Page:NIOSH Manual of Analytical Methods - 3700.pdf/1

 BENZENE by portable GC

C6H6

MW: 78.11

METHOD: 3700, Issue 2

CAS: 71-43-2

EVALUATION:

OSHA : 1 ppm; STEL 5 ppm NIOSH: 0.1 ppm; C 1ppm/15 min (suspect carcinogen) ACGIH: 10 ppm; (suspect carcinogen) (1 ppm = 3.19 mg/m 3 @ NTP)

3700

RTECS: CY1400000

PARTIAL

Issue 1: 15 August 1987 Issue 2: 15 August 1994

PROPERTIES:

liquid; d 0.879 g/mL @ 20 °C; BP 80.1 °C; MP 5.5 °C; VP 12.7 kPa (95.2 mm Hg; 12.5% v/v) @ 25 °C; explosive range 1.3 to 7.1% v/v

SYNONYMS: benzol; cyclohexatriene

SAMPLING

MEASUREMENT

SAMPLER:

AIR BAG (Tedlar)

TECHNIQUE:

GAS CHROMATOGRAPHY (PORTABLE), PHOTOIONIZATION DETECTOR

FLOW RATE:

0.02 (or lower) to 5 L/min (or higher); fill bag to ≤80% of capacity; spot samples possible (step 2.a.)

ANALYTE:

benzene

COLUMN:

CPSil 5CB Macrobore capillary column operated isothermally at 30 °C (other columns and detectors shown in field study to be acceptable).

CALIBRATION:

bag standards or calibrated gas mixtures

RANGE:

lower limit 0.02 to 1 ppm (see Interferences section below); upper limit 500 ppm.

SAMPLE STABILITY:

bags should be analyzed as soon after collection as possible ( ≤4 h).

FIELD BLANKS:

clean air, either in bag or from a non-work area.

ESTIMATED LOD: 0.01 ppm for a 1-mL injection. ACCURACY RANGE STUDIED:

0.03 to 100 ppm [1]

BIAS:

not significant

PRECISION (Sr):

0.127

ˆ ): 0.136 OVERALL PRECISION (S rT ACCURACY:

>± 27%

APPLICABILITY: The working range is 0.02 to 500 ppm (0.06 to 1600 mg/m 3) (see EVALUATION OF METHOD).

INTERFERENCES: Any compounds having the same or nearly the same retention time as benzene on the column in use are potential interferences. Such compounds cause positive interferences, however, and the actual benzene concentration will be less than or equal to the total of the benzene plus these compounds. The presence of a large number of compounds with retenti on time similar to benzene will cause a high background resulting in decreased sensitivity, possibly to the point where the LOQ approaches 1 ppm. Butane, styrene, toluene and xylenes have been shown not to affect this method [1]. Acceptable estimat es of benzene concentration in diesel and gasoline vapors have been made with this method [2].

OTHER METHODS: Methods 1500 (Hydrocarbons, BP 36 - 126 °C) and 1501 (Hydrocarbons, aromatic) use activated charcoal sampler tubes.

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