Page:NIOSH Manual of Analytical Methods - 2016.pdf/3

 FO RM ALD EHY DE: M ETH OD 2016, Issue 2, dated 1 5 Ma rch 2003 - Page 3 of 7 SAMPLE PREPARATION: NOTE: Check acetonitrile for form aldehyde content by elution and analysis of a blank cartridge; the formaldehyde level sh ould be below the detec tion lim it. Since background levels of formaldehyde on the samplers may change during storage, compare samples with sampler blanks from the same lot. Samples and blanks should be stored under the same conditions. 7. Elute the formaldehyde derivative from the cartridge samplers with 10-mL quantities of acetonitrile. a. Collect effluent from each sampler in a 10-mL volumetric flask. b. Add ac eton itrile to the m ark for ea ch s am pler. NOTE: The silica gel bed of the sampler will retain approximately 0.5 mL of the original 10 mL.

CALIBRATION AND QUALITY CONTRO L: 8. Ca librate daily with at leas t six m edia working standard s over the rang e of interes t. a. Prepare a series of aqueou s form aldehyde solutions for the fortification of samplers. Suggested concentrations include 1, 4, and 20 µg/mL. See APPEND IX A for standardization of formaldehyde in water. b. Co nne ct the outlet of a ca rtridge sam pler to a personal sam pling pum p with flexible tubing. Turn on the pum p and m ake s ure there is a flow of air through the sa m pler. c. Load a 100-µL syringe with a selected volume of aqueous formaldehyde solution in the range of 30 to 90 µL. Suggested quantities of formaldehyde for spiking include 0.04, 0.10, 0.20, 0.30, 0.40, 0.80, 1.0 and 2.0 µg/sample. d. Place the tip of the syringe needle against the frit in the inlet of the sampler and eject the formaldehyde solution. e. Prepare the m edia working stand ard (steps 7.a and 7.b). f. Prepare a dditional working standards (steps 8.b. through 8.e.). g. Trans fer 3-m L aliquots of working standa rds to 4-m L vials, and analyze (steps 10, 12 an d 13). h. Prepare calibration graph, peak area or height vs. µg formaldehyde per sample. 9. Fortify and analyze three quality control spikes and three analyst spikes to ensure that calibration graph is in control.

MEASUREMENT: 10. Set liquid ch rom atog raph acc ording to manufacturer’s recomm endations and to conditions given on page 2016-1. 11. Transfer a 3 -m L aliquot of the sam ple solution from ste p 7 to a 4-m L vial. C ap the vial. 12. Injec t a 20-µL sam ple aliqu ot. 13. Me asu re pe ak area or pe ak heigh t. NOT E 1: If sample peak is larger than the largest standard peak, dilute an aliquot of the rem ain ing sample solution, reanalyze, and apply appropriate dilution factor in the calculations. NOT E 2: To ensure validity of the samples, identify those samples which contain more than 37 µg of form aldehyde. The ca pacity of the sam plers before breakthroug h m ay have been exceeded for these samples, and collection of smaller samples would be warranted. NOTE 3: The size of the 2,4-DNPH peak should be about 2.7 times the size of the formaldehyde-DNPH peak or larger. Otherwise, breakthrough from the sampler may have occurred.

CALCULATIONS: 14. Determine m ass, µg, of form aldehyde, W , found in the sample and the average media blank, B, from the calibration graph.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition