Development of an Automated, Pyridine Free Method for Aerosol Cyanide Compounds and Hydrogen Cyanide. An Alternative to NIOSH LeRoy Dobson, Chemist at Wisconsin Occupational Health Laboratory, Derek Popp, Quality Control Officer At Wisconsin Occupational Health Laboratory Lyle Reichmann, CIH, Inorganic Supervisor at Wisconsin Occupational Health Laboratory

Narrative Samples are collected on soda lime tubes. Plugs are extracted in 10 ml of 0.1 N NaOH, and the front and back sections of soda lime are extracted separately with 10 ml of DI water. Samples are shaken and allowed to stand for 1 hour. Samples are then run by ion chromatography using a DIONEX AS7 column, AG7 guard column, and electrochemical detector. Flow is 1 milliliter per minute of mobile phase (0.5 M sodium acetate, 0.1 M sodium hydroxide, and 0.5 % ethylene diamine). The detector settings are silver working electrode vs. silver chloride reference with 0.00 applied voltage.

Advantages 1.Easily automated with software and autosampler. 2.Eliminates impingers (NIOSH 7904). 3.Eliminates problems with ion specific Electrodes (interferences from sulfides). 4.Eliminates possible exposure to pyridine (NIOSH 6010). 5.Eliminates very labor intensive procedure (NIOSH 6010). 6.Eliminates possible generation of HCN gas (NIOSH 6010).

Disadvantages 1.Recovery below 10 ug per sample is questionable. 2.Requires electrochemical detection, which can be high maintenance. 3.Working electrode and reference electrodes get dirty causing noise and decreased response. 4.Reference electrode may need to be replaced frequently. 5.Electrochemical detectors can be somewhat costly. The recovery of cyanide from the soda lime tubes declines below 10 ug applied.

Equipment Used 1.Soda lime tubes from SUPELCO (cat #226-28). 2. DIONEX GP-50 gradient pump. 3.DIONEX ED-40 electrochemical detector and cell using silver working electrode, silver chloride reference, and 0.00 V applied. 4.DIONEX AS7 anion separator column. 5.DIONEX AG7 anion separator guard column. 6.DIONEX LC20 chromatography enclosure with air actuated rotary injection valve and 50 uL injection loop. 7. DIONEX AS40 autosampler with 0.5 ml vials and cassettes. 8.DIONEX PEAKNET software version 5.1.

Possible Interferences 1.Sulfide in high concentrations (poisons electrodes). 2.Any component with the same retention time as cyanide.

Protocol 1.Only a new analytical method was used. Collection was not investigated (NIOSH 6010). 2.Desorptions were investigated. 3.Quantifiable limit was investigated. 4.Linear range was investigated. Results of QC samples showing good recoveries from ug applied

Conclusions The analytical procedure for NIOSH method 6010 was successfully modified to use Ion Chromatography (IC) instead of UV-Visible spectrometry. The IC method improves on NIOSH 6010 by eliminating the use of pyridine and the potential loss of cyanide in the titration step. Sample preparation is reduced to desorption in water. The ease of sample preparation and the potential to automate the analysis are listed as advantages. The laboratory has been running this method frequently since 1997 with laboratory control samples to demonstrate method performance. Good recoveries have been consistently obtained demonstrating that the method is rugged. Cyanide solutions spiked onto the media have shown excellent stability past 200 days.

Results of QC samples using the UV procedure. The data shows that the method is also capable of producing good results

Quality control card with the performance limits calculated by the software. The data shows an average recovery of 97%.

Results of QC samples since the beginning of IC method analysis. The majority of the data points are within 20%.

Results of QC samples by elapsed time showing good stability of cyanide on the soda lime tubes.

Disclaimers & Acknowledgements The mention of company names or products does not constitute endorsement by Wisconsin Occupational Health Laboratory, the Wisconsin State Laboratory of Hygiene, or the University of Wisconsin.