Today, the main columns for high performance liquid chromatography (HPLC) are of tubular design, normally manufactured from high quality stainless steel and packed with spherical ceramic particles. Termination of the columns is via a metal frit held in place by an end fitting that can accept a 1/16 in (15.9 mm) male fitting to connect the column to the HPLC instrument.

Figure 1 shows a typical conventional HPLC column. This is now a mature design that has evolved over a period of 20 years. In that time, many variations have evolved, such as cartridge columns, removable end fitting columns, radial compression columns and nonmetal columns. Today, the most common analytical column has an inner diameter (i.d.) of 4.6 mm with an outer diameter of 1/4 in (63.5 mm). However, in recent years there has been a movement to smaller i.d. columns such as 3, 2, 1 and 0.5 mm. There has also been a development of packed capillary columns having i.d. of 0.32, 0.25 and 0.1 mm. Even newer columns with i.d. 0.05 mm have been developed for capillary electrochromatography (CEC). Columns are defined in Table 1 according to their internal diameters.

The most common length of an HPLC column is 25 cm but analytical columns are available in lengths down to 3 cm and guard columns are commonly 1 cm long.

The material packed into columns is mainly silica based, spherical in shape with a particle size of 5 |im. Material of diameter 10 |im has now virtually disappeared from analytical columns and 3 | m material, although introduced in the mid-1980s, is still not widely used. Newer, smaller-diameter particles of

Figure 1 Typical HPLC column.

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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