Page:NIOSH Manual of Analytical Methods - 1606.pdf/3

 ACETONITRILE: METHOD 1606, Issue 3, dated 15 January 1998 - Page 3 of 3 in the calibration range (step 9). Prepare three tubes at each of five levels plus three media blanks. a. Remove the back sorbent section of the sampler. b. Inject a known amount of calibration stock solution directly onto the front sorbent section of each charcoal tube. c. Allow the tubes to air equilibrate for several minutes, then cap the ends of the tubes and allow to stand overnight. d. Desorb (steps 5 through 8) and analyze together with standards and blanks (steps 11 and 12). e. Prepare a graph of DE vs. µg acetonitrile recovered. MEASUREMENT: 11. Set gas chromatograph according to manufacturer’s recommendations and to conditions given on page 1606-1. Inject a 1-µL sample aliquot manually using the solvent flush technique or with an autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with methylene chloride/methanol (85:15), reanalyze and apply the appropriate dilution factor in the calculations. 12. Measure peak areas. CALCULATIONS: 13. Determine the mass, µg (corrected for DE), for acetonitrile found in the sample front (W f) and back (Wb) sorbent sections, and in the average media blank front (B f) and back (Bb) sorbent sections. NOTE: If Wb > Wf/10, report breakthrough and possible sample loss. 14. Calculate concentration, C, of acetonitrile in the air volume sampled, V (L):

C

NOTE: µg/L

Wf

Wb

Bf V

Bb

, mg/m 3

mg/m3

EVALUATION OF METHOD: This method development was based upon NMAM user requests to update and improve problematic gas chromatography methods. After determining that a methylene chloride/methanol (85:15) solution was the best desorption solvent (improved DE recovery and less hazardous than benzene), the desorption efficiency was determined for acetonitrile at 5 levels ranging from 39 µg to 275 µg. The average DE for acetonitrile was determined to be 1.019. The LOD was determined to be 0.8µg per sample. The precision, as determined from the pooled relative standard deviation (S r), was determined to be 0.015 [1]. Acetonitrile storage stability at 0.25 x REL and 5 C, was acceptable after 30 days with an average recovery of 98.5%. REFERENCES: [1] [2] [3] [4]

Pendergrass SM [1997]. Acetonitrile Backup Data Report, unpublished data, NIOSH/DPSE. NIOSH [1977]. Documentation of the NIOSH Validation Tests, S165, U.S. Department of Health, Education, and Welfare (NIOSH) Publ. No. 77-185. NIOSH [1981]. Health Hazard Evaluation Report, HHE 81-359-1058. NIOSH [1977]. Acetonitrile: Method S165. In: Taylor, DG, ed. NIOSH Manual of Analytical Methods, 2nd ed., V. 3, U.S. Department of Health, Education, and Welfare (NIOSH) Publication No. 77-157C.

METHOD WRITTEN BY:

Stephanie M. Pendergrass, NIOSH/DPSE

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition