Columns flow rate and

Detection requirements in preparative-scale chromatography also differ from analytical erations where detectors are selected for their sensitivity. Sensitivity is not of overriding importance in preparative-scale chromatography the ability to accommodate large column flow rates and a wide linear response range are more useful. The sensitivity of the refractive index detector is usually quite adequate for prqtaratlve work but the ... 

Compatible with normal column flow-rates and solvents. 

FIGURE 14.9 Performance of short column ultrahigh pressure nano LC system at 10 /rL/min for the separation of tranylcypromine sulfate, perphenazine, and their impurities. Nano LC may be operated at 10 times optimum column flow rate and achieve ultrahigh throughput and reproducibility. Short column (3 cm x 150 /mi inner diameter) was packed with 1.8 /im C18 particles. Solvent A was water with 0.4% ammonia solvent B was acetonitrile with 0.4% ammonia. Gradient 0 to 1 min, 3 to 10% B 1 to 1.3 min, 10 to 35% B, 1.3 to 3.5 min, 35 to 90% B held at 90% B through 4.9 min and then returned to 3% B. Column head pressure was 7200 psi. 

Figure 25-13 Gradient elution of the same mixture of aromatic compounds in Figure 25-12 with the same column, flow rate, and solvents. The upper trace is the segmented gradient profile, so named because it is divided into several different segments.

Depending on the choice of column, flow rates and temperature program are important parameters for the qualitative analysis of citrus oils. It is also important to have the same temperature program for quantifying compounds. Replication of injections for generating a standard curve is vital. Injections should be done on the same day by the same technician. A standard curve with an R2 value >0.9 is sufficient. 

Lor a particular analytical separation, each biosolute will have an optimal k] value for maximum resolution with a designated column, flow rate, and mobile phase composition. Similar criteria apply in preparative (overload) chromatography with multicomponent mixtures, where resolution is similarly enhanced following optimization of chromatographic selectivity and zone bandwidth. The conventional approach to process purification with low molecular weight solutes has frequently been based on linear scale-up of the performance of an analytical column system. In these cases, high-resolution separations can be achieved often without the burden of conformational or... 

The katherometer detector is a mgged, very forgiving detector that can be quite seriously abused in operation and still provide accurate quantitative results. This, of course, is a direct result of its relatively low sensitivity. The main problem with the katherometer is instability due to poor control of operating and ambient conditions. The katherometer is very sensitive to temperature changes and changes in columns flow rate (the reasons have already been discussed). Consequently, the flow controller and the sensor oven controls must be well maintained to ensure a precise column flow rate and a precise... 

Molecular weight distribution is usually measured by GPC or other fractionation techniques. The accuracy of fraction separation depends on factors like the length of the column, flow rate and concentration. A common... 

This paper addresses the operating characteristics and performance of a 30pi TCD when coupled with a high resolution capillary gas chromatograph. Differences in the peak shape, peak symmetry, electronic bandwidth, column flow rates, and column bleed Invoke different responses for the TCD with a capillary column as opposed to a packed column. These differences raise several questions which will be addressed in this paper ... 

Other new developments in GC include the capability to analyse larger, more labile molecules using high GC column flow rates and the use of solvent-free syringeless injection, which allows inorganic materials to be introduced directly onto a heated injection port of a GC for thermal desorption There have been advances in headspace GC techniques also. ... 

Fig. 8. Effect of imraunoaffinity chromatography on HPLC-fluorescence analysis of lAA in an extract from dwarf-1 Zea mays shoots. Sample A. acidic, diethylether extract B. as A but extract subjected to immunoaffinity chromatography. Column 250x5.0 mm i.d. 5 p,m ODS Hypersil. Mobile phase 25 rain, 25-75% gradient of methanol in 1% aqueous acetic acid. Flow rate 1 ml min. Detector fluorimeter, excitation 280 nm, emission 350 nm. Sample C. lAA-like peak from B. Column, flow rate and detector as A and B. Mobile phase 35% methanol in 50 mM phosphate buffer and 20 mM tetrabutylammonium hydrogen sulphate at pH 6.5 [93].

Fig. 13. HPLC-RC analysis of Hj. H-labelled GAs by germinating Dalbergia dolichopetala seed. After a 4 day metabolism period, seeds were extracted with methanol and ca. 20 000 dpm aliquots analysed by reverse phase HPLC with column flow rate and detector, as in Fig. 12. Mobile phase 10-65% methanol in 1% aqueous acetic acid, over 30 min. Traces illustrate the metabolism of (A) [ H2, H2]GA, (B) [ H, H2]GA4, (C) [ Hj. HiiGA, and (D) [ H2, H2]GA2o. Peaks labelled F subsequently identified as free GAs, labelled G as GA glucosides and GE as GA glucosyl esters [23].

The column experiment is used to simulate the reference environment where the crushed test material (by itself or mixed with an aggregate) is used as a fill material. The laboratory column is filled with the test material and distilled water is pumped through the column. The contaminants are leached from the test material into the flowing water. The concentration of the contaminant of concern is at a peak at the beginning of the test and decreases with time. Hence, samphng should occur more frequently at the beginning of the experiment, depending on the column flow rate and the flux rate of the leached contaminant. 

A2.4 Example—Given a 50-m column of 0.21-mm inside diameter, inlet pressure of 220 kPa (gage), outlet pressure of 101 kPa (absolute), retention time of methane of 3.62 min, and flow out the splitter vent of 200 cmVmin, calculate column flow rate and split ratio as follows t 3.62 min = 217 s jl - (5000)/(217) - 23.0 cm/s... 

The carrier gas and the auxiliary gases for detectors are controlled by a set of pneumatic devices (pressure regulators, flow-controllers, and restrictors) to assure (a) reproducibility of the column flow rate, and thus retention times, in multiple analyses (b) adjustment of the gas linear velocity for optimal column efficiencies and (c) reproducibility of detector response for reliable quantitative measurements. In addition, filtering devices are inserted in the gas lines to purify all gases mechanically and chemically. 

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