Flow injection enzyme immunoassay of atrazine herbicide in water

This paper describes an enzyme immunoassay in a flow system for detection of the atrazine herbicide. The IgG fraction was separated from rabbit anti-serum and immobilized in epoxy activated Poros support in a 10 μl column made of plexiglass. A mixture of sample/standard with horseradish peroxidase tracer was injected and adsorbed in the column. The enzyme activity of the bound tracer was detected by injecting H2O2 and 2,2′-azino-di-(3-ethylbenzthiazoline-6-sulphonic acid) substrate and detecting the product spectrophotometrically downstream at 405 nm. The column was regenerated in between each assay. The immobilized antibodies were stable giving negligible deactivation during one day. The assay was normally run with an analyte residence time of 2 min in the column which resulted in a detection limit of about 0.5 ng ml−1 and total assay time of about 15 min. If the sample volume, at the same flow rate, is increased to 800 μl, the detection limit can be reduced to about 0.02 ng ml−1 at the expense of an increased assay time (30 min, including regeneration).