SULFUR DIOXIDE
SO2
MW: 64.06
METHOD: 6004, Issue 2
OSHA : NIOSH: ACGIH:
CAS: 7446-09-5
6004
RTECS: WS4550000
EVALUATION: PARTIAL
5 ppm 2 ppm; STEL 5 ppm; Group I Pesticide 2 ppm; STEL 5 ppm (1 ppm = 2.62 mg/m 3 @ NTP)
Issue 1: 15 May 1989 Issue 2: 15 August 1994
PROPERTIES:
gas; vapor density 2.26 (air = 1); BP -10 °C; MP -72.7 °C; nonflammable
SYNONYMS: none
SAMPLING SAMPLER:
MEASUREMENT
FILTER + TREATED FILTER (cellulose + Na 2CO 3; preceded by 0.8-µm cellulose ester membrane)
TECHNIQUE:
ION CHROMATOGRAPHY
ANALYTE:
sulfite and sulfate ions
FLOW RATE:
0.5 to 1.5 L/min
EXTRACTION:
10 mL 1.75 m M NaHCO 3/2.0 mM Na 2CO 3
VOL-MIN: -MAX:
4 L @ 5 ppm 200 L
INJECTION LOOP VOLUME: 50 µL
SHIPMENT:
routine
SAMPLE STABILITY:
not determined
FIELD BLANKS:
2 to 10 field blanks per set
ELUENT:
1.75 mM NaHCO 3/2.0 mM Na 2CO 3, 2 to 3 mL/min
COLUMNS:
Ion Pac AS4A separator, Ion Pac AG4A guard; micromembrane suppressor [2]
CONDUCTIVITY SETTING: CALIBRATION:
10 µS full scale
standard solutions of SO 23- and SO 24in eluent
ACCURACY RANGE: RANGE STUDIED:
not studied
BIAS:
not determined
ˆ ): not determined OVERALL PRECISION (S rT ACCURACY:
11 to 200 µg SO 2 per sample
ESTIMATED LOD:
3 µg SO 2 per sample [2]
PRECISION (Sr):
0.042 [2]
not determined
APPLICABILITY: The working range is 0.2 to 8 ppm (0.5 to 20 mg/m 3) for a 100-L air sample. The method is applicable to STEL samples. SO 2 is collected on the back (treated) filter. Sulfuric acid, sulfate salts, and sulfite salts are collected on the front f ilter and may be quantitated as total particulate sulfate.
INTERFERENCES: Sulfur trioxide gas, if present in dry atmospheres, may give a positive interference for SO 2.
OTHER METHODS: This revises P&CAM 268 [3]. P&CAM 146 [4], P&CAM 163 [5], and S308 [6] use 0.3 N H 2O 2 for sampling, followed by titration with NaOH or barium perchlorate. P&CAM 160 [7] uses tetrachloromercurate solution and visible spectrophotometry. P&CAM 204 [8] uses a solid sorbent (molecular sieve 5A), thermal desorption, and mass spectrometry.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
