Determination of procymidone residues in ginseng by GC–ECD and GC–MS equipped with a solvent-free solid injector

A novel electrochemical aptasensor based on AgPdNPs/PEI-GO and hollow nanobox-like Pt@Ni-CoHNBs for procymidone detection

Herein, an aptasensor based on a signal amplification strategy was developed for the sensitive detection of procymidone (PCM). AgPd nanoparticles/Polenimine Graphite oxide (AgPdNPs/PEI-GO) was weaned as electrode modification material to facilitate electron transport and increase the active sites on the electrode surface. Besides, Pt@Ni-Co nanoboxes (Pt@Ni-CoHNBs) were utilized to be carriers for signaling tags, after hollowing ZIF-67 and growing Pt, the resulting Pt@Ni-CoHNBs has a tremendous amounts of folds occurred on the surface, enables it to carry a larger quantity of thionine, thus amplify the detectable electrochemical signal. In the presence of PCM, the binding of PCM to the signal probe would trigger a change in electrical signal. The aptasensor was demonstrated with excellent sensitivity and a low detection limit of 0.98 pg·mL-1, along with a wide linear range of 1 μg·mL-1 to 1 pg·mL-1. Meanwhile, the specificity, stability and reproducibility of the constructed aptasensor were proved to be satisfactory.

The effect of chlorophyll on the enzyme-linked immunosorbent assay (ELISA) of procymidone in vegetables and the way to overcome the matrix interference

BACKGROUND

There is now an increasing demand for the immunoassay of procymidone residue in foodstuffs. However, the matrix interference could significantly affect the analysis. Till now there is no detailed information on the source of the interference and the mechanism involved, which greatly limits the real application of these techniques.

RESULTS

Significant matrix effect was observed in the enzyme-linked immunosorbent assay (ELISA) of procymidone in negative vegetable samples (leek, broccoli and cucumber). By the investigation with both vegetable extracts and standard solutions, the chlorophyll was confirmed as an important source of the matrix effect. Therefore, a new strategy was proposed for the pretreatment based on the exploitation of 5-sulfosalicylic acid. It was demonstrated to effectively eliminate chlorophyll and exhibited little effect on procymidone and the competitive indirect ELISA (ci-ELISA) performance. The established technique was validated with different vegetables. With the spiking concentration of procymidone investigated, the recovery rate of ci-ELISA was 71.52-120.37%, and the relative standard deviation was 4.05-17.61%.

CONCLUSION

Chlorophyll was for the first time illuminated as an important source of matrix interference to the immunoassay of procymidone in vegetables. A new pretreatment based on 5-sulfosalicylic acid was established to remove chlorophyll and therefore eliminate the matrix effect. Validated with different vegetable samples, the new technique was demonstrated much better efficiency in comparison to conventional methods, which indicated its promising application for the development of immunoassays of herb-origin samples. © 2021 Society of Chemical Industry.

Application of a solvent-free solid injection technique coupled with GC-MS for discrimination between the secondary metabolites of wild and cultivated South Korean medicinal foods

Solvent-free solid injection was applied to differentiate between wild and cultivated South Korean medicinal foods, including dureup (Aralia elata), deodeok (Codonopsis lanceolata) and doraji (Platycodon grandiflorus). A number of compounds were identified in wild and cultivated dureup (53 and 46), deodeok (47 and 51) and doraji (43 and 38). Secondary metabolites, including butanal,2-methyl-, β-caryophyllene, neoclovene, α-humulene, γ-curcumene, β-bisabolene, and phytol, were identified in dureup with significantly (P < 0.05) different amounts between both types. In deodeok, squalene and other main components such as acetic acid, methyl ester, furan-methyl-furfural, 2-furan-methanol, and 5-methyl-furfural, were statistically different between the two types. Doraji has significantly different compounds such as furfural, 5-methyl-furfural, 2-methoxy-phenol, 2-methoxy-4-(1-propenyl)-phenol, and 1-(4-hydroxy-3-methoxyphenyl)-2-propanone. Although we failed to confirm the key compounds, a new compound, namely desaspidinol, was synthesized for the first time and its retention index determined under the experimental conditions. This solventless, easy technique can be used as a simple way to discriminate between wild and cultivated types of medicinal plants via identification of volatile markers or specific fingerprints.

Qualitative and quantitative analysis on aroma characteristics of ginseng at different ages using E-nose and GC-MS combined with chemometrics

Aroma profiles of ginseng samples at different ages were investigated using electronic nose (E-nose) and GC-MS techniques combined with chemometrics analysis. The bioactive ginsenoside and volatile oil content increased with age. E-nose performed well in the qualitative analyses. Both Principal Component Analysis (PCA) and Discriminant Functions Analysis (DFA) performed well when used to analyze ginseng samples, with the first two principal components (PCs) explaining 85.51% and the first two factors explaining 95.51% of the variations. Hierarchical Cluster Analysis (HCA) successfully clustered the different types of ginsengs into four groups. A total of 91 volatile constituents were identified. 50 of them were calculated and compared using GC-MS. The main fragrance ingredients were terpenes and alcohols, followed by aromatics and ester. The changes in terpenes, alcohols, aromatics, esters, and acids during the growth year once again confirmed the dominant role of terpenes. The Partial Least Squares (PLS) loading plot of gas sensors and aroma ingredients indicated that particular sensors were closely related to terpenes. The scores plot indicated that terpenes and its corresponding sensors contributed the most in grouping. As regards to quantitative analyze, 7 constituent of terpenes could be accurately explained and predicted by using gas sensors in PLS models. In predicting ginseng age using Back Propagation-Artificial Neural Networks (BP-ANN), E-nose data was found to predict more accurately than GC-MS data. E-nose measurement may be a potential method for determining ginseng age. The combination of GC-MS can help explain the hidden correlation between sensors and fragrance ingredients from two different viewpoints.

Determination of volatile organic compounds generated from fresh, white and red Panax ginseng (C. A. Meyer) using a direct sample injection technique

Ginsenosides are regarded as the main active, non-volatile components of Panax ginseng (C. A. Meyer). However, throughout the long history of ginseng research, there has been virtually no report describing its volatile flavor compounds. A solvent-free procedure for the determination of volatile flavor compounds generated from fresh, white and red Panax ginseng (C. A. Meyer) using solvent-free solid injection (SFSI) coupled with gas chromatography-mass spectrometry (GC-MS) detection is described here. At no point in the SFSI technique were the extraction conditions optimized. Rather, the experimental variables including various sample preparations (fresh, oven-dried and freeze-dried), injector temperatures (100, 150, 200, 250 and 300 degrees C), and preheating times (3, 5, 7, 10 and 15 min), were predicated on the experience of the authors. A total of 47 compounds were identified in various forms of ginseng. Among the compounds identified in the sample, fresh ginseng was characterized by a high proportion of 3-acetyl-1-(3,4-dimethoxyphenyl)-5-ethyl-4,5-dihydro-7,8-dimethoxy-4-methylene-3H-2,3-benzodiazepine (64.24%) and 23,24-dinor-3-oxolean-4,12-dien-28-oic acid (21.42%); 2-furanmethanol (20.26%) and 3-hydroxy-2-methyl-4H-pyran-4-one (17.95%) were detected as the major components in white ginseng while the main components of the red ginseng were found to be 1,2-benzenedicarboxylic acid dibutyl ester (16.27%) and 2-furanmethanol (13.82%). SFSI is a solvent-free, rapid and simple sample preparation technique based on direct vaporization. There is no dilution or contamination with solvent or its impurities and no loss of quickly eluted components was observed in the solvent peak.

Analysis of volatile compounds in fresh healthy and diseased peppers (Capsicum annuum L.) using solvent free solid injection coupled with gas chromatography-flame ionization detector and confirmation with mass spectrometry

The characteristic volatile flavor compounds in healthy peppers (Capsicum annuum L.) were evaluated using a solvent-free solid injector coupled with a-gas chromatography-flame ionization detector (SFSI-GC-FID) and the results of evaluation were confirmed using GC-mass spectrometry (GC-MS). These compounds were compared with those obtained from peppers that were naturally infected or artificially inoculated with Colletotrichum spp. Parameters influencing the vaporization efficiency, including the injector temperature, pre-heating time and holding time, were optimized to improve the analytical efficiency. A total of 96 compounds (excluding eight capillary compounds), 17 of which were identified in healthy peppers, 49 of which were found in naturally infected peppers, and 61 of which were identified in artificially inoculated peppers, were separated and identified under the optimal conditions of an injector temperature of 250 degrees C and 7-min preheating and holding times. Acetic acid and 2-furanmethanol were the major compounds detected in the volatiles of the healthy and diseased peppers. The major compound detected in both the healthy and naturally infected peppers was 3-hydroxypyridine, while hexadecanoic acid was the primary compound identified in the artificially inoculated peppers. Indole derivatives (1H-indole, 4-methylindole and 1-ethylindole) were suggested to be the key factors contributing to the pepper infection caused by Colletotrichum spp. We conclude that SFSI in combination with GC is a suitable approach for distinguishing between healthy and diseased peppers by the investigation of their volatile compounds. It does not require the use of solvents and complicated equipment.