Related Articles

• Analyses of the thermal characteristics and gaseous products of guanidine nitrate/basic copper nitrate mixtures using calorimetry with high resolution mass spectrometry

  This work assessed the pyrolysis of a well-established gas generating agent consisting of a mixture of guanidine nitrate (GN) with basic copper nitrate (BCN), using thermogravimetry-differential scanning calorimetry in conjunction with high resolution mass spectrometry (TG/DSC/HRMS). This instrumentation simultaneously determined mass changes and heat flow, and also permitted evaluation of evolved gases on an accurate mass basis. Fragmentation ratio correction was used to analyze the MS data acquired via electron ionization. GN/BCN mixtures were found to undergo pyrolysis to evolve H2O, N2, NO, CO2 and N2O. Using HRMS, species having similar masses, such as CO2 and N2O, CO and N2, and NH3 and OH, were successfully distinguished. The thermal analysis data and the gas evolution results allowed a pyrolysis mechanism to be proposed. In this mechanism, a copper(II) complex obtained from the BCN catalytically decomposes NH3 generated from the GN to produce N2 and H2O. The pyrolysis of a mixture of GN and BCN thus provides a synergistic effect that increases the heat and gas output.
• Selective detection of active pharmaceutical ingredients in tablet formulations using solid-state NMR spectroscopy

  Atomic-level characterization of active pharmaceutical ingredients (API) is crucial in pharmaceutical industry because APIs play an important role in physicochemical properties of drug formulations. However, the analysis of targeted APIs in intact tablet formulations is less straightforward due to the coexistence of excipients as major components and different APIs at dilute concentrations (often below 10 ​wt% loading). Although solid-state (ss) NMR spectroscopy is widely used to investigate short-range order, polymorphism, and pseudo-polymorphism in neat pharmaceutical compounds, the analysis of complex drug formulations is often limited by overlapped signals that originate from structurally different APIs and excipients. In particular, such examples are frequently encountered in the analysis of 1H ssNMR spectra of pharmaceutical formulations. While the high-resolution in 1H ssNMR spectra can be attained by, for example, high magnetic fields accompanied by fast magic-angle spinning (MAS) approaches, the spectral complexity associated with the mixtures of compounds hinders the accurate determination of chemical shifts and through-space proximities. Here we propose a fast MAS (70 ​kHz) NMR experiment for the selective detection of 1H signals associated with an API from a severely overlapped NMR spectrum of a tablet formulation. Spectral simplification is achieved by combining (i) symmetry-based dipolar recoupling (SR412) rotational-echo saturation-pulse double-resonance (RESPDOR) with phase-modulate (PM) saturation pulses, (ii) radio frequency-driven recoupling (RFDR), and (iii) double-quantum excitation using Back-to-Back (BaBa) pulse sequence elements. First, 1H sites in close proximities to 14N nuclei of an API are excited using a PM-S-RESPDOR sequence, and simultaneously, the other unwanted 1H signals of excipients are suppressed. Then, 1H magnetization transfer to adjacent 1H sites in the API is achieved by spin diffusion process using a RFDR sequence, which polarizes to 1H sites within the crystalline API regions of the drug formulation. Next, a PM-S-RESPDOR-RFDR sequence is combined with a Back-to-Back (BaBa) sequence to elucidate local-structures and 1H–1H proximities of the API in a dosage form. The PM-S-RESPDOR-RFDR-BaBa experiment is employed in one- (1D) and two-dimensional (2D) versions to selectively detect the 1H ssNMR spectrum of l-cysteine (10.6 ​wt% or 0.11 ​mg) in a commercial formulation, and compared with the spectra of neat l-cysteine recorded using a standard BaBa experiment. The 2D 1H double-quantum−single-quantum (DQ-SQ) spectrum of the API (l-cysteine)-detected pharmaceutical tablet is in good agreement with the 2D 1H DQ-SQ spectrum obtained from the pure API molecule. Furthermore, the sensitivity and robustness of the experiment is examined by selectively detecting 1H{14N} signals in an amino acid salt, l-histidine.H2O.HCl.
• Analysis of duct tapes by thermal desorption and pyrolysis mass spectrometry and X-ray-fluorescence spectroscopy

  The identification of pressure-sensitive tapes such as duct tape and electrical tape is an important forensic application. Here we show the application of thermal desorption and pyrolysis combined with Direct Analysis in Real Time (DART) mass spectrometry to distinguish between manufacturers and brands of duct tapes. X-ray fluorescence (XRF) provides complementary information about the atomic composition of the different tapes.
• Detection of Lipids Using Direct Analysis in Real Time Mass Spectrometry

  There has been a recent trend in mass spectrometry towards the development of “open-air” ionization sources. These techniques allow for the rapid analysis of samples at atmospheric pressure with little or no sample preparation. The Direct Analysis in Real Time (DART™) ion source, which is ideal for the analysis of small molecules, represents the first and simplest of the open-air techniques.1 This source creates ions based on the interactions of long-lived excited state neutral atoms or molecules (“metastables”) with the sample and atmospheric gases.
• Rapid Detection of Melamine in Dry Milk Using AccuTOF-DART

  Recent events have led to the recall of both pet food and dairy food products from international consumer markets. In both cases, melamine was added to these products to show a higher chemical signature for proteins, which in turn would increase the reported quality of the food. Unfortunately, the effect of this melamine addition caused the death of both pets and babies that consumed these tainted products. As a result, there is growing government and consumer concern towards the presence of melamine in food products. Because of this concern, there is a need for a rapid and accurate test to quickly determine the presence of melamine in these food products. Previously, the JEOL AccuTOF-DART was shown to be an effective technique for determining the presence of melamine in pet food. In this work, we extend the application of AccuTOF-DART to show that melamine can be rapidly detected when it is present in dry nonfat milk.
• Rapid screening of stobilurins in crude solid materials (wheat grains) using DART-TOFMS

  Direct control of solid materials for pesticide residues is a challenging task enabling fast contamination screening. In our study, we investigated direct analysis of strobilurin fungicides in milled wheat grains. Strobilurins, systemic pesticides originated from natural fungicidal derivatives, play an important role in control of various plant pathogens. Because of their unique protective properties, significant yield enhancements and longer retention of green leaf tissue, strobilurins have been widely used in agriculture since their introduction on the market in 1992. As other pesticides, these compounds are involved in control and monitoring surveys underta