In this paper, we briefly review the remote mass spectrometric techniques that are viable to perform “endoscopic mass spectrometry,” i.e., in-situ and in-vivo MS analysis inside the cavity of human or animal body. We also report our experience with a moving string sampling probe for the remote sample collection and the transportation of adhered sample to an ion source near the mass spectrometer. With a miniaturization of the probe, the method described here has the potential to be fit directly into a medical endoscope.
To provide safe and effective products to customers in the cosmetic industry, mass spectrometry (MS) is an indispensable analytical tool. In addition to its outstanding sensitivity and specificity, the method is applicable to a wide variety of compounds, which makes it irreplaceable for the development of cosmetics, which requires the analysis of complex systems. Because most cosmetic products are applied directly to the skin and function as they are designed, monitoring the molecular compositions of endogenous or exogenous compounds in or on the skin is crucial to ensure the safety and efficacy of a cosmetic product. Recent advancements in MS and ionization techniques, such as MS imaging and ambient ionization, now provide access to richer and deeper molecular information with less time and effort. This brief review discusses advanced ionization techniques that are currently used in the field of cosmetic science using two examples, namely, the use of desorption electrospray ionization and zero-volt paperspray ionization to detect trace molecules in or on human skin.
Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is one of the most widely used soft ionization methods for biomolecules, the lack of detailed understanding of ionization mechanisms restricts its application in the analysis of carbohydrates. Structural identification of carbohydrates achieved by MALDI mass spectrometry helps us to gain insights into biological functions and pathogenesis of disease. In this review, we highlight mechanistic details of MALDI, including both ionization and desorption. Strategies to improve the ion yield of carbohydrates are also reviewed. Furthermore, commonly used fragmentation methods to identify the structure are discussed.
The relationship between mass and charge has been a crucial topic in mass spectrometry (MS) because the mass itself is typically evaluated based on the m/z ratio. Despite the fact that this measurement is indirect, a precise mass can be obtained from the m/z value with a high m/z resolution up to 105 for samples in the low mass and low charge region under 10,000 Da and 20 e, respectively. However, the target of MS has recently been expanded to the very heavy region of Mega or Giga Da, which includes large particles and biocomplexes, with very large and widely distributed charge from kilo to Mega range. In this region, it is necessary to evaluate charge and mass simultaneously. Recent studies for simultaneous mass and charge observation and related phenomena are discussed in this review.
We compared two ionization methods, matrix assisted laser desorption/ionization (MALDI) and nanoparticle assisted laser desorption/ionization (Nano-PALDI) mass spectrometry (MS), for the analysis of amino acids derivatized with Py-Tag™ that consists pyrylium-based compound. Py-Tag is a useful stable derivatization reagent due to wide mass differences (using 13C as the sole stable labelling isotope). For Py-Tag labelled lysine, sensitive signals that showed less noise with a ten times higher sensitivity, showed a wider mass difference by Nano-PALDI MS compared to MALDI MS.
Six different sequences of hexasaccharides, pyridylaminated malto-hexaoses containing one N-acetyl hexosamine (HexNAc) residue, were analyzed using matrix-assisted laser desorption/ionization (MALDI) tandem time-of-flight (TOF) mass spectrometry (MS). Based on the product ion spectra of sodium adducts [M+Na]+, the chemical species of the observed product ions contained a HexNAc residue and had high ion abundance, indicating that the HexNAc residue had a higher affinity to sodium atom than glucopyranose. The acetamide group coordinated easily to sodium atom. This general rule of product ion generation was useful to predict the structure of the oligosaccharides based on the MS/MS product ion spectra.
We developed a dual plasma desorption/ionization system using two plasmas for the semi-invasive analysis of compounds on heat-sensitive substrates such as skin. The first plasma was used for the desorption of the surface compounds, whereas the second was used for the ionization of the desorbed compounds. Using the two plasmas, each process can be optimized individually. A successful analysis of phenyl salicylate and 2-isopropylpyridine was achieved using the developed system. Furthermore, we showed that it was possible to detect the mass signals derived from a sample even at a distance 50 times greater than the distance from the position at which the samples were detached. In addition, to increase the intensity of the mass signal, 0%–0.02% (v/v) of hydrogen gas was added to the base gas generated in the ionizing plasma. We found that by optimizing the gas flow rate through the addition of a small amount of hydrogen gas, it was possible to obtain the intensity of the mass signal that was 45–824 times greater than that obtained without the addition of hydrogen gas.