Istodobno spektrofotometrijsko određivanje losartan kalija, amlodipin besilata i hidroklorotiazida u farmaceutskim pripravcima kemometrijskom metodom

In the present work, four different spectrophotometric methods for simultaneous estimation of losartan potassium, amlodipine besilate and hydrochlorothiazide in raw materials and in formulations are described. Overlapped data was quantitatively resolved by using chemometric methods, classical least squares (CLS), multiple linear regression (MLR), principal component regression (PCR) and partial least squares (PLS). Calibrations were constructed using the absorption data matrix corresponding to the concentration data matrix, with measurements in the range of 230.5350.4 nm (∆λ = 0.1 nm) in their zero order spectra. The linearity range was found to be 840, 15 and 315 μg ml1 for losartan potassium, amlodipine besilate and hydrochlorothiazide, respectively. The validity of the proposed methods was successfully assessed for analyses of drugs in the various prepared physical mixtures and in tablet formulations.U radu su opisane četiri spektrofotometrijske metode za istodobno određivanje losartan kalija, amlodipin besilata i hidroklorotiazida u sirovinama i farmaceutskim pripravcima. Podaci koji su se preklapali kvantitativno su razlučeni kemometrijskim metodama, klasičnom metodom najmanjih kvadrata (CLS), multiplom linearnom regresijom (MLR), regresijom glavnih komponenata (PCR) te metodom parcijalnih najmanjih kvadrata (PLS). Kalibracije su provedene koristeći podatke o ovisnosti apsorpcije o koncentracijama, mjereći spektre nultog reda u rasponu 230,5350,4 nm (∆λ = 0,1 nm). Linearnost za losartan kalij bila je 840, za amlodipin besilat 15, a za hidroklorotiazid 315 μg ml1. Valjanost predloženih metoda uspješno je potvrđena analizom navedenih lijekova u različitim pripremljenim smjesama i tabletama

Aptamer-based field-effect biosensor for tenofovir detection

During medical treatment it is critical to maintain the circulatory concentration of drugs within their therapeutic range. A novel biosensor is presented in this work to address the lack of a reliable point-of-care drug monitoring system in the market. The biosensor incorporates high selectivity and sensitivity by integrating aptamers as the recognition element and field-effect transistors as the signal transducer. The drug tenofovir was used as a model small molecule. The biointerface of the sensor is a binary self-assembled monolayer of specific thiolated aptamer and 6-mercapto-1-hexanol (MCH), whose ratio was optimized by electrochemical impedance spectroscopy measurements to enhance the sensitivity towards the specific target. Surface plasmon resonance, performed under different buffer conditions, shows optimum specific and little non-specific binding in phosphate buffered saline. The dose-response behavior of the field-effect biosensor presents a linear range between 1 nM and 100 nM of tenofovir and a limit of detection of 1.2 nM. Two non-specific drugs and one non-specific aptamer, tested as stringent control candidates, caused negligible responses. The applications were successfully extended to the detection of the drug in human serum. As demonstrated by impedance measurements, the aptamer-based sensors can be used for real-time drug monitoring

Chocolate Quality and Conching

Background: Conching is the processing step in which chocolate is subjected to long-term heat treatment, me- chanical forces and addition of fat and emulsifiers. There is an important relationship between the chocolate flavour and the type of conching process. However, it is a costly processing step due to long duration of high temperature application. Scope and approach: In order to increase the level of chocolate quality and microbiological safety, the raw materials used as well as the process methods and parameters are of importance. In particular, the knowledge of how conching process affects the main quality parameters of chocolate can lead to better quality product in a more cost-effective way. Therefore, the objective of this study is to provide a general overview on the relation between the type of conching processes and chocolate main quality parameters (safety, aroma, color, texture and flow behavior), and also on the innovative conching applications. Key findings and conclusions. With the conching process, significant changes occur in physical, physico- chemical and sensory properties of chocolate. Therefore, in addition to tempering and refining steps, conching process should also be considered to produce high quality products at a more cost-effective way. As a result of innovative modifications to be made in the conching process, it is possible to obtain a safe product with higher consumer acceptability. However, these targets should be reached with shorter conching application time to increase production efficiency

Incorporation of Defatted Apple Seeds in Chewing Gum System and Phloridzin Dissolution Kinetics

Apple seeds are among the major natural sources of antioxidants and can be used in various industries. In this regard, antioxidant activity, total phenolic content, and individual phenolic compounds analyzes of defatted apple seed flours were firstly done in our study. According to these analyzes, total phenolic content, DPPH and ABTS radical scavenging activity of defatted seed flours were determined between 2861 and 5141 mg GAE/kg defatted seed, 21.45–43.56 μmol, and 291.50–391.79 μmol Trolox/g defatted seed, respectively. It was observed that the content of phloridzin represented 52–67% and 75–83% of the total phenolics that measured by the Folin-Ciocalteu assay and HPLC method, respectively. In the second part, chewing gums including defatted seeds were prepared and characterized in terms of phloridzin dissolution. The novel model described dissolution kinetics of phloridzin from chewing gum better than Higuchi and Korsmeyer-Peppas models. The results de- monstrated that 5 min was enough for the dissolution of almost all phloridzin (88.43–96%) determined by centrifugation method and according to the model parameters, the chewing gum formulation can be optimized for providing controlled dissolution. In conclusion, chewing gum could be a suitable delivering material for phloridzin uptake, and apple seeds, a valuable agricultural by-product, could be evaluated in this way

Dispersion stability and thermal conductivity of propylene glycol based nanofluids

The dispersion stability and thermal conductivity of propylene glycol-based nanofluids containing Al2O3 and TiO2 nanoparticles were studied in the temperature range of 20–80 °C. Nanofluids with different concentrations of nanoparticles were formulated by the two-step method and no dispersant was used. In contrast to the common belief, the average particle size of nanofluids was observed to decrease with increasing temperature, and nanofluids showed an excellent stability over the temperature range of interest. Thermal conductivity enhancement for both studied nanofluids was a nonlinear function of concentration and was temperature independent. Theoretical analyses were also performed using existing models compared with experimental results. The model based on the aggregation theory appears to be the best