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An in-situ CO₂-assisted dispersive micro solid phase extraction was developed using a covalent organic framework synthesized from melamine and barbituric acid as a sorbent for the extraction of Cd(II) and Zn(II) ions from honey samples. The structural and morphological characteristics of the sorbent were evaluated using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The CO₂ generated by reacting tartaric acid and sodium hydrogen carbonate enabled rapid dispersion of the sorbent within the sample solution, ensuring optimal contact with the target ions. After adsorption, the dispersed sorbent particles were separated via centrifugation, followed by elution with diluted nitric acid solution to retrieve the extracted heavy metals from the sorbent surface. The analytes collected in the eluate were quantified via flame atomic absorption spectrometry. Key experimental parameters, including tartaric acid and sodium bicarbonate amounts, sorbent dosage, type and volume of elution solvent, temperature, salt addition, pH, complexing agent concentration, and centrifugation conditions were systematically optimized. The method demonstrated high sensitivity, with the limits of detection of 0.17 and 0.092 µg L − 1 and broad linear range spanning 0.5–100 and 0.25–100 µg L − 1 for Cd(II) and Zn(II) ions, respectively. Extraction recoveries of 97.2 and 95.5%, with relative standard deviations of 3.6 and 2.7% for Cd(II) and Zn(II) ions, respectively, were obtained. Validation using a certified reference material confirmed the method’s accuracy, and application of the method on honey samples demonstrated its practicality.

A simple, rapid and efficient method has been developed for the extraction, preconcentration and determination of copper, lead and zinc ions in water samples by air-assisted liquid–liquid microextraction coupled with graphite furnace atomic absorption spectrometry (GFAAS). In the proposed method, much less volume of an organic solvent (in the order of some µL) was used as the extraction solvent in the absence of disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was achieved by centrifugation and the enriched analytes in the sedimented phase were determined by GFAAS. Several variables potentially affecting the extraction efficiency were investigated and optimized. Calibration graphs were linear in the concentration range of 45.0–1100 ng L−1. Detection limits were in the range of 18.0–26.0 ng L−1. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method was successfully applied to determine the selected heavy metals in tap, surface and river water samples.

In the present work, a new microextraction technique, namely in situ-produced CO2-assisted dispersive liquid–liquid microextraction was introduced for the extraction and preconcentration of cobalt, nickel, and copper from aqueous samples followed by graphite furnace atomic absorption spectrometry detection. The proposed method relies on the CO2 gas produced due to a chemical reaction as the disperser agent instead of the disperser solvent used in the conventional dispersive liquid–liquid microextraction. Initially, a solid mixture of tartaric acid and sodium bicarbonate was placed in the bottom of a dry conical glass test tube. Then µL level of 1,1,2,2-tetrachloroethane as the extraction solvent was added into the tube. An aqueous solution of the analytes containing sodium diethyldithiocarbamate (as chelating agent) was transferred into the tube. The reaction between tartaric acid and sodium bicarbonate was immediately occurred, and the produced CO2 led to dispersion of the extraction solvent as tiny droplets into the sample which resulted in extraction of the analytes into the organic solvent. The cloudy solution was centrifuged, and the sedimented phase was analyzed by the instrumental analytical method. Under the optimum conditions, the calibration curves were linear in the ranges of 20–300, 20–200, and 15–250 ng L−1 for Co2+, Ni2+, and Cu2+, respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.3 to 4.6 and 4.5–5.6% for intra- and inter-day (n = 6, C = 50 ng L−1) precisions, respectively. Moreover, the detection limits and enrichment factors of the selected analytes were obtained in the ranges of 6.2–12 and 139–150 ng L−1, respectively. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method was successfully applied for the simultaneous analysis of the selected analytes in environmental water and fruit juice samples. The relative recoveries obtained for the analytes in the spiked samples were within in the range of 84–107%.

A new sample preparation method, cyclohexylamine-based heat-induced homogeneous liquid–liquid microextraction, has been developed for the extraction and preconcentration of Cd(II) and Zn(II) ions in edible oils followed by flame atomic absorption spectrometry determination. First, the analytes are extracted into an acidic solution (a balanced mixture of HNO3 and HCl). Second, they are preconcentrated via the microextraction method. Accordingly, cyclohexylamine (as a complexing agent and an extraction solvent) is added at µL-level into the obtained solution containing the analytes to form a homogeneous solution followed by the addition of sodium chloride. After manual shaking, the obtained solution is placed in a water bath thermostated at 60 °C. A cloudy solution because of the decrease in cyclohexylamine solubility in water at high temperature is formed. After centrifuging fine droplets of cyclohexylamine containing Cd(II) and Zn(II)—cyclohexylamine complexes are collected on the top of the aqueous phase. The preconcentrated analytes in the upper phase by use of flame atomic absorption spectrometry are analyzed and determined. Several variables possibly affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, the calibration curves were linear in the ranges of 10–300 and 2.5–200 µg kg− 1 for Cd(II) and Zn(II), respectively. Repeatability of the proposed method, expressed as relative standard deviation, was obtained 2.4 and 1.7% for Cd (II) and Zn(II), respectively. Moreover, the detection limits of the selected analytes were obtained 3.8 and 0.6 µg kg− 1 for Cd(II) and Zn(II), respectively.

We have developed a solvent-free and sensitive method for the identification and quantification of methamphetamine (MAMP), amphetamine (AMP) and ecstasy (MDMA) in human urine. It is based on the use of an inside-needle adsorption trap (INAT) and a molecularly imprinted polymer (MIP). The MAMP-MIP layer was coated on the internal surface of a hollow stainless steel needle, which was oxidized and silylated. It was used as the extraction needle. A model solution containing the drugs was slowly passed through the extraction needle. After adsorption of the analytes, the needle was directly transferred to the injector of a gas chromatograph, where the analytes were thermally desorbed, separated by GC, and detected with a flame ionization detector. The method does not require an extraction solvent, is fast and simple. The linear range of the calibration graphs are rather wide, and the limit of detection and the limit of quantification (LOQ) for MAMP are 12 and 40 ng mL −1 , respectively. The relative standard deviations (RSD%) for six repeated experiments (at 500 ng mL −1 of MAMP) is 4.9 %. The relative recoveries obtained for MAMP in spiked human urine samples are in the range of 81–93 %. Graphical Abstract Figure Typical chromatograms corresponding to the extraction of MAMP, AMP and MDMA in the optimum condition from human urine sample. Lower chromatogram (I) belong to non-spiked samples after extraction using MAMP-MIP coated needle and the other chromatograms, (II) and (III), are related to spiked samples with MAMP, AMP and MDMA (each 0.5 μg mL −1 ) and extraction using the NIP-coated needle and MAMP-MIP coated needle, respectively.

An inside-needle extraction method was developed through thermal polymerization of atrazine-molecularly imprinted polymer (MIP) on the internal surface of a stainless steel hollow needle, which was oxidized and silylated. The fabricated coating (MIP layer) for the needle was durable and showed very good chemical and thermal stability. It could be mounted on a glass syringe and be directly coupled with gas chromatographic (GC) systems. The parameters being effective on the coating and extraction processes, namely nature of oxidizing agent, silylation time, nature and amount of porogen, template-to-MIP components ratio, polymerization time and temperature, sample volume, flow rate, pH and ionic strength of the sample were investigated and optimized. The extraction needle showed high selectivity as well as a great extraction capacity for triazines. The extraction of atrazine, simazine, cyanazine, ametryn, prometryn and terbutryn using the fabricated extraction needle and followed by GC analysis resulted in detection limits of 2.6, 21, 24, 32, 38 and 42 ng mL−1, respectively. The fabricated needle proved to be applicable to the analysis of real samples by comparing the results obtained for non-spiked and spiked samples of grape juice, tap water and groundwater.

A monolithic solid-phase microextraction (SPME) fiber was fabricated based on a molecularly imprinted polymer which could be coupled with gas chromatography for extraction, pre-concentration and determination of methamphetamine (MAMP). Methacrylic acid, ethylene glycol dimethacrylate and MAMP play the roles of functional monomer, cross-linker and template, respectively. The effective factors influencing the polymerization and extraction procedures were investigated and will be detailed here. The fabricated fiber was firm, inexpensive, stable, selective and durable which gives it vital importance in SPME. Selectivity of the fabricated fiber in relation to the template in solution containing MAMP, related and unrelated compounds was also investigated. Under the optimum conditions, the calibration plot was linear in the range of 50–3,500 ng mL−1 (r2 = 0.997). The high extraction efficiency was obtained for MAMP giving a detection limit of 14 ng mL−1. The fabricated fiber was successfully applied to SPME of MAMP from human saliva samples followed by gas chromatography-flame ionization detector analysis.

In this study, a simple and rapid sample preparation method named liquid-nitrogen-induced homogeneous liquid–liquid microextraction has been developed for the extraction and pre-concentration of Co(II) and Ni(II) ions before their analysis by flame atomic absorption spectrometry. For this purpose, first, acetonitrile containing 8-hydroxyquinoline is added into a sample solution and the mixture is vortexed. As a result, a homogeneous solution is formed. Subsequently, the solution is cooled using liquid nitrogen for a few seconds. By this process, due to difference in the freezing point of acetonitrile and water, the homogeneous state is broken and the analytes (as oxinate complexes) are extracted into liquid acetonitrile phase collected on top of the frozen aqueous phase. The linear dynamic ranges obtained for Ni(II) and Co(II) were 1.0–30 and 0.50–20 μg L−1, respectively. The obtained limits of detection were 0.36 and 0.20 μg L−1 for Ni(II) and Co(II), respectively.

Liquid phase microextraction (LPME) enables analytes to be extracted with a few microliters of an organic solvent. LPME is a technique for sample preparation that is extremely simple, affordable and virtually a solvent-free. It can provide a high degree of selectivity and enrichment by eliminating carry-over between single runs. A variety of solvents are known for the extraction of the various analytes. These features have led to the development of techniques such as single drop microextraction, hollow fiber LPME, dispersive liquid-liquid microextraction, and others. LPME techniques have been applied to the analysis of pharmaceuticals, food, beverages, and pesticides. This review covers the history of LPME methods, and then gives a comprehensive collection of their application to the preconcentration and determination of pesticides in various matrices. Specific sections cover (a) sample treatment techniques in general, (b) single-drop microextraction, (c) extraction based on the use of ionic liquids, (d) solidified floating organic drop microextraction, and various other techniques. Contains 149 references. Figure This review covers the history of LPME methods, and then gives a comprehensive collection of their application to the preconcentration and determination of pesticides in various matrices. Specific sections cover sample treatment techniques in general, single-drop microextraction, extraction based on the use of ionic liquids, solidified floating organic drop microextraction, and various other techniques.

In this study, a simple, fast, green, and efficient extraction procedure based on a using of mixture of ibuprofen and choline chloride was developed to extract trace amounts of Cu(II) and Cd(II) ions from water and fruit juice samples. For this purpose, first, appropriate amounts of ibuprofen and choline chloride were mixed and after heating, a homogeneous liquid mixture was formed. The synthesized hydrophobic mixture was used to prepare an adsorbent for the extraction of the analytes from the samples. Then extracted analytes were enriched by a dispersive liquid–liquid microextraction method before their determination by flame atomic absorption spectrometry. To achieve the best possible results, the effect of various parameters on the extraction recoveries of the analytes was investigated. Under optimal experimental conditions, linear ranges of the calibration curves were in the ranges of 2.5–100 μg L −1 for Cd(II) and 0.50–75 μg L −1 for Cu(II). The obtained relative standard deviations ( n  = 6, C  = 10 and 25 μg L −1 of each cation) were in the ranges of 2.5–4.2%. Limits of quantifications of 0.50 and 2.5 µg L −1 were obtained for Cu(II) and Cd(II), respectively. Finally, the proposed method was successfully used for the determination of Cu(II) and Cd(II) ions in various water and fruit juice samples by providing high extraction recoveries in the range of 94–97% for Cu(II) and Cd(II), respectively.