An Automated Hydrodynamically Mediated Technique for Preparation of Calibration Solutions via Capillary Electrophoresis System as a Promising Alternative to Manual Pipetting.

In this paper, a novel procedure for preparing calibration solutions for capillary electrophoresis (CE)-based quantitative analysis is proposed. Our approach, named the automated hydrodynamically mediated technique (AHMT), uses a capillary and a pressure system to deliver the expected amount of working solution and diluent directly to a sample vial. As a result, calibration solutions are prepared automatically inside the CE instrument, without any or with minimal manual operation. Two different modes were tested: forward and reverse, differing in the direction of hydrodynamic flow. The calibration curves obtained for a model mixture of analytes using AHMT were thorough compared to the standard procedure based on manual pipetting. The results were consistent, though the volume of obtained calibration solutions and the potential risk of random errors were significantly minimized by AHMT. Its effectiveness was further enhanced by the application of SCIEX® nanoVials, reducing the actual volume of calibration solutions down to 10 µL.

What Color Is Your Method? Adaptation of the RGB Additive Color Model to Analytical Method Evaluation.

Evaluation of an analytical method is a fundamental problem in analytical chemistry, and it is never straightforward. In this article, we show a perspective for facing this issue using an original tool. We propose a model that allows one to evaluate any analytical method/procedure in a global manner. It refers to the RGB additive color model and uses three primary colors to represent three main attributes of the evaluated method: analytical performance - Red, compliance with the "green" chemistry principles - Green, and productivity/practical effectiveness - Blue. A final color of the method results from the additive synthesis of the primary colors. To simplify classifications, we propose the set of nine final colors of the method (white, magenta, cyan, yellow, red, green, blue, colorless/gray, and black). The model provides also a quantitative parameter, named the "method brilliance", which integrates all primary colors and treats them with varying importance, adjusted to the evaluation context and subjective user preferences. The evaluation is performed using standard Excel worksheets interpretable "at-a-glance" and adjustable to the particular method specifications. We discuss the opportunities offered by this model, potential obstacles, and related countermeasures, as well as future perspectives for its utilization. The paper shows also examples of using the model for the evaluation of real methods. We believe that the model can be applied not only in analytical science but also in other chemical subdisciplines.

On-line coupling between capillary electrophoresis and microscale thermophoresis (CE-MST); the proof-of-concept.

We demonstrate that microscale thermophoresis can be easily coupled with capillary electrophoresis in an on-line flow system (CE-MST), offering new potential possibilities. It takes advantage of sample separation and miniaturization prior to thermo-optical/MST analysis. No instrument modification is required. The future perspective is discussed.

Separation of 20 coumarin derivatives using the capillary electrophoresis method optimized by a series of Doehlert experimental designs.

The aim of this study was to develop the first CE-based method enabling separation of 20 structurally similar coumarin derivatives. To facilitate method optimization a series of three consequent Doehlert experimental designs with the response surface methodology was employed, using number of peaks and the adjusted time of analysis as the selected responses. Initially, three variables were examined: buffer pH, ionic strength and temperature (No. 1 Doehlert design). The optimal conditions provided only partial separation, on that account, several buffer additives were examined at the next step: organic cosolvents and cyclodextrin (No. 2 Doehlert design). The optimal cyclodextrin type was also selected experimentally. The most promising results were obtained for the buffers fortified with methanol, acetonitrile and heptakis(2,3,6-tri-O-methyl)-ß-cyclodextrin. Since these additives may potentially affect acid-base equilibrium and ionization state of analytes, the third Doehlert design (No. 3) was used to reconcile concentration of these additives with optimal pH. Ultimately, the total separation of all 20 compounds was achieved using the borate buffer at basic pH 9.5 in the presence of 10mM cyclodextrin, 9% (v/v) acetonitrile and 36% (v/v) methanol. Identity of all compounds was confirmed using the in-lab build UV-VIS spectra library. The developed method succeeded in identification of coumarin derivatives in three real samples. It demonstrates a huge resolving power of CE assisted by addition of cyclodextrins and organic cosolvents. Our unique optimization approach, based on the three Doehlert designs, seems to be prospective for future applications of this technique.