Simultaneous determination of salicylic acid and salicylamide in biological fluids

Silica-titania xerogel for solid phase spectrophotometric determination of salicylate and its derivatives in biological liquids and pharmaceuticals

BACKGROUND

Salicylic acid and its derivatives are widely used drugs with potential toxicity. The main areas of salicylate derivatives determination are biological liquids and pharmaceuticals analysis.

RESULTS

Silica-titania xerogel has been used for solid phase spectrophotometric determination of various salicylate derivatives (salicylate, salicylamide, methylsalicylate). The reaction conditions influence on the interaction of salicylate derivatives with silica-titania xerogels has been investigated; the characteristics of titanium(IV)-salicylate derivatives complexes in solid phase have been described. The simple solid phase spectrophotometric procedures are based on the formation of xerogel incorporated titanium(IV) colored complexes with salicylate derivatives. A linear response has been observed in the following concentration ranges 0.1-5, 0.5-10 and 0.05-4.7 mM for salicylate, salicylamide, and methylsalicylate, respectively. The proposed procedures have been applied to the analysis of human urine, synthetic serum, and pharmaceuticals.

CONCLUSIONS

The simple solid phase spectrophotometric procedures of salicylate derivatives determination based on the new sensor materials have been proposed for biological liquids and pharmaceuticals analysis. Graphical abstractComplexation of titanium (IV), incorporated in silica-titania xerogels (Si-Ti), with salicylate derivatives (L) resulting in yellow-colored xerogels (Si-Ti/Ln) has been proposed for salicylate derivatives determination in biological liquids and pharmaceuticals.

Application of time-resolved fluorescence to the determination of metabolites

A simple fluorescent methodology for the simultaneous determination of two major metabolites of acetylsalicylic acid--salicylic and gentisic acids--in pharmaceutical preparations and human urine is proposed. Due to the overlapping between the fluorescence spectra of both analytes, the use of the more selective fluorescence decay curves is proposed. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed with a simplex optimization procedure. A calibration matrix of thirteen standards plus two blank samples was processed using a partial least-squares (PLS) analysis. To assess the goodness of the proposed method, a prediction set of nine synthetic samples was analyzed, obtaining recovery percentages between 95% and 106%. Limits of detection, calculated by means of a new criterion, were 3.49 μg L(-1) and 1.66 μg L(-1) for salicylic and gentisic acids, respectively. The method was also tested in three pharmaceutical preparations containing salicylic acid, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of thirteen standards plus five analyte blanks. Although spectra of analytes and urine overlap strongly, no extraction method neither prior separation of the analytes were needed.

Simultaneous determination of doxycycline and chlortetracycline in real samples by europium-sensitized luminescence

A simple luminescent methodology for the simultaneous determination of doxycycline and chlortetracycline in pharmaceutical preparations and human urine is proposed. Since the native fluorescence of both analytes is negligible, this method takes advantage of the lanthanide-sensitized luminescence, which provides increased sensitivity. Due to the strong overlapping between the luminescence spectra of both europium complexes, the use of luminescence decay curves to resolve mixtures of the analytes is proposed, particularly as these curves are more selective. A factorial design, with three levels per factor, coupled to a central composite design was selected to obtain a calibration matrix of 13 standards plus one blank sample, which were processed with a partial least-squares analysis. In order to assess the effectiveness of the proposed method, a prediction set of 10 synthetic samples was analyzed, and recovery percentages between 95 and 104% were obtained. Limits of detection, calculated by means of a new criterion, were 3.27 and 1.06 μg L(-1) for doxycycline and chlortetracycline, respectively. The method was tested in three different pharmaceutical preparations containing the analytes, with average recovery percentages of 99.4 ± 1.8 for doxycycline and 100.5 ± 2.1 for chlortetracycline. Moreover, a central composite design was also developed to obtain a calibration matrix that made feasible the simultaneous determination of both tetracyclines in human urine samples. In this case, average recovery percentages were 98.0 ± 4.4 and 97.8 ± 4.6 for doxycycline and chlortetracycline, respectively. No extraction method or prior separation of the analytes was needed.