Column Care and Use

Waters Styragel Column, Care and Use Manual, Waters Milford MA 01757, brochure 044491TP, Revision 1, Mareh 1994. 

A sample is removed from the reaction mixture every 15 min, however, in some cases the chromatographic run time may be 20 min. If this is the case, the sample may be held in a syringe until the injection. Alternatively, the run time can be decreased by using a flow rate of 2.0 mU min. This increased flow decreases retention time and should not have a deleterious effect on the resolution. It is cautioned, however, that the backpressure of the column should not be exceeded, as suggested by the column care and use manual of the manufacturer. 

It is especially important to note that Styragel HT columns can be purchased in three different solvents. Conversion procedures for these columns to most of the other commonly used SEC solvents are available in the care and use manual of the Styragel HT column line. Although the same conversion procedures are suitable for other Styragel columns as well, the column stability of... 

Styragel columns can be used with a broad range of solvents and at elevated temperature. They can be converted to different solvents and temperatures following the general guidelines given in this section. Detailed conversion protocols are available in the care and use manual. 

The GPC column must be a good column. Therefore, if there is any question about the condition of the column refer to the Care and Use Manual for testing procedures. 

In this chapter, we will cover the care and use of HPLC columns. Then we will discuss various duomatography problems and ways to find and eliminate the source of these problems, llie topics covered are not necessarily column problems in the strictest sense, but are often viewed as such in the eyes of the user. The troubleshooting section is organized by the observed phenomena,... 

The nitration of the 2-anilino-4-phenylselenazole (103) is much more complicated. Even careful nitration using the nitrate-sulfuric acid method leads to the formation of a mixture of variously nitrated compounds in an almost violent reaction. By the use of column chromatography as well as thin-layer chromatography a separation could be made, and the compounds could be partly identified by an independent synthesis. Scheme 33 shows a general view of the substances prepared. Ring fission was not obser ed under mild conditions. 

Column dimensions mainly determine the quantity of sample to be separated. However, because the SEC process is driven by size separation and is diffusion controlled, special care has to be taken to keep optimized separation conditions, especially when going to smaller internal diameter columns. Overloading and excessive linear flow rates can be observed quite often in these typese of columns. For this reason, standard 8-mm i.d. columns are commonly used, as they are rugged and have a good tolerance toward separation conditions. 

The mobile phase in HPLC is called the eluent and is a liquid or a mixture of liquids. Common eluents are water, aqueous solutions, acetonitrile, and methanol. Almost any other common solvent compatible with the column packing and the detector may be used. In some cases, the HPLC instrument will be capable of making a mixture of eluents or changing the mixture of eluents during chromatography. If this is done, care must be taken to make sure that the eluent mixture is compatible with the detector. 

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