HYD RO GE N C YAN IDE: ME TH OD 6017, Issue 1, dated 1 5 Ma rch 2003 - Page 3 of 5 7. Add 10.0 mL deionized-distilled water to each vial containing a sorbent section and cap. 8. 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. (If samples are allowed to stand for a period of time filtration m ay not be ne ces sary.)
CALIBRATION AND QUALITY CONTRO L: 9. Calibrate daily with at least six working standards over the range 1 to 250 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. Pip et 0.5-, 1.0 0-, 1.5 0-, 2.0 0-, and 2.50 -m L of the workin g stan dard solution into 25-m L volum etric flasks to produce 0.5-, 1.00-, 1.50-, 2.00-, and 2.50-µg CN - standards c. Analyze together with field sam ples and blank s (steps 12 throug h 14). d. Prepare calibration graph (peak height in nA vs. µg CN -). 10. 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. Rem ove and disca rd back sorbent sec tion of a blank sam pler. b. Inject a known amount of calibration stock solution directly onto the soda lime with a microliter syringe. c. Ca p an d allow to stand o vern ight. d. Desorb (steps 5 through 8) and analyze together with working standards and blanks (steps 12 through 14). e. Prepare a graph of DE vs. µg CN - recovered. 11. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and D E graph are in control.
MEASUREMENT: 12. Set ion chromatograph according to manufacturer’s instructions to conditions given on page 6017-1. 13. Injec t 50-µ L sa m ple aliqu ot. Fo r m anu al ope ration, inject 2 to 3 m L of s am ple fro m filter/syringe to ensure complete rinse of sample loop. NOTE: All samples, eluents, and water flowing through the IC must be filtered to avoid plugging system valves or columns. 14. Me asu re pe ak heigh t. NOTE: If sam ple peak height ex ceeds linear calibration ran ge, dilute w ith eluent, reanalyze a nd apply the appropriate dilution factor in calculations.
CALCULATIONS: 15. Calculate the mass, µg, of CN - in an a liquot analyzed . App ly the app ropriate aliquot fac tor to calculate the mass, µg, of CN - in the original 10-mL solution. 16. Determine the mass, µg CN- (corrected for DE ), found in the sam ple front (W f) and back (W b) sorbent sections and in the averag e m edia blank front (B f) and back (B b) sorbent sections. If W b > W f/10, report breakthrough and possible sample loss. 17. Calculate conce ntration, C, of HCN in the air volume sam pled V(L).
where 1.039 = conversion factor, CN ! to HCN NOTE: :g/L / m g/m 3
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
