Taxonomic Identification of Commercial Boswellia spp. Resins by Ambient Ionization Mass Spectrometry

International trade of several Dalbergia wood species is regulated by The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In order to supplement morphological identification of these species, a rapid chemical method of analysis was developed. Using Direct Analysis in Real Time (DART) ionization coupled with Time-of-Flight (TOF) Mass Spectrometry (MS), selected Dalbergia and common trade species were analyzed. Each of the 13 wood species was classified using principal component analysis and linear discriminant analysis (LDA). These statistical data clusters served as reliable anchors for species identification of unknowns. Analysis of 20 or more samples from the 13 species studied in this research indicates that the DART-TOFMS results are reproducible. Statistical analysis of the most abundant ions gave good classifications that were useful for identifying unknown wood samples. DART-TOFMS and LDA analysis of 13 species of selected timber samples and the statistical classification allowed for the correct assignment of unknown wood samples. This method is rapid and can be useful when anatomical identification is difficult but needed in order to support CITES enforcement. Published 2012. This article is a US Government work and is in the public domain in the USA.

Comprehensive comparison of ambient mass spectrometry with desorption electrospray ionization and direct analysis in real time for direct sample analysis

Pterocarpus santalinus and Pterocarpus tinctorius are commonly used species of the genus Pterocarpus in the wood trade. Although both of them have been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) since 2019, it is still critical to identify them in terms of plant taxonomy. Currently, high-temperature heating is an accepted treatment method for high-density wood species such as Pterocarpus to improve dimensional stability and restore previous drying defects partially. It has proved challenging to identify the high-temperature (e.g., 120 °C) heated wood from these two species. Thus, this study approaches species identification of two Pterocarpus of high-temperature (e.g., 120 °C) heated solid wood samples using headspace–gas chromatography–mass spectrometry (HS–GC–MS). Besides, a computational analytical method named similarity network fusion (SNF) was proposed to aggregate data in two different types, respectively, derived from the HS–GC–MS and direct analysis in real time–mass spectrometry (DART–MS) to explore the feasibility of improving the efficiency and accuracy of wood species discrimination. The SNF exhibits more significant differences and higher predictive accuracy (100%) between P. santalinus and P. tinctorius than that based on the HS–GC–MS data (77.78%) or DART–MS (66.67%) alone. These results demonstrated the capability of the HS–GC–MS technique in the analysis of high-temperature heated solid wood and the potential of multidimensional or comprehensive data sets based on the SNF algorithm in the field of wood species identification.

Illegal logging is a serious global issue. It is not only a great threat to rare forest species, but also contributes to the current biodiversity crisis and climate change. Despite international agreements, 10-30% of all imported wood has been illegally logged. Many of these trees, especially rosewood (Dalbergia) and ebony (Diospyros), are very important for the global market because of their high economic value. Ebony is a common name for the black heartwood (inner parts of the stem) of some Diospyros species. These woods are used in products such as acoustic musical instruments. The genus Diospyros includes over 700 species globally. More than 200 of them are endemic to Madagascar, which is a one of the richest regions in terms of biodiversity. This island is situated in the Indian Ocean off the coast of Eastern Africa and is known for its unique biodiversity. Due to over-harvesting in recent decades, many Malagasy species of Diospyros are listed as endangered under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES; CITES checklist for Diospyros). Trade of these species requires CITES permits. All described Malagasy ebony species under Appendix II meaning that, while not currently threatened with extinction they may become so if trade is not controlled. Controlling the logging trade is often more difficult than it seems. Labels are easily switched, different species of wood can be mixed, permits can be falsified, and many more tricks are used to get illegally logged wood onto the global market. One of the most commonly used techniques to identify timber products is the assessment of species-specific cellular patterns (White et al. 1991). Wood anatomy has been practiced for more than 200 years, and automated tools have been developed to identify wood at the genus and species level over the past decade (Figueroa-Mata et al. 2018, Hafemann et al. 2014, Koch et al. 2011, Ravindran et al. 2018). However, the lack of sufficient resolution for species-level identification, especially for speciose genera such as Diospyros, is the main drawback of this method. Identification using molecular barcoding is an alternative but challenging method as timber is composed mainly of dead cells and the few living cells often have poor DNA quality. A third identification method is direct analysis in real time time-of-flight mass spectrometry (DART TOF MS; Espinoza et al. 2015, Evans et al. 2017). This method analyses the chemical composition of a wood sample, resulting in a species-specific chemical fingerprint. DART TOF MS has already been successfully applied to several tree genera including Dalbergia (rosewood), Aquilaria (agarwood), and Quercus (oak). The main disadvantage of this method is that it can only be applied to heartwood samples from the inner part of the trunk. In order to develop a comprehensive and accurate identification tool to identify Malagasy ebony woods, we are working towards building an image recognition model based on wood anatomical microscopic images. As a case study, we successfully trained our classifier using a public dataset (Martins et al. 2012) such that our model was able to distinguish different tree genera of that dataset with 93% accuracy. We are currently extending this work to the subgeneric level of Diospyros. This will be used to establish the presence of ebony woods in acoustic musical instruments based on reference samples from wood specimens preserved in natural history musea. To achieve sufficient accuracy, we are focusing on the microscopic features of transverse and tangential orientation planes in ebony woods. Our database will include very high resolution images of Diospyros species, and can help wood anatomist at wood identification institute and customs officers at harbours to increase the accuracy of the identification of illegally logged ebony woods.

We have developed an efficient, sensitive, and specific method for the detection of phosphopeptides present in peptide mixtures by MALDI Q-TOF mass spectrometry. Use of the MALDI Q-TOF enables selection of phosphopeptides and characterization by CID of the phosphopeptides performed on the same sample spot. However, this type of experiment has been limited by low ionization efficiency of phosphopeptides in positive ion mode while selecting precursor ions of phosphopeptides. Our method entails neutralizing negative charges on acidic groups of nonphosphorylated peptides by methyl esterification before mass spectrometry in positive and negative ion modes. Methyl esterification significantly increases the relative signal intensity generated by phosphopeptides in negative ion mode compared with positive ion mode and greatly increases selectivity for phosphopeptides by suppressing the signal intensity generated by acidic peptides in negative ion mode. We used the method to identify 12 phosphopeptides containing 22 phosphorylation sites from low femtomolar amounts of a tryptic digest of beta-casein and alpha-s-casein. We also identified 10 phosphopeptides containing five phosphorylation sites from an in-gel tryptic digest of 100 fmol of an in vitro autophosphorylated fibroblast growth factor receptor kinase domain and an additional phosphopeptide containing another phosphorylation site when 500 fmol of the digest was examined. The results demonstrate that the method is a fast, robust, and sensitive means of characterizing phosphopeptides present in low abundance mixtures of phosphorylated and nonphosphorylated peptides.

Direct Analysis in Real Time (DART) Mass Spectrometry of Nucleotides and Nucleosides: Elucidation of a Novel Fragment [C 5H 5O] + and Its In-Source Adducts

A comparison between DART-MS and DSA-MS in the forensic analysis of writing inks

Here we report a rapid approach for qualitative analysis of iridoid glycosides and caffeoylquinic acids (CQAs) in Re Du Ning Injections using a Direct Analysis in Real Time (DART) ionization source coupled with quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). In this approach, DART/MS and DART MS/MS analyses in both negative and positive ion modes were performed to characterize two iridoid glycosides and six CQAs in reference solutions and Re Du Ning Injections. Fragmentation pathways of two kinds of natural compounds were summarized. DART-MS tended to break down some labile bonds in di-CQAs. The di-CQAs yielded abundant fragment ions in the (−) mass scan spectra. Collision-induced dissociation techniques were used to fragment the precursor ions and the product ions. Moreover, differentiation of the isomers of CQAs was possible by using the relative peak abundance and characteristic ion species in MS/MS spectra. DART-MS was also employed to obtain a chemical fingerprint of Re Du Ning Injections for rapid qualitative analysis of this Chinese medicine preparation. DART/Q-TOF MS/MS has shown potential to be used as the real-time detection method for Re Du Ning Injections.

Prediction of acrylamide formation in biscuits based on fingerprint data generated by ambient ionization mass spectrometry employing direct analysis in real time (DART) ion source

Polymers are ubiquitous, and characterisation of their chemical, thermal and mechanical properties is important in many applications. Hot-stage microscopy Direct Analysis in Real Time mass spectrometry (HDM) is a new technique which combines optical measurements with the benefits of ambient ionisation mass spectrometry. Physical and chemical information can be obtained as a function of sample temperature, in real time. Samples were placed on a miniaturised hot-stage between a custom-made Direct Analysis in Real Time (DART) source and the inlet of an ion trap mass spectrometer, and subjected to both linear and cycled temperature programmes. Optical images were collected using a digital microscope and mass spectra (positive and negative ion) were recorded simultaneously. Mass spectra and optical images were used to monitor the thermal expansion and release of volatile oligomers from both medical and domestic grades of silicone. Series of ions separated by 74m/z units were observed, consistent with the SiOMe2 monomer; the median mass of these increased with increasing temperature up to the decomposition point (340-400°C). The abundance of volatile material produced decreased with repeated thermal cycling. The coefficients of thermal expansion were calculated from optical data and were in agreement with conventional measurements (2.7-3.6 × 10-4 °C-1 ). Two samples of beach sand analysed for the presence of microplastics were found to contain polyethylene and polystyrene, respectively. Results indicate that the novel technique of HDM can be successfully applied to the characterisation of a wide range of polymers including those in complex matrices.

Ambient ionization mass spectrometry methods are convenient, sensitive and require little sample preparation. However, they are susceptible to species present in air surrounding the mass spectrometer. This study identifies some challenges associated with the potential impacts of indoor air contaminants on ionization and analysis involving open-air methods. Unexpected effects of volatile organic compounds (VOCs) from floor maintenance activities on ambient ionization mass spectrometry were studied using three different ambient ionization techniques. Extractive electrospray ionization (EESI), direct analysis in real time (DART) and ionization by piezoelectric direct discharge (PDD) plasma were demonstrated in this study to be affected by indoor air contaminants. Identification of contaminant vapors was verified by comparison with standards using EESI-MS/MS product ion scans. Emissions of diethylene glycol monoethyl ether and ethylene glycol monobutyl ether are identified from floor stripping and waxing solutions using three ambient ionization mass spectrometry techniques. These unexpected indoor air contaminants are capable of more than 75% ion suppression of target analytes due to their high volatility, proton affinity and solubility compared with the target analytes. The contaminant vapors are also shown to form adducts with one of the target analytes. The common practice in MS analysis of subtracting a background air spectrum may not be appropriate if the presence of ionizable air contaminants alters the spectrum in unexpected ways. For example, VOCs released into air from floor stripping and waxing are capable of causing ion suppression of target analytes.

Illegal adulteration of traditional Chinese medicines has become a critical global safety concern, driven by the covert addition of synthetic pharmaceuticals such as phosphodiesterase type five inhibitors, anorectic agents, nonsteroidal anti-inflammatory drugs, corticosteroids, and sedatives. This review critically examines the rapid expansion of ambient ionization mass spectrometry technologies and evaluates their performance in detecting diverse adulterants across powders, pills, decoctions, creams, and botanical tissues. Techniques including desorption electrospray ionization, direct analysis in real time, wooden tip electrospray ionization, paper spray ionization, thermal desorption electrospray ionization, low temperature plasma ionization, and dielectric barrier discharge ionization demonstrate high sensitivity, structural specificity through tandem mass spectrometry, and near zero sample preparation, enabling analysis within seconds. Evidence from the past decade shows strong concordance between ambient ionization mass spectrometry screening and laboratory based chromatographic confirmation, highlighting its transformative role in high throughput surveillance, border inspection, and emergency toxicology diagnostics. The review further analyzes limitations related to matrix effects, quantitative variability, identification of novel analogues, and challenges in regulatory acceptance. Overall, ambient ionization mass spectrometry represents a significant advance for rapid front line detection of pharmaceutically adulterated herbal products, offering a scalable and versatile platform that strengthens public health protection.

Ultraviolet (UV) radiation is a major environmental factor that leads to acute and chronic reactions in the human skin. UV exposure induces wrinkle formation, DNA damage, and generation of reactive oxygen species (ROS). Most mechanistic studies of skin physiology and pharmacology related with UV-irradiated skin have focused on proteins and their related gene expression or single- targeted small molecules. The present study identified and analyzed the alteration of skin metabolites following UVB irradiation and topical retinyl palmitate (RP, 5%) treatment in hairless mice using direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) with multivariate analysis. Under the negative ion mode, the DART ion source successfully ionized various fatty acids including palmitoleic and linolenic acid. From DART-TOF-MS fingerprints measured in positive mode, the prominent dehydrated ion peak (m/z: 369, M+H-H2O) of cholesterol was characterized in all three groups. In positive mode, the discrimination among three groups was much clearer than that in negative mode by using multivariate analysis of orthogonal partial-least squares-discriminant analysis (OPLS-DA). DART-TOF-MS can ionize various small organic molecules in living tissues and is an efficient alternative analytical tool for acquiring full chemical fingerprints from living tissues without requiring sample preparation. DART-MS measurement of skin tissue with multivariate analysis proved to be a powerful method to discriminate between experimental groups and to find biomarkers for various experiment models in skin dermatological research.

Rapid detection of bacterial endotoxins in ophthalmic viscosurgical device materials by direct analysis in real time mass spectrometry

Hydride generation (HG) coupled to cryotrapping was employed to introduce, separately and with high selectivity, four gaseous arsanes into a direct analysis in real time source for high-resolution mass spectrometry (DART-HR-MS). The arsanes, i.e., arsane (AsH3), methylarsane (CH3AsH2), dimethylarsane ((CH3)2AsH), and trimethylarsane ((CH3)3As), were formed under HG conditions that were close to those typically used for analytical purposes. Arsenic containing ion species formed during ambient ionization in the DART were examined both in the positive and negative ion modes. It was clearly demonstrated that numerous arsenic ion species originated in the DART source that did not accurately reflect their origin. Pronounced oxidation, hydride abstraction, methyl group(s) loss, and formation of oligomer ions complicate the identification of the original species in both modes of detection, leading to potential misinterpretation. Suitability of the use of the DART source for identification of arsenic species in multiphase reaction systems comprising HG is discussed.