Quantification of clenbuterol in equine plasma, urine and tissue by liquid chromatography coupled on-line with quadrupole time-of-flight mass spectrometry

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

Despite the impressive innate physical abilities of horses, camels, greyhounds, or pigeons, doping agents might be administered to these animals to improve their performance. To control these illegal practices, anti-doping analytical methodologies have been developed. This review compiles the analytical methods that have been published for the detection of prohibited substances administered to animals involved in sports over 30 years. Relevant papers meeting the search criteria that discussed analytical methods aiming to detect and/or quantify doping substances in animal biological matrices published from 1990 to 2019 were considered. A total of 317 studies were included, of which 298 were related to horses, demonstrating significant advances toward the development of doping detection methods for equine sports. However, analytical methods for the detection of doping agents in sports involving other species are lacking. Due to enhanced accuracy and specificity, chromatographic analysis coupled to mass spectrometry detection is preferred over immunoassays. Regarding biological matrices, blood and urine remain the first choice, although alternative biological matrices, such as hair and feces, have been considered. With the increasing number and type of drugs used as doping agents, the analytes addressed in the published papers are diverse. It is very important to continue to detect and quantify these drugs, recognizing those that are most frequently used, in order to punish the abusers, protect animals' health, and ensure a healthier and genuine competition.

Development and Validation of a Stability Indicating LC-MS/MS Method for the Determination of Clenbuterol HCl

Clenbuterol hydrochloride (CLT), β₂ adrenergic agonist is used as a bronchodilator in the therapeutic treatment of asthma. It is important to know the stability behaviour of the drug in different degradation conditions as per ICH Q1A (R2) guidelines for safety and efficacy purpose. The main objective of the study is to develop and validate stability indicating LC-MS/MS method for the determination of Clenbuterol HCl. The separation was achieved using Phenomenex Gemini NX C18 (250*4.6 mm, 5 μ) column and the mobile phase consisting of ammonium acetate buffer (5 mM), 0.15% triethylamine (TEA), pH 7.5 with acetic acid: methanol (70:30, v/v) at flow rate 1 ml/min. The detection was done using PDA detector at 245 nm. The validation was performed as per ICH Q2 (R1) guideline. The drug was subjected to stress degradation conditions as per ICH Q1A (R2) guidelines. The significant degradation was observed in acidic (8.78%) and sunlight (liquid) (9%) condition while no degradation was observed in neutral, basic, oxidation and thermal condition. The drug and its degradation products were characterized using LC-MS/MS and the proposed degradation mechanism was communicated. The developed method was found to be stability-indicating, simple, specific, selective, sensitive, linear, accurate, robust and precise and used as a routine analysis in quality control laboratory.

Sensitive detection of clenbuterol by hybrid iridium/silicon nanowire-enhanced laser desorption/ionization mass spectrometry

There is increasing demand for anti-doping drug monitoring in sports and food safety checks by developing sensitive and fast analytical methods. Here we report the development of hybrid Ir/SiNW as a new MALDI matrix for the detection of small molecules. This matrix is characterized by sufficient UV absorption, low-noise background, and high efficiency in ionization of small molecules. Sensitive detection of clenbuterol (LOD: 0.18 pmol) and a variety of other small molecules has been achieved using the Ir/SiNW matrix with a reproducible performance. Compared to the individual components separately, the matrix of hybrid Ir/SiNW synthesized via in situ growth can promote the MS signal intensity by up to 10 fold under identical experimental conditions. We provide a unique mechanism for the high performance of the hybrid Ir/SiNW matrix with the characteristic properties of hydrogen atom transfer and enhanced protonation at the interface of the hybrid nanostructures. Our approach of using a hybrid Ir/SiNW matrix enables detection of clenbuterol quantitatively in complicated biological samples and in vivo experiments, promising a useful tool for food security and anti-doping drug monitoring in sports.

Clenbuterol Hydrochloride

Clenbuterol (Broncodil and trade) is a direct-acting sympathomimetic agent with mainly beta-adrenergic activity and a selective action on β2 receptors (a β2 agonist). It has properties similar to those of salbutamol. It is used as a bronchodilator in the management of reversible airways obstruction, as in asthma and in certain patients with chronic obstructive pulmonary disease. The uses, applications, and the synthetic pathways of this drug are outlined. Physical characteristics including: ionization constant, solubility, X-ray powder diffraction pattern, thermal methods of analysis, UV spectrum, IR spectrum, mass spectrum are all produced. This profile also includes the monograph of British Pharmacopoeia, together with several reported analytical methods including spectrophotometric, electrochemical, chromatographic, immunochemical methods, and capillary electrophoretic methods. The stability, the pharmacokinetic behavior, and the pharmacology of the drug are also provided.

Analytical methods for the detection of clenbuterol

Clenbuterol is therapeutically used for the treatment of pulmonary diseases such as bronchial asthma or for tocolytic reasons. In cattle feeding as well as in sports it is illicitly misused due to its anabolic properties to promote muscle growth. Sample preparation procedures and analytical techniques used for the detection of clenbuterol are manifold and vary with the objectives of the investigation. Methods for its detection in biological specimens, drug preparations, the environment, food and feed products are reported. They are mainly based on immunochemical, chromatographic and mass spectrometric techniques, or on capillary electrophoresis. Sample preparation primarily includes liquid-liquid extraction and solid-phase extraction. Depending on the aim of the method clenbuterol can be determined in single- or multi-analyte methods. In biological and environmental samples concentrations are generally low due to the potency of the drug. Thus, highly sensitive procedures are required for expedient analyses.

Competitive immunoassay for clenbuterol using capillary electrophoresis with laser-induced fluorescence detection

A competitive immunoassay for detecting clenbuterol in urine was established by capillary electrophoresis (CE) with laser-induced fluorescence (LIF). The clenbuterol was conjugated with bovine serum albumin (BSA), and then the derivative was labeled with fluorescein isothiocyanate (FITC) and competes for antibody with free clenbuterol in the sample. Under the optimal conditions, Free and bound FITC labeled clenbuterol was separated within 8 min with the relative standard deviation (R.S.D.) 0.72% for migration time and 2.8% for peak area. The detection limit reached 0.7 ng/ml.

Improved method to quantify intracellular zidovudine mono- and triphosphate in peripheral blood mononuclear cells by liquid chromatography-tandem mass spectrometry

The determination of intracellular triphosphate metabolites of nucleoside analogs used in anti-HIV therapy is very challenging. Despite the well-known sensitivity and selectivity of LC-MS/MS, the measurement of the triphosphate metabolite of zidovudine (AZT-TP) remains difficult because of the interferences induced by endogenous nucleotides triphosphates. We describe a new approach that allows improved determination of AZT-TP simultaneously with AZT-monophosphate (MP). This was obtained, first, by monitoring a transition from the molecular ion of AZT-TP to a minor but very specific product ion. Then, the spiking of samples with a constant amount of AZT-TP allowed the signal to emerge from background, leading to increased sensitivity. Finally, the analytical run time was reduced to less than 10 min. The low limits of quantification were at 150 and 300 fmol per sample for AZT-TP and AZT-MP, respectively. Recoveries were higher than 85%. Inaccuracy and precision were lower than 10% and 15% (17% at the limit of quantification), respectively. The new method offers the possibility of determining simultaneously other nucleotide phosphates, as shown here for d4T-TP (the triphosphate metabolite of another nucleoside analog, stavudine or d4T) and 2'-deoxythymidine-5'-triphosphate or dTTP (the corresponding natural nucleotide triphosphate).

Multiresidue analysis of beta-agonists in pork by coupling polymer monolith microextraction to electrospray quadrupole time-of-flight mass spectrometry

A novel method of polymer monolith microextraction (PMME) using poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith combined with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) was developed for the rapid and sensitive determination of beta-agonists in pork samples. The conditions of PMME were optimized for the improvement of extraction efficiency and reduction of the matrix interferences from pork. Under the optimal condition, the eluate solution allowed direct analysis by mass spectrometry. In the positive ion mode and in the multiple reaction monitoring (MRM) mode, the limits of detection (LODs) for beta-agonists were found to be 0.08 ng/g (clenbuterol, CLB), 0.18 ng/g (salbutamol, SBTM) and 0.26 ng/g (terbutaline, TBTL) in pork, respectively, with good inter- and intra-day precisions (2-10% for CLB, 11-23% for SBTM and 4-16% for TBTL). The proposed PMME/ESI-QTOF MS method was successfully applied to the determination of beta-agonist residues in thirteen real samples, and the positive samples were confirmed according to the identification points (IPs) system defined by Commission Decision 2002/657/EC. To investigate the matrix effect, the proposed method was compared with PMME-HPLC/ESI-QTOF MS and the slight decrease in sensitivity of PMME/ESI-QTOF MS was ascribed to the inter-analyte ion suppression.

Validation and application of a screening method for beta2-agonists, anti-estrogenic substances and mesocarb in human urine using liquid chromatography/tandem mass spectrometry

Electrospray ionization (ESI) mass spectra of 15 anti-estrogenic substances, beta2-agonists and mesocarb were investigated in terms of fragmentation patterns. On the basis of this product ion information, a simultaneous screening method for anti-estrogenic substances, beta2-agonists and mesocarb was developed for doping control purposes. After hydrolysis, liquid-liquid extraction was adopted for the sample preparation. The recoveries for all compounds were 30 and 96%. A single liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis could be performed in 13 min for the analysis of 15 anti-estrogenic substances, beta2-agonists and mesocarb. A quantitative analysis was also validated. Inaccuracies were below +/-12% and precisions varied from 0 to 15.8%. The limit of detection was below 10 ng/mL except formestane (300 ng/mL) and aminoglutethimide (100 ng/mL). The validated method was applied for the analysis of excretion samples.

High-performance liquid chromatography electrospray ionization mass spectrometry determination of tulobuterol in rabbit's plasma

A sensitive and specific liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and quantification of tulobuterol in rabbits' plasma. After the addition of clenbuterol-HCl, the internal standard (IS) and 1.0 M sodium hydroxide solution, plasma samples were extracted using a solvent mixture comprised of 5% isopropanol in n-hexane. The compounds were separated on a prepacked Lichrospher CN (5 microm, 150 mm x 2.0 mm) column using a mixture of methanol-water (10 mM CH3COONH4, pH 4.0) as mobile phase. A Shimadzu LCMS-2010A mass spectrometer connected to a Shimadzu high performance liquid chromatograph (HPLC) was used to develop and validate the method. The method has shown to be sensitive and specific by testing six different blank plasma batches. Linearity was established for the range of concentrations 0.50-40.0 ng/mL with a coefficient of determination (r) of 0.9998. The intra-day precision was better than 15%. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.50 ng/mL. The proposed method enables the unambiguous identification and quantification of tulobuterol for pharmacokinetic, bioavailability or bioequivalence studies.

Tissue distribution of clenbuterol in the horse

Plasma and tissue concentrations of clenbuterol (CLB) were determined following oral (p.o.) administration of 1.6 microg/kg twice daily (b.i.d.) for 2 weeks. Horses were administered the last dose on morning of day 15, killed at 0.25, 24, 48, and 72 h post-administration. At 0.25 h, the highest tissue concentrations of CLB were found in the liver (16.21 ng/g), lung (6.48 ng/g), left ventricle (4.99 ng/g), kidney (3.35 ng/g), bronchi (2.56 ng/g), right ventricle (2.08 ng/g), and eye fluids (1.09 ng/g) all of which were higher than that of plasma (1.10 ng/mL). The elimination half-lives (t(1/2k)) for CLB in tissues ranged from 21.2 to 56.3 h, the longest were in the eye fluids (56.9 h), spleen (21.2 h), cerebrum (27.1 h), cerebellum (21.5) and cecum (23.7 h). The t(1/2k) for plasma was 10.9 h. Tissue/plasma ratios of liver (14.7), lung (5.9), left ventricle (4.6), kidney (3.1), bronchi, (2.3) and right ventricle (1.9) were high at 0.25 h and remained elevated up to 72 h. Accumulation and sustained high concentration of CLB relative to plasma in these tissues contributed to the prolonged elimination and the ability to quantify CLB in plasma and urine for a prolonged period.

Pharmacokinetics and disposition of clenbuterol in the horse

The pharmacokinetics of clenbuterol (CLB) following a single intravenous (i.v.) and oral (p.o.) administration twice daily for 7 days were investigated in thoroughbred horses. The plasma concentrations of CLB following i.v. administration declined mono-exponentially with a median elimination half-life (t(1/2k)) of 9.2 h, area under the time-concentration curve (AUC) of 12.4 ng.h/mL, and a zero-time concentration of 1.04 ng/mL. Volume of distribution (V(d)) was 1616.0 mL/kg and plasma clearance (Cl) was 120.0 mL/h/kg. The terminal portion of the plasma curve following multiple p.o. administrations also declined mono-exponentially with a median elimination half-life (t(1/2k)) of 12.9 h, a Cl of 94.0 mL/h/kg and V(d) of 1574.7 mL/kg. Following the last p.o. administration the baseline plasma concentration was 537.5 +/- 268.4 and increased to 1302.6 +/- 925.0 pg/mL at 0.25 h, and declined to 18.9 +/- 7.4 pg/mL at 96 h. CLB was still quantifiable in urine at 288 h following the last administration (210.0 +/- 110 pg/mL). The difference between plasma and urinary concentrations of CLB was 100-fold irrespective of the route of administration. This 100-fold urine/plasma difference should be considered when the presence of CLB in urine is reported by equine forensic laboratories.

Liquid chromatography/electrospray ionization tandem mass spectrometric screening and confirmation methods for beta2-agonists in human or equine urine

Electrospray ionization (ESI) mass spectra of 19 common beta(2)-agonists were investigated in terms of fragmentation pattern and dissociation behavior of the analytes, proving the origin of fragment ions and indicating mechanisms of charge-driven and charge-remote fragmentation. Based on these data, liquid chromatographic/ESI tandem mass spectrometric (LC/ESI-MS/MS) screening and confirmation methods were developed for doping control purposes. These procedures employ established sample preparation steps including either acidic or enzymatic hydrolysis, alkaline extraction and, in the case of equine urine specimens, acidic re-extraction of the analytes. In addition, a degradation product of formoterol caused by acidic hydrolysis during sample preparation could be identified and utilized as target compound in screening and also confirmation methods. The screening procedures cover 18 or 19beta(2)-agonists, the estimated limits of detection of which for equine and human urine samples vary between 2 and 100 ng ml(-1) and between 2 and 50 ng ml(-1), respectively. A single LC/MS/MS analysis can be performed in 9 min.

Identification of an unknown beta-agonist in feed by liquid chromatography/bioassay/quadrupole time-of-flight tandem mass spectrometry with accurate mass measurement

A new approach to the search for residues of unknown growth promoting agents such as anabolic steroids and beta-agonists in feed is presented. Following primary extraction and clean-up, samples are separated using gradient liquid chromatography (LC). The effluent is split towards two identical 96-well fraction collectors and an optional electrospray quadrupole time-of-flight mass spectrometry (QTOFMS) system for accurate mass measurement. One 96-well plate is used for a bioassay (enzyme-immuno assay, receptor assay) and will detect the bioactivity and position of the relevant peak in the chromatogram. The positive well in the second 96-well plate is used for identification by LC/QTOFMS/MS. The value of this LC/bioassay/QTOFMS/MS methodology is highlighted by the finding and structure elucidation of a new beta-agonist in a feed extract.

Quantification of [Dmt1]DALDA in ovine plasma by on-line liquid chromatography/quadrupole time-of-flight mass spectrometry

The synthetic peptide [Dmt(1)]DALDA (Dmt-D-Arg-Phe-Lys-NH(2); Dmt = 2',6'-dimethyltyrosine; 'super-DALDA') is a mu opioid-receptor agonist. On-line liquid chromatography/quadrupole time-of-flight mass spectrometry and the corresponding stable isotope-incorporated synthetic peptide internal standard were used to quantify [Dmt(1)]DALDA that had been extracted from ovine plasma samples. The [M+2H](2+) ion was used to construct the calibration curve, and the product ion was used for verification of the peptide. The detection sensitivity for the [Dmt(1)]DALDA [M+2H](2+) ion was 12.5 fmol and 50 fmol for the m/z 432.3 product ion. The concentration profile of [Dmt(1)]DALDA was determined from a set of ovine plasma samples. The molecular specificity of the peptide quantification was confirmed by tandem mass spectrometry (MS/MS).