Determination of penicillins in milk of animal origin by capillary electrophoresis: Is sample treatment the bottleneck for routine laboratories?

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.

A surface plasmon resonance sensor with synthetic receptors decorated on graphene oxide for selective detection of benzylpenicillin

Antibiotic residues in foods, water and the environment reveal antibiotic-resistant bacterial strains, disrupting the ecological balance and causing serious health problems. For these reasons, the detection of antibiotic residues is crucial for the protection of human health. Herein, the detection of benzylpenicillin antibiotic from aqueous and milk sample solutions was carried out by surface plasmon resonance (SPR) sensor using synthetic receptor-molecularly imprinted polymer. The benzylpenicillin-imprinted poly(hydroxyethyl methacrylate-graphene oxide-N-methacryloyl-l-phenylalanine) (MIP-GO) SPR sensor was prepared. Benzylpenicillin detection was performed by MIP-GO SPR sensor in a 1-100 ppb concentration range of benzylpenicillin with 0.9665 linear correlation and 0.021 ppb detection limit. Selectivity analysis showed that the MIP-GO SPR sensor detected the benzylpenicillin molecule 8.16 times more selectively than amoxicillin and 14.04 times more selectively than ampicillin. To examine the imprinting efficiency, non-imprinted poly(hydroxyethyl methacrylate-graphene oxide-N-methacryloyl-l-phenylalanine) (NIP-GO) SPR sensor was also prepared using the same procedure without benzylpenicillin addition. Since graphene oxide (GO) was added to enhance the sensor signal response by increasing sensitivity, the control analyses were performed by a poly(hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) (MIP) SPR sensor without adding GO. Moreover, repeatability studies of MIP-GO SPR sensor were statistically evaluated and the RSD of intra-day assays less than 1% specified that there was no loss of performance for the benzylpenicillin detection ability even after four cycles. As a real food sample analysis, the benzylpenicillin spiked and unspiked milk samples were evaluated and high-performance liquid chromatography experiments were carried out for validation.

Selective Detection of Penicillin G Antibiotic in Milk by Molecularly Imprinted Polymer-Based Plasmonic SPR Sensor

Molecularly imprinted polymer-based surface plasmon resonance sensor prepared using silver nanoparticles was designed for the selective recognition of Penicillin G (PEN-G) antibiotic from both aqueous solution and milk sample. PEN-G imprinted sensors (NpMIPs) SPR sensor was fabricated using poly (2-hydroxyethyl methacrylate-N-methacroyl-(L)-cysteine methyl ester)-silver nanoparticles-N-methacryloyl-L-phenylalanine methyl ester polymer by embedding silver nanoparticles (AgNPs) into the polymeric film structure. In addition, a non-imprinted (NpNIPs) SPR sensor was prepared by utilizing the same polymerization recipe without addition of the PEN-G template molecule to evaluate the imprinting effect. FTIR-ATR spectrophotometer, ellipsometer, contact angle measurements were used for the characterization of NpMIPs SPR sensors. The linear concentration range of 0.01–10 ng/mL PEN-G was studied for kinetic analyses. The augmenting effect of AgNPs used to increase the surface plasmon resonance signal response was examined using polymer-based PEN-G imprinted (MIPs) sensor without the addition of AgNPs. The antibiotic amount present in milk chosen as a real sample was measured by spiking PEN-G into the milk. According to the Scatchard, Langmuir, Freundlich and Langmuir–Freundlich adsorption models, the interaction mechanism was estimated to be compatible with the Langmuir model.

Advances in the Analysis of Veterinary Drug Residues in Food Matrices by Capillary Electrophoresis Techniques

In the last years, the European Commission has adopted restrictive directives on food quality and safety in order to protect animal and human health. Veterinary drugs represent an important risk and the need to have sensitive and fast analytical techniques to detect and quantify them has become mandatory. Over the years, the availability of different modes, interfaces, and formats has improved the versatility, sensitivity, and speed of capillary electrophoresis (CE) techniques. Thus, CE represents a powerful tool for the analysis of a large variety of food matrices and food-related molecules with important applications in food quality and safety. This review focuses the attention of CE applications over the last decade on the detection of different classes of drugs (used as additives in animal food or present as contaminants in food products) with a potential risk for animal and human health. In addition, considering that the different sample preparation procedures have strongly contributed to CE sensitivity and versatility, the most advanced sample pre-concentration techniques are discussed here.

Pretreatment-Integration for Milk Protein Removal and Device-Facilitated Immunochromatographic Assay for 17 Items

Accurate and comprehensive immunochromatographic assay (ICA) data are urgently required in the daily supervision of plants, schools, testing institutions, and law-enforcing departments. Through pretreatment-integration and device-facilitated operation, a quantitative ICA with high sensitivity and throughput was realized on the basis of a commercialized semi-quantitative ICA strip. Three pretreatment methods, namely, acid base, heavy metal salt, and organic solvent methods, have less than three steps. The pretreatment was established for protein removal. A total of 17 pretreated ICA items in milk were considered for the identification of the most suitable pretreatment method. The items are composed of six items pretreated by the acid-base method, six by the heavy salt method, and five by the organic solvent method. Then, the ICA results with pretreatment were compared with those without pretreatment. After pretreatment, the signal intensity increased by 39%, the detection limit decreased to 12%, the half maximal inhibitory concentration decreased to 18%, and the detection range increased fourfold. A device with mixing and centrifugation functions was designed for the pretreatment-related operations. A pre-incubation sampling device was used to facilitate incubation in batch and high-throughput detection. An ICA reader was used. The detection throughput reached 8 samples per batch or 32 samples per hour. The designed devices were printed through 3D printing and rapid prototyping.

Electrochemical surface plasmon resonance (EC-SPR) aptasensor for ampicillin detection

Surface plasmon resonance technique is highly sensitive to various processes taking place on a metal film and it has emerged as a powerful label-free method to study molecular binding processes taking place on a surface. Another important but less explored area of applications is the use of hybrid methods which combine electrochemistry with optical methods for better monitoring and understanding of biochemical processes. A detection method based on surface plasmon resonance was developed for ampicillin, applying electrochemical techniques for the elaboration and characterization of the aptasensing platform used in this study. Ampicillin is a broad-spectrum β-lactam antibiotic, used both in human and veterinary medicine for the treatment and prevention of primary respiratory, gastrointestinal, urogenital, and skin bacterial infections. It is widely used because of its broad spectrum and low cost. This widespread use can result in the presence of residues in the environment and in food leading to health problems for individuals who are hypersensitive to penicillins. The gold chip was functionalized through potential-assisted immobilization, using multipulse amperometry, first with a thiol-terminated aptamer, as a specific ligand and secondly, using the same procedure, with mercaptohexanol, used to cover the unoccupied binding sites on the gold surface in order to prevent the nonspecific adsorption of ampicillin molecules. After establishing the optimal conditions for the chip functionalization, different concentrations of ampicillin were detected in real time, in the range of 2.5-1000 μmol L^-1, with a limit of detection of 1 μmol L^-1, monitoring the surface plasmon resonance response. The selectivity of the aptasensor was proven in the presence of other antibiotics and drugs, and the method was successfully applied for the detection of ampicillin from river water. Graphical abstract ᅟ.

Molecularly Imprinted Polymers as Extracting Media for the Chromatographic Determination of Antibiotics in Milk

Milk-producing animals are typically kept stationary in overcrowded large-scale farms and in most cases under unsanitary conditions, which promotes the development of infections. In order to maintain sufficient health status among the herd or promote growth and increase production, farmers administer preventative antibiotic doses to the animals through their feed. However, many antibiotics used in cattle farms are intended for the treatment of bacterial infections in humans. This results in the development of antibiotic-resistant bacteria which pose a great risk for public health. Additionally, antibiotic residues are found in milk and dairy products, with potential toxic effects for the consumers. Hence the need of antibiotic residues monitoring in milk arises. Analytical methods were developed for the determination of antibiotics in milk, with key priority given to the analyte extraction and preconcentration step. Extraction can benefit from the production of molecularly imprinted polymers (MIPs) that can be applied as sorbents for the extraction of specific antibiotics. This review focuses on the principals of molecular imprinting technology and synthesis methods of MIPs, as well as the application of MIPs and MIPs composites for the chromatographic determination of various antibiotic categories in milk found in the recent literature.

Electrochemical behaviour of several penicillins at high potential

Successful penicillin detection on a boron-doped diamond electrode from real environmental, biomedical and pharmaceutical samples by DPV and flow analysis.

Circular dichroism spectroscopy: An efficient approach for the quantitation of ampicillin in presence of cloxacillin

Ampicillin exhibited a negative and a positive cotton effects on the circular dichroism (CD) spectra in the wavelength range of 200-280nm. Cloxacillin showed a positive cotton band peaking at 228nm. Three sensitive, precise and accurate CD spectroscopic methods have been developed for the determination of ampicillin and cloxacillin. Method A was used for the determination of ampicillin in presence of cloxacillin by measuring ellipticity at 206nm. Method B and C were employed to determine ampicillin and cloxacillin based on evaluation of ellipticity at 233nm and 228nm, respectively. Methods A, B and C showed linearity in the concentration range of 10-40μgmL(-1), 5-40μgmL(-1) ampicillin and 10-80μgmL(-1) cloxacillin, respectively. The method A was successfully applied to the determination of ampicillin in commercial dosage forms containing equivalent amount of cloxacillin.

Analysis of antibiotics by CE and their use as chiral selectors: An update

The widespread use of antibiotics in medicine and as growth-promoting agents has increased the demand for suitable analytical techniques for their analysis. Analytical methods based on CE or miniaturized CE systems have proved over the years their ability for the analysis of antibiotics. Since our last review (Electrophoresis 2014, 35, 28-49) several new CE methodologies have been reported for antibiotic analysis. This review presents an update of the literature published from June 2013 to June 2015 for the analysis of antibiotics by CE. UV continues being the most used detection system for antibiotics analysis by CE. Strategies to improve sensitivity as the use of sensitive detection systems and the application of preconcentration techniques appear to be the major developments. Furthermore, the use of portable and miniaturized devices for antibiotic analysis is presented in detail. Applications of the developed methodologies to the determination of residues of antibiotics in biological, food, and environmental samples are carefully described. Finally, new developments and applications of antibiotics as chiral selectors in CE are also included.

Simultaneous separation of ergot alkaloids by capillary electrophoresis after cloud point extraction from cereal samples

A new and sensitive analytical methodology for ergot alkaloids (EA) determination from cereal samples based on cloud point extraction (CPE) prior to CE-UV absorbance was developed. The methodology involves extraction under acid conditions and subsequent preconcentration by applying a simple, rapid and environmentally friendly low volume surfactant extraction procedure. After extraction, CE analysis was carried out by performing dilutions on preconcentrated surfactant rich phase, achieving a single peak or simultaneous alkaloids determination. A real preconcentration factor of 22 of total EA was obtained, demonstrating the efficiency of this methodology. The limits of detection were 2.6 and 2.2 μg/kg for ergotamine and ergonovine, respectively. Validation procedure revealed suitable linearity, accuracy and precision. The average extraction and clean-up recoveries were compared with the theoretical values and were better than 92%. This method was successfully applied to the determination of EA in different varieties of commercial flour samples, two grain samples and one of the leading brands cereal-based product for infant feeding. The high sensitivity achieved for EA determinations in real samples suggests CPE procedure as an interesting approach to improve CE-UV visible detection limits. Moreover, the whole process could be considered as a contribution to green chemistry because nonorganic solvents were involved, demonstrating its great potential over conventional techniques.