A new platform was developed for determination of drugs in plasma without extraction or instrumental analysis just using TLC, smart phone digital camera and free image processing software. Lamotrigine, antiepileptic drug was used as model analyte. The proposed platform depends on using oil-in-water (O/W) microemulsion to isolate the drug from plasma proteins and using water-in-oil (W/O) microemulsion as mobile phase for TLC which results in complete separation between lamotrigine and plasma as viewed under UV lamp. The composition of both microemulsions was optimized using Taguchi orthogonal array and Plackett- Burman design. The optimal (O/W) microemulsion predicted composition was 0.01 mL Butyl acetate, 4 mL butanol, 0.925 gm SDS and 8.6 mL water while the (W/O) mobile phase microemulsion was 9 mL Butyl acetate, 1 mL butanol, 0.25 gm SDS, 0.25 mL water. Separation was carried out on a silica gel 60F-254 plate eluted with the (W/O) microemulsion in about 30 min development time. The images of TLC plates were processed using 4 different programs, by comparing their results it was found that "integrated density" measured by Fiji software was the most accurate response that could measure the concentration of lamotrigine in spiked plasma in the range of (20-200) ng/spot. This method was applied also for determination of lamotrigine in lamictal® tablet dosage form using the same mobile phase. The precision of the method was satisfactory; the maximum value of relative standard deviations did not exceed 1.5%. While the accuracy was proved by the low values of % error and high values of recovery.
Keywords: Image processing; Lamotrigine; Microemulsion TLC; Plackett- Burman design; Plasma; Taguchi orthogonal array design.
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