Page:NIOSH Manual of Analytical Methods - 2014.pdf/3

 p-Chlorophenol: METHOD 2014, Issue 2, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 10.

11.

12.

Calibrate daily with at least six working standards in the range 2.5 to 64 µg per sample. a. Dilute aliquots of p-chlorophenol stock solution with 30% (v/v) acetonitrile in water in volumetric flasks to encompass the range of interest. Prepare fresh daily. b. Analyze working standards with samples and blanks steps. c. Prepare calibration graph (peak area or peak height vs. µg of p-chlorophenol per sample. Determine desorption efficiency (DE) for each lot of silica gel used for sampling in the calibration range. Prepare three tubes at each of five levels. a. Remove backup section. Inject known amounts of DE stock solution (2 to 10 µL) onto the silica gel with a microliter syringe. b. Cap the tubes and allow to stand overnight. c. Desorb (steps 7 through 9) and analyze together with standards and blanks (steps 13 and 14). d. Prepare a graph DE vs. µg p-chlorophenol recovered. Analyze three quality control spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 13.

14.

Set HPLC according to manufacturer's recommendations and to conditions on page 2014-1. Inject sample aliquot manually or with autosampler. NOTE: If peak is above the linear range of the working standards, dilute with 30% (v/v) acetonitrile in water, reanalyze, and apply the appropriate dilution factor. Measure peak area or peak height.

CALCULATIONS: 15. 16.

Determine the mass, µg (corrected for DE), of analyte found on 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. Calculate concentration of p-chlorophenol in the air volume sampled, V (L):

EVALUATION OF METHOD: The overall method was evaluated by collecting 3-L samples of test atmospheres containing p-chlorophenol in the range of 0.91 - 23.4 mg/m 3 at 29 °C and a relative humidity of greater than 80%. The amounts collected ranged from 2.6 - 64 µg per 150-mg bed of silica gel. The breakthrough volume of the sorbent tube was found to be approximately 60 L with a sampling rate of 0.2 L/min at a p-chlorophenol concentration of about 70 mg/m 3, a sampling temperature of 43 °C, and a relative humidity of greater than 80%. Samples of p-chlorophenol on silica gel were found to be stable at 25 °C for 7 days and for 29 days if stored at 0 °C after the seventh day. Silica gel gave an average desorption efficiency of 96% with a Sr 2.4% for loadings of 2.54 - 48.0 µg of p-chlorophenol on 150-mg beds of sorbent material.

REFERENCES: [1] Dillon, H.K., Emory, M.B. Development of Air Sampling and Analytical Methods for Toxic Chlorinated Organic Compounds: Research Report for p-Chlorophenol. NIOSH Contract 210-780012, Southern Research Institute, Birmingham, Alabama (1980). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94