Page:NIOSH Manual of Analytical Methods - 3509.pdf/3

AMINOETHANOL COMPOUNDS II: METHOD 3509, Issue 2, dated 15 August 1994 - Page 3 of 5 MEASUREMENT: 8.

9. 10. 11.

Set the ion chromatograph to manufacturer's recommendations and to conditions given on page 3509-1. When using fiber or micromembrane suppression, if the background level is high, make several injections of acetonitrile through the sample loop to lower the background level. NOTE: Filter all samples, eluents, and water flowing through the ion chromatograph to avoid plugging system valves or columns. Transfer a portion of sample solution to a syringe fitted with an inline membrane filter, for direct injection or for transfer to autosampler vials. Inject 50-µL sample aliquot. For manual operation, inject 2 to 3 mL of sample from syringe (through inline filter) to ensure complete rinse of the sample loop. Measure peak height. If sample peak height exceeds the linear calibration range, dilute with eluent, reanalyze, and apply the appropriate dilution factor in calculations.

CALCULATIONS: 12. 13.

Determine the mass, µg, of analyte in the impinger (W) and in the average media blank (B) from the calibration graph. Calculate the concentration, C, of analyte in the air volume sampled, V (L):

EVALUATION OF METHOD: This method was evaluated for DEA with generated air samples and for all three specified amines with liquid spiked samples [5]. Samples for DEA were generated from methanol solution delivered by a syringe pump to an ultrasonic nebulizer producing a mist which was mixed with dry, heated air in the initial mixing chamber to evaporate the methanol. The flow passed into a sampling manifold where it was mixed with humidified air to maintain a relative humidity of 73-78%. The system was monitored by measuring the level of methanol in the sampling manifold with a Miran 1A infrared analyzer. The recovery of DEA calculated from the methanol concentration varied from 70-95% in different generation runs. After studies were complete, the initial mixing chamber was rinsed with 2 m M HSA and was found to contain 52 mg DEA, and a rinse of the sampling chamber contained 23 mg DEA, indicating that DEA was lost in the generator during sample generation, and explaining the variation in recovery vs. that calculated from the methanol concentration. In the first run, four samples were generated to test the generation system. These samples were expected to contain 1305 µg DEA based on monitoring of the methanol concentration. They were found to have 1237 ± 56 µg DEA, giving a recovery of 94.8%. Next, twelve samples at each of two levels were generated for storage studies. All samples were collected at 0.75 L/min and stored at room temperature (20 °C). Finally, six samples including backup impingers were generated for breakthrough studies. The results of the storage and breakthrough studies are given below: Storage studies: N Low level High level

5 6

2-Day Storage Found, µg RSD 226 885

4.9 3.3

Breakthrough studies (stored 39 days at 20 °C): N Found, µg RSD Front section 6 4433 7.2 Back section 6 137 N/A Total 6 4570 8.2

N 5 4

21-Day Storage Found, µg RSD 215 865

13.4 3.0

Breakthrough (average) 2.68% (range 1.0-5.4%)

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

Recovery after 21 days 95.1% 97.7%