Monitoring of Gold Biodistribution from Nanoparticles Using a HPLC-Visible Method

There is intensive research using gold nanoparticles for biomedical purposes, which have many advantages such as ease of synthesis and high reactivity. Their possible small size (<10 nm) can lead to the crossing of biological membranes and then to problematic dissemination and storage in organs that must be controlled and evaluated. In this work, a simple isocratic HPLC method was developed and validated to quantify the gold coming from nanoparticles in different biological samples. After a first carbonization step at 900 °C, the nanoparticles were oxidized by dibroma under acidic conditions, leading to tetrachloroaurate ions that could form ion pairs when adding rhodamine B. Finally, ion pairs were extracted and rhodamine B was evaluated to quantify the corresponding gold concentration by reversed-phase HPLC with visible detection. The method was validated for different organs (liver, spleen, lungs, kidneys, or brain) and fluids (plasma and urine) from rats and mice. Lastly, the developed method was used to evaluate the content of gold in organs and fluids after intravenous (IV) injection of nanoparticles.

HPLC DETERMINATION OF SILDENAFIL IN TABLETS

Objective: The popularity of Sildenafil, the widespread distribution of various products and dietary supplements with added synthetic drugs, requires reliable analysis methods. This research study aimed to develop a simple isocratic HPLC method for the determination of Sildenafil in tablet dosage forms from the local market. Methods: Separation was carried out at 30 °C, using column LiChrosorb® RP-18 (150 x 4.0 mm, 5 μm) with mobile phase consisting of acetonitrile: methanol: 0.5% triethylamine (15: 26: 59 v/v/v). The detector was set at 290 nm. The flow rate was 1.0 ml/min and the injection volume was 20 μl. Results: Linear correlation was obtained within the range 6.25–50.0 μg/ml with correlation coefficient (R2) 0.9998. The achieved limits of detection and quantitation were 0.7 and 2.2 μg/ml, respectively. Conclusion: The developed method can be applied for the quality control of Sildenafil preparations.

Development and Validation of a Simple HPLC-UV Method to Assay DEET Repellents and its Application to Different Commercial Forms

Background: N’,N’-diethyl-m-toluamide (DEET) is the most widely used repellent substance worldwide. It is formulated as aerosol, solution, lotion, gel and patches. However, the official compendia report monographs to analyze only DEET drug substance and solution. Objective: In this study an isocratic HPLC method was validated to assay DEET in lotion, gel and solution, under the same analytical conditions. Method: The method was validated according to ICH requirements and DEET detection was achieved at around 11 min, using C-18 column, a mobile phase composed by methanol, acetonitrile and water pH 4.5 (45:10:45), flow rate at 1 mL min-1 and detection at 270 nm. Results: A linear relationship was observed in the range of 2.5 to 100 µg mL-1, the method was precise (relative standard deviation < 2%) and accuracy was demonstrated by DEET recovery values ranging from 99.5 to 100.2%. The specificity was studied by a forced degradation test, where degradation products were observed after alkaline degradation and ultraviolet radiation. Appropriate resolution between DEET, degradation products and excipient peaks indicated the method specificity. Robustness was evaluated by a full factorial design, and no effect on DEET assay was observed under simultaneous variation in analytical parameters. The method was applied to assay nine marketed formulations, demonstrating its good applicability. Conclusion: The validated HPLC method was successfully applied to the quantitative analysis of DEET in lotion, gel and solution, contributing to improve the quality control and the efficacy of these formulations.

An HPLC tool for process monitoring: rare sugar D- psicose and D- fructose contents during the production through an enzymatic path

D-Psicose/allulose, a rare sugar, is an essential raw material in the pharmaceutical and food industries. It is scantly found in nature and to meet its demand in industries, D-Psicose is generated enzymatically using D-fructose as a substrate. In these conversations, it is important to monitor D-Psicose, in order to control the process, impurities, optimize the reaction time and reduce the process cost The available analytical methods have their limitations in quantifying D-psicose and D-fructose mixtures. Hence there is a need for the development of a routine, sensitive, quick and precise analytical method for D-psicose production on-line monitoring of reaction mixer. In the present work, a simplified reverse phase HPLC technique is developed and validated for the quick reaction monitoring of D-psicose from D-fructose, during enzymatic conversation procedures. The analysis is conducted at different concentrations ranging from 0.05 % to 0.5 % of the standard solutions of the D-psicose and D-fructose, by using water and Acetonitrile (at a ratio of 20:80) as eluent with a flow rate of 1.0 mL/min on isocratic HPLC-RID system with an aminopropyl silane stationary phase [ZORBAX SIL 4.6 x 150 mm, 5 µm particle size column (USP-L8)]. The applicability of this method is illustrated in reaction monitoring, where D-fructose (substrate) is converted to D-psicose (product) in the presence of the enzyme: D-Tagotose 3- epimerase. Separation of D-psicose and D-fructose is achieved within 8 minutes with a resolution ≥ 4 which is the key advantage for reaction monitoring and linearity is established with regression of ≥ 0.99. Additionally, the current method uses a simple mobile phase, without any buffers. It can be used routinely for reaction monitoring.