Abstract: The use of liposomes in immunoassays to provide encapsulated markers as signal enhancers is presented. The liposomes are spherical bi-layer vesicles that can entrap a water-soluble marker during their formation. The markers can be visible dyes, fluorescent dyes, chemi/bioluminescent substrates, electroactive species or enzymes. The liposome surface contains an analyte tag which binds to a cell surface antibody, the marker is then measured directly (visible dyes) or the liposome is lysed before measurement can be performed. The liposomes can be used in an enzyme-linked flow injection liposome immunoanalysis (FILIA) and a system for the detection of alachlor is outlined. The system used an immunoaffinity column containing immobilized antibodies and had a detection limit of 5 ppb alachlor. The liposome markers can also be mixed with sample and applied to plastic-backed nitrocellulose containing an antibody competition zone and a liposome capture zone to produce test strips, the color of the liposome capture zone being measured. The use of test strips for multi-analyte assays is discussed.

Abstract: The use of chemiluminescence for detection in FIA analyzer.s is discussed. Although chemiluminescence has been adopted by researchers for many years it has yet to find general acceptance in industry. Some of the possible reasons for this anomaly are discussed. Chemiluminescence has the following advantages: (i) there is the potential for lower detection limits due to the absence of noise and light scatter; (ii) there is a high selectivity because the number of possible reactions are limited; and (iii) the instrumentation is inexpensive.

Abstract: The high sample throughput of FIA makes it suitable for routine analysis as the measurements can be made at any time and are not restricted to kinetic considerations. This should make FIA ideal for clinical and environmental analysis although in practice it is not widely used in clinical analysis due to the development of dedicated analyzer.s. However, its portability, cost-effectiveness, easy manipulation, automation and its ability to be tailored to a particular problem combine to make FIA a powerful environmental tool. The wide range of FIA systems available together with its possible modifications and online coupling are discussed. The role of FIA in environmental analysis and its restrictions are briefly outlined.