TECHNIQUE: Ion chromatography with post-column derivatization and UV detection.

APPLICABILITY:  The working range is 0.00025 to 0.1 mg/m 3  for a 200-L air sample. This method can be used for the determination of Cr(VI) using 2% NaOH - 3% Na 2 CO 3  for extraction.

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