The Electrochemical Detection of Penicillins in Milk

Nanomaterial-based electrochemical sensors and biosensors for the detection of pharmaceutical compounds

The surging growth of the pharmaceutical industry is a result of the rapidly increasing human population, which has inevitably led to new biomedical and environmental issues. Aside from the quality control of pharmaceutical production and drug delivery, there is an urgent need for precise, sensitive, portable, and cost-effective technologies to track patient overdosing and to monitor ambient water sources and wastewater for pharmaceutical pollutants. The development of advanced nanomaterial-based electrochemical sensors and biosensors for the detection of pharmaceutical compounds has garnered immense attention due to their advantages, such as high sensitivity and selectivity, real-time monitoring, and ease of use. This review article surveys state-of-the-art nanomaterials-based electrochemical sensors and biosensors for the detection and quantification of six classes of significant pharmaceutical compounds, including anti-inflammatory, anti-depressant, anti-bacterial, anti-viral, anti-fungal, and anti-cancer drugs. Important factors such as sensor/analyte interactions, design rationale, fabrication, characterization, sensitivity, and selectivity are discussed. Strategies for the development of high-performance electrochemical sensors and biosensors tailored toward specific pharmaceuticals are highlighted to provide readers and scientists with an extensive toolbox for the detection of a wide range of pharmaceuticals. Our aims are two-fold: (i) to inspire readers by further elucidating the properties and functionalities of existing nanomaterials for the detection of pharmaceuticals; and (ii) to provide examples of the potential opportunities that these devices have for the advanced sensing of pharmaceutical compounds toward safeguarding human health and ecosystems on a global scale.

High-performance liquid chromatographic separation and electrochemical detection of cephalosporins

Pulsed amperometric detection (PAD) is useful for detection of cephalosporins following separation on a C18 column using an acetate buffer solvent with a small percentage of organic modifier. Under these conditions, the indirect PAD mode worked better than direct PAD, with IPAD outperforming both. A gradient program was demonstrated that allowed separation and sensitive electrochemical detection of eleven different cephalosporins with widely differing side chain structures. The cephalosporins could be detected to sub-micromolar levels with this separation. Applications of the method for quantitation of pharmaceutical formulations and for monitoring cephalexin in porcine serum were demonstrated. To improve the detectability of cephalexin, an on-column concentration scheme using separate concentration and elution solvents was applied to porcine serum.

Chromatographic methods of analysis of antibiotics in milk

The widespread use of antibiotics in dairy cattle management may result in the presence of antibiotic residues in milk. While rapid screening tests are commonly used to detect the presence of antibiotics in milk, more accurate chromatographic methods are required by government regulatory agencies to identify and confirm the identity and quantity of antibiotic present. This paper review recent developments in the chromatographic determination of antibiotic residues in milk.

Multiresidue determination of beta-lactam antibiotics in milk and tissues with the aid of high-performance liquid chromatographic fractionation for clean up

Screening of milk shipments for beta-lactam antibiotic residues is mandatory in the USA and is widely used in other countries. Interpretation of positive screening test results has been difficult. Only six beta-lactam antibiotics are approved for use in food-producing animals in the USA but many others are used in other countries. A multiresidue procedure was developed for identification and quantitation of unknown beta-lactam antibiotics. The residues were extracted with acetonitrile and tetraethylammonium chloride. The extract was concentrated by evaporation and filtered. The concentrated extract was then loaded onto an HPLC column in 100% 0.01 M KH2PO4 and eluted with an acetonitrile gradient. Fractions corresponding to analytes of interest were collected and tested for antibiotics using rapid milk screening tests. Fractions testing positive were analyzed by HPLC. The identity of beta-lactams was confirmed by treating a replicate with beta-lactamase.

Determination of penicillins in animal tissues at trace residue concentrations: II. Determination of amoxicillin and ampicillin in liver and muscle using cation exchange and porous graphitic carbon solid phase extraction and high-performance liquid chromatography

A method for the determination of the basic penicillins, amoxicillin and ampicillin, in animal tissue is described. The method used aqueous extraction with tungstate to remove proteins followed by cation exchange solid phase extraction (SPE) clean-up. This extract was further purified using porous graphitic carbon (PGC) SPE. Extracted residues were derivatized with acetic anhydride followed by triazole/mercuric chloride prior to reversed phase HPLC with UV determination at 325 nm. At the Maximum Residue Limit of 50 micrograms/kg in fortified cattle muscle validation gave mean recoveries for amoxicillin of 57% and 50% on two different days with relative standard deviations of 19% and 15% respectively. For ampicillin the recoveries were 72% and 59% with relative standard deviations of 15% and 19% respectively.

High-performance liquid chromatographic determination of penicillins by means of automated solid-phase extraction and photochemical degradation with electrochemical detection

An automated precolumn exchange system for on-line solid-phase extraction (OPS-2) coupled to liquid chromatography with photochemical degradation and electrochemical detection was used for the determination of residual amounts of penicillin G, penicillin V, oxacillin, cloxacillin and dicloxacillin. A 5-10-fold increase in sensitivity was obtained when compared with direct UV detection of penicillins at 225 nm. The system is recommended for samples that have received an immunoaffinity clean-up. Analysis of bovine muscle tissue indicated, however, that this procedure could also be suitable for the determination of penicillin G at its maximum residue limit of 50 micrograms/kg even with conventional solvent partitioning for the first clean-up steps.