The analysis of beta-agonists by packed-column supercritical fluid chromatography with ultra-violet and atmospheric pressure chemical ionisation mass spectrometric detection

Rapid screening of toxic salbutamol, ractopamine, and clenbuterol in pork sample by high-performance liquid chromatography—UV method

A rapid and simple high-performance liquid chromatography–UV method was developed for the separation and quantification of salbutamol, ractopamine, and clenbuterol in pork. A mixture of acetonitrile–formic acid–ammonium acetate was used as the mobile phase to separate three β-agonists on a C18 column with gradient. The effects of the addition of formic acid and ammonium acetate to mobile phases on the separation of β-agonists were investigated. These additives can greatly improve the resolution and sensitivity. Under the optimized chromatographic condition, this separation does not need extra sample preparation. Complete baseline separation of three β-agonists was achieved in < 20 minutes; the linear range is 0.2–50 μg/L with a correlation coefficient R² value of > 0.99. Excellent method reproducibility was found by intra- and interday precisions with a relative standard deviation of < 3%. The detection limit (S/N = 3) was found to be <0.05 μg/L; this method can be used for routine screening of the β-agonist residues in foods of animal origin before being identified by confirmatory methods.

Different approaches of impregnation for resolution of enantiomers of atenolol, propranolol and salbutamol using Cu(II)-L-amino acid complexes for ligand exchange on commercial thin layer chromatographic plates

Atenolol and propranolol (the beta-blocking agents) and salbutamol (broncho- and vasodilator) were resolved into their enantiomers by adopting different modes of loading/impregnating the Cu(II) complexes of L-proline (L-Pro), L-phenylalanine (L-Phe), L-histidine (L-His), N,N-dimethyl-L-phenylalanine (N,N-Me(2)-L-Phe), and L-tryptophan (L-Trp) on commercial precoated normal phase plates. The three different approaches were (A) using the Cu(II)-L-amino acid complex as chiral mobile phase additive, (B) ascending development of plain commercial plates in the solutions of Cu complex, and (C) using a solution of Cu(II) acetate as mobile phase additive for the commercial TLC plates impregnated with ascending development of plates in the solutions of amino acid. Spots were located using iodine vapour. The results obtained for the three methods have been compared for their efficiency and the issue of involvement of the Cu(II) cation for the best performance of the three methods has been discussed with respect to the same mobile phase. The detection limit is 0.18 microg for each enantiomer.

Development of an analytical method for the determination of beta2-agonist residues in animal tissues by high-performance liquid chromatography with on-line electrogenerated [Cu(HIO6)2]5- -luminol chemiluminescence detection

A novel method was developed for the simultaneous determination of beta2-agonist residues such as terbutaline, salbutamol, and clenbuterol by high-performance liquid chromatography (HPLC) coupled with chemiluminescence (CL) detection. The procedure was based on the enhancement effect of beta2-agonists on the CL reaction between luminol and the complex of trivalent copper and periodate ([Cu(HIO6)2]5-), which was on-line electrogenerated by constant current electrolysis. The HPLC separation used a Nucleosil RP-C18 column (250 mm x 4.6 mm i.d., 5 microm; pore size, 100 A) with a mobile phase consisting of 90% acetonitrile and 10% aqueous ammonium acetate (20 mmol L-1, pH 4.0) at a flow rate of 1.0 mL min-1. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Liver samples were hydrolyzed with beta-glucuronidase followed by a solid-phase extraction procedure using Waters OasisMCX cartridges. Under optimum conditions, the limits of detection at a signal-to-noise ratio of 3 ranged from 0.007 to 0.01 ng g-1 and the limits of quantification at a signal-to-noise ratio of 10 ranged from 0.023 to 0.033 ng g-1 for three beta2-agonists. The relative standard deviations (RSDs) of intra- and interday precision were below 4.5%. The average recoveries for beta2-agonists (spiked at the levels of 0.05-5.0 ng g-1) in pig liver ranged from 84 to 110%, and the RSDs of the quantitative results were from 1.6 to 7.2%. The proposed method was successfully applied to the determination of beta2-agonist residues in pig liver samples.

Supercritical fluid chromatography/tandem mass spectrometric method for analysis of pharmaceutical compounds in metabolic stability samples

Packed-column supercritical fluid chromatography (pSFC) coupled to an atmospheric pressure chemical ionization (APCI) source and a tandem mass spectrometer (MS/MS) for rapid and simultaneous determination of clozapine, ondansetron, tolbutamide and primidone in in vitro samples was developed in support of metabolic stability experiments. The effects of the eluent flow-rate and composition as well as the nebulizer temperatures on the ionization efficiency of the analytes in positive ion mode under normal phase pSFC conditions were studied. The metabolic stability of the test drug components through microsomal incubation by the proposed pSFC-APCI/MS/MS approaches requiring approximately 1 min per samples were evaluated with respect to specificity, durability and accuracy. These metabolic stability results obtained by pSFC-MS/MS methods are in a good agreement with those obtained by fast high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method.

Supercritical Fluid Chromatography−Tandem Mass Spectrometry for the Enantioselective Determination of Propranolol and Pindolol in Mouse Blood by Serial Sampling

Packed-column supercritical fluid chromatography (pSFC) coupled to an atmospheric pressure chemical ionization (APCI) source and a tandem mass spectrometer (MS/MS) with minimum sample pretreatment was explored for the rapid and enantioselective determination of (R,S)-propranolol in mouse blood. Serial bleeding of mice is advantageous for the reduction of animal usage, dosing errors, and animal-to-animal variation. The effects of the eluent flow rate and composition as well as the nebulizer temperatures on the ionization efficiency of racemic propranolol and pindolol as model compounds in the positive ion mode under pSFC conditions were studied. The fundamental parameters on the proposed hyphenated system such as matrix ionization suppression and chromatographic performances were investigated in improving sensitivity and enantiomeric separation for the detection of the analytes. The proposed chiral pSFC-APCI/MS/MS approach requiring approximately 3 min/sample for the determination of (R,S)-propranolol at a low nanogram per milliliter region was partially validated with respect to specificity, linearity, reproducibility, and accuracy and was applied to support a pharmacokinetic study.

Study of the elution mechanism of sodium aryl sulfonates on bare silica and a cyano bonded phase with methanol-modified carbon dioxide containing an ionic additive

The elution mechanism of sodium sulfonates on both Deltabond cyanopropyl and bare silica stationary phases with an isocratic mobile phase composed of methanol-modified CO2 wherein an ammonium salt additive was dissolved in the methanol has been studied. The presence of the additive was crucial concerning elution of the sulfonate salts. Solid state 29silicon nuclear magnetic resonance spectroscopy provided some insight concerning the interaction of the mobile phase additive with the silica-based stationary phase. Computational calculations concerning the charge distribution on various ammonium salts were performed in an effort to explain the elution behavior. Ammonium ions are believed to deactivate available silanol sites on both phases. In addition, ammonium ion is speculated to interact with the cyano groups on the bonded phase. For concentrations of additive greater than 2 mM, stationary phase coverage of ammonium ion is anticipated to exceed one monolayer for both bare and bonded silica. The acetate counter-ion is thought to facilitate elution of the anionic sulfonates from the positively charged stationary phase in a pseudo ion exchange mechanism.

Effect of ionic additives on the elution of sodium aryl sulfonates in supercritical fluid chromatography

Addition of a small amount of polar solvent (i.e., modifier) to CO2 in packed column supercritical fluid chromatography (SFC) has shown major improvements in both polar analyte solubility and interaction of the polar analyte with the stationary phase. Recently, the addition of an ionic component (i.e., additive) to the primary modifier by one of us has been shown to extend even further the application of SFC to polar analytes. In this work, the effect of various ionic additives on the elution of ionic compounds, such as sodium 4-dodecylbenzene sulfonate and sodium 4-octylbenene sulfonate, has been studied. The additives were lithium acetate, ammonium acetate, tetramethylammonium acetate, tetrabutylammonium acetate, and ammonium chloride dissolved in methanol. Three stationary phases with different degrees of deactivation were considered: conventional cyanopropyl, deltabond cyanopropyl, and bare silica. The effect of additive concentration and additive functionality on analyte retention was investigated. Sodium 4-dodecylbenzene sulfonate was successfully eluted using all the additives with good peak shape under isocratic/isobaric/isothermal conditions. Different additives, however, yielded different retention times and in some cases different peak shapes.

Chiral supercritical fluid chromatography/tandem mass spectrometry for the simultaneous determination of pindolol and propranolol in metabolic stability samples

A chiral packed-column supercritical fluid chromatographic (pSFC) system coupled to tandem mass spectrometer (MS/MS) for the rapid measurements of (R,S)-propranolol and (+/-)-pindolol in metabolic stability samples was developed. The effects of the eluent flow rates and compositions, as well as of the nebulizer temperature, on the chromatographic performance and the ionization efficiency of the analytes in positive ion mode under pSFC conditions were studied. The ionization mechanism of the analytes in the CO2/methanol atmospheric pressure chemical ionization (APCI) environments with or without the use of an additive was studied. The chiral pSFC-APCI-MS/MS approach requiring approximately 2 min per sample was applied for the simultaneous determination of two pairs of racemic drugs in in vitro samples at low nanogram per milliliter concentrations.

Spectrophotometric determination of fenoterol hydrobromide in pure form and dosage forms

A sensitive and rapid spectrophotometric procedure has been investigated for the determination of fenoterol either per se or in pharmaceutical preparations. The proposed procedure is based on the reaction between the drug and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) at pH 7.2, using borate buffer, to produce a yellow adduct. The latter has maximum absorbance at 400 nm and obeys Beer's law within the concentration range 5-30 microg/ml. Regression analysis of the calibration data showed a good correlation coefficient (r=0.9996) with minimum detection limit of 0.24 microg/ml (6.2 x 10(-8) M). The proposed procedure has been successfully applied to the determination of this drug in its tablets and in syrup, the mean percent recoveries were 97.45+/-0.59 and 98.7+/-0.64%, respectively. The results obtained are in good agreement with those given using a reference method. The pharmaceutical additives other than active ingredient did not interfere. A proposal of the reaction pathway has been postulated.

Recent advances in the application of mass spectrometry in food-related analysis

A review is presented on recent applications of mass spectrometry (MS)-based techniques for the analysis of compounds of food concern. Substances discussed are naturally occurring compounds in food products such as lipids, oligosaccharides, proteins, vitamins, flavonoids and related substances, phenolic compounds and aroma compounds. Among xenobiotics, applications of MS techniques for the analysis of pesticides, drug residues, toxins, amines and migrants from packaging are overviewed. Advances in the analysis of trace metals of nutritional and toxicological interest by MS with inductively coupled plasma (ICP) source are presented. The main features of mass spectrometry combined with separation instruments are discussed in food-related analysis. Examples of mass spectrometry and tandem MS (MS-MS) are provided. The development and application of matrix-assisted laser desorption ionization (MALDI) and electrospray (ESI) to the analysis of peptides and proteins in food is discussed. This survey will attempt to cover the state-of-the-art up from 1999 to 2001.

Development of a packed-column supercritical fluid chromatography/atmospheric pressure chemical-ionisation mass spectrometric technique for the analysis of atropine

A packed-column supercritical fluid chromatography/atmospheric pressure chemical-ionisation mass spectrometry (pSFC-APCI/MS) method has been developed for the determination of atropine from Atropa belladonna L extracts. The technique does not require any kind of derivatisation prior to the analysis. The optimum conditions were studied by using the pure substance in methanol (MeOH). All samples were simply dissolved in MeOH and injected into the mobile phase. Detection was achieved by using mass spectrometry (MS) with atmospheric pressure chemical ionisation (APCI). Terbutaline was used as an internal standard for the determination of the analytical reproducibility. The supercritical carbon dioxide (scCO(2)) mobile phase was modified by 15% MeOH containing 0.5% trifluoroacetic acid (TFAA) and 0.5% diethylamine (DEA) additives. Concentrations of atropine were determined with a relative standard deviation of less than 1% by the pSFC-APCI/MS procedure for a sample containing atropine and terbutaline. The correlation coefficient was 0.997 and detection limit 700 pg. The absolute retention time was 9.87 min with a standard deviation of 5.2x10(-3) min and a relative standard deviation of 0.61% with respect to terbutaline.

Tuning of mobile and stationary phase polarity for the separation of polar compounds by SFC

The separation of polar compounds by supercritical-fluid chromatography (SFC) is reviewed. New developments in mobile and stationary phase tuning are reviewed for packed and packed capillary SFC. In terms of mobile phase polarity adjustment, new pure and multiple component fluids are presented. The approach of tuning the polarity of the stationary phase as a way of increasing the range of polar compounds analyzed by SFC using pure CO(2) is discussed using either silica-based or new materials as stationary phase. Chiral, liquid crystal and polymer-based stationary phases coated on particles are widely covered in this review as an interesting approach to separate polar compounds avoiding the major drawbacks associated to the use of modifiers in SFC.

Exposure to airborne dust contaminated with pesticide in the Aral Sea region

The Aral Sea region is one of the world's foremost ecological disaster zones and there is increasing local concern for the health of millions of people living in this region. We have found that dust deposition rates across eastern Turkmenistan are among the highest in the world and that the dust is contaminated with pesticide.