Determination of desaminosulfamethazine, sulfamethazine, and N4-acetylsulfamethazine by gas chromatography with electron capture detection and confirmation by gas chromatography-chemical ionization mass spectrometry

An electron capture gas chromatographic method for the determination of sulfamethazine was modified to separate and quantitate simultaneously sulfamethazine and 2 of its metabolites, N4-acetylsulfamethazine and desaminosulfamethazine. The modified method was applied to incurred residues in a veal calf depletion study and to incurred residues in swine tissues. With capillary column gas chromatography-positive ion chemical ionization mass spectrometry, confirmation of the identities of incurred desaminosulfamethazine, N4-acetylsulfamethazine, and sulfamethazine in tissues was obtained from a single injection.     

Confirmation of levamisole residues in cattle and swine livers by capillary gas chromatography-electron impact mass spectrometry

Capillary gas chromatography-electron impact mass spectrometry is used to confirm the presence of levamisole in cattle and swine livers at the 0.1 ppm tolerance level. Use of a fused silica capillary column from injector to detector solved chromatographic problems encountered with the analyte. Of the mass spectrometric techniques evaluated, electron impact mass spectrometry provided the most satisfactory data for a confirmatory method. Recoveries from swine and cattle livers fortified at 0.1 ppm averaged 74.9 and 72.7%, respectively, indicating potential utility of this methodology as a quantitative method. Apparent levamisole residues in control livers were less than 0.01 ppm.     

Confirmation of phorate, terbufos, and their sulfoxides and sulfones in water by capillary gas chromatography/chemical ionization mass spectrometry

A gas chromatographic/mass spectrometric method capable of confirming phorate, terbufos, their sulfoxides, and sulfones in water is reported. Parents and their metabolites are separated in less than 5 min using a short capillary GC column and high carrier gas linear velocities. Positive ion chemical ionization mass spectrometry generates (M + H) ions indicative of the different molecular weights of the analytes and at least one confirmatory fragment ion for each analyte. Residues have been qualitatively confirmed at the 1 ppb level in fortified water samples from a variety of sources. Apparent residues in control water were less than 0.1 ppb.     

Determination of pyrantel in swine liver by flame ionization gas chromatography and confirmation by gas chromatography/mass spectrometry

During an evaluation of the gas chromatography/mass spectrometry (GC/MS) confirmatory procedure of Lynch and Bartolucci for pyrantel residues in swine tissues, we developed a GC flame ionization method for quantitating pyrantel residues in extracts of swine liver. The method was subjected to trial principally in the laboratories of Biospherics, Inc., using control liver, fortified control liver, and incurred liver tissue samples. Although the method does not meet all of the current Food and Drug Administration criteria, it compares favorably to the official determinative method. Portions of the same extract can be used for quantitation and for GC/MS confirmation, true recoveries appear to be slightly higher, and an internal standard is not required. The precision of this method equals or exceeds that of the official determinative method.     

Quantitative gas chromatographic-mass spectrometric assay of five sulfonamide residues in animal tissue

A gas chromatographic-mass spectrometric procedure using isotopically labeled internal standards and the technique of selective-ion monitoring was used to assay sulfamethazine, sulfadimethoxine, sulfabromethazine, sulfathiazole, and sulfaquinoxaline in liver and muscle tissue of swine, poultry, and cattle. The data presented clearly demonstrate the applicability of this procedure for confirmation of sulfonamide residues in animal tissue.     

Determination of tetracycline antibiotic residues in edible swine tissues by liquid chromatography with spectrofluorometric detection and confirmation by mass spectrometry

A sensitive and specific method is described for the simultaneous determination of oxytetracycline, tetracycline (TC), and chlortetracycline residues in edible swine tissues, by combining liquid chromatography with spectrofluorometric and mass spectrometry detection. The procedure involved a preliminary extraction with EDTA-McIlvaine buffer acidified at pH 4.0, followed by solid-phase extraction cleanup using a polymeric sorbent. The liquid chromatography analysis was performed with spectrofluorometric detection after postcolumn derivatization with magnesium ions. The limits of quantification were 50 microg/kg for muscle and 100 microg/kg for kidney tissues. The recovery values were greater than 77.8% for muscle and 65.1% for kidney. The method has been successfully used for the quantification of tetracyclines in swine tissues samples. The selective liquid chromatography mass spectrometric analysis for confirmation of oxytetracycline in one positive swine muscle sample was made by atmospheric pressure chemical ionization (APCI). The APCI mass spectra of the TCs gave the protonated molecular ion and two typical fragment ions, required for their confirmation in single ion monitoring scan mode in animal tissues.     

Determination of daminozide in apples by gas chromatography/chemical ionization mass spectrometry

A method using gas chromatography/chemical ionization mass spectrometry (GC/CIMS) for the determination of daminozide residues in apples has been developed. Daminozide was separated from the sample matrix by water extraction and cation exchange, converted to the methyl ester by treatment with HCl-methanol, and determined by GC/CIMS using succinonitrile as an internal standard. The detection level was 0.05 ppm. Recoveries were 92-104% from apples spiked at the 0.05-0.5 ppm levels. Of the 25 apple samples analyzed, only 2 were positive for daminozide (1.04 and 0.32 ppm).     

Residue methodology for AMDRO fire ant insecticide (AC 217,300) in pasture grass and crops

Residue methodology is described for the determination of AC 217,300 residues in pasture grass and crop samples. After extraction and subsequent cleanup on an XAD-2 column, residues of AC 217,300 are determined by liquid chromatography (LC), using a reverse phase paired-ion chromatographic system and detection at 300 nm. The method has a validated limit of sensitivity of 0.05 ppm with corresponding control values for the commodities analyzed of less than 0.01 ppm. Apparent residues over 0.05 ppm can be confirmed by either gas chromatography with an electron capture detector (GC-EC) or gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICI). The direct GC-NICI method circumvents the need for sample cleanup on the XAD-2 column, and offers a greatly simplified procedure that is useful for screening samples. Recoveries of AC 217,300 from the commodities analyzed have been satisfactory with all methods of analysis.     

Quantitative confirmation of dimetridazole and ipronidazole in swine feed by capillary gas chromatography/mass spectrometry with multiple ion detection

Extracts from 4 types of swine feed containing 0.11 ppm each of dimetridazole (DMZ) and ipronidazole (IPR) were analyzed by capillary gas chromatography/mass spectrometry (GC/MS) using multiple ion detection (MID) techniques. We demonstrate in this paper that the quantitative results obtained by capillary GC/MS with MID are comparable for both compounds to results obtained by liquid chromatography and have a lower coefficient of variation for DMZ. Moreover, consistency in the ion ratios (5 ions in DMZ and 6 ions in IPR) permits identification of these compounds by electron ionization MS.     

Determination and confirmation of melamine residues in catfish, trout, tilapia, salmon, and shrimp by liquid chromatography with tandem mass spectrometry

Pet and food animal (hogs, chicken, and fish) feeds were recently found to be contaminated with melamine (MEL). A quantitative and confirmatory method is presented to determine MEL residues in edible tissues from fish fed this contaminant. Edible tissues were extracted with acidic acetonitrile, defatted with dichloromethane, and cleaned up using mixed-mode cation exchange solid-phase extraction cartridges. Extracts were analyzed by liquid chromatography with tandem mass spectrometry with hydrophilic interaction chromatography and electrospray ionization in positive ion mode. Fish and shrimp tissues were fortified with 10-500 microg/kg (ppb) of MEL with an average recovery of 63.8% (21.5% relative standard deviation, n = 121). Incurred fish tissues were generated by feeding fish up to 400 mg/kg of MEL or a combination of MEL and the related triazine cyanuric acid (CYA). MEL and CYA are known to form an insoluble complex in the kidneys, which may lead to renal failure. Fifty-five treated catfish, trout, tilapia, and salmon were analyzed after withdrawal times of 1-14 days. MEL residues were found in edible tissues from all of the fish with concentrations ranging from 0.011 to 210 mg/kg (ppm). Incurred shrimp and a survey of market seafood products were also analyzed as part of this study.     

Evidence for transformation of sulfamethazine to its N4-glucopyranosyl derivative in swine liver during frozen storage

An analytical procedure for determining N4-glucopyranosylsulfamethazine (GPS) in swine livers is described. The sulfamethazine derivative is extracted from the tissues with water. GPS is isolated in sufficient purity for liquid chromatographic determination by a series of adsorption chromatographic procedures. Recovery of the conjugate from spiked swine livers was 82.2% with a coefficient of variation of 4.5%. Evidence is presented suggesting that sulfamethazine in swine livers is transformed to GPS during frozen storage. Two samples of swine liver in which incurred sulfamethazine residues were substantially depleted during frozen storage were analyzed for GPS. The conjugate accounted for 96.2% and 92.2% of the depleted sulfamethazine residues.     

Gas chromatographic-mass spectrometric detection and quantitation of lincomycin in animal feedingstuffs

A substantially improved assay was developed for lincomycin A in animal feedingstuffs. The assay allows unambiguous quantitation of at least 0.1 ppm in feed. Lincomycin B did not interfere because of differences in both retention time and mass of the main fragment ion in electron impact (EI) spectra. The assay using single ion monitoring with EI detection would not discriminate between lincomycin A and clindamycin. The presence of the latter was easily confirmed by using gas chromatography-mass spectrometry in the chemical ionization mode. The assay for lincomycin A was linear in the range 0-40 ng applied to the gas chromatographic column. The recovery was 93.4 +/- 4.2% at 1 and 5 ppm and 86.2 +/- 5.5% at 0.1 ppm in feed. The coefficient of variation of the assay was 4.8% at both 1 and 5 ppm, and was 6.43% at 0.1 ppm.     

Determination of altosid insect growth regulator in waters, soils, plants, and animals by gas-liquid chromatography.

Residues of isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate (Altosid) insect growth regulator are determined in waters, soils, plants, milk, eggs, fish, shellfish, poultry and cattle tissues, blood, urine, and feces. Acetonitrile is the primary extraction solvent for all samples. Residues are extracted by high-speed blending followed by vacuum filtration. Fatty extracts are subjected to cold-temperature precipitation and filtration. Samples are cleaned up by petroleum ether partitioning and Florisil and neutral alumina chromatography. The concentrated eluants are analyzed by gas-liquid chromatography (GLC) on columns of differing polarity, using hydrogen flame ionization detectors. The identity of suspected residues is confirmed by additional GLC and by mass fragmentography. The lower limits of detection were: water samples, 0.0004-0.001 ppm; soils, blood, and urine, 0.001 ppm; forage grasses, forage legumes, and rice foliage, 0.005 ppm; and milk, eggs, fish, shellfish, poultry and cattle tissues, and feces, 0.010 ppm.     

Methods for determination of ionophore-type antibiotic residues in animal tissues

Methods for the analysis of polyether antibiotics in animal tissues and fluids are described. For monensin and nigericin, only methods based on bioautography are available. For lasalocid, in addition to TLC bioautography for quantitation in chicken skin and fat, LC methods based on fluorescence detection have been developed for quantitation in animal blood, milk, liver, skin, and fat. In addition, a confirmatory method for lasalocid is described; this is based on purification by LC followed by silylation and pyrolysis gas chromatography-positive chemical ionization mass spectrometry.     

Determination and confirmation of nitrofuran residues in honey using LC-MS/MS

A method was developed for the determination and confirmation of furazolidone, nitrofurazone, furaltadone, and nitrofurantoin as their side-chain residues in honey using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An initial solid-phase extraction cleanup of the honey samples was followed by overnight hydrolysis and derivatization of the nitrofuran side-chain residues with 2-nitrobenzaldehyde. After pH adjustment and liquid-liquid extraction, the extracts were assayed by LC-MS/MS using electrospray ionization in the positive ion mode. The method was validated at concentrations ranging from 0.5 to 2.0 ppb with accuracies of 92-103% and coefficients of variation of < or =10%. The lowest calibration standard used (0.25 ppb) was defined as the limit of quantitation for all four nitrofuran side-chain residues. The extracts and standards were also used for confirmatory purposes. Honey from dosed beehives was assayed to study the stability of the nitrofuran residues and to demonstrate the effectiveness of the method.     

Quantitation and confirmation of sulfamethazine residues in swine muscle and liver by LC and GC/MS

The present paper describes a liquid chromatographic (LC) method for purification of crude swine tissue extracts before gas chromatographic/mass spectrometric (GC/MS) quantitation and confirmation of sulfamethazine at low ppb levels. Fractions corresponding to sulfamethazine were collected, evaporated to dryness, N-methylated with diazomethane, concentrated, and analyzed by GC/MS. A mass spectrometer was set to selected ion monitoring (SIM) mode. Ions 233, 227, 228, and 92 m/z were detected. Ratio 227/233 m/z (sulfamethazine/internal standard, [phenyl 13C6] sulfamethazine) was used for quantitation, while ratios 228/227 and 92/227 m/z, respectively, were used for confirmation. Quantitation in spiked blank muscle tissue was tested from 100 to 1 ppb and found acceptable at all concentrations studied; coefficients of variations ranged from 4.9 to 14.4%. Similar results were obtained for liver tissue from 5 to 20 ppb; coefficients of variation ranged from 1.2 to 9.1%.     

Determination of linuron in potatoes using capillary column gas chromatography/mass spectrometry

A convenient method for the determination of the N-methyl,N-methoxy-phenylurea herbicide (linuron) in potatoes has been developed. The herbicide is extracted from potatoes using a slightly modified Luke multiresidue procedure. The extract is analyzed directly by gas chromatography with cold on-column injection, using an ion trap mass spectrometer in the chemical ionization mode as the detector. Quantitation is performed using p-bromonitrobenzene as the internal standard. The limit of detection is 0.1 ppm. Recoveries of linuron in potatoes averaged 112 +/- 6% at the 0.5 ppm level, and 110 +/- 2% at the 0.2 ppm level. No linuron residues were found in 25 potato samples that were analyzed by this method. Two other N-methyl,N-methoxy-phenylurea herbicides, metobromuron and chlorbromuron, are also sufficiently stable to be determined by this method, but the N,N-dialkyl-phenylurea herbicides neburon, diuron, and monuron are too thermally unstable and degrade in the gas chromatograph.     

Quantitative and confirmatory analyses of malachite green and leucomalachite green residues in fish and shrimp

Liquid chromatographic methods are presented for the quantitative and confirmatory determination of malachite green (MG) and leucomalachite green (LMG) for channel catfish, rainbow trout, tilapia, basa, Atlantic salmon, and tiger shrimp. Residues were extracted from tissues with ammonium acetate buffer and acetonitrile and isolated by partitioning into dichloromethane. LMG was quantitatively oxidized to the chromic MG with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Extracts were analyzed for total MG by liquid chromatography with both visible detection (LC-VIS) at 618 nm for routine screening and ion trap mass spectrometry (LC-MSn) with no discharge-atmospheric pressure chemical ionization for residue confirmation. The method was validated in each species fortified with LMG at 1, 2, 4, and 10 ng/g (ppb), and average recoveries ranged from 85.9 to 93.9%. Quantitative data were consistent for the two detection methods, with measured method detection limits of 1.0 ng/g for LC-VIS and 0.25 ng/g for LC-MSn. Incurred tissues from catfish, trout, tilapia, and salmon that had been treated with MG were also extracted and analyzed as part of this study.     

Tissue distribution, elimination, and metabolism of dietary sodium [36Cl]chlorate in beef cattle

Two steers (approximately 195 kg) were each dosed with 62.5 or 130.6 mg/kg body weight sodium [36Cl]chlorate for three consecutive days. All excreta were collected during the dosing and 8 h withdrawal periods. The apparent radiochlorine absorption was 62-68% of the total dose with the major excretory route being urine. Parent chlorate was 65-100% of the urinary radiochlorine; chloride was the only other radiochlorine species present. Similarly, residues in edible tissues were composed of chloride and chlorate with chloride being the major radiolabeled species present. Chlorate represented 28-57% of the total radioactive residues in skeletal muscle; in liver, kidney, and adipose tissues, chlorate ion represented a smaller percentage of the total residues. Chlorate residues in the low dose steer were 26 ppm in kidney, 14 ppm in skeletal muscle, 2.0 ppm in adipose tissue, and 0.7 ppm in liver. These data indicate that sodium chlorate may be a viable preharvest food safety tool for use by the cattle industry.     

Gas-liquid chromatographic determination of famphur and its oxygen analog in tissues of reindeer and cattle.

A gas chromatography equipped with a flame photometric detector operating in the phosphorus mode provided a sensitive method for determining residues of famphur, O,O-dimethyl O-[p-(dimethylsulfamoyl)phenyl]phosphorothioate, and its oxygen analog in reindeer and cattle tissues. With extraction and cleanup, 0.025 ppm famphur and 0.06 ppm oxygen analog could be detected in the body tissues. Recoveries of 73-100% were obtained from fat, muscle, liver, and kidney.