Development of a molecularly imprinted polymer-matrix solid-phase dispersion method for selective determination of ß-estradiol as anabolic growth promoter in goat milk.

A simple, fast, and sensitive method for determination of 17 ß-estradiol (E2) in goat milk samples has been developed by combining selective molecularly imprinted matrix solid-phase dispersion (MIP-MSPD) and liquid chromatography with diode-array detection (DAD). The molecularly imprinted polymer was synthesized by use of 17ß-estradiol as template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker monomer, azobisisobutyronitrile as initiator, and acetonitrile as porogen, and was used as selective solid support for matrix solid-phase dispersion. The selected dispersant had high affinity for E2 in the goat milk matrix and the extract obtained was sufficiently clean for direct injection for HPLC analysis without any interferences from the matrix. The proposed MIP-MSPD method was validated for linearity, precision, accuracy, decision limit (CCα) and detection capability (CCß), in accordance with European Commission Decision 2002/657/EC criteria. Linearity ranged from 0.3-10 µg g(-1) (correlation coefficient r(2) > 0.999). Mean recovery of E2 from goat milk samples at different spiked levels was between 89.5 and 92.2%, with RSD values within 1.3-2%. CCα and CCß values were 0.36 and 0.39 µg g(-1), respectively. The developed MIP-MSPD method was successfully applied to direct determination of E2 in goat milk samples.

Selective solid-phase extraction of ethynylestradiol from river water by molecularly imprinted polymer microcolumns.

A selective on-column molecularly imprinted solid-phase extraction (MISPE) for ethynylestradiol (EE2) from water samples was developed. Following a non-covalent molecular imprinting approach, two molecularly imprinted polymers (MIPs) have been synthesised using methacrylic acid (MAA) as functional monomer, ethyleneglycol dimethacrylate (EGDMA) as crosslinker and EE2 as template, in two different polymerisation solvents (acetonitrile or toluene). The optimisation of the on-column MISPE conditions for the selective rebinding of the EE2 resulted in a flow rate of 2.3 mL min(-1) and volumes of 1 mL toluene and 1.5 mL methanol-acetic acid (9:1) for washing and elution steps, respectively. The selectivity of the imprinted polymer towards several related estrogens such as estriol (E3), estrone (E1) and estradiol (E2) was evaluated. The recovery of EE2 from a 50-mL spiked river-water sample was 75% when the optimised on-column MISPE was applied.

A new molecularly imprinted polymer for the on-column solid-phase extraction of diethylstilbestrol from aqueous samples.

The estrogenic compound diethylstilbestrol (DES) is widely studied because of its potential endocrine disruption effects. The prohibition of the use of diethylstilbestrol as a growth promoter has not been enough to ensure the total disappearance of this compound from environmental matrices. Due to the low levels of DES present in the environment, preconcentration and clean up methods are necessary for its analysis. This paper describes the synthesis and use of a molecularly imprinted polymer (MIP) as sorbent for on-column solid-phase extraction of DES from aqueous samples. The selectivity of the DES-MIP was evaluated towards several selected estrogens such as hexestrol (HEX), estrone (E1), estriol (E3), estradiol (E2) and ethynylestradiol (EE2). HPLC-DAD was used to quantify all analytes at 230-nm wavelength. The method has been successfully applied to the analysis of DES in spiked river and tap water samples, with recoveries of 72% and 83% respectively.

Permanently oriented antibody immobilization for digoxin determination with a flow-through fluoroimmunosensor.

This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples.