Ion Trap Detector Research Articles

Survey of GrapevineVitis viniferaStem Polyphenols by Liquid Chromatography−Diode Array Detection−Tandem Mass Spectrometry

Grapes and red wine prepared from Vitis vinifera L. contain a variety of polyphenols. Some information is available about the polyphenols of the seeds and leaves of grapevine, but considerably less is known about the polyphenols of woody stems. In this paper, we describe the results of a study of polyphenolic compounds in grapevine stems. We demonstrate how a combination of reversed phase high-performance liquid chromatography with ultraviolet-diode array detection and electrospray ionization-tandem mass spectrometry ion-trap detection enables characterization of a phytochemical mixture of considerable complexity. As the polyphenol source, the stems of three frost-hardy grapevine varieties [Hasaine (Hasansky) sladki, Zilga, and Yubilei Novgoroda] were used. The main group of methanol-extractable polyphenols of stems consists of trans-resveratrol and its derivatives including oligomers and glucosides. As minor components of the extract, stilbenoid piceatannol as well as a number of nonstilbenoid polyphenols, mostly flavan-3-ols and phenolic acids glucosides, were determined. The total polyphenol content of the grapevine stems depends on the variety, whereby the stems of cultivar Yubilei Novgoroda with white grapes contain significantly less of both groups of polyphenols.

Solid phase microextraction and gas chromatography with ion trap detector (GC-ITD) analysis of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline

An analytical method for the determination of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline is reported. It consists of wax extraction with an acid buffer solution, head space solid phase microextraction and GC-ITD analysis. The limit of determination is 1 ng g −1. Wax samples from beekepers and commercial foundations were analysed, content of residues varied from <1 to 20.5 ng g −1.

Determination of Clotiazepam in the Plasma Using Gas Chromatography/Mass Spectrometry with an Ion-Trap Detector and its Application to Pharmacokinetics in Healthy Volunteers

A method determining the plasma concentration of clotiazepam was developed by using gas chromatography/mass spectrometry with an ion-trap detector and was validated for applying pharmacokinetics to human volunteers orally taken 5 mg dose of clotiazepam. The detection limit was 1 ng/ml and the limit of quantitation was 5 ng/mt. Intraday reproducibility and accuracy bias % were less than 8.2 and 10.2% with inter-day variations for those being within 7.0 and 13.8%, respectively. The recovery of clotiazepam was higher than 87%. The principal pharmacokinetic parameters were determined from the plasma concentration-time plot by non-compartmental or two-compartmental analysis. In non-compartmental analysis, the elimination half-life of 10.4 hr and the area under the curve of 651.3 ng hr/ml were determined, and the maximal concentration (158.6 ng/ml) in the plasma was obtained at 0.56 hr post-dose. The developed method can be appropriate to apply pharmacokinetics and bioequivalence of clotiazepam.

Determination of ochratoxin A in beer by LC–MS/MS ion trap detection

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus and Penicillium verrucosum. It was analysed in food and beverages so far. Due to its toxicity, the European community issued directives and some countries own regulations for OTA contents in food, feed, and beverages. This work describes a method for the determination of OTA in beer. It is based on a combined anion exchange/reversed phase clean-up and liquid chromatography with tandem mass spectrometry. This method was compared with a modified standard method and validated on the basis of spiked beer samples. The accuracy was checked with statistical tools ( t-test). Due to its good reproducibility, repeatability and robustness this method is a promising alternative to LC–FD (fluorescence detection) techniques.

Isomeric analysis of PCDD/PCDF in waste incinerator flyash by GC–MS/MS

The development of an analytical method for the analysis of PCDD/PCDF in flyash using a bench analytical system comprising of a gas chromatograph fitted with an ion trap detector operated in the tandem MS mode is described. The optimum settings for the most important MS/MS parameters are given, including those for the less reported mono- to tri-chlorinated dioxin and furan congener groups. Flyash samples from three waste incineration plants representing a decommissioned 1970s plant design, an upgraded and still operating plant originally designed in the 1970s, and a modern 1990s design operating plant have been analysed for PCDD/PCDF. The flyash samples were analysed for PCDD/PCDF using the methods developed and the total PCDD/PCDF, I-TEQ values and isomeric profiles are reported. The flyash from the older decommissioned incinerator had very significantly higher concentrations of PCDD/PCDF compared to the modern incinerator flyash.

Application of electrospray ionization-mass spectrometry to screen extractants for determination of insulin in an emulsion system by HPLC-UV

Soybean lecithin and phenol intensely interfered in the determination of insulin with HPLC-UV in an emulsion system which was developed for transmucosal delivery. Thus, in this study electrospray ionization mass spectrometry (ESI-MS) with ion trap detection was applied to screen extractants to remove soybean lecithin and phenol in an insulin-loaded emulsion system (IES). The results showed that n-pentanol was a suited extractant to meet the measurement requests because a large quantity of soybean lecithin and phenol were removed simultaneously, and there appeared no interferences brought by n-pentanol in insulin measurement. The analytical method was assessed by the criteria including linearity (linearity range: 1.05–7.34 U/mL and correlation coefficient: 0.99936), accuracy (recoveries: 98.1–102.5%), within-day precision (R.S.D.: 0.5%, n = 6), LOD (0.01 U/mL), and LOQ (0.03 U/mL), and exhibited high sensitivity and specificity, and considerable accuracy and precision on the determination of insulin in the emulsion system. The application of this method had been successfully performed to study the storage conditions of IES, and the results indicated that insulin in IES would be stable at 4 °C in light proof condition, which was significant for further pharmaceutical research.

Determination of mequitazine in human plasma by gas-chromatography/mass spectrometry with ion-trap detector and its pharmacokinetics after oral administration to volunteers

The objective of this study was to develop an assay for mequitazine (MQZ) for the study of the bioavailability of the drug in human subjects. Using one mL of human plasma, the pH of the sample was adjusted and MQZ in the aqueous phase extracted with hexane; the organic layer was then evaporated to dryness, reconstituted and an aliquot introduced to a gas chromatograph/mass spectrometer (GC/MS) system with ion-trap detector. Inter- and intra-day precision of the assay were less than 15.1 and 17.7%, respectively; Inter- and intra-day accuracy were less than 8.91 and 18.6 %, respectively. The limit of quantification for the current assay was set at 1 ng/mL. To determine whether the current assay is applicable in a pharmacokinetic study for MQZ in human, oral formulation containing 10 mg MQZ was administered to healthy male subjects and blood samples collected. The current assay was able to quantify MQZ levels in most of the samples. The maximum concentration (Cmax) was 8.5 ng/mL, which was obtained at 10.1 h, with mean half-life of approximately 45.5 h. Under the current sampling protocol, the ratio of AUCt-->last to AUCt-->infinity was 93.4%, indicating that the blood collection time of 216 h is reasonable for MQZ. Therefore, these observations indicate that an assay for MQZ in human plasma is developed by using GC/MS with ion-trap detector and validated for the study of pharmacokinetics of single oral dose of 10 mg MQZ, and that the current study design for the bioavailability study is adequate for the drug.

Identification and Quantification of 8 Sulfonylureas with Clinical Toxicology Interest by Liquid Chromatography–Ion-Trap Tandem Mass Spectrometry and Library Searching

Identification of sulfonylureas in blood may be useful in the evaluation of hypoglycemic crises of unknown origin. The aim of the present study was to develop a highly selective liquid chromatography-electrospray tandem mass spectrometry (MS-MS) method using an ion-trap detector for rapid screening, identification, and quantification of sulfonylureas in human plasma. After standard liquid-liquid extraction with glisoxepide as an internal standard, 8 sulfonylureas (glibenclamide, glipizide, gliclazide, glibornuride, glimepiride, carbutamide, chlorpropamide, and tolbutamide) were eluted from a C18 column within 10 min with an isocratic mobile phase. Drugs were identified and quantified in full-scan MS-MS mode by use of a homemade MS-MS library. We used the assay in 134 cases of hypoglycemic crises of unknown origin. No ion suppression effect was noted for the analytes at their specific retention-time windows. For all drugs, assay validation showed good linearity (r2>0.990) and acceptable imprecision and recovery based on commonly used criteria of acceptance. The mean extraction recoveries were 63%-87% for 5 sulfonylureas but <45% for 3 (carbutamide, chlorpropamide, and tolbutamide). Nevertheless, the high sensitivity of the MS instrument made possible detection and quantification of all 8 drugs at subtherapeutic to toxic concentrations with good precision. Sulfonylureas were found in 9 hypoglycemic patients. The described assay method allows accurate, rapid identification and quantification of 8 sulfonylureas in human plasma and can be used for specific diagnosis of factitious hypoglycemia caused by ingestion of these drugs.

Analysis of cocaine and three of its metabolites in hair by gas chromatography-mass spectrometry using ion-trap detection for CI/MS/MS

A sensitive GC/CI/MS/MS method was developed for the simultaneous determination of cocaine (COC), anhydroecgonine methylester (cocaine pyrolysis product, AEME), ecgonine methylester (cocaine enzymatic hydrolysis product, EME) and cocaethylene (cocaine with ethanol trans-esterification product, COET) in human hair samples. After acid hydrolysis, hair samples were extracted with an automated solid phase extraction (SPE). The analysis of cocaine and its three metabolites was performed using an ion-trap spectrometer in positive chemical ionization with isobutane as gas reagent. The procedure was validated. Weighted linear regression was found appropriate in a concentration range of 0.10-5.00 ng/mg for AEME, 0.05-5.00 ng/mg for COC, EME and COET. The limit of detection was estimated at 0.005 ng/mg for COC and COET, at 0.025 ng/mg for EME, and at 0.050 ng/mg for AEME. Method performance was evaluated in terms of trueness and precision using quality control (QC) samples over the investigated ranges. Method selectivity and robustness were also demonstrated.

Azithromycin extraction from municipal wastewater and quantitation using liquid chromatography/mass spectrometry

Azithromycin is a broad spectrum antimicrobial agent that is approved in the United States for use in humans. Due to azithromycin's low rate of metabolism it is likely to be found in wastewater treatment plants, where its broad spectrum of antimicrobial activity could lead to development of resistance in bacteria. A liquid–liquid extraction using K 2CO 3 and methyl- t-butyl ether (MTBE) was used to extract azithromycin from 10 ml aliquots of wastewater. Liquid chromatography was performed using a Luna C18(2) (30 mm × 2.0 mm) column with a mass spectrometer friendly mobile phase containing 50:24:2:24 acetonitrile, methanol, tetrahydrofuran, and 0.04 M ammonium hydroxide. The mass spectrometer used an electrospray source with positive ionization and an ion trap detector. A linear standard curve from 5 to 200 pg/ml was validated and used to quantitate azithromycin in wastewater.

Validation of Liquid Chromatography-Electrospray Ionization Ion Trap Mass Spectrometry Method for the Determination of Mesocarb in Human Plasma and Urine

Mesocarb metabolism in humans is the target of this investigation. A high-performance liquid chromatographic (LC) method with electrospray ionization (ESI)-ion trap mass spectrometric (MS) detection ion trap "SL" for the simultaneous determination of mesocarb and its metabolites in plasma and urine is developed and validated. Ten metabolites and the parent drug are detected in human urine, and only four in human plasma, after the administration of a single oral dose of 10 mg of mesocarb (Sydnocarb, two 5-mg tablets). Seven of this metabolites have been found for the first time. The confirmation of the results and identification of all the metabolites except amphetamine is performed by LC-MS, LC-MS-MS, and LC-MS3. In the case of doping analysis, the reliable detection time for mesocarb (long-life dihydroxymesocarb metabolites of mesocarb) is approximately 10-11 days after the administration of the drug, which is a significant increase over the existing data. The detection of amphetamine in plasma and urine is made using simple flow-injection analysis without a chromatographic separation. The addition-calibration method is used with plasma and urine. The mean recoveries from plasma are 49.2% and 57.4% for mesocarb concentrations of 33.0 and 66.0 ng/mL, respectively, whereas the recoveries from human urine are 76.9% and 81.4% for concentrations of 1 and 2 ng/mL, respectively. Calibration curves (using an internal standard method) are linear (r2>0.9969) for concentrations 0.6 to 67 ng/mL and from 0.05 to 5 ng/mL in plasma and urine, respectively. Both intra- and interassay precision of plasma control samples at 3, 40, and 55 ng/mL are lower than 6.2%, and the concentrations do not deviate for more than -3.4% to 7.3% from their nominal values. In urine, intra- and interassay precision of control samples at 0.08, 1.5, and 3.0 ng/mL is lower than 14.1%, with concentrations not deviating for more than -11.3% to 13.7% from their nominal values. The plasma disappearance curve of the parent drug is obtained. The major pharmacokinetic parameters are calculated.

Polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans in soil samples from airport areas of Croatia

Levels and patterns of polychlorinated biphenyls (PCBs) were studied in surface soil samples collected in the coastal part of Croatia within and surrounding four different airports and in the vicinity of two partially devastated electrical transformer stations. The compounds accumulated from air-dried soil samples by multiple ultrasonic extraction with an n-hexane : acetone 1 : 1 mixture were analysed by capillary gas chromatography with electron capture and ion-trap detection. PCBs were quantified against a standard Aroclor 1242/Aroclor 1260 mixture and a standard mixture of 17 individual PCB congeners (IUPAC No.: 28, 52, 60, 74, 101, 105, 114, 118, 123, 138, 153, 156, 157, 167, 170, 180, and 189). The mass fractions of total PCBs in 18 soil samples collected within the airport premises ranged from 3 to 41 327 µg/kg dry weight (dw) (median: 533 µg/kg dw), and those in 21 samples collected at a distance ranging from several metres to 5 km away from the airport fence, from <1 to 39 µg/kg dw (median: 5 µg/kg dw). The highest PCB levels were determined in soils along the airport aprons where the aircrafts were serviced and refuelled. The PCB pattern was very similar to technical Aroclor 1260 in all airport soils. The PCB pattern in 22 soils collected in the vicinity of electrical transformer stations was dominated by congeners contained in Aroclor 1242. These soils contained 7 to >400 µg/kg dw of total PCBs. One highly PCB-contaminated airport soil sample was analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). With an international toxic equivalent (I-TEQ) of 9.7 ng/kg dw, the airport soil contamination was within values typical for urban and rural areas, and the congener patterns gave no clear indication for PCBs as the only source of PCDDs/PCDFs.

Screening and semi-quantitative analysis of post mortem blood for basic drugs using gas chromatography/ion trap mass spectrometry

The study presented here shows that GC–MS with ion trap detection can be used for screening post mortem blood. The method described was used to simultaneously screen for unknowns, identify basic drugs present and semi-quantitate 14 drugs commonly encountered in coroner's toxicology (i.e. was used to determine whether the drugs were present in sub-therapeutic, therapeutic or greater than therapeutic amounts). The equipment used included a Varian Saturn 2000 GC–MS operating in full scan mode, a CP-3800 GC, a CP-8400 autosampler and Saturn GC–MS workstation Version 5.5 software. Post mortem blood samples were extracted using a standard liquid–liquid procedure; diethylether followed by back extraction into 0.1 M HCl. Standard curves for the 14 drugs which were semi-quantitated (amitriptyline, citalopram, clozapine, cocaine, cyclizine, diazepam, dihydrocodeine, dothiepin, methadone, mirtazapine, procyclidine, sertraline, tramadol, venlafaxine) were prepared covering the concentration range 0–1.0 ug/mL. The procedure is in routine use for coroners toxicology; semi-quantitation has been used (i) to speed-up the through put of cases where drugs are an incidental finding and (ii) for cases where the amount of sample submitted for analysis was too small to allow for screening, identification and quantitation on separate sample volumes.

Miniaturised sample preparation of fatty foodstuffs for the determination of polychlorinated biphenyls.

A miniaturised analytical method allowing the exhaustive extraction of environmentally relevant polychlorinated biphenyls (PCBs) from fatty foodstuffs and the purification of the extracts in a single step has been developed. After dispersion of the freeze dried sample on silica modified with 44% (w/w) of sulphuric acid, the mixture was packed in a glass column on top of a multilayer silica column used for removal of the lipids and biogenic co-extracted material. Using this arrangement, a complete sample preparation can be accomplished by two successive 10 min static extractions with hexane followed by a brief dynamic step to ensure purging of the sample and sorbents. The analytical method showed a satisfactory performance, with recoveries of the endogenous PCBs studied in the 81-134% range of those found using a more conventional off-line procedure, even though as small an amount of sample as 0.1 g was used. Detection limits by gas chromatography with micro-electron capture detection (GC-ECD) were in all cases lower than 0.3 ng/g sample (freeze dried basis) and the repeatability of the complete analytical procedure better than 14% (except for PCB 167). When combined with GC and ion trap detection in the tandem mass spectrometry mode, the miniaturised method has been proved to be a valuable alternative to the more expensive high resolution mass spectrometry for fast screening of PCBs 77, 126, and 169, even if these congeners were not isolated from the bulk of PCBs.

Evaluation of MISPE for the multi-residue extraction of β-agonists from calves urine

Methods based on molecular recognition mechanisms for the clean-up of veterinary drugs and their residues, such as immuno-, receptor- and acceptor-affinity and molecularly imprinted polymers (MIPs), have been described as selective tools to improve the selectivity and the reliability of analytical results. In this work, we tested the extraction recovery performances of a MISPE column, designed for multi-residual clean-up of β-agonists. For this purpose, 18 different samples of calf urine were spiked at 0.25, 0.50 and 1.00 ppb with pooled standard solutions of clenbuterol (Clen), tulobuterol (Tolu), isoxsuprine (Isox), brombuterol (Brom), mapenterol (Mape) and ractopamine (Racto) and analysed on two independent analytical sessions, on a LC–MS/MS ion trap detector. Averaged recoveries, constant for each molecule considered, were 64.6% for Racto, 63.0% for Salm, 59.9% for Form, 54.7% for Brom, 52.0% for Clen, 41.8% for Mape, 38.6% for Tolu and 34.5% for Isox, respectively. Reproducibility studies gave a CV<11% at the 0.25 ppb level. The decision limit for the identification of the target drugs ranged from 0.01 ppb for mapenterol to 0.19 ppb for salmeterol, when considering one precursor, and two product ions as identification points. Such findings indicate that the choice of the appropriate molecule as template in the MIP preparation is the critical factor to guarantee a reliable analytical multi-residue approach for β-agonists, despite the structural differences among molecules exploiting almost the same pharmacological effect.

Comparison of gas and high performance liquid chromatography with selective detection for determination of triazine herbicides and their degradation products extracted ultrasonically from soil

AbstractGC and HPLC with selective detectors were compared for simultaneous determination of triazine herbicides simazine, atrazine, propazine, terbuthylazine, cyanazine, ametryn, prometryn, and atraton, and of their dealkylated degradation products in soil. The compounds were ultrasonically extracted from spiked agricultural soil samples (organic matter content &lt; 5%) with a 2:1 acetone:n‐hexane mixture. High efficiency of GC capillary column and high selectivity of the thermionic sensitive detector (TSD) and ion trap detector (ITD) made it possible to directly analyse uncleaned soil extracts and determine all 12 compounds in one run. In reversed‐phase HPLC with diode‐array detector (DAD), the co‐elution of soil matrix components interfered with the determination of methylthiotriazines and terbuthylazine. The recovery of triazine compounds, determined by GC‐TSD, from a silty sand soil (organic matter content 1.82%, pH 6.22) spiked at levels of 15–600 ng g–1, were 70–90% (RSD 9–19%), except for deisopropylatraton (38%). GC‐TSD analysis with detection limits of 5–15 ng g–1 for chloro‐ and methylthiotriazines and 30 ng g–1 for methoxytriazines was more sensitive than GC‐MS(ITD). GC analysis with electron capture detection was sensitive for some chlorotriazines, but a reliable compound quantification in complex chromatograms of uncleaned soil of extracts was not possible. For all compounds save didealkylatrazine, HPLC‐DAD was at least two times less sensitive than GC‐TSD. Soil/sediment organic matter, clay and silt content, and pH were identified as matrix characteristics which might affect ultrasonic extraction recovery of a particular compound.

Adsorption–desorption effects in ion trap mass spectrometry using in situ ionization

Quadrupole mass spectrometers were compared for the GC–MS analysis of six molecules frequently encountered in analytical toxicology: diazepam, alprazolam, triazolam, LSD (lysergic acid diethylamide), trimethylsilylated LSD and trimethylsilylated buprenorphine. Experiments performed with ion trap detectors using in situ ionization led to important chromatographic peak tailing for the most polar compounds; it was assumed to result from adsorption–desorption of neutral molecules in the mass spectrometer. This study showed that the degree of peak tailing is correlated with analyte polarity, with materials coating ion trap surfaces and with analysis temperature and that this anomaly can be greatly reduced using passivated surfaces and a high temperature of analysis.

Solid-phase microextraction liquid chromatography/tandem mass spectrometry to determine postharvest fungicides in fruits.

A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were investigated, and their impact on the SPME-LC/MS was studied. Dynamic and static modes of desorption were compared and the variables affecting desorption processes in SPME-LC optimized. Static desorption provided the best recoveries and peak shapes. Recoveries at the limit of quantification (LOQ) levels were between 10% for prochloraz and 60% for o-phenylphenol, with relative standard deviations from 13.6% for prochloraz to 3.1% for o-phenylphenol. The versatility of the method was also exhibited by its excellent linearity in the concentration intervals between 0.0005 and 5 mg kg(-1) for dichloran and 0.01-10 mg kg(-1) for tolclofos methyl and prochloraz. LOQs ranged from 0.25 to 1 microg g(-1) using DAD, from 0.002 to 0.01 microg g(-1) using LC/MS, and from 0.0005 to 0.01 to microg g(-1) using LC/MS/MS. LOQs obtained in the present study using LC/MS and LC/MS/MS are lower than maximum residue limits established for all the fungicides in any matrix studied. The method enables to determine polar pesticides at low-microgram per gram levels in fruits.

Determination of ticlopidine in human plasma by capillary gas chromatography with ion trap detection

A gas chromatographic method for determination of ticlopidine in human plasma using mass spectrometric detection was developed. A Perkin Elmer model 8500 gas chromatograph coupled to an ion trap detector (ITD) in electron impact mode (EI) was used. The gas chromatograph was fitted with a 30 m×0.32 mm i.d., DB-17 capillary column with a film thickness of 0.25 μm. The compounds were isolated from plasma by Extrelut-1 solid-phase extraction using hexane as the solvent of elution. The detection and quantification limits for this method were 0.005 and 0.01 μg/ml, respectively. The calibration curves were linear from 0.01 and 2.5 μg/ml. Recoveries from human plasma spiked at 0.01 and 2.0 μg/ml ranged from 84.4 and 87.3%. The coefficient of variation (CV) was between 5.1 and 6.9%. The results show that the sensitivity, accuracy and precision of the method are adequate for the determination of ticlopidine in human plasma samples. The ITD in SIM mode allows the unequivocal identification of ticlopidine. The suitability of this method was evaluated in the determination of ticlopidine in plasma from healthy volunteers following oral administration of a dose of 500 mg/day.

Feed additives in animal nutrition: Quantification of a new adrenergic drug by hyphenated techniques

AbstractZilpaterol, (±)‐trans‐4,5,6,7‐tetrahydro‐7‐hydroxy‐6‐(isopropylamino) imidazo [4,5,1‐jk]‐[1]benzazepin‐2(1H)‐one, is an adrenergic agonist drug licensed in Mexico and South Africa as feed additive for cattle at slaughter age. In contrast, the EU legislative framework prohibits the use of beta‐agonists as growth promoters to produce lean meat. In this study, the compound was quantified as its TMS derivative both by gas chromatography‐mass spectrometry (GC‐MS) with a quadrupole detector (QUADR) and by GC‐MS/MS with an ion trap detector (ITD), in Electron Impact (EI) ionization. Subsequently, an extraction and clean‐up procedure for the identification of Zilpaterol in commercial feeds was set up. Different extraction solvents and matrices were considered for their influence on Zilpaterol yield. The analytical method led to good recoveries and limits of detection and quantification in feeds well below the 5–20 μg/g dose proposed for animal nutrition.