Glyphosate immunosensor. Application for water and soil analysis

Ion chromatography/inductively coupled plasma mass spectrometry for simultaneous determination of glyphosate, glufosinate, fosamine and ethephon at nanogram levels in water

This paper describes the first approach that simultaneously quantifies four polar, water-soluble organophosphorus herbicides, i.e., glyphosate, glufosinate, fosamine and ethephon, at nanogram levels in environmental waters. The target herbicides were separated completely by ion chromatography (IC) on a polymer anion-exchange column, Dionex IonPac AS16 (4.0 mm x 250 mm), with 30 mM citric acid flowing at 0.70 mL min(-1) as the eluent. On-line inductively coupled plasma mass spectrometry (ICP-MS) using a quadrupole mass spectrometer was employed as a sensitive and selective detector of the effluents. Various parameters affecting the separation and detection were systematically examined and optimized. Detection limits of the herbicides achieved with the proposed IC/ICP-MS method were 1.1-1.4 microg L(-1) (as compound) based on a 500-microL sample injection. Matrix anions, metal ions, phosphate, polyphosphates, non-polar and other polar organophosphorus pesticides showed no interference. The developed method was validated using reservoir water, treated water and NEWater samples spiked at the level of 10-25 microg L(-1) with satisfactory recoveries (95-109%). It is applicable to the simultaneous determination of microg L(-1) concentrations of the herbicides in polluted water.

Optical immunosensors for environmental monitoring: How far have we come?

Immunosensing has proved to be a very interesting research area. This review discusses what has actually been achieved in the field of optical immunosensing for environmental screening, and what still needs to be done. The review is presented from a practical point of view. In terms of the basic design of the immunosensor, there is a trend towards decreasing assay time; indeed, this has been reduced from 15-20 minutes to less than 5 minutes. Another goal is to simplify the manifold, and label-free approaches combining indirect assay formats and the detection of antibody binding are popular. Rapid displacement assays have also been investigated thoroughly. In terms of some important features of immunosensing devices, the reusability of the sensing element has been studied in great depth, and working lifetimes of more than five hundred assays can now be found for all assay formats. Multianalyte assays are now being investigated, and current systems are able to monitor 2-3 target compounds, although this number is set to increase greatly (to >30) in the near future. In this sense, an increasing number of publications can be found on microarrays intended for multianalyte determinations. The application of immunosensing to real situations is the main challenge. Immunosensors are barely commercialized and are yet to be established as research or routine tools, due to a lack of validated protocols for a wide range of sample matrices. Regarding compounds considered as analytes, some significant pollutants such as dioxins or pharmaceuticals are rarely chosen as targets, although the current tendency is towards a broader spectrum of analytes. New immunoreagents should be raised for these compounds, for use in immunosensors that can be used as screening tools.

Identification of cognate ligands for the Escherichia coli phnD protein product and engineering of a reagentless fluorescent biosensor for phosphonates

The Escherichia coli phnD gene is hypothesized to code for the periplasmic binding component of a phosphonate uptake system. Here we report the characterization of the phosphonate-binding properties of the phnD protein product. We find that PhnD exhibits high affinity for 2-aminoethylphosphonate (5 nM), the most commonly occurring natural phosphonate produced by lower eukaryotes, but also binds several other phosphonates with micromolar affinities. A significant number of man-made phosphonates, such as insecticides and chemical warfare agents, are chemical threats and environmental pollutants. Consequently, there is an interest in developing methods for the detection and bioremediation of phosphonates. Bacterial periplasmic-binding proteins have been utilized for developing reagentless biosensors that report analytes by coupling ligand-binding events to changes in the emission properties of a covalently conjugated environmentally-sensitive fluorophore. Several PhnD conjugates described here show large changes in fluorescence upon binding to methylphosphonate (MP), with two conjugates exhibiting up to 50% decrease in emission intensity. Since MP is the final degradation product of many nerve agents, these PhnD conjugates can function as components in a biosensor system for chemical warfare agents.