Post Column Apparatus

If post-column modification of the mobile phase or analyte is required, then the system will have a post-column apparatus in the flow path. Modification of the mobile phase (e.g. addition of buffers, changing the pH, and solvent strength) may be needed to enhance the compatibility of the mobile phase with the detector, while post-column derivatization of the analyte may be needed to improve the detection properties of the analytes after their separation. In either case, a post-column addition system consists simply of a reagent-delivery pump, a mixing-tee, and a mixing coil. Typically, a pressurized reservoir is commonly used to deliver a pulseless flow of the reagent. The vessel is usually fitted with a check value to prevent reagent back-up. The major drawback of using a pressure-based delivery system is that it can not handle a great deal of system back-pressure. Hence, close attention must be paid to the minimization of post-column back-pressure sources. Any single-piston pump, even with extensive pulse dampening, is usually inadequate for high-sensitivity work.

Delivery of the post-column reagent to the chromatographic eluent flow is accomplished via a mixing tee. The mixing tee should be a low dead-volume fitting. Probably the most crucial component in the post-column system is the mixing coil, which connects the mixing tee to the detector. It is essential that the mixing coil produces a homogeneous solution in the most efficient manner, in other words, with minimal band-broadening. The best mixing is obtained with a woven/knitted reaction coil. The three-dimensional weave achieves efficient mixing and effectively reduces band-broadening effects by preventing laminar flow patterns. In addition, their open-tubular nature produces less back-pressure than packed-bed reactors, and woven reactors are easy to make using commercially available TeflonĀ® tubing.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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