Determination of Diethylcarbamazine DEC Using Gas Chromatography with Flame Ionization Detection GC-FID

Determination of Diethylcarbamazine (DEC) Using Gas Chromatography with Flame Ionization Detection (GC-FID) 

All solvents and chemicals were HPLC grade. Organic solvents, sodium carbonate (anhydrous), and sodium bicarbonate were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Carbonate buffer, pH = 10.0, was prepared using the sodium carbonate (anhydrous), and sodium bicarbonate. A solution of 0.1 % triethylamine in methanol was made for the elution solvent. Diethylcarbamazine citrate was obtained from Sigma, and used to make stock solutions (St. Louis, MO, USA). The internal standard, 1-diethylcarbamyl-4-ethylpiperazine (E-DEC) was synthesized by the Division of Medicinal and Natural Products Chemistry at the University of Iowa, College of Pharmacy. Ultra-pure analytical grade Type I water was produced by a Milli-Q Plus water system (Millipore Corporation, Bedford, MA, USA). For the extraction of DEC and of its internal standard, Alltech Extract - Clean C18 cartridges, 500 mg with a 2.8 mL reservoir, and a SPE vacuum manifold (Alltech, Deerfield, IL, USA) were used. 

4It responds to any molecule with a carbon-hydrogen bond, but not at all or poorly to compounds such as H2S, CCI4, or NH3. 

DEC and the internal standard (Istd), 1-diethylcar-bamyl-4-ethyl piperazine HC1 (E-DEC), were extracted from human plasma - that has been alkalised with carbonate buffer - after loading onto a conditioned Cl8 solid phase extraction cartridge, rinsed with water and eluted with methanol. After evaporation under a stream of nitrogen and reconstitution in methanol, 3 il. were injected into the GC system and detected using a flame ionization detector (FID). The retention time for DEC was 5.5 min and for the internal standard (E-DEC) it was 7.28 min. 

5 mL human plasma in a disposable centrifuge tube, 25 il. of the working solution of the internal standard (21 ig E-DEC/mL) and 1 mL of carbonate buffer pH = 10.0 are added and the sample is mixed on a vortex mixer for 30 sec. 

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