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Spatial comprehensive three-dimensional chromatography (3D-LC) offers an innovative approach to achieve unprecedented resolving power in terms of peak capacity and sample throughput. This advanced technique separates components within a 3D separation space, where orthogonal retention mechanisms are incorporated. The parallel development of the second- and third-dimension stages effectively overcomes the inherent limitation of conventional multidimensional approaches, where sampled fractions are analyzed sequentially. This review focuses on the design aspects of the microchip for spatial 3D-LC and the selection of orthogonal separation modes to enable the analysis of intact proteins. The design considerations for the flow distributor and channel layout are discussed, along with various approaches to confine the flow during the subsequent development stages. Additionally, the integration of stationary phases into the microchip is addressed, and interfacing to mass spectrometry detection is discussed. According to Pareto optimality, the integration of isoelectric focusing, size-exclusion chromatography, and reversed-phase chromatography in a spatial 3D-LC approach is predicted to achieve an exceptional peak capacity of over 30,000 within a 1-h analysis, setting a new benchmark in chromatographic performance.

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High-performance thin-layer chromatography has favorable properties for high-throughput separations with a high matrix tolerance. Sample preparation, however, is sometimes required to control specific matrix interferences and to enhance the detectability of target compounds. Trends in contemporary applications have shifted from absorbance and fluorescence detection to methods employing bioassays and mass spectrometry. Traditional methods (shake-flask, heat at reflux, Soxhlet, and hydrodistillation) are being challenged by automated instrumental approaches (ultrasound-assisted and microwave-assisted solvent extraction, pressurized liquid extraction, and supercritical fluid extraction) and the quick, easy cheap, efficient, rugged, and safe extraction method for faster and streamlined sample processing. Liquid-liquid extraction remains the most widely used approach for sample clean-up with increasing competition from solid-phase extraction. On-layer sample, clean-up by planar solid-phase extraction is increasingly used for complex samples and in combination with heart-cut multimodal systems. The automated spray-on sample applicator, the elution head interface, biological detection of target and non-target compounds, and straightforward mass spectrometric detection are highlighted as the main factors directing current interest toward faster and simpler sample workflows, analysis of more complex samples, and the determination of minor contaminants requiring high concentration factors.

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Contamination of foods with mineral oil hydrocarbons, particularly mineral oil aromatic hydrocarbons (MOAH), can potentially pose a health hazard to consumers. However, identifying toxic substances among the many thousands of compounds comprising mineral oils in food samples is a difficult analytical challenge. According to the European Food Safety Authority, there is a lack of concentration and structural data about mineral oil hydrocarbons in foods, and therefore it is not clear to what extent consumers in Europe might be exposed to toxic levels of MOAH. The current gold standard method for determination of mineral oil hydrocarbons is online high-performance liquid chromatography (LC)-gas chromatography (GC) with flame ionization detection, which quantifies total saturated/aromatic content, but gives no qualitative information. The objective of this review is to explore the future prospects in mineral oil hydrocarbon determination and MOAH characterization in foods. To that end, peer reviewed literature was explored, particularly from the viewpoint of a methodology for detailed characterization of the MOAH fraction that can aid toxicological assessment. The literature clearly shows that there is much to be gained from the orthogonality power of multidimensional chromatographic separations and mass spectrometric (MS) detection. Comprehensive two-dimensional GC coupled to MS, preceded by pre-fractionations of MOAH by LC is suggested to be the most promising approach for further research. In addition, the strengths and weaknesses of a number of other, alternative approaches, both for qualitative and quantitative analysis, are discussed.

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ETHNOPHARMACOLOGICAL RELEVANCE: Kava (Piper methysticum G. Forst) is a plant grown in the Pacific that is used in traditional medicines. The roots are macerated and powdered for consumption as a beverage in social settings as well as in ceremonies. Other types of preparations can also be used as traditional medicines. There has been an increase in demand for kava as there is continued traditional use and as it is becoming utilized more both socially and medicinally outside of Oceania. Currently, most research of this plant has focused on bioactive kavalactones and flavokawains, and there are few studies focusing on the other compounds that kava contains, such as volatile and semivolatile components. AIM OF THE STUDY: This study investigated the kava volatile organic compound (VOC) profile from nine different commercially available samples of dried, powdered kava root sourced across the Pacific region. MATERIALS AND METHODS: The headspace above the kava samples was analyzed, both from the root powder as originally purchased and by performing a scaled-down extraction into water mimicking traditional preparation of the beverage. The headspace of each sample was extracted using solid-phase microextraction arrow (SPME Arrow), followed by analysis using comprehensive two-dimensional gas chromatography - quadrupole mass spectrometry/flame ionization detection (GC×GC-qMS/FID). The superior peak capacity of GC×GC was invaluable in effectively separating the complex mixture of compounds found in all samples, which enabled improved monitoring of minor differences between batches. RESULTS: Dry root powder samples contained high levels of ß-caryophyllene while water extracted samples showed high levels of camphene. Many alcohols, aldehydes, ketones, terpenes, terpenoids, and aromatics were also characterized from both types of samples. All water extracted samples from the different brands followed similar trends in terms of compounds being detected or not. Additional major compounds found in water extracts included benzaldehyde, hexanal, methoxyphenyloxime, camphor, limonene, 1-hexanol, endoborneol, and copaene. While some samples could be differentiated based on brand, samples did not group by purported geographic origin. CONCLUSIONS: This study provides foundational data about a different subset of compounds within kava than previous research has studied, and also informs the community of the compounds that transfer into the consumed beverage during the traditional means of preparing kava.

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INTRODUCTION: Ion mobility-mass spectrometry is an emerging technology in the clinical setting for high throughput and high confidence molecular characterization from complex biological samples. Ion mobility spectrometry can provide isomer separations on the basis of molecular structure, the ability of which is increasing through technological developments that afford enhanced resolving power. Integrating multiple separation dimensions, such as liquid chromatography-ion mobility-mass spectrometry (LC-IM-MS) provide dramatic enhancements in the mitigation of molecular interferences for high accuracy clinical measurements. AREAS COVERED: Multidimensional separations with LC-IM-MS provide better selectivity and sensitivity in molecular analysis. Mass spectrometry imaging of tissues to inform spatial molecular distribution is improved by complementary ion mobility analyses. Biomarker identification in surgical environments is enhanced by intraoperative biochemical analysis with mass spectrometry and holds promise for integration with ion mobility spectrometry. New prospects in high resolving power ion mobility are enhancing analysis capabilities, such as distinguishing isomeric compounds. EXPERT OPINION: Ion mobility-mass spectrometry holds many prospects for the field of isomer identification, molecular imaging, and intraoperative tumor margin delineation in clinical settings. These advantages are afforded while maintaining fast analysis times and subsequently high throughput. High resolving power ion mobility will enhance these advantages further, in particular for analyses requiring high confidence isobaric selectivity and detection.

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High-resolution separation systems are essential for the analysis of complex mixtures in a wide variety of application areas. To increase resolution, multidimensional chromatographic techniques have been one key solution. Supercritical fluid chromatography provides a unique opportunity in these multidimensional separations based on its potential for high solvent compatibility, rapid duty cycles, and orthogonality to other separation modes. This review focuses on two-dimensional chromatography methods from the past decade that use supercritical fluid chromatography because of these advantages. Valving schemes and modulation strategies used to interface supercritical fluid chromatography with other liquid chromatography and gas chromatography techniques are described. Particular applications of multidimensional separations using supercritical fluid chromatography for the analysis of oils and chiral separations of pharmaceutical compounds are highlighted. Limitations of and a potential trajectory for supercritical fluid chromatography in this field are also discussed.

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The determination of residues and contaminants in complex matrices such as in the case of food, environmental, and biological samples requires a combination of several steps to succeed in the aimed goal. At least three independent steps are integrated to provide the best available situation to deal with such matrices: (1) a sample preparation technique is employed to isolate the target compounds from the rest of the matrix; (2) a chromatographic (second) step further "purifies" the isolated compounds from the co-extracted matrix interferences; (3) a spectroscopy-based device acts as chromatographic detector (ideally containing a tandem high-resolution mass analyzer) for the qualitative and quantitative analysis. These techniques can be operated in different modes including the off-line and the on-line modes. The present report focus the on-line coupling techniques aiming the determination of analytes present in complex matrices. The fundamentals of these approaches as well as the most common set ups are presented and discussed, as well as a review on the recent applications of these two approaches to the fields of bioanalytical, environmental, and food analysis are critically discussed.

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Food safety is a priority public health concern that demands analytical methods capable to detect low concentration level of contaminants (e.g. pesticides and antibiotics) in different food matrices. Due to the high complexity of these matrices, a sample preparation step is in most cases mandatory to achieve satisfactory results being usually tedious, lengthy, and prone to the introduction of errors. For this reason, many research groups have focused efforts on the development of online systems capable to do the cleanup, concentration, and separation steps at once through multidimensional separation techniques (MDS). Among several possible setups, the most popular are the multidimensional chromatographic techniques (MDC) that consist in combining more than one mobile and/or stationary phase to provide a satisfactory separation. In the present review, we selected a variety of multidimensional separation systems used for food contaminant analysis in order to discuss the instrumentation aspects, the concept of orthogonality, column approaches used in these systems, and new materials that can be used in these columns. Selected classes of contaminants present in food matrices are introduced and discussed as example of the potential applications of multidimensional liquid phase separation techniques in food safety.

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The HPLC 2015 Conference was held from 21 to 25 June at the International Conference Center in Geneva, Switzerland. The emphasis of the meeting was around fundamental aspects of separations, sample preparation, novel developments and applications and hyphenation with MS. In this conference report, a selection of highlights of the Conference is given, based on the sessions attended by the authors, and focusing on subjects with possible relevance in the field of drug metabolism and bioanalysis. Selected papers from HPLC 2015 will be published in a virtual special issue of the Journal of Chromatography.

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In the domain of liquid phase separations, the quality of separation obtainable is most readily gauged by consideration of classical chromatographic peak capacity theory. Column-based multidimensional strategies for liquid chromatography remain the most attractive and practical route for increasing the number of spatially resolved components in order to reduce stress on necessary mass spectrometric detection. However, the stress placed on a chromatographic separation step as a second dimension in a comprehensive online methodology (i.e. online LC×LC) is rather high. As an alternative to online LC×LC combinations, coupling of HPLC with ion mobility spectrometry hyphenated to mass spectrometry (IMS-MS) has emerged as an attractive approach to permit comprehensive sampling of first dimension chromatographic peaks and subsequent introduction to an orthogonal IMS separation prior to measurement of ions by a mass spectrometer. In the present work, utilization of classical peak capacity and ion mobility theory allows theoretical assessment of the potential of two- (LC×IMS-MS) or even three-dimensional (LC×LC×IMS-MS) experimental setups to enhance peak capacity and, therefore, the number of correctly annotated features within the framework of complex, non-targeted analysis problems frequently addressed using HPLC-MS strategies. Theoretical calculations indicate that newly-available drift tube IMS-MS instrumentation can yield peak capacities of between 10 and 40 using nitrogen drift gas for typical non-targeted metabolomic, lipidomic and proteomic applications according to the expected reduced mobilities of components in the respective samples. Theoretically, this approach can significantly improve the overall peak capacity of conventional HPLC-(MS) methodologies to in excess of 10(4) depending upon the column length and gradient time employed. A more elaborate combination of LC×LC×IMS-MS would improve the ion suppression limitation and possibly allow access to theoretically even higher peak capacities, but such a combination may render the IMS separation practically redundant as well as imparting the well-known dilution problems associated with LC×LC. Finally, some predictions for the separation of co-eluted isobaric compounds can also be made by considering the required peak-to-peak resolution for acceptable IMS separation. The here-described theoretical predication approach can be used to aid method development for HPLC×IMS-MS and is also accompanied by some practical considerations that should be contemplated in associated non-targeted analysis workflows.

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Multidimensional separation where two or more orthogonal displacement mechanisms are combined is a promising approach to increase peak capacity in CE. The combinations allow dramatic improvement of analytical performance since the total peak capacity is given by a product of the peak capacities of all methods. The initial reports were concentrated on the construction of effective connections between capillaries for 2D analysis. Today, 2D and 3D CE systems are now able to separate real complex biological or environmental mixtures with good repeatability, improved resolution with minimal loss of sample. This review will present the developments in the field of multidimensional CE during the last 15 years. The endeavors in this specific field were on the development of interfaces, interface-free techniques including integrated separations, microdevices, and on-line sample concentration techniques to improve detection sensitivity.

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