Electroanalytical investigation of paracetamol on glassy carbon electrode by voltammetry

An electroanalytical method was developed for the direct quantitative determination of paracetamol (or acetaminophen) in tablet dosage forms based on its oxidation behavior. The electrochemical oxidation and determination of paracetamol were easily carried out on glassy carbon electrode (GCE) using a variety of voltammetric techniques. The electrochemical measurements were carried out on GCE in various buffer solutions in the pH range from 0.51 to 12.00 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The dependence of pH on the anodic peak current and peak potential was investigated. Acetate buffer (pH 4.51) was selected for analytical purposes. Scan rate studies were also completed. The diffusion controlled nature of the peak was established. A linear calibration curve for DPV analysis was constructed in the paracetamol concentration range from 4x10-6 mol/L to 1x10-4 mol/L. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.69x10-7 mol/L and 1.23x10-6 mol/L respectively. Validation of applied voltammetric techniques was checked with recovery studies. © 2015 The Authors

An Investigation of Recovery Mechanisms for Oil Field Optimization by Three-Phase Core Flood and Simulation Studies

Two potential recovery mechanisms are being considered for a major field which required laboratory measurements to investigate the efficiency of the two scenarios: gas flood followed by water flood and water flood followed by gas flood. Although simply stated, the recovery scenarios involved complex three-phase processes which had to be replicated in the laboratory at reservoir conditions to provide reliable data upon which reservoir development decisions could be made. The first sequence consisted of water displacing oil to residual oil saturation (Sorw), oil displacing water to residual water saturation (Swro) and gas displacing both oil and water to Sor3φ,g and Swr3φ,g. The second sequence consisted of gas displacing oil to residual oil saturation (Sorg), oil displacing gas to trapped gas saturation (Sgto) and water displacing both oil and gas to Sor3φ,w and Sgt3φ,w respectively. Composite cores of four well-matched plugs at Swi were used and all measurements were made at bubble point conditions. A vertical core holder was housed inside a reservoir condition facility equipped with gamma attenuation saturation monitoring (GASM). Temperature stability and the use of GASM were paramount for the accurate measurement of produced fluids, especially trapped gas saturation. Oil, gas and water produced volumes were also measured using a separator housed inside the core flood oven to provide optimum temperature stability. The laboratory results were modelled in a compositional simulator using an equation of state tuned to conventional PVT data and both swelling and multiple contact experiments. The objective was to build a three-phase predictive model from the constituent two-phase relative permeability data. The paper details the experimental methods and presents results for each section of the two sequences. The key conclusions are that Sorg>Sorw> Sor3φ,g> Sor3φ,w and Sgt3φ,w< Sgto

Electroanalytical Investigation of Paracetamol on Glassy Carbon Electrode by Voltammetry

An electroanalytical method was developed for the direct quantitative determination of paracetamol (or acetaminophen) in tablet dosage forms based on its oxidation behavior. The electrochemical oxidation and determination of paracetamol were easily carried out on glassy carbon electrode (GCE) using a variety of voltammetric techniques. The electrochemical measurements were carried out on GCE in various buffer solutions in the pH range from 0.51 to 12.00 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The dependence of pH on the anodic peak current and peak potential was investigated. Acetate buffer (pH 4.51) was selected for analytical purposes. Scan rate studies were also completed. The diffusion controlled nature of the peak was established. A linear calibration curve for DPV analysis was constructed in the paracetamol concentration range from 4x10(-6) mol/L to 1x10(-4) mol/L. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.69x10(-7) mol/L and 1.23x10(-6) mol/L respectively. Validation of applied voltammetric techniques was checked with recovery studies

Electrooxidation of Phenazopyridine Hydrochloride and its Voltammetric and HPLC Determination in Human Urine and Tablet Dosage Form

The electrochemical oxidation of phenazopyridine hydrochloride (PAP) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques at ultra trace graphite electrode (UTGE). PAP exhibited a diffusion controlled process which is pH dependence. The dependence of the current and potential on pH, the concentration and nature of buffer, and scan rate was investigated to optimize the experimental conditions for the determination of PAP. It was found that the optimum buffer for the determination of PAP is 0.1 NaOH solutions with the pH 12.97. In the concentration range from 6.0x10(-8) to 1.0x10(-6) M, the current measured by DPV present a good linear property as a function of the concentration of PAP. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 8.1x10(-10) and 2.7x10(-9) M, respectively. PAP was determined in human urine and tablet dosage form. Precision and accuracy of the developed technique were checked by recovery studies in spiked urine and tablet dosage form. In addition, for the comparison, high performance liquid chromatography (HPLC) technique was applied for the determination of PAP in the same samples.Scientific and Technical Research Council of Turkey (TUBITAK) [TBAG-2173, 102T062]; Ege University Department of Scientific Research Projects (BAP) [05/ECZ/007]The authors gratefully acknowledge to the Scientific and Technical Research Council of Turkey (TUBITAK, Grant No: TBAG-2173; 102T062). The authors would also like to thank Faco Inc., (Istanbul, Turkey) for supplying pure PAP and its commercial tablet forms for proposed voltammety and comparison HPLC technique. Emrah KILINC acknowledges financial support from Ege University Department of Scientific Research Projects (BAP, Project number: 05/ECZ/007)

Electrocatalytic oxidation of moxifloxacin hydrochloride on modified glassy carbon surface and determination in Avelox tablets

This work presents an electroanalytical method for the determination of moxifloxacin hydrochloride (MOX) in tablets. The surface of the glassy carbon electrode (GCE) was modified by electrochemical polymerization of 4-aminobenzene sulfonic acid in phosphate buffer solution (pH 7.0).The oxidative behavior of MOX was studied at glassy carbon and modified glassy carbon electrodes in different buffer systems using the cyclic voltammetry technique. The modified glassy carbon electrode (poly(4-ABSA/GCE) has very high catalytic ability for electrooxidation of MOX. Acetate buffer (pH 5.0) was selected as the optimum medium for the oxidation of MOX at poly(4-ABSA/GCE) due to the highest electronic signal increase obtained. Differential pulse voltammetry (DPV) and chronoamperometry (CA) techniques were used for voltammetric determination of MOX. The values of limit of detection (LOD) and limit of quantification (LOQ) were determined to be 3.19×10 -7 M and 1.06×10 -6 M for DPV; and 5.50×10 -7 M and 1.83×10 -6 M for CA, respectively. A highly sensitive electroanalytical method for the determination of MOX in Avelox tablets by DPV was described. © 2019 Bulgarian Academy of Sciences, Union of Chemists in BulgariaGaziosmanpasa University Scientific Research Fund, (2016/76); Gaziosmanpasa Üniversites

Health and health belief factors associated with screening and help-seeking behaviours for breast cancer symptoms: a systematic review and meta-analysis of the European evidence

Purpose: The aim of this systematic review was to identify health or health belief factors associated with mammography attendance or with self-initiated medical help-seeking for breast cancer symptoms among women in Europe. Methods: Five databases were searched for articles published between 2005 and 2018. Meta-analyses were conducted for 13 factors related to screening attendance and two factors associated with help-seeking behaviour. Where there were too few studies to include in the meta-analysis a narrative synthesis was undertaken. Results: Sixty-five studies were included. Never having had cervical screening (d=-0.72, p<0.001) and higher perceived barriers to mammography (d=-0.40, p<0.001) were associated with lower levels of screening attendance. Possessing health insurance (d=0.49, p<0.001), greater perceived benefits (d=0.31, p<0.001) and motivation (d=0.36, p=0.003) towards screening, and higher perceived seriousness (d=0.24, p=0.019) and susceptibility (d=0.20, p=0.024) towards breast cancer were associated with a higher level of screening attendance. Presenting with a non-lump symptom was associated with a longer time to presentation (d=0.32, p<0.001). The narrative synthesis revealed that previous benign breast disease was associated with a higher level of screening attendance but with a longer time to presentation. Conclusions: The review identified key similarities in factors associated with screening and help-seeking behaviours which offer scope for combined interventions aimed at women that target both behaviours. Furthermore, the review highlighted that fewer studies have focused on help-seeking behaviour, despite two thirds of breast cancer cases being self-detected. Future research should further examine predictors of help-seeking behaviour including a focus on modifiable factors, such as BMI, and physical activity