HPLC instrumentation selection

FIA has also found wide application in pharmaceutical analysis.214,215 Direct UV detection of active ingredients is the most popular pharmaceutical analysis application of FIA. For single component analysis of samples with little matrix interference such as dissolution and content uniformity of conventional dosage forms, many pharmaceutical chemists simply replace a column with suitable tubing between the injector and the detector to run FIA on standard HPLC instrumentation. When direct UV detection offers inadequate selectivity, simple online reaction schemes with more specific reagents including chemical, photochemical, and enzymatic reactions of derivatization are applied for flow injection determination of pharmaceuticals.216... 

HPTLC is a very fast and convenient assay to separate samples components and is often used in Organic Chemistry and in Synthetic approach. Unknown substances, after different display assay, were generally scraped off from the TLC/HPTLC plate, diluted into a tube and transferred into the MS system for structural elucidation and characterization. Now, a TLC-MS interface was developed by CAMAG, which can semi-automatically extract zones of interest and on-line direct them into any brand of a HPLC-MS system. The TLC-MS interface is connected by two fittings to any HPLC instrument coupled with mass spectrometer, without other system configuration adjustments or mass spectrometer modifications. By this way, the unknown substances can be directly extracted from a TLC/HPTLC plate, eluted and resolved by HPLC system and sensitive and selective mass spectrometric signals are obtained within a minute per substance zone [33],... 

The primary object of this book is to provide the HPLC practitioner with a handy guide to the use of HPLC for analyzing pharmaceutical compounds of interest. This means familiarizing the practitioner with the theory, instrumentation, regulations, and numerous applications of HPLC. This handbook provides practical guidelines using case studies on sample preparation, column or instrument selection, and summaries of best practices in method development and validation, as well as tricks... 

HPLC methods can usually be transferred without many modifications, since most commercially available HPLC instruments behave similarly. This is certainly true when the columns applied have a similar selectivity. One adaptation, sometimes needed, concerns the gradient profiles, because of different instrumental or pump dead-volumes. However, larger differences exist between CE instruments, e.g., in hydrodynamic injection procedures, in minimum capillary lengths, in capillary distances to the detector, in cooling mechanisms, and in the injected sample volumes. This makes CE method transfers more difficult. Since robustness tests are performed to avoid transfer problems, these tests seem even more important for CE method validation, than for HPLC method validation. However, in the literature, a robustness test only rarely is included in the validation process of a CE method, and usually only linearity, precision, accuracy, specificity, range, and/or limits of detection and quantification are evaluated. Robustness tests are described in references 20 and 59-92. Given the instrumental transfer problems for CE methods, a robustness test guaranteeing to some extent a successful transfer should include besides the instrument on which the method was developed at least one alternative instrument. 

The IMER approach does not require that the enzyme be placed in close proximity to the detector if the transducer signal is generated by a soluble product or cosubstrate of the enzymatic reaction. In the latter case, a variety of flow systems and postreactor detectors can be utilized to produce simultaneous determinations of the concentrations of several analytes. For example, an IMER can be combined with a high-performance liquid chromatography (HPLC) instrument (perhaps also in combination with mass spectroscopy) for purposes of both qualitative and quantitative analysis. The chemo-, stereo-, and regio-selectivities of enzymes facilitate separation and/or identification of analytes that may be present as different isomers (e.g., in peptide analysis based on use of peptidase IMERs in combination with these techniques to obtain structural information about the sequence of amino acids in peptides). 

A single MW-triggered HPLC instrument represents the total capabilities of this technology within HTP and is generally employed at capacity. Therefore this technique must often selected only when necessary, such as for the... 

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