Abdil Özdemir

An application of derivative and continuous wavelet transforms to the overlapping ratio spectra for the quantitative multiresolution of a ternary mixture of paracetamol, acetylsalicylic acid and caffeine in tablets

Quantitative multiresolution of tablets and ternary mixtures of paracetamol (PAR), acetylsalicylic acid (ASP) and caffeine (CAF) having strongly overlapping spectra was accomplished by two graphical transform methods as ratio spectra first derivative-zero crossing and ratio spectra-continuous wavelet transform-zero crossing (ratio spectra CWT-zero crossing) methods. In this study, ratio spectra derivative-zero crossing and ratio spectra CWT-zero crossing methods are based on the use of transformed signals of the ratio spectra and their calibration graphs were obtained by measuring the dA/dlambda and CWT amplitudes of the ratio spectra corresponding to zero crossing points. For the comparison purpose, PLS calibration method was applied to predict the content of the same mixtures containing the subject active compounds. The obtained calibrations were tested by using the synthetic mixtures and standard addition technique and they applied to the simultaneous determination of PAR, ASP and CAF in commercial pharmaceutical preparation. The obtained results were statistically compared with each other as well as those obtained by HPLC method and they showed good agreement.

Electrode-assisted desorption electrospray ionization mass spectrometry

A new ion source has been developed for rapid, noncontact analysis of materials at ambient conditions. The method provides desorption of analytes under ambient conditions directly from different surfaces with little or no sample preparation. The new method, termed electrode-assisted desorption electrospray ionization (EADESI), is on the basis of the ionization of molecules on different surfaces by highly charged droplets produced on a sharp-edged high voltage tip, and ions produced are introduced into the mass spectrometer through a capillary. The EADESI technique can be applied to various samples including amino acids, peptides, proteins, drugs and human fluids such as urine and blood. EADESI is promising for routine analyses in different fields such as forensic, environmental and material sciences. EADESI interface can be fit to a conventional ion-trap mass spectrometer. It can be used for various types of samples with a broad mass range. EADESI can also provide real-time analysis which is very valuable for biomedical applications.

Chemometric Approach to Simultaneous Chromatographic Determination of Paracetamol and Chlorzoxazone in Tablets and Spiked Human Plasma

Abstract New chemometric approaches were introduced into the high performance liquid chromatographic (HPLC) determination of chlorzoxazone (CZX) and paracetamol (PAR) in the tablets and spiked human plasma. These chemometric approaches contain the application of classical least squares (CLS), principle component regression (PCR), and partial least squares (PLS) calibrations to the multiwavelength HPLC peak area obtained by plotting the chromatograms at the five wavelengths. The multichromatograms were obtained by using the photodiode array detector at 225 (A), 240 (B), 255 (C), 270 (D), and 285 (E) nm. The algorithms of CLS, PCR, and PLS were applied to the multichromatogram data to construct the HPLC‐CLS, HPLC‐PCR, and HPLC‐PLS calibrations. A mixture of acetonitrile and 0.1 M ammonium carbonate (60:40, v/v) on a Waters Symmetry® C18 Column 5 µm 4.6×250 mm at a flow rate of 0.8 mL/min was used as a mobile phase to separate and determine CZX and PAR in samples. Hydrochlorothiazide (IS) was used as an internal standard in this chromatographic separation. The HPLC chemometric calibrations were successfully applied to the quantitative analysis of the investigated drugs in commercial pharmaceutical preparation and spiked human plasma samples with high precision and accuracy.

A New Application of Chemometric Techniques to HPLC Data for the Simultaneous Analysis of a Two‐Component Mixture

Abstract A new chemometric approach using high performance liquid chromatography (HPLC) with photodiode array (PDA) detection was developed and applied to the simultaneous determination of enalapril maleate (EA) and hydrochlorothiazide (HCT) in tablets. Chemometric calibration techniques, classical least squares (CLS), principle component regression (PCR), and partial least squares (PLS) were subjected to the peak area at multiwavelength PDA detector responses. The combination of HPLC and chemometric calibration techniques was called HPLC‐CLS, HPLC‐PCR, and HPLC‐PLS. For comparison purposes, the HPLC method called classical HPLC method was used for the confirmation of the results obtained from combined HPLC‐chemometric calibration techniques. A good chromatographic separation between two drugs and internal standard (IS) was achieved using a Waters Symmetry® C18 Column 5 µm 4.6×250 mm and a mobile phase consisting of 0.2 M acetate buffer and acetonitrile (v/v, 60∶40). The multiwavelength PDA detection was done at 230 (A), 240 (B), 250 (C), 250 (D), 240 (E) nm wavelengths, and peak area was recorded for the concentration set in the mobile phase. Three HPLC‐chemometric calibrations and a classical‐HPLC method were tested by analyzing the synthetic mixture of EA and HCT in the presence of losartan potassium (IS). The proposed methods were applied to real samples containing the present two drugs. The obtained results were statistically compared with each other.

Simultaneous decolorization of binary mixture of blue disperse and yellow basic dyes by electrocoagulation

Abstract In this paper, electrocoagulation (EC) has been used for the removal of color from solution containing a disperse dye (Disperse blue 56) and a basic dye (Basic Yellow 28) in the same solution. Iron electrodes were arranged in a monopolar fashion. In the EC of the dye mixture, the effects of the supporting electrolyte, initial pH, electrolysis time, and current density were examined. The results indicated that the majority of the aforementioned dyes in the synthetic wastewater were effectively removed when iron electrodes were used as a sacrificial anode. The amount of dye removed was found by the application of the first derivative spectrophotometric method to the synthetic dye mixtures. In the presence of both dye molecules, the optimum pH was found to be 7, optimum NaCl concentration was 3,000 mg L−1, and optimum current density was 10.89 mA cm−2. The experimental data were fit to a variety of isotherm models to determine the characteristics of the EC process. The results indicated that the mod...

REMOVAL OF A BINARY DYE MIXTURE OF CONGO RED AND MALACHITE GREEN FROM AQUEOUS SOLUTIONS USING A BENTONITE ADSORBENT

An important application of clay is as a solid adsorbent for industrial dyes. The aim of the present work was to carry out an experimental-theoretical study of the adsorption of dye mixtures, namely malachite green (MG) and Congo red (CR), by bentonite. Adsorption studies were conducted after evaluation of the impact of several parameters, including pH, adsorbate dose, and contact time, on the removal of MG and CR. The pH of the dye solution is strongly affected by the chemistry of both the dye molecules and of the adsorbent in an aqueous solution. Where both dye molecules exist in solution, the optimum pH was found to be 8.2 in order to achieve the maximum adsorption of both MG and CR. Preliminary studies showed that 60 min of contact time is sufficient to reach adsorption equilibrium. The adsorption studies were carried out using 1.0 g samples of bentonite. The amount of dye adsorbed was found by application of classical least squares to the synthetic dye mixtures. Data from equilibrium adsorption on bentonite were analyzed by Freundlich, Langmuir, Redlich-Peterson, and Temkin isotherm equations using regression analysis for non-linear forms of those equations. For binary-mixture analysis, isotherm parameters were determined from single-component adsorption studies and the theoretical amount of dye adsorbed was calculated using an extended Langmuir isotherm. Non-linear error analysis showed that the Temkin and Redlich-Peterson isotherms gave the best fits to the equilibrium data for adsorptive removal of MG and CR by bentonite.

A deeper look into sonic spray ionization

Sonic spray ionization (SSI) has been explored as an ambient ionization method for mass spectrometric analysis of different compounds. It has been applied to the analysis of different groups of compounds, mostly small molecules. The work reported in this paper extends the ionization efficiency of SSI and application of SSI to different groups of compounds, mostly biomolecules, in an ion trap mass spectrometer. SSI does not use any power supply and produces both positive and negative ions simultaneously. The most important parameters in SSI are gas pressure, solvent flow rate and physical dimensions of the spray device. Although the first two parameters have been investigated by different groups, the effect of physical dimensions has not been reported in the literature. Silica capillary inner diameter (ID) and outer diameter (OD) and ID of the cone play important roles in a spray. The best explored dimensions for the silica capillary are 150–200 μm OD and 40–75 μm ID and 350 μm ID for the cone. These physical dimensions provide the best ionization efficiency and spectra of large proteins such as albumin can be obtained. The spectra of the samples can also be collected in water without adding any acid into the solution.

Triboelectric spray ionization

Triboelectric spray ionization (TESI) is a variation of electrospray ionization (ESI) using common instrumental components, including gas flow, solvent flow rate and heat, the only difference being the use of a high-voltage power supply for ESI or a static charge for TESI. The ionization of solvent or analyte is due to the electrostatic potential difference formed between the spray electrode and counter electrode. The ion source contains a pneumatic spray operated over a range of flow rates (0.15-1.5 µl/min) and gas pressures (0-100). This new design contains a standalone spray assembly and an optional metal mesh in front of the spray. There are several parameters that affect the performance during ionization of molecules including the flow rate of solvent, gas pressure, temperature, solvent acidity, distance and potential difference between emitter and counter electrode. A variable electrostatic potential can be applied for higher ionization efficiency. The new ionization method was successfully applied to solutions of various proteins under different conditions. The same charge-state distributions compared to other ESI techniques are observed for all the protein samples. The unique feature of TESI is very efficient spraying by using a natural electrostatic potential even at the potential that a human body can produce. This provides very gentle ionization efficiency of peptides and proteins in different solvents.

Quantifying Na(I)-insulin and K(I)-insulin non-covalent complexes by ESI–MS method and calculation of their equilibrium constants

In this study, the dissociation and formation equilibrium constants of Na(I)-insulin and K(I)-insulin complexes have been calculated after the quantifying them on ESI mass spectrometer. The ESI-MS spectra of the complexes were measured by using the solvents as 50% MeOH in water and 100% water. The effect of pH on the Na(I)-insulin and K(I)-insulin complex formation were examined. Serial binding of Na(I) and K(I) ions to the insulin molecule were observed in the ESI-MS measurements. The first formation equilibrium constants were calculated as Kf1: 5.48×103 1/M for Na(I)-insulin complex and Kf1: 4.87×103 1/M for K(I)-insulin in water. The binding capability of Na(I) ions to insulin molecule is higher than the capability of K(I) ions. In case of a comparison together with Ca(II)-insulin and Mg(II)-insulin, the formation equilibrium constants (Kf1) are in order of Ca(II)-insulin>Mg(II)-insulin>Na(I)-insulin>K(I)-insulin in water. The results showed that Na(I) and K(I) ions are involved in the formation of the non-covalent complexes with insulin molecule, since high extracellular and intracellular concentrations of them in the body.

Analysis of dietary minerals in selected seeds and nuts by using ICP-OES and assessment based on the recommended daily intakes

Purpose – Seeds and nuts include many dietary minerals as well as trace metals. It is very important to determine the nutritional mineral values in seeds and nuts. Many minerals can be analyzed simultaneously in low concentrations by using inductively coupled plasma-atomic emission spectroscopy. This paper aims to evaluate nutritional values of dietary and trace minerals in selected seeds and nuts. Design/methodology/approach – Dietary minerals in the sunflower seed (Helianthus annuus), pumpkin seed (Cucurbita pepo L.), peanut (Arachis hypogaea) and corn (Zea mays L.) samples collected from the markets in Sakarya city of Turkey have been analyzed. Two digestion procedures were applied by using hydrochloric acid solution and the mixture of nitric acid and hydrogen peroxide solution. Findings – In the evaluation of the mineral contributions of the nuts, the micro-mineral contributions (Cu, Fe, Zn, Mn and Se) were found at higher values than the macro-minerals (Ca, Mg, K and Na). Potassium was determined as ...