Flow immunoassay for nonioinic surfactants based on surface plasmon resonance sensors.
A rapid, sensitive immunoassay based on a surface plasmon resonance sensor in a flow system for the determination of alkylphenol polyethoxylate (APEO) is described. The method is based on an indirect competitive reaction between an anti-APEO antibody in the sample solution and APEO immobilized on a sensor chip and APEO in the same sample solution. A sensor chip was prepared by immobilizing an APEO-horseradish peroxidase (APEO-HRP) conjugate on the thin gold film of the sensor chip. The adsorption constants for the APEO-HRP conjugate on the sensor chip and the surface density of the APEO-HRP adsorbed on the sensor chip at the saturated state were estimated to be 4.7 x 10(5) M(-1) and 5.0 x 10(-14) mol/mm(2), respectively, using a Langmuir adsorption isotherm equation and results from the adsorption experiments. The affinity constants for the immunocomplexes of the anti-APEO antibody with the APEO conjugate on the sensor chip and for APEO in the sample solution were estimated to 2.0 x 10(6) and 5.1 x 10(6) M(-1), respectively. A typical sigmoid calibration curve for APEO was obtained in the concentration range from 1 ppb to 1000 ppb. The detection limit, defined as the concentration of APEO, at which 85% of the sensor signal was observed, was ca. 10 ppb. The assay was applied to the determination of APEO in tap water in conjunction with a solid phase extraction pretreatment; APEO levels of approximately 50 ppt were successfully determined.
Tanaka
Mayumi
M
Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka, Japan.
Sakamoto
Kazuhira
K
Nakajima
Hizuru
H
Soh
Nobuaki
N
Nakano
Koji
K
Masadome
Takashi
T
Imato
Toshihiko
T
D000906:Antibodies; D004987:Ethers; D019855:Ethylene Glycol / Q000032:analysis* / Q000737:chemistry; D006735:Horseradish Peroxidase; D007118:Immunoassay / Q000379:methods*; D010636:Phenols / Q000032:analysis* / Q000737:chemistry; D020349:Surface Plasmon Resonance / Q000295:instrumentation; D013501:Surface-Active Agents / Q000032:analysis*
D000906:Antibodies; D004987:Ethers; D010636:Phenols; D013501:Surface-Active Agents; D006735:Horseradish Peroxidase; D019855:Ethylene Glycol