Quantitation of valproic acid in pharmaceutical preparations using dispersive liquid‐liquid microextraction followed by gas chromatography‐flame ionization detection without prior derivatization

Abstract

Dispersive liquid-liquid microextraction (DLLME), coupled with gas chromatography-flame ionization detection (GC-FID), has been successfully used for the extraction and determination of valproic acid (VPA) in pharmaceutical preparations. In the developed method, an appropriate mixture of extracting and disperser solvents was rapidly injected into an aqueous sample. Having formed a cloudy solution, the mixture was centrifuged and then the extracting solvent was sedimented at the bottom of a conical test tube. The extract was then injected into a GC system directly, without any further pretreatment. Initially, microextraction efficiency factors were optimized and the optimum experimental conditions found were as follows: tetrachloroethylene (9.0 µL) as extracting solvent; acetone (1.0 mL) as disperser solvent; 5 mL acidic aqueous sample (pH 1) without salt addition. Under the selected conditions, the calibration curve showed linearity in the range of 0.1-5.0 mg/L with regression coefficient corresponding to 0.9998. The limit of detection was found to be 0.05 mg/L. Finally, the method was applied for the determination of VPA in two different pharmaceutical preparations. A reasonable intra-assay (3.9-10.8%, n = 3) and inter-assay (5.6-11.4%, n = 3) precision illustrated the good performance of the analytical procedure. The protocol proved to be rapid and cost-effective for screening purposes.

Separation and Preconcentration by Dispersive Liquid–Liquid Microextraction Procedure: Recent Applications

“…Pharmaceutical preparations [27] Separation and Preconcentration by DLLME 653 [68] Separation and Preconcentration by DLLME 655 Tap, lake and river waters [79] Clozapine, chlorpromazine Red wines [104] Separation and Preconcentration by DLLME 657 Table 1 continued Analyte Disperser solvent volume Waters [105] Hexanal and heptanal 50 lL Plants [113] Pesticides and metabolites 418 lL Juice samples [122] technique, an extraction solvent with a low density and low toxicity is employed, which could make the mass transfer as fast as DLLME. Moreover, the melting point (close to or below room temperature) of the extraction solvent makes the floating phase solid, making easier transfer of the floated droplet so that loss of the analytes can be avoided and the precision improved.…”

Determination of free and total valproic acid in human plasma by capillary electrophoresis with contactless conductivity detection

“…A number of chromatographic techniques such as gas chromatography (GC) [19] and liquid chromatography (LC) [20][21][22][23] have also been reported, and have been used in conjunction with various sample pretreatment steps. Commonly used pretreatments are, for instance, liquid-liquid extraction (LLE) [24], solid phase extraction (SPE) [10], solid-phase microextraction (SPME) [25], liquid-phase microextraction (LPME) [12] and dispersive liquid-liquid microextraction (DLLME) [11]. A major drawback of the reported chromatographic approaches is the requirement of prior derivatization of VPA to either render it volatile or suitable for UV-detection.…”

“…For the determination of the total concentration, VPA is usually released from proteins by acidification [10][11][12], which converts it into its protonated form. An alternative method of destroying the protein-binding is precipitation of the serum proteins, e.g.…”

Microextraction of Furosemide from Human Serum and Its Fluorimetric Determination

“…24,25 Dispersive liquid-liquid microextraction (DLLME) method have been used in many biomedical analytical methods and possesses several advantages such as simplicity, low sample volume, low cost and high efficiency. 26,27 Various analytes such as barbituric acid, 28 losartan and carvedilol, 29 cyproheptadine, 30 valproic acid, 31,32 terazosin, 33 carvedilol, 34,35 bosentan, 36…”