Page:NIOSH Manual of Analytical Methods - 7600.pdf/1

 CHROMIUM, HEXAVALENT

Cr(VI)

MW: 52.00 (Cr); 99.99 (CrO3)

METHOD: 7600, Issue 2

7600

CAS: 18540-29-9

EVALUATION: FULL

OSHA : 0.1 mg/m 3 (as CrO 3) NIOSH: 0.001 mg/m 3/10 h; carcinogen ACGIH: 0.050 mg/m 3 (as Cr, soluble); some insoluble chromates are human carcinogens

RTECS: GB6262000 Issue 1: 15 May 1989 Issue 2: 15 August 1994

PROPERTIES: oxidizing agent

SYNONYMS: vary depending upon the compound

SAMPLING

MEASUREMENT

SAMPLER:

FILTER (5.0-µm PVC membrane)

TECHNIQUE:

VISIBLE ABSORPTION SPECTROPHOTOMETRY

FLOW RATE:

1 to 4 L/min

ANALYTE:

CrO 42--diphenylcarbazide complex

VOL-MIN: -MAX:

8 L @ 0.025 mg/m 3 400 L

EXTRACTION SOLUTION:

0.5 N H 2SO 4 or 2% NaOH3% Na 2CO 3 (see steps 4 and 5)

SHIPMENT:

routine WAVELENGTH:

540 nm; 5-cm path length

CALIBRATION:

standard solutions of K 2CrO 4 in 0.5 N H 2SO 4

RANGE:

0.2 to 7 µg per sample

ESTIMATED LOD:

0.05 µg per sample

PRECISION (Sr):

0.029 @ 0.3 to 1.2 µg per sample [3]

SAMPLE STABILITY:

analyze within 2 weeks [1]

FIELD BLANKS:

2 to 10 field blanks per set

ACCURACY RANGE STUDIED:

0.05 to 0.2 mg/m 3 [2] (22-L samples)

BIAS:

- 5.48%

ˆ ): 0.084 [2] OVERALL PRECISION (S rT ACCURACY:

± 18.58%

APPLICABILITY: The working range is 0.001 to 5 mg/m 3 for a 200-L air sample. This method may be used for the determination of soluble Cr(VI) (using 0.5 N H 2SO 4 as extraction solution or insoluble Cr(VI) (using 2% NaOH - 3% Na 2CO 3) [3].

INTERFERENCES: Possible interferences are iron, copper, nickel, and vanadium; 10 µg of any of these causes an absorbance equivalent to about 0.02 µg Cr(VI) due to formation of colored complexes. Interference due to reducing agents (e.g., Fe, Fe ++ ) is minimized by alkaline extraction (step 5).

OTHER METHODS: This method combines and replaces P&CAM 169 [1], S317 [2] and P&CAM 319 [3]; the Cr(VI) criteria document [4] contains a method similar to P&CAM 169. Method 7604 is also specific for hexavalent chromium, using ion chromatography for measurement.

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