Ultrasound-assisted matrix solid phase dispersive extraction for the simultaneous analysis of β-lactams (four penicillins and eight cephalosporins) in milk by high performance liquid chromatography with photodiode array detection

Preparation of monoclonal antibody and development of an enzyme-linked immunosorbent assay for the detection of ceftiofur in animal-derived foods

Ceftiofur (CEF) residues in animal-derived foods are of great concern to farmers, regulatory agencies and consumers. In this study, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method was established to quickly monitor CEF residues in edible animal tissues using an easy sample preparation procedure. A monoclonal antibody, 4D5, against CEF has been produced at first, which had IC₅₀ values for CEF, ceftriaxone, cefquinome, cefotaxime and desfuroylceftiofur of 0.78 μg/L, 0.73 μg/L, 13.6 μg/L, 8.99 μg/L and 8.89 μg/L, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) in artificially contaminated animal-derived foods were 0.12-0.19 μg/L and 0.20-0.30 μg/L. The recovery rates were in the range of 89.7-109.0%. The CVs were less than 6.7%. A good correlation (R= 0.9994) between the ic-ELISA and UPLC-MS/MS showed the reliability of the developed ic-ELISA. The ic-ELISA produces a sensitive, accurate and low-cost tool for the screening of residues of CEF in animal-derived foods.

Development of a modified quick, easy, cheap, effective, rugged, and safe method based on melamine sponge for multi-residue analysis of veterinary drugs in milks by ultra-performance liquid chromatography tandem mass spectrometry

The purpose of this study was to develop a modified QuEChERS method based on melamine sponge for rapid determination of multi-class veterinary drugs in milks by UPLC-MS/MS. Through simple infiltration and extrusion, fast and convenient matrix purification could be achieved within several seconds, and there was no need of extra phase separation operations. Good linearity with correlation coefficient (R²) ≥0.999 was obtained for all drugs in the range of 2~500 µg·kg^-1. The obtained matrix effects were within ±20% for all monitored drugs. The recoveries of all monitored drugs ranged from 60.7% to 116.0% at three spiked levels (50, 100, and 200 µg·kg^-1), with relative standard deviations less than 7.4%. Comparatively low LODs and LOQs were obtained in the ranges of 0.1~3.8 µg·kg^-1 and 0.2~6.3 µg·kg^-1, respectively. Compared with conventional purification adsorbents, melamine sponge yielded an equal or higher purification performance with matrix removal rate as high as 52.5% and acceptable recoveries in range of 60%-120% for all monitored drugs. The satisfactory results have demonstrated the good potential of melamine sponge in matrix purification for rapid determination of multiclass residues in food safety.

Green Bioanalytical Applications of Graphene Oxide for the Extraction of Small Organic Molecules

Bioanalysis is the scientific field of the quantitative determination of xenobiotics (e.g., drugs and their metabolites) and biotics (e.g., macromolecules) in biological matrices. The most common samples in bioanalysis include blood (i.e., serum, plasma and whole blood) and urine. However, the analysis of alternative biosamples, such as hair and nails are gaining more and more attention. The main limitations for the determination of small organic compounds in biological samples is their low concentration in these matrices, in combination with the sample complexity. Therefore, a sample preparation/analyte preconcentration step is typically required. Currently, the development of novel microextraction and miniaturized extraction techniques, as well as novel adsorbents for the analysis of biosamples, in compliance with the requirements of Green Analytical Chemistry, is in the forefront of research in analytical chemistry. Graphene oxide (GO) is undoubtedly a powerful adsorbent for sample preparation that has been successfully coupled with a plethora of green extraction techniques. GO is composed of carbon atoms in a sp² single-atom layer of a hybrid connection, and it exhibits high surface area, as well as good mechanical and thermal stability. In this review, we aim to discuss the applications of GO and functionalized GO derivatives in microextraction and miniaturized extraction techniques for the determination of small organic molecules in biological samples.

Sensitive and Fast Determination of Ceftiofur in Honey and Veterinary Formulation by HPLC-UV Method with Pre-column Derivatization

A novel, sensitive and rapid high performance liquid chromatography (HPLC) method for the determination of ceftiofur by pre-column derivatization with 1,2-naphthoquinone-4-sulfonate. Analysis was performed within 5 min on a Kinetex C18 column based on core-shell technology. The mobile phase composed of acetonitrile-water (50:50, v/v) pumped isocratically at a flow rate of 1.0 mL/min under UV detection at 254 nm. The factors affecting the derivatization reaction and separation conditions were carefully evaluated and optimized. The method was linear over the concentration range of 45-450 ng/mL with a limit of detection of 3.29 ng/mL and limit of quantitation of 10.97 ng/mL. The new method was successfully applied for the analysis of ceftiofur in the veterinary formulation and honey with average recoveries of 100.78% and 98. 83%, respectively. The present method is suitable and favorable for the analysis of ceftiofur on account of its sensitivity, rapidity and cost-effectiveness. In addition, it could have significant application for the determination of ceftiofur in other food products.

A highly sensitive and selective method for the determination of ceftiofur sodium in milk and animal-origin food based on molecularly imprinted solid-phase extraction coupled with HPLC-UV

The effective analysis of cephalosporin antibiotics in food animals has attracted considerable attention. Herein, a high-performance liquid chromatograph equipped with a UV method based on molecularly imprinted-solid phase extraction (MISPE-HPLC-UV) was developed for preconcentration, cleanup and determination of ceftiofur sodium (CTFS) in food samples. In this method, an eco-friendly molecularly imprinted polymer (MIP) was synthesized and employed as an adsorbent, which exhibited excellent selectivity towards CTFS in water, and adsorption equilibrium could be reached within 1 h. Under the optimized conditions, good linearity was obtained for CTFS in the range of 0.005-1.0 mg L^-1 with a lower LOD of 0.0015 mg L^-1, and the average recoveries were higher than 91.9% (RSD less than 8.5%) at three spiked levels in milk, chicken, pork and beef samples. After 20 cycles, the recovery of the MISPE cartridge for CTFS was still higher than 95%, which proved that the MISPE-HPLC-UV method was highly sensitive and selective for the analysis of CTFS in food samples.

A Method for the Determination of Veterinary Drugs from Different Therapeutic Classes in Animal Urine

A rapid, precise and robust HPLC separation procedure has been developed and optimized for the determination of a series of drugs of different therapeutic classes: chlortetracycline, oxitetracycline, cefoperazone, diclofenac, tiamphenicol, marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin and flumequine. The chromatographic method used a monolithic C18 column and both diode array and fluorescence detection. This procedure was validated for the analysis of drugs in cow urine, using a simple and fast procedure with methanol/acetonitrile, allowing the simultaneous and efficient extraction of most of the studied drugs. The proposed method was successfully applied to the determination of enrofloxacin in cow urine, collected after the administration of this antibiotic.

Hydrophilic-interaction planar chromatography in ultra-sensitive determination of α-aminocephalosporin antibiotics. Application to analysis of cefalexin in goat milk samples using modified QuEChERS extraction technique

A highly sensitive, selective and precise HPTLC method coupled with fluorescence detection was developed and validated for the determination of α-aminocephalosporin antibiotics; namely cefalexin, cefadroxil and cefradine in their standard solutions. The applicability of the developed methodology was demonstrated via analysis of cefalexin in goat milk samples. Full optimization of the fluorescence derivatization reaction was carried out with regard to the standard solutions of the studied compounds or after extraction of milk samples. The separation of the studied compounds was performed on HPTLC precoated silica gel plates 60 F₂₅₄ using acetonitrile: water in a ratio 85:15 (v/v) as a mobile phase. The retention behavior of the formed derivatives was discussed in detail. It was found that hydrophilic interaction mode is the main interaction mechanism governing the retention of the formed derivatives. In addition, an experimental design approach was conducted for optimization of the chromatographic conditions. Modified QuEChERS was applied as an efficient extraction technique of cefalexin from both spiked and real goat milk samples. Optimization of QuEChERS extraction technique to achieve the highest extraction recovery was performed and the results indicate that this method provides a good extraction recovery (83-116%) for cefalexin from goat milk samples. Limit of detection (LOD) of the developed method was found to be 0.023, 0.005, and 0.023 ng band^-1 for cefalexin, cefadroxil and cefradine, respectively in their standard solutions and 0.165 ng band^-1 for cefalexin in goat milk samples. According to the achieved LOD values, the method sensitivity was quasi-equivalent to other methods based on expensive techniques such as HPLC-UV and HPLC-MS and it is sufficient to determine cefalexin below its MRL in milk samples. Moreover, the method was successfully applied to a pharmacokinetic study of cefalexin in goat milk after single intramuscular injection of 10 mg of cefalexin kg^-1 per body weight.

Quantitative analysis of cefazolin sodium in lyophilized powder by infrared spectrophotometry: Green, low cost, fast and effective

Cefazolin sodium is a broad-spectrum antibiotic used in the treatment of infectious diseases in humans and in the surgical prophylaxis. Thus, since a considerable number of people have access to this drug, it is of great interest of quality control. The aim of this study was development and validation of a green method by Fourier-Transform Infrared (FT-IR) transmission spectrophotometry for the quantification of cefazolin sodium in lyophilized powder. This technique is widely used in the pharmaceutical industry due to its ease of execution, low cost, safety and high precision and accuracy. It has been employed in the quality control routine of numerous pharmaceuticals in order to identify them and quantify their active principles. The proposed method was completely validated according ICH guidelines, showing selectivity, accuracy, precision, robustness and linearity. It was linear over the concentration range of 0.4-1.7 mg with correlation coefficient 0.999, limits of detection and quantification of 0.017 mg and 0.052 mg, respectively, precise, accurate and robust when changes in the time, pressure and mark of potassium bromide were carried out during the preparation of the pellets. The proposed method was successfully applied to the qualitative and quantitative quality control of cefazolin sodium in lyophilized powder. In addition, the method is considered green, clean and sustainable since it uses only a single reagent; it is a fast, low-cost and environmentally friendly method.

Detection of β-Lactams and Chloramphenicol Residues in Raw Milk-Development and Application of an HPLC-DAD Method in Comparison with Microbial Inhibition Assays

The present study was carried out to assess the detection sensitivity of four microbial inhibition assays (MIAs) in comparison with the results obtained by the High Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) method for antibiotics of the β-lactam group and chloramphenicol in fortified raw milk samples. MIAs presented fairly good results when detecting β-lactams, whereas none were able to detect chloramphenicol at or above the permissible limits. HPLC analysis revealed high recoveries of examined compounds, whereas all detection limits observed were lower than their respective maximum residue limits (MRL) values. The extraction and clean-up procedure of antibiotics was performed by a modified matrix solid phase dispersion procedure using a mixture of Plexa by Agilent and QuEChERS as a sorbent. The HPLC method developed was validated, determining the accuracy, precision, linearity, decision limit, and detection capability. Both methods were used to monitor raw milk samples of several cows and sheep, obtained from producers in different regions of Greece, for the presence of examined antibiotic residues. Results obtained showed that MIAs could be used effectively and routinely to detect antibiotic residues in several milk types. However, in some cases, spoilage of milk samples revealed that the kits’ sensitivity could be strongly affected, whereas this fact does not affect the effectiveness of HPLC-DAD analysis.

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.

Magnetic solid phase extraction based on graphene oxide/nanoscale zero-valent iron for the determination of tetracyclines in water and milk by using HPLC-MS/MS

A magnetic solid-phase extraction (MSPE) based on graphene oxide/nanoscale zero-valent iron (GO/nZVI) coupled with HPLC-MS/MS was proposed for the determination of trace tetracycline antibiotics (TCs) in water and milk.

A graphene oxide surface–molecularly imprinted polymer as a dispersive solid-phase extraction adsorbent for the determination of cefadroxil in water samples

Graphene oxide–functionalized molecularly imprinted polymer particles have been prepared for specific selective extraction and determination of cefadroxil in environmental water samples.

Analysis of Six β-Lactam Residues in Milk and Egg by Micellar Electrokinetic Chromatography with Large-Volume Sample Stacking and Polarity Switching

A new micellar electrokinetic chromatography method with large-volume sample stacking and polarity switching was developed to analyze amoxicllin, cephalexin, oxacillin, penicillin G, cefazolin, and cefoperazone in milk and egg. The important parameters influencing separation and enrichment factors were optimized. The optimized running buffer consisted of 10 mM phosphate and 22 mM SDS at pH 6.7. The sample size was 1.47 kPa × 690 s, the reverse voltage was 20 kV, and the electric current recovery was 95%. Under these optimum conditions, the enrichment factors of six β-lactams were 193-601. Their LODs were <0.26 ng/g, and LOQs were all 2 ng/g, which was only 1/50-1/2 of the maximum residual limits demanded by U.S. and Japanese regulations. The intraday and interday RSDs of method were lower than 3.70 and 3.91%, respectively. The method can be applied to determine these six antibiotic residues in egg and milk.

Matrix molecularly imprinted mesoporous sol-gel sorbent for efficient solid-phase extraction of chloramphenicol from milk

Highly selective and efficient chloramphenicol imprinted sol-gel silica based inorganic polymeric sorbent (sol-gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol-gel catalyst. Non-imprinted sol-gel polymer (sol-gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol-gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol-gel MIP was 23 mg/g. The sol-gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work-flow. Intra and inter-assay RSD values were less than 13% and accuracy expressed as relative recovery ranged from 85 to 106%.

Determination of cefadroxil in rat plasma and urine using LC-MS/MS and its application to pharmacokinetic and urinary excretion studies

A simple, rapid, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated for the determination of cefadroxil, a first-generation cephalosporin, in rat plasma and urine. Rat samples were deproteinized with methanol, and then injected into the LC-MS/MS system (electro-spray ionization, positive mode) for quantification. Drugs were separated on a Synergi™ 4 μm Polar-RP 80A column (150 mm × 2.0 mm, 4 μm) with a mixture of 0.1% formic acid and methanol (62:38, v/v) as the mobile phase at 0.2 mL/min. Detection was performed using multiple reaction-monitoring modes at m/z 364.1→208.1 (for cefadroxil) and m/z 368.1→174.2 (for cefaclor, the internal standard). Method was specific and linear over the concentration range of 10-10,000 ng/mL. Validation parameters for cefadroxil, including accuracy, precision, absolute matrix effect, and stability in rat plasma and urine, were acceptable according to the biological method validation guidelines of the FDA (2001) [16]. Cefadroxil levels in plasma up to 1440 min or 480 min and urine up to 96 h were quantifiable following oral and intravenous cefadroxil administrations to rats at a dose of 2mg/kg, each, suggesting that the method is appropriate for routine pharmacokinetic studies including urinary recovery in rats.

Ultrasound-assisted dispersive extraction for the high pressure liquid chromatographic determination of tetracyclines residues in milk with diode array detection

Ultrasound assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of tetracyclines (oxytetracycline, tetracycline, epi-chlorotetracycline, chlorotetracycline and doxycycline) from milk. Target analytes were determined by an accurate and sensitive chromatographic analytical method, which was validated to meet the European Legislation criteria. The separation was performed on a LiChroCART-LiChrospher® 100 RP-18 (5μm, 250×4mm) analytical column, operated at ambient temperature, followed by diode array detection. Validation included investigation of linearity, selectivity, stability, limits of detection and quantitation, decision limit, detection capability, trueness, precision and ruggedness according to the Youden's approach. Limits of quantitation of examined tetracyclines were from 14.5 to 56.6μg/kg significantly lower than respective Maximum Residue Limits, whereas recoveries ranged from 82.0% to 108%. The applicability of the method was evaluated using milk samples purchased from local market. Accuracy of the method was additionally proved by analysis of bovine milk certified reference material (BCR®-492).