Figure 10 System configuration for the automated, capillary-scale amino acid analyzer. Liquid chromatography is performed using a high pressure syringe pump (Isco 100-DM, Lincoln NE). The mobile phase exits the syringe pump through a set of check valves (C) and 0.2 µm stainless steel filters (F) prior to mixing. The volumetric flow from the pump is reduced from 6 to 0.3 µL/min using a fused silica capillary splitter and carried from the splitter to the autosampler using a short length of 50 µm i.d. capillary. The 50 µm i.d. packed capillary column is mounted directly to the low-dead volume injection valve. The electrochemical detector is similar to that described in previous figures.

doi:10.1201/9780203908907-227

Chapter

Figure 10 System configuration for the automated, capillary-scale amino acid analyzer. Liquid chromatography is performed using a high pressure syringe pump (Isco 100-DM, Lincoln NE). The mobile phase exits the syringe pump through a set of check valves (C) and 0.2 µm stainless steel filters (F) prior to mixing. The volumetric flow from the pump is reduced from 6 to 0.3 µL/min using a fused silica capillary splitter and carried from the splitter to the autosampler using a short length of 50 µm i.d. capillary. The 50 µm i.d. packed capillary column is mounted directly to the low-dead volume injection valve. The electrochemical detector is similar to that described in previous figures.

Chapter

Figure 10 System configuration for the automated, capillary-scale amino acid analyzer. Liquid chromatography is performed using a high pressure syringe pump (Isco 100-DM, Lincoln NE). The mobile phase exits the syringe pump through a set of check valves (C) and 0.2 µm stainless steel filters (F) prior to mixing. The volumetric flow from the pump is reduced from 6 to 0.3 µL/min using a fused silica capillary splitter and carried from the splitter to the autosampler using a short length of 50 µm i.d. capillary. The 50 µm i.d. packed capillary column is mounted directly to the low-dead volume injection valve. The electrochemical detector is similar to that described in previous figures.

ABSTRACT

A block diagram of the system is shown in Figure 10. In this configuration, the mobile phase dwell volume can be kept low by placing a mobile phase splitter as close to the

injection valve as possible. The system is not ideal, because lightly retained peaks (k<10 in aqueous mobile phase) will exhibit band broadening under isocratic conditions using this configuration because of the large volume of mobile phase that passes through the column during injection; however, the main goal here is to separate species that can be efficiently preconcentrated at the column head. Use of this system improved RSDs to 13% while maintaining comparable sensitivity, as shown in Figure 11.