Production of AmpC β-Lactamase and Development of a Competitive Array for Discriminative Determination of Cephalosporins in Milk.

In this study, AmpC β-lactamase of was expressed, and its intermolecular interaction mechanisms with 15 cephalosporins (CPs) were studied by using a molecular docking technique. Results showed that this enzyme mainly interacted with the β-lactam ring of these CPs, and the key contacting amino acids were Ser80 and Ser228. The AmpC β-lactamase was combined with 5 horseradish peroxidase-labeled conjugates to develop a direct competitive array on a microplate for determination of 15 drugs in milk.

Determination of 35 sulfonamides in pork by magnetic molecularly imprinted polymer-based dispersive solid-phase extraction and ultra-performance liquid chromatography photodiode array method.

Background: Sulfonamide residues in foods of animal origin are potential risks to consumer health, so it is very important to inspect them. Among the previously reported instrumental methods, the best method can only be used to determine at most 22 sulfonamides. Thus, an instrumental method capable of determining more sulfonamide species is desirable.

Determination of fluoroquinolones in chicken muscle by molecularly imprinted graphitic carbon nitride-based solid-phase extraction and ultra-performance liquid chromatography.

A graphitic carbon nitride was synthesised and nalidixic acid (NA) based molecularly imprinted microspheres (MIMs) were polymerised on its surface to create a composite material. After characterisation and evaluation of its absorption ability, the composite was used to prepare a solid-phase extraction (SPE) cartridge for purification of fluoroquinolones in chicken muscle, analysed by ultra-performance liquid chromatography. The cartridge showed high absorption capacities (378-559 μg) and high recoveries (92.

Synthesis of molecularly imprinted microspheres and development of a fluorescence method for detection of chloramphenicol in meat.

In this study, nitrobenzene was used as dummy template to synthesize a type of specific molecularly imprinted microspheres for chloramphenicol, and 4-nitroaniline was coupled with three fluorophores to synthesize three fluorescent tracers. Then a competitive fluorescence method was developed on a conventional microplate for detection of chloramphenicol in chicken and pork samples. This method contained only one sample-loading step, so one assay was finished within 30 min.

Development of a molecularly imprinted microspheres-based microplate fluorescence method for detection of amantadine and rimantadine in chicken.

In this study, molecularly imprinted microspheres of a type capable of recognising amantadine and rimantadine were first synthesised, and three fluorescent tracers based on dansyl chloride, fluorescein isothiocyanate and 5-carboxytetramethylrhodamine were also synthesised. These reagents were used to develop and optimise a direct competitive fluorescence method on conventional 96-well microplate for detection of the two analytes. Results showed that this method achieved simple operation procedure, rapid assay process (30 min), high sensitivity (limits of detection 0.

Magnetic graphene dispersive solid phase extraction-ultra performance liquid chromatography tandem mass spectrometry for determination of β-agonists in urine.

In this study, a magnetic graphene-based dispersive solid phase extraction method was first developed for extraction of β-agonists in urine. During the experiments, the absorbent amount, sample pH, extraction time, elution solution and elution time were optimized respectively. The optimized extraction method was finished within 10min, and showed high enrichment factors for 9 β-agonists (20-26 folds).