Septum purge

The septum purge flow is recommended to stay on as well during the injection phase. With properly chosen injection conditions keeping the solvent/sample vapour cloud inside of the insert liner, there will be no loss of sample analytes via the septum purge outlet (see Section 2.2.5.1 Hot Sample Injection). 

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Figure 14.10 Schematic diagram of the aromatics analyser system BP, back-pressure regulator CF, flow controller CP, pressure controller Inj, splitless injector with septum purge V, tliree-way valve column I, polar capillary column column 2, non-polar capillary column R, restrictor FID I, and FID2, flame-ionization detectors.

Fig 2. Apparatus for the desorption of volatiles Iron Tenax. A Splitter valve B Septum purge valve C Toggle valve... 

In both systems the flow of helium carrier gas through the columns was 0.7-0.8 ml min-1, with a septum purge of 0.5 ml min-1 and a split valve flow of 4-4.5 ml min-1. The injection ports were maintained at 260°C and the detector ovens at 240° C. The detector employed was either a flame ionisation or a nitrogen-specific NPD-40 thermionic detector (Erba Science (UK) Ltd) and the output was recorded on a HP 3390 integrator (Hewlett Packard Ltd, Wokingham, UK). 

Figure 2.5—Injectors, a) A split/splitless injector (the split is regulated by valve 2). The exit labelled 1 is called the septum purge, b) A cold on-column injector. A typical feature of a chromatogram obtained in the splitless mode is the interference of the solvent with the analytes. This can be avoided using a selective detector.

A 500-L solution containing 2 mg/L of free chlorine residual in distilled water was pumped onto the four-column system the columns were eluted and the eluants were processed as described earlier. This chlorine blank and resin eluant blanks were analyzed by GC-MS by using a Finnigan 4023 with the I NCOS data system and a 31,000-compound National Bureau of Standards library. Electron impact spectra were obtained by using an electron energy of 70 eV and a scan time of 1 s for the mass range 33-550 amu. A 30-m WCOT SE-54 fused-silica capillary column (J W Scientific) was used for separations. Injections were made with the oven at 40 °C and the door open, the injector at 220 °C, and the interface at 270 °C. Two minutes after injection, the door was closed and the temperature was raised ballistically to 60 °C, ramped at 4 °C/min to 280 °C, and held there for 4 min. The split and septum purge valves were closed for injection and opened after 1 min. 

Figure 6.11. Vented septum injector. Any gas coming in contact with the septum is vented out the septum purge line.

Figure 6.13. Inlet techniques for capillary columns (Hewlett-Packard Co.-Multipurpose glass inlet system). (A) Splitter type. (b) Splittless type with septum purge. ...

Figure 4.14 Sample injection ports, (a) Rash-vaporizer, (b) Split injector with septum purge for capillary columns, (c) Direct -cold on-column injection onto a capillary column showing rotating valve and insertion of needle into the base of the column. (Reproduced by permission of Dr Alfred I liithig Verlag from J. High Res. i hromuiogr., Chromalogr. Contniun., 2. 35.X (1979).)...

A 5890 Series II Hewlett-Packard equipped with a thermal conductivity detector (TCD) and a flame ionisation detector (FID) connected in series is used to analyse on line gas composition. The chromatograph has a septum-purged packed inlet. Series 530 pm columns can be fitted to the injector by means of proper adapters. Two columns are connected in series. Depending on the compounds to be analysed it is possible to choose among the following columns ... 

Figure 5.2.1. Simplified diagram of a Py-GC system (not to scale). The pyrolyser is schematized as a heated filament type. A piece of a deactivated fused silica line is passed through the injection port of the GC and goes directly into the pyrolyser. This piece of fused silica is connected to the column, which is put in the GC oven. The pneumatic system consists of (1) a mass flow controller, (2) an electronic flow sensor, (3) a solenoid valve, (4) a backpressure regulator, (5) a pressure gauge, and (6) septum purge controller. The connection (7) is closed when working in Py-GC mode, and connection (8) is open. (Connection (7) is open when the system works as a GC only.) Connection (9) is closed and connection (10) is open when the GC works in splitless mode (purge off). Connection (10) is closed and connection (9) is open when the GC works in split mode (purge on). No details on the GC oven or on the detector are given.

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