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In the current study, a headspace micro solid–phase extraction was developed for extraction of 1,4–dioxane and 2–methyl–1,3–dioxolane from shampoo samples. After extraction, the quantities of analytes were determined using the large volume injection method followed by gas chromatography–flame ionization detector. Octadecylsilane, menthol: formic acid deep eutectic solvent, and 1,3–dioxane were used as adsorbent, eluent, and internal standard, respectively. Under optimum conditions, linear ranges for target analytes were from 0.30 to 5000 ng mL–1, and 0.43–5000 ng mL–1 with correlation coefficients ≥0.9972. The limits of detection were 0.08 and 0.11 ng mL–1 for 1,4–dioxane and 2–methyl–1,3–dioxolane, respectively. The limits of quantification were 0.28 and 0.43 ng mL–1 for 1,4–dioxane and 2–methyl–1,3–dioxolane, respectively. The intra– and inter–day precisions for target analytes at the spiked level of 25 ng mL–1 were ≤4.2%. The feasibility of the recommended procedure was successfully tested for the extraction and determination of 1,4–dioxane and 2–methyl–1,3–dioxolane in shampoo samples. The extraction recoveries were ranged from 89–90% with relative standard deviations less than 5.1%. The nature of the interactions between studied chemical species was investigated in the light of conceptual density functional theoretical calculations. As to conclude, it was seen that experimental observations are compatible with the theoretical explanations made according to “hard and soft (Lewis) acids and bases” Principle.

A novel solid phase extraction approach named homogenous dispersive solid phase extraction was introduced for the simultaneous extraction/preconcentration of four polycyclic aromatic hydrocarbons hydroxylated metabolites from urine samples. The method was done by dissolving a water-miscible organic polymer in urine and a homogenous phase was obtained. Then, by adding NaCl the sorbent was re-precipitated in the solution bulk as tiny particles and the analytes are adsorbed onto the sorbent. Hence, the sorbent was separated and the analytes on the surface of particles were separated by choline chloride: butyric acid deep eutectic solvent and determined by HPLC-FLD. The effective parameters were optimized by central composite design and the following conditions were obtained: sample solution pH, 4; polyvinylpyrrolidone amount, 63 mg; sodium chloride concentration, 20% w/v; and choline chloride:butyric acid deep eutectic solvent volume, 87 µL. After optimization, the method was validated and broad linear ranges and low limits of detection (14–28 ng/L) and quantification (49–96 ng/L) were obtained. Acceptable enrichment factors (85–109), extraction recoveries (74–96%), and adequate percision (RSDs ≤ 6.2%) were obtained. Finally, the introduced method was effectively applied for measurement of the studied chemical compounds in urine samples obtained from tobacco smokers.

A new microextraction procedure based on liquid-liquid microextraction using a deep eutectic solvent has been used for the extraction of three β-blockers (atenolol, propranolol, and metoprolol) from plasma samples. The enriched analytes were analyzed by gas chromatography-mass spectrometry. In this study, both of the microextraction and synthesis processes were accelerated by using microwave radiations. In this procedure, 5 mL diluted plasma sample was transferred into a glass test tube and it was mixed with 0.20 g tetramethylammonium chloride. Then 0.5 mL of dimethylformamide (as a co-disperser) was mixed with 610 µL alpha terpineol and the mixture was dispersed into the solution to form a homogenous solution. The tube was placed under microwave radiations for 1 min. By doing so, tetramethylammonium chloride-alpha terpineol deep eutectic solvent was formed in sample solution as tiny droplets and the analytes were extracted into them. Then the tube was cooled with tap water and centrifuged for 5 min at 5000 rpm. Finally 1 µL of the deep eutectic solvent was injected into the determination system. Low limits of detection (0.130–0.205 ng mL−1) and quantification (0.435–0.692 ng mL−1), high extraction recovery (72–86%), and good precision (relative standard deviation ≤ 5.3%) were obtained. The introduced method was effectively applied for determination of the β-blockers’ concentrations in plasma samples.

Here, an inexpensive, sensitive and convenient fluorescent probe is described for the sensing of miRNA-155 via Ce-doped boron nitride nanosheets (Ce-BNNSs) acting as both fluorophore and peroxidase-mimicking nanomaterial. Ce-BNNSs exhibit different affinity toward single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The miRNA target hybridization causes the probe detachment from the Ce-BNNSs surface. The nanosheets coupled with hydrogen peroxide (H2O2) can oxidize substrate o-phenylenediamine (OPD) to generate fluorescent 2,3-diaminophenazine(oxOPD) with the maximum emission at 562 nm. The OPD is colorless, while the oxOPD can display a yellowish color and a new characteristic absorption peak at 450 nm. Furthermore, oxOPD quenches the fluorescence of Ce-BNNSs via an inner filter effect. Utilizing the fluorescence intensity ratio F562/F447 as the signal readout, the ratiometric fluorescence method was established to the detection of miRNA-155. Several independent and corresponding experiments were investigated and optimized using response surface methodology (RSM) based on central composite design (CCD). As a result, this assay responded linearly to miRNA-155 from 0.1 to 70 nM with a detection limit of 50.0 pM under the optimal conditions. The developed probe was also successfully applied to serum samples for miRNA-155 detection.

An in-situ dispersive liquid–liquid microextraction and derivatization method based on deep eutectic solvent has been developed for the analysis of five short chain fatty acids (as model compounds) in different beverage samples prior to their determination by gas chromatography-flame ionization detection. In this method, 2-butanol was used as dispersive solvent derivatization reagent. For this purpose, the sample solution is transferred into a test tube and after dissolving sodium chloride in the solution, a suitable volume of HCl solution is added as catalyst. Thus, a mixture of 2-butanol and ethyl methyl ammonium chloride-carvacrol deep eutectic solvent (as an extraction solvent) is prepared and the mixture is quickly injected into the solution. The analytes are derivatized and extracted into the fine droplets of extracting agent, simultaneously. After centrifugation, an aliquot of the sedimented phase is injected into the separation system. Low limits of detection (0.89–6.6 µg L-1) and quantification (3.1–22.3 µg L-1) were obtained. Good repeatabilities with relative standard deviations ≤9.2% were obtained at the selected three concentrations. Also high enrichment factors, extraction recoveries, and enhancement factors were obtained within the ranges of 223–270, 76–92%, and 1074–1845, respectively. The developed method was successfully used in determination of the analytes in different beverage samples.

A solid phase extraction method has been reported based on a molecularly imprinted polymer combined with deep eutectic solvents-dispersive liquid–liquid microextraction characterized by gas chromatography–mass spectrometry for the extraction and quantification of valproic acid from exhaled breath condensate samples. First, the molecularly imprinted polymer was synthesized using a precipitation polymerization method with valproic acid as a template and then it was used as a sorbent for the analyte extraction. Next, the adsorbed analyte was eluted from the sorbent using a water-miscible deep eutectic solvent prepared from N,N-dimethyl ammonium chloride: propionic acid. After collecting the eluant, it was mixed with 8-hydroxyquinolin: dichloroacetic acid: pivalic acid deep eutectic solvent as an extraction solvent with the mixture applied in the sequential microextraction method. The method provided low limits of detection and quantification of 0.04 and 0.13 ng mL−1 as well as 0.08 and 0.26 ng mL−1 in deionized water and the exhaled breath condensate, respectively. The method had proper repeatability, accuracy, and stability expressed as relative standard deviations less than 4.9, 13, and 18%, respectively. The validated method was successfully performed on different exhaled breath condensate samples obtained from the patients who were under treatment with valproic acid.

In present work, a ball milling procedure has been used for chemical synthesis–free and facile preparation of magnetized polycaprolactone composite in which the natural iron oxide obtained from sand, which is easy–accessible and low cost, was used as the magnetic core. The prepared composite was employed for the extraction of some pesticides (diazinon, metalaxyl, oxadiazon, bromopropylate, and fenazaquin) from fruit juice and herbal distillate samples in the developed method named stirring–dependent magnetic dispersive solid phase extraction. In the following, a dispersive liquid–liquid microextraction method was done to enrich the extracted pesticides and obtain high sensitivity. To do the extraction procedure, a few mg of the composite is added into an aqueous phase containing the analytes and stirred at high rate. By this action the particles of composite are dispersed in whole parts of the sample solution and adsorb the analytes. After a few minutes the agitation is stopped and the composite particles are collected on the magnetic stir bar which is taken and eluted with methanol to desorb the analytes. Then the eluent is taken, mixed with 1,1,2-trichloroethane at µL–level, and rapidly injected into deionized water. The obtained cloudy solution is centrifuged and an aliquot of the sedimented phase containing the extracted analytes is injected into gas chromatography–flame ionization detection. Under optimized conditions, the introduced method provided high enrichment factors (2280–2840), and low limits of detection (0.10–0.25 ng mL−1) and quantification (0.34–0.83 ng mL−1).

An efficient, simple, rapid, and repeatable sample preparation method based on microwave-assisted solvent extraction combined with dispersive liquid–liquid microextraction using in situ synthesis of a deep eutectic solvent was developed for the extraction of some biogenic amines in canned tuna fish samples. In this procedure, one carboxylic acid group of hexanedioic acid is participated in formation of the deep eutectic solvent while the other one is used to form ion pair with the analytes. Initially the analytes are extracted into deionized water sample during microwave-assisted solvent extraction. After centrifugation deep eutectic solvent synthesis and the microextraction procedure are performed simultaneously in the supernatant phase. The enriched analytes are separated and determined by high performance liquid chromatography-diode array detection. The method provided low limits of detection and quantification in the ranges of 0.25–0.50 and 0.84–1.7 ng g−1, respectively. The method had a proper repeatability with relative standard deviation less than or equal to 12%. The validated method was successfully performed on different canned tuna fish samples obtained from different producers.

A new ferrofluid prepared from toner powder and deep eutectic solvent was used in air-assisted liquid-liquid microextraction procedure for extraction of sixteen polycyclic aromatic hydrocarbons from urine and saliva samples of tobacco smokers. In this work, initially, a water-immiscible deep eutectic solvent is synthesized by mixing choline chloride and stearic acid under mild conditions and used as a support solvent in the preparation of ferrofluid from toner powder. Then, a few microliters of the prepared ferrofluid is mixed with sample solution and dispersed in all parts of the solution by performing aspirating/dispersing cycles. To collect the ferrofluid, a magnet is deposited at the outside of the tube and the solution is discarded. The analytes in the collected phase are back-extracted into n-heptane and determined by gas chromatography–mass spectrometry. The validation parameters including limit of detection and quantification, stability, accuracy, linearity, selectivity, precision, enrichment factor, and extraction recovery were studied and the data showed that the method have low limits of detection (in the range of 6–21 ng L−1 in deionized water and 18–63 ng L−1 in saliva and urine samples, respectively) and quantification (in the range of 20–72 ng L−1 in deionized water and 60–216 ng L−1 in saliva and urine samples). Extraction recoveries and enrichment factors ranged from 61 to 84% and 305 to 420, respectively. Relative standard deviations of ≤9% for the extraction of 200 ng L−1of each analyte were obtained for intra– (n = 6) and inter–day (n = 6) precisions. Finally, urine and saliva samples of tobacco smokers were successfully analyzed using the proposed method.

The mobility, bioavailability and persistence of copper and zinc were investigated by comparing the effect of concentration and pH changes in step 2 BCR (European Community Bureau of Reference, now known as the Standards Measurements and Testing Program) sequential extraction procedure in shrimp aquaculture farm sludge from Selangor, Malaysia. The pseudototal metal contents of shrimp aquaculture sludge samples were determined following an aqua regia digestion. The metal content in the extracts was measured by flame atomic absorption spectrometry (AAS). The concentration of Zn was increased with the increase in the concentration of hydroxylammonium chloride from 0.1 M to 0.5 M, However, further increase in the concentration of reductant caused a significant reduction in released Zn. Zinc showed the highest release percentage for hydroxylammonium chloride 0.5 M with pH 1.5 (modified BCR sequential extraction scheme). In contrast, Cu showed the highest speciation percentage in step 2 when the unmodified sequential extraction procedure was used. Copper and zinc concentrations in this sludge, however, were not higher than the typical concentrations in soil, hence the use of this sludge as a fertilizer is suitable.

Influence of heavy metals was investigated by conducting various tests on the samples collected from aquaculture shrimp in Selangor, Malaysia. The concentration of heavy metals in the sludge and potential of mobility based on its association forms was studied. Two sequential extraction methods (five stages Tessier method and three steps BCR method) were used to determine the binding forms of the metals. From the analysis, Ca, Fe and Mn were found to be highest concentrated metals compared to Zn, Cu, Cr, Cd and Pb in aquaculture shrimp sludge. From the sequential extraction, Cd, Mn and Pb were mostly found in exchangeable/carbonate form, showed its susceptibility to be leached easily. Also Cu and Zn were extracted predominantly in oxidizable form. All metal concentrations (except Cd, Zn and Cu) were extracted to be higher in residual fraction in this method. The results of BCR method are totally similar to the five stages Tessier method. By comparing the percent of recovery, the BCR method was better than Tessier method. Nevertheless for both methods the percent of their recoveries were acceptable. For Pseudototal metal digestion, although the concentration of Cd is less than other heavy metals, it is very harmful as a fertilizer because Cd is one of the heavy metals that might be in the leaf or fruit of plants. Also for investigation of Ca in the sludge, this element was measured and high amounts of that show sludge is useful for growing of plant. The results of direct digestion of heavy metals show that with the control of Cd in this sludge we can use this sludge as fertilizer in soils for agriculture but it is better if it is used for fruitless plants.

A new kinetic spectrophotometric method was developed to determine nitrite using molybdosilicic acid blue (MSAB) as a color reagent. This method is simple, rapid, sensitive and selective for the determination of trace amounts of nitrite ion. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at λ max =810 nm. The fixed time method was used. The limit of detection was 0.004 ppm. The relative standard deviations for the determination of 0.06 and 0.30 ppm of nitrite were 3.0% ( n =6) and 1.3% ( n =10), respectively. Two linear calibration graphs were observed (0.02–0.1 and 0.1–1.0 ppm). The method was applied to the determination of nitrite in well and waste waters.