Simple and Sensitive Electrochemiluminescence Method for Determination of Bisphenol a Based on its Inhibitory Effect on the Electrochemiluminescence of Luminol

Signal-on electrochemiluminescence aptasensor for bisphenol A based on hybridization chain reaction and electrically heated electrode

A simple and sensitive electrochemiluminescence (ECL) aptasensor has been developed for bisphenol A (BPA) detection. The capture DNA (CDNA) was modified on the heated indium-tin-oxide (ITO) working electrode surface firstly and then hybridized with BPA aptamer to form double strand DNA (dsDNA). The presence of target can cause the releasing of aptamer from the electrode surface since the aptamer prefers to switch its configuration to combine with BPA. Subsequently, the free CDNA will induce hybridization chain reaction (HCR) to produce long dsDNA on the electrode surface. Ru(phen)₃²⁺ can integrate into the grooves of dsDNA to act as an ECL reagent, thus enhanced ECL signal can be detected. The temperature control during the processes of target recognition and HCR were realized through the heated electrode instead of the bulk solution heating. Furthermore, the performance of the ECL aptasensor can be further enhanced at elevated electrode temperature. Under the optimized conditions, the ECL intensity of the system has a linear relationship with the logarithm of BPA concentration in the range of 2.0 pM-50 nM. The limit of detection (LOD) at 55 °C (electrode surface temperature) was calculated to be 1.5 pM, which was approximately 6.5-fold lower than that at 25 °C. The proposed biosensor has been applied to detect the BPA in drink samples with satisfactory results.

Spectrophotometric and high performance liquid chromatographic methods for sensitive determination of bisphenol A

A new spectrophotometric method for the determination of trace amounts of bisphenol A based on a diazotization-coupling reaction was developed. In acidic solution, clenbuterol was first diazotized with sodium nitrite, then coupled with bisphenol A to from an azo-compound [I] in NH3-NH4Cl buffer, which shows a maximum absorption at 410 nm. The effects of the amount of sodium nitrite, diazo reaction time, the amount of clenbuterol, coupling reaction time and coupling reaction temperature have been examined. Under the optional conditions, the determination of the linear range of bisphenol A is 0.24-8.4 μg/mL, correlation coefficient is 0.9905 and detection limit of this method is 0.15 μg/mL. The spectrophotometric method is simple, rapid, high sensitivity with better accuracy. High performance liquid chromatography (HPLC) technique combined with this new spectrophotometric method has been also developed for the measurement of bisphenol A. The analysis was achieved on a C18 column using water and methanol as a mobile phase and the detection was done spectrophotometrically at 410 nm. These reported methods were applied to the determination of bisphenol A in hot water in contact with commercially available table-water bottle samples.

Determination of malachite green residues in fish using a highly sensitive electrochemiluminescence method combined with molecularly imprinted solid phase extraction

An electrochemiluminescence (ECL) inhibition method combined with molecularly imprinted solid phase extraction (MISPE) was developed for quantitative determination of malachite green (MG) residues in fish. It was found that MG could strongly inhibit the ECL signal of luminol. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of MG was in good linear relationship over a concentration range from 20 to 5000 ppt. The method detection limit was found to be about 6 ppt. Molecularly imprinted polymers (MIPs) were synthesized as solid phase extraction (SPE) sorbents, and MISPE was used for the selective extraction and purification of MG. By carrying out the oxidation reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), which could convert leucomalachite green (LMG) into MG, this method was successfully applied to determine MG residues in fish. A possible mechanism for the quenching effects of MG on luminol was also proposed.