Page:NIOSH Manual of Analytical Methods - 5525.pdf/4

 ISOCYANAT ES, TOTA L (MAP): METHO D 5525, Issue 1, dated 15 March 2003 - Page 4 of 17 3. Impinger + filter sampling a. Sam ple with an im pinger followed by a M AP-coated filter whe n im pinger sa m pling is d esired (e.g ., a highly reactive aerosol) but particles < 2 µm are suspected to be present (e.g., condensation or com bus tion ae rosol). Particles < 2 µm are n ot collected efficiently by impingers [1,2]. b. Attach the inlet of the filter cassette to the outlet of the impinger and the outlet of the filter ca sse tte to the pum p with flexible tu bing. The portion of the tubing connecting the impinger to the filter should be free of phthalate plasticizer (Fluran TM tubing is acc epta ble, PVC tubing is not.) c. Sam ple at a rate of 1 L/min for a total sample size of at least 1 L. d. After sampling, treat the impinger solution as described in step 1.d. If a combined measure of the total isocyanate from the two stage s is de sired, place the filter in the im pinger sa m ple vial. If se para te m eas urem ents of the two sta ges are desired, place the filter in a separate ja r contain ing MAPacetonitrile extraction solution as in step 1.d. e. Store samples in a refrigerator and ship the samples with ice packs. f. Obtain bulk sa m ples and M SDS s as in step 1.f. g. Obtain a minimum of three field controls and three field blanks as described in steps 1.g. and 2.g.

SAMPLE PREPARATION: NOT E 1: NOT E 2:

For correct sample preparation, follow directions below for type of sampler used: glass fiber filter (4); im pinger (5); impinger followed by glass fiber filter (6). Re frigera te all sam ples imm ediately upon rec eipt.

4. Filter and filter extract a. For vapor-only samples received without in-field extraction, follow the procedure in step 1.d. of filter sampling and allow the samples to extract overnight in a refrigerator before proceeding. b. For samples that are extracted in-field, acetylate with 5 µL of acetic anhydride upon receipt of samples. For sam ples that are ex trac ted in the lab, acetylate with 5 µL of acetic anhydride after overnight extra ction. Let these re act at least tw o ho urs at room tem pera ture or overnight in the refrigerator before proceeding. c. Attach the outlet of a 0.45-µm PTFE Luer-lock syringe filter to the S PE vacuum m anifold with disposable liner. Place an empty polypropylene syringe barrel in the inlet of the syringe filter. Add the entire extra ction s olution into the syringe barrel. d. Force the sam ple through the PT FE filter us ing either positive or negative pressure and collect in a glass vial with a PTFE-lined cap. 5. Impinger a. Attach a 6-mL SPE cartridge containing 500 mg silica gel to a solid-phase extraction (SPE) vacuum manifold with disposable liners. b. Condition the SPE cartrid ge with 2 m L butyl benzoate, bringing the liquid level down to the top of the sorbent bed. c. Add a 5.0-m L aliquot of sample solution to the SPE cartridge, adjusting the vacuum of the SPE m anifold to obtain a flow of a pprox. 1 to 2 m L/m in and sto pping when the liquid level reaches the top of the sorb ent. d. Add 6 m L methylene chloride to th e SPE cartrid ge. Elu te th e cartridge at 1 to 2 m L/m in until th e liquid level reach es the top of the sorb ent. D iscard all elua te collected up to this po int. e. Add 3 mL of 9:1 acetonitrile-methanol to the SPE cartridge. Elute at approx.1-2 mL/m in until the liquid level re aches th e top of the sorbent. C ollect th e eluate in a pre-weighed glass vial. f. Add 3 m L of m etha nol to the SP E ca rtridge. Elute and collect the eluate in the same vial as in step 5.g. g. Use a stream of nitrogen to reduce the volum e to exactly 1.0 mL. Rec onstitute to volum e if necessary by addition of acetonitrile. Determine exact volume using the sample weight and the density of acetonitrile (0.786 g/m L). 6. Impinger + Filter a. Follow steps under Sample Preparation step 5 for the impinger part of the sample. b. Follow steps under Sample Preparation step 4 for the filter part of the sample.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition