Page:NIOSH Manual of Analytical Methods - 2017.pdf/3

 ANILINE, o-TOLUIDINE, AND NITROBENZENE: METHOD 2017, Issue 1, dated 15 January 1998 - Page 3 of 5

CALIBRATION AND QUALITY CONTROL: 9.	Calibrate daily with at least six working standards over the range of interest. a.	 Add known amounts of calibration stock solutions to ethanol in 10-mL volumetric flasks and dilute to the mark. b.	 Analyze together with samples and blanks (steps 12 and 13). c.	 Prepare calibration graph (peak area vs. µg analyte). 10.	Determine recovery (R) at least once for each lot of glass fiber filters and desorption efficiency (DE) for each lot of silica gel sorbent tubes used for sampling in the calibration range (step 9). a.	 Prepare three samplers at each of six levels plus three media blanks. b.	 Inject a known amount of calibration stock solutions directly onto the sulfuric acid-treated, 37-mm glass fiber filters and onto the front sorbent bed of each silica gel tube. c.	 Allow the filters and tubes to air equilibrate for several minutes, then cap the ends of the tubes and cassettes and allow to stand overnight. d.	 Desorb (steps 5 through 8) and analyze together with standards and blanks (steps 12 and 13). e.	 Prepare a graphs of R and DE vs. µg analyte recovered. 11.	Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration, R, and DE graphs are in control. MEASUREMENT: 12.	Set gas chromatograph according to manufacturer’s recommendations and to conditions given on page 2017-1. Inject a 1-µL sample aliquot manually using solvent flush technique, or with an autosampler. NOTE:	If peak area is above the linear range of the working standards, dilute with ethanol, reanalyze, and apply the appropriate dilution factor in the calculations. 13.	Measure peak areas. CALCULATIONS: 14.	Determine the mass, µg (corrected for R), for each analyte found on the glass fiber filter ( glass fiber filter blank . 15.	Calculate concentration,, for each analyte in the air volume sampled, (L):

) and

, mg/m³. NOTE:	Use this equation to calculate wipe samples and dermal badges, if collected. 16.	Determine the mass, µg (corrected for DE), for each analyte found in the sample front and back silica gel sections, and in the average media blank front and back  sorbent sections. NOTE:	If >  /10, report breakthrough and possible sample loss. 17.	Calculate concentration,, of each analyte in the air volume sampled, (L): , mg/m³. NOTE:	µg/L = mg/m³. EVALUATION OF METHOD: The method was developed in response to a health hazard evaluation (HHE) request at a rubber tire manufacturing plant where there was a reported high incidence of bladder cancer [5,6]. The method was evaluated for the collection of aniline, o-toluidine, and nitrobenzene on gauze wipes, passive dermal samplers, and 37-mm glass fiber filter/silica gel sorbent tube sampling train. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition