Columns short fast

Asperger A. et al., 2002. Trace determination of priority pesticide in water by means of high-speed online solid-phase extraction-liquid chromatography-tandem mass spectrometry using turbulent-flow chromatography columns for enrichment and a short monolithic column for fast liquid chromatographic separation. J Chromatogr A 960 109. 

Combinatorial chemistry techniques produce hundreds, if not thousands, of samples that need to be analyzed in a relatively short period of time. While fast HPLC analyses with short columns and fast gradients have increased throughput, there are still limits on the number of samples that can be processed. Some systems have evolved that incorporate multiple injectors, pumps, and UV detectors, but are still limited by having only one mass spectrometer available for detection and analyte identification. 

The resulting very sharp peaks are then released onto the short fast column 2. The modulator actually collects eluent from column 1 every few seconds (generally 2-9 s), and so an individual chromatographic peak is actually sliced into many fragments. Figure 15.5 demonstrates how two overlapping peaks are effectively deconvoluted into two interleaved series of pulses. 

The HPLC method development requirements using short columns and fast HPLC to determine the assay concentration for each polymorph at the different temperatures are the same as for solubility determination. However, for stability evaluation of the different polymorphs a stability-indicating HPLC method should be used. 

Metabolite ID 1.4 operates in both interactive and batch mode. In the interactive mode, the user reviews the full-scan data prior to MS/MS generation. In batch mode, the user submits a list of samples to be analyzed and starts automated acquisition. With such automated approaches, the metabolic profile of a single compound can be evaluated in approximately 1.5 hours, provided that adequate separation can be achieved with short, narrow-bore columns and fast-gradient chromatography. 

Figure 5 (A) Schematic description of a multidimensional gas chromatography arrangement, where a switching system or valve (V) is located between the two columns. The process of switching the flow between and or to the monitor detector (det M) is not shown. The auxiliary flow (aux) provides flow to the system to assist in the switching process, and/or to provide make-up flow into the column, which Is not receiving flow from the precolumn. is normally a column of regular dimensions, and may incorporate a cryofocusing step at the head of the column. (B) The comprehensive two-dimensional gas chromatography arrangement essentially only requires a mechanism for modulation between the two columns, which provides a series of narrow peaks (at least four normally) to for each D peak. The modulator (M) is shown near the column connection. is normally a short, fast elution column.

Another GC-MS application of considerable potential is with comprehensive gas chromatography (GC X GC). A short fast column follows a longer standard column and fractions eluting from the first column are trapped and periodically released into the second (fast) column. The second column has a stationary phase that is different from that of the first so that there is a tendency for the compounds that co-elute from the first column to separate in the second column. GC x GC requires full scan spectra for separations less than 20-30 s and TOF-MS is ideal for this speed of analysis. 

A major step in the miniaturization of HPLC columns was done early in 1967 by Horvath and coworkers, when investigating the parameters that influence the separation of nucleotides in a 1 mm I.D. column. These columns were then named microbore columns. A further step in the miniaturization process was done in 1973, by Ishii and coworkers, by separating polynuclear aromatic hydrocarbons (PAHs) in a 0.5 mm I.D. polytetrafluoroethylene (PTFE) column. The term micro-LC was then introduced to differentiate this technique from HPLC, which uses larger-bore columns.Shortly after, Scott and Kucera published several articles deahng with microbore (1 mm I.D. columns) LC. In spite of the fast development in its early days (late 1960s and early 1970s), the miniaturization of HPLC followed a slow progress until recently, with... 

Besides the numerous fast GC applications on citrus essential oils, other oils have also been subjected to analysis, such as rose oil by means of ultrafast GC [53] and very fast GC [54], both using narrow-bore columns. Rosemary and chamomile oils have been investigated by means of fast GC on two short conventional columns of distinct polarity (5 m x 0.25 mm ID) [55]. The latter oil has also been analyzed through fast HS-SPME-GC on a narrow-bore column [56]. Fast and very fast GC analyses on narrow-bore columns have also been carried out on patchouli and peppermint oils [57]. 

The timing regime of GCxGC should be relatively slow with a regular capillary column for the first dimension and a short fast GC column for the second-dimension separation. Usually both columns connected by a modulator interface are installed in the same GC oven. The second dimension column should be of a different polarity than the first one to provide different kind of... 

Branovic, K. et al. Application of short monolithic columns for fast purification of plasmid DNA. Journal of Chromatography, B Analytical Technologies in the Biomedical and Life Sciences, 2004 801(2) 331-337. 

However, in a countercurrent column contactor as sketched in Figure 8, the holdup of the dispersed phase is considerably less than this, because the dispersed drops travel quite fast through the continuous phase and therefore have a relatively short residence time in the equipment. The holdup is related to the superficial velocities U of each phase, defined as the flow rate per unit cross section of the contactor, and to a sHp velocity U (71,72) ... 

Finally, the speed of response of the detector sensor and the associated electronics once played an important part in optimum column design. The speed of response, or the overall time constant of the detector and associated electronics, would be particularly important in the analysis of simple mixtures where the analysis time can be extremely short and the elution of each peak extremely rapid. Fortunately, modern LC detector sensors have a very fast response and the associated electronic circuits very small time constants and, thus, the overall time constant of the detector system does not significantly influence column design in contemporary instruments. The instrument constraints are summarized in Table 2... 

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