Target and Suspect Screening of Pharmaceuticals and their Transformation Products in the Klip River, South Africa, using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry

In spite of recent reports about the presence of pharmaceuticals in African water bodies, their prevalence has still not been sufficiently quantified. The few available studies have mostly focused on a limited number of pharmaceuticals. In the present study, a suspect screening of 92 compounds (mainly pharmaceuticals and their transformation products) along the Klip River, South Africa was conducted, followed by target monitoring of 21 of the detected pharmaceuticals. The experimental approach was based on solid-phase extraction followed by analysis with ultra-high-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UHPLC-QTOF-MS). The results revealed 47 pharmaceuticals, 31 of which were detected for the first time in South African waters. Seven detected pharmaceuticals (propyphenazole, sulfamerazine, levamisole, tryptophan, dibucaine, albuterol, and fenpropimorph) are not approved medications in South Africa. Six pharmaceutical metabolites were detected for the first time in South Africa. Pharmaceuticals with the highest concentrations in river water were flumequine (0.257 µg L^-1 ), oxolinic acid (0.355 µg L^-1 ), and acetaminophen (0.432 µg L^-1 ). Oxolinic acid presented the highest hazard quotient, 48.6, indicating a risk of toxicity to aquatic organisms. Hazard quotients for other pharmaceuticals were below 1, except that of flumequine, which reached 1.285. These results suggest a need for further research into the fate of pharmaceuticals in surface waters, and a quantification of the risks associated with the identified drugs because they are likely to accumulate in the tissues of fish/aquatic organisms, thus affecting humans. Environ Toxicol Chem 2022;41:437-447. © 2021 SETAC.

Development and validation of a method for the simultaneous extraction and separate measurement of oxytetracycline, florfenicol, oxolinic acid and flumequine from marine sediments

A simple and rapid method for the detection and extraction of oxolinic acid, flumequine, florfenicol and oxytetracycline from marine sediments was developed and validated. The analytes were extracted from the marine sediment using a solution of oxalic acid diluted in methanol with sonication before detection by HPLC using a diode-array detector (florfenicol and oxytetracycline) and fluorescence (oxolinic acid and flumequine). The quantification limits (QL) were 100 ng/g for oxytetracycline and florfenicol and 5 ng/g for oxolinic acid and flumequine. The coefficients of variation of the repeatability and intermediate precision were less than 10% in all of the analytes. The calibration curves were linear between 50 and 500 ng/ml for oxytetracycline and florfenicol and 1 and 20 ng/ml for oxolinic acid and flumequine. The recuperation rate for the analytes was above 86%.

Salmon aquaculture and antimicrobial resistance in the marine environment

Antimicrobials used in salmon aquaculture pass into the marine environment. This could have negative impacts on marine environmental biodiversity, and on terrestrial animal and human health as a result of selection for bacteria containing antimicrobial resistance genes. We therefore measured the numbers of culturable bacteria and antimicrobial-resistant bacteria in marine sediments in the Calbuco Archipelago, Chile, over 12-month period at a salmon aquaculture site approximately 20 m from a salmon farm and at a control site 8 km distant without observable aquaculture activities. Three antimicrobials extensively used in Chilean salmon aquaculture (oxytetracycline, oxolinic acid, and florfenicol) were studied. Although none of these antimicrobials was detected in sediments from either site, traces of flumequine, a fluoroquinolone antimicrobial also widely used in Chile, were present in sediments from both sites during this period. There were significant increases in bacterial numbers and antimicrobial-resistant fractions to oxytetracycline, oxolinic acid, and florfenicol in sediments from the aquaculture site compared to those from the control site. Interestingly, there were similar numbers of presumably plasmid-mediated resistance genes for oxytetracycline, oxolinic acid and florfenicol in unselected marine bacteria isolated from both aquaculture and control sites. These preliminary findings in one location may suggest that the current use of large amounts of antimicrobials in Chilean aquaculture has the potential to select for antimicrobial-resistant bacteria in marine sediments.

Are liquid chromatography/electrospray tandem quadrupole fragmentation ratios unequivocal confirmation criteria?

Multiple reaction monitoring (MRM) ratios as provided by tandem mass spectrometers are used to confirm positive residue findings (e.g. veterinary drugs or pesticides). The Commission Decision 2002/657/EEC defines tolerance levels for MRM ratios, which are intended to prevent the reporting of false positives. This paper reports findings where blank sample extracts have been spiked by a drug (difloxacin) and the corresponding measured MRM ratios significantly deviated from MRM ratios observed in matrix-free solution. The observation was explained by the formation of two different [M+H](+) analyte ions within the electrospray ionization (ESI) interface. These two ions vary only by the site of analyte protonation. Since they are isobaric, they are equally transmitted through the first quadrupole, but are differently fragmented in the collision chamber. The existence of two isobaric ions was deduced by statistical data and the observation of a doubly charged analyte ion. It was hypothesized that the combined presence of [M+H](+) and [M+2H](2+) implies the existence of two different singly charged ion species differing only by the site of protonation. Low- and high-energy interface-induced fragmentation was performed on the samples. The surviving precursor ion population was mass selected and again fragmented in the collision chamber. Equal product ion spectra would be expected. However, very different product ion spectra were observed for the two interface regimes. This is consistent with the assumption that the two postulated isobaric precursor ions show different stability in the interface. Hence the abundance ratio among the two types of surviving precursor ions will shift and change the resulting product ion spectra. The existence of the postulated singly charged ions with multiple chargeable sites was finally confirmed by successful ion mobility separation.

Degradation of oxolinic acid and flumequine in aquaculture pond waters and sediments

Oxolinic acid (OA) and flumequine (FLU) are two of the quinolone antibiotics (QAs) that are widely used in aquaculture. The purpose of this study was to understand the fates of OA and FLU in waters and sediment slurries from aquaculture ponds in a laboratory experiment. Waters and sediments were sampled from an eel (Anguilla japonica) pond and a shrimp (Penaeus vannamei) pond. The effects of light, microbial activities, and temperature on the degradation of these two QAs were elucidated. Results indicated that light plays a major role in the degradation of OA and FLU in waters and sediment slurries. Under illuminated and non-sterile conditions, the half-lives (t(1/2)) of OA were 2.3-4.8 and 9.5-15.0 days in the waters and sediment slurries, respectively. For FLU, under the same conditions, t(1/2) values were 1.9-2.3 and 3.6-6.4 days, respectively. Photodegradation of OA and FLU was much faster in water than in sediment slurry. In both environments, degradation became very slow or would plateau after only minimal change in the dark. Besides the effect of light, biodegradation had very minor effects on the degradation of the two QAs in the sediment slurries. The only independent biodegradation was found when OA was placed in shrimp pond sediment slurry, but at a much lower rate (t(1/2) of 98.7 days) than in light. Biodegradation of FLU was also found in the eel pond sediment slurry but only through an additional connection with light. Also, re-addition enhanced the degradation of OA in shrimp pond sediment slurry, but slowed the degradation of FLU in the eel pond sediment slurry in the dark. The temperature experiment in this study showed no significant effects on degradation of the two QAs in either pond waters or sediment slurries.

Residuos de tetraciclina y quinolonas en peces silvestres en una zona costera donde se desarrolla la acuicultura del salmón en Chile

The presence of residues of tetracycline, quinolones and antiparasitic drugs was investigated in wild fish captured around salmon aquaculture pens in Cochamó, Region X, Chile. Residues of both antibiotics were found in the meta [corrected] of two species of wild fish that are consumed by humans, robalo (Elginops maclovinus) and cabrilla (Sebastes capensis) [corrected] These findings suggest that the antibiotic usage in salmon aquaculture in Chile has nvironmental implications that may affect human and animal health. More studies are needed in Chile to determine the relevance of these findings for human and animal health and the environment to regulate this use of antibiotics.

Multiresidue determination of eleven quinolones in milk by liquid chromatography with fluorescence detection

A liquid chromatographic method with fluorescence detection was developed for simultaneous determination of norfloxacin, ofloxacin, ciprofloxacin, pefloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid, and flumequine in milk The samples were extracted with 10% trichloroacetic acid/acetonitrile (9 + 1, v/v) and cleaned by Strata-X reversed-phase solid-phase extraction cartridges. The 11 quinolones were separated on a reversed-phase C18 column (Hypersil BDS-C18) with mobile phase gradient elution and detected with fluorescence by means of a wavelength program. The recoveries for milk fortified with the 11 quinolones at 3 levels were 69-88% with acceptable relative standard deviations of <9% (intraday) and <14% (interday). The limits of detection were 23 microg/L for enrofloxacin, and 1-9 microg/L for the other 10 quinolones.

Antibiotic resistance in bacteria from shrimp farming in mangrove areas

Shrimp farming is a sufficiently large and mature industry to have an effective range of antimicrobial agents for most bacterial diseases in shrimp culture. However, at present, there exists great concern over the widespread use of antibiotics in aquaculture, which may result in residue of antibiotics in water and mud, and subsequently, the development of antibiotic resistance in bacteria in the environment. There is limited understanding about the effect of antibiotic residues on bacteria resistance in shrimp farming environment. Therefore, a study was conducted to investigate bacterial resistance to Norfloxacin (NFXC), Oxolinic Acid (OXLA), Trimethoprim (TMP) and Sulfamethoxazole (SMX), which were found in four shrimp farming locations in mangrove areas in Vietnam. Findings indicate that there is a relatively high incidence of bacteria resistance to these antibiotics observed in most of the studied sites, particularly to antibiotics with concentration of 0.1 microg/ml. Yet the relation between concentration of antibiotic residues and incidence of antibiotic resistance is not clearly defined. Among individual antibiotics, the incidence of resistance to TMP and SMX was higher than the others. Identification of bacteria isolated from mud samples by DNA analyzer shows that Bacillus and Vibrio are predominant among bacteria resistant to the antibiotics. The result of the study also indicates that these antibiotics in media degraded more rapidly due to the presence of resistant bacteria.

Multiresidue method for simultaneous determination of ten quinolone antibacterial residues in multimatrix/multispecies animal tissues by liquid chromatography with fluorescence detection: single laboratory validation study

Quinolone antibacterials are veterinary drugs authorized for use in food animal production. The analysis of residual amounts of drugs in food from animal origin is important for quality control of products for consumers. For this purpose, Maximum Residue Limits (MRLs) have been set up by a European Union Council Regulation on Veterinary Drug Residues (No. 90/2377/EEC and subsequent), and 8 quinolones received MRLs at concentration levels depending on both the matrix and the animal species of interest. A method was developed for screening and confirming 10 quinolone residues (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, oxolinic acid, sarafloxacin) in a wide variety of matrixes of different animal species. It involves extraction of the residues from the biological tissues/fluids by acidic aqueous solution, centrifugation and filtration prior to injection on a C18 narrow-bore column, and detection through a 3-step-mode fluorescence detector. The method was validated during a 2-week study for a set of 8 species-matrixes (i.e., bovine raw milk, bovine muscle, porcine muscle, porcine kidney, porcine liver, fish flesh and skin, poultry muscle, whole egg). Residues were quantified down to 15 microg/kg with limits of detection and quantitation ranging from 4 to 11 and 13 to 36 microg/kg, respectively, which are sufficient compared to the wide range of MRLs set for these substances (from 30 microg/kg for danofloxacin in milk to 1900 microg/kg for difloxacin in poultry liver). The limit of performance of the method in terms of CCalpha and CCbeta, the critical concentrations stated in the Decision No. 2002/657/EC and the ISO Standard No. 11843, has been calculated for the authorized (MRL) substances but only estimated in the case of the nonauthorized (non-MRL) substances.

Micellar electrokinetic chromatography for determination of drug partition in phospholipids

The lipophilicity of pipemidic, nalidixic and oxolinic acids was determined by forming phospholipidic micelles directly in an electrophoretic capillary. Phosphatidylcholine derivatives, namely L-alpha-dilauroyl phosphatidylcholine (DLPC) or L-alpha-dimiristoyl phosphatidylcholine (DMPC), were added in the run buffer (50 mM phosphate buffer at pH 7.4). To obtain a mixed micelle, phospholipidic derivatives and sodium cholate were together added in the run buffer. Considering the increasing of migration time when phosphatidylcholine derivative is added in the run buffer, Ks can be determined and then quinolones lipophilicity.

The bryophyte Fontinalis antipyretica Hedw. bioaccumulates oxytetracycline, flumequine and oxolinic acid in the freshwater environment

In recent years, the fate of pharmacological substances in the aquatic environment have been more and more studied. Oxolinic acid (OA), flumequine (FLU) and oxytetracycline (OTC) are commonly used antibacterial agents. A large amount of these drugs is released into water directly by dissolved fraction and indirectly in urine and feces. Monitoring these compounds in the freshwater environment is difficult because of the lack of suitable indicators. The aim of this work was to evaluate the OA, FLU and OTC bioaccumulation abilities of Fontinalis antipyretica Hedw., known for heavy metal bioaccumulation. The experiment described was decomposed for two times: a 10-days accumulation period during which bryophytes were in contact with antibiotics and a 15-days post-exposure period during which bryophytes were in water with no antibiotic. This experiment showed that this bryophyte strongly accumulates OA, FLU and OTC in freshwater. Bioaccumulation factors (ratio of concentrations in bryophyte and water) ranged between 75 and 450. Moreover, OA, FLU and OTC persisted in the bryophyte for a long time with clearance between 0.19 and 3.04 ng/g/day. Mean residence times ranged between 18 and 59 days. Accumulation and decontamination mechanism models were proposed.

Experimental study on the bioaccumulation of oxytetracycline and oxolinic acid by the blue mussel (Mytilus edulis). An evaluation of its ability to bio-monitor antibiotics in the marine environment

The ability of blue mussel (Mytilus edulis) to act as a potential antibiotic bioindicator in marine waters was experimentally tested by the study of the kinetics of two veterinary antibiotics (oxolinic acid: OA and oxytetracycline: OTC). Antibiotic uptake was fast in the soft parts of the mussels. OA was quickly eliminated while OTC was released more slowly (half-life in viscera=3.9 days). OA and OTC were preferentially accumulated in gills and in viscera, respectively. Bio-accumulation factors were low (maximum: 2 for OTC in viscera) in accordance with the low K(ow)s. It was assumed that the higher OTC bioaccumulation pattern was related to its binding to mineral and organic compounds that led to its activity inhibition (62%). The antibiotics were persistent in shells (OTC half-life=8.3 days). Most veterinary and human antibiotics such as tetracyclines and sulphonamides have low log K(ow)(<2) and should weakly accumulate in mussel. This might limit the use of blue mussel to bio-monitor antibiotics in the marine environment.

High-performance liquid chromatographic method with fluorescence detection for the screening and quantification of oxolinic acid, flumequine and sarafloxacin in fish

A previously published liquid chromatographic method for determining residues of nine quinolones in chicken, porcine, bovine and ovine muscle was adapted and applied to fish tissue for simultaneous determination of three quinolones (flumequine, oxolinic acid and sarafloxacin). The analytes were extracted from homogenised muscle using an acetonitrile basic solution. After centrifugation, partial evaporation and cleaning with hexane, direct injection was possible. Separation was achieved on PLRP-S column and detection was performed with a programmable fluorescence detector. Chromatographic conditions were optimised to be compatible with the determination of the three quinolones in a single run. The linearity, recovery, accuracy and precision of the method were evaluated from fortified tissue samples at concentration levels ranging from 15 to 120 microg kg(-1) for sarafloxacin and 75 to 600 microg kg(-1) for oxolinic acid and flumequine according to the EU maximum residue limit of each quinolone. The limits of detection were estimated to be 2, 5 and 7 microg kg(-1), respectively, for sarafloxacin, oxolinic acid and flumequine. The limits of quantification were validated at 15 microg kg(-1) for sarafloxacin and 75 microg kg(-1) for oxolinic acid and flumequine. Mean extraction recoveries of quinolones in fish ranged from 56.9 to 71.0%. This simple and rapid method is suitable for residue control.

[Determination of oxolinic acid residues in baked and fresh eels by high performance liquid chromatography without derivatization]

A method for rapid determination of oxolinic acid residues in baked eels and fresh eels by high performance liquid chromatography without derivatization was studied. The samples were triturated, and extracted with methylene dichloride. The extracted solutions were evaporated to dryness, and then was dissolved by using the mobil phase. The solutions were cleaned-up by partition with n-hexane before analysis. The components were analysed on a Nova-Pak C18 column (150 mm x 3.9 mm i.d., 5 microm), with methanol-diluted phosphoric acid (pH 2.5) (40:60, V/V) as the mobile phose at a flow rate of 0.8 mL/min and detected by a fluorescence detector at the excitation wavelength (lambdaex) 254 nm and the emission wavelength (lambdaem) 375 nm. The detection limit was 0.01 mg/kg (S/N = 3). The recoveries were over 80 %, and the relative standard deviations (RSDs) were less than 3.8%.

Determination of oxolinic acid in the bryophyte Fontinalis antipyretica by liquid chromatography with fluorescence detection

A large amount of oxolinic acid administered in freshwater fish farms reaches the environment. In order to allow environmental monitoring, an HPLC method to determine oxolinic acid in the bryophyte Fontinalis antipyretica was developed. Nalidixic acid was used as an internal standard. Oxolinic and nalidixic acids were extracted by cracking the bryophytes in liquid nitrogen with 0.1 M acid oxalic solution in ethyl acetate and a liquid-liquid clean up procedure was then performed. Mobile phase was a 0.02 M orthophosphoric acid aqueous solution-acetonitrile mixture (70:30, v/v). The stationary phase was 5 microm PuroSpher RP18e and quinolones were detected by fluorescence. The linearity, accuracy and precision of this method were demonstrated by a validation assay. The limits of detection and quantitation were 1 and 10 ng/g respectively. The linearity range was 10 to 500 ng/g. This method was applied to a 25 days experimental study performed with the bryophyte Fontinalis antipyretica.

[Oxytetracycline and oxolinic acid residues in kuruma prawn (Penaeus japonicus) and the effect of cooking procedures on the residues]

Tissue distribution and residue depletion of oxytetracycline (OTC) and oxolinic acid (OA) were studied in the kuruma prawn (Penaeus japonicus). The prawn were kept in tanks with recirculated artificial seawater at a salinity of 22-23@1000. The water temperature was maintained at 25 degrees C. The average body weight was 22.9 +/- 4.9 g for OTC and 22.5 +/- 3.6 g for OA. The drug was mixed with the diet and orally administered through a catheter to the prawn. The doses of OTC and OA, respectively, were 50 mg/kg body weight. At each sample time, four prawns were sacrificed and tissues were sampled. OTC and OA levels were determined by high-performance liquid chromatography. At the highest levels, the concentrations of OTC were in the other: shell (13.57 micrograms/g) > hemolymph (12.20 micrograms/mL) > muscle (8.30 micrograms/g). For OA, the order was: shell (20.74 micrograms/g) > hemolymph (7.06 micrograms/mL) > muscle (2.05 micrograms/g). The elimination half-lives of hemolymph and muscle were 44.7 and 46.8 hours for OTC and 55.0 and 107.9 hours for OA, respectively. Residual OTC could not be detected in hemolymph and muscle at 20 days after dosing. Residual OA disappeared from hemolymph and muscle at 25 days after dosing. A 25-day period for OTC and 30-day period for OA could be regarded as the proper withdrawal time established for kuruma prawn by the Pharmaceutical Law in Japan. However, the elimination half-lives of shell for OTC and OA could not be calculated because both drug residues persisted in shell tissues, and the elimination phase was not completed during the experimental period. Residual OTC (14.10 +/- 2.26 micrograms/g, n = 6) and OA (0.32 +/- 0.06 microgram/g, n = 7) were detected in exuviae at 3 days and 4 days after dosing, respectively. Residual OTC was reduced to 50-70% in muscle by the usual methods of cooking (boiling, baking at 200 degrees C and frying at 180 degrees C), whereas reduction levels in shell were only 20-30%. Residual OA was reduced to 20-30% in muscle and shell by the cooking. These results confirm that the cooking procedures could only reduce but not completely eliminate these drug residues in prawn.

Determination of residues of oxolinic acid and flumequine in freeze-dried salmon muscle and skin by HPLC with fluorescence detection

A procedure for the determination of residues of oxolinic acid (OA) and flumequine (FLU) in freeze-dried salmon muscle with attached skin, using reversed-phase high-performance liquid chromatography, is described. OA and FLU were extracted by a solid-liquid extraction procedure: after addition of hydrochloric acid, extraction used successively ethyl acetate, sodium hydroxide and chloroform. Liquid chromatography was performed on a 5 microm PuroSpher RP-18E cartridge using acetonitrile and 0.02 M aqueous orthophosphoric acid solution as mobile phase, with fluorescence detection. The performance of the method was established by spiking tissues with OA and FLU before the freeze-drying step. The method was linear over the concentration range 50-2000 ng/g freeze-dried tissue. Limits of detection and quantitation were 3.2 and 16 ng/g wet weight tissue respectively both for OA and FLU. Mean extraction recoveries of OA and FLU from freeze-dried tissue were 85.5 and 85.2% respectively. The method is suitable as a regulatory one for determination of residues of OA and FLU in freeze-dried salmon tissue.

Using nonaqueous capillary electrophoresis to analyze several quinolones in pig kidney samples

We show the potential of nonaqueous capillary electrophoresis (NACE) for analyzing enrofloxacin (ENR), ciprofloxacin (CPR), danofloxacin (DAN), difloxacin (DIF), marbofloxacin (MAR), flumequine (FLU), and oxolinic acid (OXA) in pig kidney samples. We have studied the effects of parameters such as the composition of the organic media, the choice of electrolyte, the pH* of the background electrolyte (BGE), the addition of modifiers, and the reversal of electroosmotic flow. Separation was good with 20 mM ammonium acetate, 0.004% polycation hexadimethrine bromide (HDB), and 4% acetic acid (pH* 5.4) in methanol/acetonitrile (50:50 v/v) medium. We used a quick and simple sample preparation method, hydrochloric acid as an extractant and solid-phase extraction (SPE) with Baker C18 cartridges as the cleanup step. Recoveries for all quinolones were over 80%.

Fast-scanning fluorescence spectroscopy as a detection system in liquid chromatography for confirmatory analysis of flumequine and oxolinic acid

Oxolinic acid and flumequine were analysed by reversed-phase liquid chromatography after extraction from the sample matrix with dichloromethane and partitioning with NaOH. The detection system consisted of a fast-scanning fluorescence detector, which provides the full spectra of the eluting peaks and can thus be used to confirm the identity of analytes. Determination was performed by partial least squares (PLS) and three-way PLS over the three-dimensional data, i.e. fluorescence intensity versus retention time and excitation wavelength. In both cases, similar results, with prediction errors around 4%, were obtained. The method was successfully applied to the analysis of salmon, pork and chicken muscle spiked up to 300 ng g(-1).

High-performance liquid chromatographic determination of oxolinic acid and flumequine in the live fish feed artemia

A high-performance liquid chromatography (HPLC) analytical method for the determination of oxolinic acid and flumequine in Artemia nauplii is described. The samples were extracted and cleaned up by a solid-phase extraction (SPE) procedure using SPE C18 cartridges. Oxolinic acid and flumequine were determined by reversed-phase HPLC using a mobile phase of methanol-0.1 M phosphate buffer, pH 3 (45:55, v/v) and a UV detection wavelength of 254 nm. Calibration curves were linear for oxolinic acid in the range of 0.2-50 microg/g (r2=0.9998) and for flumequine in the range of 0.3-50 microg/g (r2=0.9994). Mean recoveries amounted to 100.8% and 98.4% for oxolinic acid and flumequine, respectively. The quantification limit was 0.2 microg/g for oxolinic acid and 0.3 microg/g for flumequine. Quantitative data from an in vivo feeding study indicated excellent uptake of both drugs by Artemia nauplii.

Determination of oxolinic acid in faeces and urine of turbot (Scophthalmus maximus) by high-performance liquid chromatography using fluorescence detection

A procedure for the determination of oxolinic acid (OA) in faeces and urine of turbot (Scophthalmus maximus), using reversed-phase high-performance liquid chromatography is described. Liquid chromatography was performed on a 5-microm PuroSpher RP-18E cartridge using acetonitrile and 0.001 M aqueous orthophosphoric acid solution as mobile phase, with fluorescence detection. After the addition of an internal standard, oxolinic acid was extracted by using a liquid-liquid extraction procedure. Linearity and precision were checked over the concentration ranges 1.0-1000 microg/g (faeces) and 0.06-10.00 microg/ml (urine). Limits of detection of OA in faeces and urine were 0.20 microg/g and 0.02 microg/ml respectively. Mean extraction recoveries of OA from faeces and urine were 102.0 and 91.6% respectively.

Automated multi-residue isolation of fluoroquinolone antimicrobials from fortified and incurred chicken liver using on-line microdialysis and high-performance liquid chromatography with programmable fluorescence detection

Isolation of the quinolones, sarafloxacin (SAR), oxolinic acid (OXA), and flumequine (FMQ), from fortified chicken liver tissues, and SAR incurred chicken liver tissues was achieved by combined liquid-liquid extraction and aqueous on-line microdialysis using the automated trace enrichment of dialysates (ASTED) system. Analysis of tissue isolates after ASTED clean-up was performed using reversed-phase HPLC and programmable fluorescence detection. Overall recoveries of SAR, OXA and FMQ from samples fortified over a concentrations range of 1-100 ppb were 94, 97 and 87% with overall inter-assay variability of 4.2, 4.1 and 3.6%, respectively. Chicken liver samples incurred with SAR at three concentration levels also were tested by the ASTED method. The method exhibited high peak resolution (3.4-4.2 on average), a high signal-to-noise ratio, and demonstrated good precision. The ASTED-HPLC method overall had a lower limit of detection (LOD) of 0.2 ppb, and a limit of quantitation (LOQ) of 1 ppb.

Liquid chromatographic determination of flumequine, nalidixic acid, oxolinic acid, and piromidic acid residues in catfish (Ictalurus punctatus)

A peer-verified, liquid chromatographic (LC) method for simultaneous determination of residues of flumequine (FLU), nalidixic acid (NAL), oxolinic acid (OXO), and piromidic acid (PIR) in catfish muscle is presented. Sample workup involves homogenizing tissue with acetone, defatting with hexane, and extracting quinolones into chloroform. Sample is purified further by partitioning into base and then subsequently back-extracting into chloroform after acidifying the aqueous phase. After solvent is evaporated, the residue is diluted with mobile phase, and analytes are introduced into an LC system where separations are made with a 5 microns, reversed-phase polymer column and an isocratic, buffered acetonitrile-tetrahydrofuran mobile phase. Determinations are made by UV detection at 280 nm for PIR and by fluorescence detection (excitation at 325 excitation and emission at 365 nm) for the other 3 analytes. Each quinolone was used to fortify catfish muscle at 5, 10, 20, 40, and 80 ng/g. The following recoveries and relative standard deviation (RSD) values represent an average of the 5 levels for each analyte: FLU, 79.7% (RSD = 5.7%); OXO, 80.8% (RSD = 6.3%); PIR, 75.0% (RSD = 5.9%); and NAL, 87.1% (RSD = 10%). Assay of 5 levels (base incurred catfish, plus 4 dilutions with control catfish) of catfish muscle incurred with the 4 quinolones gave the following averages: FLU: base, 198 ng/g (RSD = 2.3%); dilutions, 98.0 ng/g (RSD = 4.2%), 61.6 ng/g (RSD = 4.4%), 21.6 ng/g (RSD = 2.8%), 9.24 ng/g (RSD = 8.7%); OXO, base, 257 ng/g (RSD = 6.9%); dilutions, 146 ng/g (RSD = 5.5%), 95.0 ng/g (RSD = 4.1%), 30.7 ng/g (RSD = 3.8%), 13.7 ng/g (RSD = 4.6%); PIR, base, 22.1 ng/g (RSD = 4.2%); dilutions, 13.7% ng/g (RSD = 6.7%), 6.49 ng/g (RSD = 15%), 2.65 ng/g (RSD = 15%); and NAL, base, 75.1 ng/g (RSD = 3.8%); dilutions, 42.3 ng/g (RSD = 5.1%), 24.1 ng/g (RSD = 6.3%), 8.59 ng/g (RSD = 4.8%). A second multiresidue analysis of the 4 quinolones was performed by an outside analyst. Average recoveries from catfish fortified at 5, 10, 20, and 40 ng/g were FLU, 75.9% (RSD = 4.0%); OXO, 84.0% (RSD = 5.5%); NAL, 85.6% (RSD = 8.9%); and PIR, 66.2% (RSD = 8.7%).

Rapid and simple determination of oxolinic acid and oxytetracycline in the shell of the blue mussel (Mytilus edulis) by high-performance liquid chromatography

A simple procedure for the determination of oxolinic acid (OA) and oxytetracycline (OTC), two antibacterial agents, in the shell of the blue mussel (Mytilus edulis), using reversed-phase high-performance liquid chromatography is described. Liquid chromatography was performed on a 5-microm LiChroSpher 100 RP-18E column using acetonitrile and a 0.02 M orthophosphoric acid solution as the mobile phase, with ultraviolet detection. After roughly grinding the shell, drugs were extracted using a methanolic oxalic acid solution. Linearity and precision were checked over the concentration range 0.04-0.32 microg/g. Limits of detection of OA and OTC were 0.012 and 0.008 microg/g, respectively. Mean extraction recoveries of OA and OTC from mussel shell were 72.9 and 65.4%, respectively. To demonstrate the usefulness of the analytical procedure, an experimental study was performed in blue mussels exposed to the drugs for eight days.

Determination and confirmation of identities of flumequine and nalidixic, oxolinic, and piromidic acids in salmon and shrimp

A previously published liquid chromatographic (LC) method for determining residues of flumequine (FLU) and nalidixic (NAL), oxolinic (OXO), and piromidic (PIR) acids in catfish tissue was applied to salmon and shrimp muscle. Identities of all 4 residues in salmon and shrimp were confirmed by gas chromatography/mass spectrometry (GC/MS). The tissue is homogenized with acetone, the acetone extract is defatted with hexane, and the quinolones are extracted into chloroform. The extract is further purified by first partitioning into base and then back-extracting from a solution acidified to pH 6.0. Analytes are determined by LC with simultaneous UV and fluorescence detection. Muscle tissue was fortified with each quinolone at 5, 10, 20, 40, and 80 ng/g. Average recoveries and relative standard deviations (RSDs) for salmon, which represent an average of the 5 levels for each analyte, ranged from 75.9 to 90.8% and from 2.25 to 6.40%, respectively. Average recoveries and RSDs for shrimp ranged from 81.3 to 91.2% and from 7.34 to 10.7%, respectively. Identities of OXO, FLU, NAL, and PIR were confirmed in extracts of salmon and shrimp tissue fortified at 10 ng/g by determination of decarboxylated quinolones by GC/MS. Four diagnostic ions were monitored for OXO, FLU, and PIR, and 5 ions were monitored for NAL. All ion relative abundances were within 10% of those calculated for standard decarboxylated quinolones. Optimum conditions for decarboxylation and GC/MS confirmation are given.

High-performance liquid chromatographic method for the rapid and simultaneous determination of sulfamonomethoxine, miloxacin and oxolinic acid in serum and muscle of cultured fish

A rapid method for the simultaneous determination of sulfamonomethoxine (SMM), miloxacin (MLX) and oxolinic acid (OA) in serum and muscle of cultured fish by high-performance liquid chromatography has been developed. A Hisep shielded hydrophobic phase column (15 cm x 4.6 mm I.D.) and a mobile phase of 0.05 M citric acid-0.2 M disodium hydrogenphosphate buffer, pH 2.5 in 10 mM tetra-n-butyl ammonium bromide-acetonitrile (85:15) with ultraviolet detection at 265 nm were used. The recoveries of SMM, MLX and OA from serum and muscle samples were 72-101%. The detection limits of the three drugs were 0.05-0.1 microgram/ml or g of sample.

High-performance liquid chromatographic determination of oxolinic acid residues in fish silage

A sensitive high-performance liquid chromatographic procedure was developed for the determination of oxolinic acid in fish silage. Oxolinic acid was extracted with a mixture of McIlvaine buffer (pH 3.6) and methanol (55:45) and re-extracted into dichloromethane. After successive clean-up by liquid-liquid partitioning, oxolinic acid was determined by HPLC with fluorimetric detection (exitation at 325 nm, emission at 360 nm). The analytical column was 3-microns MOS-Hypersil (150 x 4.6 mm I.D.) and the mobile phase contained (A) 0.025 M oxalic acid (pH 3.2)-acetonitrile-methanol-tetrahydrofuran (80:2.5:15:2.5, v/v) and (B) oxalic acid (pH 3.2)-acetonitrile-methanol-tetrahydrofuran (50:20:25:5), v/v) with the following elution profile: 0-5 min, linear gradient from 50 to 100% B; 5-10 min, isocratic at 100% B; 10.1-15 min, isocratic at 50% A-50% B. The calibration graph was linear over the concentration range studied (0.025-0.2 microgram/g). The limit of detection was 0.01 microgram/g (signal-to-noise ratio = 4).

Effect of cooking on residues of the quinolones oxolinic acid and flumequine in fish

The effect of cooking on residues of the quinolones oxolinic acid and flumequine in fish was investigated. Salmon containing residues of oxolinic acid and flumequine was boiled or baked in the oven. Samples of raw and cooked muscle, skin, and bone, as well as of the water in which the fish was boiled and juice from the baked fish, were analysed. Oxolinic acid and flumequine did not degrade at the temperatures reached when cooking the fish. However, fish muscle free from drug residues may be contaminated during boiling and baking due to leakage of the drug from reservoirs in the fish.

Extraction and analysis by high-performance liquid chromatography of antibiotics in a drug delivery system for farmed fish

Simple assays for extraction and determination of the concentrations of the antibiotics oxytetracycline, oxolinic acid, and flumequine in a drug dosage form for farmed fish are described. HPLC with UV detection was used in the analyses. The recovery of all three drugs was approximately 100%, and the precision varied from 0.5-3.0%. The methods are applicable to the production control, quality control, and stability control of the products.

Assay of oxolinic acid residues in salmon muscle by liquid chromatography with fluorescence detection: interlaboratory study

A previously developed method that uses a simplified sample preparation and fluorometric detection of liquid chromatographic eluates for the determination of oxolinic acid in salmon muscle has been collaboratively studied. Five laboratories participated in the study to analyze, in quintuplicate, blank salmon muscle fortified at 10, 20, 50, and 100 micrograms/kg (ppb), and 2 incurred samples from salmon given feed with medicated oxolinic acid. The tissue, 2 g mixed with 2 g Na2SO4, is extracted with ethyl acetate and centrifuged, and the solvent is evaporated. The residue is partitioned in a mixture of hexane and 0.01 M oxalic acid, and the aqueous phase is chromatographed using fluorescence detection at 327 nm excitation and 369 nm emission. Mean recoveries ranged from 77.2 to 84.5% in spiked samples with reproducibility relative standard deviation (RSDR) ranging from 11.5 to 18.3%. Treated salmon were found to contain 8.71 and 53.8 micrograms/kg with RSDR of 18.6 and 16.7%, respectively. The corresponding repeatability relative standard deviations (RSDR) were 5.8-12.2%, and 7.7 and 6.2%. The method is recommended for regulatory purposes in Canada.

Reservoir of quinolone residues in fish

Different tissues from salmon treated with the quinolones oxolinic acid, flumequine, enrofloxacin and sarafloxacin were analysed in search of possible reservoirs of the drugs. Residues of oxolinic acid and flumequine seem to be especially bound to bone, enrofloxacin to skin, and sarafloxacin to both skin and bone. The results showed that residues of these drugs were present in the fish for prolonged periods after the end of treatment.

Determination of oxolinic acid residues in salmon muscle tissue by liquid chromatography with fluorescence detection

The present paper describes a method for determination of oxolinic acid in salmon muscle tissue. Tissue (0.5-2 g) mixed with 2 g anhydrous sodium sulfate is extracted twice with ethyl acetate, centrifuged, and the extract evaporated. The residue is partitioned in a mixture of hexane and 0.01M oxalic acid and the aqueous phase chromatographed using fluorescence detection at 327 nm excitation and 369 nm emission. Calibration and standard curves are linear from 10-200 ppb and 100-2000 ppb at different sensitivity settings. Recoveries ranged from 71-83% in spiked blanks, with a CV of 4-10.3% over a 2-week period. Preliminary results in treated salmon were variable, possibly because some fish refused to eat medicated feed.

Gas chromatographic-mass spectrometric determination of oxolinic acid in fish using selected ion monitoring

A gas chromatographic-mass spectrometric (GC-MS) method is described for the determination of oxolinic acid in fish tissues. oxolinic acid is reduced with sodium tetrahydroborate to permit GC analysis. The sample is homogenized with phosphate buffer (pH 6) and extracted with ethyl acetate. The extract is partitioned between sodium hydrogencarbonate solution and the aqueous phase is acidified and re-extracted with ethyl acetate. The residue from the ethyl acetate extract is dissolved in methanol and reduced with sodium tetrahydroborate. The reduction product is extracted with diethyl ether and analysed by GC-MS in the selected ion monitoring mode for the ions at m/z 204, 219 and 176. The detection limit is 0.001 mg/kg and the recoveries were 95.6% [relative standard deviation (R.S.D.) 7.7%] at 0.1 mg/kg and 72.9% (R.S.D. 13.3%) at 0.01 mg/kg fortification levels in fish.

Automated column-switching high-performance liquid chromatographic determination of flumequine and oxolinic acid in extracts from fish

Two methods for automated analysis of extracts from edible muscle tissue of Atlantic salmon are described. Oxolinic acid and flumequine are extracted with phosphate buffer pH 9, and the extracts are analysed by high-performance liquid chromatography using a column-switching system. One method applies on-line concentration and clean-up of the extracts on a precolumn packed with polystyrene-divinylbenzene. This method was useful for the analysis of oxolinic acid and flumequine in the microgram/g range. The other method was based on on-line dialysis and concentration of the dialysate on the polymeric precolumn. This method was shown to be a reliable method for residue analysis, and the limit of detection was 2 ng/g for oxolinic acid and 3 ng/g for flumequine with fluorescence detection.

Analysis of oxolinic acid in fish by high-performance liquid chromatography

A simple high-performance liquid chromatographic method for assaying oxolinic acid, a chemotherapeutic agent, in fish tissues has been developed. Nalidixic acid is used as an internal standard. The drugs are separated on an internal surface reversed-phase column. The sample clean-up is minimized. Serum samples are analysed by direct injection on the column; muscle and liver samples are analysed after solid-phase extraction. The recoveries of oxolinic acid from spiked rainbow trout serum, muscle tissue and liver are 99.7, 87.7 and 83.6%, respectively. The lowest measurable amount of the drug is 0.01 microgram/g in all three tissues.

Improvement of chemical analysis of antibiotics. XVI. Simple and rapid determination of residual pyridonecarboxylic acid antibacterials in fish using a prepacked amino cartridge

A simple and rapid method for the determination of residual pyridonecarboxylic acid antibacterials (PCAs) (oxolinic acid, nalidixic acid and piromidic acid) in fish was developed using a combination of high-performance liquid chromatography (HPLC) and clean-up with an amino-type prepacked cartridge. PCAs were extracted with n-hexane-ethyl acetate (1:3) and the extract was applied to a Baker 10 amino cartridge. PCAs were eluted from the cartridge with acetonitrile-methanol-0.01 M aqueous oxalic acid solution (pH 3.0) (3:1:6) and were determined by HPLC. The separations were performed on Nucleosil 3C18 (3 microns, 75 x 4.6 mm I.D.) using a mobile phase containing oxalic acid. The recoveries of PCAs from various fishes fortified at the level of 1.0 ppm were 77.1-95.5%, and the detection limits were 0.05 ppm. The analytical time per sample was less than 30 min.

Evaluation of the release and efficacy of two new antibacterial agents from different ointment bases

The in vitro release of rosoxacin (1) and oxolinic acid (2) from three different ointment bases including a revised water washable (NF), an oleaginous, and an O/W emulsion ointment base was studied. Among the bases evaluated, the revised water washable base provided the best release of the two drugs as revealed from the values of the release rate constant (K). The amounts released of both drugs from the revised water washable base showed direct relationship with the concentration of the drug in the ointment. In addition, the effect of some additives on the amount released of both drugs from the different bases has been investigated. The release of 1 from the revised water washable base had been enhanced by adding 0.2% Tween 80 or 10% ethanol, but addition of 10% of N,N-dimethylacetamide and polyvinylpyrrolidone (PVP) led to retardation of the release of the drug. Furthermore addition of 10% polyethylene glycol (PEG) 200, N,N-dimethylacetamide, or ethanol led to enhancement of the release of the drug from both the oleaginous and the emulsion bases. On the other hand, the release of 2 from the revised water washable base had been enhanced only on addition of 0.2% Tween 80 and been retarded by adding 10% ethanol, N,N-dimethylacetamide or PVP to the formula. The release of 2 from the oleaginous, as well as the emulsion bases had been enhanced by 10% PEG 200. However urea was found to show no pronounced effect on the release of the two drugs from the different ointment bases.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous determination of nalidixic acid, oxolinic acid and piromidic acid in fish by high-performance liquid chromatography with fluorescence and UV detection

A simple and rapid method for the simultaneous determination of nalidixic acid (NA), oxolinic acid (OXA) and piromidic acid (PMA) in cultured fish has been developed by high-performance liquid chromatography (HPLC). The drugs were extracted with 0.1% metaphosphoric acid-methanol (6:4), followed by a Sep-Pak C18 clean-up procedure. The HPLC separation was carried out on a Kaseisorb LC ODS 300-5 column (25 cm x 4.6 mm I.D.) using 5 mM phosphate buffer-acetonitrile (6:4) as a mobile phase. A fluorescence detector was used for NA and OXA at the excitation wavelength of 325 nm and the emission wavelength of 365 nm and an ultraviolet detector at 280 nm for PMA. The calibration graphs were rectilinear from 1 to 10 ng for OXA, from 2 to 20 ng for NA and PMA. The recoveries of NA, OXA and PMA added to fish were 81.5-85.3, 83.7-88.7 and 80.9-84.9%, respectively, with high accuracy. The limits of detection were 0.01 micrograms/g for each drug.

[UV-spectrophotometry in drug control. 33. New drugs with benzene, pyridine, quinoline and phenanthrene chromophores in the molecule. 6. The effect of substitution and solvents]

UV-spectra of 14 new substances with benzene, pyridine, quinoline and phenanthrene chromophores as well as influences of substitutes and solvents on shifts of the bands E, K, B and R are discussed.

[Chemotherapy on the biliary tract infections. XIII. Miloxacin, a novel chemotherapeutic agent, its excretion into bile and clinical effect on the biliary tract infections (author's transl)]

Miloxacin, a novel chemotherapeutic agent, has been reported to have very potent antibacterial activity to E. coli, Klebsiella, Proteus and other Gram-negative rods and be excreted into bile at high levels. Therefore, the effectiveness of miloxacin against biliary tract infections and its excretion into bile in patients were investigated. The results were as follows: i) Comparative studies on the excretion of miloxacin, nalidixic acid (NA) and cephalexin (CEX) into bile of patients operated in gallbladder were performed by a crossover method. The maximum concentration of miloxacin after oral administration of 500 mg ranged from 18.2 to 24.0 micrograms/ml and were much higher than those of NA (5.3 micrograms/ml) and CEX (3.4 micrograms/ml). The mean recovery of miloxacin within 6 hours was 0.256% and much greater than those of NA (0.075%) and CEX (0.027%). ii) Into bile, intact miloxacin and its metabolites (the glucuronides of miloxacin and M-2) were excreted but M-1 was scarcely excreted. Regression analysis of the concentrations by the bioassay compared with those intact miloxacin by the HPLC method gave a good correlation with r = 0.96. iii) The clinical effectiveness against the biliary tract infections was investigated in 29 cases. Miloxacin showed the excellent effect in 8 cases and the good effect in 17 cases, giving an effective ratio of 86.2%. Especially, all of the cases dosed with miloxacin over 34 mg/kg in a day showed excellent or good results. iv) The rates of clinical effectiveness were 85.7, 80.0% and 71.4% in E. coli, Klebsiella and Proteus infections, respectively. The antibacterial activity of miloxacin against 27 strains isolated in this test was more potent than those of NA and CEX. v) During the clinical tests, none of any side effect with miloxacin was observed in both of subjective and objective symptoms. These results show that miloxacin is expected to be fully applicable on the therapy of biliary tract infections.

Determination of miloxacin and metabolites in human serum and urine by high-pressure liquid chromatography

A sensitive and reliable high-pressure liquid chromatography (HPLC) assay for miloxacin and its two principal metabolites, 5,8-dihydro-8-oxo-2H-1,3-dioxolo[4,5-g]quinoline-7-carboxylic acid (M-1) and 1,4-dihydro-1,6-dimethoxy-7-hydroxy-4-oxoquinoline-3-carboxylic acid (M-2), in human serum and urine was developed. A strong anion-exchange Zipax SAX column using a mobile phase of 0.01 M citric acid solution containing 0.03 M sodium nitrate with pH 5.0 was used to achieve separation of the three compounds. The retention times of miloxacin, M-1, and M-2 were 3.8, 9.3, and 5.9 min, respectively. Serum and urine concentrations of these compounds as low as 10 ng/ml were measured. When results from the HPLC assay were compared with those from the microbiological assay of serum and urine samples from human subjects receiving miloxacin orally, the correlation coefficients were 0.94 for the serum and 0.99 for the urine. The HPLC assay method presents an alternative to the microbiological assay and permits future pharmacokinetic investigations of miloxacin.

In vitro susceptibility comparisons and recommendations for oxolinic acid

Minimal inhibitory concentration and disk diffusion susceptibility studies were carried out with oxolinic acid to determine a recommended disk content for disk susceptibility testing. Regression curve analyses were performed with disks containing 1, 2, and 5 mug of oxolinic acid. Data suggest that the 5-mug disk more satisfactorily fulfills requirements for susceptibility testing than the 1- or 2-mug disks evaluated. Ultraviolet spectral analysis studies for absorption maxima and extinction coefficients were done to verify the authenticity and concentration of oxolinic acid in the aqueous solutions studied.