METHYL BROMIDE 2520 CH3Br MW: 94.94 CAS: 74-83-9 RTECS: PA4900000 METHOD: 2520, Issue 2
EVALUATION: FULL
OSHA: C 20 ppm (skin) NIOSH: lowest feasible; carcinogen; Group I Pesticide ACGIH: 5 ppm (skin)
(1 ppm = 3.95 mg/m³ @ NTP)
Issue 1: 15 August 1990 Issue 2: 15 May 1996
PROPERTIES: gas; d 1.73 g/mL @ 0 °C; BP 4 °C; VP 189.34 kPa (1420 mm Hg) @ 20 °C
SYNONYMS: monobromomethane; bromomethane SAMPLING SAMPLER: SOLID SORBENT TUBES (two petroleum charcoal tubes, 400 mg and 200 mg; drying tube, 9-g Na2SO4, necessary at humidity >50%)
MEASUREMENT TECHNIQUE:
GAS CHROMATOGRAPHY, ATOMIC EMISSION DETECTION (GC-AED) monitoring Br, C, and H channels
ANALYTE:
methyl bromide
DESORPTION:
400 mg tube: 3 mL methylene chloride; 200 mg tube: 2 mL methylene chloride
FLOW RATE: 0.01 to 0.1 L/min VOL-MIN: -MAX:
1 L @ 5 ppm 5 L with drying tube, 1 L w/o dying tube [1]
SHIPMENT: ship on dry ice at −10 °C [1] SAMPLE STABILITY: six days at −10 °C [1] BLANKS:
2 to 10 field blanks per set ACCURACY
RANGE STUDIED:
INJECTION VOLUME:
1 µL
TEMPERATURE-INJECTION: 250 °C -TRANSFER LINE/ CAVITY BLOCK: 250 °C -COLUMN: 30 °C, 3.5 min; 12 °C /min to 130 °C; hold 1 min CARRIER GAS:
helium
COLUMN:
DB-1 capillary, 30 m × 0.32-mm ID, 1.0-µm film thickness; 1 m × 0.53-mm deactivated fused silica pre-column
CALIBRATION:
brominated compounds in methylene chloride
RANGE:
33.0 to 2687 µg bromine per sample
0.84 to 32.0 ppm (5-L samples)
BIAS: −5.2% OVERALL PRECISION ( ): 0.089 ACCURACY:
±19.4%
ESTIMATED LOD: 16.6 µg per sample [1] PRECISION ( ):
0.066 [1]
APPLICABILITY: The working range is 0.84 to 32.0 ppm (3.3 to 126 mg/m³) for a 5-L sample. Ceiling measurement samples may require dilution when analyzed. INTERFERENCES: Water vapor interferes with collection at relative humidities (RH) >50%. To eliminate the interference, precede the sampling train with a drying tube, and limit the sample volume to 5 L. If drying tubes are not available, limit the sample volume to 1 L under humid conditions. OTHER METHODS: This is Method 2520 [2] revised to account for humidity effects, as well as instability of standards and samples. Other researchers [3] have prepared methyl bromide standards gravimetrically and used GC-ECD for analysis. The gravimetric calibration procedure did not give consistent results when compared with the procedure used in this revision of Method 2520. GC-ECD with a Porapak Q capillary column may be an alternative technique to GC-AED, if other bromine standards are used to confirm the concentration of methyl bromide standards.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
