Preparation of antibodies and development of a sensitive immunoassay with fluorescence detection for triazine herbicides

Sensors Applied for the Detection of Pesticides and Heavy Metals in Freshwaters

Water is essential for every life living on the planet. However, we are facing a more serious situation such as water pollution since the industrial revolution. Fortunately, many efforts have been done to alleviate/restore water quality in freshwaters. Numerous sensors have been developed to monitor the dynamic change of water quality for ecological, early warning, and protection reasons. In the present review, we briefly introduced the pollution status of two major pollutants, i.e., pesticides and heavy metals, in freshwaters worldwide. Then, we collected data on the sensors applied to detect the two categories of pollutants in freshwaters. Special focuses were given on the sensitivity of sensors indicated by the limit of detection (LOD), sensor types, and applied waterbodies. Our results showed that most of the sensors can be applied for stream and river water. The average LOD was72.53±12.69 ng/ml (n=180) for all pesticides, which is significantly higher than that for heavy metals (65.36±47.51 ng/ml,n=117). However, the LODs of a considerable part of pesticides and heavy metal sensors were higher than the criterion maximum concentration for aquatic life or the maximum contaminant limit concentration for drinking water. For pesticide sensors, the average LODs did not differ among insecticides (63.83±17.42 ng/ml,n=87), herbicides (98.06±23.39 ng/ml,n=71), and fungicides (24.60±14.41 ng/ml,n=22). The LODs that differed among sensor types with biosensors had the highest sensitivity, while electrochemical optical and biooptical sensors showed the lowest sensitivity. The sensitivity of heavy metal sensors varied among heavy metals and sensor types. Most of the sensors were targeted on lead, cadmium, mercury, and copper using electrochemical methods. These results imply that future development of pesticides and heavy metal sensors should (1) enhance the sensitivity to meet the requirements for the protection of aquatic ecosystems and human health and (2) cover more diverse pesticides and heavy metals especially those toxic pollutants that are widely used and frequently been detected in freshwaters (e.g., glyphosate, fungicides, zinc, chromium, and arsenic).

Applications of Green Chemistry Approaches in Environmental Analysis

Background:

Green chemistry is the application of methodologies and techniques to reduce the use of hazardous substances, minimize waste generation and apply benign and cheap applications.

Methods:

In this article, the following issues were considered: greener solvents and reagents, miniaturization of analytical instrumentation, reagent-free methodologies, greening with automation, greener sample preparation methods, and greener detection systems. Moreover, the tables along with the investigated topics including environmental analysis were included. The future aspects and the challenges in green analytical chemistry were also discussed.

Results:

The prevention of waste generation, atomic economy, use of less hazardous materials for chemical synthesis and design, use of safer solvents, auxiliaries and renewable raw materials, reduction of unnecessary derivatization, design degradation products, prevention of accidents and development of real-time analytical methods are important for the development of greener methodologies.

Conclusion:

Efforts should also be given for the evaluation of novel solid phases, new solvents, and sustainable reagents to reduce the risks associated with the environment. Moreover, greener methodologies enable energy efficient, safe and faster that reduce the use of reagents, solvents and preservatives which are hazardous to both environment and human health.

A class-selective immunoassay for simultaneous analysis of anilinopyrimidine fungicides using a rationally designed hapten

The development of multianalyte immunoassays constitutes a main research issue in the field of bioanalytical techniques. In the present study, class-specific antibodies against the three members of the anilinopyrimidine family of fungicides (pyrimethanil, cyprodinil and mepanipyrim) were raised by using a bioconjugate of a rationally designed hapten [5-(6-methyl-2-(phenylamino)pyrimidin-4-yl)pentanoic acid]. Highly sensitive immunoassays were developed for the generic determination of these compounds, using the competitive enzyme-linked immunosorbent assay (ELISA). Particularly, a direct antibody-coated competitive ELISA afforded identical sensitivity for the three anilinopyrimidines, with IC₅₀ values of 0.26, 0.27 and 0.25 μg L^-1 for pyrimethanil, cyprodinil and mepanipyrim, respectively. This immunoassay was fully characterized and applied to the multianalyte determination of anilinopyrimidine fungicides in white and red wines, with a limit of quantification of 1 μg L^-1, average recoveries from 93.1 to 114.4%, and relative standard deviations lower than 20%. Commercial wine samples were analyzed and those containing detectable anilinopyrimide residues were verified by a reference chromatographic technique.

Seasonal variation of chloro-s-triazines in the Hartbeespoort Dam catchment, South Africa

Seasonal variation of eight chloro-s-triazine herbicides and seven major atrazine and terbuthylazine degradation products was monitored in the Hartbeespoort Dam catchment using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS/MS). Lake, river and groundwater were sampled from the Hartbeespoort Dam catchment over four seasons and the downstream Jukskei River was monitored during the winter season. Triazine herbicide concentrations in the Hartbeespoort Dam were in the order atrazine>simazine>propazine>ametryn>prometryn throughout the four seasons sampled. Triazine herbicide concentrations in the Hartbeespoort Dam surface water were highest in summer and gradually decreased in successive seasons of autumn, winter and spring. Terbuthylazine was the only triazine herbicide detected at all sampling sites in the Jukskei River, though atrazine recorded much higher concentrations for the N14 and Kyalami sites, with concentrations of 923 and 210ngL^-1 respectively, compared to 134 and 74ngL^-1 for terbuthylazine. Analytical results in conjunction with river flow data indicate that the Jukskei and Crocodile Rivers contribute the greatest triazine herbicide loads into the Hartbeespoort Dam. No triazine herbicides were detected in the fish muscle tested, showing that bioaccumulation of triazine herbicides is negligible. Atrazine and terbuthylazine metabolites were detected in the fish muscle with deethylatrazine (DEA) being detected in both catfish and carp muscle at low concentrations of 0.2 and 0.3ngg^-1, respectively. Desethylterbuthylazine (DET) was detected only in catfish at a concentration of 0.3ngg^-1. With atrazine herbicide groundwater concentrations being >130ngL^-1 for all seasons and groundwater ∑triazine herbicide concentrations ranging between 527 and 367ngL^-1, triazine compounds in the Hartbeespoort Dam catchment may pose a risk to humans and wildlife in light findings of endocrine and immune disrupting atrazine effects by various researchers.

Microalgae dual-head biosensors for selective detection of herbicides with fiber-optic luminescent O2 transduction

The microalgal species Dictyosphaerium chlorelloides (D. c.) was immobilized into porous silicone films and their photosynthetic activity was monitored with an integrated robust luminescent O2 sensor. The biosensor specificity towards a particular pesticide has been achieved by manufacturing a fiber-optic dual-head device containing both analyte-sensitive and analyte-resistant D. c. strains. The latter are not genetically modified microalgae, but a product of modified Luria-Delbrück fluctuation analysis followed by ratchet selection cycles. In this way the target herbicide decreases the O2 production of the analyte-sensitive immobilized strain without affecting the analyte-resistant population response; any other pollutant will lower the O2 production of both strains. The effect of the sample flow-rate, exposure time to the herbicide, biomass loading, biosensor film thickness, intensity of the actinic light, illumination cycle, and temperature on the biosensor response has been evaluated using waterborne simazine as test bench. The biosensing device is able to provide in situ measurements of the herbicide concentration every 180 min. The biosensor limit of detection for this herbicide was 12 μg L(-1), with a working range of 50-800 μg L(-1). The biosensor specificity to simazine has been assessed by comparing its response to that of isoproturon.

Detection limits can influence the interpretation of pesticide monitoring data in Canadian surface waters

Water quality monitoring programs rely on residue data that are frequently left censored, due to some observations occurring below the Method Detection Limit (MDL). Our objective was to determine the influence the MDL has on the interpretation of pesticide residues in surface waters. Water samples from tributaries in southern and central Ontario were collected by Environment Canada from 2003 to 2008 and were analyzed for 27 pesticides, with MDLs that averaged 7.02 ng(-1) L (range 0.39-25.1 ng(-1) L). We then simulated MDLs ranging from 25 to 1700 ng(-1) L, to determine the impact this would have on the reporting of pesticide concentrations and detections. The mean number of pesticides detected simultaneously declined with increasing, i.e. less sensitive MDLs, from 5.02 pesticides (native MDL) to 0.08 pesticides detected (MDL<1700 ng(-1) L). We compared the proportion of sites where pesticides were detected in surface waters under five MDL scenarios for 13 selected pesticides. The proportions decreased sharply with increasing MDLs. We calculated detection probabilities in an effort to compensate for higher MDLs using maximum likelihood; while adjusting for detection probabilities generally improved estimates of the presence of pesticides, as the MDLs increased the ability to compensate for detection probabilities deteriorated and became unviable at high MDLs. Depending on the method of substitution for observations below MDL (replacement with ½ × or 0 × MDL), the mean and median pesticide residues became increasingly over- and underestimated, respectively, at higher MDLs. Although monitoring programs that are focused on exceedences of water quality guidelines may not require low MDLs, the achievable goals of monitoring programs oriented towards other ecological and toxicological objectives may be limited by higher MDLs.

Development of an immunoassay for terbutryn: study of the influence of the immunization protocol

Heterologous immunization has proven to be useful to enhance the selectivity and specificity of catalytic antibodies. However, in the field of immunoassays, few studies have been done to establish how the immunization protocol influences the antibody characteristics. In the present study, we have developed an enzyme-linked immunosorbent assay (ELISA) for the detection of the pesticide terbutryn following a homologous and a heterologous immunization strategy. No significant differences have been observed between the immunization procedures regarding immunoassay sensitivity and selectivity. Thus, immunoassays with a limit of detection below the 25 ng/l established by current European regulations have been obtained with both immunization protocols. Initial studies have been performed to assess the applicability of these ELISAs to the analysis of real water matrixes.

Luminescence sensors applied to water analysis of organic pollutants--an update

The development of chemical sensors for environmental analysis based on fluorescence, phosphorescence and chemiluminescence signals continues to be a dynamic topic within the sensor field. This review covers the fundamentals of this type of sensors, and an update on recent works devoted to quantifying organic pollutants in environmental waters, focusing on advances since about 2005. Among the wide variety of these contaminants, special attention has been paid polycyclic aromatic hydrocarbons, pesticides, explosives and emerging organic pollutants. The potential of coupling optical sensors with multivariate calibration methods in order to improve the selectivity is also discussed.

Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode

The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H(2)O(2) (AO-H(2)O(2)), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O(2)-diffusion cathode for H(2)O(2) generation. The main oxidizing species are ()OH radicals formed at the BDD surface in all treatments and in the bulk from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2) in EF and PEF. A poor mineralization was attained using AO-H(2)O(2) by the slow oxidation of persistent by-products with ()OH at the BDD surface. The synergistic action of ()OH in the bulk enhanced the degradation rate in EF, although almost total mineralization was only achieved in PEF due to the additional ()OH generation and photolysis of intermediates by UVA irradiation. The effect of current, pH and herbicide concentration on the mineralization degree and mineralization current efficiency of each EAOP was examined. Desmetryne decay always followed a pseudo first-order kinetics, being more rapidly destroyed in the sequence AO-H(2)O(2)<EF<PEF. In all EAOPs, ammeline and cyanuric acid were identified as persistent heteroaromatic by-products and oxamic and formic acids were detected as generated carboxylic acids. The generation of cyanuric acid mainly by oxidation with ()OH at the BDD surface is the predominant path for desmetryne degradation. The initial nitrogen of desmetryne yielded NO(3)(-) ion in low proportion and NH(4)(+) ion in much lesser extent, suggesting that its major part was lost as volatile N-derivatives.

Preparation of antibodies and development of an enzyme immunoassay for determination of atrazine in environmental samples

An indirect competitive enzyme-linked immunosorbent assay (ELISA) has been developed and optimized for atrazine determination in soil at different depths (0-10, 10-20, and 20-30 cm) before and after 48 h of application, corn shoot and cow milk samples collected from Dina farm, Egypt. This assay was based on a specific polyclonal antibodies (PAb) raised by immunizing New Zealand rabbits with an immunogen prepared by coupling 3-{4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine-2-yl} thiopropanoic acid to bovine serum albumin (BSA) via N-hydroxysuccinimide (NHS) active ester method. The sensitivity (estimated as IC₅₀ value) was 17.5 μg mL⁻¹ with a detection limit of 0.1 ng mL⁻¹. The maximum atrazine concentration was found in soil especially in the deepest layer (325 and 890 μg kg⁻¹ before and after application, respectively). Atrazine concentration in corn shoot was 333.28, μg kg⁻¹ dry plant, while there was no detectable amount in milk. All samples screened by ELISA were validated by gas chromatography mass spectrometer procedure (GC/MS). Good correlation was achieved between the two methods (r = 0.997 for soil and 0.9814 for plant). This study demonstrates the utility and convenience of the simple, practical and cost-effective ELISA method in the laboratory for analysis of environmental samples. The method is ideal for the rapid screening of large numbers of samples in laboratories where access to GC/MS facilities, is limited or lacking.

Immuno-like assays and biomimetic microchips

Biomimetic assays with molecularly imprinted polymers (MIPs) are bound to be an alternative to the traditional immuno-analytical methods based on antibodies. This is due to the unique combination of advantages displayed by the artificial materials including the absence of animal inoculation and sacrifice, unnecessary hapten conjugation to a carrier protein for stimulated production, the possibility of manufacturing MIPs against toxic substances, excellent physicochemical stability, reusability, ease of storage, and recognition in organic media. If the selectivity and affinity of MIPs are increased, many more immuno-like assays will be developed using radioactive, enzymatic, colorimetric, fluorescent, chemiluminescent, or electrochemical interrogation methods. This chapter provides a comprehensive comparison between the bio- and biomimetic entities and their usage.

Microalgae fiber optic biosensors for herbicide monitoring using sol-gel technology

Three microalgal species (Dictyosphaerium chlorelloides (D.c.), Scenedesmus intermedius (S.i.) and Scenedesmus sp. (S.s.)) were encapsulated in silicate sol-gel matrices and the increase in the amount of chlorophyll fluorescence signal was used to quantify simazine. Influence of several parameters on the preparation of the sensing layers has been evaluated: effect of pH on sol-gel gelation time; effect of algae density on sensor response; influence of glycerol (%) on the membrane stability. Long term stability was also tested and the fluorescence signal from biosensors remained stable for at least 3 weeks. D.c. biosensor presented the lowest detection limits for simazine (3.6 microg L(-1)) and the broadest dynamic calibration range (19-860 microg L(-1)) with IC(50) 125+/-14 microg L(-1). Biosensor was validated by HPLC with UV/DAD detection. The biosensor showed response to those herbicides that inhibit the photosynthesis at photosystem II (triazines: simazine, atrazine, propazine, terbuthylazine; urea based herbicides: linuron). However, no significant increases of fluorescence response was obtained for similar concentrations of 2,4-D (hormonal herbicide) or Cu(II). The combined use of two biosensors that use two different genotypes, sensitive and resistant to simazine, jointly allowed improving microalgae biosensor specificity.