Effects of ion source operating parameters on direct analysis in real time of 18 active components from traditional Chinese medicine

Recent application of direct analysis in real time mass spectrometry in plant materials analysis with emphasis on traditional Chinese herbal medicine

Direct analysis in real time (DART) represents a new generation of ionization techniques that are used to rapidly ionize small molecules under ambient environments. The combination of DART with various mass spectrometry (MS) instruments allows analyzing multiple plant materials, including traditional Chinese herbal medicines (TCHMs), under simple or no sample treatment conditions. This review discussed the DART principles, including devices, ionization mechanisms, and operation parameters. Typical spectra detected by DART-MS were exhibited and discussed. Numerous applications of DART-MS in the fields of plant material and TCHM analysis were reviewed, including compound identification, biomarker discovery, fingerprinting analysis, and quantification analysis. Besides, modifications and improvements of DART-MS, such as hyphenated application with other separation methods, laser-based desorption techniques, and online sampling configuration, were summarized as well.

Metabolite Fingerprinting for Identification of Panax ginseng Metabolites Using Internal Extractive Electrospray Ionization Mass Spectrometry

Ginseng, a kind of functional food and medicine with high nutritional value, contains various pharmacological metabolites that influence human metabolic functions. Therefore, it is very important to analyze the composition and metabolites of ginseng. However, the analysis of active metabolites in ginseng samples usually involves various experimental steps, such as extraction, chromatographic separation, and characterization, which may be time-consuming and laborious. In this study, an internal extractive electrospray ionization mass spectrometry (iEESI-MS) method was developed to analyze active metabolites in ginseng samples with sequential sampling and no pretreatment. A total of 44 metabolites, with 32 ginsenosides, 6 sugars, and 6 organic acids, were identified in the ginseng samples. The orthogonal partial least-squares discriminant analysis (OPLS-DA) score plot showed a clear separation of ginseng samples from different origins, indicating that metabolic changes occurred under different growing conditions. This study demonstrated that different cultivation conditions of ginseng can be successfully discriminated when using iEESI-MS-based metabolite fingerprints, which provide an alternative solution for the quality identification of plant drugs.

Characterization of effective phytochemicals in traditional Chinese medicine by mass spectrometry

Traditional Chinese medicines (TCMs) have been widely used in clinical and healthcare applications around the world. The characterization of the phytochemical components in TCMs is very important for studying the therapeutic mechanism of TCMs. In the analysis process, sample preparation and instrument analysis are key steps to improve analysis performance and accuracy. In recent years, chromatography combined with mass spectrometry (MS) has been widely used for the separation and detection of trace components in complex TCM samples. This article reviews various sample preparation techniques and chromatography-MS techniques, including the application of gas chromatography-MS and liquid chromatography-MS and other MS techniques in the characterization of phytochemicals in TCM materials and Chinese medicine products. This article also describes a new ambient ionization MS method for rapid and high-throughput analysis of TCM components.

Direct Analysis in Real-time Mass Spectrometry for Rapid Identification of Traditional Chinese Medicines with Coumarins as Primary Characteristics

INTRODUCTION

The increasing popularity of traditional Chinese medicines (TCMs) necessitates rapid and reliable methods for controlling their quality. Direct analysis in real-time mass spectrometry (DART-MS) represents a novel approach to analysing TCMs.

OBJECTIVE

To develop a quick and reliable method of identifying TCMs with coumarins as primary characteristics.

METHODOLOGY

DART-MS coupled with ion trap mass spectrometry was employed to rapidly identify TCMs with coumarins as primary characteristics and to explore the ionisation mechanisms of simple coumarins, furocoumarins and pyranocoumarins in detail. With minimal sample pretreatment, mass spectra of Fraxini Cortex, Angelicae Pubescentis Radix, Peucedani Radix and Psoraleae Fructus samples were obtained within seconds. The operating parameters of the DART ion source (e.g. grid electrode voltage and ionisation gas temperature) were carefully investigated to obtain high-quality mass spectra. The mass spectra of samples and DART-MS/MS spectra of marker compounds were used to identify sample materials.

RESULTS

Successful authentication was achieved by analysing the same materials of different origins. Some simple coumarins, furocoumarins and pyranocoumarins can be directly detected by DART-MS as marker compounds.

CONCLUSION

Our results demonstrated that DART-MS can provide a rapid and reliable method for the identification of TCMs containing different configurations of coumarins; the method may also be applicable to other plants. Copyright © 2016 John Wiley & Sons, Ltd.

Observed adducts on positive mode direct analysis in real time mass spectrometry - Proton/ammonium adduct selectivities of 600-sample in-house chemical library

In this study, direct analysis in real time adduct selectivities of a 558 in-house high-resolution mass spectrometry sample library was evaluated. The protonated molecular ion ([M + H]⁺) was detected in 462 samples. The ammonium adduct ion ([M + NH₄]⁺) was also detected in 262 samples. [M + H]⁺ and [M + NH₄]⁺ molecular ions were observed simultaneously in 166 samples. These adduct selectivities were related to the elemental compositions of the sample compounds. [M + NH₄]⁺ selectivity correlated with the number of oxygen atom(s), whereas [M + H]⁺ selectivity correlated with the number of nitrogen atom(s) in the elemental compositions. For compounds including a nitrogen atom and an oxygen atom [M + H]⁺ was detected; [M + NH₄]⁺ was detected for compounds including an oxygen atom only. Density functional theory calculations were performed for selected library samples and model compounds. Energy differences were observed between compounds detected as [M + H]⁺ and [M + NH₄]⁺, and between compounds including a nitrogen atom and an oxygen atom in their elemental compositions. The results suggested that the presence of oxygen atoms stabilizes [M + NH₄]⁺, but not every oxygen atom has enough energy for detection of [M + NH₄]⁺. It was concluded that the nitrogen atom(s) and oxygen atom(s) in the elemental compositions play important roles in the adduct formation in direct analysis in real time mass spectrometry.

Ionization characteristics of glycosides by direct analysis in real time quadrupole-time of flight mass spectrometry

Glycosides were ionized via various different reactions including (de)protonation, molecular ion formation, ISD fragmentation, and the formation of adducts.