The Malaysian Journal of Analytical Sciences Vol 12 No 1 (2008): 39 – 45

 

 

HARNESSING ELECTRO DRIVEN SEPARATION TECHNIQUE FOR THE SEPARATION OF SELECTED AGROCHEMICALS

 

Wan Aini Wan Ibrahim¹, S. M. Monjurul Alam²  and Azli Sulaiman¹

 

¹Separation Science Research Group (SSRG)Chemistry Department, Faculty of Science,

University Teknologi Malaysia, 81310 Skudai, Johor

²Chemistry Department, Rajshahi University, Rajshahi-6205, Bangladesh

 

Abstract

Electro driven separation techniques offer a different approach to the analysis of complex mixtures than  do  traditional pressure-driven chromatographic system; it may rely on electrophoresis, the transport of charged species through a medium by an applied field or may rely on electro driven mobile phase to provide a true chromatographic separation.  In the current work  the  potential  of  an  electro  driven  separation  technique  viz.  micellar  electrokinetic  chromatography  (MEKC),  is harnessed for the separation of selected agrochemicals (organophosphorus pesticides, OPPs) widely used in the agriculture sector in Malaysia.  The current study compares the use of MEKC in normal mode (NM) and reverse mode (RM) for the separation of the selected OPPS.  This study also highlights the difference in separations produced by performing separations in  normal  mode-MEKC  (NM-MEKC)  and  reverse  mode-MEKC  (RM-MEKC)  for  the  selected  OPPs.  In  RM-MEKC, separation is conducted at acidic pH (pH 2.5 in the current work) where the electroosmotic flow (EOF) is weak whereas in NM-MEKC, the separation is carried out under basic pH (9.3 in this work) where the EOF is strong.  A reverse migration order of the OPPs was observed under RM-MEKC.  Separation under NM-MEKC was found to be superior to those of RM- MEKC.  A comparison is also made between separations performed under sweeping-NM-MEKC and sweeping-RM-MEKC. In sweeping, the OPPs are prepared in the same background solution (BGS) minus the micelles and is adjusted to the same conductivity as the BGS.  The study showed that NM-MEKC is more sensitive than RM-MEKC but sweeping-RM-MEKC is superior to sweeping-NM-MEKC.  However, sweeping-RM-MEKC only separates two of the OPPs in a single run whereas sweeping-NM-MEKC separates four OPPs in a single run.  The better choice of separation mode would be sweeping-NM- MEKC for more OPPs separation in a single run.

 

Keywords:  Micellar electrokinetic chromatography (MEKC), organophosphorus pesticides, normal mode MEKC,

reverse mode MEKC, sweeping

 

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