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Pesticides have been used on several fruits, vegetables and cereals to control harmful organisms in order to increase the quality of products; however, these substances cause serious health effects. Therefore, an accurate and sensitive analytical method should be developed for the determination of pesticides to evaluate their toxicity. In this study, an efficient microextraction strategy was applied to preconcentrate eight different selected pesticides from mixed fruit juice samples prior to gas chromatography-mass spectrometry detection. All significant parameters such as spraying number, extraction solvent type, sample volume and mixing type/period belonging to the developed extraction method were elaborately optimized to get low detection limits. After the optimization studies, system analytical performance studies were carried out and limit of detection (LOD) values varied from 0.04 μg /kg−1to 1.99 μg kg−1(mass based) for the selected analytes. Under the optimum experimental conditions, spiking recovery experiments were performed in the mixed fruit juice samples to evaluate the applicability and accuracy of the proposed method. The recovery results were recorded in the range of 81.4–123.5% with acceptable standard deviations by applying a matrix matching calibration strategy. The proposed analytical method can be used for the qualitative and quantitative determination of selected pesticides in the mixed fruit juice samples and can also be applied to other fruit juice samples using a matrix matching calibration strategy.

In this study, an analytical strategy was proposed for the determination of cobalt at trace levels by using a flame atomic absorption spectrophotometry (FAAS) system after magnetic hydrogel based dispersive solid phase extraction (MH-DSPE). Poly(vinyl alcohol) based magnetic hydrogels (PVA-MH) were synthesized easily, quickly, and cost effectively in the laboratory and used as an adsorbent material in the microextraction process. Under the optimum experimental conditions, the limit of detection (LOD) and limit of quantitation (LOQ) values were recorded as 4.2 and 14.1 μg L−1, respectively. To investigate the matrix effects on the analyte signal, spike experiments were performed using chamomile tea extracts and good recovery results were obtained between 85.7 and 113.8%. A 57.8-fold improvement was achieved in the detection power compared to that of a conventional FAAS system. The results obtained throughout all experimental studies demonstrated the applicability in addition to the accuracy of the method for the quantification of trace levels of cobalt with high accuracy in a chamomile tea matrix.

In this study, an accurate analytical method development for cobalt determination in urine samples was described. The method is based on the mass transfer of the target analytes to the organic phase from the aqueous phase by the dispersing extractant throughout the solution with the aid of CO2bubbles prior to sample measurement by using a slotted quartz tube flame atomic absorption spectrophotometer. An extractor (1-decanol) dropped effervescent tablet (anhydrous sodium carbonate and sodium dihydrogen phosphate dihydrate mixture) was used in order to separate/preconcentrate cobalt after complexation of cobalt ions in aqueous solution with the Schiff base ligand. The parameters affecting the extraction output such as complexing conditions (pH, ligand concentration, and volume) and extraction conditions (extraction solvent type and volume, extraction temperature, and heating duration, NaOH volume and mixing period) were optimized to lower the detection limit. The limit of detection and quantification values under optimized experimental and instrumental conditions were determined as 3.7 μg L−1and 12 μg L−1, respectively with high linearity with respect to the dynamic range between 15 and 300 μg L−1. The enhancement factor obtained with the developed method was calculated as 83 fold. The pretreatment process was applied to urine samples in order to test the convenience of the developed method in urine samples for the determination of cobalt at low levels. The high percentage recovery results of 96–97% for four different concentrations of spiked urine samples indicated the proposed method's sufficient sensitivity for analyte determination in such a complex matrix.

In this work, a novel, efficient, simple and green solid phase extraction (SPE) method based on a pipette tip filled with zirconium nanoparticles (Zr-NPs) was developed for the sensitive determination of cobalt in soil samples viaslotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS). Zirconium nanoparticles providing repeatable and reproducible signals of the analyte were synthesized viaa practical method and used as adsorbents. Extraction and preconcentration steps were performed in a customized pipette tip loaded with zirconium nanoparticles. All parameters having significant effects on the analyte signal (pH and volume of the buffer, amount of nanoparticles, type, concentration and volume of the eluent, sample volume and sample flow rate) and instrumental conditions were optimized to obtain the best experimental outcomes. Under the optimum conditions, the linear range of the developed method was found to be between 7.5 and 75 μg L−1with a correlation coefficient of 0.9998. The SPE method offered 56-fold enhancement in the detection power of FAAS with the limits of detection and quantification (LOD/LOQ) calculated as 2.2 and 7.2 μg L−1, respectively. The developed method was applied to soil samples in order to test both its applicability and accuracy for real samples. The percent recoveries obtained were in the range of 90–101%, indicating the method's accuracy and applicability for complex matrices such as soil samples.