Page:NIOSH Manual of Analytical Methods - 6004.pdf/1

 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