n-BUTYLAMINE: METHOD 2012, Issue 1, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 10. 11. 12.
13.
Prepare working standards (12 to 1000 µg/mL aqueous methanol) by adding appropriate aliquots of calibration stock solution to 50% methanol. Follow neutralization procedure in step 9. Analyze working standards together with samples and blanks (steps 14 through 16). Prepare a calibration graph of area vs. µg of n-butylamine. Determine recovery for each lot of silica gel used for sampling in the concentration range of interest. Prepare four silica gel tubes at each of five levels plus three media blanks. a. Remove and discard 75 mg back sorbent section of an unused sorbent tube. b. Spike aliquot of calibration solution onto front section sorbent section of silica gel tube with a microliter syringe. c. Cap and let stand overnight. d. Desorb following (steps 7 through 9) and analyze along with working standards and blanks (steps 14 through 16). e. Prepare graph of recovery vs. µg n-butylamine. Analyze three quality control spikes and three analyst spikes to ensure that calibration graph and recovery graph are in control.
MEASUREMENT: 14. 15.
16.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2012-1. Inject 5-µL sample aliquot. NOTE: If peak area is above the linear range of the working standards, dilute with 50% methanol, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 17.
18.
Determine mass, µg (corrected for recovery), of n-butylamine found in the sample front (W f) and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample less. Calculate concentration of n-butylamine in the air volume sampled, V (L):
EVALUATION OF METHOD: This method was evaluated over the range 8.09 to 35.5 mg/m 3 at 24 °C and pressure of 769 mm Hg using 15-L samples [1,3]. Sampling and measurement precision, Sr, was 0.049, with average recovery of 91.4%, representing a non-significant bias. Sample stability during storage was evaluated at 270 µg n-butylamine per sample. Samples showed 98.4% recovery after one day of storage at ambient conditions compared to 95.2% recovery for seven-day old samples.
REFERENCES: [1] [2]
Backup Data Report for n-butylamine, prepared under NIOSH Contract 210-76-0123 (1978). NIOSH/DPSE Analytical Sequence #4975, Measurement Research Support Branch, NIOSH, Cincinnati, Ohio (unpublished, 1986). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
