Page:NIOSH Manual of Analytical Methods - 7024.pdf/1

 CHROMIUM and compounds, as Cr

Cr

MW: 52.00 (Cr)

CAS: 7440-47-3 (Cr metal) 22541-79-3 [Cr(II)] 16065-83-1 [Cr(III)]

METHOD: 7024, Issue 2

EVALUATION: FULL

OSHA : 1.0 mg/m3 (metal); 0.5 mg/m3 [Cr(II), Cr(III)] NIOSH: 0.5 mg/m3 [Cr metal, Cr(II), Cr(III)] ACGIH: 0.5 mg/m3 [Cr metal, Cr(II), and Cr(III)]; see Method 7600 for Cr(VI)

PROPERTIES:

7024

RTECS: (Cr) GB4200000 Cr(II) GB6260000 Cr(III) GB6261000

Issue 1: 15 February 1984 Issue 2: 15 August 1994

metal; d 7.14 g/cm3; MP 1890 °C; valences +1 to +6 in salts

SYNONYMS: vary depending on the compound

SAMPLING SAMPLER:

FILTER (0.8-µm cellulose ester membrane)

FLOW RATE:

1 to 3 L/min

VOL-MIN: -MAX:

10 L @ 0.5 mg/m3 1000 L

SHIPMENT:

routine

MEASUREMENT TECHNIQUE:

ATOMIC ABSORPTION, FLAME

ANALYTE:

chromium

ASHING:

conc. HCl, 9 mL; 140 °C conc. HNO3, 9 mL; 400 °C

FINAL SOLUTION:

SAMPLE STABILITY: BLANKS:

5% HNO3, 20 mL

FLAME:

nitrous oxide-acetylene, reducing

stable

WAVELENGTH:

357.9 nm

2 to 10 field blanks per set

CALIBRATION:

standard solutions of Cr in 5% HNO3

RANGE:

5 to 250 µg per sample [2,3]

ESTIMATED LOD:

0.06 µg per sample [4]

PRECISION (Sr):

0.04 to 0.06 [5]

ACCURACY 0.4 to 1.8 mg/m3 (insoluble) 0.3 to 1 mg/m3 (soluble) [1] (90-L samples)

RANGE STUDIED:

BIAS:

- 0.64%

ˆ ): OVERALL PRECISION (S rT

0.076 (insoluble) [1] 0.085 (soluble [1]

ACCURACY:

± 20.91%

APPLICABILITY: The working range is 0.05 to 2.5 mg/m3 for a 100-L air sample. This is an elemental analysis for total Cr, not compound specific. Some compounds of Cr may not be dissolved by this method. Aliquots can be analyzed separately for approximately four additional metals.

INTERFERENCES: Interferences from iron and nickel are minimized by using a high temperature flame (reducing nitrous oxide-acetylene or oxidizing air-acetylene).

OTHER METHODS: This method combines and replaces P&CAM 173 [4], P&CAM 152 [5], S323 [2], and S352 [3]. Method 7300 (Elements by ICP-AES) is an alternate analytical method. Hexavalent chromium, sampled on PVC filters, may be determined colorimetrically by Method 7600 or Method 7604.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94