Sample loadability

A buffering BGE co-ion gives better sample loadability. pH Adjustment of the sample by dilution could improve the peak shape. 

Alteration of the variables to permit a large scale preparation, mentioned as step (d) above, implies that it is essential to improve the resolution even if it means sacrifice in time. For the single component system, it is advisable to try to get as big a difference as possible in time between the preceding peaks and the major component, and between the major component and the succeeding peaks. When the major component is well separated from the other solutes, it is possible to introduce larger quantities of the sample on to the column. It is sometimes recommended that the solutes should have k values > 5 so as to increase sample loadability. 

Optimized conditions allow faster separations (threefold reduction), substantial increased injection volume capacity, reduced degradation of thermally labile compounds, and lower detection limits due to increased sample loadability. 

Abbreviations A automated sample application, D in situ instrumentalized detection, R automated chamber system, not applicable performance parameter, applicable performance parameter, number indicates the degree of importance or of difficulties. AC accuracy, LDQ lowest limit of quantitation, LLD lowest limit of detection. LR linearity and range, PR precision, REP reproducibility, RU ruggedness. SE selectivity. SL sample loadability, ST sample stability. 

An on-line coupling of capillary electrophoresis or reversed anionic capillary isotachophoresis (CITP) with electrospray ionization mass spectrometry has been described for the separation of monophosphate nucleosides, pyridine, and flavin dinucleotides (87). The combination with CITP gives an enhancement of sample loadability and concentration sensitivity in capillary zone electrophoresis/ mass spectrometry (CZE/MS). MS-compatible buffer systems were developed (trailing electrolyte, 10 mM caproic acid pH 3.4 leading electrolyte, 7 mM HCl/ 13 mM P-alanine pH 3.9). This technique seems to be valuable for the trace analysis of DNA and RNA, e.g., to study radiation-induced DNA damage. 

Fraction volumes are on the order of 200 mL to 1 L or more. A low 0.1% level impurity, with poor sample loadability and a complicated sample matrix can aggravate the situation with regards to project turnaround times and total solvent costs. Impurity fraction solution stability issues exacerbate the situation even more. For example, substituted benzylic alcohols can dehydrate under acidic HPLC conditions, or carboxylic esters can hydrolyze in aqueous mobile phase. A RP-HPLC isolation can yield solvent costs on the order of 50-200 with a turnaround time of approximately 1 week to yield the quality sample necessary for NMR analysis. 

In addition, support-coated open tubular (SCOT), porous-layer open tubular (PLOT), and wall-coated superior capacity open tubular (WSCOT) columns are applied. In a SCOT column, the column wall is coated with a thin layer of small inert particles that serve as a support for the stationary-phase liquid. The SCOT column provides a higher sample loadability at the expense of separation efli-... 

---