Maximum Residue Limit Values Research Articles

Residues of Oxytetracycline and Its 4′-Epimer in Edible Tissues from Turkeys

Residues of oxytetracycline (OTC) in edible tissues (muscle, liver, and kidney) of 18 turkeys were determined after continuous administration of the drug for 3 days in drinking water at the maximum recommended concentration of 400 mg/L. The European Union (EU) maximum residue limits (MRLs) set for OTC are 100 microg/kg in muscle tissues, 300 microg/kg in liver, and 600 microg/kg in kidney, as the sum of the parent compound and its derivative 4'-epi-oxytetracycline (4-epi-OTC). Cleanup of tissue samples was performed by metal chelate affinity chromatography (MCAC), but the original technique was miniaturized by the adoption of a mini solid-phase extraction column, allowing reduction of solvents, time, and hazardous waste. OTC and its 4'-epimer were quantitated by an isocratic liquid chromatography elution with UV detection. After 1 day of withdrawal, OTC plus 4-epi-OTC residues were greater than MRL values in muscle and liver; 3 days after the end of treatment, all tissue residues were far lower than the MRL values. At the first day after the end of treatment, 4-epi-OTC was detected at very low concentrations only in muscle, in liver after 1 and 3 days of withdrawal, and in kidney at all sampling times. The withdrawal time was calculated according to EU recommendations and was set at 5 days.

Capillary zone electrophoresis determination of oxytetracycline in pig tissue samples at maximum residue limits

The determination of the antibiotic oxytetracycline (OTC), in pig tissues was investigated by capillary zone electrophoresis (CZE) with a prior solid-phase extraction (SPE) using alkyl-bonded silica and polymeric cartridges. The methodology developed allows determination of OTC in pig kidney, liver and muscle samples with detection limits below maximum residue limit values, and the procedures to extract OTC and clean-up the matrix are simple and reliable. The limit of detection for OTC was 160, 120 and 85 μg kg−1 for kidney, liver and muscle samples, respectively. The average recoveries from spiked samples (200 μg kg−1 and 1600 μg kg−1) were in excess of 63% with coefficients of variation between 2.0 and 9.8%. This method would be useful for routine monitoring of oxytetracycline residues in pig tissues.

Use of norfloxacin in poultry production in the eastern province of Saudi Arabia and its possible impact on public health

Samples of market-ready chicken muscle and liver from 32 local broiler farms were first screened for antibiotic residues by microbiological assay. The antibiotic-residue-positive muscles and livers from 22 farms were further analysed for norfloxacin (NFX) residues by high performance liquid chromatography. NFX was detected in 35.0% and 56.7% of raw antibiotic-residue-positive muscles and livers, respectively. The NFX-positive muscles and livers were respectively obtained from 11 (50.0%) and 14 (63.6%) of the 22 antibiotic-residue-positive farms. Since the maximum residue limit (MRL) for NFX has not yet been fixed, the MRL for enrofloxacin was used in the study. All NFX-positive farms had mean raw tissue levels, which were 2.7- to 34.3-fold higher than the MRL. Although cooking markedly reduced NFX tissue concentrations, mean detectable levels remained above MRL in large proportions of NFX-positive samples and farms. Susceptibility patterns of Enterobacteriaceae isolates from chicken and human patients to NFX showed alarmingly high rates of resistance in chicken isolates especially among Escherichia coli (45.9%) and Pseudomonas spp. (70.6%) compared with patients' isolates (10.5% and 18.2%, respectively). The study reveals widespread misuse of NFX in the local poultry industry, which may pose a major risk to public health including possible stimulation of bacterial resistance and hypersensitivity reactions to fluoroquinolones. More prudent use of fluoroquinolones in food-producing animals is therefore recommended. Further, there is a need to establish MRL values for NFX.

Dissipation of Lindane and Fenvalerate Residues in Chickpea (Cicer arietinum L.) under Indian Climatic Conditions

Dissipation behavior of lindane 20 EC (400 and 800 g a.i./ha) and fenvalerate 0.4% dust (75 and 150 g a.i./ha) applied on chickpea (var. H 208) for controlling pod borer under field conditions during rabi 1994–1995 at pod initiation stage was studied. Grains from lower dose of lindane at harvest contained residues below maximum residue limit value (0.25 μg g−1), whereas no measurable amount of fenvalerate residues were found in grains of both doses at harvest. A waiting period of 7 days for lindane and 1 day for fenvalerate is suggested from point of hazards due to residues, when applied at recommended dose. The residues calculated from consumption of chickpea (60 g/person/day) is much below the maximum permissible intake of lindane and fenvalerate; hence the recommended doses can be considered safe from point of view of hazards to humans.

Pharmacokinetic and efficacy studies on bath‐administering potentiated sulphonamides in Atlantic halibut, Hippoglossus hippoglossus L.

The uptake, metabolism, tissue distribution and excretion of four sulphonamides and trimethoprim following bath treatment of Atlantic halibut, Hippoglossus hippoglossus L., were studied. Bath treatment using a concentration of 200 μg ml–1 for 72 h resulted in peak sulphadimidine concentrations in muscle and abdominal organ homogenates of 32·6 and 68·2 μg g–1, respectively. The corresponding values were 24·4 and 73·4 μg g–1 for sulphaguanidine, 6·1 and 45·1 μg g–1 for sulphamethoxazole, 2·1 and 15·1 μg g–1 for sulphadimethoxine, and 99 and 169 μg g–1 for trimethoprim. After a 72‐h treatment, approximately 90% of the sulphadimethoxine and sulphamethoxazole present in tissues was found as the N4‐acetylated metabolite, whereas for sulphadimidine and sulphaguanidine, the N4‐acetylations were from 9 to 23%. Based on these preliminary absorption studies, sulphadimidine was chosen as the companion sulphonamide to trimethoprim. Using a combination of 500 μg ml–1 sulphadimidine and 100 μg ml–1 trimethoprim in the bath for 72 h, peak muscle and liver concentrations of 262 and 312 μg g–1, respectively, for sulphadimidine and 32·8 and 83·6 μg g–1, respectively, for trimethoprim were achieved. Elimination half‐lives (t1/2β) for sulphadimidine were calculated to be 35 and 48 h for muscle and liver, respectively. The corresponding values for trimethoprim were 98 and 116 h. Using the 95% confidence limit for single observations (95% prediction limit) and a maximum residue limit (MRL) value of 0·05 μg g–1 for trimethoprim and 0·1 μg g–1 for sulphadimidine, the elimination times (Et95) for muscle and liver were calculated to be 18 and 26 days, respectively, for sulphadimidine and 40 and 55 days, respectively, for trimethoprim. Minimum inhibitory concentrations (MIC) values against selected strains of Vibrio sp. were equal to or above 128 μg ml–1 for sulphadimidine, between 0·25 and 4·00 μg ml–1 for trimethoprim and between 0·4 and 8·8 μg ml–1 for various ratios of the sulphadimidine:trimethoprim combination. In the tested ratios, the combined antimicrobial action of trimethoprim and sulphadimidine were synergistic, as revealed by their fractional inhibitory concentration (FIC) indices. In general, the 1:5 trimethoprim sulphadimidine ratio showed the highest degree of synergism. Using a combination of 500 μg ml–1 sulphadimidine and 100 μg ml–1 trimethoprim in the bath for 72 h, concentrations greater than a MIC value of 0·8 μg ml–1 were maintained for 22 days in muscle and 29 days in liver. In a laboratory challenge experiment using Vibrio anguillarum strain HI 11347, a significantly lower mortality was observed in the drug‐treated group (40%) compared to the untreated control group (93%).

Residues of cypermethrin, fenvalerate and deltamethrin on cauliflower

Following the application of Cypermethrin, fenvalerate and deltamethrin to a cauliflower crop at rates of 50, 50 and 12 g a.i. ha-1, the maximum initial deposits of these insecticides on heads and leaves were 1.10 and 0.75, 1.14 and 0.60, and 0.32 and 0.12 mg kg-1, respectively. These residue values for fenvalerate were less than the maximum residue limit (MRL) of 2 mg kg-1 for this crop. While the maximum initial deposits of Cypermethrin and deltamethrin on cauliflower leaves were less than their respective MRL values of 1 and 0.2 mg kg-1 for brassica leafy vegetables, it took one day for their residues on cauliflower heads to decline below this level.

Evaluation of FAO/WHO pesticide standards in relation to polish and honduran diets

The FAO/WHO Codex Alimentarius Commission publishes a Guide to Codex Maximum Limits for Pesticide Residues (1978) which gives both acceptable daily intake (ADI) values and maximum residue limit (MRL) values for many pesticides in raw agricultural commodities (rac's) from crops on which their use is approved. ADI values are determined from animal toxicology data which give a no-observable-effect level (NOEL) and use of a safety factor. Specific MRL values are calculated from the ADI and a food factor ( F), which is the decimal fraction of that rac in the assumed typical diet. One of the difficulties with this procedure is that dietary patterns differ substantially between countries. Whatever dietary pattern is assumed in calculation of the MRLs may be inappropriate for that country. Theoretical maximum residue intakes (TMRIs) were calculated from the Codex ADIs and MRLs using F values calculated from the national dietary patterns published separately in Poland and Honduras. The equation is TMRI = ΣMRL i × F i × D, where D is the daily individual diet weight of rac's in kilograms for the particular country. The TMRI should be lower than the maximum permitted intake (MPI) calculated as MPI = ADI × 60, where the 60 is an arbitrary human body weight in kilograms. The TMRI exceeded the MPI for 16 of 33 pesticides used in Poland and for 10 of 20 used in Honduras. At the extreme, the Polish TMRI/MPI ratio for aldrin-dieldrin is 19.5 and 18.1 for fenithion; nine pesticides had ratios of 4.0 or higher. For Honduras, piperonyl butoxide gave the highest ratio, 5.7 and three pesticides had ratios of 4.0 or higher. For Poland, the MRLs for 13 pesticides would cause the MPI to be exceeded by the theoretical residue concentrations of only one crop; in Honduras, seven pesticides have single-crop TMRIs greater than the MPI. Thus, these standards appear inappropriate for Poland and Honduras.

Investigation of veterinary psychopharmaceuticalwith the Salmonella/microsome test

A quick, simple method is described for quantifying promazine derivatives (propionylpromazine, acepromazine and chlorpromazine), xylazine, carazolol, azaperone, and the latter’s main metabolite, azaperol. Liquid extraction was followed by a clean-up on an Oasis® SPE cartridge. For unequivocal identification of each analyte, two ions were detected. Validation was carried out on kidney and muscle samples spiked respectively with 1 and 2.5 g kg−1, in the case of molecules for which there is no Maximum Residue Limit (MRL). For the other molecules, the MRL value was taken into account. The method described meets all the criteria of the SANCO directive and is easy to use in routine analysis. Tissue-level elimination was studied in animals treated with these molecules.

Residual ethylene dibromide and inorganic bromide levels in some fruit and vegetables after fumigation with ethylene dibromide or methyl bromide

Residues of ethylene dibromide (EDB) were determined at periods up to seven days after fumigation of capsicum, mango, papaw, passionfruit, pumpkin and zucchini. Residues of inorganic bromide were also determined at periods up to seven days after EDB fumigation for capsicum, cucumber, mango, papaw and passionfruit. All commercially recommended EDB treatments, with the exception of that for zucchini, resulted in EDB residues at three days from 6 to 16 times the recommended maximum residue limit (MRL) of 0.1 mg kg-1, specified for a with-holding period of two days. All the inorganic bromide residues determined up to seven days after EDB fumigation were below the current recommended MRL values. Inorganic bromide residues were also determined for avocadoes fumigated with methyl bromide. After seven days the residues for full ripe fruit slightly exceeded the recommended MRL of 75 mg kg-1, while thosefor mature green and for mixed green and ripe fruit were slightly less than the recommended MRL.