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Gas chromatography (GC) yields superior separations of low boiling point volatile compounds. Therefore, preparative gas chromatography (Prep GC) was established by combining analytical GC with a sample collection system at the end of the column, enabling the efficient isolation of the volatile components from complex matrices and their subsequent collection after GC. As Prep GC is based on an analytical gas chromatograph, its injection, separation, detection, and fraction collection systems are continuously optimized and upgraded to improve the recoveries and purities of the target compounds. Prep GC, in combination with modern spectroscopic techniques (such as UV-Vis absorption spectroscopy, infrared absorption spectroscopy, Raman spectroscopy, mass spectrometry, X-ray diffraction, and nuclear magnetic resonance spectroscopy), enables accurate structural elucidation of a target compound. Reports of the separations of various volatile components from complex matrices using Prep GC have recently increased annually, revealing promising application prospects. However, Prep GC also displays several disadvantages, such as the failure to separate thermolabile compounds, high separation costs, and the likely introduction of exogenous contamination. Based on the recent related research, this review summarizes the evolution of the structure of Prep GC and its application in isolating essential oil monomers, insect pheromones, volatile food and plant components, geological biomarkers, and persistent environmental pollutants. Finally, this review also summarizes and prospects the use of Prep GC in separating volatile components to provide a reference for the expansion of its applications.

Thin layer chromatography (TLC) is a very useful liquid chromatography approach. The simple device, convenient operation, versatility, high throughput capabilities, low cost, and simple sample pretreatments make it widely employed in various fields. In recent years, TLC-MS has become one of the most prominent trends for this technology as developments of modern analytical technology and comprehensive application of different approaches. With the development and upgrading of medicine, food, and scientific instrument industries, it is believed that TLC-MS technology should play a better role and obtain an opportunity for development. This study reviewed TLC-MS interface technologies (most of which are in recent 10 years) based on more than 150 studies and classified these TLC-MS technologies as three strategies. The first is indirect coupling using commercially available interface instruments. The second is TLC-in-site detection directly with special MS ion source devices like fast-atom-bombardment desorption ionization, matrix-assisted laser desorption ionization, surface-assisted laser desorption ionization, electrospray-assisted laser desorption ionization, laser-induced acoustic desorption/electrospray ionization, electrostatic-spray ionization, easy ambient sonic-spray ionization, desorption sonic spray ionization, ionization using "desorption/ionization resource", ionization using "molecular ionization-desorption analysis source", multiwavelength laser desorption ionization, ionization using flowing afterglow-atmospheric pressure glow discharge, ionization low-temperature plasma probe, desorption/ionization induced using neutral clusters, ionization using inductively coupled plasma and so on. These MS analyses are performed after TLC development, thus, the relative position of the chromatographic bands on TLCs is invariable, and this analysis can be regarded as static detection, though flexible travel stages or conveyor belts can be introduced to move TLC plates. The third strategy is to monitor TLC run using MS in real-time just as the monitor employed in HPLC, in which the chromatographic bands are still moving. This strategy is generally run on forced-flow TLC techniques and is less examined. The typical coupling technologies (especially appeared in recent ten years) are summarized and briefly described in this study. TLC-MS has greatly enhanced the research efficiency of bioactive substances for food and drugs due to the widespread usage of TLC-bioautography technology. Nowadays, the main bottleneck in the development of TLC-MS is the design and commercialization of "plug and play" components. The high-throughput and real-time monitoring TLC-MS technology with flexible scanning functions is also expected. Furthermore, the comparative studies of different kinds of desorbing-ionizing technologies are also application problems for further discussion.

A mass spectral library of 18 mycotoxins was developed based on ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS), which was used to establish a non-targeted screening method for mycotoxins in rice and wheat matrices. Eighteen mycotoxin standards were separated on an HSS T3 column, and data were collected for both positive and negative ionization under the MS^E mode of the UPLC-Q-TOF/MS. Details including formulas, retention times, theoretical exact masses, measured exact masses of the adduct and fragment ions, and ion abundance ratios were recorded to establish the mass spectral library of the 18 mycotoxins in UNIFI Software. Analyte detection was based on a retention time deviation of 0.3 min, and the exact mass deviation of the adduct ions and fragment ions was set to 5×10^-6. The screening detection limit (SDL) was used as the main threshold for verifying the screening method. In the validation process, 18 mycotoxins were classified into two types: with maximum levels (MLs) and without MLs. The results showed that the mycotoxins with MLs could be accurately screened at their limited level, and the mycotoxins without MLs had a range of SDL concentration from 2 to 800 μg/kg. The matrix effect results showed that 14 mycotoxins in rice and 11 in wheat had moderate matrix effects. Finally, 25 batches of rice and wheat were purified using QuEChERS and HLB columns after acetonitrile extraction and screening were performed by employing the established method. The results revealed that aflatoxin G₁ (AFG₁), aflatoxin G₂ (AFG₂), fumonisins B₁ (FB₁), and sterigmatocystin (ST) were detected in one batch of rice, FB₁ and ST were detected in another batch of rice, FB₁ and ochratoxin A (OTA) were detected in two batches of wheat, and no other mycotoxins were detected. This method is characterized by high throughput, simplicity, rapidity, accuracy, and can be applied to accurately screen mycotoxins with concentrations higher than the SDLs and qualitatively screen various mycotoxins in rice and wheat without standards.

With the increasing number of cosmetic products, their flavor and fragrance components are receiving greater and greater attention. Establishing an analytical method of determining these components in cosmetics is one of the most effective measures to eliminate consumers' concerns. In this study, a method for the simultaneous determination of 28 fragrance residues in cosmetics by gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed. The samples were extracted using methanol and those containing more oil and grease were purified using a neutral alumina solid-phase extraction column, whereas those with more complex compositions were purified by QuEChERS. The analytes in the samples were measured by GC-MS/MS, characterized using their retention times and characteristic ion pairs, and quantified with an external standard. The respective limits of detection (LODs, S/N=3) and quantification (LOQs, S/N>10) of the compounds were in the ranges 2-20 and 5-50 μg/kg. The linearities of the concentration curves of the 28 substances were good in the ranges 1-100, 2-200, 4-200, and 10-1000 μg/L, and the correlation coefficients of the quantitative ion pairs were >0.999. Twenty-eight fragrances were added to blank samples at spiked levels of 50-500 μg/kg, and the recoveries ranged from 71.3% to 120.4%, with RSDs of 1.5%-14.6%. The method could be applied in the determination of fragrances in cosmetics because it was simple, sensitive, and stable and could effectively exclude the interferences of complex matrices. The method was used to determine the fragrance components in 16 cosmetic products, and some fragrance components were detected in 12 samples. Increased attention should be paid to the safeties of fragrances and flavors used in cosmetics.

Since Nobel Laureate K. B. Sharpless first introduced the concept of click chemistry in 2001, such reactions have become a powerful modular synthesis tool. Click chemistry reactions have rapidly expanded into many scientific fields, such as materials and life science, owing to their distinct advantages, which include mild conditions, fast reaction rates, high yields, low by-product generation, and simple separation and purification procedures. Nowadays, click chemistry reactions have become an essential means of designing and preparing separation materials; thus, interest in this synthetic technique has quickly grown. Here, the development of click chemistry and its unique advantages are briefly described firstly. The reports on click chemistry-based chromatographic separation materials published in the past five years are then systematically reviewed, focusing on two major separation fields: column chromatography and membrane chromatography. Meanwhile, recent advances in the separation materials obtained from three common types of click reactions, namely, azido-alkyne, thiol-alkene, and thiol-alkyne, are summarized. Finally, an outlook on the future of click chemistry is provided in developing efficient chromatographic separation materials.