Efficient elimination and detection of phenolic compounds in juice using laccase mimicking nanozymes

Residual phenols in the juice can cause turbidity and affect its sensory quality.Laccase is used to remove phenolic compounds from fruit juice s.In order to overcome the shortcomings of natural laccase instability and high cost,in this work,we prepared a laccase mimic enzyme based on copper ion and adenosine monophosphate(AMP-Cu nanozymes).At the same mass concentration(1 mg·ml^(-1)), the catalytic activity of the nanozyme is about 15 times that of laccase.The AMP-Cu nanozymes had a higher V_(max) and a lower Km than laccase.The laccase mimic enzyme had a good stability under the condition of 30-90 ℃ and pH> 6.It also maintained high catalytic activity at high salt concentrations and 9 days storage time.Furthermore,the AMP-Cu nanozyme s maintained an initial catalytic activity of about 80% after six consecutive cycles of reaction.The linear range of detection of phenolic compounds by AMP-Cu nanozymes was 0.1-100 μmol·L^(-1) with a detection limit of 0.033 μmol·L^(-1).The phenol removal rate of AMP-Cu nanozymes was much higher than that of laccase under different reaction times.When the reaction was performed for 5 h,the phenol removal rate of the fruit juice by AMP-Cu nanozymes was about 65%.The efficient removal of phenolic compounds from different juices by AMP-Cu nanozymes indicate s that they have good application prospect in the food juice industry.

Determination of phenolic whitening agents in cosmetics by micellar electrokinetic capillary chromatography with amperometric detection

A sensitive method for simultaneous determination of six phenolic whitening agents, including arbutin, phenol, resorcinol, hydroquinone, kojic acid, and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection （MECC-AD）. Effects of several factors, such as the pH value and concentration of running buffer, potential applied to the working electrode, separation voltage, and injection time were investigated to obtain optimum conditions for separation and detection. With a 75 cm long fused-silica capillary tube, well-defined separation of six phenolic compounds was achieved in 10 mmol/L SDS/40 mmol/L H3BO3-Na2B407 running buffer （pH 9.0）. Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients （r2） between 0.9985 and 0.9994, and the detection limit （S/N = 3） ranged from 0.04 p^g/mL to 0.45 p^g/mL. The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results, providing an alternative monitoring method for cosmetics safety regulation.