Liquid chromatographic determination of ergot alkaloids in wheat

A method is described for the determination of individual ergot alkaloids in wheat. The sample is extracted with ethyl acetate-4% ammonium hydroxide (100 + 10), and the extract is cleaned up by liquid-liquid partition. The ergot alkaloids are resolved by liquid chromatography (LC), using a porous cross-linked polystyrene-divinylbenzene resin column and a mobile phase consisting of acetonitrile-0.05 M dibasic ammonium phosphate (55 + 45) buffered at pH 10.0. The ergot alkaloids ergonovine, ergonovinine, ergotamine, ergotaminine, alpha-ergocryptine, alpha-ergocryptinine, ergocristine, and ergocristinine are separated by LC and detected with a fluorescence detector. Recovery of ergot alkaloids added to wheat at levels of 16-760 ng/g averaged 85.6% with a coefficient of variation of 11.1%.     

Simultaneous assay for six alkaloids in opium, using high-performance liquid chromatography.

A method is described for the quantitative determination of morphine, codeine, cryptopine, thebaine, papaverine, and narcotine in opium by high-performance liquid chromatography. The alkaloids are isolated from a dilute acid extract by adsorption on an Amberlite XAD-2 resin column and eluted first with methanol and then with chloroform-methanol (3+1). After solvent removal by reduced pressure evaporation, the alkaloids are redissolved in chloroform-methanol (3+1). The sample solution, plus brucine as an internal standard, is injected onto a Corasil II column and eluted with hexane that is gradient programmed with a solution of chloroform-methanol-diethylamine (100+300+1). The absorbances of the separated alkaloids are continuously monitored at 254 nm, using a flow-through ultraviolet double-beam photometer.     

Liquid chromatographic identification of meats

Raw beef, pork, veal, lamb, chicken, turkey, and duck have been identified with a liquid chromatographic (LC) method. Meat samples are blended in water, and soluble proteins in the aqueous blends are separated by the LC method. Meat cuts and parts from same species had similar chromatographic profiles and differed only quantitatively. However, meat cuts or parts from different species resulted in different chromatographic profiles. The qualitative and quantitative chromatographic differences among meat species were used for their identification. The LC method applies only to fresh and frozen meats. It is simple, rapid, and reliable, and can be used for quantitative detection of meat species in unheated meat blends.     

Liquid chromatographic method for determination of water in soils

Abstract

A simple, rapid, and sensitive liquid Chromatographic (LC) method for the determination of water in soils was developed. In this method, water is extracted from soil with anhydrous methanol and injected into an LC system including a cation‐exchange column in the H form. The eluent is 1.0 mM transcinnamaldehyde in acetonitrile‐methanol (40:60). The detection scheme is based on the effect of water on the equilibrium established when trans‐cinnamaldehyde and methanol react in the H⁺ column to form cinnamaldehyde dimethylacetal and water. The equilibrium of the reaction is shifted towards the trans‐cinnamaldehyde (absorbs strongly at the detection wavelength, 300 nm) when water is introduced into the column. The extent of the shift and the resulting change in absorbance at 300 nm are proportional to the amount of water present.

Application of the method to a wide range of soils and of clay minerals containing from 0.7 to 25% water showed that the results of the LC method agreed closely with those of the gravimetric method. The LC method is accurate, precise, relatively free from interference, requires a small sample size, and gives a linear calibration graph over approximately three orders of magnitude of water concentrations. A single operator can perform approximately 80 analyses in a normal working day.     

Liquid chromatographic methodology for the characterization of orange juice

Liquid chromatographic (LC) methodology potentially useful for the characterization of orange juice, with particular regard to detecting adulteration of orange juice by computer pattern recognition analysis, has been developed. After dilution with methanol the juice is extracted with hexane to remove the carotenoids, which are chromatographed on a C18 column with an acetonitrile-methanol-methylene chloride mobile phase and detection at 450 nm. Further extraction of the juice with methylene chloride isolates the methoxylated flavones, which are chromatographed by reverse phase LC with an acetonitrile-methanol-water mobile phase and detection at 280 nm. The flavanone glycosides remaining in solution are chromatographed on a C18 column with an acetonitrile-water mobile phase and detection at 280 nm. The precisions of the heights of the 32 LC peaks selected for pattern recognition analysis were determined from 5 replicate analyses of a single juice. Coefficients of variation of the replicates ranged from 0.3 to 4.5%, with an average of 2.1%. Adulteration of products with sodium benzoate-fortified pulpwash or grapefruit juice can be detected by this method. Pattern recognition analysis of the data obtained for 80 authentic and 19 adulterated orange juices showed that the method is potentially useful for distinguishing between authentic and adulterated products.     

Liquid chromatographic determination of sulfamethazine in milk

A simple, relatively rapid liquid chromatographic method has been developed for the determination of sulfamethazine (SMZ) in milk at levels in the low ppb range. The method is based on extracting SMZ from milk with chloroform, evaporating the chloroform, dissolving the residues in hexane, extracting into buffers, and chromatographing the buffer solution. The method has been shown to determine levels as low as 5 ppb reliably. Levels greater than or equal to 7 ppb have been confirmed by gas chromatography/mass spectrometry after derivatization of extracts from fortified, incurred, and shelf milk. Intralaboratory recoveries and percent coefficients of variation are satisfactory. Sulfadimethoxine and sulfaquinoxaline can also be determined by the method. Application of the method to other dairy products is being investigated.     

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 flucytosine in capsules

A liquid chromatographic method has been developed for determination of flucytosine in capsules. Flucytosine and p-aminobenzoic acid, the internal standard, are separated on a C18 reverse phase column using water-methanol-acetic acid mobile phase containing 1-octane-sulfonic acid sodium salt. Compounds are detected photometrically at 285 nm. Mean assay results for 250 and 500 mg commercial capsules were 101.5% (n = 5) of declared, respectively. Mean recovery of flucytosine added to commercial capsules was 99.3%.     

Liquid chromatographic determination of carbamazepine in tablets

A simple and rapid liquid chromatographic method is described for the qualitative and quantitative determination of carbamazepine in tablet composites and individual tablets, using the internal standard technique. Analyses were performed on a C-18 reverse-phase column with tetrahydrofuran-methanol-water (8 + 37 + 55) as the mobile phase. A linear relationship was obtained between detector responses at 254 nm and amounts of carbamazepine injected ranging from 0.2 to 1.7 micrograms. The coefficient of variation for 10 consecutive injections of a standard preparation was 0.4%. Recoveries of carbamazepine from 100 and 200 mg tablets averaged 101.4 and 99.7%, respectively. Assay results for commercial tablets analyzed by the proposed method agreed favorably with those obtained by the method of USP XXI. The assay results for individual tablets indicated that deviations from the average value and the range of individual values are much wider with the compendial method than with the proposed method.     

Liquid chromatographic determination of sulfamethazine in feeds

A reverse-phase liquid chromatographic method for the assay of sulfamethazine (SMZ) in feeds is described. Feed samples are extracted with 50% methanol solution, centrifuged, filtered, and diluted when necessary, and chromatographed on a C-18 column. Samples are eluted with a mobile phase of 20% methanol and 80% of a solution containing acetic acid and tetramethylammonium chloride. The average recovery from spiked samples was 97.2% with a coefficient of variation of 1.2%. Linearity was very good (correlation coefficient 0.9997). Within-day and between-day coefficients of variation averaged 1.3 and 2.6%, respectively. The results for samples assayed by this method compared closely with the results from the same extracts assayed by the AOAC colorimetric method.     

Liquid chromatographic determination of melamine in beverages

A liquid chromatographic method is described for the determination of melamine in beverages. Melamine is separated by column chromatography using cation and anion exchange resin and determined by ion-pair liquid chromatography using an ODS column and a mixture of acetonitrile and 0.05M phosphate buffer (pH 3.0) containing 0.005M sodium 1-laurylsulfate (1 + 4, v/v) as mobile phase. Recoveries of melamine ranged between 90.3 +/- 7.8 and 102.1 +/- 5.6% at levels of 0.6 to 2.4 ppm in 4 kinds of beverages. The quantitation limit was 2.5 micrograms melamine in 50 mL beverage. The method was applied to the migration test of melamine from melamine-formaldehyde resin products to the beverages.     

Liquid chromatographic method for analysis of elemental sulfur in pesticide formulations

A nonaqueous reverse-phase liquid chromatographic (LC) method has been developed to determine elemental sulfur in pesticide formulations. Samples were extracted in 50 mL of stabilized tetrahydrofuran (THF) by gentle swirling while sonicating for 1 min. A 5 microL aliquot was injected into the LC instrument equipped with a Vydac 218 TP 54 column. The mobile phase was methanol-acetonitrile-stabilized tetrahydrofuran (58.5 + 40 + 1.5). Sulfur was monitored at 280 nm. Retention time was approximately 5 min with total analysis time of 7 min. For 6 different products analyzed 12 times each, the coefficients of variations were all less than 3.5%. Purity of each sulfur peak was checked by using a photodiode array detector in the spectrum and absorbance ratio modes. No impurities were observed at the monitoring wavelength.     

Liquid chromatographic method for determination of citreoviridin in corn and rice

Citreoviridin, a neurotoxic mycotoxin, has been found as a natural contaminant in corn left unharvested in the southeastern United States and in rice of several Asian countries, including Japan. A reliable analytical method for the quantitative determination of citreoviridin in corn and rice is described. Corn or rice is extracted with dichloromethane, and the extract is partially purified on silica and amino solid-phase extraction (SPE) columns. The extract is analyzed for citreoviridin by normal-phase liquid chromatography, using a mobile phase of ethyl acetate-hexane (75 + 25) at 1.5 mL/min and a fluorescence detector to measure the yellow fluorescence (388 nm excitation, 480 nm emission). With a 100 microL injection loop, the relationship between concentration and injection volume is linear for 20-60 microL injections. Recoveries of citreoviridin added to yellow corn at 10-50 ng/g were 91.0-96.9%; recoveries from white corn (10-50 ng/g added) were 96.8-102.8%. Recoveries of 5000 ng/g added to white corn were 89.0%, indicating that heavily contaminated samples can be assayed by the method. Minimum detection limits were 10 ng for citreoviridin standard and 2 ng/g for citreoviridin added to corn. White rice fermented with Penicillium citreo-viride (1524 ppm) was mixed with and serially diluted with uncontaminated ground corn to obtain citreoviridin-contaminated corn (ca 25 ppb). When the samples were assayed by the method, a mean level of 24.4 +/- 1.65 ppb (6.5% coefficient of variation) was obtained. Four fermented rice food samples and 3 commercial rice samples were investigated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Liquid chromatographic methods for vitamins A and D in multivitamin-mineral formulations

Liquid chromatographic screening procedures have been developed for the estimation of vitamins A and D in multivitamin-mineral tablet, capsule, gelatin capsule, and syrup formulations. The procedure can be used for measuring vitamin A present as either retinyl acetate or retinyl palmitate, and also for measuring the contribution to total vitamin A activity from 13-cis retinyl esters. The retinyl esters and their isomers are resolved from each other and their oxidation products. Ergocalciferol and cholecalciferol are not resolved from each other but they are resolved from other vitamin D isomers and from vitamins A, E, and K and their degradation products. Both assays use a 3 microns amino column, with a mobile phase of hexane for vitamin A and 1% isopropanol in hexane for vitamin D. The precision of replicate injections for vitamins A and D is better than 1% and the recovery from spiked syrups is better than 98%. The coefficient of variation for both assay methods is about 5%. Twenty formulations were analyzed for vitamin A and 24 were analyzed for vitamin D.     

Liquid chromatographic determination of strychnine in stomach contents

A chloroform extract of stomach contents at basic pH is concentrated and then extracted with 0.1 M phosphoric acid. The acid extract is chromatographed on a 10 cm reverse phase column, using 0.005 M phosphate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (750 + 135 + 115) containing 0.01 M octanesulfonic acid at a flow rate of 1.0 mL/min for elution. Strychnine eluted in 7.3 min. Recoveries from spiked stomach contents averaged 92%. The method can be used without modification for other alkaloids.     

Liquid chromatographic determination of narasin in feed premixes

A liquid chromatographic (LC) method has been developed to determine narasin in feed premixes. Narasin is extracted from the premix with a methanol-water solvent, and the extracted solution is assayed by using LC. Recovery of narasin from a 12.5 g/lb premix is quantitative (100%), with a relative standard deviation of 1.44%. The results correlated well (coefficient 0.92) with a turbimetric bioassay method.     

Liquid chromatographic determination of oxfendazole in swine feeds

A relatively simple analytical method is presented for determination of oxfendazole (2-(methoxycarbonylamino)-5-phenylsulfinyl-benzimidazole) at levels as low as 0.012% in swine feeds, using cation exchange liquid chromatography (LC). The sample was extracted with a solvent mixture of methanol-glacial acetic acid (90 + 10) at 45 degrees C, using a gyrorotory shaker. Plant pigments and other feed excipients were removed using zinc acetate treatment and pH-controlled extraction. Oxfendazole was further separated from the remaining interferences and quantitatively determined by LC on a Partisil SCX column with acetonitrile-0.01M phosphate buffer as mobile phase. The method is stability-specific, linear, precise, and accurate at 80-120% labeled strength (relative standard deviation 0.9-1.7 with mean recovery of 98-99%). Supporting data at a level of 0.0135% oxfendazole in swine feed indicated that this method is capable of complete recovery of oxfendazole from medicated swine feeds.     

Liquid chromatographic determination of glibenclamide in human plasma

The oral hypoglycemic agent glibenclamide was determined in human plasma by liquid chromatography (LC). Samples, with internal standard added, are extracted with dichloromethane. The organic phase is evaporated, and the residue is reconstituted in mobile phase for injection onto the LC column. Intra- and inter-day variability of the method was assessed at high and low levels of the drug. Although coefficients of variation were similar for both intra- and inter-day studies at both levels, CVs were smaller at the higher concentration level. Recovery of the drug was good at both high and low levels. The minimum level of detection was 5 ng/mL.     

Liquid chromatographic determination of aflatoxicol in porcine liver

A liquid chromatographic (LC) method for determination of aflatoxicol in porcine liver was developed. Liver sample is homogenized with water, diluted with saturated Na2SO4 solution, and extracted with acetone. After filtration, less polar interferences are removed by partition with isooctane. Aflatoxicol in the aqueous fraction is partitioned into CHCl3. The extract is dried over anhydrous Na2SO4 and evaporated nearly to dryness at 35 degrees C under a gentle flow of dry filtered air or nitrogen. Residue is dissolved in CHCl3-hexane and applied to a hexane-activated silica cartridge. The cartridge is washed with hexane-CHCl3, then aflatoxicol is eluted with CHCl3-acetone. Purified extract is evaporated to dryness, dissolved in methanol, and analyzed by C18 reverse phase liquid chromatography using a water-CH3CN-acetic acid mobile phase and fluorescence detection. Recovery of aflatoxicol from spiked liver samples at levels ranging from 0.25 to 4.0 ng aflatoxicol/g wet tissue averaged 92% with a limit of detection of about 0.1 ng aflatoxicol/g liver.