The amount of sample that can be injected at one time (load with respect to column) to maximize productivity must also be determined. Once the total amount of fraction necessary for evaluation and analysis of the target compounds and subsequent processing is calculated and the detector has been selected, the next step is to determine what scale of fractionation is required. In addition, if the volume of eluate to be introduced into the ELSD or MS detector is ultra small, a make-up pump is used to augment the mobile phase flow and maintain steady detection by the ELSD or MS.ĭetermination of the optimum preparative system To accomplish this, an active APV splitter (Automated Proportioning Valve) is used to split the flow line. To resolve this problem, most of the column eluate is directed to the fraction collector, and the remaining micro volume is introduced into the ELSD or MS. Since ELSD and MS detectors rely in principle on nebulization of the column eluate inside the detector, the target substances emerging from these detectors cannot be recovered. If the target compound or the coexisting impurities in the sample solvent have no optical absorbance, detectors based on principles other than optical absorbance detection such as ELSD (evaporative light scattering detector) and MS (mass spectrometer) can be used as supplementary detectors to improve purification efficiency, thereby improving productivity. Most simple solutions are based on UV detectors (ideally multi-wavelength or photo diode array). To ensure that the intended evaluation and analysis operations can be started as soon as possible following the preparative process to achieve the highest possible productivity, an appropriate system should be able to separate the quantity of compounds and integrate a detection principle that can most effectively ensure collection of the all possible target compounds.įigure 3: Configuration schema of prep LCMS system Just as with a typical pretreatment process, productivity is the key point in a preparative system. It is therefore important that target compounds are obtained quickly and at high purity. The objectives of a typical LC system are to conduct quantitative and qualitative analysis, but a preparative system is used more for so-called “pretreatment” with the objective of actually obtaining the necessary compounds for evaluation and analysis, as well as for subsequent processing. Additional is a mechanism for collecting fractions consisting of the target substances, thereby completing the basic configuration of a preparative system.Įfficient collection of target compounds is key Since a preparative system must separate the target components from the coexisting substances in a sample, the basic system configuration comprises of solvent delivery pumps, sample injector, column and detector, as in a typical LC system. Obtaining these target compounds at high purity enables their structural analysis, permitting evaluation and analysis of their various functions while allowing their subsequent processing to be conducted more reliably. Preparative LC as well as the combination of preparative LC with MS detection is used in several steps in drug development.įigure 1: Preparative LC systems with automatic sample injection and fraction collectionĪ preparative system can be used to recover high purity components from some types of liquid extract obtained either from a synthesis reaction or from a natural substance by separating and purifying the target compounds.
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