John O'Mahony

Current trends in sample preparation for growth promoter and veterinary drug residue analysis.

A comprehensive review is presented on the current trends in sample preparation for the isolation of veterinary drugs and growth promoters from foods. The objective of the review is to firstly give an overview of the sample preparation techniques that are applied in field. The review will focus on new techniques and technologies, which improve efficiency and coverage of residues. The underlying theme to the paper is the developments that have been made in multi-residue methods and particularly multi-class methods for residues of licensed animal health products, which have been developed in the last couple of years. The role of multi-class methods is discussed and how they can be accommodated in future residue surveillance.

Theoretical and computational strategies for rational molecularly imprinted polymer design

The further evolution of molecularly imprinted polymer science and technology necessitates the development of robust predictive tools capable of handling the complexity of molecular imprinting systems. A combination of the rapid growth in computer power over the past decade and significant software developments have opened new possibilities for simulating aspects of the complex molecular imprinting process. We present here a survey of the current status of the use of in silico-based approaches to aspects of molecular imprinting. Finally, we highlight areas where ongoing and future efforts should yield information critical to our understanding of the underlying mechanisms sufficient to permit the rational design of molecularly imprinted polymers.

Structure and dynamics of monomer-template complexation: an explanation for molecularly imprinted polymer recognition site heterogeneity.

We here present the first simulation of a complete molecularly imprinted polymer prepolymerization system. Molecular dynamics studies were performed for a system comprising a total of 1199 discrete molecules, replicating the components and concentrations employed in the corresponding polymer synthesis. The observed interactions correlate well with results obtained from (1)H NMR spectroscopic studies. Comparison with simulations performed in the absence of cross-linking agent (ethylene dimethacrylate) demonstrated its significance in the formation of ligand recognition sites. Moreover, the influence of events such as template-template (bupivacaine) and monomer-monomer (methacrylic acid) self-association, porogen-template interactions, and template conformational variability was revealed. The template recognition capacity of the modeled polymer system was verified by synthesis of imprinted and reference polymers and subsequent radioligand binding analysis. Collectively, through a series of statistical analyses of molecular trajectories in conjunction with spectroscopic data it was demonstrated that an ensemble of complex structures is present in the prepolymerization mixture and that this diversity is the basis for the binding site heterogeneity observed in molecularly imprinted polymers (MIPs) prepared using the noncovalent strategy.

A review of coccidiostats and the analysis of their residues in meat and other food

Coccidiostats are used in the control of protozoan infections in different food producing animals. They are most widely used as feed additives in intensively reared species such as pigs and poultry to maintain animal health and in some cases enhance feed conversion. However, a number of these drugs are used in the control of infections in beef and lamb production. Coccidiostat residues have been frequently reported in meat and eggs in a number of countries since the late 1990s. This has prompted increased research and surveillance of coccidiostat residues in food. This paper reviews the various coccidiostat agents used in animal production, including their chemical properties, mode of action and activity. Legislation concerning coccidiostats, limits for residues in food, monitoring and occurrence of residues in food is discussed. Methods for residue determination in food, including screening and physicochemical methods are discussed in depth. The paper concludes with a synopsis of the current state of coccidiostat residue analysis and future perspectives.

Design and implementation of an imprinted material for the extraction of the endocrine disruptor bisphenol A from milk.

This paper describes the determination of bisphenol A (BPA) in milk samples, using a novel molecularly imprinted polymer. The imprinted polymer was developed using a rational design approach, and pre-polymerization interactions were investigated using molecular dynamics simulations and X-ray crystallography. A hydroquinone-imprinted polymer was used for solid phase extraction (SPE) clean-up of samples. BPA was quantified by high performance liquid chromatography (HPLC) and fluorescence (FLD) detection. Following validation, the method described was capable of determining bisphenol A in milk down to a limit of detection of 1.32μgkg(-1). The method was applied to a survey (n=27) of commercial milk products; BPA was detected in one of the samples, at a level of 176μgkg(-1). Test results were confirmed by a parallel UHPLC-MS/MS analytical method. This demonstrates the utility of the hydroquinone-imprinted polymer for application to selective sample clean-up and analysis of bisphenol A in milk, avoiding possible detrimental affects associated with template bleeding and without the need for expensive or difficult-to-obtain template.