Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method

• Published in: Journal of environmental sciences (China) Vol. 25; no. 4; pp. 785 - 790
• Main Authors: Yu, Dengbin, Yong, Daming, Dong, Shaojun
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2013; State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022,China
• Subjects: Alum Compounds - toxicity; Aluminum; aluminum potassium sulfate; atomic force microscopy; Borates - toxicity; Borax; Chlorophenols - pharmacology; Electricity; Electrochemical Techniques - methods; electrochemistry; electrodes; electron transport chain; Escherichia coli; Escherichia coli - cytology; Escherichia coli - drug effects; Escherichia coli - growth & development; Escherichia coli - ultrastructure; Feasibility Studies; food additives; Food Additives - toxicity; inhibitory concentration 50; mass transfer; microelectrode arrays; Microelectrodes; Microorganisms; Microscopy, Atomic Force; oxygen; Potassium; potassium sulfate; screening; Sodium nitrite; Sodium Nitrite - toxicity; solutions; Sulfates; Time Factors; toxic substances; Toxicity; Toxicity Tests - methods; aluminum potassium sulfate; food additives; sodium nitrite; borax; microelectrode arrays
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/S1001-0742(12)60119-3

Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an anaiyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose- glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions （solution pH 7.0, 37℃ and reaction for 3 hr）. The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be： sodium nitrite 〉 borax 〉 aluminum potassium sulfate 〉 blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.