Page:NIOSH Manual of Analytical Methods - 6602.pdf/1

 SULFUR HEXAFLUORIDE by portable GC

SF6

MW: 146.06

METHOD: 6602

CAS: 2551-62-4

RTECS: WS4900000

EVALUATION: FULL

OSHA : 1000 ppm NIOSH: 1000 ppm ACGIH: 1000 ppm (1 ppm = 5.97 mg/m 3 @ NTP)

PROPERTIES:

6602

Issue 1: 15 August 1994

colorless, odorless gas; MP -50.8 °C; sublimes -63.8 °C; d = 5.0 (air = 1)

SYNONYMS: (none)

SAMPLING

MEASUREMENT

SAMPLER:

GAS SAMPLING BAG

TECHNIQUE:

GAS CHROMATOGRAPHY (PORTABLE)

FLOW RATE:

0.02 to 0.1 L/min; fill bag ≤ 80% of capacity; spot samples (step 2.a.) or TWA samples (step 2.b.)

ANALYTE:

sulfur hexafluoride

COLUMN:

38 cm x 6-mm OD stainless steel, packed with 100-120 mesh activated alumina

stable 28 h in 5-layers bags; 8 h in Tedlar bags

DETECTOR:

electron capture

CALIBRATION:

bag standards or calibrated gas mixtures

RANGE:

0.1 to > 10,000 ppb

SAMPLE STABILITY:

FIELD BLANKS:

in bag from a non-work area

ESTIMATED LOD: 0.05 ppb PRECISION (Sr):

0.022

ACCURACY RANGE STUDIED:

0.1 to 200 ppb

BIAS:

- 0.4%

ˆ ): 0.022 OVERALL PRECISION (S rT ACCURACY:

± 4.8%

APPLICABILITY: The working range of this method is 0.1 to 10,000 ppb in relatively non-complex atmospheres where sulfur hexafluoride is known to be present, such as indoor environments where ventilation testing is being conducted by the rel ease of SF6.

INTERFERENCES: Any compound having the same or nearly the same retention time as sulfur hexafluoride on the column may cause a positive interference. Carbon dioxide, another common substance monitored to evaluate ventilation systems in ind oor air quality studies, will not interfere.

OTHER METHODS: Method S244 [1] describes the determination of SF 6 by thermal conductivity detection after collection in bags, with a lower limit of 500 ppm, i.e., not sensitive enough for ventilation studies.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94