Chemometrically-aided general approach to novel adsorbents studies: Case study on the adsorption of pharmaceuticals by the carbonized leaves.

A chemometrically based approach was applied to select the most efficient drug adsorbent among the biochars obtained from the novel feedstock, the leaves of the invasive plant (). The representative target adsorbates (atenolol, paracetamol, ketorolac and tetracycline) were selected on the basis of their physicochemical properties to cover a wide chemical space, which is the usual analytical challenge. Their adsorption was investigated using design of experiments as a comprehensive approach to optimise the performance of the adsorption system, rationalise the procedure and overcome common drawbacks.

Phthalate content in toy samples available on the market of the Republic of Serbia.

Phthalates are a family of synthetic chemicals commonly used as plasticizers for polyvinyl chloride-based polymers. They are used in a variety of commercial consumer products, including children's toys. Exposure to phthalates is associated with various adverse health effects, such as developmental and reproductive disorders, liver and kidney toxicity, In the European Union, but also in the Republic of Serbia, restrictions have been imposed on the presence of seven phthalates in toys.

Development of Analytical Quality by Design Compliant Chaotropic Chromatography Method for Ziprasidone and Its Five Impurities Determination.

In this study, an AQbD-compliant chaotropic chromatography method for ziprasidone and the determination of its five impurities was developed. The influence of critical method parameters (initial and final methanol fraction in the mobile phase, gradient duration) on the set of selected critical method attributes (, , and ) was studied by Box-Behnken design. The errors resulting from the calculation of the model coefficients were propagated to the selected responses by Monte Carlo simulations, and their predictive distribution was obtained.

Analytical method development supported by DoE-DS approach for enantioseparation of (S,S)- and (R,R)-moxifloxacin.

In this paper, method for enantiomeric purity testing of fourth-generation fluoroquinolone, moxifloxacin hydrochloride, was developed and validated. Exceptional enantioselectivity for this assay was achieved using cyclodextrin type Chiral Stationary Phase (CSP), phenylcarbamate-β-cyclodextrin CSP, and mobile phase consisted of acetonitrile and triethylammonium acetate (TEAA) buffer. Analytical Quality by Design (AQbD) methodology, comprising Design of Experiments (DoE) - Design Space (DS) approach, was used for method development.

Predicting liquid chromatography-electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities.

A priori estimation of analyte response is crucial for the efficient development of liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS) methods, but remains a demanding task given the lack of knowledge about the factors affecting the experimental outcome. In this research, we address the challenge of discovering the interactive relationship between signal response and structural properties, method parameters and solvent-related descriptors throughout an approach featuring quantitative structure-property relationship (QSPR) and design of experiments (DoE). To systematically investigate the experimental domain within which QSPR prediction should be undertaken, we varied LC and instrumental factors according to the Box-Behnken DoE scheme.

Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids.

An alternative to the time-consuming and error-prone pharmacopoeial gas chromatography method for the analysis of fatty acids (FAs) is urgently needed. The objective was therefore to propose a robust liquid chromatography method with charged aerosol detection for the analysis of polysorbate 80 (PS80) and magnesium stearate. FAs with different numbers of carbon atoms in the chain necessitated the use of a gradient method with a Hypersil Gold C column and acetonitrile as organic modifier.

The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis.

Resolving complex sample mixtures by liquid chromatography in a single run is challenging. The so-called mixed-mode liquid chromatography (MMLC) which combines several retention mechanisms within a single column, can provide resource-efficient separation of solutes of diverse nature. The Acclaim Mixed-Mode WCX-1 column, encompassing hydrophobic and weak cation exchange interactions, was employed for the analysis of small drug molecules.

Generic approach in a gradient elution HPLC method development that enables troubleshooting free method transfer.

Nowadays, method development is strongly focused on reducing time needed for method development and execution. This subject specially concerns gradient elution methods regarding the usual need for troubleshooting assistance with uncertain outcome during the method transfer from one laboratory to another. One of the main reasons for this situation is the dwell volume difference between HPLC systems.

Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach.

The charged aerosol detector (CAD) is the latest representative of aerosol-based detectors that generate a response independent of the analytes' chemical structure. This study was aimed at accurately predicting the CAD response of homologous fatty acids under varying experimental conditions. Fatty acids from C12 to C18 were used as model substances due to semivolatile characterics that caused non-uniform CAD behaviour.

A comprehensive study on retention of selected model substances in β-cyclodextrin-modified high performance liquid chromatography.

The quantitative structure-retention relationship (QSRR) models are not only employed in retention behaviour prediction, but also in an in-depth understanding of complex chromatographic systems. The goal of the present research is to enable the comprehensive understanding of retention underlying the separation in β-cyclodextrin (CD) modified reversed-phase high performance liquid chromatography (RP-HPLC) systems, through the development of mixed QSRR models. Moreover, the amount of β-CD adsorbed on the stationary phase surface (β-CD) is added as the model's input in order to evaluate its contribution to both model performances and retention.

Corona Charged Aerosol Detector in studying retention and β-cyclodextrin complex stability using RP-HPLC.

Binding between cyclodextrin (CD) cavity and guest molecule in Reversed Phase High-Performance Liquid Chromatography (RP-HPLC) is dynamic process. In general, increasing CD concentration is inducing inclusion complex formation, leading to reduction of analyte's retention time. Consequently, the shortness in retention time is a measure of complex stability in HPLC.

Performance comparison of nonlinear and linear regression algorithms coupled with different attribute selection methods for quantitative structure - retention relationships modelling in micellar liquid chromatography.

In micellar liquid chromatography (MLC), the addition of a surfactant to the mobile phase in excess is accompanied by an alteration of its solubilising capacity and a change in the stationary phase's properties. As an implication, the prediction of the analytes' retention in MLC mode becomes a challenging task. Mixed Quantitative Structure - Retention Relationships (QSRR) modelling represents a powerful tool for estimating the analytes' retention.

Quantitative structure retention relationship modeling as potential tool in chromatographic determination of stability constants and thermodynamic parameters of β-cyclodextrin complexation process.

When cyclodextrins (CDs) are used in chromatography analytes' retention time is decreased with an increase in concentration of CD in the mobile phase. Thus complex stability constants can be determined from the change in retention time of the ligand molecule upon complexation. Since the preceding approach implies extensive and time-consuming HPLC experiments, the goal of this research was to investigate the possibility of using in silico prediction tools instead.

Analytical quality by design development of an ecologically acceptable enantioselective HPLC method for timolol maleate enantiomeric purity testing on ovomucoid chiral stationary phase.

Official method in Ph. Eur. for evaluation of timolol enantiomeric purity is normal-phase high performance liquid chromatography (NP-HPLC) method.

Quantitative structure-property relationship modeling of polar analytes lacking UV chromophores to charged aerosol detector response.

In this study, a quantitative structure-property relationship model was built in order to link molecular descriptors and chromatographic parameters as inputs towards CAD responsiveness. Aminoglycoside antibiotics, sugars, and acetylated amino sugars, which all lack a UV/vis chromophore, were selected as model substances due to their polar nature that represents a challenge in generating a CAD response. Acetone, PFPA, flow rate, data rate, filter constant, SM5_B(s), ATS7s, SpMin1_Bh(v), Mor09e, Mor22e, E1u, R7v+, and VP as the most influential inputs were correlated with the CAD response by virtue of ANN applying a backpropagation learning rule.

Quantitative structure -retention relationship modeling of selected antipsychotics and their impurities in green liquid chromatography using cyclodextrin mobile phases.

Applying green chromatography methods is currently one of the challenges in liquid chromatography. Among different strategies, using cyclodextrin (CD) mobile phase modifiers was applied in this paper. CDs can form inclusion complexes with a wide variety of hydrophobic organic compounds and, consequently, affect their retention behavior.

Multicriteria Optimization Methodology in Stability-Indicating Method Development of Cilazapril and Hydrochlorothiazide.

Multicriteria optimization methodology was applied in development of UHPLC-UV-MS method for separation of cilazapril, hydrochlorothiazide and their degradation products. This method is also applicable for analysis of cilazapril, hydrochlorothiazide and their degradation products in combined tablet formulation. Prior to method optimization forced degradation studies were conducted.

Structure-response relationship in electrospray ionization-mass spectrometry of sartans by artificial neural networks.

Quantitative structure-property relationship (QSPR) methods are based on the hypothesis that changes in the molecular structure are reflected in changes in the observed property of the molecule. Artificial neural network is a technique of data analysis, which sets out to emulate the human brain's way of working. For the first time a quantitative structure-response relationship in electrospray ionization-mass spectrometry (ESI-MS) by means of artificial neural networks (ANN) on the group of angiotensin II receptor antagonists--sartans has been established.

Quantitative structure-retention relationships applied to development of liquid chromatography gradient-elution method for the separation of sartans.

QSRR are mathematically derived relationships between the chromatographic parameters determined for a representative series of analytes in given separation systems and the molecular descriptors accounting for the structural differences among the investigated analytes. Artificial neural network is a technique of data analysis, which sets out to emulate the human brain's way of working. The aim of the present work was to optimize separation of six angiotensin receptor antagonists, so-called sartans: losartan, valsartan, irbesartan, telmisartan, candesartan cilexetil and eprosartan in a gradient-elution HPLC method.

Liquid chromatography/tandem mass spectrometry for simultaneous determination of undeclared corticosteroids in cosmetic creams.

Rationale: Undeclared corticosteroids in creams intended for frequent use might cause serious side-effects, especially in children. In order to prevent this or find the cause, it was essential to develop a method for quick detection and quantification of low levels of corticosteroids.

Methods: Eleven corticosteroids were used in this study: prednisolone, methylprednisolone, prednisolone-21-acetate, fluocinolone acetonide, fluocinolone acetonide-21-acetate, hydrocortisone-21-acetate, dexamethasone, betamethasone, betamethasone dipropionate, clobetasol propionate and triamcinolone.

Quantitative structure-retention relationships of azole antifungal agents in reversed-phase high performance liquid chromatography.

Artificial neural network (ANN) is a learning system based on a computational technique which can simulate the neurological processing ability of the human brain. It was employed for building of the quantitative structure-retention relationships (QSRRs) model of antifungal agents-imidazoles or triazoles by structure. Computed molecular descriptors together with the percentage of acetonitrile in mobile phase (v/v) and buffer pH, being the most influential HPLC factors, were used as network inputs, giving the retention factor as model output.

Chemometrically assisted development and validation of LC-UV and LC-MS methods for simultaneous determination of torasemide and its impurities.

Complete evaluation of chromatographic behavior and establishment of optimal experimental conditions for determination of torasemide and its four impurities are determined by experimental design. Fractional factorial and 3(n) full factorial design were employed for efficient and rapid optimization of liquid chromatography-ultraviolet and liquid chromatography-mass spectrometry (LC-MS) methods. Separation is achieved on a Zorbax SB C(18) analytical column (250 x 4.

Development and validation of reversed phase high performance liquid chromatographic method for determination of moxonidine in the presence of its impurities.

A simple, rapid, isocratic reversed-phase high-performance liquid chromatographic method was developed and validated for the analysis of moxonidine and its impurities in tablet formulations. The chromatographic separation was achieved on a Symmetry shield C18 column (250 mm × 4.6 mm, 5 μm) by employing a mobile phase consisting of methanol-potassium phosphate buffer (0.

Determination of carbamazepine and its impurities iminostilbene and iminodibenzyl in solid dosage form by column high-performance liquid chromatography.

An accurate and precise RP-HPLC method was developed and validated for the determination of carbamazepine and its impurities iminostilbene and iminodibenzyl in a tablet formulation with fluphenazine as an internal standard. Buffer-methanol (50 + 50, v/v) was used as the mobile phase. During validation, specificity, linearity, precision, accuracy, LOD, LOQ, and robustness of the method were tested.