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The current study aimed to develop a robust, selective, and sensitive voltammetric method for hexavalent chromium (CrVI) at a chemically modified carbon paste electrode. For the preparation of the electrode, a micropipet tip was packed with modified carbon paste mainly consisting of graphite powder and diphenylcarbazone (5 + 1, w/w). Voltammetric mode, type of electrolyte, pH, volume of electrolytes, accumulation time, accumulation potential, and stirring rate were studied in detail. The current response was linearly dependent on the concentration of CrVI from 0.20 to 2.60 µmol/L. The reproducible results were obtained for replicate analyses (n = 11) of three proposed electrodes of the same composition with RSDs of

An innovative, rapid, and simple dual-dispersive liquid–liquid microextraction (DDLL-ME) approach was used to extract uranium from real samples for the first time. The main objective of this study was to disperse extraction solvent by using an air-agitated syringe system to overcome matrix effects and avoid dispersion of hazardous dispersive organic solvents by using heat. The DDLL-ME method consisted of two dispersive liquid–liquid extraction steps with chloroform as the extracting solvent. Uranium formed complexes with 4-(2-thiazolylazo) resorcinol in the aqueous phase and was extracted in extracting solvent (chloroform) after the first dispersive liquid–liquid process. Uranium was then back-extracted in the acidic aqueous phase in a second dispersive liquid–liquid process. Finally, uranium was determined by a spectrophotometric detection technique. The variables that played a key role in the proposed method were studied and optimized. The LOD and sensitivity enhancement factor for uranium were found to be 0.60 µg/L and 45, respectively, under optimized conditions. Calibration graphs were found to be linear in the range of 5.0–600 µg/L. The RSD was 2.5%. Reliability of the proposed method was verified by analyzing certified reference material TM-28.3.

A simple vortex-assisted modified dispersive liquid-liquid microextraction procedure is proposed for the enrichment of cadmium (Cd+2) in surface (stored rainwater) and groundwater of the Tharparkar district in Pakistan, before analysis by flame atomic absorption spectrometry. Ammonium pyrrolidinedithiocarbamate was used as a ligand to make a hydrophobic complex of Cd+2, which was extracted in an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and the nonionic surfactant Triton X-114 was applied as a dispersing medium. The contents of tubes were shaken for different time intervals on a vortex mixer to enhance extraction efficiency. A multivariate strategy was used to simultaneously evaluate seven factors including, concentration of the complexing reagent, pH, amounts of ionic liquid and Triton X-114, vortex shaking time, centrifugation time and extracting solution for their influence on the percentage recovery of the analyte. The important variables were further optimized by central composite design. The preconcentration factor and LOD were observed as 76.9 and 0.048 µg/L, respectively. The Certified Reference Material SRM1643e was used to check the validity of the developed method, and the RSD was found to be 4.02%. The proposed technique was successfully applied for the enrichment of Cd+2 in groundwater and surface water samples from the southeastern part of Pakistan. The observed results revealed that the concentration of Cd+2 in groundwater was higher than the World Health Organization recommended value of 3 µg/L for drinking water. For adults weighing approximately 60 kg, consumption of groundwater for drinking and other domestic purposes would provide levels of Cd+2 that are 2- to 3-fold higher than the provisional maximum tolerable daily intake.

In the present study, a simple ultrasonically dispersed modified liquid-phase microextraction method was developed for the extraction of lead (Pb) from blood and scalp hair samples of malnourished children (MNC). The complexation of Pb was executed by means of the complexing agent, ammonium pyrrolidinedithiocarbamate (APDC), whereas extraction was carried out through the ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate. Ultrasound energy was used for the dispersion and extraction of the metal complex into an IL because it enhances the extraction of the metal complex into infinite IL drops at a temperature range of 40-80°C for 1-5 min. After sonication, the enriched analyte phase was separated by centrifugation. Nitric acid (HNO3; 0.5-2 mol/L) was added to the IL-enriched phase to back-extract the analyte into the acidic aqueous phase and analyzed by flame atomic absorption spectrometry. Various experimental parameters that affect the efficiency of the proposed method, such as volume of IL, concentration of the complexing agent, pH, ultrasonication time and temperature, and concentration of HNO3, were optimized. The enhancement factor was calculated as 70. The LOD for Pb ions was found to be 0.19 μg/L, with an RSD of

A new simple, selective, and economical preconcentration method was developed for the determination of Cd, Pb, and Ni in poultry antibiotics and supplements. The proposed preconcentration procedure is based on SPE using 8-hydroxyquinoline and Amberlite IRC-50 resin as complex and adsorbent, respectively. The determination was carried out by microsample injection system (MIS) flame atomic absorption spectroscopy (FAAS). Several analytical parameters were examined, including pH, type of resin, amount of resin, type of eluent, eluent volume, flow rate, sample volume, and interference of diverse ions. Under optimum experimental conditions, LODs and LOQs were 0.017 and 0.055, 0.016 and 0.53, and 0.074 and 0.248 μg/L for Cd, Pb, and Ni, respectively, with RSDs < 2.50%. The accuracy of SPE-MIS-FAAS was successfully tested by the standard addition method, with obtained recoveries >99%. The proposed method was successfully applied for the determination of Cd, Pb, and Ni in poultry supplement and antibiotic samples.

Supramolecular solvent–based dispersive liquid–liquid microextraction was used as a preconcentration method for the determination of trace levels of Hg. This simple method accurately measured oxidized HgII content inclaystone and sandstone samples obtained from the Thar Coalfield in Pakistan. Cold vapor atomic absorption spectrometry was used as the detection technique because it is reliable and accurate. The HgII in acidic media forms a complexwith dithizone (DTz) in the presence of supramolecular solvent (tetrahydrofuran and 1-undecanol), forming reverse micelles. Formation of the Hg-DTz complex was achieved to increase the interactions with the supramolecular solvent phase at pH 2.5 under the optimized experimental conditions. After additionof the supramolecular solvent to the aqueous solution, the micelles were uniformly mixed using a vortex mixer. The cloudy solution was centrifuged, and the Hg-DTz complex was extracted into the supramolecular solvent phase. Under optimized experimental conditions, the LOD and enrichment factor were foundto be 5.61 ng/L and 77.8, respectively. Accuracy of the developed method was checked with Certified Reference Materials. The developed method was successfully applied for the determination of HgII in claystone and sandstone samples from the Block VII and Block VIII areas of the Thar Coalfield on the basis of depth.

A simple, robust, and novel analytical procedure was developed for determination of total chromium (Cr) by carrier element coprecipitation (CECP) coupled microsample injection system with flame atomic absorption spectrometry. For this method, Cr(III) was oxidized by Ce(SO4)2 in acidic media, and the resulting solution formed coprecipitates with ammonium pyrrolidine dithiocarbamate in the presence of Ce(III). The effective parameters of the developed method have been optimized and studied in detail. The LOD and enrichment factor of CECP were 2.13 μg/L and 100 ± 2.8, respectively, with 40 mL initial volumes. The RSD values (n = 6) were 96%). The accuracy of total Cr by CECP after microwave acid digestion was checked by using a certified reference material (GBW 07309 Stream Sediment). The difference between the found and certified values was not significant (P > 0.05). The proposed method was successfully applied to natural drinking water, industrial effluent wastewater, and the exchangeable fraction of garden soil from Denizli, Turkey.

A rapid, simple, selective, economical, and sensitive dispersive liquid-liquid microextraction methodology has been established for the preconcentration of copper (Cu) at trace levels. The Cu(II) was complexed with 1-(2-pyridylazo)-2-naphthol; ethanol and carbon tetrachloride were used as disperser and extraction solvents, respectively. To obtain quantitative recovery of Cu(II), the effects of parameters influencing its extraction efficiency and subsequent determinations, i.e., pH, amount of complexing reagent, extraction time, and type and volume of disperser and extraction solvents, were examined. LOD and LOQ were 0.06 and 0.20 μg/L, respectively. The enrichment factor of the proposed method was 60, and the RSD

A method has been developed for the determination of arsenic (As) in pharmaceutical and scalp hair samples of kidney failure patients by cloud point extraction (CPE). The scalp hair samples were subjected to microwave-assisted digestion in nitric acid–hydrogen peroxide (2 + 1, v/v). Then, dialysate and digested scalp hair solutions were preconcentrated by CPE using pyronine B as a complexing agent. The resulting complex was entrapped in nonionic surfactant (Triton X-114) prior to its determination by electrothermal atomic absorption spectroscopy. The validity of the CPE method for As was checked by analysis of a certified reference material of human hair and a standard addition method for dialysate solution. The chemical variables affecting the analytical performance of the CPE methods were studied and optimized. After optimization of the complexation and extraction conditions, a preconcentration factor of 52 was obtained for As in 10 mL of dialysate solution and acid digested samples of scalp hair. Under the optimum experimental conditions, the LOD and LOQ of As for the preconcentration of 10 mL of solution were 0.022 and 0.073 μg/L, respectively. The level of As in scalp hair samples of kidney failure patients was higher than in healthy controls.

A simple and rapid cloud point extraction (CPE) procedure was applied for preconcentration of trace quantities of arsenic (As) in scalp hair samples. The samples were subjected to microwave-assisted digestion in a mixture of nitric acid and hydrogen peroxide (2 + 1, v/v) prior to preconcentration by CPE. The As in digested samples was complexed with ammonium pyrrolidine dithiocarbamate (APDC), and the resultant As-PDC complex was extracted by a nonionic surfactant, octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol and analyzed by electrothermal atomic absorption spectrometry. The experimental parameters, i.e., amount of APDC, concentration of Triton X-114, equilibrium temperature and time, were optimized. For validation of the proposed method, a certified reference material (CRM) of human hair (BCR 397) was used. No significant difference (P>0.05) was observed between the experimental results and certified values of the CRM (paired t-test). The LOD and LOQ obtained under the optimal conditions were 0.025 and 0.083 μg/kg, respectively. The developed method was applied for the determination of As in scalp hair samples from male and female subjects of two villages of Khairpur Mir's, Pakistan.

The development of 3 different ultrasonic-based sample treatment methods, ultrasonic probe-assisted acid extraction, ultrasonic-assisted acid slurry, and ultrasonic-assisted acid pseudodigestion is presented. These methods were compared for the determination of Cd and Pb by electrothermal atomic absorption spectrometry in biological samples (blood and scalp hair) and validated by using certified materials BCR 397 human hair and BCR 185R bovine liver. The sample amounts chosen to perform the analysis were 100 mg and 0.5 mL for solids (human hair and bovine liver) and blood samples, respectively. An acid digestion induced by microwave energy was used to obtain the total metal concentrations and for comparative purposes. The best results were obtained with the ultrasonic-assisted acid pseudodigestion, with which it was possible to perform accurate and precise determination of the Cd and Pb contents in 2 certified reference materials and biological samples of 50 normal males of ages 2540 years. The precision of the methods, together with their efficiency, rapidity, low cost, and environmental acceptability, make them good alternatives for the determination of trace metals from biological samples. The precision of the methods for accuracy evaluation, resulting in good agreement according to the t-test for a 95% confidence level, and the relative standard deviations were lower than 10% (n = 10) for all determinations.

A simple method for the preconcentration of cadmium (Cd) and nickel (Ni) in drinking and wastewater samples was developed. Cloud point extraction has been used for the preconcentration of both metals, after formation of complexes with 8-hydroxyquinoline (8-HQ) and extraction with the surfactant octylphenoxypolyethoxyethanol (Triton X-114). Dilution of the surfactant-rich phase with acidified ethanol was performed after phase separation, and the Cd and Ni contents were measured by flame atomic absorption spectrometry. The experimental variables, such as pH, amounts of reagents (8-HQ and Triton X-114), temperature, incubation time, and sample volume, were optimized. After optimization of the complexation and extraction conditions, enhancement factors of 80 and 61, with LOD values of 0.22 and 0.52 μg/L, were obtained for Cd and Ni, respectively. The proposed method was applied satisfactorily for the determination of both elements in drinking and wastewater samples.

A fast microwave-assisted extraction procedure was developed for the speciation of vanadium (V) species in soil samples collected from the vicinity of the Lakhra coal power plant (situated near a coal mining area) and industrial and agricultural areas. Soil samples were treated with two extracting reagents, (NH4)2HPO4 (0.2-1 M) and Na2CO3 (0.1-0.5 M), and heated by conventional and microwave methods for different time intervals to extract V+5 species. The V+4 and total V were extracted from filtration residue and the same subsamples of soil by treating with the acid mixture of HNO3-HCl-HClO4-H2SO4 (1:1:1:1, v/v/v/v). No significant difference between V+5 contents obtained by conventional heating and microwave-assisted extraction was observed (P = 0.485). The extraction efficiency of 0.6 M (NH4)2HPO4 for V+5 was lower (4-7%) than that obtained by 0.2 M Na2CO3 solution. The levels of V+5 were higher in soil samples collected from the vicinity of the Lakhra coal power plant and industrial areas, compared to those obtained from agricultural soil.

Advanced extraction methods have been developed for direct speciation of dissolved inorganic and organic selenium (Se) species in aqueous extracts of medicinal plants (MPs). The inorganic species of Se (SeIV and SeVI) were separated from organic forms by adsorbing inorganic Se on alumina, while the organic Se was not retained. The retained inorganic Se species was eluted with 10 mL 0.2 M HCl. The total inorganic Se species was determined after prereduction of SeVI into SeIV with concentrated HCl. The SeIV in the eluent and total inorganic Se species were then complexed with diethyldithiocarbamate. The resultant complexes were entrapped in the nonionic surfactant Triton X-114. The total Se, organic Se, total inorganic Se, and SeIV species were determined by electrothermal atomic absorption spectrometry with a modifer. The SeVI concentration was obtained by subtracting SeIV from total inorganic Se contents. The main factors affecting the methodologies were investigated in detail. Under the optimized experimental conditions, the LOD for SeIV was 50 µg/L. Among dissolved inorganic and organic Se species in aqueous extracts of MPs, organic Se species were present in the range of 74–84%, SeIV 3.62–7.47%, and SeVI 12.4–18.57% of total Se contents.

A simple and rapid microwave-assisted extraction (MAE) of selenium (Se) from medicinal plants was investigated using different concentrations of nitric acid and hydrochloric acid, sample mass, heating time, microwave energy, and plant particle size. The optimization strategy was carried out using multivariate methodologies. Electrothermal atomic absorption spectrometry was used to determine Se. The accuracy of the optimized procedure was evaluated by using certified reference materials with certified values for Se and a microwave-assisted acid digestion (MD) method for comparative purpose. No significant difference was observed (P > 0.05) when comparing the values obtained by the proposed MAE and MD methods (paired t-test). Under the optimum operating conditions, the LOD obtained from the standard calibration curve was 0.012 g/L for Se. The average RSD of the MAE method varied between 4.05 and 7.53 (n 6). The proposed method was successfully applied for the determination of Se in medicinal plants used as remedies for cancerous and infection diseases.

A simple and rapid ultrasound-assisted extraction procedure was developed for the determination of total mercury (Hg) in muscle tissues of freshwater fish species. A Plackett-Burman experimental design was used as a multivariate strategy for the evaluation of the effects of variables, such as presonication time (without ultrasonic stirring), sonication time, ultrasonic bath temperature, nitric acid concentration, hydrochloric acid concentration, and sample mass of muscle tissues. Some variables showed a significant effect on recovery, and they were further optimized by a 23 + star central composite design that involved 16 experiments. The validation was carried out by analysis of certified reference material DORM-2 (dog fish muscles); for comparative purposes, an acid digestion induced by microwave energy was used. Cold vapor atomic absorption spectrometry was used for the determination of total Hg. No significant differences were established between the analytical results and the certified values (paired t-test at P > 0.05). The LOD and LOQ of Hg were 0.133 and 0.445 g/kg, respectively, which demonstrated the high sensitivity of the proposed procedure for the determination of Hg at trace levels. The Hg concentrations in the muscle tissues of 10 freshwater fish species were found in the range of 35.367.8 g/kg on a dried basis, which were within the permissible limit of the World Health Organization.

A simple and fast procedure is proposed for the extraction of iron (Fe), copper (Cu), and nickel (Ni) in 16 varieties of sunflower seed oil samples using an ultrasonic bath. The experimental parameters of the ultrasonic-assisted extraction (UAE) method were optimized to improve the sensitivity and detect the metals at trace levels in minimum time. Conventional wet acid digestion method was used for comparative purposes. The optimum recovery of all 3 metals was obtained by UAE for 7 min, while the separation of aqueous and organic phases after extraction using centrifugation (UAE-2) required 3 min, as compared to the conventional equilibration method (UAE-1) that required 90 min. The respective recoveries of Cu, Fe, and Ni obtained with UAE-2 were in the range of 95.897.5, 93.598.3, and 95.698.2, respectively, for different varieties of sunflower oil samples. Accuracy was determined by the standard addition method. Under the optimum operating conditions, the limits of detection obtained from the standard addition curves were 21.7, 20.4, and 35.6 ng/mL for Fe, Cu, and Ni, respectively. The fact that all varieties of sunflower oil contain significant amounts of Fe, Cu, and Ni indicates the deterioration of sunflower oil quality immediately after extraction from seeds, which poses a threat to oil quality and human health.

A simple and rapid method based on ultrasound energy is described for the determination of aluminum (Al) in complex matrixes of chocolate and candy samples by electrothermal atomic absorption spectrometry. The optimization strategy was carried out using multivariate methodologies. Five variables (temperature of the ultrasonic bath; exposure time to ultrasound energy; volumes of 2 acid mixtures, HNO3H2SO4H2O2 (1 + 1 + 1) and HNO3H2O2 (1 + 1); and sample mass) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using fractional factorial and Doehlert matrix designs. Validation of the ultrasonic-assisted acid digestion procedure was performed against standard reference materials, milk powder (SRM 8435) and wheat flour (SRM 1567a). The proposed procedure allowed Al determination with a detection limit of 2.3 g/L (signal-to-noise = 3) and a precision, calculated as relative standard deviation, of 2.2 for a set of 10 measurements of certified samples. The recovery of Al by the proposed procedure was close to 100, and no significant difference at the 95 confidence level was found between determined and certified values of Al. The proposed procedure was applied to the determination of Al in chocolate and candy samples. The results indicated that cocoa-based chocolates have higher contents of Al than milkand sugar-based chocolates and candies.

A simple and efficient procedure for the determination of arsenic (As), cadmium (Cd), and lead (Pb) in the edible parts of freshwater fish by ultrasonic-assisted acid pseudodigestion (USD) was developed. A Plackett-Burman experimental design was used as a multivariate strategy for the evaluation of the effects of several variables at once. Five variablessonication time, sample mass of muscle tissue, temperature of the ultrasonic bath, mL of nitric acid, and mL of a mixture of acid and oxidantwere regarded as factors. From these studies, certain variables showed up as significant, and they were optimized by a 23+star central composite design, which involved 16 experiments. Optimum values of the variables were selected for the development of USD to determine the contents of As, Cd, and Pb in fish muscles used as pollution bioindicators from Lake Manchar (Sindh, Pakistan). The determination of the 3 toxic metals under study was performed by electrothermal atomic absorption spectrometry. The accuracy of the optimized procedure was evaluated by analysis of certified reference materials BCR 185R bovine liver and by comparison with conventional wet acid digestion methodology. The result obtained by the optimized method showed good agreement with the certified values and sufficiently high recovery. No significant differences were observed for P = 0.05. Relative standard deviation values (average of 10 separate determinations) were 1.21, 5.52, and 5.32% for As, Cd, and Pb, respectively.