David P. Herzog

Performance characteristics of a novel magnetic‐particlebased enzyme‐linked immunosorbent assay for the quantitative analysis of atrazine and related triazines in water samples

The performance characteristics of a magnetic‐particle‐based solid‐phase enzyme‐linked immunosorbent assay (ELISA) requiring no sample preparation for the quantification of atrazine and related triazines in groundwater samples is described. Water samples and HRP‐labeled atrazine are incubated with the antibody‐coupled solid phase for 15 min. A magnetic field is then applied to the solid phase to wash and remove free HRP‐labeled atrazine and to ensure the removal of potential interfering substances. After 20 min of color development using hydrogen peroxide/TMB, the reaction is stopped by the addition of acid. Photometric analysis of the final colored reaction was made using a specially designed microprocessor‐controlled photometer with extensive data reduction capability. The assay was found to be free of interferences when challenged with high concentrations of inorganic ions and a wide variation in sample pH. Sensitivity of the assay was 50 ppt based on 95% B/B0. Assay precision demonstrated coefficients...

Determination of pentachlorophenol in water and soil by a magnetic particle-based enzyme immunoassay.

A competitive enzyme immunoassay using specific pentachlorophenol (PCP) antiserum covalently coupled to a magnetic particle solid phase has been developed for the detection of PCP in water and soil. The immunoassay allows the quantification of PCP from 100 ppt(parts per trillion, ng/L) in water and 100 ppb (parts per billion, mg/L) in soil. Spike recovery from water samples with no sample pretreatment and from various soil types following a simple extraction technique averaged 105% and 94%, respectively. The method compares favorably with GC/MS and HPLC measurements in water (r=0.980) and soil (r=0.996) samples.

Development and evaluation of a magnetic particle based enzyme immunoassay for aldicarb, aldicarb sulfone and aldicarb sulfoxide

Abstract A magnetic particle based solid-phase enzyme linked immunosorbent assay (ELISA) for the determination of parts per billion levels of aldicarb and its sulfoxide and sulfone metabolites in water was developed. Sensitivity is estimated at 250 ppt based on a 90% B/Bo with results available in less than one hour. Photometric analysis of the final colored reaction was made using a specially designed microprocessor controlled photometer with extensive data reduction capability. Assay interference was not seen over a wide pH range and with high concentrations of inorganic ions. Results were shown to qualitatively correlate with HPLC and GC using a positive cutoff of 0.5 ppb. Quantitative comparisons were difficult due to the variable reactivities of aldicarb and its metabolites. This rapid, convenient method would be an excellent screening tool for large numbers of water samples with the potential for application in other matrices, as illustrated by a study on lemonade.

Detection of procymidone in wine and grapes by a magnetic particle‐based enzyme immunoassay

A competitive enzyme immunoassay has been developed to detect procymidone in wine at the parts per billion level (ppb) without sample dilution or extraction. This immunoassay utilizes magnetic particles as the solid phase which allows for the precise addition of antibody and rapid reaction kinetics. The sensitivity of the assay based on 90% B/Bo is 0.8 ppb in wine. The recovery of 30 wine samples spiked with four levels of procymidone averaged 104%. The specificity of the polyclonal antibody used allows for the quantitation of procymidone in the presence of other commonly applied fungicides including vinclozolin, iprodione, captan and carbendazim. Correlation of 27 wine samples by the immunoassay method and a GC/ ECD procedure yielded a regression (r) of 0.972. Recovery studies indicate that this immunoassay can also be used to detect procymidone on grapes. The average recovery of procymidone from grapes was 113%.