Analytical Sciences

A Highly Sensitive and Selective Method for the Determination of an Iodate in Table-salt Samples Using Malachite Green-based Spectrophotometry

Mongkol KONKAYAN, Nunticha LIMCHOOWONG, Phitchan SRICHAROEN, and Saksit CHANTHAI

Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand

A simple, rapid, and sensitive malachite green-based spectrophotometric method for the selective trace determination of an iodate has been developed and presented for the first time. The reaction mixture was specifically involved in the liberation of iodine in the presence of an excess of iodide in an acidic condition following an instantaneous reaction between the liberated iodine and malachite green dye. The optimum condition was obtained with a buffer solution pH of 5.2 in the presence of 40 mg L⁻¹ potassium iodide and 1.5 × 10⁻⁵ M malachite green for a 5-min incubation time. The iodate contents in some table-salt samples were in the range of 26 to 45 mg kg⁻¹, while those of drinking water, tap water, canal water, and seawater samples were not detectable (< 96 ng mL⁻¹ of limits of detection, LOQ) with their satisfied method of recoveries of between 93 and 108%. The results agreed with those obtained using ICP-OES for comparison.

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