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TUNGSTEN (soluble and insoluble)
7074
W
MW: 183.85
CAS: 7440-33-7
RTECS: Y07175000
METHOD: 7074, Issue 2
EVALUATION: FULL
Issue 1: 15 February 1984
Issue 2: 15 August 1994
Issue 2: 15 August 1994
OSHA:
no PEL
NIOSH:
1 mg/m³ solubles; STEL³ mg/m³
5 mg/m³ insolubles; STEL 10 mg/m³
5 mg/m³ insolubles; STEL 10 mg/m³
ACGIH:
1 mg/m³ solubles, STEL 3 mg/m³
5 mg/m³ insolubles, STEL 10 mg/m³
5 mg/m³ insolubles, STEL 10 mg/m³
PROPERTIES:
brittle metal; MP 3410 °C; valence 2,3,4,5,6
SYNONYMS:
wolfram.
SAMPLING
SAMPLER:
FILTER
(0.8-μm cellulose ester membrane)
(0.8-μm cellulose ester membrane)
FLOW RATE:
1 to 4 L/min
VOL-MIN:
200 L @ 1 mg/m 3
-MAX:
-MAX: 1000 L
SHIPMENT:
routine
SAMPLE STABILITY:
stable at least 2 weeks @ 25 °C
BLANKS:
2 to 10 field blanks per set
ACCURACY
RANGE STUDIED:
0.42 to 2.0 mg/m³ (soluble) [1];
0.84 to 19.7 mg/m³ (insoluble) [1]
0.84 to 19.7 mg/m³ (insoluble) [1]
BIAS:
+ 0.015
OVERALL PRECISION (ŜrT):
0.055 (soluble) [1];
0.056 (insoluble) [1]
0.056 (insoluble) [1]
ACCURACY:
± 12.5%
MEASUREMENT
TECHNIQUE:
ATOMIC ABSORPTION, FLAME
ANALYTE:
tungsten
EXTRACTION:
H₂O; 6 min, 25 °C (soluble)
ASHING:
1:1 HF:HNO₃, 10 mL; 6 h, 150 °C (insoluble)
FINAL SOLUTION:
0.05 M NaOH/2% Na ₂SO₄; 25 mL
FLAME:
nitrous oxide-acetylene, reducing
WAVELENGTH:
255.1 nm
BACKGROUND CORRECTION:
none used
CALIBRATION:
W in 0.05 M NaOH and 2% Na₂SO₄
RANGE:
0.1 to 0.5 mg per sample (soluble);
0.25 to 12 mg per sample (insoluble)
0.25 to 12 mg per sample (insoluble)
ESTIMATED LOD:
50 μg soluble W per sample;
125 μg insoluble W per sample [2]
125 μg insoluble W per sample [2]
PRECISION (Ŝr):
0.029 [1]
APPLICABILITY:
The working range of this method is 0.25 to 5 mg/m³ (soluble) and 0.6 to 5 mg/m³ (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