Sensitive determination of amide herbicides in environmental water samples by a combination of solid-phase extraction and dispersive liquid-liquid microextraction prior to GC-MS

Hydrophilic and hydrophobic deep eutectic solvent-based extraction to determine parathion in cereals by digital image colorimetry integrated with smartphones

To determine parathion in cereals, hydrophilic and hydrophobic deep eutectic solvents (DESs) were used by digital image colorimetry with smartphones. In the solid-liquid extraction part, hydrophilic DESs were used as extractants to extract parathion from cereals. In the liquid-liquid microextraction part, hydrophobic DESs dissociated into terpineol and tetrabutylammonium bromide in situ. The dissociated hydrophilic tetrabutylammonium ions reacted with parathion extracted in hydrophilic DESs under alkaline conditions to produce a yellow product, which was extracted and concentrated by dispersed organic phase terpinol. Digital image colorimetry integrated with the use of a smartphone was used for quantitative analysis. The limit of detection and quantification were 0.003 mg kg^-1 and 0.01 mg kg^-1, respectively. The recoveries for parathion were 94.8-106.2% with a relative standard deviation less than 3.6%. The proposed method was applied to analyze parathion in cereal samples: the method has the potential to be applied to pesticide residue analysis in food products.

Carbon Nanotube-Supported Dummy Template Molecularly Imprinted Polymers for Selective Adsorption of Amide Herbicides in Aquatic Products

In this study, a carbon nanotube (CNTs)-supported dummy template molecularly imprinted polymer (DMIPs) material was synthesized and utilized for the detection of amide herbicides in aquatic products via matrix solid-phase dispersion technology (MSPD). The DMIPs material was characterized, and its adsorption kinetics and isotherm were determined, the adsorption model was established, and the selective adsorption coefficient was calculated. The extract parameters of the method were optimized and successfully employed for the separation, analysis and detection of real samples, with satisfactory detection limits and linear ranges obtained. By comparing with other methods, the CNTs@DMIPs combined with MSPD technology established in our study can effectively solve false negative problems caused by insufficient destructive force, using dummy template molecules can also address the issue of false positives caused by template molecule leakage in molecular imprinting. Overall, the method is appropriate for the separation and detection of endogenous substances from highly viscous and poorly dispersed samples and is used as a routine detection tool in the aquaculture industry.

Development of a MOF-based SPE method combined with GC-MS for simultaneous determination of alachlor, acetochlor and pretilachlor in field soil

In this work, a rapid, highly selective, reusable and effective method was developed for simultaneous determination of alachlor, acetochlor and pretilachlor in field soil by GC-MS coupled with MIL-101 based SPE. Main factors affecting the SPE by using MIL-101 were optimized. Moreover, by comparing with the other commercial materials such as C₁₈, PSA and Florisil, the MIL-101(Cr) exhibited excellent adsorption performance, which aimed at amide herbicides. On the other hand, method validation displayed excellent method performance, achieving good linearities with r² ≥ 0.9921, limits of detection between 0.25-0.45 μg kg^-1, enrichment factors ≥ 89, matrix effect in the range of ± 20%, recoveries between 86.3% and 102.4%, and RSD lower than 4.38%. The developed method was successfully applied to the determination of amide herbicides in soil taken from the wheat, corn and soybean field at different depths, where the concentration of alachlor, acetochlor and pretilachlor were in the range of 0.62-8.04 μg kg^-1. It was demonstrated that the more depth of soil, the lower of three amide herbicides. This finding could be proposed a novel method to detect the amide herbicides in the agriculture and food industry.

Recent advances in microextraction procedures for determination of amphetamines in biological samples

Amphetamine and its related derivatives have stimulant and hallucinogenic properties. Illegal use of these drugs is an increasing global problem resulting in significant public health and legal problems. Deaths have been reported after intake of these drugs due to overdose. It is important to determine the type and concentration of illicit drugs in biological samples. These compounds are found in complex matrices at low concentration levels. The microextraction techniques are dominant sample preparation procedure and they are widely accepted as the most labor-intensive part of the bioanalytical process. For this purpose, a survey of recent published advances in microextraction procedures for quantification of amphetamines in biological samples found in the different databases from 2008 to date will be conducted.

Sensitive and rapid determination of pyrethroids in human blood by gas chromatography-tandem mass spectrometry with ultrasound-assisted dispersive liquid-liquid microextraction

In this study, a sensitive and fast procedure of ultrasonic-assisted dispersive liquid-liquid microextraction (UADLLME) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) for the determination of major pyrethroid pesticides (permethrin, tetramethrin, bifenthrin, fenvalerate, flucythrinate, fluvalinate, fenpropathrin, deltamethrin, and cyhalothrin) in blood samples was developed. Response surface methodology (RSM) combined with Box-Behnken design (BBD) and ANOVA function was used to optimize key factors affecting the extraction efficiency of UADLLME procedure. Target compounds were analyzed by GC-MS/MS. Under the optimal conditions, good linearity (R2 >0.99) was achieved for all the analytes in the concentration range of 0.5 to 100 μg L-1 . The recoveries for spiked samples at 3 concentration levels were between 70.2 and 91.8%, with relative standard deviations (RSD) lower than 10%. Very low limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.01 to 0.1 μg L-1 and from 0.03 to 0.3 μg L-1 were achieved. This method was successfully applied to the determination of low concentration of pyrethroids in blood samples from real forensic cases. High sensitivity, fast determination, simplicity in operation, small sample volume, and low usage of organic solvents are the advantages of this method. This methodology is of important value for sensitive and quick determination of residue pesticides and metabolites, study of residue pesticides behavior in human body, as well as application in real forensic cases.

Multi-residue method for the determination of 16 recently used pesticides from various chemical groups in aqueous samples by using DI-SPME coupled with GC-MS

A simple and solvent-free multi-residue method has been optimized to determine 16 currently used pesticides from different chemical groups in aqueous samples. The extraction of analytes was carried out with direct immersion solid-phase microextraction (DI-SPME) and for the identification and quantitative determination gas chromatography coupled with mass spectrometry (GC-MS) was applied. Two commonly used adsorbent coatings have been applied and compared: 100 μm of polydimethylsiloxane (PDMS) and 85 μm of polyacrylate (PA). The method development parameters of DI-SPME, analyte desorption and GC-MS analysis have been outlined along with the final experimental conditions. When the optimum extraction conditions were applied (extraction time 60 min, 10% (w/v) NaCl solution, 45°C) the limits of detection (LODs) were in the range of 0.015-0.13 μgL(-1) and the relative standard deviations (RSDs) were between 1.9 and 9.6%. The developed analytical method was successfully applied to the analysis of natural water samples from the following sources: river, sea, canal and rain.

Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection

A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.