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Plant hormone determination in food matrices has attracted more and more attention because of their potential risks to human health. However, analytical methods for the analysis of multiple plant hormones remain poorly investigated. In the present study, a convenient, selective, and ultrasensitive high-performance liquid chromatography method for the simultaneous determination of multiple classes of plant hormones has been developed successfully using dispersive liquid-liquid microextraction followed by precolumn fluorescent labeling. Eight plant hormones in fruits including jasmonic acid, 12-oxo-phytodienoic acid, indole-3-acetic acid, 3-indolybutyric acid, 3-indolepropionic acid, gibberellin A₃, 1-naphthylacetic acid, and 2-naphthaleneacetic acid were analyzed by this method. The conditions employed for dispersive liquid-liquid microextraction were optimized systematically. The linearity for all plant hormones was found to be >0.9993 (<i>R</i>² values). This method offered low detection limits of 0.19-0.44 ng/mL (at a signal-to-noise ratio of 3), and method accuracies were in the range of 92.32-103.10%. The proposed method was applied to determine plant hormones in five kinds of food samples, and this method can achieve a short analysis time, low threshold levels of detection, and a high specificity for the analysis of targeted plant hormones present at trace level concentrations in complex matrices.

A simple, sensitive and selective method based on one-step fluorescence labeling and ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) was developed for the determination of biogenic amines (BAs) in foodstuff samples by high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). In this work, fluorescence probe 2-(11H-benzo[a]carbazol-11-yl) ethyl carbonochloridate (BCEC-Cl) was applied to label BAs. What followed was the UA-DLLME procedure that was carried out using chloroform and acetone as extraction and disperser solvents, respectively. A response surface methodology (RSM) based on a Box-Behnken design (BBD) was employed to optimize the main parameters affecting the fluorescence labeling and DLLME efficiency. Under the optimal conditions, this method offered low limits of detection (LODs) of 1.1-7.8 ng/mL and limits of quantification (LOQs) of 3.5-26.1 ng/mL. Finally, the method was successfully used for the determination of trace BAs in real samples and exhibited powerful potential in the high-throughput sample screening.

<br>• A DLLME/HPLC-FLD method for triterpenic acid determination was developed. • DLLME was firstly used for preconcentration of triterpenic acids in medicinal herbs. • This method was sensitive and selective for triterpenic acid analysis. • A new derivatization reagent for triterpenic acid has been synthesized.<br>A novel analytical method was developed for simultaneous determination of six triterpenic acids using ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) follow by high-performance liquid chromatography (HPLC) with fluorescence detection. Six triterpenic acids (ursolic acid, oleanolic acid, betulinic acid, maslinic acid, betulonic acid and corosolic acid) were extracted by UA-DLLME using chloroform and acetone as the extraction and disperser solvents, respectively. After the extraction and nitrogen flushing, the extracts were rapidly derivatized with 2-(12,13-dihydro-7H-dibenzo[a,g]carbazol-7-yl)ethyl4-methylbenzenesulfonate. The main experimental parameters affecting extraction efficiency and derivatization yield were investigated and optimized by response surface methodology (RSM) combined with Box-Behnken design (BBD). The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.95-1.36 ng mL−1 and 3.17-4.55 ng mL−1, respectively. Under the optimum conditions, the method has been successfully applied for the analysis of triterpenic acids in six different traditional Chinese medicinal herbs.

A sensitive and inexpensive method involving ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) and pre-column derivatization followed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) was developed for the analysis of glycyrrhetinic acid. In this work, glycyrrhetinic acid could be obtained by hydrolyzing glycyrrhizic acid to remove glucuronic acid and subsequently extracted by UA-DLLME using chloroform and acetone as the extraction and disperser solvents, respectively. The sample extraction was firstly concentrated to dry under nitrogen and then rapidly derivatized with 2-(12-oxobenzo[b]acridin-5(12H)-yl)-ethyl-4-toluenesulfonate (BAETS) after the UA-DLLME. The prime parameters influencing the UA-DLLME and derivatization procedure were optimized using response surface methodology. Under the optimum conditions, the proposed method has a better linearity in a wider range of 6-300 ng mL<sup>−1</sup> and a high square of correlation coefficient (<i>R</i> <sup>2</sup>) at 0.9994. Limit of detection and limit of quantification were found to be 1.7 ng mL<sup>−1</sup> and 5.8 ng mL<sup>−1</sup>, respectively. The proposed method was applied to the analysis of glycyrrhetinic acid in liquorice, liquorice apricot and sugar plum samples. For the analysis of the spiked samples, the spiked recoveries were in the range of 90.4-103.0 % with RSD less than 5.18 %. All results demonstrated that the UA-DLLME-HPLC-FLD (ultrasound-assisted dispersive liquid-liquid microextraction-high-performance liquid chromatography with fluorescence detection) was a sensitive, accurate, efficient analytical method for the determination of glycyrrhetinic acid.