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.

Rapid fluorimetric assay for primary amine groups in water samples

Bond Elut C₁₈ solid-phase extraction cartridges were used for pre-concentration followed by derivatization with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) of primary amines in water. Optimal conditions were: conditioning the cartridges with borate buffer pH 10.4, retention of the primary amines, addition of the OPA-NAC(3.7 mmol L^–1) 1:1 molar ratio and borate buffer pH 8, elution of the isoindol with MeOH-borate buffer (9:1) pH 10.2 and fluorescence measurement. The equations of the calibration graphs for methylamine, ethylamine, propylamine, butylamine, pentylamine, and -phenylethylamine at _excitation=330 nm and _emission=440 nm, in the optimal conditions are presented. The solid-phase extraction procedure improved ten times the detection limits of the solution derivatization. Those values are in the 0.01–0.06 mg L^–1 interval in function of the amine. Also, it is possible to estimate the total primary aliphatic amine concentration in water, expressed as molar concentration of –NH₂ group or –NH₂-N mg L^–1. On the basis of these studies, the method was applied for the determination of primary amino groups in tap, ground, factory and source water samples.     

Using gas chromatography with atomic emission detection for determining organic pollutants in water

The efficiency of gas chromatography with atomic emission detection (AED) for determining the composition of complex mixtures of organic water pollutants was studied by the example of 13 compounds of different classes. It was found that the correlation between the ratio of AED signals for single element atoms of the compound in the sample and their predetermined ratio in individual solutions additionally supports the identification of impurities in water at a trace level. The determination of a compound by the concentration of one or two elements in its molecule allows the evaluation of the effect of interfering impurities on the results of analysis.     

Rapid determination of atrazine in environmental water samples by a novel liquid phase microextraction

A novel method was described for the rapid determination of atrazine using dispersive liquid phase microextraction in combination with high performance liquid chromatography （HPLC）. Possible impact parameters such as sample pH, extraction and disperser solvents, salting-out effect, and extraction time were investigated. The experimental results indicated that proposed method possessed an excellent analytical performance, The linear range, detection limit, and precision （R.S.D.） were 0.1- 50 ng mL- 1 （R2 = 0.9955）, 0.601 ng mL- 1 and 6,4%, respectively. The proposed method was validated with the real water samples, and the spiked recoveries were in the range of 69.9-89.8%, respectively. These results indicated that the established method with high enrichment factor, short extraction time was an excellent alternative for the routine analysis of atrazine in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Development of a microparticle-based on-site immunoassay for the detection of atrazine in soil and water samples

Atrazine is widely used as a herbicide in agriculture and has been identified as a major groundwater contaminant in the US. Because of the possible hazard associated with its usage, there is a need for an efficient and economic screening method for on-site field testing of atrazine and other s-triazine herbicides in soil and water. We have developed a rapid, on-site test for the detection of atrazine based on the principle of microparticle agglutination inhibition immunoassay. The test detects 50 microg kg(-1) (0.050 ppm) atrazine in soil samples with direct extraction and 1.0 microg L(-1) atrazine in water samples when coupled with solid phase extraction.     

Investigations on the applicability of two ELISA types for the determination of chlorpyrifos in soil samples compared with a gas chromatographic method

Two commercially available ELISA kits for water analysis, a microtiter plate-ELISA based on polyclonal antibodies (p-ELISA) and a magnetic particle tube-ELISA based on monoclonal antibodies (t-ELISA), were used to determine chlorpyrifos residues in soils. Comparison with a gas chromatographic method frequently applied was carried out by fortification experiments and by analyses of real soil samples. At concentration levels of 1.0, 0.1, 0.05 and 0.01 mg/kg, chlorpyrifos was reliably determined by the GC method. Application of the p-ELISA did not permit a reliable quantitation, while the t-ELISA was applicable in a concentration range of 0.05–1.0 mg chlorpyrifos/kg dry soil.     

Investigations on the applicability of two ELISA types for the determination of chlorpyrifos in soil samples compared with a gas chromatographic method

Two commercially available ELISA kits for water analysis, a microtiter plate-ELISA based on polyclonal antibodies (p-ELISA) and a magnetic particle tube-ELISA based on monoclonal antibodies (t-ELISA), were used to determine chlorpyrifos residues in soils. Comparison with a gas chromatographic method frequently applied was carried out by fortification experiments and by analyses of real soil samples. At concentration levels of 1.0, 0.1, 0.05 and 0.01 mg/kg, chlorpyrifos was reliably determined by the GC method. Application of the p-ELISA did not permit a reliable quantitation, while the t-ELISA was applicable in a concentration range of 0.05–1.0 mg chlorpyrifos/kg dry soil. Received: 23 July 1997 / Revised: 10 November 1997 / Accepted: 14 November 1997     

水样中左旋18-甲基炔诺酮的胶体金免疫层析试剂条的研制

研制了一种检测水样中左旋18-甲基炔诺酮(LNG)含量的胶体金免疫层析试剂条.基于包被抗原和检测物对金标抗体的竞争反应,通过可目测的胶体金标记物而得到直观的检测结果.试剂条对LNG的检测,灵敏度为10 ng·ml-1,在10min内显示结果;与己烯雌酚、雌三醇,17(-雌二醇,17β-雌二醇、雌酮、甲泼尼龙、泼尼松龙和...     

An immunochromatographic assay for rapid and simultaneous detection of levonorgestrel and methylprednisolone in water samples

Synthetic contraceptive levonorgestrel (LNG) and glucocorticoid methylprednisolone (MP) residues are eventually discarded to environmental water system and function as environmental hormones, displaying potential risk to humans and ecosystems, thus there is an urgent need for fast, sensitive and simultaneous detection of these compounds in water samples. In this study, a competitive immunochromatographic assay (ICA) using colloidal gold-labeled polyclonal antibodies as probes for rapid and simultaneous detection of LNG and MP in water samples was developed. The visual detection limits of LNG and MP in water samples were 10 ng/mL. The detection process could be completed within 10 min. There was no cross-reactivity of the ICA with other seven compounds. The strips could be stored at 4℃ for 10 weeks without significant loss of activity. The assay is a suitable tool for rapid and semiquantitative detection of LNG and MP in water samples on site.     

Evaluation of magnetic matrix solid‐phase dispersion for the determination of polychlorinated biphenyls in water samples by gas chromatography with electron capture detection

A vortex‐assisted magnetic matrix solid‐phase dispersion method was proposed for the determination of polychlorinated biphenyls in different matrix water samples by gas chromatography with electron capture detection. Magnetic bamboo charcoal (MBC) was synthesized for the adsorption of polychlorinated biphenyls in water samples. Complete separation of the liquid phase and the solid magnetic bamboo charcoal was easily achieved by using a permanent magnet. Under the optimized conditions, good linearity in the range of 0.006–5.0 μg/L was obtained with regression coefficients (r) higher than 0.9986. Based on a signal‐to‐noise ratio of 3, limits of detection were found to be 0.001–0.003 μg/L. Relative standard deviations ranged from 2.92 to 6.56%. Relative recoveries were 96.6–111.2% for the spiked wastewater sample and 90.7–104.7% for the spiked lake water sample. All results showed that the proposed method was simple, sensitive, and reliable for the determination of polychlorinated biphenyls in water samples.     

Rapid and sensitive method for determining free amino acids in honey by gas chromatography with flame ionization or mass spectrometric detection

This paper describes a rapid, sensitive and specific method for determination of free amino acids in honey involving a new reaction of derivatization and gas chromatography (GC) with flame ionization (FID) and mass spectrometric (MS) detection. The method allows the determination of 22 free amino acids in honey samples in a short time: 8 and 5 min for GC-FID and GC-MS, respectively. Quantitation was performed using Norvaline as internal standard, with detection limits ranging between 0.112 and 1.795 mg/L by GC-FID and between 0.001 and 0.291 mg/L by GC-MS in the selected-ion monitoring mode. The method was validated and applied to a set of 74 honey samples belonging to four different botanical origins: eucaliptus, rosemary, orange and heather. The statistical treatment of data shows a correct classification of different origins over 90%.     

Rapid polyelectrolyte-based immunofiltration technique for testosterone detection in serum samples

A new immunofiltration assay for testosterone is proposed. During the first step of the assay, testosterone molecules in serum samples compete in solution with the testosterone-peroxidase conjugate for interaction with anti-testosterone antibodies pre-bound to the conjugate between staphylococcal protein A and polymethacrylate polyanion. The reaction mixture is then filtered through a membrane charged with immobilized poly(N-ethyl-4-vinylpyridinium) polycation. The filtration is accompanied by a rapid separation of the polyanion containing complexes due to high-affinity electrostatic interactions. Following removal of unbound compounds the immobilized peroxidase is detected using a substrate that produces an insoluble coloured product. The proposed assay has been shown to combine high speed (20 min) and sensitivity (0.1 ng ml(-1)), and to be applicable for out-of-laboratory conditions. Based on densitometric measurements, the RSD of the assay is calculated to be 3.2-5.1% (n = 4). The proposed assay is 4 times faster than the microplate enzyme immunoassay (ELISA) based on the same immunoreagents. Pre-incubation of the antibody and the polyanion-protein A conjugate at a certain ratio excludes the influence of immunoglobulins from the tested serum samples on the assay results. The polyanion-protein A conjugate can be used as a universal reagent, eliminating the necessity to modify specific antibodies for each immunoassay.     

Enantioselective gas chromatographic assay with electron-capture detection for dl-ritalinic acid in plasma

Enantioselective gas chromatographic assays for the quantitation of methylphenidate and its major metabolite ritalinic acid in plasma are described. The procedures involved the extraction of methylphenidate enantiomers from alkanised plasma. The plasma was then washed to ensure complete removal of methylphenidate before saturation with sodium carbonate to promote the extraction of ritalinic acid enantiomers with ethyl acetate-isopropanol (60:40) solvent mixture. Subsequently, ritalinic acid enantiomers were converted back into methylphenidate enantiomers by Fisher-Speier esterification. N-Heptafluorobutyryl-L-prolyl chloride, a chiral acylating reagent, was used to convert the enantiomers of methylphenidate into their corresponding diastereomeric amide derivatives, which were separated cleanly on an achiral capillary column (OV-225) and quantitated with electron-capture detection. The assays were sensitive, reliable and reproducible.     

Development of a fiber-in-tube microextraction protocol for gas chromatography-electron capture detection of hexachlorocyclohexanes in water samples

A fiber-in-tube microextraction protocol was developed and coupled with gas chromatography-electron capture detector (GC-ECD) for determination of trace hexachlorocyclohexanes (HCHs) in water samples. The developed technique was performed by immersing a PTFE fiber-packed and organic solvent-filled PTFE tube in the stirred aqueous solution. Extraction took place between the solvent permeated fibers and sample solution. The extract was then analyzed by GC-ECD. The effects of fiber quantity, extraction time, agitation, addition of salt and pH of sample solution were investigated in detail. Extraction of the analytes in 8 ml aqueous solution for 20 min yielded enrichment factors of 221-538. The limits of detection (S/N = 3) and the limits of quantitation (S/N = 8) were 2-12 ng l⁻¹ and 6-32 ng l⁻¹, respectively. The precision (R.S.D.s, n = 5) was 0.1% for retention time and 1.8-4.8% for peak height. The developed methodology was applied to the determination of trace HCHs in local river water samples.     

Rapid method for determination of 228Ra in water samples

A new rapid method for the determination of ²²⁸Ra in natural water samples has been developed at the SRNL/EBL (Savannah River National Lab/Environmental Bioassay Laboratory) that can be used for emergency response or routine samples. While gamma spectrometry can be employed with sufficient detection limits to determine ²²⁸Ra in solid samples (via ²²⁸Ac), radiochemical methods that employ gas flow proportional counting techniques typically provide lower minimal detectable activity levels for the determination of ²²⁸Ra in water samples. Most radiochemical methods for ²²⁸Ra collect and purify ²²⁸Ra and allow for ²²⁸Ac daughter ingrowth for ~36 h. In this new SRNL/EBL approach, ²²⁸Ac is collected and purified from the water sample without waiting to eliminate this delay. The sample preparation requires only about 4 h so that ²²⁸Ra assay results on water samples can be achieved in <6 h. The method uses a rapid calcium carbonate precipitation enhanced with a small amount of phosphate added to enhance chemical yields (typically >90 %), followed by rapid cation exchange removal of calcium. Lead, bismuth, uranium, thorium and protactinium isotopes are also removed by the cation exchange separation. ²²⁸Ac is eluted from the cation resin directly onto a DGA Resin cartridge attached to the bottom of the cation column to purify ²²⁸Ac. DGA Resin also removes lead and bismuth isotopes, along with Sr isotopes and ⁹⁰Y. La is used to determine ²²⁸Ac chemical yield via ICP-MS, but ¹³³Ba can also be used instead if ICP-MS assay is not available. Unlike some older methods, no lead or strontium holdback carriers or continual readjustment of sample pH is required.