Salicylic acid determination in cow urine and drugs using a bienzymatic sensor

Determination of acetylsalicylic acid and its major metabolites in bovine urine using ultra performance liquid chromatography

A new method based on ultra high performance liquid chromatography (UPLC) with photometric and fluorometric detection for the determination of acetylsalicylic acid and its main metabolites, namely gentisic, salicylic and salicyluric acids, in bovine urine samples is reported. Photometric detection was used for acetylsalicylic acid determination, whereas the native fluorescence of the metabolites was monitored using fluorometric detection. The separation was performed under isocratic conditions, using acetonitrile-phosphate solution (3.5mM, pH 3.5) (26:74, v/v) as the mobile phase. The retention times of the four compounds were lower than 2min, which are shorter than those achieved using conventional HPLC. Under the optimum separation conditions, the dynamic ranges and detection limits (ngmL(-1)) were: 0.2-2500, 0.09 for gentisic acid; 0.2-2500, 0.08 for salicylic acid and 2.5-15,000, 1.1 for salicyluric acid, using fluorescence detection, and 10-25,000, 2.2 for acetylsalicylic acid, using UV detection. Intra-day and inter-day precision data were assessed at two levels of concentration of each analyte using both detection systems. The selectivity of the method was checked by assaying different drugs of veterinary use showing that most of them did not interfere with the determination of the analytes. The method has been applied to the analysis of bovine urine samples, which only required a simple clean up step of the samples prior to injection in the UPLC system. A recovery study was performed, which provided values in the range of 80-100%. This fact proves the practical usefulness of this method as an ultrafast analytical tool for the therapeutic control of acetylsalicylic acid administration in bovine animals intended for food production.

Electrochemical biosensors in pharmaceutical analysis

Given the increasing demand for practical and low-cost analytical techniques, biosensors have attracted attention for use in the quality analysis of drugs, medicines, and other analytes of interest in the pharmaceutical area. Biosensors allow quantification not only of the active component in pharmaceutical formulations, but also the analysis of degradation products and metabolites in biological fluids. Thus, this article presents a brief review of biosensor use in pharmaceutical analysis, focusing on enzymatic electrochemical sensors.

Electrocatalytic activity of salicylic acid on the platinum nanoparticles modified electrode by electrochemical deposition

Platinum nanoparticles (PNP) were deposited on the Pt disk electrode by electrochemical deposition, it was found that salicylic acid (SA) had good electrocatalytic oxidation response at the prepared Pt nanoparticles modified Pt disk electrode (PNP/Pt). Then the modified electrode was used to detect SA in weak alkali condition, it was found that the response current was 9.2 times that of bare Pt disk electrode, and the linear range of detection was 2.0x10(-5) to 5.0x10(-4)M. After that, the electrode was adopted to detect the SA in Zuguangsan, one kind of Chinese medicine, the results showed that the PNP/Pt electrode has low detection limit, high repeatability and stability as SA sensor, could be applied in the detection of SA reliably.

Application of a lanthanide composite nanoparticle-sensitized luminescence method for the determination of salicylic acid in pharmaceutical formulations and human plasma

Terbium-acetylacetone (Tb-acac) composite nanoparticles were synthesized using the ultrasonic method. The nanoparticles are water-soluble, stable and have extremely narrow emission bands and high internal quantum efficiencies. They were used as fluorimetric probes in the determination of salicylic acid (SA), based on the fluorescence enhancement of nanoparticles through fluorescence resonance energy transfer (FRET). The influence of buffer solution was investigated. Under the optimum conditions, a linear calibration graph was obtained over the SA concentration range 5 x 10(-7)-1 x 10(-4) mol/L. The limit of detection was found to be 2.5 x 10(-8) mol/L. The relative standard deviation (RSD) for six repeated measurements of 1 x 10(-4) mol/LSA was 1.75%. The method was applied to the determination of SA in pharmaceutical formulations and human plasma. We believe that the proposed approach has great potential for clinical purposes.

A Systematic and Comprehensive Combinatorial Approach to Simultaneously Improve the Activity, Reaction Specificity, and Thermal Stability of p-Hydroxybenzoate Hydroxylase

We have simultaneously improved the activity, reaction specificity, and thermal stability of p-hydroxybenzoate hydroxylase by means of systematic and comprehensive combinatorial mutagenesis starting from available single mutations. Introduction of random mutations at the positions of four cysteine and eight methionine residues provided 216 single mutants as stably expressed forms in Escherichia coli host cells. Four characteristics, hydroxylase activity toward p-hydroxybenzoate (main activity), protocatechuate-dependent NADPH oxidase activity (sub-activity), ratio of sub-activity to main activity (reaction specificity), and thermal stability, of the purified mutants were determined. To improve the above characteristics for diagnostic use of the enzyme, 11 single mutations (C152V, C211I, C332A, M52V, M52Q, M110L, M110I, M213G, M213L, M276Q, and M349A) were selected for further combinatorial mutagenesis. All possible combinations of the mutations provided 18 variants with double mutations and further combinatorial mutagenesis provided 6 variants with triple mutations and 9 variants with quadruple mutations with the simultaneously improved four properties.