Page:NIOSH Manual of Analytical Methods - 3507.pdf/2

 ACETALDEHYDE by HPLC: METHOD 3507, Issue 2, dated 15 August 1994 - Page 2 of 4

REAGENTS:

EQUIPMENT:

1.	Acetaldehyde.* 2.	Citric acid. 3.	Disodium hydrogen phosphate (Na2HPO4). 4.	Girard T reagent [(carboxymethyl)trimethylammonium chloride hydrazide] recrystallized from 95% ethanol. 5.	Water, distilled, deionized (DD). 6.	Ethanol, 95%. 7.	Sodium dihydrogen phosphate monohydrate (NaH2PO4•H2O). 8.	Girard T solution: 5.39 g citric acid, 6.63 g Na2HPO4, and 16.77 g Girard T reagent diluted to 500 mL with DD water. Store in annealed flask in the dark. Use within two weeks. 9.	HPLC mobile phase: 0.22 M Na2HPO4•H2O, 0.019 M NaH2PO4•H2O in 20% ethanol. Dissolve and dilute 31.2 g Na2HPO4 and 26.2 g NaH2PO4•H2O to 1 L with DD water. Filter through 5-µm PTFE filter and degas prior to use. Bubble helium through the solution to prevent bacterial growth. 10.	Calibration stock solution, 4.32 mg/mL acetaldehyde in 0.2 M Girard T solution. Weight 216 mg freshly-distilled acetaldehyde into 50-mL volumetric flask containing 49 mL Girard T solution. Make to volume with Girard T solution. Use within one day. 11.	Helium.

1.	Sampler: bubbler, glass, midget, with fritted glass stems, annealed,† with PTFE stoppers for shipping. 2.	Personal sampling pump, 0.1 to 0.5 L/min, with trap made from midget bubbler with stem broken off and inert, flexible connecting tubing. 3.	High pressure liquid chromatograph, with 245-nm UV detector, integrator, and column (page 3507-1) with 50-µL injection loop or autosampler. 4.	Syringe, 2-mL, Luer-lock. 5.	Distillation apparatus for preparation of high purity acetaldehyde. 6.	Flasks, volumetric, 1-L; 10-,50-, and 100-mL; and 500-mL, annealed.† 7.	Pipets, 0.02- to 1-mL; 5-, 10-, and 15-mL. 8.	Marker, glass. 9.	Cylinder, graduated, 250-mL. 10.	Filter, 5-µm, PTFE, 37-mm, with holder for liquid filtration. 11.	Balance, readable to 0.1 mg. Heat in an oxidizing atmosphere at 580 °C.

†

SPECIAL PRECAUTIONS: Acetaldehyde is extremely volatile and a fire hazard. Cool containers of acetaldehyde to ice bath temperature to reduce pressure buildup and open in an exhaust hood only. SAMPLING: 1.	Calibrate each personal sampling pump with a representative sampler and trap in line. 2.	Add exactly 15 mL Girard T solution to each bubbler using a 15-mL pipet. Mark the initial liquid level in the bubbler with a glass marker. Make impinger-to-trap and trap-to-sampling pump connections with flexible inert tubing. 3.	Sample at an accurately known flow rate between 0.1 and 0.5 L/min for a total sample size of 6 to 60 L. NOTE:	Higher flow rates will cause frothing of the collection medium. If amount of liquid condensed in the trap is greater than 1 mL, collection efficiency of bubbler may be reduced and sample may be invalid.
 * See SPECIAL PRECAUTIONS.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition