Page:NIOSH Manual of Analytical Methods - 7074.pdf/1

 Rh

Rh

METHOD: 7074, Issue 2

no PEL 1 mg/m³ solubles; STEL³ mg/m³ 5 mg/m³ insolubles; STEL 10 mg/m³ 1 mg/m³ solubles, STEL 3 mg/m³ 5 mg/m³ insolubles, STEL 10 mg/m³ brittle metal; MP 3410 °C; valence 2,3,4,5,6

wolfram.

FILTER (0.8-μm cellulose ester membrane) 1 to 4 L/min 200 L @ 1 mg/m 3 -MAX: 1000 L routine stable at least 2 weeks @ 25 °C 2 to 10 field blanks per set

0.42 to 2.0 mg/m³ (soluble) [1]; 0.84 to 19.7 mg/m³ (insoluble) [1] + 0.015 0.055 (soluble) [1]; 0.056 (insoluble) [1] ± 12.5%

ATOMIC ABSORPTION, FLAME

tungsten

H₂O; 6 min, 25 °C (soluble)

1:1 HF:HNO₃, 10 mL; 6 h, 150 °C (insoluble)

0.05 M NaOH/2% Na ₂SO₄; 25 mL

nitrous oxide-acetylene, reducing

255.1 nm

none used

W in 0.05 M NaOH and 2% Na₂SO₄

0.1 to 0.5 mg per sample (soluble); 0.25 to 12 mg per sample (insoluble)

50 μg soluble W per sample; 125 μg insoluble W per sample [2]

0.029 [1]

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.

None known. Ni, Mo, V, Mn, Cr, Co and Fe do not interfere at concentrations up to 50 times the tungsten concentration [3].

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