Abstract: A syringe of relatively simple construction which is capable of both accurate and reproducible sample volume withdrawals, including volumes of 1.0 .mu.l or less, is provided. The syringe drive mechanism is preferably adapted for use in a liquid sampling apparatus and includes a threaded lead screw, a drive for rotating the screw, and a syringe having a plunger for withdrawing a liquid sample. The plunger is mechanically connected to the rotating lead screw by a nut threaded onto the screw and a slider mechanism associated with the nut which also is secured to the plunger. The nut is designed so that lateral misalignment of the drive screw does not affect the precise linear movement of the slider mechanism, and consequently, the plunger. This provides a mechanism which is less expensive to assemble and align properly, but which has a high degree of accuracy and reproducibility.

Abstract: A heater/mixer device is disclosed for use with laboratory vials, test tubes, or similar containers containing liquids. The heater/mixer includes a chamber formed in a block of material such as aluminum, with an electric heating element in contact with the block. The vial fits loosely in the chamber. Compressed air passes into the chamber through an inlet in the block, so that the vial is revolved by a circular air flow in a vortex fashion. This revolving motion creates a vortex in the liquid inside the vial, and so mixes the liquid. The air circulation also improves heat transfer from the block to the vial.

Abstract: A conventional injection valve, such as used in high performance liquid chromatography apparatus, having six ports and three channels for connecting the ports in two different positions, is modified so that one of the channels is longer than the other two. In this way, when the valve is switched to the load position, one of the ports is always connected to the channel prior to the other port being connected. This improvement in the valve makes the valve more accurate and reduces undesirable mixing of sample and mobile phase in the valve when injecting small quantities of sample.

Abstract: A pushloop liquid sampling method is an improvement in the method of introducing liquid samples into test equipment (such as for liquid chromotography) via a six port valve. The method involves pulling the sample completely past the sample loop in the six port valve and then pushing the desired amount of sample back into the sample loop.

Abstract: A process removes FMOC--OH which is an undesirable by-product of the derivatization of amino acids by FMOC. The process uses a silicone rubber membrane extractor cell. The sample containing the FMOC--OH is held in a silicone rubber tubing, while pentane flows past the outside of the tube; the FMOC--OH is thus extracted from the sample into the pentane. The process is integrated into a conventional high performance liquid chromatography system and is readily automated.