Page:NIOSH Manual of Analytical Methods - 5518.pdf/3

 NAPHTHYLAMINES, α- and β-: METHOD 5518, Issue 2, dated 15 August 1994 - Page 3 of 4 10.

11.

Determine desorption efficiency (DE) at least once for each lot of filters and sorbent used for sampling in the range of interest. Prepare three samplers at each of five levels plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject separate known amounts (2 to 20 µL) of calibration stock solution, or a serial dilution thereof, directly onto filter and front sorbent section with a microliter syringe. c. Cap the sampler. Allow to stand overnight. d. Desorb (steps 6 through 8) and analyze with working standards (steps 12 and 13). e. Prepare graphs for filter and sorbent (DE vs. µg analytes recovered). Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graphs and DE graphs are in control.

MEASUREMENT: 12.

13.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 5518-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE 1: For the conditions given, t r = 6 min for α-naphthylamine and 7 min for β-naphthylamine. NOTE 2: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid with eluent, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.

CALCULATIONS: 14.

15.

Determine the mass, µg (corrected for DE) of analyte found on the sample filter (W f) and sample sorbent (W s) and on the media blank filter (B f) and media blank silica gel (B s) from the calibration graph. Calculate concentration, C, of analyte in the air volume sampled, V (L):

EVALUATION OF METHOD: P&CAM 264 was issued on August 1, 1978 [2], and evaluated with generated atmospheres containing mixtures of the two analytes produced by controlled vapor diffusion [1]. Capacity of the 100-mg front sorbent section at breakthrough (effluent = 5% of test concentration) was approximately 5 µg of α-naphthylamine and 7.5 µg β-naphthylamine at 80% RH with a sampling range of 0.8 L/min in atmospheres containing approximately 80 µg/m 3 of the analytes. Breakthrough capacity was found to be strongly influenced by relative humidity, being reduced by 50% at 95% RH compared to the values found at 80% RH. In storage tests, quantitative recovery was obtained for 0.5-µg masses of α-naphthylamine on silica gel and filters if stored at -15 °C for up to seven days; recovery for samples stored 14 or 21 days at -15 °C was 81 to 82% for filters and 94% for silica gel. For β-napthylamine under the same conditions, similar recoveries were observed, except that recovery from filters was quantitative at -15 °C when stored 14 or 21 days. Recovery after storage at room temperature (23 °C) for 8 days was in the range 24 to 73%.

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