Capillary electrophoresis with post‐column addition of terbium and sensitized lanthanide‐ion luminescence detection for the determination of diflunisal and salicylic acid

Abstract

SummaryA detection scheme based on the post-column addition of terbium followed by sensitized luminescence detection has been developed.Two model compounds -salicylic acid and diflunisal -were separated by capillary electrophoresis in an alkaline phosphate buffer. A solution containing terbium and CTAB was added post-column via a "home-built" reactor resulting in the rapid formation of the strongly luminescent terbium-salicylic acid and terbium-diflunisal complexes in a reaction capillary. Following complexation in the reaction capillary, the 325 nm line from a HeCd laser was used to excite the analytes which efficiently transfer their energy to terbium. Resultant luminescence of terbium was linear of 2 orders of magnitude. This novel and practical system enables the detection of micromolar concentrations of diflunisal and salicylic acid -a 10-fold improvement over UV absorbance detection in the same system. Post-column addition of terbium also eliminates the problems associated with strong adsorption of the lanthanide ion to the silica walls of the separation capillary and the formation of metal-ligand complexes with different coordination numbers.

Voltammetric quantification of a nonsteroidal anti-inflammatory agent diflunisal based on the enhancement effect of cationic surfactant on boron-doped diamond electrode

“…To date, various analytical methodologies were developed for the determination of DIF alone or in combination with other drugs in pharmaceutical formulations, biological fluids, and wastewater. The majority of these analyses are based on spectrophotometry [5], spectrofluorimetry [6,7], liquid chromatography (LC) [8][9][10][11][12], and capillary electrophoresis [13,14] methods. Although some of these methods offer good selectivity and sensitivity, they involve disadvantages such as expensive instrumentation, excessive chemical consumption, and intense pretreatment procedures.…”

Improved detection of salicylic acids using terbium-sensitized luminescence in aqueous micellar solutions of cetyltrimethylammonium chloride

“…In the absence of surfactant, complexation is very weak even in alkaline solutions. Owing to the pK value of the phenol group (12)(13), the optimum pH for complex formation seems to be related to the dissociation of the phenol group which is adjacent to the carboxylic group. This result corroborates that complexation involves two negatively charged oxygens available in a single ligand to form a chelate.…”

“…9 The same method has been proposed to determine salicylic acid and its derivatives either without a separation step 10,11 or after separation using capillary electrophoresis. 12,13 p-Aminosalicylic acid (p-ASA) has been used as a sensitizing reagent in the determination of bovine serum albumin. 14,15 5-Fluorosalicylic acid (FSA) has been found to form highly fluorescent chelates with terbium for application as labels in time-resolved fluorimetric immunoassays.…”

Validated Stability-Indicating HPLC-DAD Method for the Simultaneous Determination of Diclofenac Sodium and Diflunisal in Their Combined Dosage Form

“…These methods expose the application of an ion-selective electrode [21], differential-pulse polarography [22], differential-pulse and square-wave stripping voltammetry [22, 23], derivative spectrophotometry [24], chemometric spectrophotometry [25], and synchronous fluorescence spectrometry [26, 27]. Also, the scientific literature showed the use of separation techniques such as HPLC-UV detection [25], HPLC-fluorescence detection [28], TLC-densitometry [29], and capillary electrophoresis with luminescence detection [30]. Finally, the determination of several NSAIDs including DIC and DIF in water samples was carried out using liquid chromatography coupled with diode array detection (LC-DAD) [31] and LC-DAD-MS [32].…”