Column length decreasing

Density Control and Programming. Since the pressure drop across the column length decreases the selectivity and, hence, resolution of mixture components (6,8,13), it is very important to minimize the pressure drop across the column using a restrictor at the column outlet. Typically, the desired restriction is achieved... 

Now if Vi = V2 (i.e., if = SqLq), the amount of continuous phase that the upper part (EF) loses as it attains equilibrium is just equal to the amount the lower part needs. Thus, at equilibrium, the s profile is given by curve (AFB) and the length of the column remains unchanged. On the other hand, if El> V2 (i.e., if sqLo> Vc) (see Fig. 11b), the upper part must lose a greater amount of liquid than the lower part requires (i.e., the lower part will gain more continuous-phase liquid than it can hold). As a result, the excess separates out and the column length decreases. The final profile is now given by... 

The efficiency obtained from an open tubular column can be increased by reducing the column radius, which, in turn will allow the column length to be decreased and, thus, a shorter analysis time can be realized. However, the smaller diameter column will require more pressure to achieve the optimum velocity and thus the reduction of column diameter can only be continued until the maximum available inlet pressure is needed to achieve the optimum mobile phase velocity. 

The analytical capability of a SEC column is sometimes judged by the peak capacity, which is the number of unique species that can be resolved on any given SEC column. This number will increase with decreased particle size, increased column length, and increased pore volume. Because small particlesized medium generally has a lower pore volume and a shorter column length, peak capacities of ca. 13 for fully resolved peaks can be expected for high-resolution modern media as well as traditional media, (see Eig. 2.5). It was found that SEC columns differ widely in pore volume, which affects the effective peak capacity (Hagel, 1992). 

The effect of flow rate on resolution by Toyopearl HW-55F and Toyopearl HW-55S columns has been studied using a bovine serum albumin sample. Eor both columns, resolution decreased with increasing flow rate (46). Resolution is increased, however, with decreasing particle size (47). Resolution is proportional to the square root of the column length, as theoretically expected, and indicates that longer columns can be packed as well as shorter columns. Therefore, for samples difficult to resolve, the solution may be to increase the column length. 

Actually, the decrease in column length allows to reach log Poet values up to 7.8 using for example an ODP-50 carhidge with a reasonable analysis time [38]. Moreover the use of acetonitrile as organic modifier and a Discovery RP-amide-Cis... 

Injected quantity. When column length or internal diameter is reduced, the injected volume should be decreased proportionally to avoid any overloading of the column and variability of retention times. 

The peak volume is directly proportional to the square of the column diameter and the column length and decreases with Increasing column efficiency (decreases for smaller particle packings). The concentration at the peak maximum, C—, is given by... 

The separation number, section 1.4, is dependent on the nature of the stationary phase, the column length, column temperature, and carrier gas flow rate. The separation number tends to increase as the coluam temperature decreases. At a... 

When k is already within the optimum range of values and the resolution is still marginal, the best solution is to increase N. This is generally achieved by increasing column length or by decreasing the flow rate of the mobile phase. 

Furthermore, it is possible to increase the efficiency by a factor 3 when changing particle size from 5 to 1.7 pm while maintaining an equivalent column length, and decrease analysis time by a factor 9 while maintaining equivalent efficiencies [21],... 

With increasing analysis time, S, 10, and 15 min, there is a marked decrease in the inlet pressure, 18.2,9.1, and 6.2 atm, respectively (see Table V). Both the necessary particle diameter, 5, 7, and 8.5 fim, respectively, and the column length, 8.5, 11.5, and 14 cm, respectively, increase with the analysis time. On the other hand, an increase in efficiency at constant analysis time is accompanied by a slight increase in column length, a... 

The main contributions are the sample volume and the profile of the injected band characterized by both the injection volume and the injection time 16, 20, 27, 5). We want to calculate the maximum permissible sample size which causes a relative increase in the zone width by a factor 6, hence a decrease in the efficiency by 0. The sensitivity depends little on the column length at constant plate number if the maximum sample size is used in all cases. 

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