Convenient solid phase extraction of cephalosporins in milk using a molecularly imprinted polymer

In this paper, a molecularly imprinted polymer (MIP) for cephalosporin molecules (cephalexin (CFL) and cephapirin (CFP)), was prepared by non covalent molecular imprinting approach and applied to solid phase extraction (SPE). For MIP synthesis, a tributylammonium cefadroxil salt (TBA-CFD) was used as template with methacrylic acid and ethylene glycol dimethacrylate as monomer and cross-linker, respectively, in acetone-methanol 92/8 (v/v) mixture. The selectivity of MIP versus non imprinted polymer (NIP) was confirmed for CFL, CFD and CFP in standard solutions as well as in milk samples. The efficiency of the synthesized MIP was evaluated by means of the application of the proposed MIP-SPE procedure to spiked milk samples previous to the HPLC method for the detection of cephalosporins. The MIP-SPE recoveries were higher than 60% for the three target analytes in spiked milk.     

Quantitative analysis of ochratoxin A in wine and beer using solid phase extraction and high performance liquid chromatography-fluorescence detection

A reliable and accurate method is described for the quantitative analysis of ochratoxin A (OTA) in wine and beer. The method involves the use of disposable non-polar polymeric and aminopropyl solid-phase extraction cartridges to isolate the mycotoxin from alcoholic beverages. Extracts were subsequently analysed using reverse-phase high-performance liquid chromatography-fluorescence detection with post column ammoniation to improve the limit of detection. The precision of the method determined at three levels in both wine and beer was less than 5% (RSD). Standard addition studies in both wine and beer showed that the recovery of OTA varied between 90 and 106% over a concentration range of 0.016-1.284 µg l^-1. The detection and quantification limits were shown to be better than 0.004 (S/N = 3) and 0.016 µg l^-1 (S/N = 10) for both beer and wine.     

A molecularly imprinted electrochemical sensor based on a MoS2/peanut shell carbon complex coated with AuNPs and nitrogen-doped carbon dots for selective and rapid detection of benzo(a)pyrene

In this study, a new electrochemical strategy based on the fabrication of a molecularly imprinted sensor onto a MoS₂-loaded peanut shell carbon complex with gold nanoparticles (AuNPs) and nitrogen-doped carbon dots (N-CDs) was proposed for the detection of benzo(a)pyrene (BaP). Molecularly imprinted polymer (MIP) films were prepared by cyclic voltammetry (CV) using 2-mercaptobenzimidazole (2-MBI) as a functional monomer in the presence of BaP. The surface morphologies, structural characteristics and electrochemical properties of the obtained MIP/AuNPs/N-CDs/PSBC/MoS₂/GCE were investigated via scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), UV–Vis spectrometry, fluorescence spectrometry, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimised conditions, the detection range of the electrode towards BaP varied from 5 nM to 20 μM with a detection limit of 1.5 nM. The prepared electrochemical sensor also exhibited good stability, relevant reproducibility and high selectivity. The application of the sensor in the actual analysis of edible oil samples showed promising results, thereby being relevant as a biomimetic sensing platform for the detection of chemical hazards in food and environment.