Page:NIOSH Manual of Analytical Methods - 5031.pdf/3

 ASPARTAME: METHOD 5031, Issue 2, dated 15 August 1994 - Page 3 of 4 c. 9.

10.

Prepare a calibration graph (peak area vs. mass of Aspartame, µg per sample). Determine the recovery at least once for each lot of filters used for sampling in the range of interest. Prepare six filters at each of three levels plus three media blanks. a. Add known amounts of Aspartame in methanol to the filters. b. Cover filters. Allow to stand overnight for solvent evaporation. c. Prepare samples (step 5 through 7), and analyze (step 11 through 13) together with standards. d. Determine recovery (R). Construct a graph of R vs. µg Aspartame recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and recovery graph are in control.

MEASUREMENT: 11. 12. 13.

Set the liquid chromatograph to manufacturer's recommendations and parameters given on page 5031-1. Inject sample aliquot manually or with autosampler. Measure peak areas.

CALCULATIONS: 14. 15.

Determine the mass, µg (corrected for recovery) of Aspartame found on the sample filter (W) and the average blank filter (B). Calculate concentration, C, of Aspartame in the air volume sampled, V (L):

EVALUATION OF METHOD: A calibration curve constructed from nine standards over the range 0.5 to 463 µg/mL Aspartame in solution was linear and indicated a limit of detection (LOD) of 2 µg per filter and a limit of quantitation (LOQ) of 7 µg per filter. Test samples were prepared by spiking filters with known amounts of Aspartame from a solution in methanol at levels between 4.4 µg per filter and 434 µg per filter. At each level, three filters were subjected to each of the following studies (Table 1): a. To evaluate extraction efficiency, the filters were analyzed immediately. b. To assess storage stability, spiked filters were stored for 1 month prior to analysis. c. To investigate the stability of the material on the filter during sampling, spiked filters were attached to a sampling pump and 1000 L of laboratory air was drawn through them at 2.5 L/min before analysis.

TABLE 1: Average Percent Recovery (n=3) of Aspartame Spiked Amount (µg) (n=3) 4.4 43.5 217 435

Extraction Efficiency (%RSD)

Sampling Stability (%RSD)

Storage Stability @ 30 days (%RSD)

100 103 101 101

100 (1.3) 98 (3.1) 100 (2.4) 101 (1.3)

102 (2.7) -

(2.3) (4.8) (1.8) (1.3)

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