Solid-phase Extraction Conditions Research Articles

Amphetamine-type stimulants analysis in oral fluid based on molecularly imprinting extraction

A methamphetamine-based molecularly imprinted polymer (MIP) has been prepared by bulk polymerization to recognize new psychoactive substances (NPS) of the amphetamine, cathinones and 2C families in oral fluid samples, being the first precedent of a synthetized MIP for the extraction and preconcentration 32 NPS including amphetamine type substances and synthetic cathinones from oral fluids. Pre-polymerization complex and resulting materials were appropriately characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption isotherms. Appropriateness of the material for the specific recognition of the target analytes was also evaluated through computational calculations and experimentally assessed by solid phase extraction (SPE). The most appropriate SPE conditions were evaluated and recoveries of 32 different NPS were obtained, ranging from 80 to 120% with a relative standard deviation (RSD) in all cases lower than 12%. Amphetamine-related NPS were analyzed by a fast and portable methodology based on ion mobility spectrometry (IMS) and a rearguard procedure based on ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) providing limit of detection values from 10 to 80 μg L−1 and from 0.03 to 1.3 μg L−1, respectively. Oral fluid samples, containing different interferents like caffeine, fluticasone and cetirizine, were spiked with 300 μg L−1 amphetamine and subsequently analyzed, showing recoveries ranging from 81 to 115% using both methodologies. Thus, this paper shows preliminary results to demonstrate the applicability of the developed procedure which could be used with minor modifications as screening technique in on-road drug analysis.

Dummy molecularly imprinted polymers based on a green synthesis strategy for magnetic solid-phase extraction of acrylamide in food samples

In this work, novel dummy molecularly imprinted polymers (DMIP) with propanamide as a dummy template molecule were prepared based on a green synthesis strategy of less consumption of hazardous/organic reagents and at mild conditions for magnetic solid-phase extraction (MSPE) of acrylamide in biscuit samples, followed by high performance liquid chromatography (HPLC) determination. The resultant DMIP was well characterized by FT-IR, SEM, TEM and VSM, exhibiting uniform nanoscale coreshell structure and good magnetic property in favor of simple rapid separation. Several main variables influencing MSPE efficiency were investigated, including DMIP dosage, sample solution pH, extraction time and desorption solvent; central composite design (CCD) and response surface methodology (RSM) were employed to assist in the MSPE condition optimization with rapidity and reliability. Under optimized conditions, excellent linearity for acrylamide was obtained in the range of 5.0–5000.0 µg kg−1, and low detection and quantification limits were 1.3 µg kg−1 and 4.4 µg kg−1, respectively. The method recoveries at five spiked concentrations were found within 86.0–98.3% with relative standard deviations (RSDs) of 1.2–4.1%. Furthermore, endogenous acrylamide was detected in five different biscuit samples and the RSDs values were lower than 3.3%. The present study suggested promising perspectives of water-compatible eco-friendly DMIP based MSPE-HPLC method for highly effective sample pretreatment and targeted analytes determination in complicated matrices.

Mixed-mode solid phase extraction combined with LC-MS/MS for determination of empagliflozin and linagliptin in human plasma

A selective, sensitive, precise and accurate liquid chromatography-tandem mass spectrometry method was developed and validated for the concurrent determination of antidiabetic drugs, empagliflozin and linagliptin in human plasma. Sample preparation was tested on several reversed-phase solid-phase extraction (SPE) sorbents with different chemistries like hydrophilic-lipophilic balance (Oasis HLB), mixed-mode cation exchange (Oasis MCX) and weak-cation exchange (Oasis WCX). SPE conditions like sample pH, washing and elution solvents were suitably optimized. Best results were obtained using Oasis MCX cartridges in terms of extraction recovery (78–88%) and matrix effects (~3.0%) for both the analytes. Chromatographic conditions for the separation of analytes and their labeled internal standards (ISs) were established on XSelect HSS Cyano (50 × 2.1 mm, 3.5 μm) column using 2 mM ammonium acetate buffer and acetonitrile as the mobile phase. Detection of analytes was achieved using electrospray ionization in the positive mode. For quantitative analysis, multiple reaction monitoring transitions were m/z 451.3 → 71.1 for empagliflozin and m/z 473.2 → 420.2 for linagliptin. Standard curve concentrations were validated in the range of 1.50–1500 ng/mL for empagliflozin and 0.015–15.0 ng/mL for linagliptin. The intra-batch and inter-batch precision (% CV) was <3.7 for both the drugs. The stability of the analytes established under different storage conditions was found to be appropriate for routine laboratory practices. The validated method was used to study the pharmacokinetics of the drugs using a single oral dose of fixed-dose combination tablet consisting of 25 mg empagliflozin and 5 mg linagliptin in healthy subjects.

Speciation analysis of chromium by carboxylic group functionalized mesoporous silica with inductively coupled plasma mass spectrometry

Carboxyl-group functionalized mesoporous silica (CFMS) prepared by one-pot co-condensation method was employed for the solid phase extraction (SPE) of chromium species for the first time. A new approach of SPE coupled to inductively coupled plasma mass spectrometry (ICP-MS) was thus established for the speciation of chromium in environmental water samples. The influences of pH, volume of sample, extraction time, amount of adsorbent, elution conditions, co-existing ions and adsorption capacity were investigated on adsorption or elution of chromium species. Cr(VI) was not retained on the CFMS material in the pH range of 1.0–9.0, while Cr(III) was quantitatively adsorbed at pH 5.0–9.0. The captured Cr(III) was enriched by using 1.5 mol L−1 HNO3 as elution solvent and detected by ICP-MS. Under the optimized SPE conditions, the maximum adsorption capacity of the CFMS for Cr(III) was 57.67 mg g−1 and the enrichment factor was 25, with the detection limit (LOD) of 0.02 μg L−1. The proposed protocol has been successfully applied to chromium speciation in rain, lake and river water samples, which exhibited a prospect in field separation and enrichment of chromium species in environmental waters.

Determination of antibiotics by SPE-LC-MS/MS in wastewater and risk assessment

In this study, conditions of solid phase extraction (SPE) for determination of some antibiotics such as trimethoprim, oxytetracycline, erythromycin, clarithromycin, azythromycin, doxycycline, sulfamethazine, ciprofloxacin, chlortetracycline, sulfamethoxazole in wastewaters were optimized. After the optimum volume and pH of the sample were determined, the effect of the concentration of the compounds and matrix were investigated. The highest recovery rates for antibiotic compounds were determined between 82% and 105% in 200 mL sample volume and pH 2.5. Then, antibiotic compounds were investigated in influent and effluent samples taken from Konya Urban Wastewater Treatment Plant. The concentration of the antibiotics was detected range of 0.11-101 ng/L in influent waters and less than dl-288 ng/L in effluent samples in wastewater treatment plant. Hazard quotients (HQs) of antibiotic compounds determined in WWTP effluents to evaluate the risk towards different aquatic organisms (algae, Daphnia magna and fish) were determined. Azythromycin for fish and erythromycin, sulfamethoxazole, ciprofloxacin, clarithromycin for algae posed a moderate risk while azythromycin, ciprofloxacin, clarithromycin, oxytetracycline posed a high risk for algae in the receiving environment.

Determination of Sulfamerazine in River Water Using Thermoresponsive Modified Silica for Solid-Phase Extraction with High-Performance Liquid Chromatography Detection

ABSTRACTFour thermoresponsive silica-poly(N-isopropylacrylamide-co-butyl methacrylate) materials were prepared by grafting (N-isopropylacrylamide-co-butyl methacrylate) at different ratios on multimodal porous silica via surface-initiated atom transfer radical polymerization. The thermoresponsive materials were employed as the adsorbent for the rapid determination of sulfamerazine in river water by solid-phase extraction. The properties of silica-poly(N-isopropylacrylamide-co-butyl methacrylate) were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Static adsorption measurements showed that the silica-poly(N-isopropylacrylamide-co-butyl methacrylate)3 material had the highest adsorption characteristics (8.72 mg g−1) at 35°C. The solid-phase extraction conditions were optimized, including the elution solvent and its volume used. The thermoresponsive silica-poly(N-isopropylacrylamide-co-butyl methacrylate)3 material provided satisfactory results for solid-phase extraction, with a recovery of 90.06%, allowing the rapid purification of sulfamerazine in river water.

Determination of Cobalt in Soils and Natural Waters Using Silica Gel Modified with Polyhexamethylene Guanidine and Nitroso-N-Salt

Highly sensitive and simple method was developed for preconcentration and determination of trace amounts of cobalt in natural waters and soils using diffuse reflectance spectroscopy was developed. Method is based on the application of the new sorbent – silica gel sequentially modified with polyhexamethylene guanidine and 2-nitroso1-naphthol-4-sulfonic acid sodium salt (nitroso-N-salt). Optimal conditions of solid-phase extraction of cobalt (II) such as stirring time, pH and volume of the solution, surface concentration of the reagent were determined. During sorption, intensively colored complex of cobalt (III) with nitroso-N-salt, that have a stripe in diffuse reflectance spectrum with maximum at 530 nm, was formed. Sorption-photometric method of cobalt determination directly in the sorbent phase by the color of its complex with nitroso-N-salt using diffuse reflectance spectroscopy was developed. The linearty of calibration curve depended on the surface concentration of nitroso-N-salt. For the surface concentration of nitroso-N-salt of 2.8 µmol g-1 the linearty was maintained in the concentration range of 0.05 – 5.0 µg Co per 0.100 g of the sorbent, or 0.005 – 0.50 µg mL-1 if the sorption was carried out from 10 mL of the solution. As the surface concentration of the reagent decreased, the range of linearty of the calibration curve narrowed. The detection limit was calculated as 0.01 μg per 0.100 g of the sorbent (or 1 ng mL-1 if the sorption was carried out from 10 mL of the solution) and didn’t depend on the surface concentration of the reagent. Method was applied to the determination of cobalt in natural waters and soils. The accuracy of the results was confirmed by inductively coupled plasma optical emission spectroscopy and recovery test of spiked samples.

Ternary mixed-mode silica sorbent of solid-phase extraction for determination of basic, neutral and acidic drugs in human serum.

In this study, a ternary mixed-mode silica sorbent (TMSS) with octamethylene, carboxyl, and amino groups was prepared via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction and a subsequent reduction of azide to primary amine. While used in solid-phase extraction (SPE), the retention behavior of TMSS towards a total of nine kinds of basic, neutral, and acidic drugs was investigated in detail. The results revealed that hydrophobic, ion-exchange interaction, and electrostatic repulsion between TMSS and the analytes were closely related to the retention behavior of TMSS. Besides, the log Kow value of the analyte was also a factor influencing the retention behavior of analytes on TMSS. The nine analytes could be retained by TMSS simultaneously and then, were eluted into two fractions according to the acid-base property of the analytes for further determinations. The acidic and neutral analytes were in one fraction, and the basic ones in the other fraction. When used to treat the human serum spiked with the nine drugs, TMSS offered higher recoveries than BakerBond CBA and comparable recoveries to Oasis WCX. It should be noted TMSS had better purifying capability for human serum than Oasis WCX. Under the optimized SPE conditions, a method of SPE hyphenated to high-performance liquid chromatography-ultraviolet detection (HPLC-UV) for determination of the basic, neutral, and acidic drugs spiked in human serum was established. For the nine drugs, the linear ranges were all between 5.0 and 1000μgL-1 with correlation coefficients (R2) above 0.9990, and the limits of detection (LODs) were in the range of 0.8-2.3μgL-1. The intra-day and inter-day relative standard deviations (RSDs) were less than 5.3 and 8.8%, respectively. Graphical abstract Treating drugs in human serum by SPE with ternary mixed-mode silica sorbent.

Analysis Study of Stevioside and Rebaudioside A from Stevia rebaudiana Bertoni by Normal Phase SPE and RP-HPLC

Solid Phase Extraction (SPE) method using silica as sorbent for stevioside and rebaudiosida A analysis in Stevia rebaudiana Bertoni leaf have not been performed. The aim of this study is to develop SPE method using silica as sorbent for Reverse Phase-High Performance Liquid Chromatography (RP-HPLC) analysis of stevioside and rebaudiosida A in S. rebaudiana leaf. The results of this study indicate that the optimal conditions for normal phase SPE (silica) are conditioned with 3.0 mL of hexane. The sample loading volume is 0.1 mL. Cartridge is eluted with 1.0 mL acetonitrile: water (80: 20, v/v) to separate both analytes. The cartridge is washed with chloroform and water of 0.3 mL respectively. The developed SPE sample preparation method meets the accuracy and precision test and can be used for the analysis of stevioside and rebaudioside A by RP-HPLC.

Determination of Methylamines and Methylamine- N -oxides in Particulate Matter Using Solid Phase Extraction Coupled with Ion Chromatography

Abstract Currently, the concentrations of methylamines in fine particulate matter (PM) are most often measured by aerosol time-of-flight mass spectrometry. A novel method for identification and determination of methylamines and methylamine-N-oxides in fine particles based on solid phase extraction (SPE) coupled with ion chromatography (IC) was developed. The experimental conditions including SPE conditions and chromatographic conditions were optimized. The quartz filter loaded with particulate matter (PM) samples was ultrasonically extracted with 20 mL of methanol and water (1:3, V/V) and the extraction process was repeated twice. After extraction, a total of 60 mL of extraction solvent was dropped into the extraction equipment for SPE. The Agilent AccuBond C18 was chosen for enriching the methylamine, dimethylamine, trimethylamine and trimethylamine-N-oxide in fine particles. Under the optimum conditions, the target species on Agilent AccuBond C18 were washed by 0.5 mL of acetonitrile solution and then concentrated (2 mL) before injecting into IC for analysis. A PRP X-200 (250 mm × 4 mm i.d.) was used for separation of analytes at 25 °C. The mobile phase was a mixture of 3% (V/V) acetonitrile solution and 5 mM nitric acid with the flow rate of 1 mL min–1. The four aliphatic amine species were fully resolved and completely separated within 30 min. The linearity of the four compounds ranged from 0.45 μg kg–1 to 1000 μg kg–1 with precisions of 2%–4% and detection limits of 0.002–0.003 μg m–3. The recoveries of the four aliphatic amine species in real PM samples were higher than 90%. This method was successfully applied in the analysis of real fine PM samples collected in Beijing. The concentrations of trimethylamine and methylamine-N-oxides were in the range of (0.01 ± 0.001) μg m–3–(0.08 ± 0.002) μg m–3 and (0.05 ± 0.001) μg m–3–(0.14 ± 0.002) μg m–3 for Beijing dust and haze PM samples, respectively.

Determination of Cobalt in Soils and Natural Waters Using Silica Gel Modified with Polyhexamethylene Guanidine and Nitroso-N-Salt

Highly sensitive and simple method was developed for preconcentration and determination of trace amounts of cobalt in natural waters and soils using diffuse reflectance spectroscopy was developed. Method is based on the application of the new sorbent – silica gel sequentially modified with polyhexamethylene guanidine and 2-nitroso1-naphthol-4-sulfonic acid sodium salt (nitroso-N-salt). Optimal conditions of solid-phase extraction of cobalt (II) such as stirring time, pH and volume of the solution, surface concentration of the reagent were determined. During sorption, intensively colored complex of cobalt (III) with nitroso-N-salt, that have a stripe in diffuse reflectance spectrum with maximum at 530 nm, was formed. Sorption-photometric method of cobalt determination directly in the sorbent phase by the color of its complex with nitroso-N-salt using diffuse reflectance spectroscopy was developed. The linearty of calibration curve depended on the surface concentration of nitroso-N-salt. For the surface concentration of nitroso-N-salt of 2.8 µmol g-1 the linearty was maintained in the concentration range of 0.05 – 5.0 µg Co per 0.100 g of the sorbent, or 0.005 – 0.50 µg mL-1 if the sorption was carried out from 10 mL of the solution. As the surface concentration of the reagent decreased, the range of linearty of the calibration curve narrowed. The detection limit was calculated as 0.01 μg per 0.100 g of the sorbent (or 1 ng mL-1 if the sorption was carried out from 10 mL of the solution) and didn’t depend on the surface concentration of the reagent. Method was applied to the determination of cobalt in natural waters and soils. The accuracy of the results was confirmed by inductively coupled plasma optical emission spectroscopy and recovery test of spiked samples.

Biosorbents based on pine sawdust and malt sprouts for preconcentration and ICP-OES determination of nonferrous, heavy, and precious metals in the environmental samples

ABSTRACTPine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.

A study of environmentally friendly recycling of technogenic chromium and nickel containing waste by the method of solid phase extraction

The study has revealed the regularities of the effect produced by increasing the content of scale of steel 12Cr18Ni10Ti in the charge from 5 to 75 mass % on the contents of the products of carbon thermal reduction of oxide waste of corrosion-resistant steels. The concentration of Ni is increased from 0.8 to 7.0 mass % when the Cr content ranges from 15.9 to 17.1 mass %. The concentration of Cr in the extraction products within the range of 16.1–17.1 mass% is provided with the content of scale of 95Cr18 steel in the charge in the range from 5 to 55 mass %. It has been found that metallization products mainly consist of a solid solution of alloying elements in α-Fe. Fe 3 O 4 , Fe 3 C, and Fe 2 C were also identified. The microstructure of the extraction products is spongy and disordered. The particles are sintered, with varying Cr and Ni contents in the ranges of 7.47 to 18.03 mass % and 2.97–10.40 mass %, respectively. The study has helped achieve environmentally safe conditions for solid-phase extraction of chrome and nickel containing industrial wastes from the production of corrosion-resistant steels with the return of the alloyed product to the welding industry

An improved method for the purification of milk oligosaccharides by graphitised carbon-solid phase extraction

Milk oligosaccharides (OS) are bioactive molecules that impart a variety of health benefits to the consumer. Techniques commonly used to analyse and quantify OS require optimised extraction methods to separate the OS from more abundant milk components. Solid phase extraction (SPE) is frequently used to isolate milk OS from lactose; however, the literature contains no formal studies on its efficacy in this application. In this study, established SPE conditions were modified to improve the technique's effectiveness in purifying OS from lactose. Low concentrations of acetonitrile (ACN) and trifluoroacetic acid (TFA) were tested for solid phase washing. Lactose removal and retention of many OS were significantly improved when using 4% ACN/0.1% TFA compared with the more common water washing technique. Different behaviours between acidic and neutral OS were evident. The new SPE technique improves extraction efficiency for bovine milk OS in applications that do not require prior lactose hydrolysis.

Pervasive Gabapentin Interference in the LC-MS/MS Analysis of Amphetamine.

An LC-MS/MS urine confirmation assay was developed using a "dilute and shoot" sample preparation method that was subject to interference arising from gabapentin column overload in approximately 4% of patient samples, leading to interference in amphetamine analysis. The initial analysis method used dilute and shoot sample preparation followed by LC-MS/MS analysis. The improved assay used solid-phase extraction sample preparation followed by LC-MS/MS analysis. The improved assay using solid-phase extraction and alternative chromatographic conditions resolved the gabapentin interference in amphetamine analysis. This experience illustrates the importance of thorough knowledge of likely comedications in a patient population and these drugs' elimination mechanisms. Laboratorians should be aware of the phenomenon of mass effect LC-MS/MS interference, in addition to the more common LC-MS/MS interferences caused by matrix effects and isobaric compounds.

Filter Plate–Based Screening of MIP SPE Materials for Capture of the Biomarker Pro-Gastrin-Releasing Peptide

Affinity-based solid-phase extraction (SPE) is an attractive low-cost sample preparation strategy for biomarker analysis. Molecularly imprinted polymers (MIPs) as affinity sorbents offer unique opportunities for affinity SPE, due to their low manufacturing cost and high robustness. A limitation is the prediction of their affinity; therefore, screening of analyte recovery and specificity within a large range of SPE conditions is important in order to ensure high-sensitivity detection and assay reproducibility. Here, a µ-SPE method for screening of the MIP-SPE materials using a commercial 384-well filter plate is presented. The method allows for rapid and automated screening using 10–30 µL of packed SPE sorbent per well and sample volumes in the range of 10–70 µL. This enables screening of many different SPE sorbents while simultaneously identifying optimal SPE conditions. In addition, the 384-well format also facilitates detection with a multitude of analytical platforms. Performance of the µ-MIP-SPE method was investigated using a series of MIPs designed to capture pro-gastrin-releasing peptide (ProGRP). Fractions coming from sample load, cartridge wash, and elution were collected and analyzed using mass spectrometry (MS). The top-performing MIPs were identified, together with proper SPE conditions.

Optimization of the Determination Method for Dissolved Cyanobacterial Toxin BMAA in Natural Water.

There is a serious dispute on the existence of β-N-methylamino-l-alanine (BMAA) in water, which is a neurotoxin that may cause amyotrophic lateral sclerosis/Parkinson's disease (ALS/PDC) and Alzheimer' disease. It is believed that a reliable and sensitive analytical method for the determination of BMAA is urgently required to resolve this dispute. In the present study, the solid phase extraction (SPE) procedure and the analytical method for dissolved BMAA in water were investigated and optimized. The results showed both derivatized and underivatized methods were qualified for the measurement of BMAA and its isomer in natural water, and the limit of detection and the precision of the two methods were comparable. Cartridge characteristics and SPE conditions could greatly affect the SPE performance, and the competition of natural organic matter is the primary factor causing the low recovery of BMAA, which was reduced from approximately 90% in pure water to 38.11% in natural water. The optimized SPE method for BMAA was a combination of rinsed SPE cartridges, controlled loading/elution rates and elution solution, evaporation at 55 °C, reconstitution of a solution mixture, and filtration by polyvinylidene fluoride membrane. This optimized method achieved > 88% recovery of BMAA in both algal solution and river water. The developed method can provide an efficient way to evaluate the actual concentration levels of BMAA in actual water environments and drinking water systems.

Sulfonated poly(styrene-divinylbenzene) modified with amines and the application for pipette-tip solid-phase extraction of carbendazim in apples.

Sulfonated poly(styrene-divinylbenzene) modified with five kinds of amine functional groups was applied to the determination of carbendazim in apple samples with a pipette-tip solid-phase extraction method. The structures of the polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Five different modifications of the solid-phase extraction sorbent based on sulfonated poly(styrene-divinylbenzene) were tested under static and pipette-tip solid-phase extraction conditions. The polymer modified with p-methoxyaniline showed the best recognition capacity and adsorption amount for carbendazim. Under the optimum conditions, 3.00mg of the adsorbent, 1.00mL of ethyl acetate as washing solvent, and 1.00mL of ammonia/acetonitrile (5:95, v/v) as elution solvent were used in the pretreatment procedure of apple samples. The calibration graphs of carbendazim in methanol were linear over 5.00-200.00 μg/mL, and the limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of carbendazim were in the range of 91.31-98.13% with associated intraday relative standard deviations of 0.76-2.13% and interday relative standard deviations of 1.10-1.85%. Sulfonated poly(styrene-divinylbenzene) modified with p-methoxyaniline showed satisfactory results (recovery: 97.96%) and potential for the rapid purification of carbendazim in apple samples combined with the pipette-tip solid-phase extraction.

Determination of MS-222 in Water Samples by Solid-phase Extraction Coupled with Liquid Chromatography/Tandem Mass Spectrometry.

A practical solid-phase extraction (SPE) method coupled with liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed for the determination of the fish anesthetic MS-222 in water. Water samples were concentrated and purified using three SPE cartridges of different specifications. Elution curves of MS-222 were constructed using various methanol-water solutions on the different cartridges, and SPE conditions were optimized in accordance with the elution curves. The mobile phase containing methanol and 0.1% formic acid solution with a linear gradient elution was utilized to separate MS-222 on a C18 column. Detection was carried out by a triple-quadrupole mass spectrometry with an electrospray ion source in positive mode. Recoveries of three MS-222 fortified levels of 0.05, 0.5 and 5 μg/L ranged of 82.6-101% with relative standard deviations (RSDs) below 9.36%. The limit of detection (LOD) and limit of quantification (LOQ) of MS-222 were 0.01 μg/L and 0.03 μg/L, respectively. This method was satisfactorily applied to the determination of MS-222 in actual water samples collected from aquatic product transportation vehicles or from the natural water catchments.

Detection of Organophosphorus Pesticide Residues in Leaf Lettuce and Cucumber Through Molecularly Imprinted Solid-Phase Extraction Coupled to Gas Chromatography

How to determine multipesticide residues in vegetables is important for the modern society. The development of a simple, rapid, and sensitive method to determine pesticide residues is significant. Our study used common vegetables—leaf lettuce and cucumber, and a new molecularly imprinted polymer (MIP) was synthesized using O,O′-dimethylthiophosphoryl chloride, an intermediate for the manufacture of organophosphorus pesticides, as the template, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The adsorption capacities of the prepared MIP toward five organophosphorus pesticides (trichlorfon, dichlorvos, dimethoate, imidacloprid, and methamidophos) were evaluated, and its potential as a sorbent for solid-phase extraction was investigated. A novel method for the simultaneous determination of multiple organophosphorus pesticide residues in vegetables was developed by utilizing molecularly imprinted solid-phase extraction (MISPE) coupled with gas chromatography. Under optimal solid-phase extraction conditions, with a flow rate of 3.0 mL/min for loading 100 mL, the enrichment factor was in the range of 36–452 for the five organophosphorus pesticides. The peak area precision of the five organophosphorus pesticides based on five replicates was from 1.59 to 4.07%. The leaf lettuce spiked sample was used to verify the fortified recovery for this method, and the results ranged from 87.48 to 97.85%. The MISPE–gas chromatography method could be used to detect organophosphorus pesticide residues in lettuce leaf and cucumber from the farmer’s market, and the detection limit had no obvious difference from the national standards. This method can meet the requirements of the analysis of pesticides in complex matrix.