[Photometric determination of iron contamination of drugs and biological matrices].
The Ph. Eur. detects colorimetrically the limiting value of iron by formation of a complex with thioglycolic acid in ammoniacal solution. This reaction was rechecked by experiments. Contrary to the literature a solvated Fe(II)-complex will be formed due to the reduction of Fe(III) by the present thioglycolic acid. A supposed oxidation of the Fe(II)-complex by atmospheric oxygen does not occur. For the routine determination of traces of iron in medicinal substances and biological matrixes a VIS-method was developed based on the measurement of the absorption of the complex at 534 nm in the range of 10-100 ppm after graded oxidative decomposition with conc. sulfuric acid/H2O2 30%. This assay needs a calibration mixture or in the case of a higher demand of accuracy a calibration curve with at least five measuring points. Because of the contamination of commercially available reagents a blank value must be determined.
Seeling
A
A
Institut für Pharmazie der Friedrich-Schiller-Universität, Jena, Germany.
Wiecha
P
P
Oelschläger
H
H
D001685:Biological Factors / Q000032:analysis*; D002138:Calibration; D004340:Drug Contamination; D007202:Indicators and Reagents; D007501:Iron / Q000032:analysis*; D010084:Oxidation-Reduction; D004364:Pharmaceutical Preparations / Q000032:analysis*; D010783:Photometry; D011048:Polarography; D012015:Reference Standards; D012996:Solutions; D013464:Sulfuric Acids / Q000737:chemistry; D013864:Thioglycolates / Q000737:chemistry
D001685:Biological Factors; D007202:Indicators and Reagents; D004364:Pharmaceutical Preparations; D012996:Solutions; D013464:Sulfuric Acids; D013864:Thioglycolates; D007501:Iron; C033158:sulfuric acid