Analytical methods for determination of new fluoroquinolones in biological matrices and pharmaceutical formulations by liquid chromatography: a review

Fluoroquinolones are one of the most promising and intensively studied drugs of contemporary anti-infective chemotherapy. New fluoroquinolone antibacterials with improved pharmacokinetic properties and a broad spectrum of activity have been developed, opening new windows of opportunity for clinical use. To our knowledge, no comprehensive and critical review of the analytical methods for the determination of these agents, which correspond to the third- and fourth-generation quinolones, has yet been published. This work summarizes for the first time most of the liquid chromatographic methods reported in the literature for the separation and quantification of the new fluoroquinolones in biological matrices and pharmaceutical formulations. A systematic and detailed survey of physicochemical properties, sample preparation procedures, and chromatographic and detection conditions is presented herein. In the course of this review several liquid chromatographic methods are discussed: reversed-phase high-performance liquid chromatography (RP-HPLC), ion-exchange high-performance liquid chromatography (IEX-HPLC), hydrophilic interaction liquid chromatography (HILIC), high-performance thin-layer chromatography (HPTLC) and other chiral chromatographic methods. Their advantages, applicability and limitations are also examined.     

Chromatographic methods for the determination of toxicants in faeces.

Modern chromatographic techniques and their application in the determination of toxic compounds in faeces are reviewed. Faecal analysis may be of importance in toxicokinetic studies of xenobiotics in order to determine factors such as metabolism, body burden and major routes of elimination. Compounds of interest include various food constituents, drugs and occupational or environmental factors. Further, various mutagenic or carcinogenic compounds which are excreted by faeces have been indicated to represent risk factors for colorectal cancer. In this context, the chromatographic determination of the endogenously generated fecapentaenes and bile acids, both postulated etiological factors in colorectal carcinogenesis, is reviewed. For fecapentaene determination, several high-performance liquid chromatographic (HPLC) methods are available; however, the applicability of some of these methods is limited owing to insufficient separation of various isomeric forms or discrimination between fecapentaenes and their precursors. For the determination of bile acids in faeces, many chromatographic procedures have been reported, and the characteristics of the most relevant methods are compared and discussed. It is concluded that separation by gas chromatography (GC) in combination with mass spectrometry provides the highest selectivity and sensitivity. A relatively rapid alternative analysis for the determination of total and aqueous faecal bile acids is proposed. Further, methods for the determination of polycyclic aromatic hydrocarbons (PAHs) are reviewed. Although the use of radiolabelled PAHs in animal studies has many advantages, it cannot be applied for human biological monitoring and HPLC and GC provide sensitive alternatives. An HPLC method for the determination of non-metabolized PAHs in faeces is described.     

Pharmaceutical applications of micelles in chromatography and electrophoresis

This review surveys the use of micelles as separation media in chromatography and electrophoresis. Applications to pharmaceuticals whose molecular masses are relatively small are focused on in this review. In high-performance liquid chromatography (HPLC), chromatography using micelles and reversed-phase stationary phases such as octadecylsilylized silica gel (ODS) columns is known as micellar liquid chromatography (MLC). The main application of MLC to pharmaceutical analysis is the same as in ion-pair chromatography using alkylsulfonate or tetraalkylammonium. In most cases, selectivity is much improved compared with other short alkyl chain ion-pairing agents such as pentanesulfonate or octanesulfonate. Direct plasma/serum injection can be successful in MLC. Separation of small ions is also successful by using gel filtration columns and micellar solutions. In electrophoresis, especially capillary electrophoresis (CE), micelles are used as pseudo-stationary phases in capillary zone electrophoresis (CZE). This mode is called micellar electrokinetic chromatography (MEKC). Most of the drug analysis can be performed by using the MEKC mode because of its wide applicability. Enantiomer separation, separation of amino acids and closely related peptides, separation of very complex mixtures, determination of drugs in biological samples etc. as well as separation of electrically neutral drugs can be successfully achieved by MEKC. Microemulsion electrokinetic chromatography (MEEKC), in which surfactants are also used in forming the microemulsion, is successful for the separation of electrically neutral drugs as in MEKC. This review mainly describes the typical applications of MLC and MEKC for the analysis of pharmaceuticals.     

Chemometric methods for evaluation of chromatographic separation quality from two-way data--a review

Most traditional chromatographic separation criteria or response functions are defined on chromatograms recorded by single-channel detectors, e.g. a spectrometer measuring the absorbance at a single wavelength or a thermal conductivity detector. When the peaks are seriously overlapped, usually there is a lack of the information concerning the total number of chemical components, overlap degree of the peaks and peak purity. Such information characterizes some crucial aspects of separation process and lack of it will lead to an inaccurate and misleading evaluation of separation quality as well as some computational ambiguity for many traditional response functions. In contrast, hyphenated chromatography-(multi-channel) spectroscopy instruments together with chemometric methods will largely increase the information content available in chromatographic detection. Such information, if properly used, can cast a new light on evaluation of chromatographic separation quality. The main objective of this article is to review chemometric methods devoted to estimation of the number of chemical components, determination of elution sequence and assessment of peak purity. Some newly defined response functions or separation criteria based on extracted information by chemometric methods are also introduced. The methods reviewed are limited to those for treating two-way data obtained by hyphenation of high-performance liquid chromatography with multi-channel detectors. We prefer to provide a comprehensive view of such methods rather than present a full list of all the methods developed. Further details of some important methods are touched upon in favor of employment and understanding of them by researchers not very familiar with chemometrics.     

Ecofriendly chromatographic estimation of spasmolytic pharmaceutical mixture along with official toxic impurity, 3,5-dichloroaniline: Complete green profile appraisal

Nowadays, Green Analytical Chemistry is widely applied to provide various analytical methods with eco-friendly procedures employing the least toxic, harmful reagents on humans and the environment without affecting the efficacy of the determination. Accordingly, two eco-friendly, accurate, and reliable high-performance thin-layer chromatography-densitometry and high-performance liquid chromatographic methods were established for the determination and separation of two antispasmodic drugs, namely phloroglucinol and trimethylphloroglucinol in their pure, combined dosage form along with phloroglucinol toxic impurity, 3,5-dichloroaniline. For high-performance thin-layer chromatography-densitometry, efficient separation was developed via utilizing the stationary phase of high-performance thin-layer chromatography silica gel 60 F₂₅₄ plates and developing a system comprising of ethyl acetate-butanol-ammonia in the ratio of 8.0:2.0:0.2, by volume and scanning of the developed bands at 210.0 nm. The subsequent method is isocratic high-performance liquid chromatography with diode array detection in which separation was successively attained using XTerra RP-C₁₈ (250 × 4.6 mm, 5 μm) column as stationary phase and methanol-10.0 mM phosphate buffer, pH 3.7 ± 0.1 as mobile phase in the ratio of 75.0:25.0, v/v at flow rate 1.0 ml/min and scanning at 220.0 nm. The developed liquid chromatography methods were validated according to the International Council for Harmonization guidelines, and all results acknowledged their efficacy. Additionally, the proposed methods worked well for assessing the cited drugs in binary combined commercially available pharmaceutical formulation. The greenness profile of the present methods was assessed and estimated using various assessment tools, namely; Green Analytical Procedure Index, analytical eco-scale method, National Environmental Method Index in addition to Analytical GREEnness tool to evaluate the greenness of the provided methods with a statistical comparison between them to assess the more green ones.     

Aflatoxin analysis at the beginning of the twenty-first century

Aflatoxin mycotoxins were first described in the early 1960s as important fungal toxins, which contaminate many different human foods and animal feeds. Accurate and sensitive determination of these carcinogenic compounds immediately became an important requirement to meet food safety concerns and new official legislated regulations. For these reasons, analytical methods for aflatoxins continued to develop over the decades, reflecting advances in analytical chemistry. Currently, a wide range of methods are available to analytical scientists, ranging from newly described multi-toxin liquid chromatography tandem mass spectrometry to rapid methods based on immunological principles. These latter methods can provide quantitative outputs or a simple rapid determination of contamination level above or below a pre-determined cutoff value. The newest official methods as validated by Association of Official Analytical Chemists International or Comité Européen de Normalisation rely on immunoaffinity column clean-up of conventional extracts, followed by high-performance liquid chromatography separation of the analogues with detection based on natural fluorescence or the fluorescence generated by various derivatisation methods. In selecting from this range of available methods, the analytical chemist must decide on the requirements of the analysis such that the method chosen is ‘fit for purpose’.     

A review of chromatographic methods for the assessment of phospholipids in biological samples

Phospholipids are important constituents of all living cell membranes. Lipidomics is a rapidly growing field that provides insight as to how specific phospholipids play roles in normal physiological and disease states. There are many analytical methods available for the qualitative and quantitative determination of phospholipids. This review provides a summary of the methods that were historically used such as thin layer chromatography, gas chromatography and high-performance liquid chromatography. In addition, an introduction to applications of interfacing these traditional chromatographic techniques with mass spectrometry is provided.     

Chromatographic methods for tetracycline analysis in foods.

The tetracyclines have served for decades as an important class of antibiotics in food animal health and production. As such, they have also been a source of concern for residue monitoring authorities around the world. In response to this concern a number of microbial inhibition, immunoassay and bacterial receptor methods have evolved for the detection of this class of compounds in various foods of animal origin. However, these methods often lack specificity and are subject to false positive and false negative results. For these reasons a number of chromatographic methods for the separation and determination of the tetracyclines isolated from foods have been developed that are capable of identifying and quantifying individual tetracycline drugs. We present here an overview of tetracycline analytical methods, including microbial inhibition, immunoassay and receptor technologies for detection, techniques for isolation from food matrices, and thin-layer chromatographic, high-performance liquid chromatographic, gas chromatographic and mass spectrometric procedures for determination of this class of compounds. A discussion of the variables involved in such methodology and a review of method criteria are offered.     

Flow methods in chiral analysis

The methods used for the separation and analytical determination of individual isomers are based on interactions with substances exhibiting optical activity. The currently used methods for the analysis of optically active compounds are primarily high-performance separation methods, such as gas and liquid chromatography using chiral stationary phases or chiral selectors in the mobile phase, and highly efficient electromigration techniques, such as capillary electrophoresis using chiral selectors. Chemical sensors and biosensors may also be designed for the analysis of optically active compounds.     

Determination of 1,4-benzodiazepines and their metabolites by capillary electrophoresis and high-performance liquid chromatography using ultraviolet and electrospray ionisation mass spectrometry.

A study is presented for the separation and determination of fifteen 1,4-benzodiazepine drugs and metabolites by capillary electrophoresis (CE) compared with high-performance liquid chromatography (HPLC). A comparison is made between the CE determination of the compounds by conventional UV detection and LC determination with electrospray ionisation (ESI) ion-trap mass spectrometry. CE is shown to provide superior separation to HPLC but the MS-MS capability of the ion-trap allows for the specific detection and determination of four of the compounds, diazepam, N'-desmethyldiazepam, oxazepam and temazepam in the hair of a patient under clinical treatment with diazepam and temazepam. Selected mixtures of drugs and metabolites are determined by CE and LC and the determination of diazepam and its metabolites by CE-UV-ESI-MS-MS is also presented.