Stir Bar Coated With Dummy Molecularly Imprinted Polymers For Trace Analysis Of Bisphenol A In Food

Bisphenol A (BPA) is a kind of environmental hormones, which can causehealth hazards of human beings even at trace concentration. It is an important rawmaterial of the production of polycarbonate plastics and epoxy resins. Surroundingenvironment and food can be contaminated as a consequence of BPA migration froma variety of products contained BPA. Due to the low concentration level of BPAexisting in complicated environment, the separation and detection of trace BPAbecome an issue in highlight.Stir bar sorptive extraction (SBSE) is a novel sample pretreatment techniquedeveloped from solid phase microextraction (SPME). It gets advantages from SPME,simultaneously it possesses higher sample capacity and self-stirring characteristicwhich can avoid competitive adsorption from additional stirrer. At present,commercially available coatings of SBSE are limited, low selectivity and expensive,thus coatings have become the bottleneck of the development of SBSE. Recently, stirbars coated with molecularly imprinted polymers (MIPs) have been developed toextract polar or apolar analytes in complex samples. They possess high extractioncapacity and predetermined selectivity for a desired template, thus have greatdevelopment prospects.In this study, a dummy molecularly imprinted polymers coated stir bar(DMIPs-stir bar) was prepared for the separation and detection of trace BPAcommodiously.1. Preparation and evaluation of DMIPs-stir bar.In this paper，3,3’,5,5’-tetrabromobisphenol A (TBBPA) was used as dummy template to avoid the potential risk of leakage of imprinting molecules duringextracting BPA by MIPs-SBSE. The scanning electron microscopic image of thecoating presented a homogeneous surface with a thickness of about2.6μm. Fouriertransform infrared spectra of the coatings confirmed that the preparation ofDMIPs-stir bar was successful.The resulting DMIPs-stir bar showed the large sorption capacity and fastbinding kinetics for BPA. The saturated adsorption amount of the DMIPs-stir barwas32.1μg, which was3.0times over that of the non-imprinted polymers stir bar(NIPs-stir bar). And it only took1h for DMIPs-stir bar to achieve the sorptionequilibrium.The DMIPs-stir bar showed better selectivity than the bars coated withpolydimethylsiloxane (PDMS) or NIPs when used to extract BPA and its threeanalogues. Moreover, the recoveries of BPA with DMIPs-stir bar were stable even ifthe concentrations of each analogue increased, and this indicated the greatanti-interferences ability of DMIPs-stir bar.Besides, the extraction capacity of DMIPs-stir bar was investigated with aseries of BPA solutions, and NIPs-stir bar and PDMS-stir bar as a control.DMIPs-stir bar showed larger extraction amount than the bars coated with NIPs orPDMS.2. The application of the DMIPs-stir bar in food.The high-performance liquid chromatography (HPLC) combined with theDMIPs-stir bar was employed in the analysis of BPA in aqueous solution. The linearrange of BPA concentration in aqueous medium was0.0228-2.28ng/mL withcorrelation coefficient of0.9994and the detection limit was about6.84×10-3ng/mLbased on three times ratio of signal to noise.The method built was exploited to analyze BPA in tap water (0.069ng/mL). The spiked recoveries of BPA were95.3%with relative standard deviation less than8.8%(n=3).The standard addition method was used when the DMIPs-stir bar was applied tothe determination of trace BPA in milk. The amount of BPA in four milk samples was0.32、0.16、0.36and0.25ng/mL, respectively. The recoveries of the spiked BPA inmilk samples were between89.5-107.9%, and standard deviations were within10.7%(n=3). It showed the analytical method satisfied the need of analysis ofrealistic samples.