MULTIDIMENSIONAL GAS CHROMATOGRAPHY FOR THE SEPARATION OF TCDD ISOMERS

A multidimensional gas chromatographic technique with heartcutting was used for the determination of complex isomeric mixtures of tetra- chlorodibenzo-p-dioxins(TCDDs)which could not be completely separated on a single capillary column.When using so-called heartcutting technique ,only the interested single peak or section of the fraction eluting from the first column was transferred onto the second column with different stationary phase.Flame ionization detection was used as the monitor detector and electron capture detection as the main detector.This arrangement offers complete separation and avoids interference of the possible remained chlorinated solvents.The separation power of multi- dimensional GC was demonstrated by the determination of TCDD isomers.

Gain deeper insights into traditional Chinese medicines using multidimensional chromatography combined with chemometric approaches

Traditional Chinese medicines(TCMs)possess a rich historical background,unique theoretical framework,remarkable therapeutic efficacy,and abundant resources.However,the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms.To gain deeper insights into the phytochemicals and ensure the quality control of TCMs,there is an urgent need to enhance analytical techniques.Currently,two-dimensional(2D)chromatography,which incorporates two independent separation mechanisms,demonstrates superior separation capabilities compared to the traditional one-dimensional(1D)separation system when analyzing TCMs samples.Over the past decade,new techniques have been continuously developed to gain actionable insights from complex samples.This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs,encompassing 2D-gas chromatography(GC),2D-liquid chromatography(LC),as well as emerging three-dimensional(3D)-GC,3D-LC,and their associated data-processing approaches.These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis.Nevertheless,the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools.Considering that multidimensional chromatography is still a relatively nascent research field,further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development.

Multidimensional separation due to selective spherical agglomeration—Evidence of shape separation via X-ray microtomography

Objective of this work was to develop a novel method for characterizing real 3D shapes of particles smaller than 20μm by X-ray microtomography(X-RMT).Multidimensional separation of heterogenous solids through agglomeration in suspension will improve recycling processes as the particle shape and the agglomerate size are used for shape-selective separation.In the present paper we discuss the fundamentals of X-ray tomography and the experimental setup for selective spherical agglomeration in suspension.A specific preparation method of the particulate sample for X-RMT followed by 3D image processing,are essential for the shape analysis expressed as sphericity.We also discuss the limitation of this method due to the so-called Partial Volume Effect and particle clusters in the order of magnitude of X-RMT resolution.As proof of concept,we used a mixture of graphite platelets and spheronized graphite particles for a shape selective-agglomeration in suspension.The remaining fines were analyzed and showed more platelets than in the mixture.This indicates that spheronized particles are preferably bound in the agglomerates.These findings show that,based on the discussed sample preparation and a 3D image analysis in connection with X-RMT,particle shapes of micronized particles can be discriminated.