Screening and monitoring antiretrovirals and antivirals in the serum of acquired immunodeficiency syndrome patients by micellar liquid chromatography

Chromatographic methods in HIV medicine: Application to therapeutic drug monitoring

HIV antiretroviral therapy spans several different drug classes, meant to combat various aspects of viral infection and replication. Many authors have argued the benefits of therapeutic drug monitoring (TDM) for the HIV patient including compliance assurance and assessment of appropriate drug concentrations; however, the array of drug chemistries and combinations makes TDM an arduous task. HPLC-UV and LC-MS/MS are both frequent instruments for the quantification of HIV drugs in biological matrices with investigators striving to balance sensitivity and affordability. Plasma, the dominant matrix for these analyses, is prepared using protein precipitation, liquid-liquid extraction or solid-phase extraction depending on the specific complement of analytes. Despite the range of polarities found in drug classes relevant to HIV therapeutics, most chromatographic separations utilize a hydrophobic column (C₁₈ ). Additionally, as the clinically relevant samples for these assays are infected with HIV, along with possible co-infections, another important aspect of sample preparation concerns viral inactivation. Although not routine in clinical practice, many published analytical methods from the previous two decades have demonstrated the ability to conduct TDM in HIV patients receiving various medicinal combinations. This review summarizes the analytical methods relevant to TDM of HIV drugs, while highlighting respective challenges.

Online solid phase extraction and liquid chromatography-mass spectrometric determination of nucleoside drugs in plasma

The bioanalysis and especially the sample preparation of nucleoside drugs in complex media, such as human plasma, has been challenging due to the high polarity and high solubility of these drugs in water. Online solid phase extraction (SPE) offers significant advantages, such as automation and timesaving. Thus, several types of SPE columns have been developed for compounds with different polarities. In this study, SPE was applied to overcome the issue of sample pretreatment of nucleoside drugs in human plasma, with the final aim of establishing a robust analytical platform for drugs with similar structures. A simple, easy-to-use, and efficient method is described for the simultaneous determination of lamivudine, zidovudine, didanosine and emtricitabine in human plasma via online SPE and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Following a simple centrifugation step, a 10μL plasma sample was injected directly onto the HPLC system. The Oasis MCX cartridge was washed, and the analytes were removed by back-flushing directly onto the analytical column. The analytes were quantified using a triple-quadrupole tandem mass spectrometer in multiple-reaction monitoring mode. Similarly, with the development and application of a Bond Elut phenylboronic acid (PBA) SPE cartridge, a fully automated online SPE-HPLC-MS/MS method was established for the simultaneous determination of ribavirin and taribavirin in human plasma. Linear calibration curves were obtained over the range of 0.5-2000ngmL^-1, and the limit of quantification ranged from 0.5ngmL^-1 to 10ngmL^-1, which is sensitive enough for clinical drug monitoring. The intra- and inter-day precisions were in the range of 0.2-8.9%, and the trueness ranged between 88.9% and 113.1%. Excellent recoveries from plasma were achieved with a range between 86.7% and 105.1%. This procedure is easier to perform and requires less sample handling compared to methods previously described in the literature. This high-throughput method involving the direct injection of plasma samples may provide a practical solution for the analysis of multiple nucleoside drugs in clinical research. The method was tested in plasma samples from some patients and showed good performance.

Application of micellar liquid chromatography for the determination of antitumoral and antiretroviral drugs in plasma

In micellar liquid chromatography, the mobile phase is made of a surfactant and, eventually, an alcohol. This article describes several methods to measure the concentration of antitumoral and antiretroviral drugs in plasma, utilizing micellar liquid chromatography. Samples can be injected after dilution with a micellar solution and filtration, because proteins and other endogenous compounds are solubilized in micellar medium. We will discuss the following optimized parameters: dilution ratio, type of column, detection conditions and mobile phase composition. This article will also cover the validation performed following the International Conference on Harmonization guidelines and the results reported in the literature, indicating that the methods are useful for the routine analysis of plasma samples for clinical purposes.

Biological sample preparation: attempts on productivity increasing in bioanalysis

Sample preparation is an important step of any biomedical analysis. Development and validation of fast, reproducible and reliable sample preparation methods would be very helpful in increasing productivity. Except for a few direct injection methods, almost all biological samples should at least be diluted before any analysis. Sometimes dilution is not possible because of the low concentration of the target analyte in the sample, and alternative pretreatments, such as filtration, precipitation and sample clean up using different extraction methods, are needed. This review focuses on the recent achievements in the pretreatment of biological samples and investigates them in six categories (i.e., dilution, filtration/dialysis, precipitation, extraction [solid-phase extraction, liquid–liquid extraction], novel techniques [turbulent flow chromatography, immunoaffinity method, electromembrane extraction] and combined methods). Each category will be discussed according to its productivity rate and suitability for routine analysis, and the discussed methods will be compared according to the mentioned indices.

Recent theoretical and practical applications of micellar liquid chromatography (MLC) in pharmaceutical and biomedical analysis

Micellar liquid chromatography (MLC) is an analytical technique belonging to the wide range of reversed-phase liquid chromatographic (RP-LC) separation techniques. MLC with the use of surfactant solutions above its critical micellar concentration (CMC) and the addition of organic modifiers is currently an important analytical tool with still growing theoretical considerations and practical applications in pharmaceutical analysis of drugs and other biologically active compounds. The use of MLC as an alternative, relatively much faster in comparison to conventional chromatographic separation techniques has several advantages, especially as being suitable for screening pharmaceutical analysis. The analytical data received from MLC analysis are considered a useful source of information to predict passive drug absorption, drug transport and other pharmacokinetics and physicochemical measures of pharmaceutical substances. In the review several MLC assays for determination of drugs and other active compounds in biological samples were compared and critically discussed. The presented overview provides information on recent applications and achievements connected with the practical use of MLC. The review covers fields of interest related to theory and mechanism of MLC separation, direct applications of MLC in pharmaceutical analysis, including optimization and efficiency of separation with the use of modification of stationary phase and mobile phase compositions as well as the determination of physicochemical characteristics of drugs by MLC.