Page:NIOSH Manual of Analytical Methods - 2016.pdf/2

 FO RM ALD EHY DE: M ETH OD 2016, Issue 2, dated 1 5 Ma rch 2003 - Page 2 of 7 REAGENTS:

EQUIPMENT:

1. Form aldehyde stoc k solution,* aqu eou s, standardized, 1 m g/m L (see AP PEN DIX A ). Alternatively, standardized formaldehyde solution, aqueous, 4 m g/m L, is available commercially from Hach Co., Loveland, CO. 2. Ac eto nitrile,* distilled in glass, low c arbonyl conte nt.** 3. W ater, deionized and distilled. 4. Sulfuric acid, 0.02 N (pH standardization procedu re) or 0.1 N (colorime tric procedure). 5. Sodium hydroxide, 0.01 N. 6. Sodium sulfite (Na2SO 3), 1.13 M (pH proc edu re) or 0.1 M (colorim etric procedu re). Prepare fresh imm ediately before use. 7. Thymophthalein indicator solution, 0.04% (w/v) in 50:50 ethanol:water.

1. Sam pler: Plastic holder containing 0.35 g of 150-250 µm (60-100 mesh) silica gel coated with 1.0 mg of acidified 2,4dinitrophenylhydrazine. Pressure drop across sampler should be less than 28 inches of water (7 kP a) at 1.5 L/min. Sam plers are comm ercially available, [Supelco S10 LpDN PH c artridge, cat. No. 2-101 4; W aters Corp. Sep -Pak X PoSu re Aldehyde Sam pler, part No.W ATO 47205; see APPEND IX B for SKC sam pler]. 2. Pe rsonal sam pling pum p, 0.03 to 1.5 L/m in with flexible connecting tubing. 3. Vials, 4-mL, glass with PTFE-lined rubber septa caps. 4. Vials, 20-mL, glass. NOTE: Do not use vials with “polycone” liners (sources of high formaldehyde blanks)[5,9]. 5. Liquid chrom atograph with UV detector, recorder, integrator, and column (page 2016-1). 6. Syringes, 100-µL, 500-µL and 10-mL. 7. Volumetric flasks, 10-mL, 25-mL, and 1-L. 8. Burets, 50-mL. 9. pH m eter. 10. Mag netic stirrer. 11. Beaker, 50-mL. 12. Flask, Erlenmeyer, 250-mL. 13. Ozone scrubbe r (W aters Corp.)(optional). 14. Aluminum foil or black electrical tape (optional).



See SPECIAL PRECAUTIONS.



Carbonyl content of acetonitrile can be determined by passing 10 mL of the solvent through a cartridge of DNPH-coated silica gel and analyzing by HPLC. Formaldehyde content should be below the LOD.

SPECIAL PRECAUTIONS: Form aldehyde is a suspect ca rcinogen and a proven hum an sensitizer; it sho uld be han dled in a fum e ho od [10-12 ]. Acetonitrile is toxic and is a fire hazard (flash point = 12.8 oC).

SAMPLING: 1. Calibrate each personal sam pling pum p with a rep resenta tive sam pler (and ozo ne scrubber, if used) in line. 2. Open sam pler packet and remove end caps. 3. Attac h sa m pler to the sampling pump with flexible tubing. The W aters sampler is bi-directional and can be connected at either end. NOTE: The sampler does not have a backup section for determination of br ea kt hr ou gh. If h igh concentrations of aldehydes and ketones are a nticipated, conn ect tw o sa m plers in series. The back pressure of the sampling train will be higher and a lower flow rate may be required. 4. Sam ple 1 to 15 L of air at 0.03 to 1.5 L/min. NOTE: To protect from intense light, such as bright sunlight, the sampler can be wrapped with aluminum foil or electrical tape. 5. Plac e en d ca ps o nto the sa m pler and s eal sa m pler in an en velop e. Pro tect sam ples from hea t. 6. Ship sam ples on ice (0 °C ).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition