The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO3−), perchlorate (ClO4−) and bromate (BrO3−) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.

The presented study investigates the application of MnO₂/3MgO nanocomposite, as a new sorbent for solid phase extraction and determination of trace amounts of Pb²⁺ and Cu²⁺ from various samples using flame atomic absorption spectrometry. After extraction, the analytes were desorbed using 0.01 M ethylenediaminetetraacetic acid. The effects of various parameters were studied and optimized. Under optimized experimental conditions the linear dynamic ranges for Cu²⁺ and Pb²⁺ were 10‒900 and 30‒900 μg/L, respectively, with a preconcentration factor of 20. The detection limits of Cu²⁺ and Pb²⁺ were 4 and 11 μg/L, respectively, and relative standard deviations for eight determinations of 100 μg/L were 3.6 and 3.8% for Cu²⁺ and Pb²⁺, respectively. The method was successfully applied for determination of copper and lead in mushrooms, rice, tap water and refinery wastewater with good spike recoveries ranging between 95‒106%.

In the current study, we have developed a green water switchable liquid–liquid microextraction method for separation, preconcentration, and estimation of selenium concentration in the real samples. First time introducing the water switchable liquid–liquid microextraction method to determine the trace level selenium in different food and soft drink samples. Water switchable medium was formed by the reaction of diethylenetriamine base when exposed to uniformed pressure of carbon dioxide. After being exposed to carbon dioxide, water switchable medium reversibly exchanges in two separated aqueous and organic phases. Advantages of carbon dioxide uses are cheap, environmental friendly, non-accumulation, removable, and require the opaque materials for operating container. Water switchable phenomena occurred easily from low polarity to high polarity organic solvent. Experimental variables of the water switchable liquid–liquid microextraction (LLME) method were optimized into its optimum values such as pressure, pH, centrifugation speed, extraction time, and concentration of complexing agent. The certified reference material of Canada Lake Water (TMDA-53.3) and CS-M-3 Mushroom (Boletus edulis) was used for validation of the present water switchable LLME method. Enhancement factor and limit of detection were obtained 85.5 and 0.018 μg kg⁻¹, respectively. Developed green water switchable LLME method was successfully applied for assessment of total selenium in tomato, pumpkin seed, mushroom, garlic, rice, pistachio, chickpea, hazelnut, walnut, apple juice, and ice tea samples.