Electromembrane extraction - capillary zone electrophoresis for the quantitative determination of β-lactam antibiotics in milk samples

Three penicillin-based β-lactam antibiotics (benzylpenicillin, amoxicillin, and ampicillin) were extracted by electromembrane extraction (EME) and determined in the resulting extracts by capillary zone electrophoresis (CZE) with UV-Vis detection. The EME was optimized for the simultaneous clean-up of complex samples and preconcentration of the three antibiotics and employed 1-octanol as the organic phase interface (impregnated in the pores of a hollow fiber), acidified donor solution (pH 3), and phosphate buffer (pH 5.6) as the acceptor solution. The EMEs were carried out for 20 min at 300 V and constant stirring (750 rpm) of the donor solution. At the optimized EME-CZE conditions, the sensitivity of the analytical method was sufficient for the determination of the three β-lactam antibiotics in undiluted cow's milk at concentrations below the EU maximum residue limits (4 μg/L) in foodstuffs. The method was simple, rapid, and convenient and offered extraction recoveries of 13.5 - 87.3 %, enrichment factors of 23.6 - 152.8, repeatability (RSD values) better than 7.6 %, linear analytical response in the 1 - 100 μg/L (3 - 100 μg/L for benzylpenicillin) concentration range with correlation coefficients ≥ 0.9997, and limits of detection from 0.2 to 1.2 μg/L. The proposed analytical concept was used for the rapid control of milk quality (i.e. assessment of excessive use of antibiotics in dairy animals), moreover, it was further extended to the trace determination of β-lactam antibiotics in other complex samples, such as in wastewater.

Validation of the AnticFast® Beta-Lactams Rapid Test Kit for Detection of Beta-Lactams (Penicillins and Cephalosporins) in Raw Cow's Milk: AOAC Performance Tested MethodSM 032303

BACKGROUND

AnticFast® Beta-Lactams Rapid Test Kit is a qualitative two-step (2 min + 5 min) rapid lateral flow assay to detect β-lactam (penicillins and cephalosporins) antibiotic residues in raw commingled cow's milk.

OBJECTIVE

The method performance was evaluated according to Commission Decision 2002/657/EC, Commission Implementing Regulation 2021/808, and Community Reference Laboratories Residues Guidelines for the Validation of Screening Methods for Residues of Veterinary Medicines.

METHODS

The AnticFast Beta-Lactams Rapid Test Kit was evaluated for detection capability, selectivity, false-positive results, repeatability, robustness, suitability for various milk types and milk compositions, milks from various species, and test kit consistency and stability. Samples included milks spiked at concentrations bracketing the EU maximum residue limits (MRLs) for β-lactams as well as bulk farm and tanker milks.

RESULTS

The AnticFast Beta-Lactams Rapid Test Kit is specific for the detection of β-lactams in milk and does not detect compounds from other antibiotic families. Interference was seen with clavulanic acid, a β-lactamase inhibitor, which was expected. The test can detect all residues of β-lactams (penicillins and cephalosporins) present on the EU-MRL list for milk at their respective MRL except for desfuroylceftiofur and cephalexin, which were above the MRL. No false positives were detected in the 602 (300 blank farm and 302 tanker load) samples tested. Robustness testing indicated that the detection in heat-treated milk types may be slightly hampered. For substances with a detection capability well below the MRL, this interference does not cause problems since detection at MRL remains guaranteed, but care should be taken for substances with a CCβ at or near their MRL. Diminished sample flow was seen with reconstituted milk powder and blank ewes' milk, so sample flow should always be verified for these milk types.

CONCLUSIONS

Results of this validation show that the AnticFast Beta-Lactams Rapid Test Kit is a reliable test for rapid screening of raw cows' milk for residues of β-lactam antibiotics.

HIGHLIGHTS

AnticFast Beta-Lactams Rapid Test Kit is an easy, realiable, robust and highly specific test for screening of raw cows' milk for residues of penicillins and cephalosporins.

Utilization of colorimetric and atomic absorption spectrometric determination of aztreonam through ion pair complex formation

Three rapid and sensitive, colorimetric and atomic absorption spectrometric methods were developed for the determination of aztreonam. The proposed methods depend upon the reaction of cobaltthiocyanate (I) or reineckate (II) ions with the drug to form stable ion-pair complexes which extractable with chloroform. The greenish blue and pink color complexes are determined either colorimetrically at lambda(max) 625 and 525 nm for I and II reagents, respectively, or by atomic absorption spectrometry, directly using the organic extracted complex, or indirectly, using the supernatant. The three procedures are applied for the determination of aztreonam in pure and in pharmaceutical dosage forms applying the standard additions technique and the results obtained agreed well with those obtained by the official method.

High-performance liquid chromatography of alpha-amino acids and aztreonam on reversed phase columns with aqueous Cu2+ as eluent

Parameters affecting the separation of amino acids on different RP-HPLC columns were studied. Six amino acids were separated on Zorbax TMS, Zorbax CN, Zorbax ODS and Zorbax C8, using 1.8 x 10(-3) M copper sulphate at pH 4.1 as aqueous mobile phase. The best separation was shown by Zorbax TMS followed by Zorbax CN. The column performance was maintained by serial washing after 6 h continuous work with aqueous 10(-4) M disodium edetate, 10(-4) N sulphuric acid, water and gradient elution with aqueous methanol. The separation mechanism was interpreted. The method was applied for separation and quantification of aztreonam and L-arginine in Azactam vials.

The use of near infrared spectroscopy in the quality control laboratory of the pharmaceutical industry

The suitability of NIR spectroscopy as an alternative to several compendial test methods is discussed. Using ampicillin trihydrate as an example it is demonstrated that eight quality criteria are controlled by recording the NIR spectrum of a batch sample and calculating its Conformity Index.

[Synthesis and study of the properties of (3S-trans)-3-amino-4-methylmonobactamic acid]

The process for production of (3S-trans)-3-amino-4-methylmonobactamic acid (3-AMMA) was studied. It included transformation of L-threonine into amide, protection and activation of the functional groups, cyclization of the resulting beta-mesyloxyacylsulfomate into azetidinone followed by removal of the protecting group. For estimation of the completeness of the process separate stages and their optimization chromatography and spectroscopy were used. Stability, optical activity and chromatographic mobility of 3-AMMA under various conditions were studied. It was shown that solutions of 3-AMMA were rather stable in weak acid and neutral media and degraded at pH greater than 9.0. Control of this process was provided by circular dichroism.

beta-Lactam antibiotics: structural relationships affecting in vitro activity and pharmacologic properties

The essential nucleus of beta-lactam antibiotics is the four-membered ring, which can exist fused to form bicyclic ring structures or with moieties alone affixed to the four atoms. Penicillins, penems, carbapenems, and clavams have asymmetric centers at C-5 and C-6; cephalosporins and oxacephems have asymmetric centers at C-6 and C-7. Penicillins, cephalosporins, and monobactams require a beta-acylamino group for antimicrobial activity. Cephalosporins can undergo modification at C-3 and C-7 in both the alpha and beta position. Sulfur can be replaced with oxygen to achieve a more reactive nucleus. The most useful 7-beta-acylamino groups have been a 2-aminothiazolyl and an iminomethoxy or carboxypropyl group. Substitutions on the 7-alpha position increase beta-lactamase stability but decrease activity against staphylococci and Streptococcus pneumoniae. C-3 substitutions, particularly pyridinium groups, increase activity against Pseudomonas aeruginosa and Staphylococcus aureus. Carbapenems possess 6-alkyl substitutions in a trans configuration and inhibit aerobic, anaerobic gram-positive, and gram-negative bacteria. Monobactams are activated by sulfonic, phosphoric, or carboxyl groups, and their properties are related to the C-3-acyl side chain and their beta-lactamase stability to the C-4 grouping. beta-Lactamase inhibitors acylated by beta-lactamases can be penicillanic acid derivatives or clavulanates.

Intramolecular nucleophilic amino attack in a monobactam: synthesis and stability of (2S,3S)- 3-[(2R)-2-amino-2-phenylacetamido]-2-methyl-4-oxo-1- azetidinesulfo nic acid

The potentially orally bioavailable arylglycine-substituted monobactam, (2S,3S)- 3-[(2R)-2-amino-2-phenylacetamido]-2-methyl-4-oxo-1- azetidinesulfonic acid, was prepared as a crystalline solid. No significant antibacterial activity [i.e., MICs were greater than 128 (micrograms/mL)] was found when the monobactam was tested against Gram positive and Gram negative bacteria. Solution instability (greater than 2,000 times less stable than aztreonam) due to intramolecular nucleophilic amine attack on the beta-lactam is believed to be a contributing factor to the poor microbiological activity.