Page:NIOSH Manual of Analytical Methods - 5029.pdf/4

 4,4'-METHYLENEDIANILINE: METHOD 5029, Issue 2, dated 15 August 1994 - Page 4 of 5 b. c.

To assess storage stability, spiked filters were stored in glass scintillation vials for 1 month prior to analysis. To investigate the stability of MDA on the filter during sampling, spiked filters were attached to a sampling pump and 1000 L of laboratory air was drawn through them at 2.5 L/min before analysis.

Table 1: Average Percent Recovery (n=3) of 4,4'-Methylenedianiline From Filter Media Spiked Amount (µg)

Extraction Efficiency (S.D.) (%)

3.71 1.80 0.93 0.37 0.09 0.037 a

94.5 91.3 85.9 84.8 82.0 80.0

(0.8) (0.2) (0.8) (0.9) (2.7) (4.1)

Storage Stability a (%)

Sampling Stability (%)

94.4 91.1 86.4 86.0 82.0 83.0

94.4 90.8 85.5 84.9 77.0 77.0

(1.0) (0.4) (0.9) (0.7) (3.8) (4.1)

(1.0) (1.7) (0.4) (1.0) (3.5) (3.1)

- Stored in glass scintillation vial for 1 month.

Nine spiked filters were prepared independently and submitted for analysis as a single blind test. Recoveries were 80 to 95% when spiked with 0.012 to 1.2 µg per filter. During method ruggedization, recoveries were observed to drop significantly during shipment in cassettes. The reason has not been determined but stability has been achieved by field extraction of the filter with methanolic KOH. Solutions and extracted filters were prepared, shipped, stored for 60 days, and analyzed. The data are shown in Table 2. Table 2: Stability of Extracted Filter Solutions Spiked Amount (µg) 9.9 5.1 1.0 0.0

N

% Recovery (S.D.)

4 4 4 2

92.1 (0.017) 90.4 (0.042) 100.0 (0.050) NA

WIPE SAMPLING-This analytical method was used to analyze environmental samples collected on gauze pads and smear tabs. MDA was spiked onto acid-treated gauze pads, plain gauze pads, and smear tabs at 92, 9.2, and 0.92 µg per sample. Sets of each concentration were extracted immediately after allowing the spiking solution to evaporate, one day, one week, and one month after spiking. The extraction solution consisted of 10 mL 0.1 N methanolic KOH for the gauze pads and 2 mL for the smear tabs. The best recovery was obtained when the media were extracted immediately after the methanol evaporated. The same-day samples were reanalyzed at various times to determine if MDA would react with the medium when in solution. Recoveries are given in Table 3.

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