Page:NIOSH Manual of Analytical Methods - 5701.pdf/3

 RESORCINOL: METHOD 5701, Issue 1, dated 15 January 1998 - Page 3 of 4 to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (peak area or height vs. µg resorcinol). 9. Determine desorption efficiency (DE) at least once for each lot of OVS tubes used for sampling in the calibration range (step 8). a. Prepare three samplers at each of six levels plus three media blanks. b. Raise the Teflon holding ring to prevent wicking, and inject a known amount of calibration stock solution directly onto the front sorbent bed of each OVS tube. c. Allow the tubes to air equilibrate for several minutes, then cap the ends of the tubes and allow to stand overnight. d. Desorb the samples (steps 5 through7) and analyze together with standards and blanks (steps 11 and 12). e. Prepare a graph of DE vs. µg analyte recovered. 10. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration and DE graphs are in control.

MEASUREMENT: 11. Set gas chromatograph according to manufacturer’s recommendations and to conditions given on page 5701-1. Inject a 1-µL sample aliquot manually using solvent flush technique or with an autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with methanol, reanalyze and apply the appropriate dilution factor in the calculations. 12. Measure peak areas.

CALCULATIONS: 13. Determine the mass, µg (corrected for DE), for resorcinol found in the sample front (W f) and back (Wb) sorbent sections, and in the average media blank front (B f) and back (Bb)sorbent sections. NOTE: If Wb > Wf/10, report breakthrough and possible sample loss. 14. Calculate concentration, C, of resorcinol in the air volume sampled, V (L):

C

NOTE: µg/mL

Wf

Wb

Bf V

Bb

, mg/m 3

mg/m3

EVALUATION OF METHOD: This work extended the range of the OSHA stopgap method for recorcinol [2] to lower concentration levels. The method was evaluated for resorcinol over the range of 0.040 to 5.96 mg per sample. Table 1 shows the desorption efficiencies for each of the sampler components, glass fiber filter (alone) and XAD-7 sorbent, as well as the complete OVS tube. The 40 µg, 80 µg, 120 µg, and 200 µg levels were evaluated by NIOSH [1]. Higher concentration levels (298 to 5860 µg) were evaluated by OSHA [2]. The OSHA study tested retention efficiency by spiking filters with 5.96 mg resorcinol and pulling humidified air through the tubes. The mean recovery from these samples was 99.7%, with no resorcinol found on the back up section. When stored at ambient temperature, resorcinol samples spiked at 120 µg were stable on the XAD-7 sorbent for 28 days, NIOSH Manual of Analytical Methods (NMAM), Fourth Edition