11
Procedure G – Procedure for the Analysis of Paints and Coatings
(cont’d)
(Reagent System: HS-HPT)
Procedure for Expected Water Content Greater than 15% (with Dilution)
1.
PREPARATION:
Remove a dilution vial, two sampling syringes, two caps and a white-capped tube from the
box. Check the contents to ensure that all items are present and intact. Remove the white cap from the reaction
tube and discard; remove the cap from the dilution vial. Insert one green water ampule into the top of the
polypropylene ampule sleeve and replace the ampule sleeve into the reaction tube with the grayish-white
ampule on the bottom.
2.
SAMPLE INTRODUCTION:
Remove the cap from an empty sampling syringe. Work the plunger on the
empty sampling syringe a few times to ensure that it slides easily. Place the tip of the syringe into the paint
sample to be tested and slowly pull back on the plunger until it reaches the stop and cannot be pulled further.
When drawing up the sample, make sure there are no air bubbles in the syringe. If air bubbles are present,
depress the plunger again and draw a second sample slowly.
Remove the syringe from the paint sample and
wipe any excess paint from the outside of the syringe with a tissue wipe, be sure not to blot the tip of the
syringe. Place a syringe cap on the syringe and weigh; record the weight (gross sample weight) to the nearest
0.1 mg.
3.
SAMPLE DILUTION:
Remove the syringe cap and insert the sampling syringe into the dilution vial and
dispense the paint sample by depressing the plunger. (Do not allow the syringe to contact the dilution solvent
when dispensing the sample.) Replace the syringe cap and reweigh the syringe and record the weight (sample
tare weight). The difference in the two weights becomes the sample weight S
1
to be used in equation 2 below.
Replace the white cap on the dilution vial and shake the vial vigorously for at least 10 seconds. Remove the
vial cap and quickly, using a new sampling syringe, draw up a sample from the solution. Wipe any excess
solution from the outside of the syringe, cap with a fresh cap and weigh the syringe. Record this weight (diluted
sample gross weight). Dispense this sample into the reaction tube. Replace the cap and reweigh the syringe
and record this weight (diluted sample tare weight). The difference in the two weights becomes the sample
weight S
2
to be used in equation 2 below. Insert the black septum (hole on top) into the reaction tube by
gripping the tube firmly and pressing down on the septum with your thumb until flush with top of the tube.
TIGHTLY
cap the tube with the holed, white cap
. NOTE: DO NOT SQUEEZE THE SIDES OF THE TUBE
WHILE INSERTING THE BLACK SEPTUM. DOING THIS WILL RESULT IN LOW READINGS.
.
4.
REACTION:
Break the bottom (gray) ampule in the tube by compressing the sides of the tube. Mix
thoroughly by shaking the tube vigorously for 30 seconds. The mixture will be seen to bubble and perhaps
foam. Allow the reaction to proceed for 2 minutes. Shake the reaction tube again for 10 seconds and let stand
for an additional 1 minute.
5.
ANALYSIS:
Press the <ON> key to activate the meter. Ensure the meter is set for "Program G" (See “Selecting
a Program” in the manual on how to change programs). Once the meter displays “tUbE”, insert the reaction
tube firmly into the opening at the bottom of the meter. The hole in the white cap must be lined up with the
metal pin extending from the inside of the hole in the meter. Push the reaction tube all the way into the meter.
Press the <READ> key on the face of the meter. The display will flash the word "CALC," then the results will
displayed in
milligrams
of water in the diluted sample. Record the results.
KEEP THE METER AND TUBE
UPRIGHT AT ALL TIMES.
6.
DISPOSAL:
Carefully remove the reaction tube from the meter. Vent tube by inserting completely into
venting cap and remove slowly.
REACTION TUBE AND CAP MUST BE UPRIGHT AND POINTED
AWAY FROM USER AND BYSTANDERS
. Tap the tube on the bench top to shake any loose glass to the
bottom of the tube, then break the top (green) ampule in the reaction tube by compressing the sides of the tube.
Shake the tube for 15 seconds. After 5 minutes, vent the tube again. Discard the tube and vial as laboratory
waste.
DO NOT REMOVE WHITE CAP.
7.
CALCULATION:
The meter is programmed to display the weight, in
milligrams
, of the water contained in the
sample introduced into the reaction tube (In this case the diluted sample). Calculate the water content in the
original paint sample in weight percent using the following equation:
Water in paint, wt. percent = (R/S
2
)(1+(2.15/S
1
))/10
(2)
where:
R = Meter reading in
milligrams
of water
S
1
= actual weight of whole paint sample, in
grams
S
2
= actual weight of diluted paint sample, in
grams
2.15 = Weight of the dilution solvent, in
grams