SIMULATION OPTICS

A generic liquid chromatographic method development workflow was developed and successfully applied to the analysis of phytocannabinoids and Cannabis sativa extracts. Our method development procedure consists in four steps: At the end, this method development workflow was performed in less than 4 da …

Computer simulation was used to optimize high-performance liquid chromatography of phenol and its chloro and nitro derivatives. On the basis of two linear gradient runs of different steepness (RP-18-water + methanol + 1% acetic acid), several simulated gradient runs allowed the optimum gradient prog …

The Craig model (assuming a Langmuir isotherm) has been used by us previously to successfully simulate isocratic high-performance liquid chromatographic (HPLC) separation in a mass-overload mode. Here we have extended this approach to the case of gradient elution for large samples. These simulations …

An interface for a high-performance liquid chromatographic system based on the Commodore 64 personal computer has been designed as an alternative to the expensive and somewhat inflexible solvent programmers and data acquisition systems offered by commercial manufacturers. The system consists of the …

This article is Part II of a series describing a newly-developed gradient chromatofocusing high-performance liquid chromatography (HPLC) technique. Theoretical aspects of the technique are discussed. In gradient chromatofocusing, the column pH gradient with respect to column distance can be varied w …

A strategy for rapid optimization of liquid chromatography column temperature and gradient shape is presented. The optimization as such is based on the well established retention and peak width models implemented in software like e.g. DryLab and LC simulator. The novel part of the strategy is a high …

A package of Excel VBA macros have been developed for modeling multilinear gradient retention data obtained in single or double gradient elution mode by changing organic modifier(s) content and/or eluent pH. For this purpose, ten chromatographic models were used and four methods were adopted for the …

Availability of analytical method which is compatible with both Ultra high performance liquid chromatography (UHPLC) and Liquid chromatography mass spectrometry to identify and quantify the impurities in pharmaceutical products is an advantage for drug product development; such analytical method was …

This study reports the use of retention modeling software for the successful method development of 24 injectable antineoplastic agents. Firstly, a generic screening of several stationary and mobile phases (using various organic modifiers and pH) was achieved. Then, an optimization procedure of mobil …

In gradient chromatography for proteins migrating along the chromatographic column, the critical distance X0 has been shown to exist at which the separation of zones is at a maximum and band spreading is at a minimum. With steep gradients and small elution velocity, the column length may be reduced …

An important research direction in the continued development of two-dimensional liquid chromatography (2D-LC) is to improve the detection sensitivity of the method. This is especially important in applications where injection of large volumes of effluent from the first dimension (1D) colu …

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention …

Pharmaceutical companies worldwide tend to apply chiral chromatographic separation techniques in their mass production strategy rather than asymmetric synthesis. The present work aims to investigate the predictability of chromatographic behavior of enantiomers using DryLab HPLC method development so …

Computer-assisted procedures were used to simulate modifications in chromatograms caused by the transfer of elution programmes between instruments with significantly different dwell volumes. Moreover, for the first time the same approach was used to modify the elution programmes to match the chromat …

A membrane unit which can be used to inject a large volume of sample solution was developed to facilitate reproducible and accurate gradient elution in micro-high-performance liquid chromatography (micro-HPLC). Since the membrane unit has a very low void volume, it facilitates the effective concentr …

An optimization strategy for an isocratic reversed phase high performance liquid chromatographic system (RP-HPLC) is described. Factorial design and a computer program are used to predict the retention time and resolution of fourteen steroids. An optimized rapid (less than 25 min) isocratic RP-HPLC …

A rapid extraction procedure for mebendazole and its metabolites from plasma using Sep Pak C18 is described. This method eliminates the need for solvent extractions as such. Two reversed-phase high-performance liquid chromatographic determinations for these extracts, one isocratic elution and the ot …

The influence of some important experimental parameters on the resolution of compounds as well as the validity of widely used rules of thumb and of common expectations about how to improve resolution is discussed. It will be shown, on the basis of selected examples, that the general expectations abo …

A reversed-phase high-performance liquid chromatography (HPLC) method with gradient elution for the separation of angiotensin peptides is described. The highly reproducible method allows the base-line separation of angiotensin peptides with UV detection at 225 nm. This chromatographic methodology in …

The optimization of reversed-phase high-performance liquid chromatographic separation by the simultaneous variation of pH and solvent strength (%B) was studied for acidic (substituted benzoic acids) and basic samples (substituted anilines). The combination of these two variables was expected to be m …

We describe a method to study the monomer-dimer equilibrium of human growth hormone (hGH) making use of a very short size exclusion high-performance liquid chromatographic column and rapid flow rates. By adjusting the flow rate and thus the retention time on the column, the dissociation of the hGH d …

A high-performance liquid chromatographic method for the determination of free gossypol in chicken liver at levels down to 0.5 ppm has been developed. Tissue was deproteinized with acetonitrile in presence of ascorbic acid and the filtrate was subjected to hydrolysis with hydrochloric acid. The libe …

In this paper, the development of reversed-phase liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality by design (QbD) approach is presented. The defined analytical target profile (ATP) was the efficient baseline separation and th …

Population pharmacokinetics can be defined as a study of the basic features of drug disposition in a population, accounting for the influence of diverse pathophysiological factors on pharmacokinetics, and explicitly estimating the magnitude of the interindividual and intraindividual variability. It …

MicroRNAs (miRNAs) function as regulatory molecules of gene expression with multifaceted activities that exhibit direct or indirect oncogenic properties, which promote cell proliferation, differentiation, and the development of different types of cancers. Because of their extensive functional involv …

Target concentration intervention (TCI) is proposed as an alternative conceptual strategy to therapeutic drug monitoring (TDM). It is argued that the idea of a therapeutic range has limited the interpretation of measured drug concentrations and diminished the anticipated clinical benefit to patients …

Learn about acquiring an analog signal, including topics such as bandwidth, amplitude error, rise time, sample rate, the Nyquist Sampling Theorem, aliasing, and resolution.

The VirtualBench All-in-One Instrument combines a mixed-signal oscilloscope with protocol analysis, an arbitrary waveform generator, a digital multimeter, a programmable DC power supply, and digital I/O into a single device that connects to a PC or iPad.