Preparation and application of glass capillary columns

Method of preparation of glass capillary columns using etching process was examined. Glass capillary columns were prepared as follows: Borosilcate glass capillary tubes of 1520 m long and 0.250.30 mm inside diameter were washed with water, acetone and methyl alcohol. The capillary tubes were filled with 0.35% hydrofluoric acid (HF) solution at room temperature for 20 hours for etching treatment. Then, the tubes were washed with water and treated with 5% KOH solution overnight, and further washed with water and dried. Observation of the etched glass capillary columns with a scanning electron microscope showed fine irregularities (convex and concave unevenness) of 0.20.3 μm on the inside walls. Such irregularities were most noticeable in the columns treated with 2% HF solution. On the contrary columns treated with 5% HF solution which was more corrosive, had rather smooth inside walls. The etched glass capillary columns were then coated with silicone oil OV 101 as a stationary phase by the dynamic coating method. The efficiency of the columns thus prepared was tested by analyzing mixture of hydrocarbons (n-C6H14, n-C8H18, n-C10H22n-C14H30). On the tetradecane peak (capacity ratio k=46) thus recorded, each columns showed the following number of theoretical plates: untreated column: 12001600/m column treated with 0.3% HF solution: 12001600/m column treated with 1% HF solution: 18002500/m column treated with 2% HF solution: 20003000/m column treated with 5% HF solution: ≅2000/m From the above data, it is easily seen that the columns treated with 2% HF solution showed the highest performance. The k-HETP characteristics of the columns prepared under optimum etching conditions were measured at carrier gas velocity of 9.3 cm/s and 15cm/s and it was found that the slope is reduced at capacity ratio higher than 3, indicating that the columns permit the analysis of components having high capacity ratio without reducing the column efficiency. Further, application of the glass capillary columns to several samples was examined. PCBs, various mixture of steroids, perfumes and terpenes were analyzed using the glass capillary columns, packed glass columns and stainless steel capillary columns for comparisons. It was found that the glass capillary columns have higher resolution than packed glass columns and stainless steel capillary columns. The high performance of the glass capillary columns was clearly shown in the analysis of the perfumes and terpenes, that is, the influe