Recent developments of enantioseparation techniques for adrenergic drugs using liquid chromatography and capillary electrophoresis: a review

This review provides the achievements of enantioseparation of adrenergic drugs and application of these methods in clinical and pharmaceutical analysis. The adrenergic agonist and antagonist drugs are analyzed in the direct and indirect modes by liquid chromatography (LC) and capillary electrophoresis (CE). Other chromatographic enantioseparation methods including super- and sub-critical fluid chromatography (SFC), and capillary electrochromatography (CEC) are presented likewise to analyse the cited compounds. The different separation processes for these drugs are briefly discussed and some applications are presented.     

Inhibition of Differentiation in Dictyostelium discoideum by Anti-Inflammatory Drugs

Evidence is presented that a panel of non-steroidal anti-inflammatory drugs inhibit both developmental gene expression and terminal cell differentiation in the slime mold Dictyostelium discoideum. Incubation of developing cells with a number of these drugs also prevents the accumulation in the cells of two lipid species which have chromatographic properties similar to authentic eicosanoids. The results raise the possibility that Dicytostelium cells synthesize eicosanoid-like lipids which are required for normal development.     

Simplified method for monitoring tricyclic antidepressant therapy using gas—liquid chromatography with nitrogen detection

A simplified gas chromatographic method for the rapid measurement of tricyclic anti-depressant drugs in plasma using a nitrogen-sensitive detector is described. All drugs are extracted and chromatographed under identical conditions. Tertiary amines are separated from their secondary amine metabolites, which are determined simultaneously without the need for derivatisation. The lower limit of accurate determination for most drugs is 10 μg/1.

The method has been applied to the routine measurement of amitriptyline and nortriptyline in plasma from patients receiving antidepressant treatment. Large and important interindividual differences in plasma concentrations in the patients investigated have been found, and the significance of these results is discussed.     

Investigation of the enantioselectivity and enantiomeric elution order of some piperidine-2,6-dione drugs on chiralcel OD column

The enantioselectivity and enantiomeric separation of five racemic piperidine-2,6-dione compounds, on the cellulose tris(3,5-dimethylphenyl carbamate) chiral stationary phase Chiralcel OD-CSP were investigated under the same chromatographic conditions. This class of drugs includes glutethimide, aminoglutethimide, cyclohexylaminoglutethimide, pyridoglutethimide, and phenglutarimide. The results revealed that chiral recognition and the binding sites of these drugs on the Chiralcel OD column are similar, regardless of the absolute configuration of the individual enantiomers. A possible chiral recognition mechanism(s) for this class of drugs and the CSP is presented. © 1994 Wiley-Liss, Inc.     

Chromatographic screening techniques in systematic toxicological analysis

A review of techniques used to screen biological specimens for the presence of drugs was conducted with particular reference to systematic toxicological analysis. Extraction systems of both the liquid–liquid and solid-phase type show little apparent difference in their relative ability to extract a range of drugs according to their physio-chemical properties, although mixed-phase SPE extraction is a preferred technique for GC-based applications, and liquid–liquid were preferred for HPLC-based applications. No one chromatographic system has been shown to be capable of detecting a full range of common drugs of abuse, and common ethical drugs, hence two or more assays are required for laboratories wishing to cover a reasonably comprehensive range of drugs of toxicological significance. While immunoassays are invariably used to screen for drugs of abuse, chromatographic systems relying on derivatization and capable of extracting both acidic and basic drugs would be capable of screening a limited range of targeted drugs. Drugs most difficult to detect in systematic toxicological analysis include LSD, psilocin, THC and its metabolites, fentanyl and its designer derivatives, some potent opiates, potent benzodiazepines and some potent neuroleptics, many of the newer anti-convulsants, alkaloids colchicine, amantins, aflatoxins, antineoplastics, coumarin-based anti-coagulants, and a number of cardiovascular drugs. The widespread use of LC–MS and LC–MS–MS for specific drug detection and the emergence of capillary electrophoresis linked to MS and MS–MS provide an exciting possibility for the future to increase the range of drugs detected in any one chromatographic screening system.     

Chromatographic analysis of lipoic acid and related compounds

The analysis of lipoic acid and related compounds, such as its reduced form dihydrolipoic acid, its amide form lipoamide and other analogues, in biological and food samples is important in biochemistry, nutritional and clinical chemistry. This review summarizes the chromatographic methods for the determination of lipoic acid and related compounds, and their applications to various samples such as bacteria, tissues, drugs and food. Gas chromatographic methods with flame ionization detection and flame photometric detection are commonly used for the quantification of lipoic acid present as its protein-bound form, after acid or base hydrolysis of these samples. High-performance liquid chromatographic methods with ultraviolet, fluorescence and electrochemical detection are mainly used for the determination of free lipoic acid and related compounds, such as dihydrolipoic acid, lipoamide and other analogues. Moreover, gas chromatography–mass spectrometry and capillary electrophoresis methods are also developed.     

Drug delivery systems: polymers and drugs monitored by capillary electromigration methods

In this paper, different electromigration methods used to monitor drugs and polymers released from drug delivery systems are reviewed. First, an introduction to the most typical arrangements used as drug delivery systems (e.g., polymer-drug covalent conjugates, membrane or matrix-based devices) is presented. Next, the principles of different capillary electromigration procedures are discussed, followed by a revision on the different procedures employed to monitor the release of drugs and the degradation or solubilization of the polymeric matrices from drug delivery systems during both in vitro and in vivo assays. A critical comparison between these capillary electrophoretic methods and the more common chromatographic methods employed to analyze drugs and polymers from drug delivery systems is presented. Finally, future outlooks of these electromigration procedures in the controlled release field are discussed.     

Simultaneous solid-phase extraction and chromatographic analysis of morphine and hydromorphone in plasma by high-performance liquid chromatography with electrochemical detection

High-performance liquid chromatography has become an important analytical tool for the quantitation of opioid drugs. Using solid-phase extraction and coulometric electrochemical detection, we have developed a chromatographic method for the simultaneous measurement of morphine and hydromorphone which is both sensitive and specific. Using 1 ml of plasma, intra-assay and inter-assay data show that the detection limit for accurate quantitation of these compounds is about 1.2 ng/ml (coefficient of variation 11.6%) for morphine and 2.5 ng/ml (coefficient of variation 10.5%) for hydromorphone. The method is simple and readily adaptable to most pharmacokinetic studies and toxic screens involving these drugs.     

Application of high-performance liquid chromatography for recognition of covalent nucleic acid modification with anticancer drugs

Covalent modification of DNA by antineoplastic agents represents a potent biochemical lesion which can play a major role in drug mechanism of action. The ability to measure levels of DNA covalent modifications in target cells in vivo may, therefore, be seen as the ultimate form of therapeutic drug monitoring. Additionally, elucidation of the structure of critical DNA adducts and definition of their role in tumour cell cytotoxicity will provide more selective targets for rational drug design of new cancer chemotherapeutic agents. High-performance liquid chromatography has contributed significantly to all these areas. In vivo levels of nucleic acid covalent modifications are in the range of 1 in 10⁵–10⁸ nucleotides precluding the use of conventional high-performance liquid chromatographic detection methods. Several classes of natural product anticancer drugs have been shown to bond covalently to nucleic acids under optimal laboratory conditions. These have proved more accessible to high-performance liquid chromatographic analysis because of their lipophilicity and strong UV chromophores. However, the majority of experimental evidence to date suggests that with the exception of mitomycin C and morpholino-anthracyclines these compounds do not exert their primary mechanism of action through nucleic acid covalent modification. DNA adducts of alkylating and platinating agents are more difficult to detect by high-performance liquid chromatography and can be chemically unstable. These compounds interact with DNA on the basis of chemical kinetics. Thus, the principle sites of attachment tend to be with the most nucleophilic base (guanine) at its most reactive centre (N-7 position). Limited in vivo high-performance liquid chromatographic studies with all classes of anticancer drugs indicate a much more complex pattern of adductation than would have been anticipated from in vitro studies alone. Some of these differences are probably due to methodological artefacts but these studies stress the need for sensitive detection methods and reliable sample preparation (nucleic acid extraction and digestion techniques) when attempting to determine nucleic acid covalent modifications by anticancer drugs.     

Analysis of tricyclic antidepressant drugs by gas chromatography using nitrogen-selective detection with packed and capillary columns

A gas chromatographic method using either a conventional packed column (3% SP-2250) or a capillary column (SE-30) for the measurement of therapeutic plasma concentrations of tricyclic antidepressant drugs and their demethylated metabolites is described. The technique is based on a simple hexane extraction of drug from alkalinized plasma followed by derivatization with heptafluorobutyric anhydride for the measurement of demethylated compounds. Subsequently, parent drugs and derivatives are chromatographed and detected using a nitrogen-selective detector. A comparison of the results using both types of chromatographic systems is discussed.     

Determination of antiepileptic drugs in biological material

Current analytical methodologies applied to the determination of antiepileptic drugs in biological material are reviewed. The role of chromatographic techniques is emphasized. Special attention is focused on new chemical entities as well as current trends such as high-speed liquid chromatographic techniques, hyphenated techniques and electrochromatography techniques. A review with 542 references.     

Analytical surveillance of emerging drugs of abuse and drug formulations

Uncontrolled recreational drugs are proliferating in number and variety. Effects of long-term use are unknown, and regulation is problematic, as efforts to control one chemical often lead to several other structural analogs. Advanced analytical instrumentation and methods are continuing to be developed to identify drugs, chemical constituents of products, and drug substances and metabolites in biological fluids. Several mass spectrometry based approaches appear promising, particularly those that involve high resolution chromatographic and mass spectrometric methods that allow unbiased data acquisition and sophisticated data interrogation. Several of these techniques are shown to facilitate both targeted and broad spectrum analyses, the latter of which are often of particular benefit when dealing with misleadingly labeled products or assessing a biological matrix for illicit drugs and metabolites. The development and application of novel analytical approaches such as these will help to assess the nature and degree of exposure and risk and, where necessary, inform forensics and facilitate implementation of specific regulation and control measures.     

Poly(ethyleneglycol) column for the determination of acetaminophen,phenylephrine and chlorpheniramine in pharmaceutical formulations

New polar reversed-phase stationary phases in HPLC provide specific selectivities which can help to solve traditional chromatographic problems related to the development of chromatographic methods with widely different retention times for the sample components. One such case is the analysis of pharmaceutical formulations against the common cold. Acetaminophen, phenylephrine and chlorpheniramine, compounds with different polarities, are frequently associated in these drugs. An isocratic and rapid HPLC method for the simultaneous determination of the three compounds, acetaminophen, phenylephrine and chlorpheniramine, in capsules as pharmaceutical formulations, including the separation of impurities (4-aminophenol and 4-chloracetanilide) and excipients, has been developed and validated. The final chromatographic conditions employed a Supelco Discovery HS PEG column poly(ethyleneglycol) 15x0.46 cm, 5 microm. The mobile phase was 20 mM phosphate buffer, pH 7.0-acetonitrile (90:10, v/v) at a flow-rate of 1 ml/min. UV detection was performed at 215 nm for all the compounds except acetaminophen, which was measured at 310 nm. Validation parameters permit us to consider this method suitable.     

Reversed-phase,ion-pair liquid chromatography of quaternary ammonium compounds : Determination of pyridostigmine,neostigmine and edrophonium in biological fluids

A reversed-phase, ion-pair liquid chromatographic method for the quantitative determination of quaternary acetylcholinesterase inhibitors is described. The method uses an ion-pair extraction to isolate the drugs from biological material prior to liquid chromatographic separation and online UV detection at 214 nm. Quantitation down to 5 ng/ml and within-day precision with coefficient of variation (C.V.) of 1.5% (n=10, $\text{x}$ = 100 ng/ml) for neostigmine, C.V., 1.7% (n=10, $\text{x}$ = 80 ng/ml) for pyridostigmine and C.V., 1.5% (n=10, $\text{x}$ = 100 ng/ml) for edrophonium have been achieved. The assay was designed for pharmacokinetic studies of these drugs in anesthetized patients.     

Quantitative liquid chromatographic analysis of anthracyclines in biological fluids

Anthracyclines are amongst the most widely used drugs in oncology, being part of the treatment regimen in most patients receiving systemic chemotherapy. This review provides a comprehensive summary of the sample preparation techniques and chromatographic methods that have been developed during the last two decades for the analysis of the 4 most administered anthracyclines, doxorubicin, epirubicin, daunorubicin and idarubicin in plasma, serum, saliva or urine, within the context of clinical and pharmacokinetic studies or for assessing occupational exposure. Following deproteinization, liquid-liquid extraction, solid phase extraction or a combination of these techniques, the vast majority of methods utilizes reversed-phase C18 stationary phases for liquid chromatographic separation, followed by fluorescence detection, or, more recently, tandem mass spectrometric detection. Some pros and cons of the different techniques are addressed, in addition to potential pitfalls that may be encountered in the analysis of this class of compounds.     

Rapid thin-layer chromatographic method for the simultaneous determination of carbamazepine,diphenylhydantoin, mephenytoin,phenobarbital and primidone in serum

A thin-layer chromatographic method for the simultaneous determination of five anticonvulsant drugs is presented. The serum is extracted with toluene and the dried extract is dissolved in chloroform and applied on to a thin-layer chromatographic plate. After development, the plate is scanned at 215 nm without staining. The drug peaks are well defined. Most of the interfering substances that occur naturally in serum are soluble in and eliminated by the liquid front.     

Confirmatory analysis for drugs of abuse in plasma and urine by high-performance liquid chromatography-tandem mass spectrometry with respect to criteria for compound identification

Recently, high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) has become a powerful tool for quantitative confirmatory analysis of drugs of abuse and has begun to spread in the field of forensic toxicology. Guidelines for confirmatory analysis by GC/MS and LC/MS/MS have been published recently by several organizations (WADA, IOC, SOFT, GTFCh, EU). However, these guidelines have not yet been included in procedures for drug analysis with LC/MS/MS. The prerequisites for forensic confirmatory analysis by LC/MS/MS with respect to EU guidelines are chromatographic separation, a minimum number of two MS/MS transitions to obtain the required identification points and predefined thresholds for the variability of the relative intensities of the MS/MS transitions (MRM transitions) in samples and reference standards. LC/MS/MS methods for determination of several classes of drugs of abuse including some basic drugs (opiates, stimulants), cannabinoids and some of their phase-I- and phase-II-metabolites (especially glucuronides) in urine and serum of drug abusers and/or crime offenders or victims have been developed and validated following current recommendations and are presented in this paper. At least two MRM transitions for each substance were monitored to provide sufficient identification of drugs, deuterated analogues of analytes were used as internal standards for quantitation where possible and chromatographic separation has been performed on reversed-phase columns with gradient elution. Validation data obtained and the application to real samples show that the requested criteria for confirmatory analysis of drugs of abuse by EU guidelines can be fulfilled with a total number of four identification points by LC/MS/MS methods using a triple-quadrupole mass spectrometer. Furthermore, the methods are sufficiently sensitive to meet current requirements for confirmatory analysis of drugs of abuse in driving under the influence of drugs (DUID) cases established by the Society of Toxicological and Forensic Chemistry (GTFCh).     

Nonisotopic receptor-binding assay for benzodiazepine receptors utilizing a fluorophore labeled ligand.

A nonisotopic receptor-binding assay method provides a new approach for the study of receptor-ligand interactions and a possible receptor assay for benzodiazepine drugs. The proposed method is based upon the use of fluorescence-labeled drugs and a chromatographic system which accepts samples without deproteinization. The effectiveness of the technique is illustrated in a study of benzodiazepine receptor-drug-binding interactions.     

Stereoselective determination and pharmacokinetics of dihydropyridines: an updated review

All dihydropyridines, except nifedipine, have at least one chiral center, and their pharmacokinetics and clinical effects differ from one enantiomer to another. Chiral separation methods for dihydropyridines using chromatographic techniques are discussed. The stereoselective pharmacokinetics of dihydropyridine calcium antagonists were reviewed in detail in 1995. The present review article updates the methods for the stereoselective determination of dihydropyridines using chromatographic techniques and summarizes the pharmacokinetics of the dihydropyridines, including the newest drugs under development.     

Principles and applications of luminescence spectrometry coupled to liquid chromatographic techniques

An overview is presented of the physicochemical basis of luminescence, and its application to the detection of chemicals (drugs, biomedically important compounds, environmentally active substances) in liquid chromatographic systems.