Analysis of veterinary drugs and metabolites in milk using quadrupole time-of-flight liquid chromatography-mass spectrometry.

A quadrupole time-of-flight (Q-TOF) liquid chromatography-mass spectrometry (LC-MS) method was developed to analyze veterinary drug residues in milk. Milk samples were extracted with acetonitrile. A molecular weight cutoff filter was the only cleanup step in the procedure.

Bioaccumulation of cyanuric acid in edible tissues of shrimp following experimental feeding.

Due to concerns that cyanuric acid (CYA)-contaminated feed had been used in aquaculture and could enter the human food chain, a method to quantify CYA residues in the edible tissues of fish and shrimp was previously developed and validated. This paper provides further data on the deliberate feeding of CYA to shrimp to determine the extent of residue accumulation in edible tissue. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed for the analysis of CYA in shrimp tissue.

Analysis of aminoglycoside residues in bovine milk by liquid chromatography electrospray ion trap mass spectrometry after derivatization with phenyl isocyanate.

A derivatization procedure using phenyl isocyanate was adapted to liquid chromatography ion trap mass spectrometry (LC-MS(n)) for confirmation and quantification of aminoglycoside residues in milk. Aminoglycoside residues were extracted from milk with acid and isolated from the matrix with a weak cation exchange solid-phase extraction cartridge. After isolating the compounds from the milk, derivatives of gentamicin, neomycin, and tobramycin were formed by reacting the drugs with phenyl isocyanate in the presence of triethylamine.

Multiresidue method for the triphenylmethane dyes in fish: Malachite green, crystal (gentian) violet, and brilliant green.

Liquid chromatographic methods are presented for the quantitative and confirmatory determination of crystal violet (CV; also known as gentian violet), leucocrystal violet (LCV), brilliant green (BG), and leucobrilliant green (LBG) in catfish. LCV and LBG were oxidized to the chromic CV and BG by reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, and residues were measured as the combined CV+/-LCV and BG+/-LBG. These methods are extensions of published methods for malachite green (MG) analysis to allow simultaneous determination of MG, CV, and BG.

Determination of cyanuric acid residues in catfish, trout, tilapia, salmon and shrimp by liquid chromatography-tandem mass spectrometry.

In May 2007, investigators discovered that waste material from the pet food manufacturing process contaminated with melamine (MEL) and/or cyanuric acid (CYA) had been added to hog and chicken feeds. At this time, investigators also learned that adulterated wheat gluten had been used in the manufacture of aquaculture feeds. Concern that the contaminated feed had been used in aquaculture and could enter the human food supply prompted the development of a method for the determination of CYA residues in the edible tissues of fish and shrimp.

Determination of oxytocin in a dilute IV solution by LC-MS(n).

The most common drug prescribed to induce labor in the United States is oxytocin, a peptide hormone composed of nine amino acids. Oxytocin is often reconstituted in intravenous (IV) saline solutions at less than 0.05 units ml(-1) (125 ng ml(-1)) to be delivered at 1-4 drops per minute.

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.

Multi-class, multi-residue liquid chromatography/tandem mass spectrometry screening and confirmation methods for drug residues in milk.

This paper describes the development and optimization of a multi-residue veterinary drug screening method for whole milk. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. Milk samples were extracted with acetonitrile and the samples were then subjected to a clean-up procedure using a bonded solid-phase extraction cartridge and a molecular weight cut-off filter.

Determination of quinolone residues in shrimp using liquid chromatography with fluorescence detection and residue confirmation by mass spectrometry.

The quinolones, oxolinic acid (OXO), flumequine (FLU), and nalidixic acid (NAL), are antibacterial drugs effective against gram-negative bacteria. Quinolones are used in both human and veterinary medicine, but are currently not approved by the U.S.

Confirmation of diminazene diaceturate in bovine plasma using electrospray liquid chromatography-mass spectrometry.

Diminazene diaceturate is used as a trypanocide for cattle in tropical regions. This paper describes a LC-MS(n) method to confirm the presence of diminazene in bovine plasma. Bound diminazene in plasma samples was freed with dilute phosphoric acid, then concentrated on a bonded C(18) SPE cartridge.

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.

No-discharge atmospheric pressure chemical ionization: evaluation and application to the analysis of animal drug residues in complex matrices.

Alternative ionization methods are increasingly being utilized to increase the versatility and selectivity of liquid chromatography/mass spectrometry (LC/MS). One such technique is the practice of using commercially available atmospheric pressure chemical ionization (APCI) sources with the corona discharge turned off, a process termed no-discharge APCI (ND-APCI). The relative LC/MS responses for several different classes of veterinary drugs were obtained by using ND-APCI, electrospray ionization (ESI), and APCI.

Determination and confirmation of malachite green and leucomalachite green residues in salmon using liquid chromatography/mass spectrometry with no-discharge atmospheric pressure chemical ionization.

A liquid chromatography/mass spectrometry (LC/MS) method was developed to quantitate and confirm residues of leucomalachite green (LMG) in salmon tissue after their conversion to chromic malachite green (MG) in the extraction process. The method uses no-discharge atmospheric pressure chemical ionization (APCI) in conjunction with an ion-trap instrument to generate product-ion spectra. In the sample preparation procedure, salmon tissue is extracted with acetonitrile/buffer, the LMG residue is partitioned into methylene chloride, the LMG is converted to MG using an organic oxidizing agent, and the MG is isolated on alumina/propylsulfonic acid solid-phase extraction cartridges.

Liquid chromatographic determination of malachite green and leucomalachite green (LMG) residues in salmon with in situ LMG oxidation.

A liquid chromatography (LC) method is presented for the quantitative determination of malachite green (MG) in salmon. MG and leucomalachite green (LMG) residues were extracted from salmon tissue with ammonium acetate buffer and acetonitrile, and then isolated by partitioning into dichloromethane. LMG was quantitatively oxidized to the chromic MG by reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

Liquid chromatographic determination of diminazene diaceturate (Berenil) in raw bovine milk.

A simple liquid chromatographic (LC) method is presented for the determination of diminazene (DZ) in raw bovine milk. DZ is extracted from raw milk by chilled aqueous centrifugation and is isolated from milk components on a cyano solid-phase extraction column. DZ is eluted by using a methanol-ion pairing reagent.

Determination of residues of azamethiphos in salmon tissue by liquid chromatography with fluorescence detection.

A liquid chromatographic (LC) method with fluorescence detection (FLD) is described for determining residues of the pesticide azamethiphos (AZA) in salmon tissue. The sample is extracted with ethyl acetate, centrifuged, dehydrated with anhydrous sodium sulfate, evaporated, reconstituted in water, and defatted with hexane. The aqueous phase is passed through a C18 solid-phase extraction (SPE) column.

Confirmation of avermectin residues in food matrices with negative-ion atmospheric pressure chemical ionization liquid chromatography/mass spectrometry.

A multi-residue LC/MS method has been developed to confirm avermectin drug residues in several food matrices. Ivermectin (IVR), doramectin (DOR), eprinomectin (EPR) and moxidectin (MOX) are confirmed using atmospheric pressure chemical ionization (APCI) with negative ion detection and selected ion monitoring of three to four ions for each compound. The drug residues are extracted from tissue or milk using previously published procedures.

Liquid chromatographic determination of flumequine, nalidixic acid, oxolinic acid, and piromidic acid residues in catfish (Ictalurus punctatus).

A peer-verified, liquid chromatographic (LC) method for simultaneous determination of residues of flumequine (FLU), nalidixic acid (NAL), oxolinic acid (OXO), and piromidic acid (PIR) in catfish muscle is presented. Sample workup involves homogenizing tissue with acetone, defatting with hexane, and extracting quinolones into chloroform. Sample is purified further by partitioning into base and then subsequently back-extracting into chloroform after acidifying the aqueous phase.

Simultaneous determination of chloramphenicol, florfenicol, and thiamphenicol residues in milk by gas chromatography with electron capture detection.

A gas chromatographic (GC) method is described for determining residues of chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) in raw milk, with meta-nitrochloramphenicol (mCAP) as internal standard. Milk is extracted with acetonitrile, centrifuged, evaporated, reconstituted in water, and passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with 60% methanol, and then the eluate is evaporated and derivatized with Sylon BFT ¿N,O-bis(trimethylsilyl)trifluoroacetamide [BSTFA]-trimethylchlorosilane [TMCS], 99 + 1¿.

Confirmation of fluoroquinolones in catfish muscle by electrospray liquid chromatography/mass spectrometry.

A multiresidue liquid chromatography/mass spectrometry (LC/MS) confirmation method for fluoroquinolones in catfish muscle was developed by using an electrospray interface. Residues of ciprofloxacin, enrofloxacin, sarafloxacin, and difloxacin were positively identified in catfish muscle fortified at 10-80 ppb as well as in incurred tissue. The extraction procedure is based on an LC method with fluorescence detection for determination of these compounds in catfish.

Determination off four fluoroquinolones in milk by liquid chromatography.

A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxacin (CIPRO), sarafloxacin (SARA), and difloxacin (DIFLX) in milk. The procedure consists of extraction of milk with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC analysis is performed by isocratic elution using an acetonitrile-2% acetic acid (15 + 85) mobile phase and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 450 nm, respectively.

Determination of methylene blue in channel catfish (Ictalurus punctatus) tissue by liquid chromatography with visible detection.

Methylene blue (MB) is a thiazine dye that, although not regulated for use with edible fish, may sometimes be used as a chemotherapeutic agent in the aquaculture industry. A liquid chromatographic (LC) method was developed for the determination of MB in fish muscle. MB was extracted from catfish tissue with an acetonitrile-acetate buffer solution containing hydroxylamine and toluenesulfonic acid, partitioned into methylene chloride, and cleaned up on alumina and carboxylic acid solid-phase extraction cartridges.

Determination and confirmation of identities of flumequine and nalidixic, oxolinic, and piromidic acids in salmon and shrimp.

A previously published liquid chromatographic (LC) method for determining residues of flumequine (FLU) and nalidixic (NAL), oxolinic (OXO), and piromidic (PIR) acids in catfish tissue was applied to salmon and shrimp muscle. Identities of all 4 residues in salmon and shrimp were confirmed by gas chromatography/mass spectrometry (GC/MS). The tissue is homogenized with acetone, the acetone extract is defatted with hexane, and the quinolones are extracted into chloroform.

Particle beam liquid chromatography-mass spectrometry of triphenylmethane dyes: application to confirmation of malachite green in incurred catfish tissue.

Eight triphenylmethane dyes (malachite green, leucomalachite green, gentian violet, leucogentian violet, brilliant green, pentamethyl gentian violet, N',N'-tetramethyl gentian violet and N',N"-tetramethyl gentian violet) have been characterized by particle beam liquid chromatography-mass spectrometry. The electron ionization spectra obtained of these dyes by this technique exhibit similar fragmentation, with the formation of phenyl and substituted phenyl radicals, and loss of alkyl groups from the amines. It was observed that the six cationic dyes are reduced in the mass spectrometer source to form the corresponding leuco compounds.

Determination of malachite green and its metabolite, leucomalachite green, in catfish (Ictalurus punctatus) tissue by liquid chromatography with visible detection.

To determine residues of malachite green (MG) and its metabolite, leucomalachite green (LMG), in catfish tissue, analytes are extracted with acetonitrile-buffer and the extract is partitioned into methylene chloride. Final cleanup and isolation are performed on neutral alumina solid-phase extraction (SPE) and propylsulfonic acid cation-exchange SPE columns before analysis by liquid chromatography with visible detection. PbO2 postcolumn oxidation is performed by isocratic elution with a buffered mobile phase from a cyano column.