Automated purity assessment

An example of automated purity assessment of a compound analyzed by LC/UV/MS is shown in Figure 11-4. In this example, purity is assessed at two different wavelengths, X220 and L254. Excel macros are used for automated... 

Figure 11-4. Purity assessment is a critical component in the decision process by the chemist as to whether their isolated compound is of sufficient quality to be submitted for compound registration and biological testing. To facilitate automated and rapid purity assessment of compound libraries, applescripts and visual basic scripts are used. (A) Total ion current chromatogram shows two components. (B) Extracted ion chromatogram for the expected product identifies its retention time. (C) Mass spectrum observed for the expected product. (D) UV 220-nm chromatogram indicates the expected product is approximately 75% pure. (E) UV 254-nm chromatogram indicates the expected product is approximately 66% pure.

Fast LC-MS methods have been used to assess library quantity and purity, as well as to triage purification of compounds. Zeng et al. [51] developed one of the first fully automated analytical/preparative LC-MS systems for the characterization and purification of compound libraries derived by parallel synthesis. The system incorporated fast, reverse-phase LC/ESI-MS analysis (5-10 minutes). Post-data-acquisition purity assessment of compound ti-braries was performed automatically with software control. Compounds that were below a threshold level of purity were automatically purified with HPLC. The real-time purity assessment eliminated the need for postpurification analysis or pooling of fractions collected. 

Thus, in the result of automated data processing one can confirm the identity of library components, perform purity assessment based on several independent techniques (UV, MS, ELSD), estimate quantities of compounds, obtain information about side products, etc. The results may be presented using tabular output, which has certain strengths and weaknesses. On one side, a lot of different information about compounds can be captured in one table, such as sample ID, purity, estimated amount of material, etc. the data can be easily sorted and transferred to various databases. An example of tabular output where compounds were sorted based on their average purity is presented in [34], On the other side, the amount of information usually captured in a table is much more than is nec-... 

Capillary electrophoresis (CE) is a modern analytical method that is being extensively applied to the characterization of biotechnology-derived products like peptides and proteins [1], Due to its ease of automation and facilitating the development of reproducible routine analysis, CE seems to be well suited for the quality control of biotechnological products, including process monitoring, purity assessments. 

UV, or evaporative light-scattering detection (ELSD). In a related approach, Schmid et al. described an automated robotics system based on SPE [45]. This system uses 1-3 fractionation steps, followed by a concentrahon step to generate semipurihed samples. MALDI-TOE was used to assess the purity and identity of the resulhng fractions. The complexity of the hnal frachons was dramatically reduced, resulting in better compatibility with their biological screens. These developments in automated fractionation have been used to generate a purihed central natural product pool, as described by Koch et al. [46]. 

The large numbers of compounds synthesized by HTOS and purified by HTP require high throughput analysis and quality assessment. Mass spectrometry is commonly used for this purpose. Research and development in the analysis of libraries have been focused primarily on the improvement of throughput and automation in the analysis, interpretation, and reporting of data. Morand et al. have recently reviewed development of high throughput mass spectrometry in pharmaceutical research [20] for the analysis of chemical library compounds. Also, the use of one or more auxiliary detection techniques, such as UV or ELSD in addition to mass spectrometry, allows for better assessment of the purity of library compounds. 

The purity of the intermediates was assessed by TLC, MS, and H NMR, and intermediates that were less than 90% pure were not used in subsequent reactions. Unfortunately, only a randomly chosen fraction (-5%) of the final products was analyzed by MS and only a few products were analyzed by HPLC. Thus, there are no rehable data about the identities and purities of the final products. Nevertheless, this work is an impressive example of solution-phase synthesis of a large combinatorial library and an automated liquid-liquid extraction purification strategy-... 

TLRC can be used for animal, human, and plant metabolism analysis radiochemical purity and stability assessment toxicology and biochemical studies and separation, detection, and quantification of separated radioactive zones of all compound classes. Traditional film autoradiography and LSC continue to be widely used, but phosphor imaging and layer scanners are being increasingly applied. The instruments for these methods are highly automated and... 

In this method, the measurement of conductance was used to evaluate the total concentration of the dissolved minerals within the raw and treated water or to determine the degree of demineralization of distandard and deionized water. The work presents an expedient conductometric method for assessing Si02 concentration in high-purity water obtained by ion-exchange demineralization. This method can be used for continuous measurements required by accurate kinetic and thermodynamic studies and monitoring automated systems within industrial facilities. 

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