Hatchery Losses in Flocks of Layer and Broiler Breeders Due to Feed Contamination with Nicarbazin and Narasin: A Case Report

In the current study, we investigated decreased hatchability and increased embryonic mortality in two farms of layer breeders (flocks A1 and B1) and a farm of broiler breeders (flocks C1 and C2) from Austria, which also presented discoloration of eggshells in 2% of the eggs. After conducting clinical evaluations and the approval that the feed operator was common for flocks A1 and B1, and C1 and C2, it was decided to investigate the feed. Our findings revealed that the feed contained levels of nicarbazin and narasin up to five and 14 times, respectively, above the maximum limits allowed by the European Union for nontarget species. On the other hand, there were no significant abnormalities in vitamin levels, which were also described as the etiology of the noticed abnormalities. Switching to a noncontaminated feed resulted in the clinical signs and production parameters returning to expected ranges. This report emphasizes the significance of considering feed contamination by nicarbazin and narasin as a potential cause of hatchery losses in nontarget species, even in the absence of other clinical signs.

OUP accepted manuscript

Background

AOAC Method 2013.07 was adopted as First Action in 2013. Since then, the method has been used in numerous residue depletion studies with favorable comments from analysts.

Objective

To analyze data from residue depletion studies to support Final Action status.

Method

Ten residue depletion studies were conducted during May 2014 through May 2019. For each study, harvested incurred tissues were analyzed for nicarbazin using AOAC Method 2013.07 in 1 of 4 laboratories. Each analytical run included one or more fortified quality control test portions. The data from these known fortified matrix test portions were analyzed for reproducibility and repeatability.

Results

For muscle tissues, relative recovery was 90.4% (95% CI 83.8 to 97.5); RSD_r was 5.4% (95% CI 3.8 to 9.2); and RSD_R was 7.9%. In the liver, values were 94.5% (95% CI 91.1 to 98.0), 5.8% (95% CI 4.1 to 9.9), and 6.8%, respectively. In the kidney, values were 91.5% (95% CI 85.3 to 98.1), 5.2% (95% CI 3.7 to 8.8), and 9.0%, respectively. In skin with adhering fat, values were 94.5% (95% CI 89.2 to 100.1), 8.9% (95% CI 6.3 to 15.1), and 8.9%, respectively. In all cases, repeatability and reproducibility were within acceptable limits.

Conclusions

The data and positive feedback support the transition of AOAC Method 2013.07 from First Action to Final Action.

Highlights

Final action status is supported by data collected during routine use of the method rather than a traditional multi-laboratory collaborative study. Data were subjected to statistical analysis using the pC-metamer, and then transformed back to the traditional C-metamer.

Investigation of the causes for the occurrence of residues of the anticoccidial feed additive nicarbazin in commercial poultry

Investigations were undertaken to identify causes for the occurrence of high levels of the zootechnical feed additive nicarbazin in broiler liver at slaughter. The first investigation on 32 commercial broiler flocks involved sampling and analysis for nicarbazin (as dinitrocarbanilide, DNC) in liver from birds during a 3-10-day period after withdrawal of nicarbazin from their feed and before commercial slaughter. DNC residues in liver samples of broilers scheduled as being withdrawn from nicarbazin for > or =6 days ranged from 20 to >1600 microg kg(-1) (the specified withdrawal period for nicarbazin is 5 days and the Joint Expert Committee on Food Additives (JECFA) maximum residue limit (MRL) is 200 microg kg(-1) liver). Further on-farm investigations on 12 of these flocks, selected on the basis of the feeding system in use and the levels of DNC residues determined in liver, identified issues in feed management contributing to elevated residues in broiler liver. A significant correlation (0.81, p < 0.01, n = 10) between DNC residues in liver samples and in feed samples from the feeding pans was observed. The second investigation on 12 commercial broiler flocks involved sampling and analysis for DNC in liver samples and feed samples from feeding pans and from the feed mill at the three thinnings of birds for commercial slaughter. In the case of one flock, a clear relationship between nicarbazin in feed from the feed mill (10.5 mg kg(-1) DNC), in feed from the feeding pans (6.6 mg kg(-1) DNC) and in liver (583 microg kg(-1) DNC) at first thinning (9 days scheduled withdrawal from nicarbazin) was observed. Such a clear relationship was not observed in other cases, particularly at second and third thinnings, pointing to re-exposure of birds to nicarbazin late in the flock production cycle, probably from the litter. Guidelines outlining best farm practice to eliminate nicarbazin residues in poultry have been published in booklet and poster format for broiler producers and deal with feed system cleaning, feed bin management, feed deliveries, feed usage and records.

Development and validation of a lateral flow device for the detection of nicarbazin contamination in poultry feeds

Concentrations of the coccidiostat nicarbazin as low as 2 mg/kg in feed can result in violative drug residues arising in poultry liver. A lateral flow device (LFD) was developed for the detection of contaminating concentrations of nicarbazin following solvent extraction of poultry feeds. Test results, as determined by both visual and instrumental measurement, are available within minutes. For 22 feed samples, nicarbazin-free and fortified at 2 mg/kg, the % relative inhibition ranged from 0 to 45% and from 53 to 85%, respectively. Nicarbazin contamination at the critical concentration (2 mg/kg) can be determined in all cases providing the sampling is representative. A wide range of feed samples taken at a mill that incorporated nicarbazin into poultry feed were analyzed. Data generated for these samples by both the LFDs and a mass spectrometric method were compared, and a significant correlation was achieved.

Screening for the coccidiostats halofuginone and nicarbazin in egg and chicken muscle: development of an ELISA

Nicarbazin and halofuginone have been widely used as coccidiostats for the prevention and treatment of coccidiosis in poultry. It has been shown that accidental cross-contamination of feed can lead to residues of these compounds in eggs and/or muscle. This paper describes a direct competitive assay for detecting halofuginone and nicarbazin, developed as qualitative screening assay. In an optimized competitive ELISA, antibodies showed 50% binding inhibition at approximately 0.08 ng ml(-1) for halofuginone and 2.5 ng ml(-1) for dinitrocarbanilide (marker residue for nicarbazin). Extraction from the matrix was carried out with acetonitrile followed by a wash with hexane. The assay's detection capability (CCbeta) for halofuginone was < 0.5 microg kg(-1) in egg and < 1 microg kg(-1) in muscle. For dinitrocarbanilide, the CCbeta was estimated at < 3 microg kg(-1) in egg and < 10 microg kg(-1) in chicken muscle.

The effect of cooking on veterinary drug residues in food: Nicarbazin (Dinitrocarbanilide component)

The change of concentration of residues of the marker compound for the anti-coccidial drug nicarbazin, N,N'-bis(4-nitrophenyl)urea (dinitrocarbanilide, DNC), was investigated in model oil and aqueous solutions and in chicken muscle and egg. In model aqueous solutions, DNC decreased rapidly in concentration upon heating followed by a much more gradual decomposition. The curves produced when this information was plotted were not typical of exponential decay. In model cooking oil solutions, DNC generally showed a slower decrease in concentration over time when compared with aqueous solutions. DNC residues in egg were stable to microwave cooking and residues in chicken muscle were stable to stewing and microwaving. Other cooking procedures led to a decrease in amount of DNC by 22% to 48% of the total amount of analyte present. Only a small amount (<2%) of residue leached with juices which exuded as the food was cooked.

Efficient HPLC method for the determination of nicarbazin, as dinitrocarbanilide in broiler liver

A simple, fast and reliable HPLC-UV method has been developed for the determination of dinitrocarbanilide residues in broiler liver. Liver samples (2 g) were extracted with two portions of acetonitrile (10 and 5 ml), defatted with hexane and evaporated to dryness under nitrogen. Extracts were reconstituted in acetonitrile-water (70/30, v/v, 500 microl), loaded onto C18 solid phase (SPE) cartridges and eluted with acetonitrile-water (70/30, v/v, 2.5 ml) into clean test-tubes. Extracts were evaporated to dryness and reconstituted in acetonitrile-water (80/20, v/v, 500 microl). An aliquot of the extract was assayed by high performance liquid chromatography (HPLC) with UV detection at 350 nm. The method was validated according to EU guidelines using liver tissues fortified at levels of 100, 200 and 300 microg/kg, with dinitrocarbanilide. The decision limit (CC(alpha)) and the detection capability (CC(beta)) were calculated from the within laboratory repeatability data to be 228 and 266 microg/kg, respectively. The mean recovery was typically >70% and the limits of quantitation was 12.5 microg/kg (based on the lowest standard on the calibration curve).

Liquid chromatographic method for nicarbazin in broiler feeds and premixtures: development, validation, and interlaboratory study

A reversed-phase liquid chromatography method for nicarbazin in broiler feeds and premixtures was developed, validated, and interlaboratory studied. The extraction solvent was an acetonitrile-methanol (1 + 1) mixture. For feedingstuffs, water was also added. The 4,4'-dinitrocarbanilide moiety of nicarbazin was detected at a wavelength of 350 nm. Recovery was > or =87%. At 20 mg/kg, the repeatability was 0.7% and the within-laboratory reproducibility was 2.7%. The limit of determination was <20 mg/kg. Other feed additives did not interfere in the assay that proved to be applicable to broiler feeds from different European Union countries. In an interlaboratory study, 4 positive broiler feeds, 1 blank pig feed, and 1 broiler premixture were analyzed by 19 laboratories using the method developed in this study. The relative standard deviation for repeatability (RSDr) of the feedingstuffs (20-240 mg/kg) varied between 2.6 and 10.2%. The HORRAT ranged between 0.70 and 1.22. Recoveries were 91-108%. Three laboratories detected small signals in the blind blank samples, ranging from 0.4 to 2 mg/kg. For the premixture, acceptable results for reproducibility could only be obtained after the sample weight and volume of extraction had been doubled. To avoid excessive dilution of the extracts, the range of the calibration curve had also been doubled. With this modified method, the RSDr was 5.7% and the HORRAT was 1.95 (10 laboratories).

An all-in-one dry chemistry immunoassay for the screening of coccidiostat nicarbazin in poultry eggs and liver

An automated immunoassay for the detection of nicarbazin residues in poultry eggs and liver was developed. The assay was based on a novel all-in-one dry chemistry concept and time-resolved fluorometry. The analyte specific antibody was immobilized into a single microtiter well and covered with an insulation layer, on top of which the label was dried in a small volume. The extracted sample was added automatically to the dry microtiter well, and the result was available within 18 min. Due to the rapidity and simplicity, the quantitative immunoassay could also be used as a high throughput screening method. The analytical limit of detection for the assay was calculated as 0.1 ng mL(-)(1) (n = 12) and the functional limit of detection as 3.2 ng g(-)(1) for egg (n = 6) and 11.3 ng g(-)(1) for liver (n = 6) samples. The sample recovery varied from 97.3 to 115.6%. Typically, the intra-assay variations were less than 10%, and interassay variations ranged between 8.1 and 13.6%.

Liquid chromatographic determination of 4,4'-dinitrocarbanilide, the active component of the infertility agent nicarbazin, in chicken, duck, goose, and snake eggs

4,4'-Dinitrocarbanilide (DNC) was extracted from chicken, duck, goose, and snake eggs and isolated by reversed-phase liquid chromatography. DNC was detected by ultraviolet absorbance at 347 nm and quantitated by comparison with a calibration standard. Recoveries of DNC from fortified control chicken, duck, goose, and snake egg samples were determined for DNC levels of 0.16, 10, and 16 microg/g. The mean recoveries from chicken, duck, goose, and snake eggs were 92 +/- 4, 88 +/- 9, 87 +/- 7, and 95 +/- 6%, respectively. The method limits of detection for DNC in chicken, duck, goose, and snake eggs ranged from 0.015 to 0.035 microg/g. The reported method is much simpler than and equally efficient as previous methods developed for the determination of DNC residues in egg contents.

[Simple determination of residual anticoccidial drugs (diclazuril and nicarbazin) in chicken tissues by HPLC]

A simple and rapid determination of anticoccidial drug residues, diclazuril (DCZ) and nicarbazin (NCZ), in chicken tissues has been developed. DCZ and NCZ were extracted with acetonitrile from chicken liver, muscle, and fat. The extract was rinsed with n-hexane saturated with acetonitrile and then evaporated. The residue was dissolved in 1.4 mL of acetonitrile-methanol (1:1), then 1.0 mL of n-hexane saturated with acetonitrile-methanol (1:1) was added, and the mixture was partitioned by the addition of 0.6 mL of water. DCZ and NCZ in the aqueous layers were determined by HPLC on an Xterra RP-18 column with acetonitrile-0.5% ammonium acetate containing 0.01 mol/L tetra-n-butylammonium hydrogen sulfate (43:57) as the mobile phase. The mean recoveries (n = 5) of DCZ and NCZ spiked in chicken tissues at the maximum residue levels were 92.0-95.6% (CV 2.4-3.0%) and 87.3-89.4% (CV 1.7-2.8%), respectively. The detection limits of DCZ and NCZ were 0.01 and 0.004 microgram/g, respectively.

Determination of 4,4'-dinitrocarbanilide (DNC), a component of Nicarbazin, in Canada goose (Branta canadensis) eggshells using high-performance liquid chromatography

A method was developed using high-performance liquid chromatography to assay 4,4'-dinitrocarbanilide (DNC), the active ingredient in Nicarbazin, in eggshells collected from Canada geese fed a formulated feed fortified with Nicarbazin at doses of 0, 125, 250, and 500 microg/g. The method was developed using chicken eggshells fortified with DNC. The method was used to quantify DNC in both the shell-associated membranes and the calcified shell extracellular matrix. These values were compared to those obtained for a composite sample consisting of both the membranes and the calcified shell extracellular matrix. The validated method was used to quantify DNC in eggshells from geese fed fortified feed to ascertain the effect of Nicarbazin feed concentration on shell DNC concentration. DNC levels in the eggshells were highly correlated with feed dose.

Contamination of animal feedingstuffs with nicarbazin: investigations in a feed mill

Some mechanisms of nicarbazin contamination were investigated in a feed mill. Three sequential 3-tonne batches of nicarbazin-free feed were produced directly after a batch of nicarbazin-containing feed (125 mg kg(-1)). Sampling of the nicarbazin-free feed took place at two points before pelleting and at one point post-pelleting. The study was repeated on two further occasions, i.e. three separate nicarbazin-containing feeds and 27 tonnes of 'flushing' feeds were manufactured and sampled in total. Pre-pelleting, the highest nicarbazin concentrations (3.4+/- 0.26 mg kg(-1)) were observed in the first tonne milled after the nicarbazin containing ration. Thereafter, concentrations steadily declined in successive batches. Post-pelleting samples contained much higher concentrations of the drug. After 8 tonnes had passed through, the concentrations (7.2+/- 1.29 mg kg(-1)) were between 10 and 20 times greater than the corresponding concentrations detected post-mixing. These concentrations are sufficient to cause violative residues in eggs and broiler liver. The practice of returning post-press sieved material to the pre-press bins was identified as the cause of the problem. Re-routing of sieved material along with better segregation of nicarbazin-containing and nicarbazin-free feedingstuffs markedly reduced the incidence of feed contamination with this compound.

High-performance liquid chromatography-based determination of nicarbazin excretion in waterfowl

A method for the high-performance liquid chromatography (HPLC) determination of nicarbazin uptake and excretion in ducks is presented. The method uses few clean-up steps and provides a rapid assessment of nicarbazin excretion by measuring the analyte 4,4'-dinitrocarbanalide (DNC). During method development the effect of extraction volume, number of extractions, mobile phase composition, column temperature, and injection volume were varied to optimize sensitivity and achieve as short a run time as possible. For our purposes, a 2 x 5.0 ml 1:1 dimethyl formamide (DMF):acetonitrile (ACN) extraction injected (40 ml) into an HPLC system equipped with a Keystone octadecylsilyl (ODS) C18 column and a UV variable wavelength detector (lambda=347 nm) with a mobile phase of 60:40 (v/v) ACN-H2O, at a flow-rate of 1.0 ml/min at a column temperature of 35 degrees C provided adequate resolution and an acceptable total run time. Studies conducted during method development for inter-day recovery efficiencies for 0.46, 1.8 and 88.5 microg fortified samples (n=3) had mean recoveries of 91, 94 and 97% and intra-day (n=3) recoveries at the same fortification levels of 103, 94, and 92%. The method has been used successfully in excretion studies of nicarbazin in ducks.

Development and validation of a method for the confirmation of nicarbazin in chicken liver and eggs using LC-electrospray MS-MS according to the revised EU criteria for veterinary drug residue analysis

A method is described for the quantitative confirmation of 4,4'-dinitrocarbanilide (DNC), the marker residue for nicarbazin in chicken liver and eggs. The method is based on LC coupled to negative ion electrospray MS-MS of tissue extracts prepared by liquid-liquid extraction. The [M-H]- ion at m/z 301 is monitored along with two transition ions at m/z 137 and 107 for DNC and the [M-H]- ion at m/z 309 for the internal standard, d8-DNC. The method has been validated according to the new EU criteria for the analysis of veterinary drug residues at 100, 200 and 300 microg kg(-1) in liver and at 10, 30 and 100 microg kg(-1) in eggs. Difficulties concerning the application of the new analytical limits, namely the decision limit (CCalpha) and the detection capability (CCbeta) to the determination of DNC in both liver and eggs are discussed.

Possible causes of nicarbazin residues in chicken tissues

Two experiments were carried out to investigate possible causes of nicarbazin residues in broiler chicken tissues. The first experiment was designed to establish whether feeding nicarbazin as stipulated in the product license can result in 4,4'-dinitrocarbanilide (DNC) tissue residues exceeding the JECFA MRL (200 micrograms/kg). It was shown that the MRL was exceeded in the livers of broilers housed on deep litter, but not in those of broilers housed on wire flooring. Muscle DNC concentrations were well below the MRL. The higher residual tissue concentrations in birds housed on deep litter were attributed to faecal recycling. The second experiment was to establish the relationship between nicarbazin-contaminated withdrawal ration up to the point of slaughter and DNC residues in the tissues of broilers that had not been previously exposed to nicarbazin. Tissue DNC concentrations were found to be proportional to feed concentrations. The housing method caused no significant difference in tissue residues. Meal containing nicarbazin at a concentration of 2.4 mg/kg or greater caused liver DNC residues above the JECFA MRL. Violative residues may, therefore, occur in chickens not exposed to nicarbazin during rearing, but fed withdrawal ration contaminated at 2.4 mg/kg or greater, or in chickens housed on deep litter and fed nicarbazin-medicated meal according to the product license even when the withdrawal ration is nicarbazin-free.

Nicarbazin contamination in feeds as a cause of residues in eggs

A survey was carried out to investigate the prevalence of nicarbazin residues in eggs in Northern Ireland. Nicarbazin, in the form of 4,4'-dinitrocarbanilide (DNC), was detected in 39 of the 190 eggs analysed. An experiment was designed to establish the relationship between nicarbazin-contaminated feed and nicarbazin residues in eggs. The concentrations of both the DNC and 4,6-dimethyl-2-hydroxypyrimidine (DHP) components of the drug in eggs were proportional to feed levels. The maximum feed nicarbazin concentration of 12.1 mg/kg (8.6 mg/kg DNC and 3.5 mg/kg DHP) gave rise to mean maximum whole egg concentrations of 631 micrograms/kg DNC and 51.8 micrograms/kg DHP. After withdrawal of the experimental diet, DNC was undetectable in eggs after 12 days and DHP after 3 days. Feed contaminated with nicarbazin at concentrations greater than about 2 mg/kg gave rise to egg DNC residues at concentrations greater than the Differential Action Limit (DAL) set by the UK (100 micrograms/kg). DNC was contained almost entirely in the yolk of the egg, whereas DHP was distributed between albumen and yolk in a ratio of approximately 3:1.

Liquid chromatographic determination of nicarbazin in feeds

A new liquid chromatographic method has been developed for determination of nicarbazin in feeds. Approximately 40 g feed is extracted with 200 mL acetonitrile-water (80 + 20, v/v). An aliquot of the extract is filtered and assayed using a reversed-phase isocratic method that measures the 4,4'-dinitrocarbanilide moiety of nicarbazin at a wavelength of 340 nm. For medicated feeds, the method uses a standard linear range of 5 to 100 microg/mL. For lower levels, a linear range of 50 to 150 ng/mL can be used. The method has a limit of detection of 250 ng/g and a limit of quantitation of 500 ng/g in a 40 g feed sample. Recovery was 99.1%, with a range of 95.2 to 101.8%. In the typical U.S. dosing range of 27 to 113.5 g/ton, the precision of the method based on one analyst, one day, and 2 weighings ranged from 2.8% (113.5 g/ton) to 4.7% (27 g/ton).

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.

Determination of nicarbazin in feeds using liquid chromatography-electrospray mass spectrometry

A method is presented for the determination of the 4,4'-dinitrocarbanilide component of the coccidiostat nicarbazin in animal feeds. Samples are extracted by shaking with methanol and analysed, without further clean-up, using liquid chromatography-electrospray mass spectrometry. A deuterated form of the analyte is employed as internal standard to improve the repeatability of the method. The method has been validated at levels between 0.1 and 100 mg kg-1 with internal standard corrected recoveries between 88 and 101% and RSD values < 8%.

A new and rapid method for the determination of nicarbazin residues in poultry feed, eggs and muscle tissue using supercritical fluid extraction and high performance liquid chromatography

A simple and rapid method, using supercritical fluid extraction (SFE) with off-line high-performance liquid chromatography for the isolation and determination of nicarbazin, a popular broad-spectrum coccidiostatic drug used principally in poultry, is described. Results show good repeatability with a minimum quantification level of 0.4 microgram g-1 and mean 'spiked' recoveries of 98%, 100% and 99% using poultry feeds (n = 18), eggs (n = 28) and chicken tissue (n = 20), respectively. SFE using carbon dioxide is proposed as an alternative isolation method to the current Association of Official Analytical Chemists (AOAC) procedure which involves the use of large volumes of a harmful solvent (dimethylformamide) and requires a long tedious separation and clean-up regime (6 h) prior to its determination.

Determination of nicarbazin in eggs by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A method was developed to determine in eggs 2 components [4,6-dimethyl-2-hydroxypyrimidine and 1,3-bis(4-nitrophenyl)urea] of the anticoccidial drug nicarbazin, used to treat poultry. Samples were extracted with acetonitrile, and the extracts were washed with hexane and evaporated to dryness before analysis by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. By switching from positive to negative ion monitoring and using gradient elution, both components were measured within one run. The limit of quantitation of the assay was 10 ng/g for each component. The results of a preliminary feeding trial in which chickens were fed contamination levels of the drug are also reported.

High-performance liquid chromatographic method for the determination of the dinitrocarbanilide component of nicarbazin in eggs with on-line clean-up

A high-performance liquid chromatographic method for the determination of the dinitrocarbanilide component of the anti-coccidial drug nicarbazin has been developed. The drug was extracted from egg with acetonitrile. The extract was evaporated to dryness and taken up in water-acetonitrile (80:20, v/v). The extract was then injected onto a reversed-phase precolumn. After clean-up with 20% aqueous acetonitrile for 5 min, the precolumn was eluted onto a Chromspher C18 cartridge column with 0.01 M potassium dihydrogen-phosphate pH 4.0-acetonitrile (50:50, v/v). Detection was by ultraviolet at 343 nm. Average recoveries at five levels from 0.005 to 0.500 mg kg-1 were > 80%. The limit of determination was 0.005 mg kg-1.

Liquid chromatographic determination and liquid chromatographic-thermospray mass spectrometric confirmation of nicarbazin in chicken tissues: interlaboratory study

The U.S. Food and Drug Administration sponsored an interlaboratory study of a liquid chromatographic determination with ultraviolet detection of nicarbazin in chicken liver and muscle tissues. The method determined the 4,4'-dinitrocarbanilide (DNC) portion of nicarbazin. The interlaboratory study of the determinative method was successful for nicarbazin at the 4 ppm level. Results showed good reproducibility for the fortified liver and muscle samples. Mean interlaboratory recoveries and percent coefficients of variation at about 4 ppm were 87.1 and 10.9%, respectively, for muscle and 87.4 and 7.5%, respectively, for liver. The interlaboratory analyses of the dosed liver and muscle tissues produced concentration levels similar to those obtained by the sponsor. The confirmatory procedure, which identified DNC in purified tissue extracts, used liquid chromatography-thermospray/mass spectrometry. The confirmatory procedure was successfully evaluated by one FDA laboratory.

[Determination of nicarbazin in imported chicken]

The confirmation and quantitative analysis of nicarbazin (NCZ) in imported chickens were made by high performance liquid chromatography equipped with a photodiode array detector. The results showed that 1 out of 7 chicken samples contained over 30 ng/g of NCZ. The concentrations of NCZ varied from 10 to 120 ng/g according to the parts of the NCZ positive chicken samples.

Determination of nicarbazin in chicken tissues by liquid chromatography and confirmation of identity by thermospray liquid chromatography/mass spectrometry

A liquid chromatographic method is described for the quantitative measurement of nicarbazin in chicken liver, fat, muscle, and skin tissues. The 4,4'-dinitrocarbanilide (DNC) portion of nicarbazin is extracted from tissues with ethyl acetate. After filtration and evaporation, the extract is purified by liquid-liquid partitioning with acetonitrile-hexane and alumina cartridge chromatography. DNC is separated and measured by reverse-phase liquid chromatography (RP-LC) with an octadecylsilyl (ODS) column and a UV detector set at 340 nm. The overall average recovery of DNC added to tissues was 83.4 +/- 3.1%. The lowest level validated in tissues by this procedure was 0.10 ppm. The limit of detection was estimated to be 0.020 ppm. This method provides a sensitive, selective, rapid, and reproducible alternative to existing purification, separation, and detection techniques, such as differential pulse polarography and colorimetry, for determination of nicarbazin in chicken tissues. Identity of DNC is confirmed by subjecting the purified extracts to thermospray-LC/mass spectrometric analysis using negative-ion detection and selected ion monitoring. Three structural-indicating ions at m/z 302, 272, and 164 are monitored in the thermospray-mass spectrum which are characteristic of the DNC molecule.

Rapid procedure for determination of nicarbazin residues in chicken tissues

A procedure is described for the quantitation of nicarbazin residues in chicken tissues. The method includes extraction of tissue with chloroform-ethyl acetate-dimethyl sulfoxide (50 + 50 + 0.8), adsorption on neutral alumina, and subsequent elution of the residues with methanol-pH 6.0 phosphate buffer (1 + 1). Extracts are separated on a 15 cm, 5 micron C18 column with methanol-pH 6.0 phosphate buffer (6.5 + 3.5) as the mobile phase. The dinitrocarbanilide portion of the complex is detected and quantitated with an electrochemical detector in the reductive mode. Recoveries, based on dinitrocarbanilide, were greater than 95% in liver, breast, and thigh muscle tissues fortified with 0.25-8.0 ppm nicarbazin.

[The determination of the coccidiostat nicarbazin in animal tissue and eggs. I. Determination by pulse polarography and high pressure fluid chromatography with electrochemical detection]

The determination of nicarbazin residues in foodstuffs of animal origin by two different methods, polarography, HPLC with electrochemical detection, is described. By applying pulse polarography at the dropping mercury electrode to acetonitrile extracts of animal tissues and eggs, a detection limit of 50 micrograms/kg and mean recoveries of 79% were obtained. The same extracts were used for the HPLC determination with electrochemical detection. This led to a detection limit of 1 microgram/kg. Additional rapid confirmation can be obtained from HPLC using an internal standard (nifursol) and comparing peak area proportions of both substances at varied polarization voltages. The quantitative determination of nicarbazin in chicken eggs by both polarography and HPLC was found to be in good agreement.

[Multi-method for determining residues of chemotherapeutics, antiparasitics and growth promotors in foods of animal origin. 2. Determination of nitrofurans and nicarbazin (dinitrocarbanilide components)]

Nitrofurans and dinitrocarbanilide are extracted from food according to the multiresidue method and detected by Reversed-phase-HPLC with UV-detection at 360 nm. Records of the UV-spectra confirm the results qualitatively. Possibilities for further confirmation are discussed. Substances in amounts below 0.01 mg/kg can only be determined with particular care. Statistical confirmation of this method and possible problems are mentioned. An interlaboratory collaborative study confirmed the method: furazolidone, furaltadone, nitrofurazone, nitrofurantoin, and nicarbazin (the dinitrocarbanilide containing component) were added to homogenized eggs in amounts of 0.005-0.150 mg/kg. The procedure can be standardized as an official analytical method at a detection limit of 0.005 mg/kg for nitrofurans and 0.01 mg/kg for nicarbazin.

Liquid chromatographic determination of nicarbazin in feed

A liquid chromatographic method was developed for the determination of nicarbazin (4,4'-dinitrocarbanilide.2-hydroxy-4,6-dimethylpyrimidine) in chicken feed. Ground feed was extracted with hot dimethylformamide, filtered, and then cleaned up on an alumina column. The nicarbazin was eluted from the column with ethanol and quantitated using a reverse phase C-18 column, with a methanol-water mobile phase and ultraviolet detection at 344 nm. Recoveries at a typical use level of 100 micrograms/g feed averaged 98% with a standard deviation of 3%. Samples fortified at levels as low as 0.1 micrograms/g were analyzed with 92% recovery. The detection limit is 1 ng, and the response is linear between 4 and 1000 ng. Feed additives in combination with nicarbazin do not interfere with recovery.

Liquid chromatographic determination of nicarbazin in feeds and premixes

A liquid chromatographic (LC) method has been developed for the determination of nicarbazin in premixes and poultry feed. Liquid chromatography of the 4,4'-dinitrocarbanilide (DNC) portion of nicarbazin is performed isocratically with a reverse phase octadecylsilica column and a UV detector set at 340 nm. The 2-hydroxy-4,6-dimethylpyrimidine (HDP) portion of nicarbazin is chromatographed isocratically with a reverse phase octylsilica column and a UV detector set at 305 nm. Nicarbazin concentration can be calculated by assaying both DNC and HDP, or by assaying DNC or HDP and assuming that nicarbazin is a 1:1 molar ratio of the two. Average recoveries of DNC and HDP added to poultry feed were 101% and 87%, respectively. This procedure provides an alternative to existing colorimetric procedures for determining nicarbazin in premixes and poultry feeds.