VINYLIDENE CHLORIDE: METHOD 1015, Issue 2, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 8.
9.
10.
Calibrate daily with at least six working standards. a. Add known amounts of calibration stock solution to CS 2 in 10-mL volumetric flasks and dilute to the mark. Prepare working standards in the range 10 to 100 µg vinylidene chloride/mL. b. Analyze with samples and blanks (steps 11 and 12). c. Prepare calibration graph (peak area or peak height vs. µg vinylidene chloride). Determine desorption efficiency (DE) at least once for each batch of charcoal used for sampling in the range of interest. 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 (2 to 10 µL) of DE stock solution directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg vinylidene chloride recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.
MEASUREMENT: 11.
12.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 1015-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If response is above the linear range of the working standards, dilute with CS 2, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area or peak height.
CALCULATIONS: 13.
14.
Determine the mass, µg (corrected for DE) of vinylidene chloride 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 loss. Calculate concentration, C, of vinylidene chloride in the air volume sampled, V (L):
EVALUATION OF METHOD: Method P&CAM 266 was issued on November 21, 1977 [1]. The method was tested with sample loadings between 13 and 85 µg vinylidene chloride per charcoal tube [2]. The samples were collected from atmospheres containing vinylidene chloride in the range 7.6 to 10.0 mg/m 3 and having relative humidity in the range 10 to 95%. The pooled relative standard deviation of the measurement was 4.8% for the analysis of 36 samples over the range 12 to 85 µg vinylidene chloride per sample. Desorption efficiency was determined to be 80% for a loading of 7 µg vinylidene chloride at a vinylidene chloride concentration of 10 mg/m 3 and high relative humidity; the breakthrough volume was 7.3 L when sampling at 0.2 L/min from this atmosphere. At 87% relative humidity, the breakthrough volume was 10% of the breakthrough volume at 10% relative humidity.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
