Filling injector

As a rule, the molds are filled pneumatically. This can be accomplished with a blower centered over the filling injectors. The air blown in is removed through perforated walls, or through special devices. It is also possible to suck in the material by applying a vacuum in the mold. It is practical to add to the prefoamed material the foam accumulated during cutting, as reclaim rates up to 20% are possible without quality deterioration. 

FIGURE 1.193 Mold with filling injector and pressure filling container... 

The most important equipment part is the filling injector (Figure 1.203). It is needed to transport the foam particles into the molds. 

For filling, the spindle sleeve is pneumatically retracted, and the compressed air for the venturi nozzle is turned on. A vacuum is applied to the filling injector and the material hose. This vacuum sucks the foam particles out of the filling container. 

In the load position the sampling loop is isolated from the mobile phase and is open to the atmosphere. A syringe with a capacity several times that of the sampling loop is used to place the sample in the loop. Any extra sample beyond that needed to fill the sample loop exits through the waste line. After loading the sample, the injector is turned to the inject position. In this position the mobile phase is directed through the sampling loop, and the sample is swept onto the column. 

Slagt et al. [134] have stated that because of their thermal instability and reactivity sultones could not be easily analyzed by gas chromatography. They studied the two methods published by Martinsson and Nilsson using a Carlo Erba Fractovap G1 equipped with a flame ionization detector and a glass column (length 0.65 m OD 1/4 in.) filled with 10% OV 1 on Chromosorb W-AW (80-100 mesh). The column temperature was 230°C and the injector/de-tector temperature 275°C. The gas flow rates were N2 25 ml/min (carrier gas), H2 25 ml/min, and air 250 ml/min. One microliter of sample was injected. 

Automated gel permeation chromatograph (Cleanup XL, Abimed Gilson) equipped with 5-mL loop and chromatographic tube, 25-mm i.d., 600-mm long, filled with 52-g of Bio-Beads, S-X3, 200 00 mesh, 33-cm gel bed length GC Gas chromatograph equipped with a split/splitless injector, autosampler, DB-1 fused-silica column, 30 mx 0.25-mm i.d., 0.25-p.m film thickness and electron capture detector... 

For HPLC, the injector is a valve. In the charge position, a 50- jL syringe is used to fill the sample loop that holds a specific volume of sample solution. The valve is switched to the run position, and the eluent carries the sample out of the sample loop and into the column (auto samplers are also available for HPLC). A recording of the detector output is automatically started at the time of injection and produces a chromatogram of the separated components. 

The loop injector is a two-position valve that directs the flow of the mobile phase along one of two different paths. One path is a sample loop, which when filled with the sample causes the sample to be swept into the column by the flowing mobile phase. The other path bypasses this loop while continuing on to the column, leaving the loop vented to the atmosphere and able to be loaded with the sample free of a pressure differential. Figure 13.7 is a diagram of this injector, showing both the load and inject positions and the path of the mobile phase in both positions. 

Your instructor will discuss and/or demonstrate how to make an injection. With the injector valve in the load position, flush the injector s sample loop with the sample, and then make certain that the sample loop is completely filled. Turn the valve to inject and simultaneously activate the data system. The chromatogram should begin to be traced on the monitor. 

The analyst may either 1) install a smaller loop on the injector, or 2) partially fill the current loop, using the syringe to measure the volume. 

An injector valve operates in two modes— the fixed-loop mode or the partial-loop mode. In the fixed-loop mode, a sample is overfilled into the loop at 2-4 times the loop volume and the entire loop content is injected. In the partial-loop fill mode, a variable sample aliquot, measured precisely by a syringe at <50% of the loop volume, is injected. Note that the sample slug is introduced into the end of the sample loop and is back flushed onto the column to minimize band dispersion by the sample loop (Figure 9). Due to the emphasis on productivity, manual injectors are seldom used in the pharmaceutical laboratory except for preparative applications. 

The explosive oil (usually dinitrodiglycol) was used in the form of an aqueous emulsion. It was drawn from a wooden container lined with lead and introduced through a feeder into a water injector in which the aqueous emulsion formed. This emulsion was introduced into the mixer, filled with an aqueous suspension of nitrocellulose (Fig. 268). 

Injector volume. The volume of carrier gas (mobile phase) required to fill the injection port of the chromatograph. 

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