The helium carrier gas was then led into the injector. Although attempts were made to use the original injection assembly, it was
found that the quartz liner suffered from high temperature water erosion and the interior surface area of this injector was large enough that it required extra humidification, which ultimately dis- rupted operation. To circumvent this problem, a simplified injector was constructed from a 1/16 SS Swagelok tee union (Calgary Valve and Fitting) that was fitted to the original heating block. Carrier gas entered and exited this union at opposing ends, while sam- ple was injected perpendicular to this through a septum fitted into the remaining port. This injector was normally kept at 220 ◦ C (but lower temperatures were also possible depending on the analyte) and was found to operate more stably. A SS injection liner designed for the original injector is being developed for exploration in future experiments.
A length of 316 SS tubing (1/16 O.D. × 250 m I.D. × 30 m; Chro- matographic Specialties) was used as the separation column, since fused silica readily erodes at high temperature in the presence of water. For example, in our experience, only around 80–100 ◦ C is required to completely deteriorate a humidified fused silica capil- lary in a short period of time. The SS column led from the outlet of the injector and was connected to a 50 m I.D. × 11 cm long fused silica capillary restrictor (Polymicro Technologies, Phoenix, AZ, USA) via a zero dead volume union (Vici-Valco, Houston, TX, USA). The end of this restrictor was placed at the base of the flame in the FID jet to deposit column effluent directly into the detector. This fused silica restrictor was replaced about every 10–12 operational hours after deterioration due to hot water exposure was noted. The FID was set to a temperature of 300 ◦ C and the typical gas flows used were 88 mL/min of hydrogen (Praxair) and 740 mL/min of medi- cal grade air (Praxair). The hydrogen flow rate was occasionally increased to aid in flame stability if required.
The helium carrier gas was then led into the injector. Although attempts were made to use the original injection assembly, it was
found that the quartz liner suffered from high temperature water erosion and the interior surface area of this injector was large enough that it required extra humidification, which ultimately dis- rupted operation. To circumvent this problem, a simplified injector was constructed from a 1/16 SS Swagelok tee union (Calgary Valve and Fitting) that was fitted to the original heating block. Carrier gas entered and exited this union at opposing ends, while sam- ple was injected perpendicular to this through a septum fitted into the remaining port. This injector was normally kept at 220 ◦ C (but lower temperatures were also possible depending on the analyte) and was found to operate more stably. A SS injection liner designed for the original injector is being developed for exploration in future experiments.
A length of 316 SS tubing (1/16 O.D. × 250 m I.D. × 30 m; Chro- matographic Specialties) was used as the separation column, since fused silica readily erodes at high temperature in the presence of water. For example, in our experience, only around 80–100 ◦ C is required to completely deteriorate a humidified fused silica capil- lary in a short period of time. The SS column led from the outlet of the injector and was connected to a 50 m I.D. × 11 cm long fused silica capillary restrictor (Polymicro Technologies, Phoenix, AZ, USA) via a zero dead volume union (Vici-Valco, Houston, TX, USA). The end of this restrictor was placed at the base of the flame in the FID jet to deposit column effluent directly into the detector. This fused silica restrictor was replaced about every 10–12 operational hours after deterioration due to hot water exposure was noted. The FID was set to a temperature of 300 ◦ C and the typical gas flows used were 88 mL/min of hydrogen (Praxair) and 740 mL/min of medi- cal grade air (Praxair). The hydrogen flow rate was occasionally increased to aid in flame stability if required.
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