Page:NIOSH Manual of Analytical Methods - 2007.pdf/3

 AMINOETHANOL COMPOUNDS I: METHOD 2007, Issue 2, dated 15 August 1994 - Page 3 of 5 6. 7.

8. 9.

10.

Place the first glass wool plug and the front section of the sampler in a vial. Place the second plug and backup section in a separate vial. Add 2.0 mL eluent to each vial. Attach cap to each vial. NOTE: If conc. HCl was not added to the silica gel after sampling, desorb the samples in 2.0 mL 0.12 N HCl in eluent. The acid increases desorption efficiency. Allow to stand 2 h with occasional agitation. Transfer a 0.5-mL aliquot of each sample to another vial. Add 0.5 mL alkalinizing solution and attach cap. Mix thoroughly. Check the solution pH with pH paper. If the solution pH is <9 add alkalinizing solution until solution pH is >9. If 2-aminoethanol is present, repeat step 9 with another 0.5-mL aliquot. Add 10 µL benzaldehyde to the basic solution, mix thoroughly and let stand 20 min. NOTE: Benzaldehyde derivatizes 2-aminoethanol to 2-benzylideneaminoethanol which has a higher molecular weight, thereby decreasing the GC detection limit. Underivatized 2-aminoethanol can be determined by this method if the sample size is large.

CALIBRATION AND QUALITY CONTROL: 11.

12.

13.

Calibrate daily with at least six working standards over the range 0.005 to 6 mg of each analyte. a. Add known amounts of analyte or calibration stock solution to 0.12 N HCl in eluent in 10-mL volumetric flasks and dilute to the mark. b. Treat the working standards with base and benzaldehyde as needed (steps 9 and 10). c. Analyze together with samples and blanks (steps 14 and 15). d. Prepare calibration graph (peak area vs. mg analyte). Determine desorption efficiency (DE) at least once for each lot of silica gel used for sampling. 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 analyte or calibration stock solution directly onto front sorbent section with a microliter syringe. c. Add 20.0 µL conc. HCl. d. Cap the tube. Allow to stand overnight. e. Desorb (steps 6 through 10) and analyze with working standards (steps 14 and 15). 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 and DE graph are in control.

MEASUREMENT: 14.

15.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2007-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE 1: The temperature program separates all three compounds. Isothermal column conditions are 225, 150, and 90 °C for 2-aminoethanol, 2-dibutylaminoethanol and 2-diethylaminoethanol, respectively. The column packing degrades rapidly at 225 °C; keep operating time at a minimum near this temperature. NOTE 2: If peak area is above the linear range of the working standards, dilute with eluent, reanalyze, and apply the appropriate dilution factor in calculations. NOTE 3: When using a capillary column system, use the split injection port liner coated with KOH to improve amine peak shape. Measure peak area.

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