Electronic pressure-controlled injection

Applications On a comparative basis, HTGC is a relatively new tool and extremely valuable for the analyses of extracted polymer additives, as shown by industrial problem solving. For satisfactory analysis of in-polymer additives by HTGC two specific conditions are to be met. The instrument should be equipped with a cool on-column injection port to better preserve some of the additives and/or their by-products that may be thermally labile. The instrument must also have electronic pressure control so that some of the very high-boiling components, such as Irganox 1010, are... 

TTie pneumatics also optimize the performance of the spht/sphtless inlet. Its forward pressure control in sphtless injection mode significantly reduces the risk of sample loss and maximizes accuracy and reproducibihty. TTie provision of mass flow control coupled with back pressure control in the spht injection mode maximizes reproducibihty and accuracy and also allows electronic adjustment of spht ratios. The net result is that sample-introduction conditions are optimized individually for the two most popular injection techniques. In addition, parameters are recorded in the methods file. 

A column consisting of a deactivated silica-based stationary phase is used for the packed-column mode. A packed column allows larger volumes of sample solvent to be injected, thus improving sensitivity. Generally, the column dimensions are 1 x 100-250 mm and the particle size is 5 / m. Commercial SFC instruments are also available that will handle the classical 4.6 x 150-mm or 250-mm columns. With the introduction of electronically controlled variable restrictors to control the back pressure, the packed columns are becoming increasingly more popular. This feature allows the independent flow and pressure control of mobile phases, thus helping in rapid optimization of selectivities. Some of the commonly used packed columns are as follows ... 

A schematic block diagram illustrating an entire DP-SCD detection system is shown in Fig. 2. An analytical system consists of a gas chromatogr h equipped with a split/splitless iigector with the option of a Pressurized Liquid Injection System (PLIS), wifli or without low diermal mass gas chromatogr q)hy apparatus, for sample introduction and sulfur speciation (if required) an electrically heated burner with an interface that controls the burner gas flows and temperature and a detector that contains a chemiluminescent reaction cell, ozone generator, optical filter, amplifier, and electronics. Lastly, a vacuum pump is used to keep file reaction cell under low pressure conditions to prevent loss of chemiluminescent species and to reduce collisional quenching. 

From the 1980s to early 2000s, control of PM was mainly accomplished using technologies that improved engine combustion, most successfully with the common-rail system, i.e., an electronically controlled high-pressure fuel injection system. However, as more severe emission regulations have been enforced worldwide, the adoption of after-treatment systems that directly remove exhausted PM has become inevitable. 

M. Nuti, M Variable Timing Electronically Controlled High Pressure Injection System for 2S S.I Engines, SAE 900799, Society of Automotive Engineers, Warrendale, Pa., 1990. 

All diesel fuels tend to contain trace water, expressed in parts per million (ppm). With the veiy high fuel injection pressures now used in electronically controlled diesel engine, fuel-filter/water separators are widely used, since water allowed to circulate freely through the injection system can result in seizure of components and erosion of injector orifice holes, and in extreme cases the high compressibility factor of water can blow the tip off of the fuel injector. 

An alternative form of split injection is the timed split technique, Figure 6.11 [130,131,133]. In this case the column is connected directly to the valve and the valve actuator is controlled electronically to turn the valve to the inject position and back very rapidly with only a portion of the sample in the loop displaced to the column. Timed split allows variable volumes to be injected by changing the valve actuator tine and provides more reproducible splitting than the dynamic split technique. However, it suffers from many of the same problems as dynamic split, namely, poor accuracy, split ratios that depend on pressure, and high detection limits. 

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