Evaluation of a Novel Malathion Immunoassay for Groundwater and Surface Water Analysis

Abstract

Malathion is an organophosphorus insecticide commonly used in crops and indoor applications. Negative effects of malathion on human health and ecosystems are of growing concern. In this work, novel malathion haptens are synthesized to develop an ELISA screening method. The immunoassay is based on a conjugate-coated format and shows a limit of detection of 0.11 ng/mL, an IC50 of 1.58 ng/mL, a dynamic range between 0.23 and 10.94 ng/ mL, and a cross-reactivity of <2% with structurally related compounds. The developed ELISA has been used to quantify malathion in groundwater and surface water samples. The good recoveries achieved and the agreement with those given by the GC-MS reference method indicate the potential of the assay for environmental monitoring of malathion in natural waters without purification or preconcentration steps. The effect of dissolved organic matter (humic acids) on the ELISA was evaluated, resulting in the conclusion that the immunoassay can be successfully performed in surface water samples with a humic acid content up to 10 mg/L, without sample pretreatment. Samples with a high humic acid content can be analyzed through ELISA after solid-phase extraction, eluting with acetone or acetonitrile.

Time-Resolved Fluoroimmunoassay as an Advantageous Approach for Highly Efficient Determination of Sulfonamides in Environmental Waters

“…As a widely existing matrix substance in natural water, humic acids are heterogeneous, hardly separable mixtures of polyelectrolytes with varying molecular sizes, substructures, and functionalities. Most inorganic cations and organic compounds are associated with humic acid, which could influence the immunoassay by interfering with the association of analytes with antibodies and the measurement of fluorescence signals (24). Figure 3B indicates that an increase of humic acid concentration to 100 mg/L DOC (dissolved organic carbon) has no significant effect on the TRFIA of SAs, suggesting the interference from humic acid is negligible because in real environmental waters the humic acid concentrations are far below 10 mg/L DOC.…”

Novel hapten synthesis for antibody production and development of an enzyme-linked immunosorbent assay for determination of furaltadone metabolite 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ)

“…For each condition, the standard curves for NPAMOZ were established (n=3) and the maximum absorbance value (B 0 ) as well as the concentration of analyte that produces a 50% decrease in B 0 (IC 50 ) were obtained. The B 0 /IC 50 ratio was used to estimate the effect of a certain factor on the ciELISA performance, the higher ratio indicating the higher sensitivity response to the condition being tested [29,30]. As shown in Fig.…”

Sensitive immunoassay for simultaneous determination of tetrabromobisphenol A bis(2-hydroxyethyl) ether and tetrabromobisphenol A mono(hydroxyethyl) ether: An effective and reliable strategy to estimate the typical tetrabromobisphenol A derivative and byproduct in aquatic environments

“…B 0 /IC 50 was selected as important criteria to evaluate the performance of the immunoassays (Brun et al, 2005;Korpimaki et al, 2004). In addition, IC 50 and B 0 also were regarded as primary physicochemical factors to estimate the performance of the methods (Li et al, 2014).…”