Using Micro-Extraction on a Screw for Determination of Trace Amounts of Cationic Dyes by HPLC-UV/Vis

Nowadays, among all pollutants, cationic dyes are one of the biggest concerns incontemporary society. These dyes pose a serious threat to human health and the environment dueto their toxic, non-biodegradable, and even carcinogenic effects. Therefore, it is important todevelop sensitive techniques for determining these colors in real samples [۱].In general, sample preparation is an important step in separation techniques and accuratedetermination of the desired analyte from complex matrices [۲]. Among the sample preparationmethods, solid phase micro-extraction (SPME) is more popular. SPME is found useful for microextractiondue to its small geometry and simple operating procedures, simplicity, rapidity, accurateanalysis and low consumption of organic solvent [۳].In the present work, solid phase micro-extraction on a screw (MES) which is a miniaturized formof in-tube SPME without back pressure, was developed to extract cationic dyes (malachite green,methylene blue and rhodamine B) in water samples. The screw was coated with a functionalizedco-polymer as an absorbent. The extracted dyes on the screw was eluted by a suitable eluent.Separation and determination of the dyes was performed by high performance liquidchromatography equipped with a UV detection (HPLC-UV). Hence, MES is prepared byelectrophoretic coating sulfonated poly (styrene-co-divinylebenzene) on surface of a screw. Thenit was placed inside a silicon tube to create a channel to pass sample solution through it. Effectiveparameters on extraction efficiency of analytes were studied and optimized. Under optimumconditions, the limit of detection was ۰.۱۵ μg L-۱ and calibration curve was liner in the range of۰.۵-۲۵۰ μg L-۱ with a correlation coefficient greater than ۰.۹۸ for all studied cationic dyes. Theinter-day and intra-day precision (n=۵) were ۲.۸-۷% and ۷-۹.۵%, respectively. The proposedmethod is evaluated as a simple and repeatable method with acceptable relative recoveries (۸۲-۱۰۳%) for determination of cationic dyes in real water samples.