Page:NIOSH Manual of Analytical Methods - 6010.pdf/3

 HYDROGEN CYANIDE: METHOD 6010, Issue 2, dated 15 August 1994 - Page 3 of 5 SAMPLE PREPARATION: 5. 6.

7. 8.

Score each sampler with a file. Break sampler at score line. Transfer front and back sorbent sections to separate vials. Discard glass wool plugs separating and retaining sorbent sections. NOTE: An estimate of particulate cyanide may be obtained by analyzing the initial glass fiber filter disk as follows; however, no evaluation data are available for particulate cyanides determined in this manner. (i) Transfer the glass wool plug at the tube inlet and the glass fiber filter disk immediately behind it to a third vial. (ii) Add 10.0 mL 0.1 N NaOH to each vial. (iii) Proceed with step 8. Add 10.0 mL deionized-distilled water to each vial containing a sorbent section. Cap each vial. Allow to stand 60 minutes, with occasional agitation. Transfer to a 10-mL plastic syringe fitted with an in-line 0.45-µm filter. Collect the filtrate in a clean vial.

CALIBRATION AND QUALITY CONTROL: 9.

10.

11.

Calibrate daily with at least six working standards over the range 1 to 300 µg CN - per sample. a. Prepare a working standard solution, 1.00 µg /mL.CN -, by diluting 100 µL of calibration stock solution to 100 mL with 0.1 N NaOH. b. Pipet 0.5-, 1.00-, 1.50-, 2.00- and 2.50-mL of the working standard solution into 25-mL volumetric flasks to make 0.50-, 1.00-, 1.50-, 2.00- and 2.50- µg CN - standards. c. Analyze together with field samples and blanks (steps 12 through 19). d. Prepare calibration graph (absorbance vs. µg CN -). Determine desorption efficiency (DE) at least once for each lot of soda lime used for sampling. Prepare at least three tubes at each of five levels plus three media blanks. a. Remove and discard back sorbent section of a blank sampler. b. Inject a known amount of calibration stock solution directly onto the soda lime with a microliter syringe. c. Cap, and allow to stand overnight. d. Desorb (steps 5 through 8) and analyze together with working standards and blanks (steps 12 through 19). e. Prepare a graph of DE vs. µg CN - recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 12. 13.

14. 15.

16.

Set spectrophotometer according to manufacturer's recommendations and to conditions on p. 6010-1. Pipet a sample aliquot estimated to contain 0.5 to 2.5 µg CN - into a 25-mL volumetric flask. Alternately, to cover an unknown sample concentration range, pipet 0.5-, 1.00-, and 3.00-mL aliquots into separate 25-mL vol. flasks for each field sample. Larger or smaller aliquots may be taken, based on prior knowledge of expected analyte level. Pipet 0.5 mL 0.1 N NaOH into a 25-mL volumetric flask for reagent blank. Add one drop phenolphthalein solution to each standard or sample. NOTE: Add a little deionized-distilled water to increase volume for easier mixing. All solutions should be alkaline (pink) at this point. Starting with the reagent blank, add dropwise 0.15 N HCl, with mixing, until pink color just disappears. CAUTION: HCN may be produced. Work in hood. Immediately add 1.0 mL N-chlorosuccinimide/succinimide oxidizing reagent. Mix and let stand.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94