LC-MS/MS method for simultaneous estimation of raloxifene, cladrin in rat plasma: application in pharmacokinetic studies

Aim: A newer LC-MS/MS method was developed and validated for the simultaneous quantification of raloxifene (RL) and cladrin (CL). Methodology: Both drugs were resolved in RP-18 (4.6 × 50 mm, 5 μ) Xbridge Shield column using acetonitrile and 0.1% aqueous solution of formic acid (FA) (70:30% v/v) as mobile phase by using biological matrices in female Sprague-Dawley rats using-MS/MS. Results: The developed method was found to be linear over the concentration ranges of 1-600 ng/ml, and lower limit of quantification was 1 ng/ml for RL and CL, respectively. Pharmacokinetic results of RL+CL showed Cmax = 4.23 ± 0.61, 26.97 ± 1.14 ng/ml, at Tmax(h) 5.5 ± 1.00 and 3.5 ± 1.00, respectively. Conclusion: Pharmacokinetic study results will be useful in the future for the combined delivery of RL and CL for osteoporosis treatment.

Enhanced chromatographic efficiency obtained with vacuum jacketed columns facilitates the rapid UHPLC/MS/MS-based analysis of fasiglifam in rat plasma

The use of vacuum jacketed LC columns (VJC) to minimize on- and post-column band broadening to maximize chromatographic performance has been evaluated as a potential route to improved high throughput (HT) analysis. Here the use of the "VJC" approach has been applied to the HT bioanalysis of the antidiabetic GPR40 agonist drug fasiglifam in rat plasma samples obtained following a 5 mg/kg IV dose. The data obtained from a 1 minute VJC/MS-based analysis showed significant improvements compared to that from a conventional 2 minute UHPLC method for the drug. Notably, using VJC/MS with the rapid 1 min analysis provided a ca. 50% reduction in peak width coupled with a 2-5 fold higher peak response whilst doubling analytical throughput when compared to a conventional UHPLC/MS method. In addition, the increased resolution provided by the VJC system also improved the separation of fasiglifam from common matrix interferences such as co-extracted phospholipids thereby reducing the potential for matrix effects. The concatenation of these improvements suggests that the VJC approach may indeed provide a pathway to more sensitive, robust and high throughput drug bioanalysis, with particular advantages for drug discovery applications.

High Throughput UHPLC-MS-Based Lipidomics Using Vacuum Jacketed Columns

Reversed-phase UHPLC-MS is extensively employed for both the profiling of biological fluids and tissues to characterize lipid dysregulation in disease and toxicological studies. With conventional LC-MS systems the chromatographic performance and throughput are limited due to dispersion from the fluidic connections as well as radial and longitudinal thermal gradients in the LC column. In this study vacuum jacketed columns (VJC), positioned at the source of the mass spectrometer, were applied to the lipidomic analysis of plasma extracts. Compared to conventional UHPLC, the VJC-based methods offered greater resolution, faster analysis, and improved peak intensity. For a 5 min VJC analysis, the peak capacity increased by 66%, peak tailing reduced by up to 34%, and the number of lipids detected increased by 30% compared to conventional UHPLC. The narrower peaks, and thus increased resolution, compared to the conventional system resulted in a 2-fold increase in peak intensity as well a significant improvement in MS and MS/MS spectral quality resulting in a 22% increase in the number of lipids identified. When applied to mouse plasma samples, reproducibility of the lipid intensities in the pooled QC ranged from 1.8-12%, with no related drift in t_R observed.

High-Throughput UHPLC/MS/MS-Based Metabolic Profiling Using a Vacuum Jacketed Column

In UHPLC, frictional heating from the eluent flowing through the column at pressures of ca. 10-15 Kpsi causes radial diffusion via temperature differences between the center of the column and its walls. Longitudinal dispersion also occurs due to temperature gradients between the inlet and outlet. These effects cause band broadening but can be mitigated via a combination of vacuum jacketed stainless steel tubing, reduced column end nut mass, and a constant temperature in the column from heating the inlet fitting. Here, vacuum jacketed column (VJC) technology, employing a novel column housing located on the source of the mass spectrometer and minimized tubing from the column outlet to the electrospray probe, was applied to profiling metabolites in urine. For a 75 s reversed-phase gradient separation, the average peak widths for endogenous compounds in urine were 1.2 and 0.6 s for conventional LC/MS and VJC systems, respectively. The peak tailing factor was reduced from 1.25 to 1.13 when using the VJC system compared to conventional UHPLC, and the peak capacity increased from 65 to 120, with a 25% increase in features detected in urine. The increased resolving power of the VJC system reduced co-elution, simplifying MS and MS/MS spectra, providing a more confident metabolite identification. The increased LC performance also gave more intense MS peaks, with a 10-120% increase in response, improving the quality of the MS data and detection limits. Reducing the LC gradient duration to 37 s gave peak widths of ca. 0.4 s and a peak capacity of 84.

Improving LC/MS/MS-based bioanalytical method performance and sensitivity via a hybrid surface barrier to mitigate analyte - Metal surface interactions

The accurate determination of the pharmacokinetics (PK) of a candidate drug molecule is critical in both drug discovery and development. Over the last 30 years, the sensitivity and selectivity of LC/MS has resulted in it being established as the technology of choice for these studies. However, unwanted chemical interactions between analyte(s) and the metal components in a chromatography system can result in poor peak shape and reduction in signal response, which can adversely affect the analysis of low concentrations of drugs and their metabolites in biological samples. This study evaluated the benefits of employing an inert hybrid surface technology (HST) applied to the metallic components in the LC flow path, column frits and column wall to mitigate these interactions. The results obtained were compared with that of an identical conventional LC for the bioanalysis of two steroid phosphate drugs (dexamethasone phosphate and hydrocortisone phosphate) and an epidermal growth factor receptor (EGFR) inhibitor (gefitinib) in human plasma. The results showed that for the two steroid phosphates, the peak width was reduced by 20%, peak tailing factors reduced by up to 30% and the assay sensitivity improved by factors of 7.5 and 10. This resulted in a significant improvement in the limit of detection. The new LC system also improved the reproducibility of peak integration for gefitinib, thereby reducing assay coefficients of variation (%CV) from greater than 10% to less than 5% at the lower limit of quantification.

[Recent advances in microchip liquid chromatography]

Miniaturization is an important trend in modern analytical instrument development, including miniaturized gas chromatography and liquid chromatography, as well as micro bore columns and capillary-to-microfluidics-based platforms. Apart from the miniaturization of the separation column, which is the core part of a chromatographic system, other parts of the system, including the sampler, pumping system, gradient generation, and detection systems, have been miniaturized. Miniaturized liquid chromatography significantly reduces solvent and sample consumption while providing comparable or even better separation efficiency. When liquid chromatography is coupled with mass spectroscopy, a low flow rate can increase the ionization efficiency, leading to enhanced sensitivity of the mass spectrometer. In contrast, normal-scale liquid chromatography suffers from its relatively high volumetric flow rate, which challenges the scanning frequency of the mass spectrometer. On the other hand because of the small sample size, other detection strategies such as spectrometric methods cannot provide sufficient sensitivity and limits of detection. In this sense, mass spectrometry has become the detection method of choice for micro-scale liquid-phase chromatography. Miniaturized liquid chromatography can diminish sample dilution efficiently when extremely small amounts of samples are used. The main driving force for this miniaturization trend, especially in liquid-phase separations, is the desperate need for microscale analyses of biological and clinical samples, given these samples are precious and the sample size is usually very small. At present, microscale liquid-phase chromatography is the only method of choice for such small, precious, and highly informative samples. The miniaturization of liquid chromatography systems, especially chromatographic columns, would be advantageous to the modularization and integration of liquid chromatography instrumental systems. Chip liquid chromatography is an integration of chromatography columns, liquid control systems, and detection methods on a single microfluidic chip. Chip liquid chromatography is an excellent format for the miniaturization of liquid chromatography systems, and it has already attracted significant attention from academia and industry. However, this attempt is challenging, and great effort is required on fundamental techniques, such as the substrate material of the microfluidic chip, structure of the micro-chromatography column, fluid control method, and detection methods, in order to make the chips suitable for liquid chromatography. Currently, the major problem in chip liquid chromatography is that the properties of the chip substrate materials cannot meet the requirements for further miniaturization and integration of chip liquid chromatography. The strength of the existing chip substrate materials is generally below 60 MPa, and the material properties limit further advances in the miniaturization and integration of chromatographic chips. Therefore, new chip substrate materials and the standard of chip channel design such as channel size and channel structure should be the key for further development of chip liquid chromatography. Mainstream instrumentation companies as well as new start-up innovation companies are now undertaking efforts toward the development of microchip liquid chromatographic products. Agilent, the first instrumentation company that introduced commercial microchip liquid chromatographic columns to the market, has led this field. Apart from microchip-based columns, Agilent introduced trap columns for different kinds of biological molecules as well as gradient generation systems for microchip-based liquid phase chromatography. Recently, another start-up company introduced microchip columns based on the in situ microfabrication of the column bed rather than packing the column with a particulate material. Such developments in microfabrication may further propel the advancement of micro-scale liquid-phase chromatography to an unprecedented level, which is beyond the conventional components and materials employed in normal-scale liquid chromatography. This review introduces the recent research progress in microchip liquid chromatography technologies, and briefly discusses the current state of commercialization of microchips for liquid chromatography by major instrumentation companies.

Current developments in LC-MS for pharmaceutical analysis

Liquid chromatography (LC) based techniques in combination with mass spectrometry (MS) detection have had a large impact on the development of new pharmaceuticals in the past decades.

A microfluidic chip-based co-culture of fibroblast-like synoviocytes with osteoblasts and osteoclasts to test bone erosion and drug evaluation

Targeting fibroblast-like synoviocyte (FLS) migration and invasion-mediated bone erosion is a promising clinical strategy for the treatment of rheumatoid arthritis (RA). Drug sensitivity testing is fundamental to this scheme. We designed a microfluidic chip-based, cell co-cultured platform to mimic RA FLS-mediated bone erosion and perform drug-sensitive assay. Human synovium SW982 cells were cultured in the central channel and migrated to flow through matrigel-coated side channels towards cell culture chamber where RANKL-stimulated osteoclastic RAW264.7 and osteogenic medium (OS)-stimulated bone marrow mesenchymal stem cells (BMSC) were cultured in the microfluidic chip device, mimicking FLS migration and invasion-mediated bone erosion in RA. These SW982 cells showed different migration potentials to osteoclasts and BMSC. The migration of SW982 cells with high expression of cadherin-11 was more potent when SW982 cells were connected with the co-culture of RAW264.7 and BMSC. Simultaneously, in the co-cultured chamber, tartrate-resistant acid phosphatase (TRAP) activity of RANKL-stimulated RAW264.7 cells was enhanced, but alkaline phosphatase (ALP) activity was decreased in comparison with mono-cultured chamber. Furthermore, it was confirmed that celastrol, a positive drug for the treatment of RA, inhibited SW982 cell migration as well as TRAP activity in the cell-cultured microfluidic chips. Thus, the migration and invasion to bone-related cells was reconstituted on the microfluidic model. It may provide an effective anti-RA drug screen model for targeting FLS migration-mediated bone erosion.

Capillary ultra performance liquid chromatography-tandem mass spectrometry analysis of tienilic acid metabolites in urine following intravenous administration to the rat

Capillary scale (100 mm × 150 μm id) UPLC/MS/MS, performed using reversed-phase gradient chromatography on sub 2 μm particles, has been successfully employed for the characterization of the metabolites of the drug tienilic acid (TA) excreted via the urine following oral administration to the rat. The capillary LC system provided a significant increase (range ca. 11-33-fold) in sensitivity compared with a conventional 150 mm × 2.1 mm id UPLC system. An investigation of the effect of the injection volume and sample mass loading on the capillary column on the results obtained for both endogenous metabolites and TA was performed. This demonstrated that the injection of up to 2 μL of rat urine onto the system was permitted whilst still providing excellent chromatographic results and robustness. Qualitative analysis of the urine revealed the presence of TA itself and a total of 15 metabolites of the drug, including those resulting from biotransformations such as hydroxylation or conjugation. The capillary chromatography system was shown to be robust, and capable of providing comprehensive drug metabolite profiles from small format urine samples such as those obtained from preclinical studies in rodents.

Quantitative mass spectrometry methods for pharmaceutical analysis

Quantitative pharmaceutical analysis is nowadays frequently executed using mass spectrometry. Electrospray ionization coupled to a (hybrid) triple quadrupole mass spectrometer is generally used in combination with solid-phase extraction and liquid chromatography. Furthermore, isotopically labelled standards are often used to correct for ion suppression. The challenges in producing sensitive but reliable quantitative data depend on the instrumentation, sample preparation and hyphenated techniques. In this contribution, different approaches to enhance the ionization efficiencies using modified source geometries and improved ion guidance are provided. Furthermore, possibilities to minimize, assess and correct for matrix interferences caused by co-eluting substances are described. With the focus on pharmaceuticals in the environment and bioanalysis, different separation techniques, trends in liquid chromatography and sample preparation methods to minimize matrix effects and increase sensitivity are discussed. Although highly sensitive methods are generally aimed for to provide automated multi-residue analysis, (less sensitive) miniaturized set-ups have a great potential due to their ability for in-field usage.This article is part of the themed issue 'Quantitative mass spectrometry'.