RESUMEN
A liquid chromatographic/mass spectrometric (LC/MS) electrospray confirmation method has been developed to confirm 4 ionophores (monensin, lasalocid, salinomycin, and narasin) in a variety of animal feeds using a single quadrupole mass spectrometer. The sodium ions of these compounds are dominant in the electrospray mass spectrum. Using optimized "in-source" collision induced dissociation, characteristic fragment ions seen previously using MS/MS can be observed. The drugs were extracted from the feed matrix using hexane-ethyl acetate and isolated using a silica solid-phase extraction cartridge. These ionophores were confirmed in both medicated feeds and nonmedicated feeds fortified with these drugs at the 1-50 ppm level. In addition, this method was used to confirm residues of monensin in a nonmedicated feed that was collected from a feed mill immediately after the production of a similar feed that was medicated with high levels of monensin.
Asunto(s)
Alimentación Animal/análisis , Cromatografía Liquida/métodos , Ionóforos/análisis , Espectrometría de Masas/métodos , Alimentos Fortificados , Lasalocido/análisis , Lasalocido/química , Monensina/análisis , Piranos/análisis , Piranos/químicaRESUMEN
A solid-phase extraction (SPE) cleanup and a liquid chromatographic (LC) method with UV detection is presented for analysis of up to 7 ephedrine alkaloids in herbal products. Alkaloids from herbal products are extracted with acidified buffer, isolated on a propylsulfonic acid SPE column, eluted with a high-ionic-strength buffer, and separated by LC with detection at 255 nm. LC separation is performed by isocratic elution on a YMC phenyl column with 0.1 M sodium acetate-acetic acid (pH = 4.8) containing triethyl-amine and 2% acetonitrile. Ephedrine alkaloids are completely separated in 15 min. Average recovery of 5 common alkaloids from 3 spiked matrixes is 90%, with an average relative standard deviation (RSD) of 4.4% for alkaloid spikes between 0.5 and 16 mg/g. Average quantitation of ephedrine and pseudoephedrine from 6 herbal products is 97% of declared label claims, and average quantitation of synephrine from an herbal dietary product is 85% of label claim (RSD, 3.2%). Recoveries of synephrine, norephedrine, ephedrine, pseudoephedrine, N-methylephedrine, and N-methylpseudoephedrine spiked in 4 herbal products averaged 95%. Results of ruggedness testing and of a second laboratory validation of the procedure are also presented.
Asunto(s)
Alcaloides/análisis , Cromatografía Liquida/métodos , Efedrina/análisis , Fitoterapia , Ácido Acético , Acetonitrilos , Ácidos Alcanesulfónicos , Tampones (Química) , Efedrina/análogos & derivados , Etilaminas , Concentración de Iones de Hidrógeno , Concentración Osmolar , Fenilpropanolamina/análisis , Acetato de Sodio , Sinefrina/análisisRESUMEN
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¿. After derivatization, toluene is added directly to the sample, followed by water, to quench the derivatization process. After centrifugation, the organic layer is carefully removed. Analytes are determined by GC with electron capture detection (ECD). Milk was fortified with fenicols (the collective name for CAP, FF, and TAP) at 5, 10, 20, 40 and 80 ng/mL (target level = 10 ng/mL). Overall recoveries were 92, 100, and 104% for CAP, FF, and TAP, respectively. Overall interassay (between-day) variabilities were 6.1, 6.7, and 6.0% for CAP, FF, and TAP, respectively. Raw milk samples containing incurred residues of FF were also analyzed.
Asunto(s)
Antibacterianos/análisis , Cloranfenicol/análisis , Leche/química , Tianfenicol/análogos & derivados , Tianfenicol/análisis , Animales , Cromatografía de Gases , Residuos de Medicamentos/análisis , Indicadores y Reactivos , Estándares de Referencia , Espectrofotometría UltravioletaRESUMEN
A method was developed for determining methylmercury in various food commodities. The organomercurial species was converted to methylmercuric chloride by treatment of a sample homogenized with 1.8M HCl. The resulting chlorinated species was eluted from a Celite 545-sample homogenate column with methylene chloride. The eluate was treated with stannic chloride, and the analyte was isolated from coextractives by using a wide-bore capillary column with microwave-induced plasma atomic emission detection. The method was applied to both high- and low-moisture commodities during analysis of 32 samples of grains, cereal products, fruits, and vegetables. Methylmercury was found at trace levels (i.e., between a signal-to-noise ratio of 3:1 and 10:1) and up to 0.85 ppb. Recoveries of added methylmercury ranged from 70.0 to 114.0%. Limits of quantitation and detection were 0.63 and 0.24 pg on column, respectively, corresponding to 0.30 and 0.11 ng Hg/g sample for a 40 g sample treated according to the method.