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At least 19 recordsLinked to original sources
PubMedDate not supplied

Determination of clopidol residues in chicken tissues by liquid chromatography: part II. Distribution and depletion of clopidol in chicken tissues.

A study was made of the distribution and depletion of clopidol residues at different tissue locations in chickens fed with feeds incurred with clopidol. Experiments showed that the residue levels were not identical at 5 different tissue locations in each chicken. The sequence of residue levels from high to low was livers, kidneys, upper breast, lower breast, and leg meat. The maximum residue values after suspension of the drug for 8 h were (mg/kg): livers, 4.600; kidneys, 3.619; upper breast, 1.742; lower breast, 1.641; leg meat, 1.525. The averages were taken after values for 10 chickens were determined. After suspension of the drug for 3 days, >80% residue clopidol was depleted, and the depletion was nearly completed within 7 days. The speed of depletion varied at different tissue locations in each chicken, with the sequence from fast to slow being equivalent to that of the residue levels. Analytical results of 350 samples during 7 days showed that the proposed method is specific for determination of clopidol in chickens.

Animals↗
PubMed1984

Effects of decoquinate and clopidol on electron transport in mitochondria of Eimeria tenella (Apicomplexa: Coccidia).

Resistance of the chicken coccidium Eimeria tenella to the anticoccidial agents decoquinate and clopidol, and the synergistic activity of mixtures of these compounds have been confirmed in vivo. Inhibition of electron transport by decoquinate and clopidol has been studied in mitochondria isolated from unsporulated oocysts of the same lines of E. tenella as those used in the in vivo studies. Electron transport in mitochondria of a drug sensitive line was susceptible to inhibition by both decoquinate and clopidol, and mitochondria isolated from lines made resistant to one or the other of these compounds showed a corresponding resistance at the level of electron transport. Combinations of low concentrations of decoquinate and clopidol caused a greater inhibition of electron transport than expected from summation of their individual actions. Isobolograms showed that decoquinate and clopidol in fact potentiated each other's effect on electron transport. Induced resistance to either decoquinate or clopidol resulted in an increased sensitivity of electron transport to inhibition by the other drug. Cytochrome spectra of E. tenella mitochondria and a biphasic response of NADH-oxidase and terminal oxidase activity to inhibition by cyanide or azide suggest the presence of two functional terminal oxidases. There is a correlation between the resistance of electron transport to inhibition by decoquinate or clopidol and the susceptibility to inhibition by cyanide or azide. Mitochondrial electron transport that is more resistant to inhibition by decoquinate exhibits greater sensitivity to cyanide and azide; electron transport that is more resistant to inhibition by clopidol exhibits a decreased sensitivity to cyanide and azide. Resistance to decoquinate and clopidol is discussed in view of a possibly branched electron transport chain in mitochondria of E. tenella.

Animals↗
PubMedDate not supplied

Tissue residues of clopidol (3,5-dichloro-2,6-dimethyl-4-pyridinol) in chickens in relation to withdrawal times.

Broiler chickens were fed on a commercial diet containing 0.0125% clopidol for 34 days. They were killed 0-10 days after withdrawal of the premedicated feed and clopidol was determined in liver and muscle samples by a sensitive gas-liquid chromatography (g.l.c.) method. During the first two post-withdrawal days the clopidol concentration in the liver decreased rapidly from 7 to 0.5 mg/kg and the level in muscle declined from 3 to 0.1 mg/kg. There was little decline in the clopidol concentrations from days 2 to 10, the levels during this period being 0.2-0.8 mg/kg in liver and 0.05-0.2 mg/kg in muscle. In addition to the above experimental study, liver and muscle samples collected at a Swedish slaughterhouse from broiler chickens raised on clopidol-containing feed were analysed for residues of this drug. Large variations were found in the clopidol levels in broilers from different producers. The levels in the liver ranged from 0.05 to 8.0 mg/kg and those in muscle from 0.03 to 3.5 mg/kg. The present results emphasize the need to carry out field studies to check the levels of feed additive residues in edible tissues from chickens.

Animal Feed↗
PubMed1978

Eimeria tenella: experimental studies on the development of resistance to amprolium, clopidol and methyl benzoquate.

The development of resistance by the Houghton strain of Eimeria tenella to the anticoccidial drugs amprolium, clopidol and methyl benzoquate has been studied. Resistance to amprolium and clopidol developed more readily in experiments where a large number of coccidia were exposed to the drug, either by increasing the number of oocysts in the inoculum or by increasing the number of birds in the group. When 45 birds were given 2.0 X 10(6) oocysts, resistance to amprolium and clopidol appeared after 6 and 7 passages respectively. In previous experiments, under similar conditions, resistance to robenidine developed after 6 passages, suggesting little difference between these three drugs. Resistance to amprolium and clopidol arose gradually as the concentration of drug was increased, but resistance to methyl benzoquate appeared in a single step from sensitivity to high-level resistance. Both amprolium and clopidol-resistant lines showed an 8-fold reduction in drug sensitivity. Attempts to measure the degree of resistance by calculation of the ED50 were unsuccessful.

Amprolium↗
PubMedDate not supplied

Gas chromatographic determination of clopidol in chicken tissues.

A method has been developed for the determination of clopidol residues in chicken tissues. After extraction and cleanup, clopidol is esterified in a 2-phase system to clopidol propionate, which is determined by gas chromatography. The 2-phase system includes, in addition to the clopidol dissolved in methanol, aqueous borax solution, hexane, propionic anhydride, and pyridine. Use of these reagents precludes the use of explosive or carcinogenic chemicals in the derivatization step, and the method is therefore suitable for routine laboratory analysis. Levels of 0.5 ppb clopidol in tissue can be determined.

Animals↗
PubMedDate not supplied

Rapid liquid chromatographic determination of clopidol in chicken muscles.

A simple, rapid, and sensitive liquid chromatographic method is described for the quantitative determination of trace amounts of clopidol (3,5-dichloro-2,6-dimethyl-4-pyridinol) in chicken muscles. Clopidol was extracted from tissues with acetonitrile and the extract was cleaned up on an alumina column and separated on an anion exchange column, using 0.5% acetic acid in methanol as eluant. The solvent in the eluate was evaporated and the residue was dissolved in methanol containing benzamide as internal standard. Clopidol was separated on a Zorbax ODS column (4.6 X 250 mm) by using acetonitrile-0. 05M phosphate buffer, pH 7.0 (15 + 85 v/v%), and detected at 270 nm with 0.005 AUFS . Recoveries of clopidol added to chicken tissues at levels of 0.02, 0.05, and 0.1 microgram/g were 94.8, 94.8, and 97.0%, respectively. This method is applicable to levels as low as 0.01 ppm clopidol in chicken muscle.

Animal Feed↗
PubMed1978

The activity of methyl benzoquate and clopidol against Eimeria maxima: synergy and drug resistance.

Synergy between clopidol and methyl benzoquate against Eimeria maxima was shown to be supra-additive. Collateral sensitivity to these drugs could not be demonstrated in resistant lines of this parasite. Resistance to methyl benzoquate and clopidol was not transferred when lines of E. maxima, resistant to the respective drugs, were propagated together. The failure to demonstrate this phenomenon was judged not to be due to synergy between the drugs. Attempts to induce simultaneous was readily acquired by a line of E. maxima resistant to clopidol. Induced resistance to clopidol in a methyl benzoquate-resistant line required numerous passages.

Animals↗
PubMedDate not supplied

Determination of clopidol residues in chicken tissues by liquid chromatography: collaborative study.

Eighteen laboratories participated in a collaborative study on the determination of clopidol residues in chicken muscle tissues by liquid chromatography. Of these, results from 16 laboratories which rigorously followed the method were subjected to statistical analysis. The method performance was assessed by all participants using 14 samples of chicken muscle fortified at concentrations ranging from 0.1 to 5.0 mg/kg. In addition, 9 participants each reported results for 6 clopidol-incurred samples in chicken muscle. Test portions were extracted with acetonitrile, and the extracts were purified with alumina and anion exchange resin solid-phase extraction cartridges in sequence. Clopidol was separated by reversed-phase liquid chromatography and quantified at 270 nm. Average recoveries ranged from 81.8 to 85.4%, reproducibility relative standard deviation (RSDR) ranged from 11.9 to 22.6%, and repeatability relative standard deviation (RSDr) ranged from 9.9 to 15.1%. For clopidol-incurred samples at concentrations of 0.100-0.687 mg/kg, the mean determination value range was 0.099-0.659 mg/kg; RSDR was 12.6-19.8%, RSDr was 3.1-8.5%; and HORRAT values were 0.7-1.1. The accuracy and precision of the method are in conformity with the requirements specified by AOAC INTERNATIONAL. The method was adopted Official First Action in April 2003.

Animals↗
PubMed1980

Improved method for gas-liquid chromatographic determination of clopidol in chicken tissues.

A sensitive and specific gas-liquid chromatographic (GLC) method has been developed for determining low levels of clopidol in chicken tissues. Clopidol is extracted from the tissues with methanol, and cleaned up on an alumina column and an anion exchange resin column with 0.1% acetic acid--methanol as eluate. Clopidol is methylated with diazomethane, and then determined by GLC. 2,4-Dinitro-1-chlorobenzene is used as an internal standard. The method is applicable to levels as low as 2 ppb in chicken tissues. Recoveries of 2--20 ppb clopidol added to tissues averaged 87% for muscle, 84% for liver, 80% for kidney, and 76% for fat.

Animals↗
PubMed1991

Effects of clopidol on sporulation and infectivity of Eimeria tenella oocysts.

Feed additive anticoccidials currently used in Japan were examined for possible effects on oocyst sporulation of Eimeria tenella. Monensin, salinomycin, lasalocid, amprolium plus ethpabate, amporolium plus ethopabate plus sulfaquinoxaline, clopidol, or nicarbazin were given to chickens continuously via the feed at the recommended use level or one-half of that level. Oocysts discharged in feces 7-8 days post inoculation (PI) were collected and aerated for sporulation. Low sporulation rate was noted, when clopidol at 62.5 mg kg-1 was given from 4 to 7 days PI. These oocysts were as infective as oocysts from controls, based on weight gain, feed efficiency, gross lesion score of cecae, and oocyst count 7 days PI. The results of the study indicated that the second schizogony and gametogony are vulnerable to clopidol, as evidenced by oocyst sporulation, but infectivity of these sporulated oocysts was not affected.

Animals↗
PubMed2000

Determination of clopidol residues in chicken tissues by high-performance liquid chromatography-mass spectrometry.

A high-performance liquid chromatographic-mass spectrometric (HPLC-MS) method has been developed for determination of clopidol residues in chicken tissues. Samples are extracted with acetonitrile. The extracts are cleaned up on an alumina column followed by an anion-exchange column. The clopidol is separated on a column (150 cmx4.6 mm) of Intertsil by using acetonitrile-water (20:80) as mobile phase. The clopidol was qualitatively identified by molecule mass and determined quantitatively by selected ion monitoring mode at 190 m/z. The recoveries with RSDs ranged from 91.6+/-10.1 to 97.3+/-5.7 at 0.010 to 10.0 mg/kg by spiking three matrices (chicken muscle, liver, and kidney). The limit of detection was 0.005 mg/kg, and the limit of quantification was 0.010 mg/kg.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Determination of clopidol residues in chicken tissues by liquid chromatography: part III. Quality control analysis of export chickens.

A summary is presented of the liquid chromatographic (LC) determination of clopidol residues in export chickens from 1992 to 1999. Over the past 8 years, we analyzed >7000 chicken samples. A total of 0.66% of samples contained clopidol residues, ranging from 0.005 to 0.79 mg/kg; however, none exceeded 3 mg/kg, the Chinese maximum residue limit. In comparison with 1992, the number of samples multiplied 70-fold, and the frequency of clopidol found in samples decreased 148-fold in 1999. The chickens inspected were exported to foreign countries; all were cleared by the buyers with no disputes. This report also introduces the critical control points of the proposed LC method as well as identification of false-positive procedures by both experience and LC/mass spectrometric confirmation. Our experiences over the past 8 years have demonstrated that the ruggedness of the proposed LC method is quite good.

Animals↗
PubMedDate not supplied

Determination of residual clopidol in chicken muscle by capillary gas chromatography/mass spectrometry.

Clopidol was extracted from chicken with acetonitrile, and the extract was evaporated to about 5 mL. The concentrated solution was centrifuged and applied to a glass column filled with basic alumina. The column was eluted with methanol and the methanol was evaporated to dryness. The residue was derivatized with Sylon BFT and analyzed by gas chromatography/mass spectrometry (GC/MS). Mass characteristics of trimethylsilyl derivative of clopidol were interpreted manually. The selected-ion monitoring mode was performed at m/z 191, 248, 263, and 265. A sensitive, reproducible GC/MS method was developed for monitoring residues of clopidol in chickens. All recoveries of the drug from chicken muscle fortified at 1, 10, and 100 ng/g were > 65%, and relative standard deviations were < 15%. The detection limit was about 0.5 ng/g, and the quantitation limit was the lower limit of the standard curve, which was about 1 ng/g.

Aluminum Oxide↗
PubMed1975

Lerbek, a synergistic mixture of methyl benzoquate and clopidol for the prevention of chicken coccidiosis.

Methyl benzoquate at 20 ppm or clopidol at 250 ppm in the diet show true coccidiostatic activity in infections with Eimeria tenella in the chick. Lerbek, a synergistic mixture yielding 8-35 ppm methyl benzoquate and 100 ppm clopidol, produced a partially coccidiocidal effect; relapses following restricted periods of medication were less severe, and suppression of parasite development following delayed medication was quicker and more effective with either component of the mixture used alone.

Animals↗
PubMedDate not supplied

Determination of clopidol residues in chicken tissues by liquid chromatography: part I. Optimization of analytical conditions and comparison with AOAC gas chromatography method.

A simple and specific liquid chromatographic method was developed for determination of clopidol in chicken tissues. Samples were extracted with acetonitrile. The extracts were cleaned up on an alumina column and an anion exchange column. The clopidol was separated on a column (30 cm x 3.9 mm) of microBondapak C18 (10 microm) by using acetonitrile-water (20 + 80, v/v) as mobile phase, and determined quantitatively at 270 nm. Recoveries were 86.0-97.6%, with relative standard deviations of 2.14-9.42% at 0.010-2.0 mg/kg from 4 spiked matrixes of chicken muscle, egg, liver, and kidney. The limit of detection was 0.005 mg/kg. Compared with the modified AOAC gas chromatographic method, the present method is simple and fast to operate. Its results are accurate and reliable, making it favorable for environmental protection and meeting requirements for human safety. Thus, it is suitable for routine analysis of large quantities of samples.

Animals↗
PubMed2000

Determination of nicarbazin and clopidol in poultry feeds by liquid chromatography.

A rapid and very effective analytical procedure for the simultaneous liquid chromatographic determination of two coccidiostats, clopidol (CLOP) and nicarbazin (NICA), in poultry feeds was developed and tested. The ground feed samples were extracted using aqueous dimethylformamide after moistening with water. Co-extracted feed constituents were removed with a solid-phase extraction alumina-basic column and the eluates were directly analyzed on an ODS column (250x4.6 mm, 5 microm) with acetonitrile-0.01 M acetate buffer (pH 4.6) as eluent. UV detection of CLOP and the 4,4'-dinitrocarbanilide portion of NICA was carried out at 265 and 345 nm, respectively. The mean recovery from NICA spiked samples was 95% with a RSD of 4% in a concentration range of 2-150 mg/kg while for CLOP it was 98% with a RSD of 5% in a concentration range of 5-150 mg/kg. The limits of detection of NICA and CLOP in feed, based on a detector signal-to-noise ratio of 3, were estimated to be 1 mg/kg and 2.5 mg/kg, respectively, and the lowest levels tested in feeds by this procedure were 2 mg/kg and 5 mg/kg, respectively.

Animal Feed↗
PubMed1976

Model ecosystem evaluation of the environmental impacts of the veterinary drugs phenothiazine, sulfamethazine, clopidol, and diethylstilbestrol.

Four veterinary drugs of dissimilar chemical structures were evaluated for environmental stability and penchant for bioaccumulation. The techniques used were (1) a model aquatic ecosystem (3 days) and (2) a model feedlot ecosystem (33 days) in which the drugs were introduced via the excreta of chicks or mice. The model feedlot ecosystem was supported by metabolism cage studies to determine the amount and the form of the drug excreted by the chicks or mice. Considerable quantities of all the drugs were excreted intact or as environmentally short-lived conjugates. Diethylstilbestrol (DES) and Clopidol were the most persistent molecules, but only DES bioaccumulated to any appreciable degree. Phenothiazine was very biodegradable; sulfamethazine was relatively biodegradable and only accumulated in the organisms to very low levels. Data from the aquatic model ecosystem demonstrated a good correlation between the partition coefficients of the drugs and their accumulation in the fish.

Animals↗