Ultra-sensitive determination of cadmium in rice and water by UV–vis spectrophotometry after single drop microextraction

In this work, a new method based on single drop microextraction (SDME) preconcentration using tetrachloromethane (CCl4) as extraction solvent was proposed for the spectrophotometric determination of cadmium in rice and water samples. The influence factors relevant to SDME, such as type and volume of extractant, stirring rate and time, dithizone concentration, pH, drop volume and instrumental conditions were studied systematically. Under the optimal conditions, the limit of detection (LOD) was 0.5 ng L−1, with sensitivity enhancement factor (EF) of 128. The different maximum absorption wavelength caused by the different extraction acidity compared with some conventional works and the enhancement effect of acetone (dilution solvent) for the spectrophotometric determination were the two key factors of the high EF and sensitivity. The proposed method was applied to the determination of rice and water samples with satisfactory analytical results. The proposed method was simple, rapid, cost-efficient and sensitive.

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► The first report of SDME pre-treatment coupled with UV–vis for Cd detection.
► Conventional UV–vis can accomplish ultra-trace metal detection via the combination.
► It is a simple and relatively greener method with impressive detectability and novelty.
► It can be useful in less developed area without more advance analytical instruments.