Biomaterial Database

Nitrite interference and elimination in diphenylcarbazide (DPCI) spectrophotometric determination of hexavalent chromium. 2015

Da He, and Maosheng Zheng, and Tao Ma, and Jinren Ni

Shenzhen Key Laboratory for Heavy Metal Pollution Control and Reutilization, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China; Department of Environmental Engineering, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Peking University, Beijing 100871, China E-mail: jinrenni@pku.edu.cn; nijinren@iee.pku.edu.cn.

Cr(VI) is highly noted as a carcinogenic, mutagenic, and teratogenic pollutant. However, accurate determination of Cr(VI) in aqueous samples is difficult using the conventional diphenylcarbazide (DPCI) spectrophotometric method upon being interfered by co-existed nitrite. This paper illustrates how to eliminate the nitrite influence in a simple but efficient method based on a detailed analysis of interference mechanism. High-performance liquid chromatography analysis revealed that under acidic condition, DPCI was oxidized by nitrite to other substrates, which could not react with Cr(VI). The final oxidation product of DPCI was further purified by thin-layer chromatography and identified as diaryl carbodiazone by Fourier Transform Ion Cyclotron Resonance-Mass Spectrometry (FTICR-MS) and nuclear magnetic resonance. Consequently, an improved method was proposed by simply adding sulfamic acid for eliminating the nitrite interference in Cr(VI) determination. The proposed method was successfully confirmed by the accurate recovery of Cr(VI) from spiked water samples and further proven with inductively coupled plasma-atomic emission spectroscopy, which demonstrated a great potential for determining Cr(VI) concentration in aqueous samples containing nitrite.

UI	MeSH Term	Description	Entries
D009573	Nitrites	Salts of nitrous acid or compounds containing the group NO2-. The inorganic nitrites of the type MNO2 (where M	Nitrite
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D002857	Chromium	A trace element that plays a role in glucose metabolism. It has the atomic symbol Cr, atomic number 24, and atomic weight 52. According to the Fourth Annual Report on Carcinogens (NTP85-002,1985), chromium and some of its compounds have been listed as known carcinogens.
D004160	Diphenylcarbazide	Used as an indicator in titrating iron and for the colorimetric determination of chromium and the detection of cadmium, mercury, magnesium, aldehydes, and emetine.	1,5-Diphenylcarbazide,S-Diphenylcarbazide,1,5 Diphenylcarbazide,S Diphenylcarbazide
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D013054	Spectrophotometry, Atomic	Spectrophotometric techniques by which the absorption or emmision spectra of radiation from atoms are produced and analyzed.	Spectrophotometry, Atomic Absorption,AA Spectrophotometry,AE Spectrophotometry,Atomic Absorption Spectrophotometry,Atomic Emission Spectrophotometry,Atomic Spectrophotometry,Inductively Coupled Plasma Atomic Emission Spectrophotometry,Inductively Coupled Plasma Atomic Emission Spectroscopy,Spectrophotometry, Atomic Emission,AA Spectrophotometries,AE Spectrophotometries,Absorption Spectrophotometry, Atomic,Emission Spectrophotometry, Atomic,Spectrophotometries, AA,Spectrophotometries, AE,Spectrophotometry, AA,Spectrophotometry, AE
D014874	Water Pollutants, Chemical	Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.	Chemical Water Pollutants,Landfill Leachate,Leachate, Landfill,Pollutants, Chemical Water