chromatography device liquid chromatography valve liquid chromatography valve A sample valve that must be able to sustain pressures up to 10,000 p.s.i., although it is most likely to operate on a continuous basis, at pressures of 3,000 p.s.i. or less. The higher the operating pressure the tighter the valve seating surfaces must be forced together to eliminate any leak. It follows that any abrasive material, however fine, that passes into the valve can cause the valve seating to become scored each time it is rotated which will ultimately lead to leaks. This will cause the sample size to vary between samples and eventually affect the accuracy of the analysis. It follows that any solid material must be carefully removed from any sample before filling the valve. The sample volume of an internal loop valve is situated in the connecting slot of the valve rotor and can be used only for relatively small sample volumes. Internal sample loop valves provide samples with volumes ranging from 0.1 ml to about 0.5 ml. Valve operation is shown in figure 6. The left-hand side diagram shows the load position. The sample occupies the rotor slot and has been filled by passing the sample from an appropriate syringe through the rotor slot to waste. While loading the sample, the mobile phase supply is passed through the valve directly to the column. To place the sample onto the column, the valve is then rotated and the valve slot containing the sample is now placed between the solvent supply and the column. As a result, the sample is passed into the column by the flow of solvent. PERSON:Daniel Schober chromatography device WEB:<http://www.chromatography-online.org/EC-Dispersion/HPLC-Sample-Valves/rs16.html> http://msi-ontology.sourceforge.net/ontology/CHROM.owl#msi_01110 metadata complete