TUNGSTEN (soluble and insoluble)
W
MW:
183.85
METHOD: 7074, Issue 2
OSHA : no PEL NIOSH: 1 mg/m 3 5 mg/m 3 ACGIH: 1 mg/m 3 5 mg/m 3
CAS: 7440-33-7
7074
RTECS: Y07175000
EVALUATION: FULL
Issue 1: 15 February 1984 Issue 2: 15 August 1994
PROPERTIES: brittle metal; MP 3410 °C; valence 2,3,4,5,6 solubles; STEL 3 mg/m 3 insolubles; STEL 10 mg/m 3 solubles, STEL 3 mg/m 3 insolubles, STEL 10 mg/m 3
SYNONYMS: wolfram.
SAMPLING SAMPLER:
FILTER (0.8-µm cellulose ester membrane)
FLOW RATE:
1 to 4 L/min
VOL-MIN: -MAX:
200 L @ 1 mg/m 3 1000 L
SHIPMENT:
routine
SAMPLE STABILITY:
stable at least 2 weeks @ 25 °C
BLANKS:
2 to 10 field blanks per set
MEASUREMENT TECHNIQUE:
ATOMIC ABSORPTION, FLAME
ANALYTE:
tungsten
EXTRACTION:
H 2O; 6 min, 25 °C (soluble)
ASHING:
1:1 HF:HNO 3, 10 mL; 6 h, 150 °C (insoluble)
FINAL SOLUTION:
0.05 M NaOH/2% Na 2SO 4; 25 mL
FLAME:
nitrous oxide-acetylene, reducing
WAVELENGTH:
255.1 nm
BACKGROUND CORRECTION:
none used
CALIBRATION:
W in 0.05 M NaOH and 2% Na 2SO 4
RANGE:
0.1 to 0.5 mg per sample (soluble); 0.25 to 12 mg per sample (insoluble)
ACCURACY RANGE STUDIED: BIAS:
0.42 to 2.0 mg/m 3 (soluble) [1]; 0.84 to 19.7 mg/m 3 (insoluble) [1] + 0.015
ˆ ): 0.055 (soluble) [1]; OVERALL PRECISION (S rT 0.056 (insoluble) [1] ACCURACY:
± 12.5%
ESTIMATED LOD: 50 µg soluble W per sample; 125 µg insoluble W per sample [2] PRECISION (Sr):
0.029 [1]
APPLICABILITY: The working range of this method is 0.25 to 5 mg/m 3 (soluble) and 0.6 to 5 mg/m 3 (insoluble) for a 400-L air sample. This is an elemental analysis and not compound-specific. For cemented tungsten carbide samples, cobalt can be quantitatively determined from the HCl extract used to remove interferences.
INTERFERENCES: None known. Ni, Mo, V, Mn, Cr, Co and Fe do not interfere at concentrations up to 50 times the tungsten concentration [3].
OTHER METHODS: This revises P&CAM 271 [1,3]. Method 7300 (ICP-AES) is an alternate measurement method; however, the extraction and ashing procedures described in this method must be followed.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
