ACETALDEHYDE
CH3CHO
MW: 44.05
METHOD: 3507, Issue 2
CAS: 75-07-0
3507
RTECS: AB1925000
EVALUATION: FULL
OSHA : 200 ppm NIOSH: carcinogen; lowest feasible level ACGIH: 100 ppm; STEL 150 ppm; suspect carcinogen (1 ppm = 1.801 mg/m 3 @ NTP)
PROPERTIES:
Issue 1: 15 August 1987 Issue 2: 15 August 1993
liquid; d 0.78 g /mL @ 20 °C; BP 20.4 °C; MP -123 °C; VP 100 kPa (750 mm Hg; 99% v/v) @ 20 °C; explosive range 4 to 60% in air
SYNONYMS: ethanal; acetic aldehyde.
SAMPLING SAMPLER:
MEASUREMENT
LIQUID IN BUBBLER (midget bubbler containing 15 mL Girard T solution @ pH 4.5)
TECHNIQUE:
HPLC, UV
ANALYTE:
Girard T derivative
FLOW RATE:
0.1 to 0.5 L/min
SAMPLE PREPARATION:
dilute 5 mL sample to 100 mL with HPLC mobile phase
VOL-MIN: -MAX:
6 L @ 200 ppm 60 L
INJECTION VOLUME:
50 µL
SHIPMENT:
seal bubblers to prevent leakage before shipping; protect from light
SAMPLE STABILITY:
1 week @ 25 °C in dark [1]
FIELD BLANKS:
2 to 10 field blanks per set
COLUMN:
50 cm x 2-mm ID SS, Zipax SCX
DETECTOR:
UV @ 245 nm for acetaldehyde
MOBILE PHASE:
HPO 24-/HPO 4- buffer, 0.75 mL/min
CALIBRATION:
standard solutions of acetaldehyde in Girard T reagent
RANGE:
2 to 60 mg per sample [1]
ACCURACY RANGE STUDIED:
170 to 670 mg/m 3 [1] (60-L samples)
BIAS:
1.2%
ˆ ): 0.053 [1] OVERALL PRECISION (S rT ACCURACY:
ESTIMATED LOD: 0.1 mg per sample [1] PRECISION (Sr):
0.024 @ 11 to 43 mg per sample [1]
± 14.4%
APPLICABILITY: The working range is 18 to 372 ppm (33 to 670 mg/m 3) for a 60-L air sample. The method is sensitive enough for short-term exposure sampling and can be used to measure lower concentrations by diluting samples to less than the recommended 100 mL.
INTERFERENCES: Other volatile aldehydes and ketones (e.g., acetone, acrolein, benzaldehyde, formaldehyde, furfural, methyl ethyl ketone, and propionaldehyde) compete for the Girard T reagent which should be kept at a two-fold molar excess over aldehyde concentration. Chromatographic conditions may be adjusted to resolve acetaldehyde from other aldehydes [1].
OTHER METHODS: This revises S345 [2]. Method 2538 is an adaptation of OSHA Method 68, which uses solid sorbent collection and GC analysis. Other reported methods for acetaldehyde use collection in 2,4-dinitrophenylhydrazine solutio n [3,4].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93 ACETALDEHYDE: METHOD 5512, Issue 2, dated 15 August 1993 - Page 2 of 4 REAGENTS: 1. 2. 3. 4.
5. 6. 7. 8.
9.
10.
11.
EQUIPMENT:
Acetaldehyde.* Citric acid. Disodium hydrogen phosphate (Na 2HPO 4). Girard T reagent [(carboxymethyl)trimethylammonium chloride hydrazide] recrystallized from 95% ethanol. Water, distilled, deionized (DD). Ethanol, 95%. Sodium dihydrogen phosphate monohydrate (NaH 2PO 4·H 2O). Girard T solution: 5.39 g citric acid, 6.63 g Na 2HPO 4, 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. HPLC mobile phase: 0.22 M Na 2HPO 4·H 2O, 0.019 M NaH 2PO 4·H 2O in 20% ethanol. Dissolve and dilute 31.2 g Na 2HPO 4 and 26.2 g NaH 2PO 4·H 2O 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. 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. Helium.
2.
3.
Heat in an oxidizing atmosphere at 580 °C.
See SPECIAL PRECAUTIONS. 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.
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 245nm 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.
Calibrate each personal sampling pump with a representative sampler and trap in line. 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. 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.
SAMPLE PREPARATION: 4.
5.
Tap bubbler stem lightly against bubbler body to drain contents into the body. If necessary, bring samples up to the 15-mL mark with distilled water. Swirl bubbler to mix contents well. Do not add solution collected in the trap to the sample. Transfer a 5-mL aliquot to a 100-mL flask and bring to volume with HPLC mobile phase. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93 ACETALDEHYDE: METHOD 5512, Issue 2, dated 15 August 1993 - Page 3 of 4
CALIBRATION AND QUALITY CONTROL: 6.
7.
Calibrate daily with at least six working standards over the range 0.007 to 4 mg acetaldehyde per mL (0.1 to 60 mg acetaldehyde per sample). a. Add known amounts of calibration stock solution to Girard T solution in 10-mL volumetric flasks and dilute to the mark. Dilute 5 mL of each of these solutions to 100 mL with HPLC mobile phase. Prepare at least two blanks in the same manner. b. Analyze together with samples and blanks (steps 8 and 9). c. Prepare calibration graph (peak area vs. mg acetaldehyde per sample). Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.
MEASUREMENT: 8.
9.
Set liquid chromatograph according to manufacturer's recommendations and to conditions given on page 2507-1. Inject 50-µL sample aliquot with injection loop or autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with HPLC mobile phase, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 10. 11.
Determine the mass, mg of acetaldehyde found in the sample (W), and in the average media blank (B). Calculate concentration, C, of acetaldehyde in the air volume sampled, V (L):
EVALUATION OF METHOD: Method S345 was issued on March 16, 1979 [2], and validated over the range 170 to 670 mg/m 3 at 21 °C and 756 mm Hg using a 60-L sample [1,5]. Overall precision, SˆrT, was 0.053 with an average recovery of 101.2% representing a non-significant bias. The concentration of acetaldehyde was independently verified by calibrated gas chromatograph. Collection efficiency of a single bubbler was determined to be >0.998 when 61-L air samples were taken at 0.5 L/min in atmospheres containing 670 mg/m 3 acetaldehyde.
REFERENCES: [1] [2] [3] [4]
Backup Data Report, S345, Acetaldehyde, prepared under NIOSH Contract 210-76-0123 (unpublished). NIOSH Manual of Analytical Methods, 2nd ed., Vol. 5, S345, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). Kuwata, K., M. Uebori and Y. Yamasaki. J. Chromatog . Sci., 17, 264-268 (1979). Lipari, F. and S.J. Swarin. J. Chromatog ., 247, 2970306 (1982).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93 ACETALDEHYDE: METHOD 5512, Issue 2, dated 15 August 1993 - Page 4 of 4 [5]
NIOSH Research Report-Development and Validation of Methods for Sampling and Analysis of Workplace Toxic Substances, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-133 (1980).
METHOD REVISED BY: Eugene R. Kennedy, Ph.D., NIOSH/DPSE; Method S345 was validated under NIOSH Contract 210-760123.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93