Effect of long-term dietary administration of oregano on the alleviation of carbon tetrachloride-induced oxidative stress in rats.

This study aimed at evaluating the protective effect of long-term dietary oregano on the alleviation of carbon tetrachloride-induced oxidative stress in rats. Twenty-four female Wistar rats were allocated to four groups of six animals each. Groups 1 (control) and 2 (CCl 4) were fed a basal diet, while groups 3 (oregano) and 4 (oregano + CCl 4) were fed the basal diet supplemented further with ground oregano at 1% level. Following six-week feeding, the rats of groups 2 and 4 were given a single intraperitoneal injection of CCl 4 at a dose of 1 mL/kg bw. Six hours after the CCl 4 injection, all animals were sacrificed, and serum, liver, kidney, and heart tissue samples were collected. Analysis results showed that the addition of oregano significantly increased the total phenolic content and the Trolox equivalent antioxidant capacity of the basal diet but had no effect on its lipid peroxidation index. Treatment with CCl 4 of rats from the CCl 4 group caused a significant increase in aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP) in serum, whereas it decreased cholesterol and triglyceride content as compared to the control. It also increased the lipid peroxidation index and decreased the scavenging activities of the 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS) radical cation, the hydroxyl anion radical, the superoxide anion radical, and the hydrogen peroxide in all tested tissues, as compared to that of the control. Without CCl 4 treatment, diet supplementation with oregano had no effect on these biochemical parameters, excluding the hydroxyl radical scavenging activity, which was increased in all tested tissues as compared to that of the control. Feeding oregano before CCl 4 treatment resulted in a significant decline of the increase in AST, ALT, and ALP activities ( P < 0.05 vs CCl 4 group), but the recorded values could not attain those of the control group ( P < 0.05 vs control group). It significantly increased the reduced cholesterol and triglycerides ( P < 0.05 vs CCl 4 group) to values not differing from those of the control. It also resulted in a significant reduction of the increased malondialdehyde ( P < 0.05 vs CCl 4 group) to values that could not attain the levels of the control but had no significant effect ( P > 0.05) on the reduced ABTS radical cation scavenging activity. It increased significantly the reduced hydroxyl anion radical scavenging activity ( P < 0.05 vs CCl 4 group) to values that could not attain those of the control in all tested tissues except kidney. Additionally, it resulted in a significant elevation of the decreased superoxide anion radical scavenging activity in serum and liver but had no effect in kidney and heart, whereas it also resulted in a significant elevation of the decreased hydrogen peroxide scavenging activity in liver, kidney, and heart but had no effect in serum. These results suggest that dietary oregano may effectively improve the impaired antioxidant status in CCl 4-induced toxicity in rats.

The incorporation of dehydrated rosemary leaves in the rations of turkeys and their impact on the oxidative stability of the produced raw and cooked meat.

Thirty-six 12-week-old turkeys were distributed into six groups and were raised for 4 weeks on rations containing 0%, 0.5% or 1.0% dehydrated rosemary leaves as antioxidant in the presence of alpha-tocopheryl acetate from 10 to 300 mg/kg. Following slaughtering, breast and thigh meat samples, raw or cooked, from all six groups were collected to be refrigerated at 4 degrees C for 9 days. All stored samples were submitted to analysis for their concentration in malondialdehyde (MDA), a lipid oxidation marker, and alpha-tocopherol. The results showed that the rations containing 300 mg/kg alpha-tocopheryl acetate increased the mean alpha-tocopherol content of the breast and thigh significantly (P <0.05) compared with the respective control values. No significant (P>0.05) changes could be observed in the alpha-tocopherol content of breast and thigh of turkeys consuming rations containing up to 1% dehydrated rosemary leaves. The refrigeration of the meats led to spontaneous increase in the MDA content of the breast and thigh meat samples. Samples from turkeys fed rations containing 300 mg/kg alpha-tocopheryl acetate showed the lowest mean levels of MDA after the 9-day refrigerated period. The incorporation of rosemary in the rations led to a modest decrease in the formation of MDA in the meats compared with the respective mean control values. The combination of alpha-tocopheryl acetate and rosemary was not associated with an additional decrease in MDA formation.

Effect of dietary saffron (Crocus sativus L.) on the oxidative stability of egg yolk.

1. The effects of dietary inclusion of red stigmas of Greek saffron (Crocus sativus L.) on the oxidative stability of shell eggs and liquid yolks were investigated and compared with those of dietary a-tocopherol. 2. Ninety-six Lohmann laying hens, 38 weeks old, distributed into 4 groups with 4 replicates each, were given either a control diet, diets enriched with 10 (SAF10) or 20 (SAF20) mg/kg saffron, or a diet enriched with 200 mg/kg a-tocopheryl acetate (VE200). 3. Following 6 weeks of feeding, eggs were collected and the rate of lipid oxidation was determined in refrigerated stored shell eggs, as well as in yolks adjusted to a pH of 6.2 or 4.2 and stored in the presence of light. 4. The results showed that the extent of lipid oxidation in shell eggs, as measured by malondialdehyde (MDA) formation, differed between dietary treatments, but did not change with storage time. In stored shell eggs, MDA levels differed between dietary treatments at all time points. 5. Yolks from the control group adjusted to pH 6.2 gave MDA values higher than those of the SAF10 group, which in turn were higher than those of the SAF20 group, a finding suggesting that saffron exerted a dose-dependent antioxidative activity. The VE200 group gave lower MDA values than the other groups at all time points. The oxidation profile of yolks at pH 4.2 showed a similar pattern but the rate of oxidation was greater.

Performance of rabbits and oxidative stability of muscle tissues as affected by dietary supplementation with oregano essential oil.

The effect of dietary supplementation with oregano essential oil on the performance of rabbits, and the susceptibility of the produced raw and thermally treated muscle tissue to lipid oxidation during refrigerated storage, were investigated. A total of 96 weaned rabbits were separated into four equal groups with three subgroups each. One group was given the basal diet and served as control, two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, whereas the remaining group was given a diet supplemented with alpha-tocopheryl acetate at 200 mg/kg. During the 42-day experimental period, body weight and feed intake were recorded weekly and the feed conversion ratio was calculated. Feeding the experimental diets to rabbits, performance parameters were not affected. Therefore, dietary oregano essential oil exerted no growth-promoting effect on rabbits. With increased supplementation of oregano essential oil, malondialdehyde values decreased in both raw and thermally treated muscles during refrigerated storage. This finding suggests that dietary oregano essential oil exerted a significant antioxidant effect. Dietary supplementation of oregano essential oil at the level of 200 mg/kg was more effective in delaying lipid oxidation compared with the level of 100 mg/kg, but inferior to dietary supplementation of 200 mg alpha-tocopheryl acetate per kg. This study indirectly provides evidence that antioxidant compounds occurring in oregano essential oil were absorbed by the rabbit and increased the antioxidative capacity of tissues.

Blockade of Kupffer cells by gadolinium chloride reduces lipid peroxidation and protects liver from ischemia/reperfusion injury.

BACKGROUND/AIMS: The implication of lipid peroxidation in the inhibitory effect of GdCl3 (gadolinium chloride) on Kupffer cells activation has not been extensively investigated. The aim of this study was to examine the effect of GdCl3 inhibition of Kupffer cells activation on lipid peroxidation after severe total hepatic ischemia/reperfusion. METHODOLOGY: Male Wistar rats (n = 40) were randomly divided into a sham-operation group, a control ischemia/reperfusion group, and two ischemia/reperfusion groups pretreated with GdCl3 (10 mg and 20 mg/kg bw intravenously, 48 and 24 h prior to operation). Following 60 min of total hepatic ischemia and 120 min of reperfusion, the rats were sacrificed, and liver samples were taken for determination of malondialdehyde and light microscopy examination. Blood samples were also taken for assay of aspartate and alanine transaminase. Additional animals (n = 60) were followed up for a 7-day survival rate determination. RESULTS: Ischemia/reperfusion decreased the survival rate to 13.3%, increased (p < 0.001) the levels of aspartate and alanine transaminase in serum to 2387 +/- 75 and 2157 +/- 87 IU/L, respectively, and increased (p < 0.001) malondialdehyde levels in liver to 1.609 +/- 0.096 nmoles/g compared with 1.164 +/- 0.060 in the sham operation group. Pretreatment with GdCl3 increased the survival rate to 60%, and decreased (p < 0.001) the levels of aspartate transaminase in serum to 1549 +/- 66 and 1496 +/- 55 IU/L, the levels of alanine transaminase in serum to 1302 +/- 48 and 1305 +/- 63 IU/L, and the levels of malondialdehyde in liver to 1.132 +/- 0.034 and 1.149 +/- 0.57 nmoles/g for the lower and the higher doses of GdCl3, respectively. Histological examination showed protection of liver parenchyma in the animals treated with GdCl3. CONCLUSIONS: Experimental data suggest that GdCl3 inhibition of Kupffer cells activation protects liver from ischemia/reperfusion injury by a mechanism that reduces lipid peroxidation.

Effect of dietary supplementation with oregano essential oil on performance of broilers after experimental infection with Eimeria tenella.

A study was carried out to examine the effect of dietary supplementation of oregano essential oil on performance of broiler chickens experimentally infected with Eimeria tenella at 14 days of age. A total of 120 day-old Cobb-500 chicks separated into 4 equal groups with three replicates each, were used in this study. Two groups, one infected with 5 x 10(4) sporulated oocysts of E. tenella and the other not, were given a basal diet and served as controls. The other two groups also infected with E. tenella were administered diets supplemented with oregano essential oil at a level of 300 mg/kg, or with the anticoccidial lasalocid at 75 mg/kg. Following this infection, survival rate, bloody diarrhoea and oocysts excretion as well as lesion score were determined. Throughout the experimental period of 42 days, body weight gain and feed intake were recorded weekly, and feed conversion ratios were calculated. Two weeks after the infection with E. tenella supplementation with dietary oregano oil resulted in body weight gains and feed conversion ratios not differing from the non-infected group, but higher than those of the infected control group and lower than those of the lasalocid group. These parameters correspond with the extent of bloody diarrhoea, survival rate, lesion score and oocyst numbers and indicated that oregano essential oil exerted an anticoccidial effect against E. tenella, which was, however, lower than that exhibited by lasalocid.

The effects of dietary oregano essential oil and α-tocopheryl acetate on lipid oxidation in raw and cooked turkey during refrigerated storage.

The effects of dietary oregano essential oil and α-tocopheryl acetate supplementation on the susceptibility of raw and cooked turkey breast and thigh meat to lipid oxidation during refrigerated storage for 9 days were examined. Thirty 12-week-old turkeys were divided into five groups and fed a basal diet containing 30 mg α-tocopheryl acetate kg(-1) feed as control, or basal diet plus 200 mg α-tocopheryl acetate kg(-1), or basal diet plus 100 mg oregano oil kg(-1), or basal diet plus 200 mg oregano oil kg(-1), or basal diet plus 100 mg oregano oil and 100 mg α-tocopheryl acetate kg(-1), for 4 weeks prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde formation in raw and cooked meat at 0, 3, 6 and 9 days of refrigerated storage, through use of a third-order derivative spectrophotometric method. Results showed that all dietary treatments significantly (P<0.05) increased the stability of both raw and cooked turkey meat to lipid oxidation compared with the control. Oregano oil at 200 mg kg(-1) was significantly (P<0.05) more effective in delaying lipid oxidation compared to the level of 100 mg kg(-1), equivalent to α-tocopheryl acetate at 200 mg kg(-1), but inferior (P<0.05) to oregano oil plus α-tocopheryl acetate at 100 mg kg(-1) each, which in turn was superior (P<0.05) to all dietary treatments, indicating a synergistic effect. Thigh muscle was more susceptible to oxidation compared with breast muscle in all treatments, although it contained α-tocopherol at significantly (P<0.05) higher levels.

Distribution and stability of aflatoxin M1 during production and storage of yoghurt.

Yoghurt from cow's milk artificially contaminated with aflatoxin M1 (AFM1) at levels of 0.050 and 0.100 g l(-1) was fermented to reach pHs 4.0 and 4.6. Yoghurt fermented to pH 4.6 was also used for preparing strained yoghurt. Yoghurts were stored at 4 degrees C for up to 4 weeks. Analysis of AFM1 in milk, yoghurt, strained yoghurt and yoghurt whey was carried out using immunoaffinity column extraction and liquid chromatography coupled with fluorometric detection. AFM1 levels in yoghurt samples showed a significant decrease (p < 0.01) compared with those initially added to milk. Growth of culture lactic acid bacteria was not affected in the AFM1 contaminated yoghurts, with the exception of Streptococcus thermophilus that showed a significantly (p < 0.01) lower increase in the yoghurt containing the toxin at high concentration. Following fermentation, AFM1 was significantly lower (p < 0.01) in yoghurts with pH 4.0 than in yoghurts with pH 4.6 at both contamination levels. During refrigerated storage, AFM1 was rather more stable in yoghurts with pH 4.6 than with pH 4.0. The percentage loss of the initial amount of AFM1 in milk was estimated at about 13 and 22% by the end of the fermentation, and 16 and 34% by the end of storage for yoghurts with pHs 4.6 and 4.0, respectively. The percentage distribution ratio of AFM1 in strained yoghurt/yoghurt whey of the initial toxin present in the yoghurt was about 90/10 and 87/13 for the lower and the higher contamination levels, respectively.

Occurrence of aflatoxin M(1) in raw and market milk commercialized in Greece.

From December 1999 to May 2000, 114 samples of pasteurized, ultrahigh temperature-treated (UHT) and concentrated milk were collected in supermarkets, whereas 52 raw milk samples from cow, sheep and goat were obtained from different milk producers all over Greece. Sample collection was repeated from December 2000 to May 2001 and concerned 54 samples of pasteurized milk, 23 samples of bulk-tank raw milk and 55 raw milk samples from cow, sheep and goat. The total number of samples analysed for aflatoxin M(1) (AFM(1)) contamination by immunoaffinity column extraction and liquid chromatography was 297. In the first sampling, the incidence rates of AFM(1) contamination in pasteurized, UHT, concentrated and cow, sheep and goat raw milk were 85.4, 82.3, 93.3, 73.3, 66.7 and 40%, respectively, with only one cow raw milk and two concentrated milk samples exceeding the EU limit of 50 ng l(-1). In the second sampling, the incidence rates of AFM(1) contamination in pasteurized, bulk-tank and cow, sheep and goat raw milk were 79.6, 78.3, 64.3, 73.3 and 66.7%, respectively, with only one cow and one sheep raw milk samples exceeding the limit of 50 ng l(-1). The results suggest that the current regulatory status in Greece is effective.

Effect of dietary oregano essential oil on performance of chickens and on iron-induced lipid oxidation of breast, thigh and abdominal fat tissues.

1. We studied the effect of dietary oregano essential oil (50 and 100 mg/kg of feed) on the performance of broilers, and determined the susceptibility of the resulting broiler meat to iron-induced lipid oxidation. 2. Performance of the birds was unaffected by the experimental diets. Therefore, dietary oregano oil exerted no growth-promoting effect on broilers. 3. Iron-induced lipid oxidation showed that as oregano oil increased in the diet, malondialdehyde values decreased in tissue samples, suggesting that the oil, particularly at 100 mg/kg of feed, exerted an antioxidant effect on chicken tissues. 4. Dietary alpha-tocopheryl acetate supplementation at 200 mg/kg of feed displayed greater antioxidant activity than oregano oil at either supplementation rate. 5. Thigh muscle was more susceptible to oxidation than breast muscle, although the former contained alpha-tocopherol at higher concentration. Muscle alpha-tocopherol is an important factor influencing lipid oxidation, but the influence of polyunsaturated fatty acids and content of pro-oxidants must be taken into consideration too.

New simple liquid chromatographic method for the determination of trimethoprim, sulfadiazine and N4-acetylsulfadiazine in plasma of broilers.

A new method for simultaneous quantification of trimethoprim, sulfadiazine and N4-acetylsulfadiazine in plasma of broilers at levels down to 13-16 ng/ml has been developed. Samples were deproteinized with acetonitrile, defatted with hexane, and extracted with dichloromethane. Chromatographic analysis was carried out on a C18 column in the presence of tetrabutylammonium hydrogen sulfate, a competing base, while detection was performed at 240 nm for trimethoprim, and 270 nm for both sulfadiazine and N4-acetylsulfadiazine. Accuracy and precision data showed recoveries and relative standard deviation values better than 87.3% and 3.1%, respectively, for all three analytes. The good analytical characteristics of the method could allow limits of detection in the low ng/ml range to be realised. The method was successfully applied to determine drug concentrations in plasma samples from broilers administered a combination of sulfadiazine and trimethoprim.

The effect of dietary oregano essential oil on lipid oxidation in raw and cooked chicken during refrigerated storage.

The antioxidative effect of dietary supplementation with oregano essential oil on susceptibility of raw and cooked breast and thigh muscle meat of chickens to lipid oxidation during refrigerated storage for 9 days was investigated. Day-old chickens (n=80) were randomly divided into four groups and fed a basal diet containing 30 mg α-tocopheryl acetate kg(-1) feed as control, or basal diet plus 200 mg α-tocopheryl acetate kg(-1) feed, or basal diet plus 50 or 100 mg oregano essential oil kg(-1) for 38 days prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde (MDA) formation in raw and cooked meat during 0, 3, 6 and 9 days of refrigerated storage, using the thiobarbituric acid (TBA) assay and third-order derivative spectrophotometry. Results showed that dietary oregano essential oil supplementation exerted antioxidative effects, the supplementation being most effective in retarding lipid oxidation in stored raw and cooked meat at the 100 mg oregano essential oil kg(-1) feed. However, dietary α-tocopheryl acetate supplementation at 200 mg kg(-1) feed displayed greater antioxidant activity than oregano treatments. Thigh muscle was more susceptible to oxidation compared to breast muscle in all treatments, although the former tissues contained α-tocopherol at markedly higher levels.

Distribution and stability of aflatoxin M1 during processing, ripening and storage of Telemes cheese.

Telemes cheeses were produced using milk that was artificially-contaminated with aflatoxin M1 at the levels of 0.050 and 0.100 microg/l. The cheeses produced in the two cheese-making trials were allowed to ripen for 2 months and stored for an additional 4 months to simulate commercial production of Telemes cheese. Concentrations of aflatoxin M1 in whey, curd, brine, and the produced cheeses were determined at intervals by liquid chromatography and fluorometric detection coupled with immunoaffinity column extraction. Concentrations of aflatoxin M1 in the produced curds were found to be 3.9 and 4.4 times higher than those in milk, whereas concentrations in whey were lower than those in curd and milk. Aflatoxin M1 was present in cheese at higher concentrations at the beginning than at the end of the ripening/storage period, and it declined to concentrations 2.7 and 3.4 times higher than those initially present in milk by the end of the sixth month of storage. Concentrations of aflatoxin M1 in brine started low and increased by the end of the ripening/storage period but only a portion of the amounts of aflatoxin M1 lost from cheese was found in the brine. Results showed that Telemes cheeses produced from milk containing aflatoxin M1 at a concentration close to either the maximum acceptable level of 0.05 microg/l set by the European union (EU) or at double this value, will contain the toxin at a level that is much lower or slightly higher, respectively, than the maximum acceptable level of 0.250 microg of aflatoxin M1/kg cheese set by some countries.

Rapid determination of cholesterol in milk and milk products by direct saponification and capillary gas chromatography.

A simple method is described for the determination of cholesterol in milk and milk products. Samples (0.2 g) are saponified in capped tubes with 0.5 M methanolic KOH solution by heating for 15 min at 80 degrees C. Water is added to the mixtures, and the unsaponifiable fractions are extracted with hexane to be further analyzed by capillary gas chromatography. Because of the rapid sample preparation and gas chromatographic procedures, a single sample can be analyzed in 30 min. Overall recovery was 98.6%, and the linearity was excellent for the fortification range examined. Precision data that were based on the variation within and between days suggested an overall relative standard deviation value of 1.4%. The method has been successfully applied to quantitate cholesterol in a variety of milk products.

Albendazole-related drug residues in milk and their fate during cheesemaking, ripening, and storage.

The level and nature of the albendazole residues in milk of treated cows were determined as a function of the time of milking (12-h intervals), and the fate of those residues during cheesemaking, ripening, and storage was examined when the obtained milk was used for making Teleme cheese. Ion-pair liquid chromatographic analysis with fluorescence detection showed that the albendazole sulfoxide metabolite reached its maximum (523 +/- 199 micrograms/kg) at the 1st milking and declined below the detection limit by the 4th milking. The sulfone metabolite attained its highest level (812 +/- 99 micrograms/kg) more slowly (at the 2nd milking) and declined below detection limit by the 13th milking. The 2-aminosulfone metabolite, which was present in the milk obtained at the 1st milking, reached its maximum (128 +/- 36 micrograms/kg) at the 3rd milking, and slowly declined to a level below detection limit by the 15th milking. Whey and cheese analysis revealed that about 70% of each major metabolite initially present in milk could be distributed in the whey. The remaining 30% occurred in the cheese at residue levels higher than those initially present in the milk of the 1st or 2nd milking (688 versus 445 or 450 versus 230 micrograms/kg for albendazole sulfoxide; 890 versus 608 or 1502 versus 783 micrograms/kg for albendazole sulfone; 19 versus 15 or 161 versus 105 micrograms/kg for albendazole 2-aminosulfone). Ripening and storage of the cheeses made from milks from the 1st or 2nd milkings results in a decrease of the sulfoxide metabolite (to 225 or 206 micrograms/kg), an increase of the sulfone metabolite (to 1,181 or 1,893 micrograms/kg), and no effect on the 2-aminosulfone metabolite.

Determination of the marker residue of albendazole in cheese by ion-pair liquid chromatography and fluorescence detection.

A liquid chromatographic method is described that allows quantitative determination of the marker residue of albendazole in cheese. Samples were extracted with acetonitrile, and the extracts were defatted with hexane, evaporated to dryness, reconstituted in ethyl acetate, and purified by partitioning with phosphate buffer. Separation of the sulfoxide, sulfone, and 2-aminosulfone metabolites that constitute the marker residue of albendazole was carried out isocratically with a mobile phase containing both positively and negatively charged pairing ions; detection was performed fluorometrically, with excitation and emission wavelengths of 290 and 320 nm, respectively. Overall recoveries ranged from 73.7 to 84.9%. Precision data based on variation within and between days suggested overall values for relative standard deviation of 3.0 to 3.9%. The sensitivity of the method permitted low limits of detection, particularly for the sulfone and 2-aminosulfone metabolites.

Trace analysis of albendazole and its sulphoxide and sulphone metabolites in milk by liquid chromatography.

Analytical methodology for determination of albendazole and its sulphoxide and sulphone metabolites in milk at levels down to 2-5 ng/ml has been developed. Extraction was carried out with ethyl acetate under alkaline conditions, and extracts were analyzed on a silica-based C18 column in the presence of positively-charged pairing ions. Accuracy data showed overall recoveries ranged from 78.4% to 100%, whereas precision data, based on within and between-day variation, suggested overall precision values better than 4.9%. The method was successfully applied to determine residues in milk of a dairy cow orally given albendazole.

Rapid determination of amphotericin B in serum and urine by third-order derivative spectrophotometry.

A derivative spectrophotometric method for rapid monitoring of amphotericin B in serum and urine down to 30 ng/mliters is described. Samples are treated with acetonitrile, and amphotericin B is directly quantified in the crude extracts on the basis of the intensity of the peak that appears at 402 nm when the normal absorption spectrum is submitted to third-order derivative processing. Accuracy data suggested recoveries in the range of 84.3-94.9% for serum and 85.6-93.4% for urine. The precision of the method was better than 11.3% for serum and 9.2% for urine when samples contained as low as 29.6 ng/mliters of amphotericin B. Ease of applicability, short analysis time, low cost, and reliability are the main advantages of the method.

Rapid spectrophotometric method for analyzing natamycin in cheese and cheese rind.

A rapid spectrophotometric method for determining natamycin in cheese and cheese rind has been developed. Samples are homogenized with acidified aqueous acetonitrile and homogenates are filtered. Natamycin is directly quantitated in filtered extracts on the basis of the characteristic third-derivative trough at 322.6 nm. Additional cleanup of extracts is not required because derivative transformation of the conventional analytical band at around 319 nm eliminates spectral interferences from other compounds. The analysis is simple and can be completed in 6 min. The equipment is easily accessible because most modern spectrophotometers allow instant generation of derivative spectra. The method needs small amounts of solvents and has good analytical characteristics. Overall recovery was 98.4 +/- 0.7%, and linearity was excellent (r = 0.9998) in the range examined (0.5-20 mg/kg). Quantitation and detection-limits were estimated at 0.5 and 0.25 mg/kg, respectively. Precision statistics based on within-day and between-days variations suggest an overall relative standard deviation of 1.4%.

Rapid ion-pair liquid chromatographic method for the determination of fenbendazole in cows' milk.

A simple and rapid methodology for the analysis of fenbendazole residues in cows' milk, at levels down to 3 ng ml-1, has been developed. Samples are extracted with acetonitrile and centrifuged. The supernatant is de-fatted with isooctane, and mixed with dichloromethane. The separated aqueous layer is discarded, while the bottom organic layer is washed with a phosphate buffer (pH 10) and evaporated to dryness. The residue is dissolved in the mobile phase and analysed by ion-pair reversed-phase liquid chromatography, using octanesulfonate as the ion-pair reagent. Over-all recovery was found to be 99.0%, linearity was excellent and precision data based on within- and between-day variation suggested an over-all variation of 2.0%.