Development of Immunoaffinity Sample-Purification for GC–MS Analysis of Ractopamine in Swine Tissue

A method combining immunoaffinity chromatography with gas chromatography–mass spectrometry (GC–MS) has been established for determination of ractopamine residues in swine liver and urine. After clean-up on an immunoaffinity chromatography column, GC–MS analysis revealed recovery from blank swine liver and urine fortified at 2.5–20 ng g^?1 (ng mL^?1 for urine), respectively, was 68.2–78.6 and 76.2–83.1%. The limits of detection and quantification were 0.5 ng g^?1 (or ng mL^?1) and 2.0 ng g^?1 (or ng mL^?1), respectively. The procedure was used for analysis of ractopamine residues in samples of swine liver and urine in which the levels were unknown. The amounts detected were 9–216 ng g^?1 (ng mL^?1).     

Synthesis and application of a novel magnetic nanosorbent for determination of trace Cd(II), Ni(II), Pb(II), and Zn(II) in environmental samples

In this work for the first time, Fe₃O₄@SiO₂ core–shell nanoparticles functionalized with isatin groups as a magnetic nanosorbent was applied for the simultaneous extraction of trace amounts of cadmium(II), nickel(II), lead(II), and zinc(II). The characterization of this nanosorbent was studied using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, vibrating sample magnetometer and thermogravimetric analysis. The effect of several factors such as pH, amount of sorbent, extraction time, type and volume of the eluent, sample volume, sorption capacity, and potentially interfering ions was investigated. In the selected conditions, it was observed that the limits of detection were 0.11 ng mL^?1 for Cd(II), 0.28 ng mL^?1 for Ni(II), 0.47 ng mL^?1 for Pb(II), and 0.21 ng mL^?1 for Zn(II), and the maximum sorption capacity of this suggested magnetic nanosorbent was 120, 112, 100, and 100 mg g^?1 for Cd(II), Ni(II), Pb(II), and Zn(II), respectively. Also, the precision of the method (RSD%) for ten replicate measurements was found 2.5, 2.5, 2.8, and 3.1%, for Cd(II), Ni(II), Pb(II), and Zn(II) ions, respectively. Finally, the suggested procedure was applied for determination of cadmium(II), nickel(II), lead(II), and zinc(II) at trace levels in different water and agricultural products with satisfactory results.     

Magnetic Nanoparticle-Based Micro-Solid Phase Extraction and GC�CMS Determination of Oxadiargyl in Aqueous Samples

A new facile, rapid, inexpensive, and sensitive method based on magnetic micro-solid phase extraction (M-??-SPE) coupled to gas chromatography?Cmass spectrometry (GC?CMS) was developed for determination of the herbicide oxadiargyl in environmental water samples. The feasibility of employing non-modified magnetic nanoparticles (MNPs) as sorbent was examined and applied to perform the extraction process. Influential parameters affecting the extraction efficiency along with desorption conditions were investigated and optimized. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) of the method under optimized conditions were 0.005 and 0.030 ng mL^?1, respectively. The relative standard deviations (RSD) (n = 3) at a concentration of 0.10 ng mL^?1 was 11%. The calibration curve of oxadiargyl showed linearity in the range of 0.050?C0.50 ng mL^?1. The developed method was successfully applied to the extraction of oxadiargyl from spiked tap water and Zayande-Rood River water samples and the relative recoveries of 98 and 94% were obtained, respectively.     

Solid phase extraction of heavy metal ions based on a novel functionalized magnetic multi-walled carbon nanotube composite with the aid of experimental design methodology

We report that magnetic multiwalled carbon nanotubes functionalized with 8-aminoquinoline can be applied to the preconcentration of Cd(II), Pb(II) and Ni(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH value) were selected as the main factors affecting sorption, and four variables (type, volume and concentration of the eluent; elution time) were selected for optimizing elution. Following sorption and elution, the ions were quantified by FAAS. The LODs are 0.09, 0.72, and 1.0 ng mL^?1 for Cd(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations are <5.1 % for five separate batch determinations at 30 ng mL^?1 level of Cd(II), Ni(II), and Pb(II) ions. The sorption capacities (in mg g^?1) of this new sorbent are 201 for Cd(II), 150 for Pb(II), and 172 Ni(II). The composite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Diphenyl diselenide grafted onto a Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-chitosan composite as a new nanosorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction

Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe₃O₄) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-μSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n?=?3) are as following: Pb(II): 2.0 ng·mL^?1; 6.3–900 ng·mL^?1; 1.5%. Cd(II): 0.15 ng·mL^?1; 0.7–85 ng·mL^?1, 3.2%; Ni(II): 1.6 ng·mL^?1,.6.0–600. ng·mL^?1, 4.1%; Cu(II): 1.2 ng·mL^?1, 3.0–300 ng·mL^?1, 2.2%. The nanosorbent can be reused at least 4 times.

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Graphical abstract Fe₃O₄-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

     

Simultaneous Determination of Gallium(III) and Indium(III) in Urine and Water Samples with Cloud Point Extraction and by Inductively Coupled Plasma Optical Emission Spectrometry

A simple, sensitive, and selective method for the determination of gallium and indium in different samples at trace levels is presented. This method was based on complexation of analyzes with 2-(5-bromo-2- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of t-octylphenoxy-polyethoxyethanol (Triton X-100). After phase separation, the analyzed concentrations were determined by inductively coupled plasma optical emission spectrometry. Quantitative extraction of gallium and indium was performed at pH 7.0, 1.7 mmol L^?1, 5-Br-PADAP, 1.3% (w/v) Triton X-100 and at 75°C. The relative standard deviations (RSD) of this method were between 0.3% and 1.6% (C = 20 ng mL^?1, n = 9). The calibration curve is linear over the concentration range 6–200 ng mL^?1 for gallium and 2–200 ng mL^?1 for indium, respectively. The limits of detection (LOD) for gallium and indium were 0.72 and 0.28 ng mL^?1, respectively. The results showed the developed method was not susceptible to matrix effects, providing recoveries between 98% and 102%. The accuracy of the developed method was evaluated by the analysis of spiked certified reference materials. The developed method was successfully applied to gallium and indium determination in urine and lake water with satisfactory results.     

FAAS determination of palladium after its selective recovery by silica modified with hydrazone derivative

Amino propyl silica (APS) gel reacts immediately with benzyl monopyridyl hydrazone (BMPH) to produce a new effective and selective derivative (BMPH-APS) for the separation and preconcentration of traces of Pd(II) in aqueous solution. Factors affecting the sorption and desorption of Pd ions have been investigated. Acidic aqueous solution of 0.5% thiourea in 0.5 mol L^?1 HCl has been used as eluent for the desorption of Pd(II). The stripped metal ion was determined by flame AAS. The modified silica quantitatively sorbed Pd(II) at pH 2–4 with a sorption capacity of 0.65 mmol g^?1 and preconcentration factor of 250 fold in less than one minute (t_1/2). Common other ions did not interfere except Co(II) which was eliminated by EDTA . The limit of detection (LOD) is 0.1 ng mL^?1 and the relative standard deviation (R. S. D.) for 10 replicate measurements at 20 ng mL^?1 Pd level was 1.51%. The method was successfully applied for Pd preconcentration in highly concentrated salt solutions and in spiked clay, road dust, scrap and water samples.     

Micro-solid phase extraction of ochratoxin A, and its determination in urine using capillary electrophoresis

We describe a simple, environmentally friendly and selective technique for the determination of ochratoxin A (OTA) in urine. It involves (a) the use of a molecularly imprinted polymer as a sorbent in micro-solid-phase extraction in which the sorbent is contained in a propylene membrane envelope, and (b) separation and detection by capillary electrophoresis (CE). Under optimized conditions, response is linear in the range between 50 and 300 ng mL^?1 (with a correlation coefficient of 0.9989), relative standard deviations range from 4 to 8 %, the detection limit for OTA in urine is 11.2 ng mL^?1 (with a quantification limits of 32.5 ng mL^?1) which is lower than those of previously reported methods for solid-phase extraction combined with CE. The recoveries of OTA from urine spiked at levels of 50, 150 and 300 ng mL^?1 ranged from 93 to 97 %.

Determination of Herbicides in Soil by Dispersive Solid-Phase Extraction,Dispersive Liquid–Liquid Microextraction,and High-Performance Liquid Chromatography

A method for determination of five herbicides (i.e., quinclorac, metsulfuron-methyl, bensulfuron-methyl, atrazine, prometryn) in soil was developed by dispersive solid-phase extraction combined with dispersive liquid–liquid microextraction and high-performance liquid chromatography. The analytes were removed from the soil by liquid partitioning with acetonitrile/5% acetic acid, purified using a octadecylsilane sorbent, and subsequently extracted before chromatographic analysis. Under the optimized conditions, the linear dynamic range was from 10.0 to 300 ng g^?1 with correlation coefficients (r) between 0.9971 and 0.9985. The limits of detection were between 1.5 and 3.1 ng g^?1, with relative standard deviations from 3.8% to 6.7% (n = 5). The recovery of the herbicides from soil at fortification levels of 20.0 and 100.0 ng g^?1 were between 71.5% and 94.3%. The method was successfully applied to the determination of the analytes in soil.     

Sulfur modified with 2-mercaptobenzoxazole as a new sorbent for preconcentration of silver prior to determination by flame atomic absorption spectrometry

A solid-phase extraction method for preconcentration of silver and consequent determination by atomic absorption spectrometry is described. The method is based on the retention of silver on sulfur modified with 2-mercaptobenzoxazole. The retained silver is eluted from the column with a thiourea solution and determined by flame atomic absorption spectrometry. The preconcentration conditions such as pH, amount of reagent loaded on sorbent, type of eluent and its volume, flow rate and interfering ions were investigated. The calibration graph was linear in the range of 3–200 ng mL^?1 of Ag⁺ in the initial solution with r = 0.9985. The limit of detection based on 3S_b was 1.0 ng mL^?1. The relative standard deviation for ten replicate measurements of 50 and 150 ng mL^?1 of Ag⁺ was 4.1 and 1.4 %, respectively. The method was applied to the determination of silver in radiology film and water samples.     

Simultaneous preconcentration and determination of malachite green and fuchsine dyes in seafood and environmental water samples using nano-alumina-based molecular imprinted polymer solid-phase extraction

Molecular imprinted polymer for determination of malachite green (MG) and fuchsine basic (FU) dyes by spectrophotometry has been used, to develop a novel simultaneous extraction and preconcentration method. Molecularly imprinted layer-coated nano-alumina (MIP@Nano-Al₂O₃) as adsorbent was prepared by surface molecular imprinting technique, and characterised by FTIR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and thermogravimetric analysis (TGA). The method is based on simultaneous extraction of MG and FU dyes from aqueous solution by using molecularly imprinted polymer and measuring the absorbance at 617 and 546 nm for MG and FU, respectively. Parameters which affect the extraction efficiency such as pH, volume of eluent and amount of adsorbent were investigated and optimised. Linear calibration curves were obtained in the range of 2–750 ng mL^?1 for MG and 1–240 ng mL^?1 for FU under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.655 and 0.245 ng mL^?1 (n = 10) for MG and FU, respectively. The relative standard deviation (RSD) for 100 ng mL^?1 of MG and FU was 2.35 and 3.06% (n = 7), respectively. The method was applied to the simultaneous determination of the dyes in different seafood and environmental water samples.     

An Experimental Design Approach to Selecting the Optimum LC Conditions for the Determination of Local Anaesthetics

A sensitive high performance liquid chromatographic (HPLC) method has been developed and validated for the simultaneous determination of four local anaesthetics: lidocaine, proparacaine, bupivacaine and oxybuprocaine. A full factorial design was used. The chromatographic separation was achieved using a Bondesil C₈ (4.6 × 2.5 mm i.d., particle size 5 μm) analytical column. An optimised mobile phase consisted of acetonitrile and sodium dihydrogen phosphate (pH = 3.0, 20 mM) (30:70, v/v) at a flow rate of 1.2 mL min^?1. Local anaesthetics detection was performed by UV-Vis detector at 220 nm. The retention times for lidocaine, proparacaine, bupivacaine and oxybuprocaine were 5.74, 9.28, 16.84 and 26.26 min, respectively. HPLC-UV-Vis method was linear in the range of 50–5,000 ng mL^?1 for lidocaine and proparacaine and 100–5,000 ng mL^?1 for bupivacaine and oxybuprocaine. The limit of detection (LOD) was 25 ng mL^?1 for lidocaine, proparacaine and 30 ng mL^?1 for bupivacaine and oxybuprocaine. The limit of quantification (LOQ) was found to be 50 ng mL^?1 for lidocaine, proparacaine and 100 ng mL^?1 for bupivacaine, oxybuprocaine. In intra-day and inter-day precision and accuracy analysis, the relative standard deviation was found to be less than 8%.     

Determination of Lead at Trace Level Through Cloud Point Extraction and Atomic Absorption Spectrometry with Electrothermal Atomization: An Environmentally Benign Methodology

The quantification of lead in water samples is presented at the sub-ppb level through preconcentration with cloud point extraction (using Triton x-100 and eriochrome black T) and atomic absorption spectrometry with electrothermal atomization. In order to study the influence of several variables, experimental design analyses were carried out. Linearity was observed between 0.15 to 1.20 ng mL^?1 (r = 0.98), with a detection limit of 0.04 ng mL^?1 and a quantification limit of 0.15 ng mL^?1. A mean recovery of 90 ± 9% (n = 6, P = 0.05) was found; at the precision was 9% expressed as the coefficient of variation. Anions and cations that were studied did not affect the recovery of lead. Water samples of different sources were analyzed directly as well as by the standard addition method; no statistical differences were found between the two procedures. Finally, the present methodology was compared with liquid–liquid extraction of the lead-ditizone complex, using green analytical indicators proposed for this purpose.     

Rabbit Monoclonal Antibody-Based Lateral Flow Immunoassay Platform for Sensitive Quantitation of Four Sulfonamide Residues in Milk and Swine Urine

Based on the available rabbit monoclonal antibody (RabMAb), a rapid and sensitive lateral flow immunoassay (LFA) platform has been developed for quantitative detection of four sulfonamide residues(SRs) of sulfadiazine (SD), sulfathiazole (STZ), sulfapyridine (SP), and sulfamethoxazole (SMX).Within the designed LFA competitive format assay, which was based on antigen-antibody properties, the hapten conjugate N¹-[4-(carboxymethyl)-2-thiazolyl] sulfanilamide linked to protein ovalbumin (TS-OVA) and goat anti-rabbit antibody were sprayed as capture and control reagents, respectively, and then the antibody was conjugated to colloidal gold particles as the detection reagent. With quantitative assessment aided by a colorimetric strip reader, the sensitivities of the established LFA method for SD, STZ, SP, and SMX were 0.91 ng mL^?1, 0.10ng mL^?1,0.12ng mL^?1, and 2.13ng mL^?1, and the half-maximum inhibition concentrations (IC₅₀) were 5.19 ng mL^?1, 1.25 ng mL^?1, 0.66 ng mL^?1, and 24.14 ng mL^?1, respectively. The recoveries at three spiked levels (5, 20, 50 ng mL^?1for SD, STZ, and SP; 20, 50, 100 ng mL^?1 for SMX) were in the range of 78.02–135.10% and 76.40–137.16% for milk and swine urine, respectively. More importantly, the detection performance of the established platform was consistent with that of in-parallel LC-MS/MS analysis. In conclusion, the proposed LFA platform has showed the potential for fast, sensitive and relatively accurate quantification of four sulfonamide residues in practical uses.     

Quantification of Imidacloprid in Honeybees: Development of a Chemiluminescent ELISA

A Chemiluminescent Enzyme-Linked Immuno-Sorbent Assay (CL-ELISA) for determination and quantification of the fungicide imidacloprid in honeybees was developed in an indirect competitive format. The assay was optimized by determining: the optimal coating conjugate concentration and anti-imidacloprid antiserum dilution, the effect of the incubation time on the competitive step, and the tolerance to organic solvents. The IC₅₀ and the limit of detection (LOD) values were 14.8 ng mL^?1 and 0.11 ng mL^?1, respectively, similar to those of colorimetric ELISA with a calibration range of 0.1–2600 ng mL^?1. Cross reactivity of some related compounds such as three imidacloprid metabolites, 6-chloro nicotinic acid, 5-hydroxy-imidacloprid, and imidacloprid olefin, and one other chloronicotinoid insecticide, acetamiprid, were tested. The assay was then applied to honeybee extracts obtained by using the liquid-liquid extraction. The calibration curves in honeybee extracts from the liquid-liquid procedure gave an IC₅₀ of 23.7 ng mL^?1 and a LOD 1.6 ng mL^?1. The average recovery value from honeybee extracts spiked with 100 and 1000 ng mL^?1 of imidacloprid were 73% and 76%, respectively. Finally, the assay was applied to honeybee samples collected during monitoring activities in Italy; it was found that only five of the 27 samples were positives, with low concentrations of imidacloprid ranging between 1.2 and 15.4 ng g^?1.     

Determination of Tangeretin in Rat Plasma by LC-Electrospray-Ion Trap MS

A selective, sensitive, and accurate method has been developed and validated for the quantification of tangeretin in rat plasma. The application of LC-electrospray-ion trap mass spectrometry in full scan and multiple reactions monitoring modes were investigated. Following solid phase extraction using a hydrophilic–lipophilic balance cartridge, the analytes were separated on a C₁₈ column using an isocratic mobile phase composed of acetonitrile/water (50:50, v/v) containing 0.3% formic acid. In full scan mode, the LOQ was 2 ng mL^?1. The standard calibration curve was linear (R ² = 0.9999) over the concentration range 2–200 ng mL^?1. The precision over the concentration range was within 15% (RSD) and the accuracy was ranged from 86 to 115%. In multiple reaction monitoring mode, the LOQ was 1 ng mL^?1 and the standard calibration curve was linear (R ² = 0.9976) over the concentration range 1–100 ng mL^?1 with a precision of 12% and accuracy rangeing from 91 to 113%.     

Application of organo-nanoclay as a solid sorbent for rhodium complex separation and preconcentration

An organo-nanoclay is used as a new, easily accessible, and stable solid sorbent for the preconcentration of trace amounts of rhodium ions from aqueous solution, this followed by its determination by flame atomic absorption spectrometry (FAAS). Rh(III) ion was first complexed with 2,3,5,6-tetra(2-pyridyl) pyrazine (TPPZ) at pH values between 3.0 and 4.7, and then the complex was then adsorbed onto the nanoclay. The rhodium ions were eluted from the sorbent with HCl. The rhodium in the effluent was determined by FAAS. The linear analytical range is between 0.14 ng mL^?1 and 20.0 μg mL^?1 in the initial solution, the relative standard deviation at 2.0 μg mL^?1 of rhodium is 2.6% (n?=?8), the detection limit is 0.03 ng mL^?1, and the preconcentration factor is 140. Experimental parameters including the pH, eluent type, interference by other ions and breakthrough volume were optimized. The method was applied to the determination of rhodium in water, road dust and synthetic samples.     

A Ce3+-imprinted functionalized potassium tetratitanate whisker sorbent prepared by surface molecularly imprinting technique for selective separation and determination of Ce3+

A surface molecular imprinting technology was developed to adsorb Ce(III) ions that showed much higher adsorption affinity and selectivity for than for other metal ions. The batch adsorption process was studied with respect to effects of pH value, residence time, temperature, and initial concentration of Ce(III) ion. The maximum adsorption capacity is 43 mg g^?1 at an initial Ce(III) concentration of 300 mg L^?1 and at a sorbent dosage of 1.0 g L^?1. A Langmuir isotherm fits the experimental data. The imprinted sorbent exhibits a much higher separation and selectivity for the target imprinted ion than the non-imprinted polymer. Cerium ion can be desorbed with 1M hydrochloric acid solution which is also proven by scanning electron microoscopy and X-ray diffraction experiments. The limit of detection is 37 ng mL^?1. The sorbent has been applied to the determination of trace cerium in different environmental samples with satisfactory results.     

Colorimetric Determination of Lead Using Gold Nanoparticles

A combined homogeneous assay and colorimetric determination method using gold nanoparticles was developed for rapid determination of lead(II) in contaminated natural waters. The presence of lead(II) in the colloidal gold suspension causes a change in the absorbance of the suspension. An increase in the absorption property at 595 nm is accompanied by a change in the size of the gold nanoparticles. High concentrations of lead cause aggregation of the gold colloids. Colloidal gold nanoparticles were synthesized using tannic acid as the reducing agent; this reagent allowed selective determination of lead in 10 µL of water, with a detection limit of 310 ng mL^?1 with an analysis time of 5 min. The coefficient of variation for lead(II) within the working range of the assay (520 ng mL^?1–13 µg mL^?1) varied from 1.3% to 9.2%. The limit of detection using this method with a sample volume of 50 µL was 60 ng mL^?1. The coefficient of variation for lead over the working range of the determined concentrations (80 ng mL^?1–25 µg mL^?1) varied from 0.2% to 9.3%, while the values for the inter-day assay (n = 8) were less than 10%. The method was employed for the analysis of river, lake, marsh, and spring water; the recovery of lead was determined to be 72.5%–130% for 10 µL of water and 93.6%–114.7% for 50 µL.     

Preparation of an ionic liquid-mediated carbon nanotube-poly(dimethylsiloxane) fiber by sol–gel technique for determination of polycyclic aromatic hydrocarbons in urine samples using head-space solid-phase microextraction coupled with gas chromatography

A novel ‘ionic liquid-mediated multi-walled carbon nanotube (MWCNT)-poly(dimethylsiloxane) (PDMS)’ hybrid coating was prepared by the covalent functionalization of MWCNTs with hydroxyl-terminated PDMS using the sol–gel technique. The prepared fiber was successfully used for the separation and determination of trace amounts of polycyclic aromatic hydrocarbon compounds (PAHs) in four urine samples using head-space solid-phase microextraction coupled to gas chromatography-flame ionization detection. The proposed fiber has high thermal stability and long durability and it can be used more than 210 times without any significant change in its sorption properties. The effects of important parameters such as the exposure time, sampling temperature, sample ionic strength and stirring rate on the extraction efficiency have been studied and optimized. Under the optimal conditions, the method detection limits (S/N = 3) were in the range of 0.0005–0.004 ng mL^?1 and the limits of quantification (S/N = 10) between 0.002 and 0.01 ng mL^?1. The relative standard deviations for one fiber (repeatability, n = 5) were 4.9–7.5 % and for the fibers obtained from different batches (reproducibility, n = 3), 6.1–8.9 %. The developed method was successfully applied to determine trace levels of PAHs in real urine samples. The obtained relative recoveries for the spiked samples with 0.05 ng mL^?1 of each of the PAH compounds were 89.3–107.2 %.