Page:NIOSH Manual of Analytical Methods - 2503.pdf/3

 MEVINPHOS (PHOSDRIN): METHOD 2503, Issue 2, dated 15 August 1993 - Page 3 of 4 9.

10.

Determine desorption efficiency (DE) at least once for each batch of Chromosorb 102 used for sampling in the calibration range (step 8). Prepare three tubes at each of five levels plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount of calibration stock solution directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg Mevinphos recovered. Analyze three quality control blind spikes and three analyst spikes to insure that the calibration graph and DE graph are in control.

MEASUREMENT: 11.

12.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2503-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with toluene, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.

CALCULATIONS: 13.

14.

Determine the mass, µg (corrected for DE) of Mevinphos found in the sample front (W f) and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of Mevinphos in the air volume sampled, V (L):

EVALUATION OF METHOD: Method S296 [3] was issued on July 6, 1979, and validated over the range 0.027 to 0.145 mg/m 3 at 25 °C using a 240-L sample [2,4]. Overall precision, s r was 0.0694 with an average recovery of 103.9%, representing a non-significant bias. The concentration of Mevinphos was independently verified by sampling the generator with toluene-filled bubblers and measurement by GC/FPD. Desorption efficiency was 1.04 in the range 7.0 µg to 40.0 µg per sample. After sampling an atmosphere containing 0.195 mg/m 3 at 1.0 L/min at 80% RH for 376 min, only 0.6% breakthrough was reported [2]. REFERENCES: [1]

[2] [3]

Criteria for a Recommended Standard...Occupational Exposure During the Manufacture and Formulation of Pesticides, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-174 (1978). Backup Data Report No. S296, Phosdrin, prepared under NIOSH Contract No. 210-76-0123 (July, 1979), available as Order No. PB 81-228983 from NTIS, Springfield, VA 22161. NIOSH Manual of Analytical Methods, 2nd ed., V. 6, S296, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-125 (1980).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93