Determination of Ferrous Iron in Ferric Chloride Hexahydrate

Bai Xiaoguang,Liu Aihua,Wu Xudong,Cheng Xiao,Wang Zhengda,Duan Shufen

doi:10.11648/j.ijpc.20210701.11

Abstract

Objective: As a pharmaceutical raw material, ferric chloride hexahydrate has been included in the British Pharmacopoeia, the European Pharmacopoeia (2008) and the United States Pharmacopoeia (2015), and there are detailed discussions on quality standards and testing methods. Ferric chloride hexahydrate has not been included in the Chinese Pharmacopoeia. This study is the part of research to establish a spectrophotometric method for the determination of ferrous iron in ferric chloride hexahydrate. In this study, the two methods were discussed in detail, and the spectrophotometric method for detecting the content of ferrous iron in ferric chloride hexahydrate was proposed. Methods: The detection method on ferrous iron in ferric chloride hexahydrate among European pharmacopoeia, United States pharmacopoeia and Chemical Reagent Ferric Chloride Hexahydrate (HG/T3474-2014) of China's Chemical Industry were compared. The last two methods were not easy to operation. On the basis of the European pharmacopoeia, a method was proposed that after Fe<sup>3+</sup> were screened with H3PO4, Fe2+ was measured by spectrophotometry, and the method was verified by experiments. Results and Conclusion: The spectrophotometry method is easy to operate and has good reproducibility. The content of ferrous iron can be calculated semi-quantitatively by masking ferric iron with H3PO4 and spectrophotometric determination of ferrous ion content. Therefore, the method established in this study can more clearly detect whether the ferrous content in ferric chloride hexahydrate is up to standard.

Highlights

Pharmacopoeia, the European Pharmacopoeia (2008) and the United States Pharmacopoeia (2015), and there are detailed discussions on quality standards and testing methods
When the content of Fe2+ in the sample is under very strict requirement, such as Fe2+ not more than 50×10-6, or even no more than 20×10-6, it should be considered that ferric chloride hexahydrate is not very stable
When the aqueous solution is directly heated on an electric furnace, and even the hot solution is filtered by a filter paper filter cloth or a PP microporous membrane, it can generate Fe2+ [14,15]

Summary

Reagents

Potassium ferricyanide (Shanghai Qianshun Chemical Reagent Co., Ltd., batch number 1401107), 5% potassium ferricyanide solution prepared on the test day; phosphoric acid (Shanghai Lingfeng Chemical Reagent Co., Ltd., batch number 20151009); sulfuric acid heptahydrate Yatie (Shenzhen Pharmaceutical Group Chemical Reagent Co., Ltd., batch number 10012118) Fe2+ concentration of 0.1mg/mL stock solution (weigh 0.250g FeSO4·7H2O, add H2SO4 5mL dissolved and diluted into 500mL volumetric flask); Fe2+ concentration of 0.01mg/mL solution (take 10m Fe2+ concentration 0.1mg /mL stock solution, diluted to 100mL volumetric flask, ready for use) Ferric chloride solution of hexahydrate (FeCl3·6H2O, Sinopharm Chemical Reagent Co., Ltd., batch number 10011918); hydrochloric acid, Sinopharm Chemical Reagent Co., Ltd., batch number 10011018)

Principle of the Method

ACS Detection Method Method

Experimental Verification

Findings

Discussion