Table 3.

Analytical methods for total Cr, Cr (III), and Cr (VI) in water samples. AAS, atomic absorption spectroscopy; GFAAS, graphite furnace atomic absorption spectrometry; ICP-MS; inductively coupled plasma mass spectrometry; ICP-AES, inductively coupled plasma atomic emission spectroscopy; HPLC, high-performance liquid chromatography; DPC, 1,5 diphenylcarbazide.

Sample Description and Cr Oxidation State	Procedure	Analytical Method	Detection Limit	References
Water, wastewater, and solid wastes (total dissolved Cr)	For the determination of dissolved Cr in a filtered aqueous sample aliquot, nitric acid is added to the sample, and then it is diluted to a predetermined volume and mixed before analysis.	ICP-OES	6.1 µg L−1	[80]
Groundwater, surface water and drinking water, wastewater, sludges, and soils (total dissolved Cr)	The same as the above procedure.	ICP-MS	0.08 µg L−1	[81]
Groundwater, surface water, drinking water, storm runoff, industrial and domestic wastewater (total dissolved Cr)	The same as the above procedure.	GFAA	0.1 µg L−1	[82]
Drinking water, groundwater, and water effluents (Cr (VI))	A filtered aqueous sample is adjusted to a pH of 9–9.5 with a buffer solution. A 50–250 μL aliquot of sample is introduced into ion chromatograph and separated on an anion exchange column. Post-column derivatization with DPC is followed by detection to 530 nm.	Ion chromatography associated with post-column derivatization and UV/VIS detection	0.3 µg L−1	[83]
Drinking water (dissolved Cr (VI))	Samples are analyzed by direct injection. An aliquot of 1 mL of sample is introduced into the ion chromatograph and Cr (VI) is separated from the other matrix components by an anion exchange column followed by derivatization with DPC.	Ion chromatography with post-column derivatization and UV/VIS detection	0.0044–0.015 µg L−1	[78]
Drinking water (Cr (VI))	A 2 mL aliquot of sample is transferred to a glass vial and sulphuric acid (1 mL 0.2 M) and DPC (1 mL 0.5% w/v) are added. Following, the absorbance is measured in microcuvettes with 1 mm light path at 543 nm against reagent blank.	Colorimetric method based on DPC dye for incorporation into a microfluidic detection system	0.023 µg L−1	[84]
Drinking water, surface water, and certain domestic and industrial effluents (dissolved Cr (VI))	Chelation of Cr (VI) with ammonium pyrrolidine dithiocarbamate (APDC) and extraction with methyl isobutyl ketone (MIBK) at pH 2.4. The extract is aspirated into the flame of the atomic absorption spectrophotometer.	AAS	2.3 µg L−1	[85]
Rain water, river water, spring water (Cr (VI))	Cr (VI) is collected as DPC complex on a column of chitin in the presence of dodecyl sulfate as counter-ion. The Cr-DPC complex retained on the chitin is eluted with a methanol–1 M acetic acid mixture, and the absorbance of the eluent is measured at 541 nm.	Preconcentration on a chitin column and spectrophotometric determination	0.05 µg L−1	[86]
Groundwater (Cr (VI)	A 25 mL aliquot of sample is added to 1 mL of 2.5 M H2SO4 and 1 mL of DPC 0.5%. The absorbance is measured after 10 min at 540 nm with a UV/VIS spectrophotometer using a cell with optical pathlengths of 10 cm.	Colorimetric assay using S-DPC	1 µg L−1	[22]
Drinking water (Cr (III) and Cr (VI))	On the basis of the type of ion exchange column used, HPLC is used to separate one of the two chromium forms. Following, a coupled ICP-MS is used to quantify the concentration of the species before and after the separation step.	HPLC-ICP-MS	0.005 to 0.5 µg L−1 (Cr (III)) 0.009 to 1.0 µg L−1 (Cr (VI))	[79]
Sea water (Cr (III) and Cr (VI))	A solid-phase extraction using anion exchange resins for Cr (VI) adsorption and chelating resins for Cr (III) adsorption is performed	ICP-MS	0.03 (Cr (III)) and 0.009 (Cr (VI))	[73]