3.1. Optimization of the signal form and reproducibility
The signal profile is partly controlled by the geometry of the injector and of the capillary system. The liner, a glass insert in the injector, plays the most an important role. With other conditions constant, a large liner broadens the signal in direct proportion to its volume. We have tested two different liners: a standard one with i.d. of 2 mm and one with i.d. of 4 mm. For the same conditions, the smaller liner gives narrower peaks. The volume of the capillary plays a similar role to the liner in that a broader capillary led to a broadening of the signal. Three capillaries have been tested: 0.53, 0.32 and 0.1 mm i.d. The influence is smaller than the effect of the liner, because the volume of the capillary is much smaller. The differences are not very significant, so we have used the 0.32 mm i.d. capillary.
The temperature of the injector (and of the capillary) significantly influences the form of the signal. Table 1 reproduces the changes in height of the signal with changes in temperature. As can be seen from this table, decreasing the injector temperature from 280 to 150°C has a significant effect on the height and the width of the signal. The peaks become broader and smaller, so that the peak integration is less accurate. The injector has to be maintained at a temperature higher than the boiling point of the main volatile substances analyzed; these conditions produce narrow and high peaks, which are easier to interpret.
3.1. Optimization of the signal form and reproducibility
The signal profile is partly controlled by the geometry of the injector and of the capillary system. The liner, a glass insert in the injector, plays the most an important role. With other conditions constant, a large liner broadens the signal in direct proportion to its volume. We have tested two different liners: a standard one with i.d. of 2 mm and one with i.d. of 4 mm. For the same conditions, the smaller liner gives narrower peaks. The volume of the capillary plays a similar role to the liner in that a broader capillary led to a broadening of the signal. Three capillaries have been tested: 0.53, 0.32 and 0.1 mm i.d. The influence is smaller than the effect of the liner, because the volume of the capillary is much smaller. The differences are not very significant, so we have used the 0.32 mm i.d. capillary.
The temperature of the injector (and of the capillary) significantly influences the form of the signal. Table 1 reproduces the changes in height of the signal with changes in temperature. As can be seen from this table, decreasing the injector temperature from 280 to 150°C has a significant effect on the height and the width of the signal. The peaks become broader and smaller, so that the peak integration is less accurate. The injector has to be maintained at a temperature higher than the boiling point of the main volatile substances analyzed; these conditions produce narrow and high peaks, which are easier to interpret.
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