Related Drugs

The main problem posed in the separation of antibiotics is their broad range of structures that covers almost the whole range of organic chemistry. This includes carbohydrate, macrocyclic lactones, quinones, peptides and heterocyclic compounds, although antibiotics in general are relatively polar, nonvolatile and thermally labile drugs. For that reason, liquid chromatography has increasingly been chosen as the method of analysis, and SFC is gaining greater acceptance with the extended use of packed columns combined with organic modifiers and additives that allow the separation of the more polar solutes.

GC commonly provides the highest resolution in the shortest analysis time, but it also requires high temperatures and often derivatization of the drugs. HPLC methods have lower resolution and longer analysis times. The SFC technique can provide the same resolution as GC and short run times, but with the added benefit that it does not need high temperatures (Figure 1). Typical temperatures are as low as 50-80°C in packed-column SFC.

The packed columns used for SFC of polar drugs are similar to the columns used in HPLC, although back-pressure is not a problem in SFC, allowing columns to be coupled in series to achieve high resolution systems, even for polar analytes. When it comes to detection, the commonest systems for antibiotics determination are UV (Figure 2). or mass spectrometry (MS). In comparing packed-column SFC and LC, the ultraviolet detector can be operated at lower wavelengths in SFC, because of the lack of background absorbance from the solvent and the mass spectrometric ionization techniques work best with volatile mobile phases also favouring SFC (Table 1).

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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