Basically the technique of chromatography splits compunds into their chemical groups and this is made possible by using a number of different related instruments. One such method, High Performance Liquid Chromotography (HPLC) uses an autosampler as one of many tools to achieve its goals. So, let’s take a look at thow these two products work together.
Column chromatography is a method of separating compounds which drives a solvent through a column having a small sample of the compound within. Based on how the solvent interacts with different parts of the compound substance, this will cause some of it to be separated from the original mix while some will stay. This is basically how HPLC is developed.
High Performance Liquid Chromatography doesn’t simply allow the solvent to drip through the column as happens with column chromatography. Rather, the solvent is forced through at much greater pressures. The advantages are two-fold.
First, because the pressures are much greater, often as high as 400 atmospheres, the process is much quicker. Were the solvent simply dripping through under the pressure of gravity, separating the compound into its component elements would be a much longer process.
Also, materials on a smaller scale can be used as the packing surface within the column. The result is a much more accurate separation of the desired components that would be possible via traditional column techniques.
These advantages come at a cost, however. Generating the extreme pressures to which the solvent is subjected cannot be done without the help of external machinery. It is also worth mentioning that finer separation of components needs more advanced levels of automated detection. This is where an autosampler comes in. mainly autosamplers used for HPLC carry out these functions.
First of all the sample is injected into the main column. It is at this stage that high pressures are produced to push the compound through the column at extremely high speeds.
eventually reach the detector}. Given the known quantities of the pressure, solvent and column dimensions, determining when a given compound has been separated is a fairly straight-forward matter of measuring the time that individual chemicals take to traverse the column the separation is quite simple by measuring the time it eakes for individual chemicals to extend the column~If we know the dimensions of the column and solvent, as well as the main pressure we can determine the time taken for the separation of the compound and the time it takes the substance to pass through the column}.
This value, known as the retention time, is one of several factors used by the detector in determining when a given chemical has been removed. As temperature can certainly effect the rate of flow through the column, there is a need for {control using retention time as a method of detection}. This is yet another of the many factors maintained by an HPLC autosampler.
Once the compound traverses the column, it arrives at one or more detectors, each using different methods to quickly and accurately detect the presence of desired substances. A very common method is the use of ultraviolet detector products and UV light. By shining UV light through the stream and detecting which wavelengths are absorbed, an accurate identification
of some chemical compounds can be obtained.
The result of ultra violet spectroscopy, tetention timings and other detection is then translated by computers to form an identity of the components chemical properties.
The high pressures and extreme speed of HPLC make it practically impossible to perform manually. As such, an autosampler is an invaluable tool when using this method of chromatography.
Tags: autosampler, hplc, hplc analysis, hplc chromatography