Septa capillary-inlet

The septum presents one of the most convenient but problematical of the basic components of a capillary inlet. It is located at the top or the front of the inlet and is the most commonly replaced part. Its role is to provide a means for conveniently introducing the sample without causing the system to leak or requiring special valves. Septa generally require replacement every 30-50 injections. 

Figure 6. Diagram of our 1-atm ion mobility spectrometer (IMS) apparatus (a) stainless steel source gas dilution volume, (b) septum inlet, (c) needle valve, (d) Nj source gas supply, (e) source and drift gas exhaust, (f) flow meter, (g) pressure transducer, (h) insulated box, (i) drift tube, (j) ion source, (k) Bradbury-Nielson gate, (I) Faraday plate/MS aperture, (m) drift gas inlet, (n) universal joint, (o) electrostatic lens element, (p) quadrupole mass filter, (q) 6"-diffusion pump, (r) first vacuum envelope, (s) channeltron electron multiplier, (t) second vacuum envelope, (u) 3"-dif-fusion pump, (v) Nj drift gas, (w) leak valve, (x) on/off valves, (y) fused silica capillary, (z) 4-liter stainless steel dilution volume, (aa) Nj gas supply.

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

One neck of the flask was covered with a septum for the removal of samples by a syringe equipped with a stopcock. Potassium slloxanolate catalyst was pipetted Into the flask. The flask was then Immediately fitted with the argon Inlet and heated by a silicone oil bath. Samples were removed at various times and put Into sample vials which were capped with septums. These were stored In a refrigerator until analysis by HFLC, Some samples were analyzed immediately by capillary gas chromatography. 

When on-column injection is used the end of the transfer capillary is inserted into the column inlet or retention gap where decompression of the supercritical fluid occurs. Carbon dioxide gas exits through the column and the seal made between the restrictor and septum (unless a closed injector is used). The analytes are focused by cold trapping in the stationary phase. The transfer line must be physically removed from the injector at the completion of the extraction to establish the normal carrier gas flow for the separation. Analyte transfer to the column is virtually quantitative but blockage of the restrictor is more conunon and involatile material accumulates in the injection zone eventually degrading chromatographic performance. The on-column interface is probably a better choice for trace analysis of relatively clean extracts with modest fluid flow rates than the split interface. When optimized both the on-column and split interfaces provide essentially identical peak shapes to those obtained using conventional solution injection. 

A three-necked 5-L Morton flask is fitted with an overhead mechanical stirrer, a nitrogen inlet adapter, and a rubber septum and charged with toluene ( 3 L) and niobium pentachloride (187.3 g, 0.693 mol). The mixture is cooled in an ice bath. A 1-L Schlenk flask is charged with tetrahydrofuran (315 mL, 3.88 mol) and tributyltin hydride (202 g, 0.694 mol) and fitted with a rubber septum. This solution is added, via cannula,f over 20-30min to the vigorously stirred toluene suspension. Shortly after the addition is completed ( < 10-20 min), the solution is filtered and the solid is washed with toluene (200 mL) and pentane (2 x 300 mL) and dried in vacuo for 12h ( < 1 mm). Yield, 249 g (95%)J of a free-flowing yellow powder is obtained. Melting point (sealed capillary) = 127-137°C dec. (lit. 145°C) IR (cm , Nujol mull) V 990, 820. 

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