Analytical method for the determination of chromium (VI) compounds

Translation of DGUV Information 213-505 (former BGI 505-05 or ZH1/120.5)

Synonym: Hexavalent chromium

Method 04 – Photometry

Sampling with a pump and collection on a quartz fibre filter. Photometry after extraction.

This analytical method is a validated measurement procedure for the determination of hexavalent chromium in workplace air averaged over the sampling period after personal or stationary sampling.

Principle

A pump draws a defined volume of air through a quartz fibre filter. The hexavalent chromium compounds retained on the filter in the form of dusts and aerosols are determined using the diphenylcarbazide method.

Limit of quantification (LOQ)

Absolute: 0.1 µg of Cr(VI) for a measurement solution of 50 mL and a cuvette layer thickness of 50 mm.

Relative:  

0.24 µg/m³ of Cr(VI) for an air sample volume of 0.42 m³, an extraction solution of 10 mL, a measurement solution of 50 mL and a cuvette layer thickness of 50 mm.
0.48 µg/m³ of Cr(VI) for an air sample volume of 0.42 m³, an extraction solution of 10 mL, a filtrate solution of 5 mL, a measurement solution of 50 mL and a cuvette layer thickness of 50 mm, aliquot factor 2.
0.083 µg/m³ of Cr(VI) for an air sample volume of 1.2 m³ an extraction solution of 10 mL, a measurement solution of 50 mL and a cuvette layer thickness of 50 mm.
0.17 µg/m³ of Cr(VI) for an air sample volume of 1.2 m³, an extraction solution of 10 mL and a filtrate solution of 5 mL, a measurement solution of 50 mL and a cuvette layer thickness of 50 mm, aliquot factor 2.

Issue

March 2017

The complete measuring method is available in the Wiley Online Library: Method for the determination of hexavalent chromium in workplace air using photometry (The MAK Collection for Occupational Health and Safety 2019, Volume 4, No 1, 2019).

Method 03 – IC – withdrawn

Sampling with a pump and collection on a glass fibre filter, ion chromatography (IC) after wet-ashing

Note: Chemical inert pumps have to be used in order to avoid corrosion.

This method permits the determination of hexavalent chromium concentrations in working areas averaged over the sampling time after personal or stationary sampling.

Principle 

With a pump a measured air volume is drawn through a binder-free annealed glass fibre. The chromium compounds deposited on the filter in the form of dusts and aerosols are transferred to a measured volume of a buffer solution, dissolved by means of an ultrasonic bath and finally filtered through a membrane filter.

The ion chromatographic measuring procedure using one column, post-column derivatization and direct UV-VIS detection permits the simultaneous determination of chromium (III) and chromium (VI). Prior to determination, derivation of trivalent chromium compounds is carried out by boiling the measuring solution with the eluent concentrate. In this solution the chromium(III) reacts with pyridine-2,6-dicarboxylic acid (PDCA) to form a blue-violet, anionic chromium (III)-PDCA complex. In the subsequent ion chromatography the chromium (III) is separated from the chromate (chromium (VI)). Post-column derivatization then leads to the reduction of chromate by 1,5-diphenylcarbazide (DPC) to yield a red-violet chromium (III)-DPC complex. The complexes are then analysed in a UV-VIS detector.

Limit of quantification (LOQ)

For personal sampling (calculated as CrO₃):

Absolute: 0.2 ng.

Relative: 0.24 µg/m³ for 0.42 m³ air sample, 10 mL sample solution and 200 µL injection volume of the measuring solution.

For stationary sampling:

Absolute: 0.2 ng.

Relative: 0.01 µg/m³ for 45 m³ air sample, 50 mL sample solution and 200 µL injection volume of the measuring solution.

Issue

May 1993

Withdrawn

June 2017

The complete measuring method is available in the Wiley Online Library: Method for the determination of hexavalent chromium (Analyses of Hazardous Substances in Air, Volume 4, 1999).

Method 02 – Photometry – withdrawn

Sampling with a pump and collection on a glass fibre filter, ion chromatography (IC) after wet-ashing

This method permits the determination of hexavalent chromium concentrations in working areas averaged over the sampling time after personal or stationary sampling.

Principle 

With a pump a measured air volume is drawn through an annealed glass fibre filter. The chromium compounds collected on the filter as dusts or aerosols are determined by the diphenylcarbazide
method.

Limit of quantification (LOQ) (calculated as CrO3)

1 μg for 50 mL sample solution and 10 mm optical path length.

For personal sampling:

4.8 μg/m³ for 0.42 m³ air sample, 10 mL ashing solution and 5 mL filtrate volume.

For stationary sampling:

0.04 μg/m³ for 0.45 m³ air sample, 20 mL ashing solution and 10 mL filtrate volume.

Issue

May 1993

Withdrawn

February 2016

The complete measuring method is available in the Wiley Online Library: Method for the determination of hexavalent chromium (Analyses of Hazardous Substances in Air, Volume 4, 1999).