Determination of new β2-Agonists drugs by α1 glycoprotein affinity chromatographyglycoprotein affinity chromatography

The use of plasmatic acceptors as specific ligands in affinity chromatography cleanup of veterinary drugs from biological matrices

Bovine alpha(1)-acid glycoprotein (bAAG) and bovine serum albumin (BSA) are plasmatic acceptors working as carriers by the specific and reversible binding of several drugs in vivo. We synthesized affinity columns by coupling bAAG and BSA to an activated chromatographic support through their carbohydrate moieties, to preserve protein tertiary structure and, consequently, to improve the biological activity in vitro. The bAAG and BSA affinity columns were used to study the binding of acidic and basic drugs. Moreover, a purification strategy was developed for the cleanup of drug residues from biological matrices and foods, prior to screening and/or confirmatory analysis, on the basis of the specific molecular recognition between the protein and the drug. The aim of this work was to test the potency of bAAG- and BSA-based affinity chromatography to bind some veterinary drugs and purify them in the context of the official control of animal products. The efficiency of these homemade affinity columns in minimising matrix interference and in selective cleanup of different classes of substances was reported and discussed.

Identification of a probable new adrenergic agonist by nuclear magnetic resonance and mass spectrometry

In animal production, it is consolidated the synthesis and the illegal use of growth promoters of new generation, able to skip routine screening and confirmatory analysis. In this work it is reported the nuclear magnetic resonance (NMR) and the mass spectrometry identification of a probable new adrenergic drug found in a feed premix. The substance was selectively purified on alpha 1 acid glycoprotein affinity columns; then its structure was first achieved by recording the 13C NMR spectrum that gave the total number of carbons of the molecule, successively sorted by DEPT experiments into quaternary, CH, CH2, and CH3 groups. However, the complete assignments of all resonances were derived from the bi-dimensional analysis and the crucial indications from the 1H-13C reverse experiments. Further characterisation was performed by atmospheric pressure chemical ionisation both in positive and negative ion mode, matching the molecular ion and the fragmentation pattern with those of most recently described new adrenergic agonists. After the loss of a ter-butylic group, the structure shows an internal symmetry along with the presence of Chlorine clusters. The proposed formula of the compound, the 8,8'-diamino-9,9'-dichloro-1-terbutyl-1,1',4,4-tetrahydro-5H,5'H-2,2'-bi-1-benzazepine-5,5'-dione, partially resembles that of Zilpaterol for the presence of a heterocyclic ring; Further work is in progress to characterise the structure-activity relationship.

Development of a liquid chromatography/electrospray tandem mass spectrometry method for confirmation of chloramphenicol residues in milk after alfa-1-acid glycoprotein affinity chromatography

In this work we present a method for confirmatory analysis of chloramphenicol (CAP) in bovine and buffalo raw milk. CAP is extracted in acetonitrile and purified by affinity chromatography on an alpha-1-acid glycoprotein (AAG) column, then is identified and determined by ion-trap liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) analysis in the negative ion mode. CAP was identified at the minimum required performance limit (MRPL) of 0.30 ppb, by monitoring the [M-H]- ion and at least two product ions, meeting the qualitative and quantitative criteria set by the European Commission in Decision 2002/657/EC for confirmation of prohibited veterinary drugs. The trueness and within-day and between-day repeatability data are also reported. Moreover, the loading capacity of affinity columns towards CAP was tested. This method, based on the molecular recognition between drug and AAG during the purification step to improve sample cleanup, represents a quantitative and repeatable procedure for confirmatory analysis, and fits the requirements for the routine official control of CAP residues in raw milk.

Evaluation of MISPE for the multi-residue extraction of β-agonists from calves urine

Methods based on molecular recognition mechanisms for the clean-up of veterinary drugs and their residues, such as immuno-, receptor- and acceptor-affinity and molecularly imprinted polymers (MIPs), have been described as selective tools to improve the selectivity and the reliability of analytical results. In this work, we tested the extraction recovery performances of a MISPE column, designed for multi-residual clean-up of beta-agonists. For this purpose, 18 different samples of calf urine were spiked at 0.25, 0.50 and 1.00 ppb with pooled standard solutions of clenbuterol (Clen), tulobuterol (Tolu), isoxsuprine (Isox), brombuterol (Brom), mapenterol (Mape) and ractopamine (Racto) and analysed on two independent analytical sessions, on a LC-MS/MS ion trap detector. Averaged recoveries, constant for each molecule considered, were 64.6% for Racto, 63.0% for Salm, 59.9% for Form, 54.7% for Brom, 52.0% for Clen, 41.8% for Mape, 38.6% for Tolu and 34.5% for Isox, respectively. Reproducibility studies gave a CV < 11% at the 0.25 ppb level. The decision limit for the identification of the target drugs ranged from 0.01 ppb for mapenterol to 0.19 ppb for salmeterol, when considering one precursor, and two product ions as identification points. Such findings indicate that the choice of the appropriate molecule as template in the MIP preparation is the critical factor to guarantee a reliable analytical multi-residue approach for beta-agonists, despite the structural differences among molecules exploiting almost the same pharmacological effect.