High-performance liquid chromatography using continuous on-line post-elution photoirradiation with subsequent diode-array UV or thermospray mass spectrometry detection

Determination of photoirradiated tetracyclines in water by high-performance liquid chromatography with chemiluminescence detection based reaction of rhodamine B with cerium (IV)

A simple, selective and sensitive method has been developed for the simultaneous determination of tetracycline, oxytetracycline, chlorotetracycline, demeclocycline, doxycycline and meclocycline based on reversed-phase high-performance liquid chromatography with chemiluminescence detection. The procedure was based on the chemiluminescent enhancement by photoirradiated tetracyclines of the cerium (IV)-rhodamine B system in sulphuric acid medium. The six tetracyclines were separated on an Aquasil-C18 column with a gradient elution using a mixture of acetonitrile and 0.1 mol L(-1) phosphate buffer as mobile phase, photoderivatized using a photoreactor consisting of a tube reactor coil of PFA and a 8W Xenon lamp. Under the optimized conditions, the method was validated with respect to linearity, precision, limits of detection and quantification and accuracy. The relative standard deviation (RSD) on intra-day precision was below 10% and detection limits ranged between 0.12 and 0.34 microg L(-1). The proposed method has been successfully applied to the determination of tetracyclines in surface water samples. A possible mechanism of the chemiluminescence in the system is discussed.

Column switching liquid chromatography and post-column photochemically fluorescence detection to determine imidacloprid and 6-chloronicotinic acid in honeybees

The determination of imidacloprid and its main metabolite (6-chloronicotinic acid) in honeybees was performed by liquid chromatography with post-column photochemical derivatisation in alkaline medium and fluorescence detection. The compounds were extracted from honeybees with acetone under ultrasound conditions prior to liquid-liquid partition with dichloromethane. The separation of extract components was performed using a 50 mm x 4.6 mm i.d. short column packed with 5 microm Aquasil C(18) using an acetonitrile:water gradient program as mobile phase. Injection of samples in 0.1 mol L(-1) H(3)PO(4)/KH(2)PO(4) buffer solution (pH 3) improved the chromatographic separation between the most polar components of matrix and the 6-chloronicotinic acid. Matrix components were removed to waste using an on-line clean-up method previously to post-column reaction. Limits of quantification were 0.3 and 5.0 microg L(-1) (corresponding to 1.2 and 20.0 microg kg(-1) in the honeybee sample) for imidacloprid and 6-chloronicotinic acid, respectively. The recovery was ranged from 80.2 to 91.7% with a relative standard deviation lower than 9.0%.

New method for the photo-chemiluminometric determination of benzoylurea insecticides based on acetonitrile chemiluminescence

The viability of tandem photochemical reaction-chemiluminescence detection has been studied for the determination of five benzoylurea insecticides, namely, diflubenzuron, triflumuron, hexaflumuron, lufenuron and flufenoxuron. The 'on-line' photochemical reaction of benzoylurea pesticides provides an enhanced chemiluminescence response of the pesticides during their oxidation by potassium hexacyanoferrate(III) and sodium hydroxide, whose signal increases with the percentage of acetonitrile in the reaction medium. The determination was performed using a photoreactor consisting of a PFA (perfluoroalkoxy) tube reactor coil (5 mx1.6-mm O.D. and 0.8-mm I.D.) and an 8-W xenon lamp. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mmx4.6 mm, 5-microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactants as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation of intra-day precision below 10% and detection limits between 0.012 and 0.18 microg mL-1, according to the compound. The proposed method has been successfully applied to the determination of benzoylureas in cucumber with good results.

Determination of nine pyrethroid insecticides by high-performance liquid chromatography with post-column photoderivatization and detection based on acetonitrile chemiluminescence

An HPLC method was developed to determine pyrethroids, including fenpropathrin, beta-cyfluthrin, lambda-cyhalothrin, deltamethrin, fenvalerate, permethrin, acrinathrin, tau-fluvalinate, and bifenthrin, by coupling HPLC, post-column irradiation with UV light and chemiluminescence detection of the resulting photoproducts. It is based on the observation that photolyzed pyrethroids take part in a chemiluminescent reaction in presence of K3Fe(CN)6 and NaOH, whose signal increases with the percentage of acetonitrile in the reaction medium. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mm x 4.6 mm, 5 microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactives as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation on intra-day precision below 10% and detection limits between 0.013 and 0.049 microg mL(-1), according to the compound. The proposed method has been successfully applied to the determination of pyrethroids in tomato with good results.

Psychoactive tryptamines from basidiomycetes

The review lists natural sources, i.e. strains and species of fungi producing predominantly psychoactive tryptamines (indolealkylamines), their chemical structure and properties, toxic effects on the man and psychic symptoms of intoxication. It describes the biosynthesis and production of some tryptamines by the mycelial culture of Psilocybe bohemica Sebek, a survey of methods for their analysis and isolation. It evaluates the worldwide use and abuse of psychoactive fungi as sources of drugs in general and in the Czechia in particular during the last two and a half decades.

Liquid chromatography-mass spectrometry in forensic toxicology

Liquid chromatography-mass spectrometry has evolved from a topic of mainly research interest into a routinely usable tool in various application fields. With the advent of new ionization approaches, especially atmospheric pressure, the technique has established itself firmly in many areas of research. Although many applications prove that LC-MS is a valuable complementary analytical tool to GC-MS and has the potential to largely extend the application field of mass spectrometry to hitherto "MS-phobic" molecules, we must recognize that the use of LC-MS in forensic toxicology remains relatively rare. This rarity is all the more surprising because forensic toxicologists find themselves often confronted with the daunting task of actually searching for evidence materials on a scientific basis without any indication of the direction in which to search. Through the years, mass spectrometry, mainly in the GC-MS form, has gained a leading role in the way such quandaries are tackled. The advent of robust, bioanalytically compatible combinations of liquid chromatographic separation with mass spectrometric detection really opens new perspectives in terms of mass spectrometric identification of difficult molecules (e.g., polar metabolites) or biopolymers with toxicological relevance, high throughput, and versatility. Of course, analytical toxicologists are generally mass spectrometry users rather than mass spectrometrists, and this difference certainly explains the slow start of LC-MS in this field. Nevertheless, some valuable applications have been published, and it seems that the introduction of the more universal atmospheric pressure ionization interfaces really has boosted interests. This review presents an overview of what has been realized in forensic toxicological LC-MS. After a short introduction into LC-MS interfacing operational characteristics (or limitations), it covers applications that range from illicit drugs to often abused prescription medicines and some natural poisons. As such, we hope it can act as an appetizer to those involved in forensic toxicology but still hesitating to invest in LC-MS.

Liquid chromatography/mass spectrometry for timely response in regulatory analyses: identification of pentobarbital in dog food

A limited liquid chromatography/mass spectrometry (LC/ MS) data set was acquired under conditions which called for timely response without benefit of a fully developed method. Quality assurance elements verified that an LC/ MS procedure developed in a short-time was sufficiently under control to meet its purpose. LC/MS was used to rule out a potential problem with a gas chromatography (GC)/MS method that had been developed for regulatory purposes. The LC/MS data set showed that signals identified by GC/MS as diagnostic of pentobarbital (PB) were not artifacts of derivatization or GC analysis. Samples of dry dog food identified by GC/MS as containing PB were also shown by LC/MS to contain PB. The LC/MS method would not be recommended as a substitute for GC/MS, primarily because of poorer sensitivity. Although the data set is limited, and justifiably represents only the starting point for conventional method development, the purpose at hand was served adequately. This work demonstrates the utility of LC/MS for rapid regulatory response, provided there is a framework of quality assurance checks.

The role of liquid chromatography-mass spectrometry in the determination of heroin and related opioids in biological fluids

The opioid most commonly sold in the illicit market is heroin. This substance, classified as an analgesic narcotic drug, has an extremely short half-life, and it is rapidly metabolized to 6-monoacetyl-morphine and further to morphine. Morphine is principally metabolized by conjugation to morphine-3 and morphine-6 glucuronides. Morphine itself is a potent analgesic that is frequently used in the pharmacological intervention of cancer pain. The toxicological and clinical evaluation of heroin and morphine have stimulated pharmacokinetic studies in human and animal models. Although a number of methods exist to determine opiates and their metabolites, liquid chromatography (LC) appears to be the technique that can separate without any pretreatment the lipophilic and the hydrophilic analytes of the complete metabolic profile of heroin and/or morphine. Moreover, mass spectrometry (MS) used as a detector for liquid chromatography is unique, because it offers universality and selectivity. Furthermore, efforts have been made to develop LC/MS interfaces that could overcome the previous problem of poor sensitivity. For this reason, in recent years LC combined with MS has been applied to the analysis of opiates--parent drugs and metabolites--in biological fluids. This article reviews the existing literature on the determination, using liquid chromatography coupled to mass spectrometry, of opiate metabolites found in different biological matrices after the administration of the parent compounds.

Analysis of psilocybin and psilocin in Psilocybe subcubensis Guzmán by ion mobility spectrometry and gas chromatography-mass spectrometry

A new method has been developed for the rapid analysis of psilocybin and/or psilocin in fungus material using ion mobility spectrometry. Quantitative analysis was performed by gas chromatography-mass spectrometry after a simple one-step extraction involving homogenization of the dried fruit bodies of fungi in chloroform and derivatization with MSTFA. The proposed methods resulted in rapid procedures useful in analyzing psychotropic fungi for psilocybin and psilocin.

Investigation of photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography-electrospray ionization tandem mass spectrometry system. Application to trace and confirmatory analyses in food samples

The photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography-electrospray ionization mass spectrometer (LC-hv-MS) was investigated. This paper describes the application of LC-hv-MS, in combination with tandem mass spectrometry (MS-MS), to identification of phototransformation products and to the establishment of possible photolytic pathways of pesticides. In addition, the applicability of LC-hv-MS as an alternative to LC-MS-MS, for trace and confirmatory multiresidue analysis in food samples was investigated. To demonstrate the potential of this technique, a series of N-heterocyclic compounds, phenylureas and carbamates, was studied. Several parameters, such as irradiation time and nature of photosensitizers, were investigated, and their impact on the photolytic transformation is presented here. The technique's versatility is also exhibited by using it for identification of triazine isomers, and for detection of pesticide residues in food sample extracts. Illustrative applications for analysis in lettuce and blueberry extracts are described.

Labeling reactions applicable to chromatography and electrophoresis of minute amounts of proteins

Chromatography and electrophoresis have become extremely valuable and important methods for the separation, purification, detection and analysis of biopolymers and HPLC/HPCE may become the premier, preferable approaches for both qualitative and quantitative analyses of most proteins, especially from recombinant materials. This includes smaller peptides, polypeptides, proteins, antibodies and all types of protein or antibody-conjugates (antibody-enzyme, protein-fluorescent probe, antibody-drug and so forth). This entire Topical Issue of Journal of Chromatography emphasizes the application of chromatography and electrophoresis to protein analysis. This particular review deals with approaches to the selective tagging or labeling of proteins at trace (minute) levels, again using either chromatography or electrophoresis, with the emphasis on modern HPLC/HPCE methods and approaches. We discuss here both pre- and post-column labeling methods and reagents, techniques for realizing selective labeling of proteins or antibodies, applicable approaches to protein preconcentration in both HPLC and HPCE areas and in general, methods for improving (lowering) detection limits for proteins utilizing chemical or physical derivatization and/or preconcentration techniques. There are really two major goals or emphases in that which follows: (1) methods for selective labeling of proteins prior to or after HPLC/HPCE and (2) labeling of proteins at trace levels for improved separation-detection and lowered detection limits. We discuss here a large number of specific references related to both pre- and post-column/capillary derivatizations for proteins, as well as methods for improved detectability in both HPLC and HPCE by, for example, analyte preconcentration on a solid-phase extractor or membrane support, capillary isotachophoresis and other methods. Selective reactions or derivatizations on proteins refers to the ability to tag the protein at specific (e.g. reactive amino sites) in a controlled manner, with the products having the same number of tags all at the very same site or sites. The products are all the same species, having the same number of tags at the same locations on the protein. Selective reactions can also refer to the idea of tagging all of the protein sample at only a single, same site or at all available sites, homogeneously.

Determination of fenbufen and its metabolites in serum by reversed-phase high-performance liquid chromatography using solid-phase extraction and on-line post-column ultraviolet irradiation and fluorescence detection

An improved analytical method for the detection and quantification of fenbufen and its two major metabolites is described. The assay consists of reversed-phase high-performance liquid chromatography and post-column irradiation with ultraviolet light and fluorescence detection. A highly selective chromatography separation was established on a cyanopropyl column at ambient temperature with a flow-rate of 0.5 ml/min. The analytes of interest were isolated from serum using a Bond-Elut CIN column with high recovery and selectivity. The fluorescence response of all three analytes upon UV irradiation was investigated. The post-column UV irradiation was optimized and the effect of irradiation time on the fluorescence response was determined for all three analytes. The detection limits were 10 ng/ml for each analyte using 1 ml of serum. Linear calibration curves from 50 to 375 ng/ml for all three analytes show coefficients of determination of 0.99. Precision and accuracy of the method were within 3.9-6.5 and 5.1-7.4% for fenbufen, 3.5-6.4 and 4.9-6.3% for metabolite II (expressed as lactone III) and 5.4-7.4 and 2.6-7.4% for metabolite IV, respectively.

In-depth chromatographic analyses of illicit cocaine and its precursor, coca leaves

Chromatographic methodology used for the in-depth alkaloid analyses of coca leaves and for the characterization of alkaloidal impurities and manufacturing by-products in illicit refined cocaine samples is reviewed. This includes liquid-liquid partition and liquid-solid adsorption column chromatography, packed- and capillary-column gas chromatography with flame-ionization, electron-capture, nitrogen-phosphorous and mass spectrometric detection, and high-performance liquid chromatography with ultraviolet detection. The rationale supporting the presence and determination of processing impurities/by-products in cocaine samples is discussed, and chromatographic methodology used for the development of drug impurity signature profiles is presented.