ABSTRACT
A high-throughput liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, which combines on-line sample extraction through turbulent flow chromatography with a monolithic column separation, has been developed for direct injection analysis of drugs and metabolites in human plasma samples. By coupling a monolithic column into the system as the analytical column, the method enables running 'dual-column' extraction and chromatography at higher flow rates, thus significantly reducing the time required for the transfer and mixing of extracted fraction onto the separation column as well as the time for gradient separation. A strategy of assessing and reducing the matrix suppression effect on the on-line extraction LC/MS/MS has also been discussed. Experiments for evaluating the resolution, peak shape, sensitivity, speed, and matrix effect were conducted with dextromethorphan and its metabolite dextrorphan as model compounds in human plasma matrix. It was demonstrated that the total run time for this assay with a baseline separation of two analytes is less than 1.5 min.
Subject(s)
Analgesics, Opioid/blood , Chromatography, High Pressure Liquid , Dextromethorphan/blood , Dextrorphan/blood , Excitatory Amino Acid Antagonists/blood , Spectrometry, Mass, Electrospray Ionization/methods , Humans , Sensitivity and Specificity , Spectrometry, Mass, Electrospray Ionization/instrumentationABSTRACT
As preparation for an extensive study that aims to image the cryocooling process of macromolecular crystals, the ability to thermally image solid objects and liquids at temperatures far below 273 K is demonstrated. In the case of a large lysozyme crystal (1.0 x 0.7 x 0.2 mm), qualitative measurements show the cooling process to take about 0.6 s with the cooling taking place in a wave starting from the face of the crystal nearest to the origin of the cryostream and ending at the point furthest away from the origin. Annealing of this lysozyme crystal, cooled under good cryoprotectant conditions, shows that cold striations form perpendicular to the cooling stream. These striations become more pronounced after successive annealing. Cryocooling of a non-cryoprotected crystal of glucose isomerase displayed an 'S-shaped' cold front wave traveling across the sample. These preliminary results are qualitative but show the power of infrared imaging as a new tool for fundamental and practical cryocrystallography studies.
