Preconcentration of ultra-trace amounts of iron and antimony using ion pair solid phase extraction with modified multi-walled carbon nanotubes

Ion pair solid phase extraction was applied to the simultaneous preconcentration of iron and antimony. The ion pairs consisting of FeCl₄ ^? or SbCl₄ ^? anions and the benzyldimethyltetradecyl ammonium cation were formed on the surface of multi-walled carbon nanotubes, then eluted with nitric acid, and the elements finally quantified by ETAAS. The adsorption capacities of the impregnated MWCNTs are 9.2 mg g^?1 for iron and 27.5 mg g^?1 for antimony. The following analytical figures of merit were determined for iron and antimony, respectively: Enrichment factors of 210 and 230, assay precisions of ±5.3 % and ±4.8 %, linear calibration plots from 0.7 to 9.4 and 13.0 to 190 ng L^?1, and detection limits of 0.17 and 3.5 ng L^?1. The method was applied to the determination of iron and antimony in human hair, synthetic sample, and to the certified reference materials gold ore (MA-1b) and trace elements in water (SRM 1643d).

Assessing hazelnut allergens by protein- and DNA-based approaches: LC-MS/MS,ELISA and real-time PCR

Hazelnut (Corylus avellana L.) is responsible for a significant part of the allergies related to nuts. Still, it is a very much appreciated nut and as consequence is widely used in all types of processed foods, such as chocolates. Correct food labelling is currently the most effective means of preventing the consumption of allergenic ingredients, namely hazelnut, by the sensitised/allergic individuals. Thus, to verify labelling compliance and to ensure allergic patient protection, the development of highly sensitive methodologies is of extreme importance. In this study, three major methodologies, namely enzyme-linked immunosorbent assays (ELISA), liquid chromatography coupled with mass spectrometry and real-time polymerase chain reaction, were evaluated for their performance regarding the detection of hazelnut allergens in model chocolates. The sandwich ELISA and respective antibodies were in-house developed and produced. With sensitivity levels of approximately 1 mg kg^?1 and limits of quantification of 50–100 mg kg^?1, all the performed methods were considered appropriate for the identification of hazelnut in complex foods such as chocolates. To our knowledge, this was the first successful attempt to develop and compare three independent approaches for the detection of allergens in foods.

Determination and pharmacokinetic study of the diacid metabolite of norcantharidin in beagle plasma by use of liquid chromatography–tandem mass spectrometry

Because norcantharidin (NCTD) is unstable and subject to ring opening and hydrolysis, the diacid metabolite of norcantharidin (DM-NCTD) is the stable form of NCTD found in normal saline solution. Conversion of NCTD to DM-NCTD is almost 100 %, making it possible to determine and investigate the pharmacokinetics of DM-NCTD converted from NCTD. In this paper, a sensitive, simple and selective liquid chromatographic–tandem mass spectrometric method was developed and validated for determination of DM-NCTD in beagle plasma. DM-NCTD was detected in multiple-reaction monitoring (MRM) mode by using the dehydrated ion 169.3 as precursor ion and its product ion 123.1 as the detected ion. Ribavirin was used as internal standard and detected in MRM mode by use of precursor ions, resulting in a product ion transition of m/z 267.1?→?135.1. This method was successfully used for a pharmacokinetic study of DM-NCTD in beagles after intravenous administration of DM-NCTD in normal saline solution at doses of 0.39, 0.78, and 1.6 mg kg^?1. DM-NCTD had dose-dependent kinetics across the dosage range investigated, with enhanced T _1/2α and AUC_0-12 and apparently decreasing V _d and CL with increasing dosage. After single-dose administration, T _1/2α ranged from 0.20 to 0.55 h, AUC_0-12 from 1.81 to 43.6 μg mL^?1 h^?1, V _d from 228 to 55.9 mL kg^?1, and CL from 220 to 36.5 mL kg^?1 h^?1 (P?<?0.01). The results indicated nonlinear pharmacokinetic behavior of DM-NCTD in beagles, suggesting that the risk of DM-NCTD in normal saline solution intoxication may be non-proportionally increased at higher doses.

A sensitive and specific ELISA for determining a residue marker of three quinoxaline antibiotics in swine liver

Methyl-3-quinoxaline-2-carboxylic acid (MQCA) is a possible residue marker for three quinoxaline veterinary medicines (olaquindox, mequindox, and quinocetone). The wide application of mequindox/quinocetone or the illegal use of olaquindox leads to MQCA residue in animal’s original food, thereby threatening the safety of human food. The indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) with a specific coating antigen and monoclonal antibody (MAB) was established and optimized for detecting MQCA in swine liver. Samples were acidified with 2 mol?l^?1 hydrochloric acid, extracted with ethyl acetate–hexane–isopropanol (8?+?1?+?1, v/v/v) and then detected by IC-ELISA. The logarithm correlation of standards to OD values ranged from 0.2 to 200 μg?l^?1, with IC₅₀ of 6.46 μg?l^?1. Negligible cross-reactivity happened to five quinoxaline antibiotics (olaquindox, mequindox, quinocetone, carbadox, and cyadox) and the metabolite of carbadox and cyadox (quinoxaline-2-carboxylic acid). When spiked with 1 to 100 μg?kg^?1 of MQCA, the recoveries ranged from 85.44 to 100.02 %, with the intra-assay coefficient of variation (CV) of 6.64–10.57 % and inter-assay CV of 7.29–10.88 %. The limit of detection for MQCA was 1.0 μg?kg^?1 in swine liver. Furthermore, incurred samples were detected by the IC-ELISA and then conformed by a reported LC/MS/MS method, it shown that there was good correlation between the two methods. All these results indicated that the IC-ELISA method is appropriate for surveillance MQCA residue in animal tissues.

Gas chromatography–tandem mass spectrometry analysis of 52 monohydroxylated metabolites of polycyclic aromatic hydrocarbons in hairs of rats after controlled exposure

A method based on gas chromatography–tandem mass spectrometry after derivatization with N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide was developed for the analysis of monohydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in hair. The method focused on 52 target compounds corresponding to two- to six-ring monohydroxylated metabolites of polycyclic aromatic hydrocarbons (PAHs). The limits of quantification ranged from 0.2 to 50 pg mg^?1. The method was then applied to the analysis of hair samples collected from rats exposed to 12 PAHs at 0.01, 0.1, and 1 mg kg^?1, by intraperitoneal injection, for 28 days. The results of this study confirm that these metabolites can be incorporated in hair after intraperitoneal administration of the corresponding parent compound. Only 20 of the 52 metabolites were actually detected in hair samples and corresponded to nine parent PAHs. The mean concentrations of OH-PAHs in rat hair samples exposed to PAHs at 1 mg kg^?1 ranged from 0.6?±?0.2 pg mg^?1 for 8-hydroxybenzo[b]fluoranthene to 6.7?±?1.0 pg mg^?1 for 1-hydroxypyrene. The results also demonstrated that hair pigmentation has no influence on the concentration of most OH-PAHs. This animal experiment confirmed the incorporation of PAH metabolites in hair and demonstrated that the method was sufficiently sensitive to detect low levels of exposure to PAHs. These results confirmed the usefulness of hair analysis in the biomonitoring of human exposure to PAHs.

Chemiluminescence competitive indirect enzyme immunoassay for 20 fluoroquinolone residues in fish and shrimp based on a single-chain variable fragment

A chemiluminescent competitive indirect enzyme-linked immunosorbent assay, based on a mutant single-chain variable fragment (scFv), was developed to detect a broad range of fluoroquinolones (FQs) in fish and shrimp matrices. In this study, the best scFvC4A9H1_mut2 was adopted, which showed 10-fold improved affinity to sarafloxacin (SAR), difloxacin (DIF), and trovafloxacin (TRO), while the affinity to other FQs was fully inherited from wild-type scFvC4A9H1. In the optimized generic test, scFvC4A9H1_mut2 in combination with norfloxacin–ovalbumin conjugate and horseradish peroxidase-labeled anti-c-myc 9E10 antibody showed 50 % binding inhibition (IC₅₀) at 0.12 μg kg^?1 for norfloxacin in buffer. Screening for the class of FQ antibiotics is accomplished using a simple, rapid extraction carried out with ethanol/acetic acid (99:1, v/v). This common extraction was able to detect 20 FQ residues such as s ciprofloxacin (CIP), danofloxacin, DIF, enoxacin, enrofloxacin (ENR), fleroxacin, amifloxacin, flumequine, levofloxacin, lomefloxacin hydrochloride, marbofloxacin, norfloxacin (NOR), ofloxacin, orbifloxacin, pazufloxacin, pefloxacin-d5 (PEF), prulifloxacin, SAR, sparfloxacin, and TRO in fish and shrimp. The limit of detection (LOD) for NOR was 0.2 μg kg^?1 and the LODs for CIP and ENR were all <0.2 μg kg^?1. Values of LODs inferred from the cross-reactivity data will range from approximately 0.23 μg kg^?1 for PEF to 2.1 μg kg^?1 for TRO. Field fish and shrimp samples were analyzed and compared to the results obtained from liquid chromatography tandem mass spectrometric method. All five instances (from 0.25 to 15.6 μg kg^?1) in which FQs were present at concentrations near or above the assay LOD were identified as positive by the newly developed assay, demonstrating the usefulness of this assay as a screening tool.

Cetyltrimethylammonium-coated magnetic nanoparticles for the extraction of bromate,followed by its spectrophotometric determination

We report on a combination of magnetic solid-phase extraction and spectrophotometric determination of bromate. Cetyltrimethylammonium ion was adsorbed on the surface of phenyl-functionalized silica-coated Fe₃O₄ nanoparticles (Ph-SiO₂@Fe₃O₄), and these materials served as the sorbent. The effects of surfactant and amount of sorbent, the composition of the desorption solution, the extraction time and temperature were optimized. Under optimized conditions, an enrichment factor of 12 was achieved, and the relative standard deviation is 2.9 % (for n?=?5). The calibration plot covers the 1–50 ng mL^?1 range with reasonable linearity (r ²?>?0.998); and the limit of detection is 0.5 ng mL^?1. The method is not interfered by ionic compounds commonly found in environmental water samples. It was successfully applied to the determination of bromate in spiked water samples.

Enantioselective Separation and Determination of Carnosine in Rat Plasma by Fluorescence LC for Stereoselective Pharmacokinetic Studies

A sensitive fluorescence liquid chromatographic analytical method was developed for the simultaneous determination of carnosine enantiomers in rat plasma. The method was applied to pharmacokinetic studies. Chiral separation of carnosine enantiomers was achieved by pre-column derivatization with o-phthaldialdehyde and the thiol N-acety-l-cysteine as derivating reagents. They were separated on an ODS column and detected by fluorescence detection (λ_ex = 350 nm, λ_em = 450 nm). γ-Aminobutyric acid was used as internal standard. The method was linear up to 6,000 ng mL^?1 for l-carnosine, 4,000 ng mL^?1 for d-carnosine. Low limit of quantitation (LLOQ) was 40 ng mL^?1 for each isomer. The relative standard deviations obtained for intra- and inter-day precision were lower than 12% and the recoveries were higher than 75% for both enantiomers. The method was applied to a stereoselective study on the pharmacokinetics of carnosine after oral administration with a single dose (carnosine, 75 mg kg^?1 for each isomer) to a rat. The initial data indicated that l-carnosine had a larger value of the highest plasma concentration than d-carnosine (C _max 5,344 vs. 1,914 ng mL^?1), and that of l-carnosine had a lower value of AUC_(0?∞) and t _1/2(h) (AUC_(0?∞) 5,306 vs. 6,321 ng h mL^?1, t _1/2 1.43 vs. 3.37 h). Our results indicated that the pharmacokinetic of l-carnosine and d-carnosine revealed enantioselective properties significantly.     

Comparison of an HPTLC method with the Reflectoquant assay for rapid determination of 5-hydroxymethylfurfural in honey

5-Hydroxymethylfurfural (HMF) was analyzed in 17 botanical varieties of honey from 12 countries. A recently developed high-performance thin-layer chromatographic (HPTLC) method was limited because of increased matrix effects at higher honey sample loading. Therefore, the method was modified to achieve higher sensitivity and eliminate matrix interference by use of rectangular application combined with a focusing step. The HPTLC results were compared with results from the new spectrophotometric Reflectoquant hydroxymethylfurfural assay. Both methods had quantification limits of 4 mg kg^?1 and were suitable for rapid quantification of HMF in honey at the strictest regulated level of 15 mg kg^?1. Comparable results were obtained for the 17 honey samples, with a mean deviation of 2.9 mg kg^?1 (15 %). The optimized HPTLC method was proved to be highly matrix-robust and was validated for the 17 different honey matrices (correlation coefficients ≥0.9994 (n?=?6), mean intra-day precision 3.2 % (n?=?3 within a plate; n?=?2 repeated within a day), mean inter-day precision 3.7 % (n?=?3), mean reproducibility over the whole procedure including sample preparation 4.1 % (n?=?2), and mean recovery 106.9 % (n?=?5 different concentrations; n?=?4 different honey matrices). Recovery for a range of different application volumes, and thus for different honey matrix loading, differed by only ≤4.2 %. HMF results when calculated by use of external calibration and by use of the standard addition method varied by 8.8 %. Both revealed that any matrix effect was minor and that the original matrix interference problem was successfully solved.

Selection and identification of ssDNA aptamers recognizing zearalenone

Zearalenone (ZEN) is a nonsteroidal estrogenic mycotoxin produced by Fusarium graminearum on maize and barley. Because most current methods of ZEN detection rely on the use of low-stability antibodies or expensive equipment, we sought to develop a rapid, low-cost determination method using aptamers instead of antibodies as the specific recognition ligands. This work describes the isolation and identification of single-stranded DNA (ssDNA) aptamers recognizing ZEN using the modified systematic evolution of ligands by exponential enrichment methodology based on magnetic beads. After 14 rounds of repeated selection, a highly enriched ssDNA library was sequenced and 12 representative sequences were assayed for their affinity and specificity. The best aptamer, 8Z₃₁, with a dissociation constant (K _d) of 41?±?5 nM, was successfully applied in the specific detection of ZEN in binding buffer and in real samples based on a magnetic separation/preconcentration procedure. This analytical method provided a linear range from 3.14?×?10^?9 to 3.14?×?10^?5 M for ZEN, and the detection limit was 7.85?×?10^?10 M. The selected aptamers are expected to be used in the potential development of affinity columns, biosensors, or other analytical systems for the determination of ZEN in food and agricultural products.

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

Determination of phthalate esters in edible oils by use of QuEChERS coupled with ionic-liquid-based dispersive liquid–liquid microextraction before high-performance liquid chromatography

A selective and low organic-solvent-consuming method of sample preparation combined with high-performance liquid chromatography with diode-array detection is introduced for analysis of phthalic acid esters in edible oils. Sample treatment involves initial liquid–liquid partitioning with acetonitrile, then QuEChERS cleanup by dispersive solid-phase extraction with primary secondary amine as sorbent. Preconcentration of the analytes is performed by ionic-liquid-based dispersive liquid–liquid microextraction, with the cleaned-up extract as disperser solvent and 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent. Under the optimized conditions, correlation coefficients (r) were 0.998–0.999 and standard errors (S _y/x ) were 2.67–3.37?×?10³ for calibration curves in the range 50–1000 ng g^?1. Detection limits, at a signal-to-noise ratio of 3, ranged from 6 to 9 ng g^?1. Intra-day and inter-day repeatability, expressed as relative standard deviation, were in the ranges 1.0–6.9 % and 2.4–9.4 %, respectively. Recovery varied between 84 % and 106 %. The developed method was successfully used for analysis of the analytes in 28 edible oils. The dibutyl phthalate content of four of the 28 samples (14 %) exceeded the specific migration limit established by domestic and international regulations.

A portable electrochemical magnetoimmunosensor for detection of sulfonamide antimicrobials in honey

A new electrochemical magnetoimmunosensor (EMIS) has been developed for the screening of residues of sulfonamide antimicrobials in honey samples. The immunosensor is able to detect up to ten different sulfonamide congeners at levels below the action points established in some European countries (25 μg kg^?1) after a hydrolysis step in which the sulfonamides are released from the corresponding conjugates formed in samples of this type. In spite of the complexity of the sample after the hydrolysis procedure, the EMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. For example, sulfapyridine, used as a reference, can be detected in hydrolyzed honey with a limit of detection (IC₉₀) of 0.1?±?0.03 μg kg^?1. Considering that the use of antibiotics for bee treatment is prohibited in the European Union, the immunosensor presented here could be an excellent screening tool. Moreover, several samples can be processed in parallel, which facilitates the analysis, reducing the necessity to use more costly confirmatory methods for just screening. As a proof of concept, a set of blind honey samples (spiked and incurred) were analyzed and the results were compared with those obtained by high-performance liquid chromatography–tandem mass spectrometry, demonstrating the potential of the EMIS as a screening tool.

Selective isolation of hemoglobin by use of imidazolium-modified polystyrene as extractant

Ionic liquids have attracted much attention in the analysis of a variety of species. The functional groups in ionic liquids can result in highly efficient separation and enrichment and, because of their typical lack of volatility, they are environmentally benign. We grafted imidazole cations onto the surface of chloromethyl polystyrene, denoted PS-CH₂-[MIM]⁺Cl^?, and this modified polymer was used to selectively extract the protein hemoglobin (Hb). The prepared extractant PS-CH₂-[MIM]⁺Cl^?, containing 2 mmol immobilized imidazole groups per gram polymer, was characterized by FT-IR, surface charge analysis, and elemental analysis. The adsorption efficiency was 91 %. The adsorption capacity of the PS-CH₂-[MIM]⁺Cl^? for Hb was 23.6 μg mg^?1, and 80 % of the retained Hb could be readily recovered by use of 0.5 % (m/v) aqueous sodium dodecyl sulfate (SDS) solution as eluate. The activity of the eluted Hb was approximately 90 %. The prepared imidazole-containing solid phase polymer was used for direct adsorption of Hb without use of any other solid matrix as support of the ionic liquid. The material was used in practice to isolate Hb from human whole blood.

Detection of trace nitrite in waters using a QDs-based chemiluminescence analysis system

In the present work, a novel flow-injection chemiluminescence method based on CdTe quantum dots (QDs) was developed for the determination of nitrite. Weak chemiluminescence (CL) signals were observed from a CdTe QDs–H₂O₂ system under basic conditions. The addition of a trace amount of hemoglobin (Hb) caused the CL from the CdTe QDs–H₂O₂ system to increase substantially. In the presence of nitrite, the ferrous Hb reacted with the nitrate to form ferric Hb and NO. The NO then bound to ferrous Hb to generate iron nitrosyl Hb. As a result, the CL signal from the CdTe QDs–H₂O₂–Hb system was quenched. Thus, a flow-injection CL analytical system for the determination of trace nitrite was established. Under optimum conditions, there was a good linear relationship between CL intensity and the concentration of nitrite in the range 1.0?×?10^?9 to 8.0?×?10^?7 mol L^?1 (R ²?=?0.9957). The limit of detection for nitrite using this system was 3.0?×?10^?10 mol L^?1 (S/N?=?3). This method was successfully applied to detect nitrite in water samples.

Magnetic titanium oxide nanoparticles for hemimicelle extraction and HPLC determination of organophosphorus pesticides in environmental water

We report on a method for the extraction of organophosphorus pesticides (OPPs) from water samples using mixed hemimicelles and magnetic titanium dioxide nanoparticles (Fe₃O₄@TiO₂) modified by cetyltrimethylammonium. Fe₃O₄@TiO₂ nanoparticles were synthesized by a hydrothermal process and then characterized by scanning electron microscopy and Fourier transform IR spectrometry. The effects of the quantity of surfactant, extraction time, desorption solvent, pH value, extraction volume and reuse of the sorbent were optimized with respect to the extraction of OPPs including chlorpyrifos, dimethoate, and trichlorfon. The extraction method was applied to analyze OPPs in environmental water using HPLC along with UV detection. The method has a wide linear range (100–15,000 ng L^?1), good linearity (r?>?0.999), and low detection limits (26–30 ng L^?1). The enrichment factor is ~1,000. The recoveries (at spiked levels of 100, 1,000 and 10,000 ng L^?1) are in the range of 88.5–96.7 %, and the relative standard deviations range from 2.4 % to 8.7 %.

Determination of soy proteins in food samples by dispersive solid-phase immunoextraction and dynamic long-wavelength fluorometry

We report on a method for the determination of soy proteins in food samples via dispersive solid-phase immunoextraction using gold-coated magnetic nanoparticles (NPs) as a support. Soy proteins were first extracted using anti-soy protein antibodies immobilized on the NPs, and then quantified by measuring the increase in fluorescence of the long-wavelength fluorophore cresyl violet in the presence of the anionic surfactant sodium dodecyl sulfate at neutral pH in a flow system. The method involves the use of two standard or sample aliquots. The fluorescence intensity of one aliquot is directly measured whereas that of the other aliquot is measured after immunoextraction. The difference between the peak heights of both aliquots serves as the analytical information that is directly proportional to the protein concentration. The limit of detection is 0.35 mg L^?1, the linear range is from 1 to 15 mg L^?1, and the relative standard deviation is <?5 %. Proteins such as bovine serum albumin and globulins do not interfere at the same concentration level. The method was applied to the analysis of soy-based beverages and gave recoveries in the range between 80.0 and 107.3 %.

pH-triggered PMAA-b-HTPB-b-PMAA copolymer micelles: physicochemical characterization and camptothecin release

pH-sensitive poly(methacrylic acid)-block-hydroxyl-terminated polybutadiene-block-poly(methacrylic acid) block copolymers were synthesized by atom transfer radical polymerization of t-butyl methacrylate and follow-up acidolysis. The copolymers can spontaneously assemble into stable and nearly spherical micelle aggregates in aqueous solution, with hydrodynamic diameters (D _h ) from 51 to 92 nm and critical micelle concentration of 3.90–7.76 mg L^?1. Zeta potentials were found to be increased with increasing (monomer)/(initiator) molar ratios. A pH-dependent phase behavior is produced at approximately 5.4–5.6, as determined by D _h and I ₃₃₅/I ₃₃₂ fluorescence intensity ratios. The in vitro camptothecin (CPT) release was compositional and pH dependent, and the cumulative CPT release below pH 7.2 was higher than that in pH 7.4. They could inhibit the premature burst CPT release. The copolymer micelles were low in cytotoxicity even at a micellar concentration of 800 mg L^?1, and therefore they may be used as potential drug-delivery carriers.

Solid-phase preconcentration of cadmium(II) using amino-functionalized magnetic-core silica-shell nanoparticles, and its determination by hydride generation atomic fluorescence spectrometry

We report on the synthesis and evaluation of aminated-CoFe₂O₄/SiO₂ nanoparticles that can serve as a selective solid-phase sorbent for the extraction of cadmium ion. The nanoparticles consist of a magnetic CoFe₂O₄ core and an amino-modified silica shell. They can efficiently extract cadmium(II) ion and then can be isolated from the sample solution due to the magnetic nature of the core. The effects of the experimental conditions on the extraction process were optimized. Cadmium was then quantified by hydride generation atomic fluorescence spectrometry. The resulting calibration curve is linear in the concentration range of 0.01–10 μg?L^?1, the instrumental detection limits (3σ) is 3.15 ng?L^?1 and the relative standard deviation is 4.9 % at the 1.0 μg?L^?1 level (for n?=?11). The enrichment factor is 50 (for 50 mL samples), and the adsorbent can be used for at least 45 cycles of preconcentration and elution. The method was applied to the determination of cadmium in environmental water samples, and successfully validated by analyzing two certified reference materials.

Enzyme-linked immunosorbent assay and immunochromatographic strip for rapid detection of atrazine in water samples

We have developed a heterologous direct competitive enzyme-linked immunosorbent assay (ELISA) and a colloidal gold-based immunochromatographic (ICG) strip for the determination of the herbicide atrazine in water samples. The ELISA had a half-maximum inhibition concentration (IC₅₀) of 0.12 ng mL^?1 and a limit of detection (LOD, calculated as the IC₁₅ value) of 0.01 ng mL^?1. The average of recoveries for all spiked water samples was 96.5%. There was a good correlation between the data determined by this ELISA and those obtained by high performance liquid chromatography (HPLC) (r ² ?=?0.996). The visual LOD of the ICG strip assay was 2 ng mL^?1. The assay process only took 10 min, and no sample pretreatment was required. Its high specificity, sensitivity and fast detection made the strip well suited for on-site screening of atrazine in water samples. Both the ELISA and the ICG strip assay are useful for rapid analysis of a large number of water samples at low cost.