electrode (Part number SC-100-3),
blue polycarbonate housing
pH Electrode (Part number SC-200-3),
red polycarbonate housing
Two 5 mL syringes
Two 3 mL polyethylene transfer pipettes
One 25 mL serological sampling pipette
Figure 1. The SC-300 instrument
One 5mL serological sampling pipette
100 mL polypropylene titration beaker
SO2 Reagent set (Part number SC-100-2):
SO2 Titrant solution (0.0156N)
Acid reagent
Reactant solution
pH/TA reagent set (Part number SC-200-2):
pH 4.01 Reference solution
pH 7.00 Reference solution
TA Titrant (0.133N NaOH)
Lab Support stand (the large blue metal base with its long metal rod)
(Part number SC-300-3)
Vinmetrica Electrode Holder (Part number SC-300-8)
Double Burette Clamp (Part number SC-300-6)
10 mL Glass burette with Teflon Stopcock (with ~2 grams of Burette detergent)
(Part number SC-300-7)
Magnetic Stirrer (includes two AA batteries, stir bar and 25 mL cylindrical container)
(Part number SC-300-4)
Things you will need:
1.
2.
3.
Two standard AA batteries (alkaline type).
Distilled water, which usually can be found at your local grocery store. It’s handy to have a
wash bottle for rinsing. Rinse bottle available from Vinmetrica (Part number SC-100-17)
(Optional) 1N Sodium Hydroxide solution (if you want to do total SO2). Available from
Vinmetrica (Part number SC100-7)
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Why Test for SO2, pH and TA?
Testing for sulfite (SO2) is crucially important for making sure your wine does not spoil by
oxidation or from microbial growth. Having the proper SO2 level in your wine gives you this protection.
By monitoring your SO2 levels, you can make adjustments when needed, especially before starting
primary fermentation, after malolactic fermentation has completed, after racking or when ready to
bottle. To correctly adjust sulfite, you need values for your current "Free SO2" level and your wine's pH,
both of which can be measured with the Vinmetrica SC-300 analyzer.
The key parameter in protecting your wine is "Molecular SO2" which for most wines should be
at 0.8 ppm (mg/L) following primary fermentation. This in turn depends on the "Free SO2" (it can also
be referred to as "unbound" SO2) and the pH. Overall, you can reach your target Molecular SO2 by
measuring and adjusting your free SO2 levels and considering your wine's particular pH. See Table 1.
Table 1. Free SO2 concentrations necessary to attain 0.8 mg/L Molecular SO2 at a designated pH.
Free SO2 (ppm)
pH
13
16
21
26
32
40
50
63
79
99
125
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
We recommend using a sulfite calculator for determining how much sulfite to add to your wines
after taking a sulfite measurement with the SC-300 Pro Kit. Winemaker Magazine's Sulfite Calculator
at http://winemakermag.com/guide/sulfite can walk you through the process. See Appendix B for more
information on how to adjust your wine for sulfite.
Monitoring your wine's pH is especially important for the first few months of the wine making
process. Proper pH and Titratable Acidity (TA) levels influence mouth feel and provide wine stability.
During malolactic fermentation, the pH can increase somewhat and should be monitored. Typically,
wine pH and TA are inversely related; when pH goes up, TA goes down and vice versa. Adjustments
may be made to your wine to prevent wine instability. See Appendix B for more information on
adjustments.
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Theory of Operation:
1.
Sulfite (SO2): The SC-300, with the SO2 electrode and reagents provided, can be used to
determine sulfite levels in wine, musts, and other samples. It relies on the Ripper titration
based on the quantitative reaction of the SO2 with iodine (generated during the titration) which
oxidizes the SO2 in the sample under acid conditions.
-
-
IO3 + 5I + 6H+  3I2 + 3H2O
generation of iodine (I2) from iodate (IO3-)
-
SO2 + I2 + H2O  2I + SO3 + 2H+ reaction of SO2 and iodine
When all the SO2 is titrated at the endpoint, excess iodine appears in solution. This is detected
as current with the SO2 electrode and signaled by audible and visual indicators. The endpoint is
much more sensitive than the starch color change commonly employed for Ripper titration, and
it is sharp and clear, even when titrating red wines and musts. From the known concentration
of the titrant and its volume required to reach the endpoint, the free SO2 is simply calculated.
2.
pH and TA: The SC-300 kit also provides a pH electrode and reagents for calibration and
determination of pH and titratable acidity (TA) values in wines and other samples. The pH
value is simply determined by placing the calibrated pH electrode into a sample and reading the
value. TA is determined by titrating a 5 mL sample of wine to an endpoint pH of 8.2 with the
TA titrant (0.133N NaOH) from the syringe in the kit. From the known concentration of the TA
titrant and its volume required to reach the endpoint, the TA is simply calculated (results are in
units of g/L tartaric acid).
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Setup:
Setting up the SC-300 for the first time:
1.
The SC-300 (See Figure 1) runs on two standard AA batteries (alkaline cells recommended). To
insert the batteries, open the battery housing on the bottom of the back of the unit by removing
the two screws and gently prying off the lid. Install the batteries with the negative '-' end
contacting the coiled springs and the positive '+' end contacting the raised metal inserts then
close the housing. If desired, you can prop the unit up using its folding stand.
2.
Low Battery Detection: When the battery level is getting low, the instrument will show a low
battery icon on the upper left side of the display but continues to operate without impairment to
any function. Replace the batteries as soon as practicable. When the battery level drops too far,
the instrument does not operate. It rapidly flashes the low battery icon for 3.0 seconds, beeps
and shuts itself off.
3.
Auto Shut-off: The SC-300 shuts off after 30 minutes. If this happens unexpectedly, just press
the POWER button to resume from where you were.
4.
Electrodes: Attach the desired electrode (pH or SO2, Figures 2 & 3) via the BNC connector
protruding from the top. Be sure to secure the electrode plug to the BNC connector to insure
proper function.
Figure 2. Attach the Electrode
you are using to the BNC
connector on the SC-300
5.
Figure 3. Be sure the Electrode
attachment is screwed into place
on the BNC connector.
SO2 electrode: Remove any protective cover from the electrode tip (some electrodes are
shipped without one). This cover is for shipping protection and need not be used routinely.
Put the electrode on its side, or hang it from an electrode stand if you have one. The SO2
electrode (blue) is sturdy with its plastic housing, but do take care not to let things touch or
strike the platinum wires; they are somewhat fragile and will break if bent and straightened
repeatedly. Electrode care: When done, always rinse with DI water and let air dry. There is no
need to store the SO2 electrode in any kind of solution.
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6.
pH electrode: Attach the pH electrode via the BNC connector on the top of the SC-300 (see
Figures 2 & 3). A note about the pH electrode: The pH electrode is fragile and should always
be handled carefully. Remove the liquid storage bottle by unscrewing the cap first, then gently
pulling the bottle, followed by the cap, off the electrode. Rinse the electrode in a little distilled
water before each use. Electrode care: Do not touch the glass bulb, nor attempt to wipe it with
anything. When necessary, you may gently blot excess liquid away from the electrode surface,
but avoid directly touching it. The pH electrode should always be kept in the liquid storage
bottle with its pH storage solution (available from Vinmetrica) when not in use. Rinse the
electrode with DI water and gently blot or shake off excess water. Push the electrode through
the hole in the cap about an inch, then gently screw the bottle onto the cap so that the electrode
is in contact with the solution in the bottle.
Assembling the Pro Kit Equipment:
1.
Remove the items from their packaging: the Lab Support Stand, the Vinmetrica Electrode
Holder, the Double Burette Clamp, the 10 mL Glass Burette and the Magnetic Stirrer. Carefully
pull out the glass burette from its cardboard cylindrical container and out of its bubble wrap.
Use caution not to exert too much force on the burette as it is fragile and can break.
2.
For the burette, assemble as shown below. First, remove the attached Teflon stopcock bag
which is wrapped around the burette (See Figure 4). Open the bag, unscrew the red cap,
remove the black rubber o-ring and the red plastic washer from the stopcock assembly (See
Figure 5). Now insert the stopcock into the slot on the glass burette, it should fit snugly (See
Figure 6). The threaded section on the end of the Teflon stopcock should be protruding through
the glass burette slot. Reattach the red plastic washer onto the threaded section then the black
rubber o-ring and finally screw on the red cap (See Figure 7). Tighten appropriately, but not so
much that it is difficult to turn the valve to the open or closed positions.
Figure 4. The Burette and
its Teflon Stopcock.
3.
Figure 5. Disassembly
of Teflon Stopcock.
Figure 6. Stopcock
inserted into Burette.
Figure 7. Reattached
Teflon Stopcock red cap.
Open the Magnetic Stirrer from its packaging, then insert the double AA batteries included. For
pH measurements or SO2 & TA Titrations, you can use the 25 mL cylindrical container included
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with the magnetic stirrer. Another option is to replace the cylindrical container with the titration
beaker (Figure 8) included with the SC-300.
4.
Assemble the Lab Support Stand by attaching the long metal rod and screwing it into the large
blue metal base. We have found that adding a drop of super glue to the threads of the metal rod
can prevent loosening of the assembly. Then place the magnetic stirrer below the lab support
stand as shown below in Figure 8.
5.
To attach the Vinmetrica Electrode Holder, loosen the thumb screw on the Holder and slide it
onto the Lab Support Stand rod (Figure 9), then tighten the thumb screw to adjust it to an
appropriate height (Figure 10). Make sure the Vinmetrica logo can be read upright.
6.
Attach the Double Burette clamp to the Lab Support Stand using its thumb screw to adjust for
height, as shown in Figure 11 below. Usually with the burette attached to the Double Burette
Clamp, you may need to adjust both of them to the right height to read it properly.
Figure 8. The Magnetic
stirrer and beaker with the
pH electrode inserted into
the Electrode Holder
to the wine sample.
Figure 9. The Vinmetrica
Electrode Holder slides
onto the Lab Support
Stand.
Figure 10. The thumb
screw makes adjusting
The Vinmetrica Electrode
Holder's height easy.
Figure 11. The Double
Burette Clamp slides
easily onto the Lab
Support Stand.
7.
Carefully open the Double Burette Clamp's spring arms with your thumb and forefinger and
place the burette in between the four indentations in the double burette clamp's spring arm's
plastic knobs (See Figure 12). Slowly release the clamp spring to secure the burette between
these four spring arm plastic knobs (See Figure 13). You can adjust the burette at any time by
raising and lowering it within the spring arm clamps of the Double Burette Clamp. When
making these adjustments, hold onto the burette and do not apply too much force to it as the
burette is delicate. The burette tip can be placed into a convenient slot on the Vinmetrica
Electrode Holder (See Figure 14) to make it easier to titrate.
8.
Finally, insert the electrode that you wish to use into one of the open side slots (as seen in
Figure 8). Once the rubber neck of the electrode is sitting on top of the electrode holder, you
can press down on the rubber neck gently so the electrode is further stabilized into the slot.
You are now ready to titrate!
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Note: The magnetic stir bar that is placed within the 25 ml cylindrical container or titration
beaker can potentially damage the SO2 and pH electrodes. When adjusting the height of the
electrodes make sure that the stir bar in the beaker is below the bottom of the electrode. You do
not want the spinning magnetic stir bar to strike the SO2 or pH electrode.
Figure 12. The glass
burette should be placed
between two sets of
spring arm knobs on the
Double Burette Clamp.
Figure 13. The burette
sits firmly between the
notches of the four
spring arm knobs of the
Double Burette Clamp.
Figure 14. The glass
burette tip can be slid into
the Electrode Holder's
front open slot for
accurate titrations.
Figure 15. The Pro Kit
Assembly is complete. Go
take some measurements!
Burette Maintenance
Keep the burette clean and wash with deionized (distilled) water when you are finished using
the burette. This is especially important for TA titrations because the TA Titrant is caustic and can etch
the burette. Every so often, you will want to clean your burette with a cleaning solution to maintain
accuracy of the burette. The included ~2 grams of Burette Detergent is specially formulated to clean
glassware. The dry detergent ships in an Eppendorf tube that has markings with approximate half gram
increments. Upon first receiving the detergent, mix approximately half a gram (about an 1/8th of a
teaspoon) with about 50 milliliters (mL) of distilled water into a small bottle. We recommend capping
the bottle and shaking well for a minute or until the detergent is dissolved. Bubbles may form but the
detergent will still be effective. The detergent solution should be made fresh every time you clean the
burette, as it loses its potency quickly if stored as a liquid.
After you have run distilled water through your burette, close the stopcock, and fill with the
Burette Detergent solution. You can open and close the stopcock over a waste bucket or sink to allow
the solution to pass into the tip of the stopcock. We recommend letting this detergent solution sit in the
burette for one hour. Dispense the detergent solution then rinse the burette with distilled water twice
more. During this time we recommend opening and closing the stopcock to make sure the stopcock is
turning easily. If it is not, remove the stopcock and clean it thoroughly. Once drained, allow to hang dry
by hanging the burette upside down with the stopcock in the open position. Once the burette is dry
cover the top opening with a piece of tape. This will prevent dust from getting in that can cause
aberrations when reading the burette. Remove the tape when you're ready to titrate.
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Burette Reading
ALWAYS use eye protection and preferably gloves (latex or nitrile) when using glassware
and chemical reagents. To get the most accurate results when titrating, there are a few things to keep
in mind. We recommend reading from the bottom of the meniscus (See Figure 17 on the following
page). First, use a thick sheet of white paper, note card or the back of a business card and draw a black
band down the center of the paper about an inch and a half thick (See Figure 16). When taking a
measurement, hold the paper about an inch behind the burette and the black band about a half an inch
below the meniscus (See Figure 18). This provides a clear view of the bottom of the meniscus which
helps make a precise, consistent measurement. Second, when filling the burette make sure the titrant
(in most cases this will be either the SO2 Titrant or the TA Titrant) has completely filled the bottom of
the burette including within the tip. Sometimes bubbles can be trapped in the tip of the burette but can
usually be dislodged by opening and closing the stopcock while the burette is hovering over a waste
container. We also recommend washing a couple of milliliters of the titrant you are using through the
burette to remove any excess water or contaminants that may remain from a previous titration . Finally,
make sure there are not any large bubbles in the burette after filling. If there are, cover the top of the
burette with some saran wrap (or parafilm if you have it) and make sure the stopcock is in the closed
position. Then take the burette out of its clamp and hold the saran wrapped end tightly. Rotate and
invert the burette to allow the bubbles to move out of the column of titrant. Once the bubbles have been
displaced, you are ready to titrate.
Figure 16. On a thick white
sheet of paper or a business card,
use a black marker to draw a
band approximately an inch and
a half thick. This card will assist
you in reading the burette
accurately.
Figure 17. The Meniscus of the
water column. This curve is
formed because of interactions
of water with the glass burette.
We recommend measuring the
titrant volume from the bottom
of the meniscus. In the picture
the value is about 3.27 mL.
Figure 18. Reading the Meniscus of
the water column is easier and more
precise if you use the paper with the
black band held up an inch behind the
burette and its black band 1/2 an inch
below the meniscus. In this picture the
value from Figure 17 is further
resolved to 3.26 mL.
Before beginning the titration, record the starting titration volume, using the thick white paper
with the black band, and then begin titrating, slowly. Record the final titration volume using the same
technique. You can also checkout these websites for more burette info:
http://www.titrations.info/pipette-burette or http://www.csudh.edu/oliver/demos/buretuse/buretuse.htm
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Instrument Operation:
1.
Turn on the instrument by pressing the POWER button briefly (Note: depressing the POWER
button longer than two seconds at start-up will cause the instrument to enter Test Mode; see
Appendix A). The instrument will go through a power-up sequence. After a few seconds the
instrument will start in whatever mode was last selected. The mode is indicated by the yellow
LED panel on the left. Select the desired mode by pressing the MODE button.
2.
SO2 mode: This is for titration in determining ppm of SO2 (see below under ‘Procedures’). The
SO2 electrode must be attached [Warning: The pH electrode can be damaged by connecting it
to the instrument in SO2 mode. As a safety precaution, you must press the ENTER button after
selecting SO2 mode to confirm that the SO2 electrode is attached before the mode will be
enabled. However, scrolling through the MODE selections (such that you pass by the SO2
selection) with a pH electrode attached is safe, as long as you do not press ENTER to confirm
the SO2 mode.] After pressing ENTER, with the SO2 electrode attached, you should see the
display show a value less than 50 (usually 0.0) and the green "PROCEED" LED should be on.
3.
Precondition the SO2 Electrode: We recommend that you precondition your SO2 electrode
before you use it for the first time. With the SO2 Electrode attached and the SC-300 instrument
in SO2 Mode, place the SO2 electrode in 20 mL H2O and add 2 drops of Acid Solution. Stir
moderately. If the instrument registers the STOP condition (with the red "STOP" LED lit, the
beeper sounding and the LCD displaying a current of 50.0 or higher for longer than 5 seconds),
then the electrode should be preconditioned by allowing it to stand in this solution for a period
of time (anywhere from 15 minutes to several hours as needed) until the current drops below
50.0 and the PROCEED conditions are achieved (with the green "PROCEED" LED lit and no
sound is coming from the instrument). Normally, this preconditioning only needs to be done
for the first time the electrode is used. See the Appendix C2 for additional testing of the SO2
function.
4.
pH mode: In this mode, the meter measures the pH. The pH electrode must be attached. If the
instrument has not yet been calibrated, the message “doCal” scrolls across the screen, and you
need to do a calibration (see Calibration of pH below). We recommend re- calibrating the
instrument for pH once each day of use. Warning: Be careful not to press ENTER when the pH
electrode is attached while the instrument is in SO2 mode, as this can potentially damage the pH
electrode. If this does happen, and the pH electrode does not respond correctly, place it into the
pH 4 Reference solution for an hour and it should return to normal function.
5.
TA mode: This is for titration in determining titratable acidity (TA). As in the pH mode, the pH
is displayed and the pH electrode must be attached. The green (“PROCEED”) LED is lit if the
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pH is below 8.2, while the red "STOP" LED is lit if the pH is 8.2 or greater. (see below under
Measuring TA by Titration )
6.
CAL mode: This is for calibrating the pH electrode, which must be attached. The display
initially shows CAL for a few seconds as it prepares to read pH and lets readings settle.
Thereafter, the display shows the measured pH level with two decimal places.
7.
Calibration works with one of the following reference calibration sets:
pH 4.01 and 7.00 or “4/7”
pH 7.00 and 10.00 or “7/10”
pH 3.00 and 7.00 or “3/7”
Vinmetrica recommends use of the pH 4/7 Reference Solution set provided with the kit.
8.
The magnetic stirrer has two modes. Pressing the "light bulb" button on the magnetic stirrer
activates a light underneath the sample and the stirrer. The power button activates just the stirrer.
After pressing either button, the stirrer remains active for 60 seconds, a feature to conserve its
batteries. If during the titration it turns off, simply press the button again for it to continue. We
recommend using the light mode because it helps us indicate when the stirrer stops. Plus when
doing TA titrations watching the wine turn from deep red to dark green is cool!
Note: When using the magnetic stirrer, be sure that the electrode does not touch the spinning
stir bar as this can potentially damage the glass bulb of the pH electrode or the platinum wires of the
SO2 electrode. If you are using the Vinmetrica Electrode Holder, adjust the electrode’s height so that its
probe end is above the level of the stir bar.
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Procedures
Measuring Free SO2 by Titration:
1.
Make sure the SO2 electrode is attached and preconditioned as described in step 3 of the
Instrument Operation section. Turn on the instrument and select SO2 mode with the MODE
button. Press ENTER to confirm selection of SO2 mode (Figure 19).
Figure 19. Once in SO2
MODE the instrument
should read
'Press Enter'
Press ENTER to activate
SO2 MODE.
2.
Figure 20. Withdraw
the titrant from its bottle
using a clean 5 mL
syringe. If you are using
the glass burette, use the
syringe to fill it.
Figure 21. Dispense 25
mL of your wine into the
titration beaker using the
25 mL sampling pipette.
Make sure this is clean
before putting the pipette
into your wine container!
Figure 22. The transfer
pipette. One full squeeze
of the transfer pipette in
either the Acid solution
or Reactant should be
approximately 2 mL.
Fill the syringe by drawing up the SO2 Titrant (the bottle with the blue label) (Figure 20).
Expel bubbles and set the plunger on the syringe to a readable point, preferably the 5.0 mL
point. Make sure the outside of the syringe is dry, to minimize any inaccuracies. [Note: the 5.0
mL setting allows determination of up to 100 ppm SO2 in a standard 25 mL wine sample.] If
using the burette, use the syringe to dispense the SO2 titrant into the top of the burette. Make
sure the burette stopcock is in the closed position (where the red handle is horizontal). When
filling the burette make sure the SO2 titrant has completely filled the bottom of the burette
including the tip. Sometimes bubbles can be trapped in the tip of the burette but can usually be
dislodged by opening and closing the stopcock while the burette is above a waste container. If
you spill any titrant on the outside of the burette, be sure to clean it up with a paper towel or dry
rag. If the spilled titrant is not cleaned from the outside of the burette you may introduce these
spilled titrant droplets into the wine sample leading to an inaccurate reading. Be sure to record
your starting burette or syringe volume; refer to 'Burette Reading' section under the Setup
section for how to measure accurately.
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3.
Place 25 mL of wine or must in the titration vessel. We recommend using the 25 mL sampling
pipette provided in the kit: draw the sample up to the 0 mL mark, and then dispense the sample
into your titration vessel by letting the tip of the pipette touch the side of the vessel while the
sample drains (See Figure 21). NEVER pipette any reagents by mouth! Also make sure the
pipette you are using is completely clean before submerging into your wine sample.
4.
Using the transfer pipettes (see Figure 22), add about 2 mL Acid Reagent and 2 mL Reactant
solution to the titration beaker (the two transfer pipettes should come with red and yellow labels,
with red for the Acid Reagent and yellow for the Reactant). It is not necessary to be extremely
accurate in this step; with these pipettes, 2 mL is roughly the amount that fills the pipette up to
the 2 mL mark after a single thorough squeeze of the bulb. To preserve the shelf life of these
reagents take care not to cross contaminate the transfer pipettes. If they do get contaminated
rinse them off with distilled water and let air dry. Caution: the Acid reagent is corrosive and
can cause damage to clothing, skin and eyes. The Reactant solution should not be ingested.
ALWAYS use safety glasses! We recommend the use of laboratory latex or nitrile gloves
during this procedure. If any solutions contact skin or eyes, flush with plenty of water.
5.
If you are using a magnetic stirrer, turn it on to stir at a moderate rate. The Magnetic Stirrer
provided with the SC-300 Pro Kit operates at a suitable preset speed. Make sure your electrode
is not being struck by the spinning stir bar. To prevent this, we recommend using the Vinmetrica
Electrode Holder to stabilize your electrode.
6.
Rinse the electrode briefly with distilled water. Insert the electrode into the titration beaker so
that the tip is completely submerged to just above the circulation gaps (cutouts at the tip of the
electrode) but above the level of the stir bar (approximately half an inch from the bottom of the
titration beaker). If you are using the Vinmetrica Electrode Holder adjust it to a similar level.
7.
If you are stirring manually, begin now; use a constant moderate swirling motion. If the
electrode is not held in a stand, hold it against the side of the vessel with one finger and grasp
the vessel with the remaining fingers so that the two move together. (See Figure 23).
8.
Verify that the current is less than 50 and the green (“PROCEED”) LED is lit (See Figure 24).
If the current is greater than this, and/or the red (“STOP”) LED is lit and the buzzer sounds,
your sample has less than 2 ppm SO2 and there is no need to proceed. (Verify that your SO2 has
been preconditioned by following step 3 in the Instrument Operation section of the manual).
9.
Titrate the sample by adding the SO2 Titrant drop wise from the syringe (See Figure 23) or from
the burette (See Figure 24), being sure to note the starting volume mark on the syringe or
burette. Try to accomplish the titration as rapidly as possible (in 3 minutes or less), but be
careful near the endpoint so as not to overrun it – here, dispense one or two drops at a time. Be
sure to maintain stirring or swirling throughout the entire procedure. If the magnetic stirrer
turns off, turn it back on.
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Figure 23. Manual stirring
technique. Hold the electrode
against the side of the titration
beaker and swirl gently; add
SO2 Titrant with other hand.
Figure 24. Automated stirring
technique. Turn on the
magnetic stirrer; add SO2
Titrant by slowly opening the
burette stopcock valve.
Figure 25. Make sure
Figure 26. Once the device
that the "PROCEED"
beeps for 15 seconds or 20
LED is lit. You should be
sets of "beep-beep"
reading close to 0.0 when
you are done with the
you first start. You are
titration. The red "STOP"
now ready to titrate!
LED will also remain lit.
10.
During the titration, the LCD display will show transient currents, the red "STOP" LED will
briefly illuminate, and the beeper will sound (“beep-beep!”). These transient indicators will last
longer and longer as you approach the endpoint (Figure 26). Take the endpoint as the first
addition of Titrant that causes the display to exceed 50, and the red LED and beeper to stay on,
for longer than 15 seconds (or a count of 20 sets of "beep-beep"). It is important to maintain
stirring or swirling to detect the endpoint well. Do not add titrant while the red "STOP" LED is
lit. Read the remaining titrant volume off of the syringe or burette.
11.
Calculate the volume of titrant used "V" ( using the Syringe: Starting volume minus final
volume, e.g.; Burette: final volume minus starting volume), e.g., V = 5.0 mL - 3.5 mL = 1.5 mL )
12.
The free SO2 content is calculated in units of parts per million (ppm) as:
ppm Free SO2 =
64 * V * N * 1000
2*S
Where V = mL SO2 Titrant needed to reach the endpoint; N = normality (concentration) of the
Titrant; and S = mL of your wine sample. 1 If you use a 25 mL wine sample as directed and the
SO2 Titrant's normality is 0.0156 as supplied in the kit, then the calculation is simply:
ppm Free SO2 = 20 * V (i.e. 20 times V)
1
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Measuring Total SO2 by Titration (optional - requires 1N NaOH):
1.
Place 25 mL wine or must in the titration vessel (See Figure 21).
2.
Add 10ml 1N sodium hydroxide (Vinmetrica Part number SC-100-17) and mix well. Let stand
approximately 10 minutes.
3.
Using the transfer pipettes, add approximately 8 mL of the Acid Reagent and 2 mL of the
Reactant solution to the vessel. Remember that if you are using the transfer pipettes in the kit, 2
mL is the amount that fills the bulb with a vigorous squeeze, so dispense four of these for the
Acid Reagent.
4.
Proceed from step 5 in the Free SO2 procedure above. The result calculated will be total SO2,
rather than free SO2 in parts per million (ppm).
Calibration of pH:
1.
Be sure the pH electrode is attached to the unit, then select CAL mode by pressing the MODE
button until the CAL LED illuminates.
2.
Choose a calibration set that corresponds to the range you are working in. Usually for wine this
will be at pH values below 4, so use the 4/7 set. If you have a source of a pH 3.00 reference
solution, you can use this in place of pH 4.
3.
Rinse the electrode with DI water, shake or blot off excess liquid gently, and place the electrode
into a small vessel (like the pH 4 Reference Solution cap) containing one of the reference
solutions (e.g. pH 4.01).
4.
The instrument will determine which calibration solution is being used, and will display the
apparent pH value. This may be different by as much as 0.40 from the value of the reference
solution (e.g. the LCD may display 4.41 when the pH electrode is sitting in the pH 4.01
reference solution). When the pH level is sensed as stable, the nominal value is shown on the
display, flashing, and the “CAL” LED flashes to convey that calibration for this value is ready.
Press the ENTER button to accept the calibration.
5.
The display stops flashing, scrolling the message 'Good CAl', and four beeps are rapidly
sounded to indicate success. [Note: if an error occurs during this process, the message
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'BAd CAl' will scroll and a single beep will sound; the instrument will then continue to wait
for a stable pH level. Repeat step 4.] Following the 'Good CAl' message, the display will
now show the calibrated pH value.
6.
Now rinse the electrode again and place it in the second member of the calibration set (e.g., pH
7.00 reference solution). Repeat the process to get a second 'Good CAl' message. Exit into
pH or TA mode.
Measuring pH:
1.
Make sure the pH electrode is attached. Calibrate it as described above, if necessary. Select pH
mode with the MODE button.
2.
Rinse the pH electrode with DI water. Gently shake off or carefully blot away excess liquid.
3.
Place the electrode in the solution to be tested. Be careful not to let the electrode strike any
surfaces.
4.
Allow the pH reading to stabilize. Typically this takes about 10-15 seconds. Read the pH value
on the display. Note: Once you've completed the pH test you can start the TA test. Start
with precisely a 5 mL wine sample before beginning the pH & TA combined measurement.
You can use a clean 5 mL sampling pipette provided in the kit to pipette this amount.
Measuring Titratable Acidity (TA) by Titration:
1.
If you are working with a sample of must, we recommend homogenizing your sample in a
blender before proceeding; otherwise your TA values can be very inaccurate. Take 100 mL or
more of your must and put it in a blender on high for 30 seconds. Allow solids to settle for 2
minutes before sampling or use a cheese cloth or mesh strainer to remove solids.
2.
Fill the syringe by drawing up the TA Titrant (0.133N NaOH). Expel bubbles and set the
plunger on the syringe to a readable point, preferably the 5.0 mL point. [Note: the 5.0 mL
setting allows determination of up to 10 g/L TA in a standard 5 mL wine sample.] If you are
using the burette, use the syringe to dispense the TA titrant into the top of the burette. Make
sure the burette stopcock is in the closed (the red handle is horizontal) position. When filling
the burette make sure the TA titrant has completely filled the bottom of the burette including the
tip. Sometimes bubbles can be trapped in the tip of the burette but can usually be dislodged by
opening and closing the stopcock while the burette is above a waste container. If you spill any
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TA titrant on the outside of the burette, be sure to clean it up with a paper towel or dry rag. If
the spilled titrant is not cleaned from the outside of the burette you may introduce these spilled
titrant droplets into the wine sample leading to an inaccurate reading. Be sure to record your
starting burette or syringe volume. Caution: the TA Titrant is caustic and can cause damage
to clothing, skin and eyes. We recommend use of laboratory safety glasses and latex or
nitrile gloves during this procedure. If any solutions contact skin or eyes, flush with
plenty of water.
3.
Place 5.0 mL wine or must in the titration vessel (100 mL polypropylene beaker). We
recommend using the 5 mL pipette provided in the kit: draw sample up to the 0 mL mark, then
dispense the sample into your titration vessel by letting the tip of the pipette touch the side of
the vessel while the sample drains. For best accuracy, do not blow out the liquid that remains in
the tip. Add about 15 ml of deionized (DI) water (distilled water).
4.
Turn on the instrument. Make sure the pH electrode is attached. If necessary, calibrate it as
described above. Select TA mode with the MODE button.
5.
If you are using a magnetic stirrer, turn it on to stir at a moderate rate. Be sure the stir bar will
not strike the electrode in the following steps. (See Figure 28)
6.
Rinse the electrode briefly with DI water. Insert the electrode into the titration vessel so that the
tip is fully submerged to just above the circulation gaps (cutouts at the tip of the electrode).
7.
If you are stirring manually, begin now; use a moderate swirling motion. If the electrode is not
held in a stand, hold it against the side of the vessel with one finger and grasp the vessel with
the remaining fingers so that the two move together while swirling (See Figure 27).
Figure 27. Manual stirring
Figure 28. Automated
technique. Hold the
stirring technique. Turn on
electrode against the side of the magnetic stirrer; add
the titration beaker and
TA Titrant by slowly
swirl gently; add TA Titrant
opening the burette
with other hand.
stopcock valve.
SC-300 Pro Kit Manual
17
Figure 29. Make sure that
the green "PROCEED"
LED is lit. You should be
reading a pH close to what
you expect your wine is at.
You are ready to titrate!
Figure 30. Once the pH
arrives at or passes 8.20
you are done with the
titration. The red "STOP"
LED will be lit and the
instrument will be beeping
Version 1.5
8.
Verify that the pH is less than 7 and the green (“PROCEED”) LED is lit (see Figure 29). If the
pH is greater than this, and/or the red (“STOP”) LED is lit and the beeper sounds, your sample
has less than 0.1g/L TA and there is no need to proceed.
9.
Titrate the sample by adding the TA Titrant drop wise from the syringe or burette, being sure to
note the starting volume mark on the syringe or burette. During the titration, the pH will
gradually rise from its starting value (below 4 usually). As you approach pH 7, go slowly in
adding successive drops of titrant so as not to overrun the endpoint. Be sure to mix thoroughly
after each successive drop of titrant. Take the endpoint as the first addition of TA Titrant that
causes the pH to stay above 8.2 for longer than 15 seconds. The red "STOP" LED and the
beeper will provide additional indication of the endpoint (See Figure 30). Read the endpoint
volume off of the syringe or burette. To silence the beeper after the endpoint, select pH mode,
or turn off the instrument.
10.
Calculate the TA value as:
where V = mL Titrant needed to reach the endpoint; 0.133 = normality of the Titrant, S = mL
sample. If you use 5 mL of sample as directed, and the Titrant is 0.133 N as supplied, then the
calculation is simply
Finishing up:
1.
Turn off the instrument.
2.
Rinse the SO2 electrode and syringe with distilled water. Let air dry.
3.
Be sure to rinse and store the pH electrode in its storage solution as directed under 'Setting up
the SC-300 for the first time' item 6.
4.
Store all reagents tightly capped and away from heat and sunlight.
5.
Discard waste samples and solutions in accordance with local regulations. Acidic solutions can
be neutralized by slow addition of baking soda (sodium bicarbonate) with stirring until
effervescence ceases.
Technical assistance: [email protected]
SC-300 Pro Kit Manual
18
tel. 760-494-0597
Version 1.5
WARRANTIES AND LIABILITIES
1.
The materials provided in the kit, as described on pages 1 and 2 above, (“Materials”) are
warranted as follows: The SC-300 instrument, electrodes and non-reagent accessories are
warranted against defects in workmanship for 12 months from date of purchase. The reagents
are warranted to perform as described herein up until any stated expiration date or 6 months
after purchase, whichever is later. THE WARRANTIES IN THESE TERMS AND
CONDITIONS ARE IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF MERCHANTABILITY,
NONINFRINGEMENT, OR FITNESS FOR A PARTICULAR PURPOSE, SAID
WARRANTIES BEING EXPRESSLY DISCLAIMED.
2.
Buyer agrees that its sole and exclusive remedy against Vinmetrica shall be limited to the
repair and replacement of Materials or parts of Materials, provided Vinmetrica is promptly
notified in writing, prior to the expiration of the warranty period specified above, of any
defect. Vinmetrica’s liability for any damages due Buyer shall be limited to the purchase price
of the Materials.
3.
VINMETRICA'S MAXIMUM LIABILITY FOR ALL DIRECT DAMAGES, INCLUDING
WITHOUT LIMITATION CONTRACT DAMAGES AND DAMAGES FOR INJURIES TO
PERSONS OR PROPERTY, WHETHER ARISING FROM VINMETRICA’S BREACH OF
THESE TERMS AND CONDITIONS, BREACH OF WARRANTY, NEGLIGENCE, STRICT
LIABILITY, OR OTHER TORT WITH RESPECT TO THE MATERIALS, OR ANY
SERVICES IN CONNECTION WITH THE MATERIALS, IS LIMITED TO AN AMOUNT
NOT TO EXCEED THE PRICE OF THE MATERIALS. IN NO EVENT SHALL
VINMETRICA BE LIABLE TO BUYER FOR ANY INCIDENTAL, CONSEQUENTIAL OR
SPECIAL DAMAGES, INCLUDING WITHOUT LIMITATION LOST REVENUES AND
PROFITS.
HAZARDS AND TOXICITY
All Materials offered by Vinmetrica are intended for use by individuals who are familiar with
laboratory procedures and their potential hazards. The Materials contain chemicals which may be
harmful if misused. Due care should be exercised with all Materials to prevent direct human contact.
Glassware can break and chemicals can splash during experiments; Always use safety glasses. We
strongly recommend using nitrile or latex gloves and wearing long pants, long sleeves and closed toed
shoes. Keep out of reach of children.
Vinmetrica
1945 Camino Vida Roble, Suite I - Carlsbad, CA 92008
www.vinmetrica.com (760) 494-0597 [email protected]
Copyright 2010-13. Sportsman Consulting, LLC DBA Vinmetrica. All rights reserved.
SC-300 Pro Kit Manual
19
Version 1.5
Appendix A - Test Mode
Test Mode provides various special functions that may be useful in testing the device, for example, if
troubleshooting is necessary.
•
Test Mode is entered when the POWER button is pressed longer than 2 seconds while turning
the instrument on. Remove the pH electrode if it is attached.
•
Test Mode is organized into sections. Press the POWER button briefly to move to the next
section. After the last section, Test Mode restarts the first. WARNING! DO NOT MOVE
THROUGH SECTIONS WITH THE pH PROBE ATTACHED! This can damage the
electrode. Only connect the pH electrode if needed in section 2 or 4. Always remove the pH
electrode before leaving these sections.
•
Combinations of the yellow MODE LEDs are illuminated to indicate the section number as
shown in the table below.
•
The Stop LED (red) is illuminated when an error is detected by the instrument The Proceed
LED (green) is illuminated to indicate no error detected. The green LED does not guarantee
proper functioning; it only indicates that no problem could be automatically detected. The user
should make careful observations to discern proper operation.
•
To exit Test Mode, hold the POWER button down (5-10 seconds) until the instrument shuts off.
If the device does not shut off after 10 seconds of holding down the button, move to the next
section by releasing, then pressing again the POWER button briefly; then try to exit again.
Yellow
LEDs
Section
1. Version
Equipment Required
Description
None.
The version number of the instrument
software is displayed.
The instrument goes through a
continuous “burn-in” cycle, exercising
relay, sound, LEDs, and display.
2. Burn-in
None
3. pH
pH probe or precision
voltage source. Do
not exceed +/- 0.5 V.
An uncalibrated pH level is shown in two
alternating parts. First, the integer
portion of pH level is shown (1 to 14).
Next, three decimal places are shown.
Readings above 14.000 are shown as "---".
Readings below 0.000 are shown as
" ___".
4. SO2
SO2 probe or SO2
probe simulator ( e.g.,
450 kOhm resistor)
The SO2 current in nanoamperes is
displayed. For values under 10, one
decimal place is shown.
SC-300 Pro Kit Manual
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Version 1.5
Yellow
LEDs
Section
Equipment Required
Description
5. pH
Voltage
pH probe or precision
voltage source. Do
not exceed +/- 0.5 V.
The raw voltage output from the
instrument's pH amplifier is displayed as
X.XX volts. Readings can range from
0.00 to 4.10.
6. SO2
Voltage
SO2 probe or
SO2 probe simulator.
The raw voltage output from the
instrument's current amplifier is
displayed as X.XX volts. (.XXX if less
than 1.00)
7. DAC
Test
None.
Disconnect probe.
The Digital-Analog Converter (DAC) is
cycled through its 32 levels. Note: Ignore
red LED error indication.
8. Battery
Voltage
Install two AA
batteries
The battery voltage is displayed as X.XX
volts.
9. Character None.
Set
Every ASCII character (space) to ~ is
displayed. Due to the limitations of the
7-segment format, some characters are
not used by the software.
10. Number
Display
None.
The display cycles through showing
every possible digit and every decimal
point.
11. Sound
Test
None.
The beeper is turned on continuously.
SC-300 Pro Kit Manual
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Version 1.5
Appendix B - Sulfite and TA Adjustments
Using the Winemaker Magazine Sulfite Calculator:
Winemaker Magazine's Sulfite Calculator at http://winemakermag.com/guide/sulfite is an
excellent tool for calculating how much sulfite should be added to your wine. We will briefly go over
the process here for some clarification.
First, select a 'Preferred method of Sulfite addition:'; we recommend using a 10% solution of
Potassium metabisulfite (KMBS). [You can prepare this solution by weighing out 10g of KMBS and
dissolving it in a FINAL volume of 100 mL DI water.] Next choose the wine type (red or white). Keep
the 'Desired Molecular SO2 at 0.8 mg/L' and enter your wine's pH value (hit your keyboard's 'Enter'
button after entering the value). One thing to notice is that after entering in your 'Desired molecular
SO2' and your wine's pH, the calculator will ask you to enter the 'Desired level of free SO2'. The value
you should enter for this field should appear in the 'Notes:' section, within the following text: "1. The
recommended level of free SO2 for this type of wine, molecular SO2 & pH is: [your value] mg/L".
Then input the "Current level of Free SO2" which you determined from measuring Free SO2 with the
Vinmetrica SC-300. Finally, enter the "volume of wine to be corrected". Choose liters or gallons; we
prefer "liters" because the answer is returned in mL. The 'Amount of sulfite to be added:', should be in
mL or fluid ounces of 10% sulfite solution or in grams if you use sulfite powder as your sulfite additive.
We recommend double checking your calculations, and choosing the appropriate 'Desired
molecular SO2' level (usually 0.8 mg/L after primary fermentation). Once you have added the amount
of sulfite that fits to your methods, stir your wine thoroughly and take another SO2 measurement. If the
measurement matches the 'Desired level of free SO2' then you are done, otherwise make incremental
additions and repeated SO2 measurements until you reach your desired level.
Adjusting TA in your wine:
We recommend adjusting your titratable acidity levels by adding tartaric acid (for non-grape
wines fruit acids can be used but, remember, additions of malic acid, if done improperly, can make
wine overly sour or tart). If your wine's pH is too high, indicating low acidity, and TA levels too low,
you can add tartaric acid to decrease the pH and increase TA. By measuring TA, you can figure out
how much tartaric acid to add without making your wine overly tart or sharp. If your TA is too high,
some winemakers like to do a "cold stabilization" which results in precipitation of tartaric acid before
bottling to decrease the tartness. Another method to decreasing your TA level is to add calcium
carbonate or potassium carbonate (CaCO3 or K2CO3). For the chemically inclined, we recommend
Zoecklein's book "Wine Analysis and Production" which goes over theory and practice behind these
adjustment techniques and many wine analytical techniques.
SC-300 Pro Kit Manual
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Appendix C1 - Troubleshooting: pH and TA Issues
I can’t calibrate the pH on my SC-300
When calibrating your pH electrode, remember these points:
1.
The displayed pH may not be correct until after you press ENTER.
2.
If the instrument signals stable pH but displays “Bad Cal” after pressing ENTER, try laying it
flat on the table; when the next stable signal is signaled, press the ENTER button quickly
without handling the instrument. Sometimes the instrument may pick up noise from its
environment, particularly if you handle it at the last second, while it’s trying to achieve a stable
reading. This sensitivity is usually only an issue during calibration.
3.
If values appear to drift, leave the electrode in the pH 4.01 reference solution for 30 minutes.
4.
If you intend to read pH values in samples that are at a different temperature than ambient, it’s
best to have your reference solutions at that temperature also before calibrating.
5.
Finally refer to the next FAQ question if these steps do not help.
What should I do if my pH electrode is acting sluggish, erratic and is difficult to
calibrate?
Reconditioning and cleaning of pH electrodes:
Even in normal use and storage, performance of pH electrodes may show deterioration over
time, which typically shows up as noisy, erratic or sluggish electrode readings, and/or difficulty
calibrating. Assuming the meter itself is working (see “Meter test” below), then there are two main
causes for this:
1.
Clogging of the reference junction (most likely).
2.
Fouling of the glass membrane (happens occasionally, or after prolonged service).
The following procedures will often provide renewed stability and pH sensitivity. If the electrode
cannot be restored by one of these methods, it needs to be replaced.
Unblocking the reference junction:
The reference electrode junction is usually the problem when the electrode can’t calibrate in its
expected ranges. This junction is a fine-pored frit that allows electrical contact of a reference electrode
with the solution being tested. It can become clogged over time.
SC-300 Pro Kit Manual
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Version 1.5
1.
Soak electrode in hot (NOT boiling!) water, about 60 °C, for 5 – 10 mins. Allow to cool to
room temperature then place in pH 4 reference solution for 5 minutes. Try to recalibrate. If this
does not work, try remedy 2.
2.
Place the pH electrode into the pH storage solution (available from Vinmetrica part number SC200-10 or a solution of 2.5M KCl with optionally added 0.01M KHP) at 60 °C and allow
electrode and solution to cool to room temperature, then place in pH 4 reference solution for 5
minutes. Try to recalibrate. If this doesn't work, try remedy 3.
3.
Soak in 0.1M HCl (note: this can be made by diluting 1 mL of the SO2 Acid Solution with 20
mL DI water) or 0.1M nitric acid (HNO3) for 1 hour. Rinse with DI water, then place in pH 4
reference solution for 5 minutes. Try to recalibrate. If this does not work, try remedy 4.
4.
Soak in 1:10 dilution of bleach in a 0.1 – 0.05 % solution of liquid detergent in hot water with
vigorous stirring for 15 mins. Rinse with DI water, then place in pH 4 reference solution for 5
minutes. Try to recalibrate.
Cleaning the pH electrode’s glass membrane:
The glass bulb is a thin membrane of a special kind of glass that actually does the job of
responding to the pH of the solution. It can sometimes become dirty and poorly responsive.
1.
Immerse electrode tip in 0.1M HCl ( see above for how to make) for about 15 secs., rinse with
distilled water, then immerse in 0.1M NaOH (you can use a little of your TA Titrant for this) for
another 15 sec. Cycle the electrode through these solutions several times (rinsing with DI water
in between), then rinse and check for performance in pH buffer 4.00 and 7.00.
2.
Some other tricks: protein deposits can be removed by soaking in 1 % pepsin in 0.1M HCl for
15 mins. Inorganic deposits may be removed by soaking in 0.1M tetrasodium EDTA solution
for 15 mins. Grease and oil deposits may be removed by rinsing the electrode in mild detergent
in methanol solution.
Instrument test:
You want to be sure that the instrument is responding correctly. A quick test is to simply short
out the electrode connector:
1.
Disconnect the electrode and put the instrument in pH mode.
2.
Short out the electrode connector at the top of the instrument using something metallic, like a
paper clip or pin, to connect the center hole of the connector to its outer sheath.
3.
With the input shorted out, the reading should be pH 7.00 +/- 0.05. If out of this range, the
meter is probably bad. Contact us at [email protected] or tel. 760-494-0597.
4.
Bear in mind that this test is not 100% fool-proof (the instrument might still have trouble
reading pH values different from 7.00), but generally if this test passes, it is much more likely
to be an electrode problem.
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Version 1.5
Help! What do I do if my pH electrode was attached to my SC-300 when in SO2
mode? Is my pH electrode broken?
No, don’t worry, your pH meter should still work. To fix it, leave your pH electrode in the pH 4
reference solution for an hour and it should return to normal function. Enabling SO2 mode with the pH
electrode attached could cause the pH electrode to wear out more quickly. Because of its design, SO2
mode cannot be accessed unless you press ‘ENTER’ after pressing the ‘MODE’ button, this is another
safeguard we installed to prevent this from becoming a problem.
Appendix C2 - Troubleshooting: SO2 Issues
How stable are the reagents?
The SO2 reagents and the pH/TA reagents are all warranted to last for 6 months. We have found
that, in fact, except the TA Titrant, our reagents are stable for well over 12 months if stored tightly
capped, out of the heat and direct sunlight. And of course, these reagents will last much longer if not
cross-contaminated with each other!
How can I check the accuracy of my reagents?
It’s rare that the SO2 reagents go bad, but if you are concerned about it, run the 'Ascorbic Acid
Test' method located in the FAQ section of the website to check your SO2 reagents. If you are worried
about your TA Titrant, you can run the 'KHP test', also located on the Vinmetrica website in the FAQ
section under 'Manuals, Tests and How To Videos' at vinmetrica.com/FAQ/
I’m getting strange results in SO2 mode; how do I know if my instrument is
working correctly?
For SO2 measurements with the SC-300, there are several quick tests you can do to make sure
the instrument is not faulty.
1.
Be sure the battery is good per the manual’s instructions.
2.
Short out the terminals on the BNC connector at the back, using a paper clip or similar metal
piece. The device should indicate “STOP” with its red LED and buzzer or beeper. If this does
not happen there may be a problem with the instrument; contact us for more information.
SC-300 Pro Kit Manual
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Version 1.5
3.
Connect the electrode and put it in about 20 mL of distilled water; add about 1 ml (half a bulb
squeeze) of each of the acid solution and the reactant and swirl in the usual way keeping
constant motion. The instrument may or may not indicate STOP as above. If it does not, add a
drop of the SO2 Titrant solution. This should make the STOP condition occur. [If it doesn't you
may have an electrode problem read in the next section below how to fix this.] Now add one
drop of a concentrated sulfite solution (1-10% is fine) and verify that the STOP signal ends and
the PROCEED light illuminates. If this happens, your electrode is probably OK as well.
4.
Finally, you can check your SO2 reagents with the ascorbic acid (vitamin C) test located on our
website vinmetrica.com/FAQ.
Sometimes when the SO2 electrode is first shipped it can be shipped “hot”. A hot electrode is
one that is overly sensitive, this can be fixed by pre-conditioning your SO2 electrode. To pre-condition
your electrode:
1.
First, attach the SO2 electrode to the SC-300 analyzer, turn the power on and press the MODE
button until the instrument is in SO2 mode then press ENTER. Put 20 mL of distilled water (deionized water) in a beaker and add half a bulb squeeze of the acid solution, half a bulb squeeze
of the reactant solution and let the SO2 electrode sit in this solution.
2.
Then add one drop of 10% potassium metabisulfite solution (KMBS) to the beaker with the
electrode in it. Swirl gently. The instrument LCD should now read 0.0 (in units of nanoamps) or
close to it. If it is reading significantly higher than 20 on the screen, let the electrode sit in the
solution for half an hour.
3.
After half an hour rinse the electrode with distilled water. Put it in about 20 mL of distilled
water. Again add half a bulb squeeze of each of the acid solution and the reactant and swirl in
the usual way keeping constant motion. The instrument may or may not indicate STOP as
above. If it does not, add a drop of the SO2 Titrant solution. This should make the STOP
condition occur. [If it doesn't you may have an electrode problem]
4.
Now add one drop of KMBS solution (1-10% is fine), swirl and verify that the STOP signal
ends and the PROCEED light illuminates. If this is the case your electrode has been
conditioned. If the electrode is still “hot” and the PROCEED light does not illuminate let it sit
in 20 mL of distilled water with a half bulb full of the acid solution for a few hours. Now repeat
the test from step 3. If it works great! If not call us and we will try to troubleshoot or replace
your electrode.
Technical assistance: [email protected]
SC-300 Pro Kit Manual
26
tel. 760-494-0597
Version 1.5
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