Liquid chromatographic determination of lasalocid sodium in chicken skin: interlaboratory study

The U.S. Food and Drug Administration (FDA) sponsored an interlaboratory study of a liquid chromatographic determinative procedure for lasalocid sodium in chicken skin with adhering fat. Four laboratories analyzed 35 dosed tissue samples and 82 fortified tissue samples containing lasalocid at levels ranging from 0.1 to 0.6 ppm. Samples were homogenized with acetonitrile, washed with hexane, and partitioned into the mobile phase prior to analysis liquid chromatography with fluorescence detection. The results of the interlaboratory study showed good reproducibility for fortified samples. Fortification levels, average recoveries, and interlaboratory percent coefficients of variation were as follows: 0.6 ppm, 0.57 ppm, and 9.7; 0.3 ppm, 0.25 ppm, and 9.1; and 0.15 ppm, 0.14 ppm, and 7.0, respectively. Data for analysis of the dosed tissue also showed good agreement among the laboratories.     

Liquid chromatographic determination of rotenone in fish, crayfish, mussels, and sediments

An analytical procedure is described for determining residues of rotenone in fish muscle, fish offal, crayfish, freshwater mussels, and bottom sediments. Tissue samples were extracted with ethyl ether and extracts were cleaned up by gel permeation chromatography and silica gel chromatography. Sediment samples were extracted with methanol, acidified, partitioned into hexane, and cleaned up on a silica gel column. Rotenone residues were quantitated by liquid chromatography, using ultraviolet (295 nm) detection. Recoveries from sediment samples fortified with rotenone at 0.3 microgram/g were 80.8%, whereas recoveries from tissue samples fortified with 0.1 microgram/g ranged from 87.7 to 96.8%. Samples fortified with 0.3 microgram/g and stored at -10 degrees C for 6 months before analysis had recoveries ranging from 83.2 to 90.5%. Limits of detection were 0.025 microgram/g for sediments and 0.005 microgram/g for tissue samples.     

Extraction and cleanup procedures for determination of diarylphosphates in fish, sediment, and water samples

Methods for determination of triaryl/alkylphosphates (TAPs) in water, fish, and sediment have been extended to determination of the diarylphosphate (DAP) degradation products. DAPs were extracted from water (adjusted to pH 0.5) by use of XAD-2 resin and determined by gas-liquid chromatography as butyl esters. Recovery of diphenylphosphate (DPP) and o-, m-, p-dicresylphosphates (DoCP, DmCP, DpCP) were greater than 95% in water samples fortified at 1, 10, and 50 micrograms/L. DAPs were extracted from fish with methanol and the extracts were cleaned up on reverse phase (C18) silica cartridges. Recoveries were greater than 87% for DPP, DoCP, DmCP, and DpCP in fish muscle fortified at 50, 100, and 500 ng/g. Sediments were refluxed with aqueous methanol and DAPs were recovered by use of XAD-2 resin. Recoveries of DAPs from sediments fortified at 50 and 100 ng/g were greater than 76%. Interferences (1-10 ng/g) from phosphorus or nitrogen-containing GLC peaks prevented sub- ng/g level analysis for DAPs in sediment and fish extracts.     

Reduction of mercury pollution in the vicinity of a caustic soda plant in Thailand

Fish samples collected near the caustic soda factory of TACSCO in Thailand during November and December 1978 were found to contain 0.10 to 1.38 ppm Hg in flesh (on wet weight basis), whereas those of the control areas contained 0.01 to 0.30 ppm. The Hg content of the fish in the TACSCO area had decreased by more than half from the first investigation which took place during 1975–76. This decrease is obviously a result of the functioning of the waste-water-treatment system built by the factory in 1974. The bottom mud collected near the factory in 1978 contained 8.39 to 57.95 ppm Hg (on dry weight basis) as compared with the mean of 0.03 ppm in samples taken from the control area. The Hg content in fish-eating birds were low, 0.04 to 0.44 ppm in the muscles and 0.05 to 1.32 ppm in the livers (on wet weight basis).     

Liquid chromatographic determination of zoalene and its metabolites in chicken tissues with electrochemical detection

A procedure is described for the quantitation of Zoalene (3,5-dinitro-o-toluamide) and its 2 major monoamino metabolites in chicken tissues. The method includes blender extraction of tissue with chloroformethyl acetate (1 + 1), adsorption of the drug and metabolites on neutral alumina, and subsequent elution of the residues with pH 3.5 formate buffer-methanol (6.5 + 3.5). Recovered residues were separated on a 5 micron C18 column with the alumina eluting solvent as the LC mobile phase. The parent drug and metabolites were detected and quantitated with an electrochemical detector in the reductive mode with a minimum level of reliable measurement of 0.1 ppm. Overall mean recoveries greater than 85% were obtained with Zoalene and its 2 monoamino metabolites in breast, thigh, and liver tissues fortified with 0.25-2.00 ppm. The results on tissues from chickens fed a diet containing 0.0125% Zoalene are presented.     

Determination of chlorinated methylthiobenzenes and their sulfoxides and sulfones in fish

A procedure was developed to determine chlorinated methylthiobenzenes and their respective sulfur oxidation products in fish. Perch samples fortified at the 0.1 ppm level with 2,4,5-trichloromethylthiobenzene, pentachloromethylthiobenzene, and their sulfoxides and sulfones were extracted and cleaned up using an adaptation of the official AOAC method for multiple residues of organochlorine pesticides. The Florisil column cleanup was modified; 200 mL 6% petroleum etherethyl ether eluted the methylthiobenzenes, 200 mL 50% PE-EE eluted the sulfones, and 200 mL EE eluted the sulfoxides. Recoveries determined by electron capture (ECD) gas chromatography (GC) were 75-101% for the methylthiobenzenes and their sulfones and 63-93% for the sulfoxides. Co-extracted materials in the Florisil eluates that interfered with the ECD/GC quantitation were removed by partitioning the sulfoxides and sulfones into sulfuric acid and by thin layer chromatography on silica gel, using methylene chloride-hexane (50 + 50) as the developing solvent. Seven fish samples containing residues of chlorinated benzenes or polychlorinated biphenyls (PCBs) were examined for chlorinated methylthiobenzenes, methylthio-PCBs, and their oxidation products by matching GC retention times obtained with the EC detector and a flame photometric detector operated in the sulfur mode. These analytes were not found in the fish samples above a detection level equivalent to 0.02 ppm 2,4,5-trichloromethylthiobenzene.     

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.     

Improved cleanup technique for the estimation of endosulfan and endrin residues.

An improved cleanup technique has been developed for the extraction of endosulfan and endrin from crops. The technique involves the use of Nuchar C-190N as adsorbent and a mixture of n-hexane and acetone (4+1) as the eluting solvent. The mean percentage recoveries of endosulfan (I and II) and endrin from plant tissue extracts fortified at levels of 0.5-2.0 ppm varied from 86 to 102 and 97 to 100, respectively.     

Colorimetric determination of boric acid in prawns, shrimp, and salted jelly fish by chelate extraction with 2-ethyl-1,3-hexanediol.

Borate was directly chelate-extracted from foods with 5% 2-ethyl-1,3-hexanediol (EHD) in n-hexane-n-butyl acetate mixture (8 + 2), from which borate was selectively transferred into 1% NaOH, since EHD-chelated boron did not react with curcumin to develop color. Finally, an aliquot of the alkaline solution was acidified with HCl and reacted with curcumin in a rotary evaporator. Color development was increased by heating for 8 min at 80 degrees C under reduced pressure of 16 mm Hg. Frozen shrimp and prawns (peeled and with shells) and salted jelly fish were analyzed by the proposed method. Results were compared with the contemporary official method of Japan based on curcumin reaction on an incinerated sample. Over 90% of the boric acid was recovered by the proposed method when samples were fortified with 20 ppm boric acid. Recoveries were superior to those of the official method especially for shrimp and prawns with shells and salted jelly fish. Detection limit of boric acid is 1 ppm. Moreover, the method requires only about 1 hr for analysis of one sample, making it suitable for routine analysis.     

Simplified micro perchlorination method for polychlorinated biphenyls in biological samples.

Simplified methodology is presented for the micro determination of polychlorinated biphenyls (PCBs) in biological samples, by conversion to the decachlorobiphenyl (DCB) derivative. Beef adipose tissue and human milk extracts were fortified with PCB standards at 0.1--5.0 ppm, and perchlorinated with antimony pentachloride (SbCl5). Several Aroclors representing various degrees of chlorine content were investigated to assess the efficiency of conversion to DCB. Samples were cleaned up on a Florisil mini column and the PCBs were quantitated by electron capture GLC. Several chlorinated pesticides which were subjected to the perchlorination procedure did not interfere. As little as 0.1 ppm PCBs in 500 mg tissue extract can be recovered at 79-99%. The background DCB content of several brands of SbCl5 was determined. The levels of PCBs in human milk obtained by the perchlorination technique are compared with data acquired by electron capture gas-liquid chromatography in which the individual chlorobiphenyls in the sample are measured.     

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.     

Determination of niclosamide residues in rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) fillet tissue by high-performance liquid chromatography

Bayluscide [the ethanolamine salt of niclosamide (NIC)] is a registered piscicide used in combination with 3-(trifluoromethyl)-4-nitrophenol (TFM) to control sea lamprey populations in streams tributary to the Great Lakes. A high-performance liquid chromatography (HPLC) method was developed for the determination of NIC residues in muscle fillet tissues of fish exposed to NIC and TFM during sea lamprey control treatments. NIC was extracted from fortified channel catfish and rainbow trout fillet tissue with a series of acetone extractions and cleaned up on C(18) solid-phase extraction cartridges. NIC concentrations were determined by HPLC with detection at 360 and 335 nm for rainbow trout and catfish, respectively. Recovery of NIC from rainbow trout (n = 7) fortified at 0.04 microg/g was 77 +/- 6.5% and from channel catfish (n = 7) fortified at 0.02 microg/g was 113 +/- 11%. NIC detection limit was 0.0107 microg/g for rainbow trout and 0.0063 microg/g for catfish. Percent recovery of incurred radioactive residues by this method from catfish exposed to [(14)C]NIC was 89.3 +/- 4.1%. Percent recoveries of NIC from fortified storage stability tissue samples for rainbow trout (n = 3) analyzed at 5 and 7.5 month periods were 78 +/- 5.1 and 68 +/- 2.4%, respectively. Percent recoveries of NIC from fortified storage stability tissue samples for channel catfish (n = 3) analyzed at 5 and 7.5 month periods were 88 +/- 13 and 76 +/- 21%, respectively.     

Validation of a method for determination of tetracycline antibiotics in salmon muscle tissue

A method was validated for analysis of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in fortified salmon muscle tissue. Recoveries of OTC were 100 +/- 6, 86 +/- 6, and 82 +/- 5% (n = 6) at fortification levels of 1.0, 0.5, and 0.2 ppm, respectively. Recoveries of TC were 68 +/- 4, 65 +/- 6, and 66 +/- 7%; recoveries of CTC were 45 +/- 9, 48 +/- 8, and 0%, respectively. Detection limits for OTC and TC were 0.08 and 0.09 ppm, respectively.     

Relationship of carotenoids and tocopherols in a sample of carrot root-color accessions and carrot germplasm carrying Rp and rp alleles

Carotenoids and tocopherols are powerful antioxidants synthesized in plants from a common precursor. They may offer significant health benefits to humans. Seed oils have been shown to possess high levels of tocopherols, but little is known about their levels in the edible portions of most vegetable crops. A two-year field experiment was conducted at two locations to assess levels of major carotenoids and tocopherols in carrot (Daucus carota) root and leaf tissue. Levels of compounds in root tissue reported on a dry weight basis were as follows: alpha-tocopherol, 0.04-0.18 ppm; lycopene, 0.00-52.94 ppm; alpha-carotene, 10.63-1504.76 ppm; and beta-carotene, 26.69-1673.76 ppm. Higher levels of all carotenoids were measured in phloem tissue than in xylem. Leaf tissue levels of tocopherols measured on a dry weight basis ranged from 0.02 to 0.85 ppm, whereas levels of carotenoids ranged from 12.81 to 411.66 ppm. In xylem tissue, alpha-tocopherol was significantly (P < or =0.001) positively correlated with alpha-carotene (r = 0.65) and with beta-carotene (r = 0.52). This positive correlation indicates it may be possible to select for both increased alpha-tocopherol and carotenoids in carrot. The reduced pigment (rp) mutation of carrot exhibited a 96% reduction in levels of alpha- and beta-carotene and a 25-43% reduction in alpha-tocopherol when compared to a near-isogenic line. In plants homozygous for rp, a substantial increase was observed in phytoene, a precursor to carotenoids, suggesting the location of the rp lesion in the carotenoid synthesis pathway.     

Gas chromatographic method for determination of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol (TCP) in dates.

A method is described for the determination of the insecticide chlorpyrifos and its metabolite TCP in green, unprocessed, and processed dates with the seeds incorporated. After extraction, chloropyrifos is cleaned up using Florisil and analyzed using a gas chromatography (GC) equipped with a nitrogen/phosphorus detector. TCP is derivatized using bis-(trimethylsilyl)-acetamide (BSA) to form the TCP-derivative and analyzed by a gas chromatograph equipped with a Hall electrolytic conductivity detector. Recoveries of chlorpyrifos from all fortified dates (0.05 and 0.1 ppm) ranged from 86 to 110% with an average of 94.5%. Recoveries of TCP from all fortified dates (0.1 and 0.2 ppm) ranged from 79 to 99% with an average of 86%. Limits of detection for chlorpyrifos and TCP in green, unprocessed, and processed dates were 0.02 and 0.05 ppm, respectively.     

The Luke et al. method for determining multipesticide residues in fruits and vegetables: collaborative study

Ten laboratories analyzed unfortified and fortified samples of lettuce, tomatoes, and strawberries for organochlorine and organophosphorus pesticides by applicable portions of the comprehensive multipesticide method of Luke et al. The 3 crops were fortified with 6 pesticides, alpha-BHC, dieldrin, chlorpyrifos, acephate, omethoate, and monocrotophos, each at 3 levels per crop. Included in the 54 fortifications were 16 pairs of blind duplicates: same pesticide, crop, and level. Recoveries were calculated by area comparisons with known reference materials, using the responses obtained from 2 separate element-specific gas chromatographic (GC) systems. The organochlorine pesticides were chromatographed on a methyl silicone column and detected with a Hall 700A electrolytic conductivity detector, and the organophosphorus pesticides were determined with a flame photometric detector after being chromatographed on a specified DEGS column material. Chlorpyrifos was quantitated on both GC systems. Mean recoveries ranged from 82.6% for acephate fortified at 0.5000 ppm in strawberries to 118.1% for 0.0636 ppm fortification of chlorpyrifos in lettuce. Interlaboratory coefficients of variation ranged from 4.0% for 0.6360 ppm fortification of chlorpyrifos in tomatoes to 17.8% for the 0.0636 ppm chlorpyrifos level in lettuce. The procedure features essentially no cleanup before GC and proved comparable to existing multiresidue methods for pesticides of the class types studied, as evidenced by the intra- and interlaboratory measurements of precision and recoveries obtained. The method with the 2 GC systems has been adopted official first action.     

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.     

Determination of 4,4'-dinitrocarbanilide (DNC), the active component of the antifertility agent nicarbazin, in chicken, duck, and goose plasma

4,4'-Dinitrocarbanilide (DNC) was extracted from chicken, duck, and goose plasma and isolated by reversed-phase high-performance liquid chromatography. DNC was detected by ultraviolet absorbance at 347 nm and quantified by comparison to a calibration standard. Recovery data were determined by analyzing DNC-fortified control plasma. The mean recovery of DNC in fortified chicken plasma samples was 99.7 +/- 1.9% for 0.18 and 9.1 ppm DNC, and in fortified duck and goose plasma samples was 99.5 +/- 4.9% and 101.4 +/- 4.5%, respectively, for 0.18, 9.1, and 18 ppm DNC.     

Matrix solid phase dispersion isolation and liquid chromatographic determination of sulfadimethoxine in catfish (Ictalurus punctatus) muscle tissue

A method for the isolation and liquid chromatographic determination of sulfadimethoxine in catfish (Ictalurus punctatus) muscle tissue is presented. Blank control and sulfadimethoxine-fortified fish muscle tissue samples (0.5 g) were blended with octadecyisilyl (C18, 40 micrograms, 18% load, endcapped) derivatized silica packing material. A column made from the C18/fish tissue blend was first washed with hexane (8 mL), following which the sulfadimethoxine was eluted with dichloromethane (8 mL). The eluant contained sulfadimethoxine analyte that was free from interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array, 270 nm). Standard curves for sulfadimethoxine isolated from fortified samples were linear (0.999 +/- 0.001) with an average relative percentage recovery of 101.1 +/- 4.2% for the concentration range (50, 100, 200, 400, 800, and 1600 ng/g) examined using sulfamethoxazole as the internal standard. The interassay variability was 10.7 +/- 8.2% with an intra-assay variability of 2.2%.     

Determination of polybrominated biphenyl residues in dairy products.

A method for the determination of polybrominated biphenyls (PBBs) in dairy products is described. Fat is extracted from the products by the official AOAC method. The PBB residues are separated from the fatty material by gel permeation chromatography prior to gas-liquid chromatographic (GLC) quantitation. An additional cleanup using petroleum ether elution through a miniature Florisil column is necessary for thin layer chromatographic (TLC) confirmation. Recoveries of PBBs from samples fortified at levels from 0.1 to 0.5 ppm ranged from 94 to 104% with an average of 99%. GLC sensitivity permits the estimation of PBB residue levels as low as 0.007 ppm. Routine TLC confirmation is limited by sensitivity to greater than or equal to 0.2 ppm.