Simultaneous determination of cyromazine,melamine and their biodegradation products by ion-pair high-performance liquid chromatography

An ion-pair high-performance liquid chromatography with ultraviolet detection method for the determination of cyromazine, melamine and its biodegradation products (ammeline, ammelide, cyanuric acid and biuret) was developed. C18 column was utilised to separate the six analytes with a mobile phase consisting of perchloric acid-ammonia solution and acetonitrile, under gradient elution and variable flow rate. The detection wavelengths were 205 nm for cyanuric acid and biuret and 222 nm for cyromazine, melamine, ammeline and ammelide. For analysis of sediment samples, the extraction solution containing acetonitrile, ammonia and water (80:10:10 by volume) was used to extract the analytes from sediment matrix. Using the extraction method for the spiked sediment sample, high linearity of matrix-matched standard curve could be obtained for the six analytes. The method detection limit was 0.1 μg g^?1 for melamine and cyromazine, 0.2 μg g^?1 for ammeline and ammelide, 1.2 μg g^?1 for cyanuric acid and 1.0 μg g^?1 for biuret in sediment matrix. The recoveries of these compounds were 70.1–98.3% and the relative standard deviations were 0.5–4.4%. Finally, the proposed method was successfully applied to the analysis of the sediment sample near the wastewater outlet of a melamine-producing factory.     

On-line Micro Solid-Phase Extraction of Clodinafop Propargyl from Water,Soil and Wheat Samples Using Electrospun Polyamide Nanofibers

An on-line extraction/determination set up was designed for micro solid-phase extraction of clodinafop propargyl from water, soil and wheat samples using electrospun polyamide nanofiber mats. The prepared mats were packed in a stainless steel tube which conveniently acted as a high-performance liquid chromatography injection loop. Influential parameters affecting the extraction efficiency were optimized using a distilled water sample fortified with 25 μg L^?1 of clodinafop propargyl. An enrichment factor of 440 was achieved for clodinafop propargyl indicating the ability of the whole procedure. Under the optimum conditions, the linearity for the analyte was in the range of 6–700 μg L^?1, while a limit of detection and limit of quantification of 2 and 6 μg L^?1 were achieved, respectively. The intra-day and inter-day RSD% at the concentration level of 25 μg L^?1 were 4.6 and 9.3 %, respectively. To investigate the matrix effect, the developed method was applied to the analysis of real water samples including paddy and river waters as well as the wheat and soil samples. The relative recovery percentages for the spiked samples were in the range of 63–95 %.     

Application of vortex-assisted supramolecular solvent liquid–liquid microextraction for trace determination of nitroaniline isomers

A novel, fast and efficient method for the analysis of nitroaniline isomers as model compounds was developed using vortex-assisted supramolecular solvent liquid–liquid microextraction (VA-SMS-LLME). A vortex mixer was used as the mixer in supramolecular solvent liquid–liquid microextraction, and it decreased the extraction time greatly. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, salt effect and extraction time, were optimised in detail. Under the optimal conditions, the enrichment factor was 133 for p-nitroaniline, 98 for m-nitroaniline and 115 for o-nitroaniline, and the limits of detection by HPLC were 0.3, 1.0 and 0.5 μg L^?1, respectively. Linearity with determination coefficient from 0.9981 to 0.9993 was evaluated using water samples spiked with the nitroanilines at fourteen different concentration ranging from 4 to 1000 μg L^?1. The ranges of intra-day and inter-day precision (n = 5) at 10 μg L^?1 of nitroanilines were 1.67–7.05% and 9.4–11.6%, respectively. The VA-SMS-LLME method was successfully applied for preconcentration of nitroanilines in environmental water samples.     

Analysis of PAHs in Water and Fruit Juice Samples by DLLME Combined with LC-Fluorescence Detection

A simple, rapid and efficient method termed dispersive liquid–liquid microextraction combined with liquid chromatography-fluorescence detection, has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in water and fruit juice samples. Parameters such as the kind and volume of extraction solvent and dispersive solvent, extraction time and salt effect were optimized. Under optimum conditions, the enrichment factors ranged from 296 to 462. The linear range was 0.01–100 μg L^?1 and limits of detection were 0.001–0.01 μg L^?1. The relative standard deviations (RSDs, for 5 μg L^?1 of PAHs) varied from 1.0 to 11.5% (n = 3). The relative recoveries of PAHs from tap, river, well and sea water samples at spiking level of 5 μg L^?1 were 82.6–117.1, 74.9–113.9, 77.0–122.4 and 86.1–119.3%, respectively. The relative recoveries of PAHs from grape and apple juice samples at spiking levels of 2.5 and 5 μg L^?1 were 80.8–114.7 and 88.9–123.0%, respectively. It is concluded that the proposed method can be successfully applied for determination of PAHs in water and fruit juice samples.     

Determination of reference interval values for inorganic elements in whole blood samples of humans and laboratory animals by X-ray fluorescence spectrometry

Inorganic elements are responsible for essential bodily functions, such as osmotic regulation, cardiac frequency and contractibility, blood clotting and neuromuscular excitability. The determination of inorganic elements in corporeal fluids such as blood, serum, plasma and urine is used as a monitor for a part or the whole organism; their values, then, are compared with reference interval values. In this study, the energy dispersive X-ray fluorescence spectrometry (EDXRF), applying the Fundamental Parameters method, for the determination of inorganic elements in whole blood samples from humans and laboratory animals, was used. Peripheral blood samples were collected and, before coagulation, 100 μL of sample were deposited onto Whatman No. 41 filter paper and dried, using infrared spotlight. The reference interval values for healthy Brazilian population of Na were found to be 1,788–1,826 μg g^?1, of Mg 63–75 μg g^?1, of P 602–676 μg g^?1, of S 1,519–1,718 μg g^?1, of Cl 2,743–2,867 μg g^?1, of K 1,508–1,630 μg g^?1, of Ca 214–228 μg g^?1, of Fe 170–184 μg g^?1, of Cu 4–6 μg g^?1 and of Zn 1–3 μg g^?1. The reference interval values for golden hamster (Mesocricetus auratus) of Na were found to be 1,714–1,819 μg g^?1, Mg 51–79 μg g^?1, P 970–1,080 μg g^?1, S 1,231–1,739 μg g^?1, Cl 2,775–2,865 μg g^?1, of K 1,968–2,248 μg g^?1, of Ca 209–257 μg g^?1, of Fe 145–267 μg g^?1, of Cu 4–6 μg g^?1 and of Zn 3–5 μg g^?1. A comparative study between EDXRF and instrumental neutron activation analysis data was carried out and the results for both techniques are statistically equal (α = 0.05). The results contribute for the establishment of reference interval values for Na, Mg, P, S, Cl, K, Ca, Cu and Zn in the healthy Brazilian population and the referred laboratory animal species.     

Development of a molecularly imprinted polymer-matrix solid-phase dispersion method for selective determination of β-estradiol as anabolic growth promoter in goat milk

A simple, fast, and sensitive method for determination of 17 β-estradiol (E2) in goat milk samples has been developed by combining selective molecularly imprinted matrix solid-phase dispersion (MIP–MSPD) and liquid chromatography with diode-array detection (DAD). The molecularly imprinted polymer was synthesized by use of 17β-estradiol as template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker monomer, azobisisobutyronitrile as initiator, and acetonitrile as porogen, and was used as selective solid support for matrix solid-phase dispersion. The selected dispersant had high affinity for E2 in the goat milk matrix and the extract obtained was sufficiently clean for direct injection for HPLC analysis without any interferences from the matrix. The proposed MIP–MSPD method was validated for linearity, precision, accuracy, decision limit (CCα) and detection capability (CCβ), in accordance with European Commission Decision 2002/657/EC criteria. Linearity ranged from 0.3–10 μg g^?1 (correlation coefficient r ²?>?0.999). Mean recovery of E2 from goat milk samples at different spiked levels was between 89.5 and 92.2%, with RSD values within 1.3–2%. CCα and CCβ values were 0.36 and 0.39 μg g^?1, respectively. The developed MIP–MSPD method was successfully applied to direct determination of E2 in goat milk samples.

Rapid Ultrasound-Assisted Emulsification Microextraction Combined with COU-2 Dispersive Micro-solid Phase Extraction for the Determination of Azole Antifungals in Milk Samples by HPLC-DAD

A rapid, simple, and efficient method using ultrasound-assisted emulsification microextraction combined with dispersive micro-solid phase extraction (USAE-D-µ-SPE) was developed for detection and quantification of three azole antifungals in milk samples by high-performance liquid chromatography diode array detector. In this study, mesoporous carbon, COU-2, was used as sorbent in USAE-D-µ-SPE for the extraction and preconcentration of analytes. Several important experimental parameters, including type of deproteinized solvents, desorption time, type of extraction solvents, volume of extraction solvent, extraction time, emulsification time, sample pH, salt addition, and mass of COU-2 sorbent, were optimized using spiked milk samples. Under the optimum extraction and detection conditions, three azole antifungals, namely ketoconazole, clotrimazole, and miconazole, were determined within 20 min, with good linearity of matrix-matched calibration in the range of 0.5–5000.0 µg L^?1 with coefficient of determination, r ² ≥ 0.9943. The method showed limits of detection and limits of quantification of all analytes in the range of 0.15–3.0 and 0.5–10.0 µg L^?1, respectively. Good repeatability with RSDs <15% (n = 3) and satisfactory relative recoveries (83.3–111.1%) were obtained for spiked azole antifungal drugs in milk. The results reveal that the developed USAE-D-µ-SPE method was a simple, rapid, efficient, environmentally friendly, and practicable method for the determination of azole antifungals in milk samples.     

Development of ultrasound-assisted emulsification solidified floating organic drop microextraction for determination of trace amounts of iron and copper in water, food and rock samples

A simple and efficient liquid-phase microextraction technique was developed using ultrasound-assisted emulsification solidified floating organic drop microextraction combined with flame atomic absorption spectrometry, for the extraction and determination of trace amounts of iron and copper in real samples. 2-Mercaptopyridine n-oxide was used as chelating agent and 1-dodecanol was selected as extraction solvent. The factors influencing the complex formation and extraction were optimized. Under optimum conditions, an enrichment factor of ~13 was obtained for both iron and copper from only 6.7 mL of aqueous phase. The analytical curves were linear between 40–800 and 20–1,200 μg L^?1 for iron and copper respectively. Based on three SD of the blank, the detection limits were 8.6 and 4.1 μg L^?1 for iron and copper respectively. The relative SDs for ten replicate measurements of 500 μg L^?1 of metal ions were 2.9 and 1.2 for iron and copper respectively. The proposed method was successfully applied for determination of iron and copper in environmental waters and some food samples including chess, rice, honey and powdered milk. Finally, method validation was made using rock certified reference material. A student’s t test indicated that there was no significant difference between experimental results and certified values.     

SPE then RP-LC for Simultaneous Analysis of Cyromazine and its Metabolite Melamine in Liquid Milk and Egg

Solid-phase extraction (SPE) and reversed-phase liquid chromatography (RP-LC) have been used for simple, sensitive simultaneous analysis of cyromazine and melamine residues in liquid milk and eggs. The conditions used for SPE and LC were investigated and optimized. A combined cation-exchange–reversed-phase cartridge was used for clean-up, and an ODS (C₁₈) column (150 mm × 4.6 mm i.d., 5-μm particles) with 62:38 (v/v) 5 mm sodium lauryl sulfate (pH 3.4)–acetonitrile as mobile phase was used for RP-LC. Under the optimum conditions the method limit of detection (LOD) for both cyromazine and melamine was 6.2 μg kg^?1 for liquid milk samples, and 11.5 μg kg^?1 for egg samples. Average recovery of cyromazine and melamine from milk samples was 90.3%, RSD 4.6–5.6%, and 99.6%, RSD 3.2–4.7%, respectively. Average recovery of cyromazine and melamine from egg samples was 85.3%, RSD 1.0–4.7%, and 89.6%, RSD 3.1–5.0%, respectively. The method enables detection of melamine and cyromazine at levels as low as 20.7 μg kg^?1 in liquid milk and 38.3 μg kg^?1 in egg.     

Use of a Headspace Solid-Phase Microextraction-Based Methodology Followed by Gas Chromatography–Tandem Mass Spectrometry for Pesticide Multiresidue Determination in Teas

This study reports on the development of a fast and efficient method based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–tandem mass spectrometry (GC–MS/MS) for simultaneous analysis of 128 volatile or semi-volatile pesticide residues belonging to nine classes of pesticides. The important factors related to HS-SPME performance were optimized; these factors include fiber types, water volume, ion strength, extraction temperature, and extraction time. The best extraction conditions include a PDMS/DVB fiber, and analytes were extracted at 90 °C for 60 min from 1 g of tea added to 5 mL of 0.2 g mL^?1 NaCl solution. The methodology was validated using tea samples spiked with pesticides at three concentration levels (10, 50, and 100 μg kg^?1). In green tea, oolong tea, black tea, and puer tea, 82.8, 88.3, 79.7, and 84.3% of the targeted pesticides meet recoveries ranging from 70 to 120% with a relative standard deviation of?≤?20%, respectively, when spiked at a level of 10 μg kg^?1. Limits of quantification in this method for most of the pesticides were 1 or 5 μg kg^?1, which are far below their maximum residue limits prescribed by EU. The optimized method was employed to analyze 30 commercial samples obtained from local markets; 17 pesticide residues were detected at concentrations of 2–452 μg kg^?1. Chlorpyrifos was the most detected pesticide in 80% of the samples, and the highest concentration of dicofol (452 μg kg^?1) was found in a puer tea. This is the first time to find that the optimized extraction temperature for pesticide residues is 90 °C, which is much higher than other reported HS-SPME extraction conditions in tea samples. This developed method could be used to screen over one hundred volatile or semi-volatile pesticide residues which belong to multiple classes in tea samples, and it is an accurate and reliable technique.     

Optimization of parameters for the alcoholic-assisted dispersive liquid–liquid microextraction of estrogens in water

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L^?1 for E2 and 0.1–100 μg L^?1 for E1. Limits of detection were 0.1 μg L^?1 for E2 and 0.01 μg L^?1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.     

Development of a new analytical method for Pb preconcentration and its further determination in water and foodstuffs using relatively low-sensitivity flame atomic absorption spectrometry

The present study describes chelation of Pb(II) with ascorbic acid and formation of a charge-transfer sensitive ion-pair in the presence of Rhodamine 6G at pH 5.5, and then its extraction to the micellar phase of non-ionic surfactant, PONPE 7.5 by an ultrasound-assisted cloud point extraction method before analysis by FAAS. The various variables affecting ion-pair formation and extraction efficiency were studied and optimised. Under the optimised conditions, the good linear relationships in the ranges of 0.4–150 μg L^?1 and 0.8–120 μg L^?1 for solvent-based calibration and matrix-matched calibration curves, respectively, were achieved with a pre-concentration factor of 71.4 from pre-concentration of 50-mL sample. Moreover, the limits of detection with good sensitivity enhancements of 124 and 114.5 were 0.13 and 0.24 μg L^?1, respectively, while the intra-day and inter-day precision (as RSD%, for five replicate measurements of 5 and 100 μg L^?1 in the same day and three succeed days) were in range of 2.8–5.4% and 3.7–6.3%, respectively. The matrix effect on triplicate determination of 50 µg L^?1 Pb(II) was also investigated. The accuracy of the method was statistically verified by the analysis of two certified reference materials (CRMs) after digestion with acid mixtures (HNO₃-H₂O₂-HF and HNO₃-H₂O₂) and dilution at suitable ratios. It has been observed that there is statistically not a significant difference between the certified- and found-values. The accuracy was also controlled using the pre-treated sample solutions spiked at different concentration levels, and the good spiked recoveries were obtained in range of 90–102.8%. The method was successfully applied to the determination of trace amounts of lead in water and food matrices with satisfactory results.     

Determination of Zn(II) in rock and vegetable samples after acidic digestion followed by ultrasound-assisted solid-phase extraction with reduced graphene oxide as novel sorbent,in combination with flame atomic absorption spectrometry

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using reduced graphene oxide (RGO) as sorbent was developed for the preconcentration of trace amounts of zinc (Zn) to its determination by flame atomic absorption spectrometry. Zinc could be adsorbed quantitatively on RGO in the pH range of 1–9, and then eluted completely with 0.5 mL of 0.1 mol L^?1 HCl. Some effective parameters on the extraction were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 0.2–15 μg L^?1 with a detection limit of 0.14 μg L^?1 with an enrichment factor of 100.12. The relative standard deviation for ten replicate measurements of 10 μg L^?1 of Zn was 0.58 %, respectively. The proposed method was successfully applied in the analysis of rock and vegetable samples. Good spiked recoveries over the range of 99.9–100 % were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.     

Determination of trace amounts of nystatin in water and vaccine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by high-performance liquid chromatography–ultraviolet detection

In this work, magnetic solid-phase extraction based on sodium dodecyl sulfate-coated Fe₃O₄ nanoparticles has been successfully applied for extraction and preconcentration of trace amounts of nystatin from water and vaccine samples prior to high-performance liquid chromatography–ultraviolet detection. Various experimental parameters affecting extraction and recovery of the analyte, such as the amount of sodium dodecyl sulfate, pH of the sample solution, salt concentration, extraction time, sample volume and desorption conditions, were systematically studied and optimized. Under optimized conditions, nystatin was quantitatively extracted. Proper linear range with good coefficient of determination, (R ² > 0.99) and limit of detection and quantification (based on signal-to-noise ratios of 3 and 10) of 2.0 and 5.0 µg L^?1, over the investigated concentration range (5–700 µg L^?1), were obtained, respectively. The intra-day and inter-day relative standard deviations at 50 µg L^?1 level of NYS were 1.4 and 4.5% based on six replicate determinations. The accuracy of the method was evaluated by recovery measurements on spiked samples. Suitable recoveries of 96–102 and 26–44% were achieved (at spiked levels of 50, 300 and 500 µg L^?1) for water and vaccine samples, respectively.     

Polyaniline/graphene oxide nanocomposite as a sorbent for extraction and determination of nicotine using headspace solid-phase microextraction and gas chromatography–flame ionization detector

A solid-phase microextraction fiber was prepared by polyaniline/graphene oxide nanocomposite as sorbent on the surface of a platinized stainless steel wire using electrospinning technique. The nanocomposite structure was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The polyaniline/graphene oxide nanocomposite fiber was used for the determination of nicotine from tobacco samples using headspace solid-phase microextraction method and gas chromatography–flame ionization detection. Influential experimental variables on the extraction efficiency of nicotine, such as extraction time and temperature, humidity and desorption conditions, were evaluated and optimized. Under the optimal experimental conditions? the limit of detection, linear dynamic range, intraday and inter-days precisions were found to be 0.01 μg g^?1, 0.05–700 µg g^?1 (R²?=?0.996), 6.9 and 8.1%, respectively. Comparison of the polyaniline/graphene oxide nanocomposite sorbent with polyaniline and commercial fibers shows longer durability, larger capacity and higher extraction efficiency. The polyaniline/graphene oxide nanocomposite fiber was successfully applied for the determination of nicotine in tobacco samples.     

Studies of total, organic and inorganic iodine in Canadian bovine milk samples with varying milk fat content using ion-exchange chromatography and neutron activation analysis

Chemical separation methods in conjunction with instrumental neutron activation analysis (INAA) were developed for measuring iodine levels in commercially available bovine milk with varying milk fat (MF) content. Samples of homogenized (3.25 % MF), partly skimmed (2 % MF), partly skimmed (1 % MF), partly skimmed calcium enriched (1 % MF + Ca), and skim (<0.05 %) milk were purchased from local supermarkets. Ion exchange chromatography, solvent extraction, and ammonium sulfate precipitation methods were applied to the separation of the inorganic, lipidic and proteic fractions of iodine in milk. The levels of iodine were measured by INAA in total reactor and epi-cadmium (EINAA) neutron flux in conjunction with conventional gamma-ray and Compton suppression spectrometry (CSS). A pseudo-cyclic INAA method coupled with CSS (PC-INAA-CSS) was also explored as an instrumental option to further lower the detection limit of iodine. The detection limits of 0.06, 0.06 and 0.02 μg mL^?1 for iodine were obtained using INAA-CSS, EINAA-CSS, and PC-INAA-CSS methods, respectively. Although the PC-INAA-CSS method provided the lowest detection limit, the INAA-CSS method was sufficient for the determination of total iodine in almost all samples analyzed in this work. The total iodine concentrations (μg mL^?1) were: 0.40 ± 0.01 (in 3.25 % MF), 0.40 ± 0.01 (2 % MF), 0.42 ± 0.01 (1 % MF), 0.42 ± 0.01 (<0.05 %), and 0.96 ± 0.01 (1 % MF + Ca) milk samples. Iodine bound to various fractions of the milk samples analyzed, in percent of total iodine content, ranged: (0.05–1.8), (1.9–4.8), (90–95) for the lipidic, proteic and anionic inorganic fractions respectively. Iodine recovery in all cases was higher than 96 %.     

Determination of Antimony(III) and Total Antimony in Aqueous Samples by Electrothermal Atomic Absorption Spectrometry After Dispersive Liquid–Liquid Microextraction (DLLME)

Dispersive liquid–liquid microextraction (DLLME) technique combined with electrothermal atomic absorption spectrometry (ET-AAS) was proposed for determination of antimony(III) and total antimony at very low concentrations in water samples. The N-benzoyl-N-phenylhydroxylamine (BPHA) was used as a chelating agent, and chloroform and ethanol were used as extraction and disperser solvents, respectively. The effect of various experimental parameters on the extraction and determination was investigated. The detection limits (3σ) were 0.005 μg L^?1 for Sb(III) and 0.008 μg L^?1 for total Sb. The developed method was applied successfully to the determination of Sb(III) and total Sb in natural water samples.     

Liquid–Liquid Microextraction of Nitrophenols Using Supramolecular Solvent and Their Determination by HPLC with UV Detection

A novel, efficient, and environmentally friendly method—supramolecular solvent liquid–liquid microextraction (SMS-LLME) combined with high-performance liquid chromatography (HPLC)—was first established for the determination of p-nitrophenol and o-nitrophenol in water samples. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, temperature, salt effect, extraction time, and stirring rate, were optimized in detail. Under the optimal conditions, the enrichment factor was 166 for p-nitrophenol and 160 for o-nitrophenol, and the limits of detection by HPLC were 0.26 and 0.58 μg L^?1, respectively. Excellent linearity with coefficients of correlation from 0.9996 to 0.9997 was observed in the concentration range of 2–1,000 μg L^?1. The ranges of intra- and interday precision (n = 5) at 100 μg L^?1 of nitrophenols were 5.85–7.76 and 10.2–11.9 %, respectively. The SMS-LLME method was successfully applied for preconcentration of nitrophenols in environmental water samples.     

MultiSimplex optimization of the dispersive solid-phase microextraction and determination of fenitrothion by magnetic molecularly imprinted polymer and high-performance liquid chromatography

A magnetic molecularly imprinted polymer (MMIP) was fabricated and used as the sorbent for the MMIP-dispersive solid-phase microextraction of fenitrothion prior its determination by high-performance liquid chromatography equipped with an ultraviolet detector. The MMIP was prepared using functionalized Fe₃O₄ nanoparticles as the magnetic supporter. Methacrylic acid, ethylene glycol dimethacrylate and fenitrothion were used as the functional monomer, the cross-linker and the template, respectively. The properties of the resultant MMIP were evaluated using X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The sorbent exhibited high selectivity and affinity toward fenitrothion compared to other organophosphate pesticides with the maximum adsorption capacity of 31.5 mg g^?1. The effective variables on the extraction were optimized by univariable and MultiSimplex methods. The calibration curve exhibited linearity over the concentration range of 0.3–50.0 μg L^?1 with the limit of detection of 0.1 μg L^?1. The relative standard deviations at 10.0 μg L^?1 level of FNT (n = 5) for intra- and inter-day assays were 1.6 and 3.1%, respectively. The proposed method was successfully used for the determination of trace amounts of FNT in food and water samples.     

Determination of Methadone in Biological Samples Using Liquid Phase Microextraction with Back Extraction Combined with LC

Liquid phase microextraction with back extraction (LPME-BE) combined with liquid chromatography-ultra violet (LC-UV) was applied for the extraction and determination of methadone in biological fluids. At the optimized conditions, an enrichment factor of 386 and detection limit (LOD) of 0.2 μg L^?1 were obtained. The calibration curve was linear (r ² = 0.989) in the concentration range of 0.6–1,000 μg L^?1. Within-day relative standard deviation RSD (S/N = 3) and between-day RSD were 2.7 and 5.9%, respectively. The feasibility of the proposed method was evaluated by extraction and determination of methadone in plasma and urine samples and satisfactory results were obtained.