A new approach to ion exchange chromatography with conductivity detection for adulterants investigation in dietary...

The extent of adulteration of dietary supplements has significantly increased in recent years. This situation worries health authorities and requires auxiliary analytical tools for the investigation of illegal substances purposely added. Ion exchange chromatography with conductivity detection is a consolidated analytical technique for the determination of inorganic compounds in various matrices. This technique has been applied to the pharmaceutical characterization of mainly impurities and degradation products. This work presents a new approach to ion exchange chromatography as a screening method to investigate the presence of amfepramone, femproporex, sibutramine, bisacodyl and amiloride in dietary supplements advertised for weight loss. The method was optimized and validated using a Metrosep C4 100/4.0 cation exchange column. The mobile phase consisted of 1.8 mm HNO₃ containing 2% acetonitrile (v/v), with a flow rate of 0.9 ml min^-1 , and nonsuppressed conductivity detection was applied. The limits of detection and quantification varied from 1.01 to 3.62 mg L^-1 and from 1.48 to 8.72 mg L^-1 , respectively. The proposed method was successful applied to 78 solid dietary supplement samples, in two of which adulterations were found. Moreover, ion exchange chromatography with conductivity detection could be easily used for quality control without prior complex sample pre-treatment.