Quantitation of tricyclic antidepressant drugs based on the formation of mixed aggregates with surfactants

Bio-sample preparation and analytical methods for the determination of tricyclic antidepressants

An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and different analytical methods applied for the quantification of tricyclic antidepressants. These procedures are relevant tools in clinical and forensic toxicology. It is revealed that SPE, for sample preparation, and HPLC, using reversed-phase alkyl (C18) or cyanopropyl-bonded silica columns for the analytes separation, are effective and versatile methods for assay of tricyclic antidepressants. These methods enable achievable detection limits using UV/diode array detection, readily available in most laboratories, down to 1–8 ng ml-1, and using electron capture detection better than 1 ng ml-1, which is lower than that for nitrogen–phosphorus detector. MS interfaced with electrospray ionization offered similar sensitivity, whilst sonic spray ionization provided detection down to 0.03 ng ml-1. A brief discussion on chemical structures, metabolism and mechanism of action of this group of drugs is also presented.

Pharmaceutical quality control of acid and neutral drugs based on competitive self-assembly in amphiphilic systems

An aggregation parameter-based methodology for determining acid and neutral drugs in pharmaceutical dosage forms is presented. The method is based on competitive self-assembly in ternary dye-surfactant-drug aqueous mixtures. Dyes bearing charge of opposite sign to that of surfactants bind to surfactant to form mixed dye-surfactant aggregates, which are monitored from changes in the spectra features of the dye. The drug competes with the dye to interact with the surfactant to form drug-surfactant aggregates, which results in a decrease in the surfactant to dye binding degree proportional to the drug concentration in the aqueous solution. Coomassie Brilliant Blue G (CBBG) and didodecyldimethylammonium bromide (DDABr) were the dye and surfactant reactant used, respectively. The suitability of the surfactant to dye binding degree (SDBD) method to determine drugs with very different molecular structure: propionic (flurbiprofen, ibuprofen, naproxen and ketoprofen) and acetic (diclofenac, felbinac and zomepirac) acids, indolines (indomethacin and sulindac), glycyrrhetinic acid derivatives (carbenoxolone and enoxolone), salicylates (diflunisal and phenyl salicylate), oxicams (meloxicam, piroxicam and tenoxicam), pyrazolones (phenylbutazone and sulfinpyrazone) and hydrocortisones (dexamethasone and prednisolone) has been proved. The proposed method was successfully applied to the determination of drugs in commercial formulates (effervescent granulates, tablets, suppositories, gels and blisters) with a minimum sample treatment (dilution of liquid samples and dissolution of solid samples).

Response surface methodology in the development of a stacking-sensitive capillary electrophoresis method for the analysis of tricyclic antidepressants in human serum

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.

A validated spectrofluorimetric method for determination of some psychoactive drugs

Five psychoactive drugs namely, chlorpromazine HCl, thioridazine HCl, clomipramine HCl, imipramine HCl and desipramine HCl were analyzed by a simple spectrofluorimetric method. The method is based on oxidation of the studied drugs using cerium(IV) in presence of sulphuric acid and monitoring the fluorescence of the formed cerium(III) at lambda(ex.) = 254 nm and lambda(em.) = 355 nm. All variables affecting the reaction conditions such as; cerium(IV) concentration, sulphuric acid concentration, heating time, temperature and dilution solvents were carefully studied. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid and propylene glycol were investigated. A validation study of the proposed method was carried out according to USP 2002. Beer's law was obeyed for all the studied drugs in the concentration range of 0.05-1.3 microg/ml. Limits of detection range was 0.035-0.038 microg/ml and limits of quantitation of 0.116-0.125 microg/ml were obtained. The method was successfully applied for the assay of the studied drugs in pure form and in pharmaceutical dosage forms. Results were compared with official methods. The t- and F-values were calculated and compared with the theoretical values, which indicate high accuracy and good precision of the proposed method.

Determination of aromatic hydrotropic drugs in pharmaceutical preparations by the surfactant-binding degree method

An aggregation parameter-based analytical approach, the surfactant-dye binding degree (SDBD) method, was used, for the first time, to determine aromatic hydrotropic compounds. The anionic dye Coomassie Brilliant Blue G (CBBG) was used as inductor of didodecyldimethylammonium bromide (DDABr) aggregates, whose formation was monitored from changes in the spectral features of the dye. Interactions between hydrotrope and DDABr molecules resulted in a decrease of the degree of binding of the cationic surfactant to CBBG, which was proportional to the concentration of hydrotrope in the aqueous solution. The CBBG-DDABr-hydrotrope chemical system was found to fit to the mathematical expression previously derived for the determination of amphiphilic compounds. The hydrotrope-surfactant bond strength determined the sensitivity achieved for the determination of hydrotropic compounds, which was highly dependent on the molecular structure of the analyte. The high precision (the relative standard deviation for 7 mg l(-1) of salicylic acid was 0.8%), rapidity (measurements were performed in a few minutes) and low cost (in both instrumentation and reactants) of the proposed method, made it especially suitable for quality control. The practical analytical applicability of the SDBD method for the control of hydrotropic drugs in pharmaceutical preparations was demonstrated by quantifying salicylic acid and acetyl salicylic acid in liquid (solutions) and solid (tablets, granulates, unguents, gels and creams) samples, which were directly analyzed after dissolution of the samples.