Micellar electrokinetic chromatography–electrospray ionization mass spectrometry for the identification of drug impurities

Capillary Electrophoresis-Mass Spectrometry for Clinical Metabolomics

In clinical metabolomics, capillary electrophoresis-mass spectrometry (CE-MS) has become a very useful technique for the analysis of highly polar and charged metabolites in complex biologic samples. A comprehensive overview of recent developments in CE-MS for metabolic profiling studies is presented. This review covers theory, CE separation modes, capillary coatings, and practical aspects of CE-MS coupling. Attention is also given to sample pretreatment and data analysis strategies used for metabolomics. The applicability of CE-MS for clinical metabolomics is illustrated using samples ranging from plasma and urine to cells and tissues. CE-MS application to large-scale and quantitative clinical metabolomics is addressed. Conclusions and perspectives on this unique analytic strategy are presented.

Determination of galantamine hydrobromide in bulk drug and pharmaceutical dosage form by spectrofluorimetry

AIM

To develop a simple, accurate, sensitive, rapid and precise method for the determination of galantamine hydrobromide in bulk drug and pharmaceutical dosage form.

MATERIAL AND METHODS

The method employs wavelength detection and determination of galantamine hydrobromide at excitation wavelength 282 nm and emission wavelength 607 nm in a solution of simple distilled water.

RESULT AND CONCLUSION

The method was found to be linear in the range of 2-14 μg/ml having r (2) = 0.9999. The mean accuracy was found to be 98.12% to 99.67%. The intraday and interday precision was found to be 0.18-0.35% and 0.13-0.46%, respectively. The limit of detection was found to be 0.29 μg/ml. The limit of quantification was found to be 0.89 μg/ml. The method was successfully applied for the determination of galantamine hydrobromide in bulk drug as well as pharmaceutical dosage form.

Analysis of plasma nucleotides in rat by micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry

RATIONALE

The aim of this study was to establish a simultaneous quantitative analysis method of nine endogenous nucleotides in rat plasma using micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry (MEKC/ESI-MS).

METHODS

To select the optimum conditions for separation of the nucleotides, various pH, concentrations of running buffers and surfactants were tested. Ammonium acetate (20 mM) containing the surfactant dodecyltrimethylammonium bromide (2 mM, pH 3.5) was selected as the micellar running buffer. The plasma samples were prepared by precipitating the proteins with 2 mM EDTA in 60% ethanol. The samples were analyzed using capillary electrophoresis (CE)/MS and selected ion monitoring (SIM) mode with positive ionization. CE was performed using a silica capillary column in reversed polarity mode.

RESULTS

The limits of detection (LODs) and limits of quantification (LOQs) of the nucleotides ranged from 0.05-5 and 2.0-20 μM, respectively. The calibration curves were linear (R(2) >0.99) for all analytes, and the accuracy and precision were within ±15%. The developed method was applied to the analysis of nucleotides in rat plasma that was collected after oral administration of acetaminophen (1000 mg/kg/day) to evaluate the changes in plasma nucleotide levels under hepatotoxic conditions.

CONCLUSIONS

Decreased level of GTP and increased level of cytosine nucleotides were found to be associated with liver toxicity, which led to the conclusion that liver toxicity is closely related to changes in nucleotide levels in plasma.

Ionization techniques in capillary electrophoresis-mass spectrometry: principles, design, and application

A major step forward in the development and application of capillary electrophoresis (CE) was its coupling to ESI-MS, first reported in 1987. More than two decades later, ESI has remained the principal ionization technique in CE-MS, but a number of other ionization techniques have also been implemented. In this review the state-of-the-art in the employment of soft ionization techniques for CE-MS is presented. First the fundamentals and general challenges of hyphenating conventional CE and microchip electrophoresis with MS are outlined. After elaborating on the characteristics and role of ESI, emphasis is put on alternative ionization techniques including sonic spray ionization (SSI), thermospray ionization (TSI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), matrix-assisted laser desorption ionization (MALDI) and continuous-flow fast atom bombardment (CF-FAB). The principle of each ionization technique is outlined and the experimental set-ups of the CE-MS couplings are described. The strengths and limitations of each ionization technique with respect to CE-MS are discussed and the applicability of the various systems is illustrated by a number of typical examples.

MEKC as a powerful growing analytical technique

This review summarizes the principle and the developments in MEKC in terms of separation power, sensitivity, and detection approaches more than 25 years after its appearance. Newly used surfactants are mentioned. Classical and new sample concentration techniques in MEKC are described. The different detection approaches in MEKC with advantages, limitations, and future prospects are also discussed. This review highlights the wider application of MEKC in different analytical fields. Various recent selected applications of this technique in different analytical fields are reported.

The rapid detection and identification of the impurities of simvastatin using high resolution sub 2 μm particle LC coupled to hybrid quadrupole time of flight MS operating with alternating high–low collision energy

The profiling and identification of impurities in raw pharmaceuticals or finished drug product is an essential part of the pharmaceutical manufacturing process. Critical to this process is the ability to confirm known, expected impurities and identify new impurities. LC coupled to electrospray MS is a powerful tool that has been employed for the identification of impurities, natural products, drug metabolites, and proteins. In this study, we show how sub 2 microm porous particle LC has been coupled to hybrid quadrupole orthogonal TOF mass spectrometer to profile and identify the impurities of the common cholesterol lowering drug simvastatin. The hybrid quadrupole TOF mass spectrometer was operated by alternating the collision cell energies to allow for the rapid, facile conformation of the identity of impurities. Using this process it was possible to identify all of the common impurities of simvastatin in a single 10 min run. During the analysis a new impurity of simvastatin was detected and identified as the saturated ring form of simvastatin.

Nonaqueous electrokinetic chromatography–electrospray ionization mass spectrometry using anionic cyclodextrins

The set-up of an on-line method for coupling nonaqueous electrokinetic chromatography (NAEKC) and electrospray ionization mass spectrometry (ESI-MS) is presented. It allows the use of the single-isomer derivative anionic cyclodextrins heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-cyclodextrin (HDAS-beta-CD) for chiral and achiral separations of positively charged analytes. The effect of the cyclodextrins (CDs) on the MS signal intensities of model compounds was studied. When a voltage is applied over the CE capillary, the overall mobility of the CDs is towards the inlet vial preventing CDs from entering the ion source. However, the sodium counter ions of the CDs still enter the ion source and appeared to cause ionization suppression. Nevertheless, significant analyte signals could still be detected with detection limits in the sub-microg/ml. System parameters such as sheath liquid composition and flow rate, nebulizing gas pressure, capillary position in the sprayer and the drying gas flow and temperature were studied and optimized. The selection of a relatively low nebulizing gas pressure appeared to be important to achieve optimum sensitivity. The chiral selectivity of the NAEKC-ESI-MS system could be improved by addition of camphorsulfonate to the background electrolyte. Using mixtures of drugs and drug-related compounds, the NAEKC-ESI-MS system is shown to offer potential for (chiral) drug profiling.