A new simple accurate turbidimetric method for determination of ascorbic acid in pharmaceuticals and fruits

摘要

An accurate,simple,solvent free and inexpensive turbidimetric method ispresented for the determination of ascorbic acid in pharmaceutical preparations and fruits.It needs nospecial reagents or precautions.In this method HgCl_2 oxidizes ascorbic acid in citrate buffer at a pH of about 4 and produced Hg_2Cl_2 precipitate as monitored by turidance measurements.The procedure is very simple and the experimental conditions such as temperature,ionic strength,stirring and time are not critical.High sensitivity and selectivity are two other advantages of this method.Linear dynamic rane of the calibration curve is between 3-120 mug/mL with limit to detection (LOD) l mug/mL.Linear dynamic range of the calibration curve is between 3-120 mug/mL with limit of detection(LOD) l mug/mL,which allows the ascorbic acid contents of most fruits and vegetables to be analyzed.On the other hand,the interference studies show that common compounds in real samples and colored substances have no considerable effect on the determination.Only filtration of some samples is necessary and other treatments,which are performed piror to determination of ascorbic acid by other analytical methods,are eliminated.Finally,ascorbic acid concentration in different samples is determined by the proposed method and obatined results are compared with the results of the official 2,6-dichlorophenolindophenol or iodimetric methods and a good agreement is obtained.This method is very sensitive in comparison with iodimetry and is very fast relative to the 2,6-dichlorophenolindophenol method.