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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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14.21.1 Use <strong>of</strong> solvents in manufacture <strong>of</strong> drugs 995<br />

Table 14.21.1.12. Specification for isopropanol<br />

particular case. It is preferable to focus on the impact <strong>of</strong> impurities present in the solvent on<br />

the chromatographic performances.<br />

Impurities in and additives to solvents can cause several problems and artifacts in liquid<br />

and gas chromatography. 37-39 Primarily they can be the origin <strong>of</strong> irreproducible separations,<br />

enhanced UV-background and even <strong>of</strong> mechanical problems. De Schutter and Col 37<br />

have investigated this problem in purity <strong>of</strong> solvents used in high-performance thin-layer<br />

chromatography.<br />

A way to improve the stability <strong>of</strong> the chromatographic system by minimizing the role<br />

<strong>of</strong> solvent impurities is to add deliberately a controlled amount <strong>of</strong> organic modifier. For example,<br />

Lauren and Col 40 have applied this technique, using decanol for improving the stability<br />

<strong>of</strong> the LC used for analyzing carotenoids. Middleditch and Zlatkis 41 have listed an<br />

impressive range <strong>of</strong> stabilizers and additives which can be found in solvents which may<br />

help the chromatographer in explaining the occurrence <strong>of</strong> artifacts in chromatography.<br />

Zelvensky and Col 38 have determined by gas chromatography the most common impurities<br />

contained in solvents for liquid chromatography. The series <strong>of</strong> solvents investigated include<br />

acetonitrile, methanol, ethanol, dichloromethane, formic acid, dimethylformamide,

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