Page:NIOSH Manual of Analytical Methods - 2010.pdf/3

 AMINES, ALIPHATIC: METHOD 2010, Issue 2, dated 15 August 1994 - Page 3 of 4 a.

10.

11.

Add aliquots of the calibration stock solutions to 10-mL volumetric flasks and dilute to the mark with 0.1 M sulfuric acid in aqueous methanol. b. Neutralize the standards as in step 8. c. Analyze with samples and blanks (steps 12 through 14). d. Prepare a calibration graph (peak area or peak height vs. mg of amine per sample). Determine desorption (DE) at least once for each lot of silica gel used for sampling in the concentration range of interest. Prepare four tubes at each of five levels plus media blanks. a. Measure the amount of silica gel used in the front sorbent section into a vial. b. Inject a known amount (1 to 20 µL) of calibration stock solution, or a dilution there of directly onto the silica gel. c. Cap vial. Allow to stand overnight. d. Desorb and neutralize as in steps 6 through 8. e. Analyze together with working standards and blanks (steps 12 through 14). f. Prepare a graph of DE vs. mg analyte recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.

MEASUREMENT: 12.

13. 14.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2010-1. Use the following conditions as a guide.

Compound

Injection

Diethylamine Dimethylamine

160 155

Temperature (°C) Column Detector 70 60

200 200

NOTE: Use a removable glass liner at the inlet to the GC column. Remove the glass liner from the gas chromatograph and clean it with water and acetone rinses at the end of each day. In order to prevent salt buildup, the glass GC liner was soaked in a saturated KOH solution and packed with KOH-coated glass wool [9]. Inject sample aliquot manually using solvent flush technique or with autosampler. Measure peak area or peak height.

CALCULATIONS: 15.

16.

Determine the mass, mg (corrected for DE), of analytes found in sample front (W f) and back (Wb) sorbent sections and in the media blank front (B f) and blank back (B b) sorbent sections from the calibration graph. Calculate concentration of analyte, C (mg/m 3), in the air volume sampled, V (L):

EVALUATION OF METHOD: Precisions, biases, and recoveries listed below were determined by analyzing generated atmospheres containing one-half, one, and two times the OSHA standard [1,2,3]. Generated concentrations were independently verified. Breakthrough of the front section of the silica gel tube was not observed after sampling a dry test atmosphere. Sample stability was not determined.

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