A pillar array column with a perfectly ordered internal structure has a higher separation efficiency than a particle-packed column used in conventional high-performance liquid chromatography. However, applying the pillar array column technology to quantitative analysis is challenging as the injection volume of the sample varies for each injection. This occurs because the sample volumes are in the order of nanoliters and the sample is injected manually. In this study, an automated sample injection system was developed to solve this problem. The system was composed of two pumps (one for the sample and other for the mobile phase), a six-way valve that can be controlled by a PC, and an autosampler. The peak height deviation, which is more than 20% in the conventional manual injection system, was improved to 1.2% and 0.4% for the two coumarin dye samples. This result indicated that the automated sample injection method developed in this study could be applied to pillar array columns to allow for quantitative analysis.

In our previous study, we developed an automatic sample injection system for pillar array columns for quantitative analysis. An autosampler was used to maintain a constant sample injection volume. However, the sample was diluted during injection using the autosampler, thus deteriorating the analytical reproducibility. In this study, we have substituted the autosampler with a syringe pump to overcome the abovementioned problem and improve the system. Sample dilution was avoided by filling the entire capillary with the sample at a constant rate. This improved system also increased the analytical reproducibility. In the previous system, the relative standard deviation (RSD) exceeded 17% of the peak height for coumarin dyes. In contrast, the improved system decreased the RSD to the range 1.2–1.8%. The analytical reproducibility was evaluated by using five types of amino acids. The RSD of each peak height was within 3.0%, confirming good reproducibility. These results indicate that the sample injection method developed in this study can be applied to biological sample analyses as a simple quantitative analysis method for pillar array columns.