Open tubular column splitless

Injection into open tubular columns split routine for introducing small sample volume into open tubular column splitless best for trace levels of high-boiling solutes in low-boiling solvents on-column best for thermally unstable solutes and high-boiling solvents best for quantitative analysis... 

Figure 6.11 Schenatic diagran of a split/splitless valve injector (A) and a timed-split injector (B) for open tubular column SFC.

Figure 24-15 Representative injection conditions for split, splitless, and on-column injection into an open tubular column.

Figure 24-16 Split and splitless injections of a solution containing 1 vol% methyl isobutyl ketone (b.p. 118°C) and 1 vol% p-xylene (b.p. 138°C) in dichloromethane (b.p. 40°C) on a BP-10 moderately polar cyanopropyl phenyl methyl silicone open tubular column (0.22 mm diameter x 10 m long, film thickness = 0.25 m, column temperature = 75°C). Vertical scale is the same for A-C. In D, signal heights should be multiplied by 2.33 to be on the same scale as A-C. [From R J. Marriott and P. D. Carpenter, Copillory Gas Chromatography Injection," J. Chem. Ed. 1996, 73, 96.]...

Figure 5 compares chromatograms of A8- and A9-THC-TMS and 11-hydroxy-A8-THC-TMS obtained on a glass capillary column and a 6ft. x 2mm I.D. packed column. The retention times of the cannabinoids are comparable, but the resolution and sensitivity achieved on the capillary column is far superior. The capacity of the capillary column is of course far less than that of the packed column. Nevertheless, by using a Grob-type splitless injector (7) we are able to inject several microliters of solution containing up to 50 ng of each cannabinoid without overloading the column. Use of a support-coated open tubular column should increase the column capacity, but at some sacrifice of resolution and sensitivity. 

The split/splitless detector has been designed for use with open-tubular columns or solid-coated open-tubular (SCOT) columns. Due to the small dimensions of such columns, they have very limited sample load capacity and, thus, for their effective use, require sample sizes that are practically impossible to inject directly. The split injector allows a relatively large sample (a sample size that is practical to inject with modern injection syringes) to be volatilized, and by means of a split-flow arrangement, a proportion of the sample is passed to the column while the remainder is passed to waste. A diagram of a split/splitless injector is shown in Fig. 1. 

Figure 3.5. Schematic diagram of a hot split/splitless injector for open tubular columns, (From ref. [50] Perkin-Elmer Co.).

Figure 3 A hot split/splitless injector for open tubular column gas chromatography. (From Tipler A and Ettre LS (1997) The Prevent System and its Application in Open-Tubular Column Gas Chromatography. Norwalk Perkin-Elmer Corporation.)...

Figure 4 Suitable liners for direct splitless (left) and on-column (right) injection onto wide bore open tubular columns.

Figure 22-7 Injection port operation for (q) split, (b) splitless, and (c) on-column injection into an open tubular column. A slow flow of gas past the inside surface of the septum out to waste cools the rubber and prevents volatile emissions from the rubber from entering the chromatography column.

Standards with a poor UV chromophore (4-methyl-2-pentanone, 1-chlorododecane, and stearic acid) were analyzed on a Perkin-Elmer 3920 gas chromatograph with a flame ionization detector and a 30-m SE-54 wall-coated open tubular (WCOT) fused-silica capillary column (J W Scientific). The injector temperature was 200 °C the detector interface temperature was 280 °C. The carrier gas was He at 16.5 lb/in.2, and the makeup gas was nitrogen at a flow of 40 cm3/min. Splitless l-/zL injections of the 25,000 1 concentrates were made by starting with an oven temperature of 45 °C and the oven door open after 2.75 min, the oven door was closed and the temperature was programmed at 4 °C/min to 280 °C, which was held for 8 min. The syringe was kept in the injection port for 15 s after injection. 

The extracted degradation products were identified and quantified by a ThermoFinnigan GCQ (San Jose, CA, USA). The column used a wall-coated open tubular (WCOT) fused silica CP-WAX 58 (FFAP)-CB column from Varian (25 m x 0.32 mm id, od 0.2 pm). Helium of scientific grade purity from AGA (Stockholm, Sweden) was used as carrier gas at the constant velocity of 40 cm/s. The initial oven temperature was 40 "C, which was held for 1 minute. The oven was heated to 250 C for 15 minutes. Electron impact mode (El) detection was used with an electron energy of 70 eV. The mass-range scanned was 35-400 m/z and the ion source and transfer line temperatures were 180 and 250 C, respectively. The injector temperature was set to 250 C. A sample (1 pi) was injected in splitless injection mode and two blanks were run between each sample by injecting clean methanol (0.15 M HCl). 

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