[Trapping array-based preparative two-dimensional liquid chromatography for the purification of four components in tobacco leaves].

Two-dimensional liquid chromatography (2D-LC) has gained increased attention because of its high peak capacity for separating complex samples. However, preparative 2D-LC aimed at isolating compounds is significantly different compared with one-dimensional liquid chromatography (1D-LC) in terms of method development and system configuration; thus, it is less developed than its analytical counterpart. The use of 2D-LC in large-scale product preparation has rarely been reported. Hence, a preparative 2D-LC system was developed in this study. The system was composed of one set of preparative LC modules as a separation system, with a dilution pump, switch valves, and trap column array as the interface, to enable the simultaneous isolation of several compounds. Tobacco was used as a sample, and the developed system was applied to isolate nicotine, chlorogenic acid, rutin, and solanesol. The chromatographic conditions were developed by investigating the trapping efficiency of different types of trap column packings, and chromatographic behaviors under different overload conditions. The four compounds were isolated in one 2D-LC run with high purity. The developed system features low cost because it employs medium-pressure isolation, excellent automation owing to its use of an online column switch, high stability, and capability for large-scale production. The isolation of chemicals from tobacco leaves as pharmaceutical raw materials could aid in the development of the tobacco industry and promote the local agricultural economy.

[Bacterial Diversity and Community Structure Antibiotic-resistant Bacteria in Bioaerosol of Animal Farms].

Confined animal feeding operations generate high concentrations of airborne antibiotic-resistant bacteria, including pathogenic strains that may pose a health risk to both animals and farm workers and pollute the local air environment. In this study, tetracycline and erythromycin-resistant bacteria were used as examples to study the biodiversity and community structure of airborne antibiotic-resistant bacteria in animal farms. The Anderson sampler was used to collect bioaerosols samples from the inside environment and outside atmospheric environments. A comparative analysis of biological differences of antibiotic-resistant bacteria was conducted on fine and coarse particles, bioaerosol samples inside the house, fecal samples, and inside and outside bioaerosol samples based on the result of the Illumina MiSeq sequencing. The key genus that drives the above differences was also studied. Results showed that the biodiversity of airborne erythromycin-resistant bacteria was higher than that of airborne tetracycline-resistant bacteria, and the biodiversity of bioaerosol samples in the house was higher than that in fecal samples. There were no significant differences in the biodiversity and community structure of airborne antibiotic-resistant bacteria between fine and coarse particles. Actinobacteria is one of the key bacteria responsible for the differences between erythromycin-resistant bacteria and other bacterial populations. Staphylococcus is one of the key genera of tetracycline-resistant flora that is distinguished from erythromycin resistance and all bacterial flora. The results of the community structure showed that there was no significant difference in the dominant flora and the community structure of tetracycline and erythromycin-resistant bacteria. The community structure of feces and bioaerosol samples is different at the genus level, and the dominant bacteria are likewise different. The results of this study provide basic data for the accurate assessment of the current status of antibiotic-resistant bacteria in animal farms and their ecological risks.

Separation and Analysis of Sucrose Esters in Tobacco by Online Liquid Chromatography-Gas Chromatography/Mass Spectrometry.

In this work, a strategy of in-series combination of ultrasound-assisted extraction and online LC-GC/MS was constructed for effective separation and analysis of sucrose esters in tobacco. Sucrose esters were first extracted by ultrasound-assisted extraction with high efficiency and easyhandling. Online LC-GC/MS was then applied for sucrose ester clean-up and analysis. To better evaluate the effectiveness of this strategy, we limited our focus to five groups of sucrose ester isomers. Each group differed in mass from the next by 14 Da. The obtained coefficient of the calibration curve was 0.9986. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.05 and 0.16 µg/ mL, respectively. The recovery was above 90% and the reproducibility was below 4%. This strategy was subsequently applied to the comparison of relative amounts of five groups of sucrose esters extracted from three different parts of aromatic tobacco. The satisfactory performance indicated that this strategy has great prospect for the rapid and high-throughput analysis of sucrose esters in tobacco.