Stepwise injection determination of isoniazid in human urine samples coupled with generalized calibration method

Large-scale flow analysis: From repetitive assays to expert analyzers

Flow analysis is usually associated with repetitive assays, as all samples of a batch are generally handled in the same way. By exploiting computer-controlled devices (e.g. pumps, valves, injectors, commuters, and samplers), this scenario has been expanded, as a proper manifold dimensioning can be set for each sample. Initially, this dimensioning relied on previous information about each sample, added to the operating software prior to analysis of a given sample lot. Further, real-time decisions relying on feedback mechanisms started to be exploited for improving the analytical figures of merit, simplifying the laboratory management, and allowing real-time system optimization and fault detection. This is the essence of the expert flow analyzers, which involve manifold re-dimensioning by means of flow/manifold programming, often relying on multicommutation. The development of flow analysis from repetitive to real-time defined assays, the involved terminology, and trends on further development are highlighted in this review. Applications involve segmented and unsegmented flow analysis of agronomical, clinical, environmental, industrial, pharmaceutical, and geological samples.

Bioanalytical methodology for determination of glutamate and aspartate for use in pharmacological sciences with application of Integrated Calibration Method

A new calibration approach based on the adaptation of Integrated Calibration Method (ICM) to consecutive two components analysis in separation science is presented. Consecutive ICM method (C-ICM) was conceptually developed and applied to determination of two excitatory amino acids - glutamate and aspartate in cerebrospinal fluids collected by the use of brain microdialysis from freely-moving animals. Both analytes as a neurotransmitters play an important role in formation of the memory trace, and thus the processes of learning and memory. Due to their low concentration and presence of interferences, considered analytical system - animal brain - was a big challenge. High-performance liquid chromatography (HPLC) with electrochemical detection (ECD) was used in all experimental work. The most important feature of proposed method is integration of interpolative and extrapolative ways to calculate analyte concentration in single calibration procedure, which consequently leads to obtain series of six estimations of analytical result. Comparison of individual estimations with each other allows for a more in-depth analysis of systematic errors. It was proved that C-ICM approach enables diagnosis and compensation of systematic errors induced by occurrence of interference effects and improvement of accuracy of analytical results. Most of all, it was demonstrated that application of this method is efficient and useful analytical tool in analysis of complicated biological samples in pharmacology and neuroscience.

Univariate analytical calibration methods and procedures. A review

An original focus on univariate calibration as an experimental process of quantitative analysis is presented. A novel classification system is introduced against the background of the present situation concerning nomenclature of calibration methods. Namely, it has been revealed that four methods well-known in analytical chemistry: the conventional method, the internal standard method, the indirect method and the dilution method, can be split into those carried out in both the interpolative and the extrapolative mode. It is then shown that the basic procedures of all these methods can be modified including different approaches, such as matrix-matched technique, spiking the sample with a reactant, bracketing calibration, and others. For the first time (as compared to monographies dealing with univariate calibration) it is reviewed how the methods are mixed and integrated with one another thereby creating new calibration strategies of extended capabilities in terms of enhanced resistance to the interference and non-linear effects - as the main sources of systematic calibration errors. As additional novelty, rationally possible combinations of the calibration methods - not met hitherto in the literature - have been predicted. Finally, some general rules relating to calibration are formulated and the main calibration problems that still need to be solved are displayed.