Capillary Liquid Chromatographic Analysis Of Vitamins And Phytohormones In Corns

Due to its advantages of high separation efficiency and fast speed, high performance liquid chromatography (HPLC) has been widely applied in the fields of biological detection, environmental monitoring and so on. Miniaturization and automation have been two important trends in LC field, and micro or capillary liquid chromatography (CLC) has been used more and more. Compared with conventional LC, micro or capillary LC offers several advantages such as significant reduction of solvent consumption, small amounts of sample required. However, a minute sample injection volume and limited optical path length for on-column UV photometric detection in CLC result in its low detection sensitivity. In order to enhance the detection sensitivity in CLC, hyphenation with sample preconcentration techniques is needed. In this work, some on-column focusing technique such as in-tube solid-phase microextraction (SPME) and solvent gradient zone sharpening effect were investigated to enhance the detection sensitivity. The major content is described as follows:1. A sensitive CLC method has been proposed for the determination of water-soluble vitamins. An optical-fiber flow cell with a long light path in the UV detector was used to improve the detection sensitivity. The effects of some parameters on the separation (including methanol concentration and pH of mobile phase) were investigated. The detection limits (LODs) of the water-soluble vitamins are in the range from 14.6 to 53.5 ng/mL based on the signal-to-noise ratio of 3 (S/N = 3). The relative standard deviations (RSDs) of migration time and peak area for each water-soluble vitamins were less than 4.4%. The developed method was applied to the analysis of water-soluble vitamins in corns. Water-soluble vitamins were not detected in corn samples since the detection sensitivity of the developed method for water-soluble vitamins was not high enough to detect them due to their low contents in corns.2. A CLC method was developed for the analysis of phytohormones. An optical-fiber flow cell with a long light path in the UV detector and solvent gradient zone sharpening effect were combined to enhance the detection sensitivity. Some parameters, such as methanol concentration and sample matrix, were optimized. The LODs of the phytohormones are in the range from 27.2 to 196.1 ng/mL based on the signal-to-noise ratio of 3 (S/N = 3). The RSDs of migration time and peak area for each phytohormone were less than 2.8%. The method was applied to the analysis of phytohormones in different types of corns. Zeatin (ZT), gibberellin A3 (GA3) and indole-3-acetic acid (IAA) in corn samples were detected, in which GA3 and IAA were analyzed quantitatively.3. A CLC system with UV/Vis detection was coupled with an in-tube SPME device for the analysis of fat-soluble vitamins andβ-carotene. A monolithic silica-ODS column was used as the extraction medium. An optical-fiber flow cell with a long light path in the UV/Vis detector and solvent gradient zone sharpening effect were utilized to further enhance the detection sensitivity. In the in-tube SPME/CLC system, the pre-condition of the extraction column and the effect of the injection volume were studied. The LODs for the fat-soluble vitamins andβ-carotene were in the range from 1.9 to 173 ng/mL based on the signal-to-noise ratio of 3 (S/N = 3). The RSDs of migration time and peak area for each analyte were less than 5.0%. The method was applied to the analysis of fat-soluble vitamins andβ-carotene contents in different types of corns.α-tocopherol (VE) in corn sample was detected and analyzed quantitatively.