Simultaneous determination of six penicillins in cows' raw milk by a multiresidue high-performance liquid chromatographic method

Bacteria-based electro-optical platform for ampicillin detection in aquatic solutions

We have shown for the first time that it is possible to use a bacteria-based sensory system consisting of the bacterium Pseudomonas putida TSh-18 and an electro-optical sensor to detect ampicillin in the concentration range 0.5-600 μg/mL. Changes in the anisotropy of cell polarizability were detected at 900 and 2100 kHz; these represented the state of the cytoplasm and of the cell membrane, respectively. The changes indicate the quickest cell response to changes in the characteristics of the bacterial culture exposed to ampicillin. We have also shown that it is possible to monitor the ampicillin in the presence of kanamycin. In control experiments, we examined the effects of ampicillin and kanamycin on bacterial cells by phase-contrast microscopy and by standard microbiological tests on solid media. P. putida TSh-18 is recommended as a sensor system for ampicillin detection. Electro-optical analysis ensures detection of ampicillin in aquatic solutions in real-time, takes 10 min, and offers a lower limit of ampicillin detection of 0.5 μg/mL, which is lower than the European Community's maximum residue limit standards for penicillin antibiotics.

Immunosensor for trace penicillin G detection in milk based on supported bilayer lipid membrane modified with gold nanoparticles

In this work, we developed an immunosensor for electrochemical detection of penicillin G at trace level. The biosensor was fabricated by immobilizing anti-penicillin G in a supported bilayer lipid membrane (s-BLM) modified with gold nanoparticles, and the modified electrodes were characterized by the scanning electron microscope (SEM), cyclic voltammetry and electrochemical impedance spectroscopy. The biosensor was able to detect penicillin G with a linear correlation ranging from 3.34×10(-3)ng/L to 3.34×10(3)ng/L and a detection limit of 2.7×10(-4)ng/L, much lower than the maximum residue limit (MRL) of penicillin G in milk (4ppb, equal to 4×10(3)ng/L) set out by the European Union. The mean coefficient variation (CV) of the intra-assays and the inter-assays were 5.4% and 7.7%, respectively. In addition, the concentration of penicillin G in milk samples determined by this biosensor was in good agreement with that determined by high performance liquid chromatography (HPLC) assay.

Residue depletion of ampicillin in eggs

A residue depletion study of ampicillin (AMP) was performed after oral dosing (60.0 mg/kg and 120.0 mg/kg body weight once a day for 5 days) to laying hens, through the use of reversed-phase high-performance liquid chromatography with fluorescence detection (RP-HPLC-FLD) to achieve detection of ampicillin residue in eggs. Limit of detection was 0.5 ng/g, and limit of quantitation was 1.2 ng/g for ampicillin. Extraction recoveries of ampicillin from samples fortified at 5.0-125.0 ng/g levels ranged from 77.5% to 84.6% in albumen, 77.9% to 87.5% in yolk, and 77.9% to 88.6% in whole egg, with coefficients of variation ≤ 9.3%. The maximum concentrations of ampicillin in albumen, yolk, and whole egg were detected at 1, 2, and 1 day after the last administration of ampicillin, respectively. Ampicillin was not detectable in albumen at day 9 of withdrawal time, at day 10 and 11 in yolk, and day 9 and 11 in whole egg at each of those 2 dose levels. The theoretical withdrawal time of AMP in whole egg was 6.730 and 7.296 days for 60 and 120 mg/kg oral dosage, respectively. This method also proved to be suitable as a rapid and reliable method for the determination of ampicillin in other poultry eggs.

Flow-injection chemiluminescence determination of cloxacillin in water samples and pharmaceutical preparation by using CuO nanosheets-enhanced luminol-hydrogen peroxide system

In this paper, a rapid and sensitive flow-injection chemiluminescence (flow-CL) system was developed for the determination of cloxacillin sodium in environmental water samples and pharmaceutical preparations. The method was based on the enhancement effect of cloxacillin sodium on the CL reaction of luminal-H₂O₂-CuO nanosheets (NSs) in alkaline medium. The CuO nanosheets were synthesized using a green sonochemical method. The physical properties of the synthesized CuO nanosheets were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The influences of various experimental factors such as H₂O₂, NaOH, luminol and CuO nanosheets concentrations were investigated. Under the optimum conditions, the enhanced CL intensity was linearly related to the concentration of cloxacillin sodium in the range of the 0.05-30.00 mg L(-1) with a correlation coefficient of 0.995. The corresponding detection limit (3σ) was calculated to be 0.026 mg L(-1). The relative standard deviation (RSD) of the developed method was 2.21% with 11 repeated measurements of 4.00 mg L(-1) cloxacillin sodium. Also, a total analysis time per sample was 30 s which confirmed the rapidity of the proposed method. The analytical applicability of the proposed CL system was assessed by determining cloxacillin sodium in spiked environmental water samples and pharmaceutical preparation. Furthermore, the possible mechanism of CL reaction was discussed.

Comparative Study of RP-HPLC and UV Spectrophotometric Techniques for the Simultaneous Determination of Amoxicillin and Cloxacillin in Capsules

Reversed-phase HPLC and UV spectrophotometric techniques using water as solvent have been developed and validated for the simultaneous determination of amoxicillin and cloxacillin in capsules. For both techniques, the linearity range of 60.073x2013;140.0 µg/mL was studied. The spectrophotometric data show that non-derivative techniques, such as absorbance ratio and compensation, and ratio spectra first-order derivative could be successfully used for the co-assay of amoxicillin and cloxacillin. Based on the statistical comparison of spectrophotometric and chromatographic data, the interchangeability between HPLC and UV spectrophotometric techniques has been suggested for the routine analysis.

Application of a solid-phase fluorescence immunoassay to determine amoxicillin residues in fish tissue

The present study demonstrates an application of Parallux (a solid-phase fluorescence immunoassay) for amoxicillin analysis in fish tissue. Amoxicillin at the recommended therapeutic dose (400 mg/kg body weight) was orally administered to three groups of 25 olive flounder ( Paralichthys olivaceus ), 25 rockfish ( Sebastes schlegeli ) and 25 red sea bream ( Pagrus major ) for 7 consecutive days. Amoxicillin was detected in the muscle of fish treated by the 3rd day of the withdrawal period. The recovery rates of all spiked muscle samples were > 86% of the spiked values. The present study showed that solid-phase fluorescence immunoassay can be easily adopted in predicting amoxicillin residues in the muscle tissue of farmed fish.

Quantitative analysis of penicillins in porcine tissues, milk and animal feed using derivatisation with piperidine and stable isotope dilution liquid chromatography tandem mass spectrometry

Penicillins are used universally in both human and veterinary medicine. The European Union (EU) has established maximum residue levels (MRLs) for most ß-lactam antibiotics in milk and animal tissues and included them in the National Residue Monitoring Programs. In this study, a novel method is described for the determination and confirmation of eight penicillins in porcine tissues, milk and animal feed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). To prevent degradation of penicillin residues during workup, a derivatisation procedure was developed, by which penicillins were converted to stable piperidine derivatives. Deuterated piperidine derivatives were synthesised for all relevant penicillins, enabling the use of isotope dilution for accurate quantification. Penicillin residues were derivatised in the crude extract with piperidine and isolated using solid-phase extraction. The penicillin piperidine derivatives were determined by LC–MS/MS. The method was validated at the current MRLs, which range from 25–300 µg kg⁻¹ in muscle and kidney to 4–30 µg kg⁻¹ in milk as well as at the target value of 100 µg kg⁻¹ chosen for animal feed, according to the EU requirements for a quantitative confirmatory method. Accuracy ranged from 94–113% (muscle), 83–111% (kidney) and 87–103% (milk) to 88–116% (animal feed). Intra-day precision (relative standard deviation (RSD)_r) ranged from 5–13% (muscle, n = 18), 4–17% (kidney, n = 7) and 5–18% (milk, n = 7) to 11–32% (animal feed, n = 18). Inter-day precision (RSD_RL, n = 18) ranged from 6–23% (muscle) to 11–36% (animal feed). From the results, it was concluded that the method was fit for purpose at the target MRLs in animal tissue and target levels for animal feed.

ICH guidance in practice: Validated stability-indicating HPLC method for simultaneous determination of ampicillin and cloxacillin in combination drug products

Ampicillin and cloxacillin were degraded together under different stress test conditions prescribed by International Conference on Harmonization. The samples so generated were used to develop a stability-indicating high performance liquid chromatographic (HPLC) method for the two drugs. The drugs were well separated from degradation products using a reversed-phase (C-18) column and a mobile phase comprising of acetonitrile:phosphate buffer (pH 5.0), which was delivered initially in the ratio of 15:85 (v/v) for 1 min, then changed to 30:70 (v/v) for next 14 min, and finally equilibrated back to 15:85 (v/v) from 15 to 20 min. Other HPLC parameters were: flow rate, 1 ml/min; detection wavelength, 225 nm; and injection volume, 5 microl. The method was validated for linearity, precision, accuracy, specificity and selectivity. It was also compared with the assay procedures given in British Pharmacopoeia for individual drugs. Similar results were obtained, indicating that the proposed single method allowed selective analysis of both ampicillin and cloxacillin, in the presence of their degradation products formed under a variety of stress conditions. The developed procedure was also applicable to the determination of instability of the drugs in commercial products.

Trace determination of β-lactam antibiotics in surface water and urban wastewater using liquid chromatography combined with electrospray tandem mass spectrometry

A sensitive and reliable method using liquid chromatography-electrospray tandem mass spectrometry has been developed and validated for the trace determination of beta-lactam antibiotics in natural and wastewater matrices. Water samples were enriched by solid-phase extraction. The analytes included amoxicillin (AMOX), ampicillin (AMP), oxacillin (OXA), cloxacillin (CLOX) and cephapirin (CEP). Average recoveries of beta-lactams (BLs) in fortified samples were generally above 75% (except amoxicillin) with the standard deviations lower than 10% in water matrices. Amoxicillin was not quantified due to poor recovery (less than 40%) in the investigated water matrices. Matrix effects were found to be minimal when measuring these compounds in water matrices. The accuracy, within- and between-run precision of the assay fell within acceptable ranges of 15% absolute. The method detection limit (MDL) was estimated to range between 8 and 10 ng/L in surface water, 13 and 18 ng/L in the influent and 8 and 15 ng/L in the effluent from a wastewater treatment plant. A large number of actual water samples were analyzed using this method in order to evaluate the occurrence of the beta-lactams in a river and a wastewater treatment plant in northern Colorado. Most of the samples were negative for all analytes. These compounds were found at 15-17 ng/L in the three influent samples and at 9-11 ng/L in three surface water samples out of a total of 200 samples. This indicates that contamination by beta-lactam antibiotics is of minor importance to the small mixed-watershed.

Development and validation of a fully automated LC method for the determination of cloxacillin in human plasma using anion exchange restricted access material for sample clean-up

In the framework of a preliminary investigation on the plasma profile of cloxacillin after oral administration, a simple and rapid LC method was developed for the direct determination of this compound in human plasma. The on-line sample clean-up was carried out using a weak anion exchanger (diethylaminoethyl groups) as restricted access material (RAM). The effects of the washing liquid pH, the ionic strength and the addition of organic modifier to the washing liquid were studied in order to obtain an efficient sample clean-up and a high recovery of cloxacillin. The separation was achieved on octadecylsilica stationary phase using a mobile phase consisting in a mixture of phosphate buffer (pH 4.0; 25 mM) and acetonitrile (72:28, v/v). The UV detection was performed at 215 nm. The most appropriate regression model of the response function as well as the limit of quantitation (LOQ) were first selected during the pre-validation step. These criteria were then assessed during the formal validation step. The LOQ was 50 ng/ml. The method was also validated with respect to analyte recovery, precision, trueness, accuracy and linearity. Finally, it was successfully applied for the analysis of the first plasma samples obtained from patients having taken an oral dose of 500 mg cloxacillin.

Residues of beta-lactam antibiotics in bovine milk: confirmatory analysis by liquid chromatography tandem mass spectrometry after microbial assay screening

A procedure for the simultaneous determination of the residues of seven beta-lactam antibiotics (penicillin G, ampicillin, oxacillin, amoxicillin, dicloxacillin, cephalexin, cephapirin) in bovine raw milk using tandem liquid chromatography mass spectrometry (LC-MS/MS) is described. The antibiotics were extracted by an acetic acid solution after centrifugation and filtration. The beta-lactams were separated using reversed-phase liquid chromatography. A triple quadrupole mass spectrometer was used in positive-ion mode as a detector via a Turbo Ionspray interface for electrospray ionization (ESI). The limits of detection and quantitation of the method were below the legal tolerances, except for ampicillin. The method was used to confirm 53 samples found positive by a microbial method (Delvotest SP) at the Istituto Zooprofilattico Sperimentale per la Lombardia e l'Emilia Romagna of Brescia during 2001. Penicillin G was found in 26 samples at concentrations ranging from less than 4 to 6240+/-550 microg x l(-1). Amoxicillin was found in three samples at concentrations ranging from 8.5+/-0.1 to 53.7+/-2.3 microg x l(-1). Cephapirin was found in two samples at 5.7+/-0.1 and 6.4+/-0.3 microg x l(-1).

Monitoring of ampicillin and its related substances by NMR

A 1H NMR procedure for the monitoring of ampicillin (Amp) and its main related substance in different media, has been developed. The characteristics peak of Amp, 6-aminopenicillanic acid (6-APA), phenylglycine (PhG), and penicilloic acid in the range of 0.5-0.9 and 3.0-4.5 ppm were used for their identification in drugs and serum samples. The quantitative works were performed based on the intensity of protons of the methyl group link to the beta-lactam cyclic of Amp and 6-APA and the aromatic protons of PhG relative to the protons of methylene group of maleic acid, as internal standard, at constant temperature. The resulting data are compared with those obtained with an HPLC method proposed by British Pharmacopoeia. Statistical studies show that, at a confidence limit of %95, there is no significant difference between the two methods. In comparison with the HPLC method, the proposed NMR method does not require any sample pretreatment, standard solution preparation, long analysis time and use of any carcinogenic solvent. The method was applied to the determination of Amp and its related substances in synthetic mixtures, drug powders and serum samples.

Screening and mass spectral confirmation of beta-lactam antibiotic residues in milk using LC-MS/MS

Milk is typically screened for beta-lactam antibiotics by nonspecific methods. Although these methods are rapid and sensitive, they are not quantitative and can yield false positive findings. A sensitive and specific method for the quantitation and mass spectral confirmation of five beta-lactam and two cephalosporin antibiotics commonly or potentially used in the dairy industry is described using high-performance liquid chromatography with tandem mass spectrometry. The antibiotics studied were ampicillin, amoxicillin, penicillin G, penicillin V, cloxacillin, cephapirin, and ceftiofur. The antibiotics were extracted from milk with acetonitrile, followed by reversed-phase column cleanup. The extract was analyzed by liquid chromatography coupled with a mass spectrometer, using a water/methanol gradient containing 1% acetic acid on a C-18 reversed-phase column. Determination was by positive ion electrospray ionization and ion trap tandem mass spectrometry. Quantitation was based on the most abundant product ions from fragmentation of the protonated ion for amoxicillin, cephapirin, ampicillin, and ceftiofur and on the fragmentation of the sodium adduct for penicillin G, penicillin V, and cloxacillin. The method was validated at the U.S. FDA tolerance or safe level and at 5 or 2.5 ng/mL for these compounds in bovine milk. Theoretical method detection limits in milk based on a 10:1 signal to noise ratio were 0.2 ng/mL (ampicillin), 0.4 ng/mL (ceftiofur), 0.8 ng/mL (cephapirin), 1 ng/mL (amoxicillin and penicillin G), and 2 ng/mL (cloxacillin and penicillin V) using a nominal sample size of 5 mL.

Simultaneous determination of five beta-lactam antibiotics in bovine milk using liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A multiresidue method for the detection of five important beta-lactam antibiotics (amoxicillin, ampicillin, cloxacillin, oxacillin, penicillin G) in fresh milk is presented that allows quantitation of the analytes well below established legislative limits. The method avoids the use of acid during the extraction procedure and entails a cleanup step over a C18 cartridge. The analytes are separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) using a stable isotope-labeled internal standard. Mass spectral acquisition is done in the positive ion mode by applying selected reaction monitoring of two or more fragmentation transitions per analyte to provide a high degree of sensitivity and specificity. The typical recoveries for all five beta-lactams in fresh milk ranged from 76 to 94% at a fortification level of 4 microg/kg. This study also addresses common problems encountered in the stability of penicillins during sample preparation as well as the employment of postcolumn infusion of a standard compound to verify potential matrix-induced signal suppression in ESI-MS.

Application of ion-exchange cartridge clean-up in food analysis III. Determination of benzylpenicillin, phenoxymethyl-penicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in bovine liver and kidney by liquid chromatography with ultraviolet detection

A multiresidue analytical method was developed for the simultaneous determination of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine liver and kidney. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from bovine liver spiked at levels of 0.5 mg/kg and 0.1 mg/kg were in the range of 73-91% and 83-96% with coefficients of variation of 1.4-4.2% and 3.4-8.7%, respectively. For bovine kidney spiked at levels of 0.5 mg/kg and 0.1 mg/kg, the recoveries of these compounds were 79-92% and 82-92% with RSDs of 1.8-5.9% and 2.7-7.8%, respectively. The detection limits for the six penicillins were 0.02-0.05 mg/kg in bovine liver and kidney.

Simultaneous determination of seven penicillins in muscle, liver and kidney tissues from cattle and pigs by a multiresidue high-performance liquid chromatographic method

A high-performance liquid chromatographic (HPLC) method based on solid-phase extraction (SPE) was developed for determination of amoxicillin, penicillin G (benzylpenicillin), ampicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in muscle, liver and kidney tissues of pigs and cattle. The compounds were extracted in aqueous solution by precipitation of organic materials with a mixture of sulphuric acid and sodium tungstate. The extract was cleaned up by SPE on a divinylbenzene-co-N-vinylpyrrolidone polymeric sorbent. Further clean-up was performed by liquid-liquid partition with diethyl ether. The extract was derivatised with benzoic anhydride and 1,2,4-triazole mercury (II) reagent. Chromatography was performed by reversed-phase gradient HPLC on a C18 column with ultraviolet detection at 323 nm. The limits of detection estimated by a conservative model were in the range 8.9-11.1 microg/kg for amoxicillin, penicillin G, ampicillin, oxacillin, cloxacillin and nafcillin and 18.3-20.9 microg/kg for dicloxacillin. The mean recovery range was 66-77% for amoxicillin, 73-75% for penicillin G, 81-82% for ampicillin, 73-76% for oxacillin, 74-75% for cloxacillin, 66-72% for nafcillin and 58-65% for dicloxacillin.

Application of ion-exchange cartridge clean-up in food analysis. II. Determination of benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in meat using liquid chromatography with ultraviolet detection

A multiresidue analytical method was developed for the simultaneous determination of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in meat. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from pork muscle spiked at levels of 0.5, 0.1 and 0.05 mg/kg were in the range of 77-90, 73-95 and 80-93% with coefficients of variation of 0.5-1.7, 1.6-4.4 and 3.2-6.6%, respectively. For beef muscle spiked at levels of 0.5, 0.1 and 0.05 mg/kg, the recoveries of these compounds were 83-92, 71-86 and 77-90% with coefficients of variation of 1.7-4.4, 2.6-7.0 and 3.9-6.4%, respectively. The detection limits for each penicillin were 0.02 mg/kg in meat.

Simultaneous determination of beta-lactam antibiotics in milk by ion-pair liquid chromatography

A simple and rapid ion-pairing liquid chromatographic method was developed for the simultaneous determination of five penicillins (PCs), ampicillin (AB-PC), benzylpenicillin (PC-G), Dicloxacillin (MDI-PC) and nafcillin (NF-PC) in milk. These PCs are most frequently used for the treatment of mastitis of cows. These antibiotics were extracted with acetonitrile from milk and cleaned up by solid-phase extraction with a C18 cartridge. PCs were separated on a Kaseisorb LC ODS-300-5 column with a mobile phase (1 ml/min) of acetonitrile-methanol-0.05 M potassium dihydrogenphosphate (20:10:80, v/v/v) mixture containing 5 mM of sodium 1-decanesulfonate adjusted to pH 3.5 and UV detection at 210 nm. The average recoveries of five PCs from milk fortified at 0.5 and 1.0 micrograms/ml (n = 5) were 79.8-89.4% with relative standard deviations ranging from 2.7 to 7.2% The detection limit of PCs in milk were 0.03-0.05 microgram/ml.

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.