Tungsten (Soluble and Insoluble) (7074)
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 TUNGSTEN (soluble and insoluble): METHOD 7074, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS: 1. 2. 3. 4. 5. 6. 7.
8.
EQUIPMENT:
Nitric acid, conc.* Hydrofluoric acid, conc.* Hydrochloric acid, conc.* Hydrochloric acid, 1% (v/v). Add 26.5 mL conc. HCl to 500 mL water; dilute to 1 L. Sodium hydroxide, 0.5 M. Dissolve 20 g NaOH in 500 mL water; dilute to 1 L. Sodium sulfate, 20% (w/v). Dissolve 20 g Na 2SO 4 in 80 mL water; dilute to 100 mL. Calibration stock solution, 10 mg W/mL. Commercially available or dissolve 1.5985 g Na 2WO 4 (dried at 125 °C) in water; add 10 mL 0.5 M NaOH and dilute to 100 mL. Water, distilled, deionized.
See SPECIAL PRECAUTIONS.
1. Sampler: cellulose ester membrane filter, 0.8-µm pore size, 37-mm diameter; in cassette filter holder. 2. Personal sampling pump, 1 to 4 L/min, with flexible connecting tubing. 3. Atomic absorption spectrophotometer with a nitrous oxide-acetylene burner head. 4. Tungsten hollow cathode lamp. 5. Two-stage regulators for N 2O and acetylene. 6. Beakers, PTFE, 100-mL (with covers).* 7. Volumetric flasks, 10-, 25- and 100-mL.* 8. Assorted volumetric pipets, as needed, with pipet bulb.* 9. Hotplate for use at 150 °C. 10. Steam bath or 100 °C hotplate. 11. Filtering apparatus (funnel, clamp, frit, holder) with 47-mm, 0.45-µm pore size cellulose ester membrane filter and collection vessel.
Clean all labware with conc. nitric acid and rinse thoroughly with distilled water before use.
SPECIAL PRECAUTIONS: Wear protective equipment (gloves, labcoats, and safety glasses) when working with HF. Do not use HF with glass labware. Perform all acid digestions in a fume hood. SAMPLING: 1. 2.
Calibrate each personal sampling pump with a representative sampler in line. Sample at an accurately known flow rate between 1 and 4 L/min for a total sample size of 200 to 1000 L. Do not exceed 2 mg total dust loading on the filter.
SAMPLE PREPARATION: 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
Open the cassette and transfer the filter to the filtering apparatus on top of a 47-mm filter. Add 3 mL deionized water to the sample filter, allow it to stand 3 min, apply vacuum to transfer the extract to the holding vessel, and repeat with an additional 3 mL water. Transfer the extracts to a 10-mL volumetric flask, add 1.0 mL 20% Na 2SO 4, dilute to volume, and analyze for soluble tungsten (steps 17 through 19). Digest the filters and residue in a covered PTFE beaker with 5.0 mL conc. HNO 3 and 5.0 mL conc. HF at 150 °C. Remove the beaker cover and reduce the volume to 2 mL (150 °C). Take to dryness at 100 °C. Remove from heat, cool, add 10 mL 1% HCl, and agitate manually for 5 min. Filter through an additional 47-mm filter (the filtrate may be analyzed for cobalt). Digest the filter and residue in a PTFE beaker with 5.0 mL conc. HNO 3 and 5.0 mL conc. HF at 150 °C. Remove the beaker cover and reduce the volume to 1 mL (150 °C). If filter residue (dark, charred material) is visible, add additional HNO 3 and HF (2 mL each). Take to near-dryness at 100 °C. Dissolve residue in beaker with 2.5 mL 0.5 M NaOH and 2.5 mL 20% Na 2SO 4 at 100 °C (15 min). Transfer to a 25-mL volumetric flask and dilute to volume.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94 TUNGSTEN (soluble and insoluble): METHOD 7074, Issue 2, dated 15 August 1994 - Page 3 of 3 CALIBRATION AND QUALITY CONTROL: 15.
16.
Calibrate with at least six working standards over the range 0.05 to 12 mg W per sample. a. Add known amounts of calibration stock solution to 100-mL volumetric flasks containing 10 mL 0.5 M NaOH and 10 mL 20% Na 2SO 4; dilute to volume with distilled, deionized water. b. Analyze together with samples and blanks (steps 17 through 19). c. Prepare calibration graph (absorbance vs. solution concentration, µg/mL). Analyze three quality control blind spikes and three analyst spikes to ensure that the recovery and calibration graph are in control (steps 6 through 14 and 17 through 19).
MEASUREMENT: 17. 18. 19.
Set spectrophotometer to conditions on page 7074-1. Aspirate standards and samples. Record absorbance readings. If the absorbance values for the samples are outside of the range of the standards, dilute the solutions with 0.05 M NaOH/2% Na 2SO 4 solution, reanalyze, and use the appropriate dilution factor in calculations.
CALCULATIONS: 20. 21.
Determine the solution concentrations of tungsten in the sample, C s (µg/mL), and average media blank, C b (µg/mL), from the calibration graph. Using the solution volumes, mL of the sample (V s) and media blank (V b), calculate the concentration of tungsten, C (mg/m 3), in the air volume sampled, V (L):
EVALUATION OF METHOD: This method is based on P&CAM 271 [3,4] and was further evaluated and ruggedized under contract [1]. Laboratory testing with spiked samples over the ranges of 0.17 to 0.8 mg per sample (soluble) and 0.34 to 7.9 mg per sample (insoluble) gave precisions ( Sr) of 0.079 (soluble) and 0.076 (insoluble) [1]. Both soluble and insoluble tungsten species collected on filters were stable for two weeks [1]. REFERENCES: [1]
[2] [3] [4]
Carlin, L. M., G. Colovos, D. Garland, M. Jamin, M. Klenck, T. Long, and C. Nelson. Analytical Methods Evaluation and Validation: Arsenic, Nickel, Tungsten, Vanadium, Talc and Wood Dust, NIOSH Contract No. 210-79-0060 (1981), available as Order No. PB 83-155325 from NTIS, Springfield, VA 22161. User check, UBTL, Inc., NIOSH Sequence #4213-M (unpublished, May 23, 1984). NIOSH Manual of Analytical Methods, 2nd ed., Vol. 4, P&CAM 271, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). Hull, R. D. Analysis of Tungsten by Atomic Absorption Spectrophotometry: A Feasibility Study, NIOSH, DPSE, MRB, IMDS Technical Report (unpublished, December, 1977).
METHOD WRITTEN BY: R. DeLon Hull, Ph.D., NIOSH/DBBS; additional data obtained under NIOSH Contract 210-79-0060.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94