title: Integration of liquid chromatography with immunoassay: an approach combining the strengths of both methods.
abstract: The integration of liquid chromatography (LC) with immunochemical detection combines the superior separation power of LC and the sensitivity and specificity of immunoassays. This approach is shown with 3 LC systems (Perkin-Elmer, C18 RP, 4.6 mm; Varian, C18 RP, 1 mm microbore; Michrom, C18 RP, 1 mm microbore) integrated with an enzyme-linked immunosorbent assay (ELISA) selective for five 4-nitrophenols. The nitrophenols were separated with the 3 LC systems with isocratic runs of 15 to 20 min. Microbore LC separation showed a 10-20 times reduction in solvent amount compared to conventional separation. LC-immunoassay was about 8- to 10-fold more sensitive compared with LC with UV detection. Integrated LC-immuno-assay proved to be a very selective method when 2-methylphenol was injected with an equimolar mixture of 2-amino-4-nitrophenol and 3-methyl-4-nitrophenol; 2-methylphenol does not cross-react with the serum used. Only 2 peaks could be seen in the detection, even when 2-methylphenol was present in very high amounts (3000 pmol). Further, the ELISA-LC detection proved to be selective and sensitive for complex matrixes. 2-Amino-4-nitrophenol was clearly identified in spiked extracts of soil and plant, even when a very small amount (2.4 ng) was injected. Although LC-immunoassay is more labor intensive than LC with UV detection, it offers great advantages in multiresidue analysis and is generally applicable for peak confirmation.
authors.affiliation: University of California, Department of Entomology, Davis 95616.
authors.forename: P M
authors.initials: PM
authors.lastname: Krämer
authors.forename: Q X
authors.initials: QX
authors.lastname: Li
authors.forename: B D
authors.initials: BD
authors.lastname: Hammock
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods* / Q000706:statistics & numerical data; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods* / Q000706:statistics & numerical data; D009596:Nitrophenols / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D012997:Solvents
chemical_list: D009596:Nitrophenols; D012997:Solvents