Self-contained SEC instruments

The Waters Associates 150C GPC, however, has set the standard for high-temperature SEC. It is microprocessor-controlled and designed for safety, ease of use, flexibility and speed of operation [2]. 

Two areas of safety are important—toxicity of solvent and flammability. The unit is entirely encased, and has an efficient exhaust system coupled to multiple sensors which trigger audible alarms and eventual shutdown if the 

Up to sixteen separate samples can be loaded on to the carousel and their chromatographic characteristics (flow rate, sensitivity, scale factor, delay time before injection, run time and number of injections up to a maximum of 9), separately loaded into the microprocessor for automatic analyses. The instrument has three compartments which are separately thermostatted-pump, injector and column compartments. The upper temperature is 150°C. The temperature of the compartments are controlled by proportional heaters allowing slow heating and cooling rates to be adopted if required. This minimizes thermal shock to the gel columns and also overheating—two features which help to prolong the life of the columns. 

Dual pumps deliver solvent at a constant flow rate to the sample and reference sides of the instrument. The standard pump heads deliver solvent at a rate of 0.1-9.9cm min irrespective of system pressure, but work best at 0.1-3.0cm min However, preparative pump heads are available which increase this range to 0.2-19.8 cm min A pre-pump ensures the consistency of the flow rate by supplying a head of solvent to the system. 

The column compartment is reasonably large and can hold up to ten 60-cm X 1-cm analytical columns as well as the differential refractometer—the only standard detector supplied. Other detectors can be fitted (IR, UV, viscometers and LALLS), but these are normally fitted externally and require heated extension tubes with additional plumbing to the equipment. The refractometer has a sensitivity of 1 x 10 RI units full-scale deflection, with an average noise level of 5 x 10 RI units. A quartz halogen bulb light source is used for increased sensitivity. Very good temperature control is required when using a RI detector. 

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