47
Section 13 Sulfide–1
13.1 Micro Dist™ Method
CAUTION
Chemical inhalation hazard. To avoid potential exposure to
hydrogen sulfide gas (H
2
S), the manufacturer recommends
operating the Micro Dist under a fume hood.
ATTENTION
Risque d'inhalation de produit chimique. Pour éviter le contact
potentiel avec du gaz de sulfure d'hydrogène (H2S), le
fabricant recommande d'utiliser le Micro Dist sous une hotte
aspirante.
CAUTION
Chemical hazard. Always follow appropriate laboratory safety
procedures when handling chemicals. Always wear personal
protective equipment appropriate for the chemicals you are
handling.
ATTENTION
Danger chimique. Suivez toujours les procédures de
laboratoire de sécurité lors de l'utilisation de produits
chimiques. Veuillez toujours porter l'équipement de protection
personnel approprié pour les produits chimiques que vous
manipulez.
This is a method for distilling solid and liquid samples containing 0.2
to 50 mg/kg acid-soluble sulfide, for iodometric determination.
In the following procedure,
D and M refer to the marks on the ends
of the collector tube.
D means 'distillation' or 'discarded' end and M
means 'measuring' end. See Figure 2 on page 13.
1. Set the controller to 120
°C. Allow the heater block to warm up.
This will take about 45 minutes.
2. With the
M end up, put the required number of collector tubes
into the collector tube rack. When using the Pre-filled collector
tubes, re-seal the foil pack after removing the tubes if there are
any left. When using the User-Fill collector tubes, fill and cap
the tubes before using.
3. Put the required number of sample tubes into the sample tube
rack; up to 21 for one block. Place 1.0 g of solid sample or 5.5
mL of standard solution into each sample tube. For solid
samples, add about 5.0 mL deionized water.
4. Add between 0.5 to 1.0 g of soil or sludge to 5 mL of DI water. If
the sample is high in organics, a smaller sample size or less DI
water may be required. Foaming or caking of the membrane is
often eliminated by the above measures. If not, see Running
Solid Samples with Micro Dist on page 70.
5. In order to both release the free sulfide as H
2
S (g) and to digest
complexed sulfides during the digestion/ distillation, add 0.45
mL of 9.0 M sulfuric acid solution to each sample tube using the
supplied automatic pipet.
Note: When running an unknown matrix for the first time it is advisable
to determine the approximate amount of concentrated sulfuric required
to reduce the pH of the sample to less than or equal to 1. The volume
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