Quantitative multi-residue determination of beta-agonists in bovine urine using on-line immunoaffinity extraction-coupled column packed capillary liquid chromatography-tandem mass spectrometry

Current Advances in Immunoassays for the Detection of β2-Agonists

β2-agonists are a group of synthetic phenylethanolamine compounds which are traditionally used for treating bronchospasm. These compounds can also increase skeletal muscle mass and decrease body fat. The illegal use of β2-agonists in food-producing animals results in residue of β2-agonists in edible tissues and causes adverse health effects in humans. Thus, the detection of β2-agonists at trace level in complex sample matrices is of great importance for monitoring the abuse of β2-agonists. Many methods have been developed to detect β2-agonists. Among them, a variety of antigen–antibody interaction-based techniques have been established to detect β2-agonists in various samples, including animal feed, urine, serum, milk, tissues and hair. In this review, we summarized current achievement in the extraction of β2-agonists from testing samples and detection of β2-agonists using immunological techniques. Future perspectives were briefly discussed.

Nano liquid chromatography, an updated review

Low flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for mass spectrometry have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow liquid chromatography , the types of columns employed, and strategies for multi-dimensionality of separations, which is key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend towards biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy to use platform.

Analysis of β-agonists in different biological matrices by liquid chromatography–tandem mass spectrometry

Introduction

Wide use is made of β-agonists in therapy due to their smooth muscle–relaxant properties. They also have a side effect of increasing muscle mass. Besides improving oxygen utilisation as bronchodilators, β-agonists increase protein synthesis and promote fat burning. The growth- and performance-enhancing effects are often exploited in illegal use. The guiding objective of this study was to develop a procedure for the determination of β-agonists by a single method in different types of matrices.

Material and Methods

Five grams of homogenised samples were subjected to enzymatic hydrolysis with β-glucuronidase in ammonium acetate, pH 5.2. Purification was performed by solid phase extraction. Analytes were eluted with 10% acetic acid in methanol. The eluted β-agonists were analysed by high-performance liquid chromatography–tandem mass spectrometry.

Results

Validation results met the requirement of the confirmation criteria according to European Commission Decision 2002/657/EC in terms of apparent recoveries (93.2–112.0%), repeatability (3.1–7.1%) and intra-laboratory reproducibility (4.1–8.2%).

Conclusion

The method can be successfully applied in the detection and determination of clenbuterol, salbutamol, mabuterol, mapenterol, terbutaline, brombuterol, zilpaterol, isoxsuprine and ractopamine in feed, drinking water, urine, muscle, lung and liver matrices.

Mixed mode monolithic sorbent in pipette tip for extraction of ractopamine and clenbuterol prior to analysis by HPLC-UV and UHPLC-Q ExactiveTM Plus Orbitrap MS

This work developed a fast and simple method for the quantification of two important β-agonists, ractopamine (RAC) and clenbuterol (CLEN) in animal urines. The method was based on micro-extraction by a mixed mode monolithic material and analysis by HPLC-UV and UHPLC-Q ExactiveTM Plus Orbitrap mass spectrometer. A mixed functional monolith with nonpolar ester-based structure containing polar carboxylic groups was thermally synthesized in situ in the pipette tips. The material combines both hydrophobic and ionic interactions. Parameters including conditions and composition of reagents for the in-pipette tip monolith synthesis, as well as the extraction process, were investigated and optimized. The procedure for extraction is 800 μL washing solvent of 10:90 (v/v) ACN:water and 150 μL eluting solvent of 30:70 (v/v) ACN:200 mM acetate buffer pH 4.0. Extraction efficiencies of 92% and 100% for RAC and CLEN, respectively, were achieved within 5 min with total organic solvent consumption of 395 μL. The extracts of spiked cattle and swine urines were analyzed by HPLC-UV and UHPLC-Q ExactiveTM Plus Orbitrap mass spectrometer. Good recovery with acceptable precision was observed. The mass spectrometry data confirmed efficient matrix removal by the synthesized extraction sorbent allowing routine analysis by the HPLC-UV method.

Development and validation of an UHPLC-MS/MS method for β2-agonists quantification in human urine and application to clinical samples

A fast analytical method for the simultaneous detection of 24 β₂-agonists in human urine was developed and validated. The method covers the therapeutic drugs most commonly administered, but also potentially abused β₂-agonists. The procedure is based on enzymatic deconjugation with β-glucuronidase followed by SPE clean up using mixed-phase cartridges with both ion-exchange and lipophilic properties. Instrumental analysis conducted by UHPLC-MS/MS allowed high peak resolution and rapid chromatographic separation, with reduced time and costs. The method was fully validated according ISO 17025:2005 principles. The following parameters were determined for each analyte: specificity, selectivity, linearity, limit of detection, limit of quantification, precision, accuracy, matrix effect, recovery and carry-over. The method was tested on real samples obtained from patients subjected to clinical treatment under chronic or acute therapy with either formoterol, indacaterol, salbutamol, or salmeterol. The drugs were administered using pressurized metered dose inhalers. All β₂-agonists administered to the patients were detected in the real samples. The method proved adequate to accurately measure the concentration of these analytes in the real samples. The observed analytical data are discussed with reference to the administered dose and the duration of the therapy.

A robust high-throughput fungal biosensor assay for the detection of estrogen activity

Estrogenic active compounds are present in a variety of sources and may alter biological functions in vertebrates. Therefore, it is crucial to develop innovative analytical systems that allow us to screen a broad spectrum of matrices and deliver fast and reliable results. We present the adaptation and validation of a fungal biosensor for the detection of estrogen activity in cow derived samples and tested the clinical applicability for pregnancy diagnosis in 140 mares and 120 cows. As biosensor we used a previously engineered genetically modified strain of the filamentous fungus Aspergillus nidulans, which contains the human estrogen receptor alpha and a reporter construct, in which β-galactosidase gene expression is controlled by an estrogen-responsive-element. The estrogen response of the fungal biosensor was validated with blood, urine, feces, milk and saliva. All matrices were screened for estrogenic activity prior to and after chemical extraction and the results were compared to an enzyme immunoassay (EIA). The biosensor showed consistent results in milk, urine and feces, which were comparable to those of the EIA. In contrast to the EIA, no sample pre-treatment by chemical extraction was needed. For 17β-estradiol, the biosensor showed a limit of detection of 1ng/L. The validation of the biosensor for pregnancy diagnosis revealed a specificity of 100% and a sensitivity of more than 97%. In conclusion, we developed and validated a highly robust fungal biosensor for detection of estrogen activity, which is highly sensitive and economic as it allows analyzing in high-throughput formats without the necessity for organic solvents.

Semiquantitative immunohistochemical detection of progesterone receptors in male accessory sex glands as a screening assay for anabolic steroid use in bulls

We investigated the immunohistochemical expression of progesterone receptors (PRs) in the prostate and bulbourethral glands of thirty-two 10–14-mo-old Charolais bulls following treatment with a low dosage of estrogens. Animals were divided into 2 groups: 16 animals (group T) were treated for 71 d with a therapeutic dose of trenbolone acetate and estradiol by subcutaneous implant, 16 animals (group C) received no treatment. Urine samples were collected both at the beginning of the trial and 9 times during the study. A semiquantitative analysis of immunohistochemistry (IHC) was performed by counting the number of positive cells in 10 randomly selected high-power fields (hpf). Both groups showed no significant histologic lesions. IHC examination showed positive cells in the epithelium of both glands, with different patterns of distribution between groups. In group C, IHC-positive cells per hpf varied from 0 to 40 in the prostate and from 0 to 32 in the bulbourethral gland. In group T, positive cells varied from 0 to 85 per hpf in the prostate and from 0 to 75 in the bulbourethral gland. The treated group showed significantly higher median numbers of positively stained cells in both organs than the controls (  p < 0.001). Chemical analysis of the urine samples confirmed that the experimental treatment mimics continuous, low-dose administration of anabolic steroids. IHC quantification showed good sensitivity with a high predictive power to correctly classify treated animals and could be used as a preliminary screening test in bulls.

Ultrasensitive quantitative LC–MS/MS of an inhibitor of apoptosis protein's antagonist in plasma using protein target affinity extraction

Background: A target protein-based affinity extraction LC–MS/MS method was developed to enable plasma level determination following ultralow dosing (0.1–3 µg/kg) of an inhibitor of apoptosis proteins molecule. Methodology & results: Affinity extraction (AE) utilizing immobilized target protein BIR2/BIR3 was used to selectively capture the inhibitor of apoptosis proteins molecule from dog plasma and enable removal of background matrix components. Pretreatment of plasma samples using protein precipitation was found to provide an additional sensitivity gain. A LLOQ of 7.8 pM was achieved by combining protein precipitation with AE. The method was used to support an ultralow dose dog toxicity study. Conclusion: AE-LC–MS/MS, utilizing target protein, is a highly sensitive methodology for small molecule quantification with potential for broader applicability.

Confirmation of the progesterone receptor as an efficient marker of treatment with 17β-estradiol in veal calves

Under current European Union legislation the use of anabolic steroids in food-producing livestock is banned because of their long-term adverse effects on human health. We examined the expression profile of the immunohistochemical marker progesterone receptor in veal calves' sex accessory glands following experimental administration of anabolic compounds. The aim was to confirm the accuracy of the immunohistochemical approach in the detection of the over-expression of the progesterone receptor induced by the administration of sexual steroids at low levels (17β-estradiol and nandrolone alone or in combination). A total of 217 male veal calves were randomly divided into four groups: group A (104 calves) treated with 17β-estradiol (5 mg/head; 4 weekly injections); group B (20 calves) treated with nandrolone (50 mg/head; 4 weekly injections); group C (20 calves) treated with the association of the two steroids (5 mg estradiol + 50 mg nandrolone; 4 weekly injections); and group K (73 calves) kept as a control. All the sexual accessory glands were collected at the slaughterhouse (15 days after the last administration) and subjected to immunohistochemical staining with anti-progesterone receptor antibody. All the calves treated with 17β-estradiol alone or in association with nandrolone (groups A and C) showed strong positivity, while nandrolone-treated calves and controls (groups B and K) gave negative results to the immunohistochemical investigation. The statistical analysis showed that the progesterone receptor is a significant predictor of 17β-estradiol treatment alone or in association with nandrolone (p < 0.001): the immunohistochemical study resulted in 100% sensitivity (CI = 95%: 97.1-100%) and specificity (CI = 95%: 95.1-100%) for prostate and 99% sensitivity (CI = 95%: 95.6-100%) and 100% specificity (CI = 95%: 95.1-100%) for bulbo-urethral glands. The data confirm that this innovative biological approach offers a reliable tool to enhance the efficacy of the histological test to detect illegal treatments with estrogens alone or in association with androgens.

Using gold nanoparticles as probe for detection of salmeterol xinafoate by resonance Rayleigh light scattering

The paper explores the method of determination of salmeterol xinafoate at nanogram level with gold nanoparticles (AuNPs) probe, to measure the intensity of resonance Rayleigh light scattering (RLS) by a common spectrofluorometer. The RLS intensity of salmeterol xinafoate was greatly enhanced by AuNPs, with the maximum scattering peak at 357 nm. The salmeterol xinafoate was determined basing on the binding of salmeterol xinafoate to AuNPs by electrostatic adsorption. Under the optimum conditions, the enhanced RLS intensity was directly proportional to the concentration of salmeterol xinafoate in the range of 0.054-6.038 μg mL(-1) with a good linear relationship (r=0.9928). The limit of detection (LOD) was 9.48 ng mL(-1). The interference tests were performed carefully. With the proposed method, the synthetic samples were analyzed satisfactorily, the recovery and RSD were 102.5-103.0% and 0.67-1.0% respectively.

In vitro studies on the behavior of salmeterol xinafoate and its interaction with calf thymus DNA by multi-spectroscopic techniques

The salmeterol xinafoate (SX) binding to calf thymus DNA in vitro was explored by fluorescence, resonance light scattering (RLS), UV-vis absorption, as well as viscometry, ionic strength effect and DNA melting techniques. It was found that SX could bind to DNA weakly, and the binding constants (Ka) were determined as 8.52×10(3), 8.31×10(3) and 6.14×10(3) L mol(-1) at 18, 28 and 38°C respectively. When bound to DNA, SX showed fluorescence quenching in the fluorescence spectra and hyperchromic effect in the absorption spectra. Stern-Volmer plots revealed that the quenching of fluorescence of SX by DNA was a static quenching. Furthermore, the relative viscosity and melting temperature of DNA solution were hardly influenced by SX, while the fluorescence intensity of SX-DNA was observed to decrease with the increasing ionic strength of system. Also, the binding constant between SX and double stranded DNA (dsDNA) was much weaker than that between SX and single stranded DNA (ssDNA). All these results suggested that the binding mode of SX to DNA should be groove binding. The obtained thermodynamic parameters indicated that electrostatic force might play a predominant role in SX binding to DNA. The quantum yield (φ) of SX was measured as 0.13 using comparative method. Based on the Förster resonance energy transfer theory (FRET), the binding distance (r0) between the acceptor and donor was calculated as 4.10 nm.

Development, validation and application to real samples of a multiresidue LC-MS/MS method for determination of β2 -agonists and anabolic steroids in bovine hair

β(2) -agonists are often abused in cattle breeding because of their effects on animal growth and meat properties. The use of β(2) -agonists as growth promoters is forbidden in the European Union (Council Directive 96/23/EC classifies them into group A of Annex I), due to their toxicity and carcinogenic properties, as for anabolic steroids, which are often administered in combination with β(2) -agonists, to promote the storage of proteins and increase muscle size. A unique confirmatory liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative detection of 13 β(2) -agonists and anabolic steroids plus the qualitative identification of other three analytes in bovine hair was developed and validated, according to Decision 2002/657/CE. Hair samples were washed with dichloromethane, digested within a NaOH solution and subjected to liquid-liquid extraction. The analysis was performed by high performance liquid chromatography coupled to a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The absence of matrix interferents, together with good repeatability of both retention times and relative abundances of diagnostic transitions, allowed the correct identification of all analytes. The quantitative calibrations obtained from spiked blank hair samples proved linear in the range tested. CCα and CCβ ranged from 0.5 ng/g to 30 ng/g. Intralaboratory reproducibility (CV%) ranged between 5.0 and 17.7 and trueness between 96% ± 7% and 105% ± 8%. The applicability of the method to real positive samples was demonstrated for both β(2) -agonists and anabolic steroids. 17α-boldenone was found in most (70%) hair samples obtained from untreated animals, supporting the hypothesis of endogenous production of this steroid.

Preparation of stir cake sorptive extraction based on poly(4-vinylbenzoic acid-divinylbenzene) monolith and its application in sensitive determination of β-agonists in milk and swine urine samples

In this study, a new stir cake sorptive extraction (SCSE) based on poly(4-vinylbenzoic acid-divinylbenzene) (VBADB) monolith was prepared. The effect of preparation conditions of monolith on extraction efficiencies was investigated in detail. Several characteristic techniques, such as elemental analysis, infrared spectroscopy, mercury intrusion porosimetry and scanning electron microscopy were used to characterize the monolithic material. The combination of SCSE-VBADB with high-performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS) detection was developed for sensitive determination of ultra-trace β-agonists in milk and swine urine samples. In order to obtain the optimal extraction conditions of SCSE-VBADB for β-agonists, several extractive parameters, including pH values and ionic strength in sample matrix, extraction and desorption time were optimized. Under the optimum conditions, the limits of detection (S/N=3) for the target analytes were 0.007-0.030 μg/L in milk and 0.002-0.011 μg/L in swine urine, respectively. Excellent method reproducibility was achieved in terms of intraday and interday precisions, indicated by the RSDs of both <10.0%, respectively. Finally, the proposed method was successfully used to detect β-agonists in different milk and swine urines samples. Acceptable recoveries ranged from 50.3% to 113% and 50.1% to 92.2% for milk and swine urine samples, respectively; and the RSDs for reproducibility were less than 8.0% for target analytes in all real samples.

Quantification of 1α,25-dihydroxy vitamin D by immunoextraction and liquid chromatography-tandem mass spectrometry

BACKGROUND

1α,25-dihydroxy vitamin D [1,25(OH)(2)D] is the active metabolite of vitamin D. Antibody-based detection methods lack specificity, but when combined with isotope dilution/ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry, immunoextraction provides an attractive method for 1,25(OH)(2)D. We developed a method for simultaneous quantification of 1,25(OH)(2)D(2) and 1,25(OH)(2)D(3) with a 4.6-min instrument cycle time. Results are available 36 h after sample preparation begins.

METHODS

Sample preparation consisted of protein precipitation, immunoextraction with solid-phase anti-1,25(OH)(2)D antibody, and derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione. Analytes were resolved using reversed-phase UPLC and quantified using positive ion electrospray ionization-tandem mass spectrometry. We used hexadeuterated 1,25(OH)(2)D(3) and 1,25(OH)(2)D(2) as internal standards and performed method comparisons against the DiaSorin RIA and an LC-MS/MS method available at a reference laboratory.

RESULTS

1,25(OH)(2)D(3) intraassay and interassay imprecision was 5.6% and 8.0% (120 pmol/L) and 8.7% and 13% (48 pmol/L). Limits of detection and quantification were 1.5 pmol/L and 3.0 pmol/L, respectively. 1,25(OH)(2)D(2) intraassay and interassay imprecision was 8.7% and 11% (186 pmol/L) and 11% and 13% (58 pmol/L). Limits of detection and quantification were both 1.5 pmol/L. Comparison with RIA had a proportional bias of 0.75, constant bias of -4.1, and Pearson correlation (r(2)) of 0.31. Comparison with a reference LC-MS/MS assay had a proportional bias of 0.89, constant bias of 3.7, and r(2) of 0.88.

CONCLUSIONS

Protein precipitation with antibody-based extraction is effective for sample preparation before LC-MS/MS analysis of derivatized 1,25(OH)(2)D. This method appears to have improved specificity over a clinically used RIA with low imprecision and limits of detection.

Ion trap MS/MS of intact testosterone and epitestosterone conjugates--adducts, fragile ions and the advantages of derivatisation

In ion trap mass spectrometry, fragile ions may fragment under the application of resonance ejection during precursor mass isolation, reducing MS/MS spectral intensity. In this study the steroidal epimers testosterone glucuronide (TG) and epitestosterone glucuronide (EG) have been chosen as a model for exploring whether compound structure is linked to ion trap fragility. Both compounds form multiple adducts by ESI-MS, namely protonation, ammonium and sodium, however, the mass spectrum of EG displays a more intense ammonium adduct peak than TG. [TG+NH(4)](+), [EG+NH(4)](+) and [EG+H](+) were found to be fragile ions. To explain the differences in adduct formation and fragility, molecular modelling was employed. Ammonium adduction was localised to the glucuronide ring oxygens and while EG has eight possible adduction sites, only seven were located for TG explaining the increased ammonium adduct abundance with EG. In EG the bond between the steroid and the glucuronide was slightly longer and the oxygen in this bond was more basic than TG. This shows that the EG bond is weaker which may contribute to the fact that [EG+H](+) but not [TG+H](+) is fragile. To investigate whether stability could be restored by chemical means, EG was derivatised with tris(trimethoxyphenyl)phosphonium chloride or methylated on the carboxylic acid and Girard P or methoxylamine on the 3-keto group. Derivatisation of the steroid rather than the glucuronide eliminated fragility and using a charged derivative eliminated adduct formation. This work demonstrates the importance of carefully considering the nature of the derivative and the site of derivatisation.

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.

Development and application of a sol–gel immunosorbent-based method for the determination of isoproturon in surface water

An immunosorbent was fabricated by encapsulation of monoclonal anti-isoproturon antibodies in sol-gel matrix. The immunosorbent-based loading, rinsing and eluting processes were optimized. Based on these optimizations, the sol-gel immunosorbent (SG-IS) selectively extracted isoproturon from an artificial mixture of 68 pesticides. In addition to this high selectivity, the SG-IS proved to be reusable. The SG-IS was combined with liquid chromatography-tandem mass spectrometry (LC-MS-MS) to determine isoproturon in surface water, and the linear range was up to 2.2 microg/l with correlation coefficient higher than 0.99 and relative standard deviation (RSD) lower than 5% (n=8). The limit of quantitation (LOQ) for 25-ml surface water sample was 5 ng/l.

Immunoaffinity solid-phase extraction for pharmaceutical and biomedical trace-analysis—coupling with HPLC and CE—perspectives

Immunoaffinity solid-phase extraction (SPE) technique is based upon a molecular recognition mechanism. The high affinity and the high selectivity of the antigen-antibody interactions allow the specific extraction and the concentration of the analytes of interest in one step. In pharmaceutical and biological fields, where most often matrices are complex and analytes at trace-levels, this approach constitutes a unique tool for fast and solvent-free sample preparation. This review presents a general description of this extraction technique and gives numerous examples of its applications in pharmaceutical and biomedical fields. It emphasizes the on-line coupling with chromatographic and electrophoretic separation techniques and introduces new developments. The future directions, especially with regards to the current development of analytical microsystems, are discussed.

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.

Fast analysis using monolithic columns coupled with high-flow on-line extraction and electrospray mass spectrometric detection for the direct and simultaneous quantitation of multiple components in plasma

In this work, monolithic columns were used as a fast separation tool for multiple-component quantitative liquid chromatography-tandem mass spectrometry (LC-MS-MS) assays of drug candidates in biological fluids. A considerably reduced runtime was achieved while maintaining good chromatographic separations. This significantly improved separation speed demanded higher throughput on sample extraction. To this end, monolithic separations were coupled on-line with high-flow extraction, which allowed for the fast extraction and separation of samples containing multiple analytes. An evaluation of this system was performed using a mixture of fenfluramine, temazepam, oxazepam, and tamoxifen in plasma. A total cycle time of 1.2 min was achieved which included both sample extraction and subsequent monolithic column separation via column switching. A total of over 400 plasma samples were analyzed in less than 10 h. The sensitivity and responses were reproducible throughout the run. The system has been routinely used in the authors' laboratory for high-throughput quantitation of compounds in biological fluids in support of drug discovery programs. The assay for samples from a 9-in-1 dog pharmacokinetic study is shown as an example to demonstrate the capability of this system.

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.

Atmospheric pressure photoionization liquid chromatographic-mass spectrometric determination of idoxifene and its metabolites in human plasma

This paper describes a comparison between atmospheric pressure chemical ionization (APCI) and the recently introduced atmospheric pressure photoionization (APPI) interface for the LC-MS determination of idoxifene and its major metabolite, SB245419 (SB19), in human plasma. The results indicate that analyte response in APPI is highly dependent on the solvent composition, especially to water in the mobile phase. Other parameters investigated are the mobile phase flow-rate, the chemical noise, and signal suppression by matrix interferences. APPI appears to be six to eight times more sensitive than APCI for idoxifene and its SB245419 metabolite; the response for the SB245420 metabolite is considerably better than for APCI conditions, but still not sufficient for trace level pharmacokinetic determinations in human plasma. The LOQ for the parent drug and its major metabolite were 10 and 25 ng/ml, respectively, in human plasma. From post-column infusion experiments we conclude that there is little difference in matrix suppression between APCI and APPI. From these studies we suggest APPI may be an additional tool in pharmaceutical LC-MS applications.

Progress of liquid chromatography-mass spectrometry in clinical and forensic toxicology

The use of liquid chromatography-mass spectrometry (LC-MS) has recently exploded in various analytic fields, including toxicology and therapeutic drug monitoring (although still far behind pharmacokinetics). There is no doubt that LC-MS is currently competing with gas chromatography (GC)-MS for the status of the reference analytic technique in toxicology. This review presents, for the nonspecialist reader, the principles, advantages, and drawbacks of LC-MS systems using atmospheric pressure interfaces. It also gives an overview of the analytic methods for xenobiotics that could be set up with these instruments for clinical or forensic toxicology. In particular, as far as quantitative techniques are concerned, this review tries to underline the large number and variety of drugs or classes of drugs (drugs of abuse, therapeutic drugs) or toxic compounds (e.g., pesticides) that can be readily determined using such instruments, the respective merits of the different ionization sources, and the improvements brought about by tandem MS. It also discusses new applications of LC-MS in the field of toxicology, such as "general unknown" screening procedures and mass spectral libraries using LC-atmospheric pressure ionization (API)-MS or MS-MS, presenting the different solutions proposed to overcome the naturally low fragmentation power of API sources. Finally, the opportunities afforded by the most recent or proposed instrument designs are addressed.

Synthesis and LC characterization of clenbuterol molecularly imprinted polymers

Highly selective non-covalent clenbuterol (CL) imprinted polymers were prepared using methacrylic acid as monomer and ethylene glycol dimethacrylate as cross-linking agent. HPLC experiments with columns packed with this material showed that CL are selectively recognised with respect to all other adrenergic substances studied using a phosphate buffer/acetonitrile eluent. The separation was strongly dependent on pH and the organic/aqueous phase ratio. An important contribution to the recognition mechanism from hydrophobic interactions was found at higher water content. These results demonstrate that a novel family of absorbents with high selectivity for CL was obtained which can be exploited in solid phase extractions or as recognition elements for selective sensors.

Advances in sample preparation in electromigration, chromatographic and mass spectrometric separation methods

The quality of sample preparation is a key factor in determining the success of analysis. While analysis of pharmaceutically important compounds in biological matrixes has driven forward the development of sample clean-up procedures in last 20 years, today's chemists face an additional challenge: sample preparation and analysis of complex biochemical samples for characterization of genotypic or phenotypic information contained in DNA and proteins. This review focuses on various sample pretreatment methods designed to meet the requirements for the analysis of biopolymers and small drugs in complex matrices. We discuss the advances in development of solid-phase extraction (SPE) sorbents, on-line SPE, membrane-based sample preparation, and sample clean-up of biopolymers prior to their analysis by mass spectrometry.

Immunoaffinity solid-phase extraction for the trace-analysis of low-molecular-mass analytes in complex sample matrices

Immunoaffinity solid-phase extraction (SPE) sorbents, so-called immunosorbents (ISs), are based upon molecular recognition using antibodies. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they allow a high degree of molecular selectivity and have shown to be a unique tool in the sample preparation area these last few years. Extraction and clean-up of complex biological and environmental aqueous samples are achieved in the same step and from large volumes when required. Their application to extracts from solid matrixes is solvent-free and more simple than any other clean-up procedure. Single analytes can be targeted, but since an antibody can also bind one or more analytes having structure similar to the one used for its preparation, ISs have been developed for targeting a single analyte and its metabolites. The cross-reactivity was also exploited for developing ISs that could selectively extract a whole class of structurally related compounds. This review describes the current technology used for the synthesis of the ISs, their properties and their field of application. The different parameters governing the antigen-antibody interactions and the solid-phase extraction process are discussed. Emphasis is given to the optimisation of the SPE sequence, especially to the desorption and regeneration steps. The importance of the capacity and its relationship with the analytes recovery and breakthrough volumes is highlighted for class-specific ISs. Multi-class-selective ISs are also presented. Validation studies are reviewed using various certified reference materials. Relevant examples, involving combination with chromatography in both off-line and on-line mode, illustrate the high selectivity provided in various complex matrixes. Miniaturisation is also described, since it allows high throughput of samples.

Beta2-agonist extraction procedures for chromatographic analysis

Normally, different procedures were necessary to prepare sample matrices for chromatographic determination of beta2-agonists. The present review includes sampling, pre-treatment and extraction/purification for urine, plasma, liver, meat, feeds, hair and milk powder, as previous steps for chromatographic analysis of beta2-agonists. Six methodologies were especially revised for extraction/purification namely, liquid-liquid extraction, solid-phase extraction (SPE), matrix solid-phase dispersion, immunoaffinity chromatography, dialysis and supercritical fluid extraction. SPE was discussed in detail and five mechanisms were described: adsorption, apolar, polar, ion-exchange and mixed phase. A brief conclusion in this field was also outlined.

Quantitative analysis of clenbuterol in meat products using liquid chromatography-electrospray ionisation tandem mass spectrometry

A method is presented that allows quantitation of clenbuterol in meat and liver products at the ng/kg level by liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESIMS-MS) using a stable isotopically labeled internal standard. The practical procedure involves acid extraction followed by two solid-phase clean-up steps with C18 and strong cation-exchange (SCX) resins. The typical recovery of the analyte spiked at 0.4 microg/kg in meat and liver samples was at 63+/-7%. Mass spectral acquisition was done in multiple reaction monitoring (MRM) to provide a high degree of sensitivity, achieving a limit of detection and quantitation at 10 and 15 ng/kg, respectively. Two precursor ions at m/z 277 and 279, corresponding to the characteristic isotopic cluster of the two chlorine atoms of clenbuterol, were monitored by LC-ESIMS-MS to provide unambiguous identity of the analyte. Samples of meat and liver of various origins with either incurred residues or spiked with known amounts of clenbuterol were used to validate the method.

Quantitative determination of clenbuterol enantiomers in human plasma by high-performance liquid chromatography using the macrocyclic antibiotic chiral stationary phase teicoplanin

We report a method for the high-performance liquid chromatographic (HPLC) chiral separation of racemic clenbuterol in human plasma. Human plasma was spiked with stock solutions of clenbuterol hydrochloride and practolol as the internal standard. Following a liquid-liquid extraction procedure with 10% (+/-)-2-butanol/isopropyl ether under alkaline conditions, the dried samples were reconstituted in methanol and chromatographed using a macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T(trade mark) (teicoplanin). The mobile phase composition was methanol:acetonitrile (70:30, v/v), containing 0.3% (v/v) acetic acid and 0.2% (v/v) triethylamine. The resulting chromatogram achieved baseline separation for the clenbuterol enantiomers. Calibration curves (peak area ratio vs plasma concentration, n = 10) were constructed for the (-)-R-and (+)-S-clenbuterol enantiomers with a plasma concentration range of 0. 25-10 microM. The correlation coefficient (r) range was 0.99988-0. 99999 (mean = 0.99999). The lowest concentration measured was 0.25 microM. Inter- and intra-assay variation was determined for the lowest, medium and highest plasma concentration (0.25, 2 and 10 microM) by calculating the analytical recoveries with a range of 96-104%. The percentage recoveries for the clenbuterol enantiomers were 88.4-102% over the concentration range used. Detailed methodology is presented.

Solid-phase extraction: method development, sorbents, and coupling with liquid chromatography

The objective of this review is to provide updated information about the most important features of the new solid-phase extraction (SPE) materials, their interaction mode and their potential for modern SPE. First, the recent developments are given in formats, phases, automation, high throughput purpose and set-up of new types of procedures. Emphasis is then placed on the large choice of sorbents for trapping analytes over a wide range of polarities, such as highly cross-linked copolymers, functionalized copolymers, graphitized carbons or some specific n-alkylsilicas. The method development is given which is based on prediction from liquid chromatographic retention data or solvation parameters in order to determine the main parameters of any sequence (type and amount of sorbent, sample volume which can be applied without loss of recovery, composition and volume of the clean-up solution, composition and volume of the desorption solution). Obtaining extracts free from matrix interferences in a few steps--one step when possible--is now included in the development of SPE procedure. New selective phases such as mixed-mode and restricted access matrix sorbents or emerging phases such as immunosorbents or molecularly imprinted polymers are reviewed. Selectivity obtained by combining two sorbents is described with the use of ion-exchange or ion-pair sorbents. Special attention is given to complete automation of the SPE sequence with its on-line coupling with liquid chromatography followed by various detection modes. This represents a fast, modern and reliable approach to trace analysis. Many examples illustrate the various features of modern SPE which are discussed in this review. They have been selected in both biological and environmental areas.