Benchtop nuclear magnetic resonance performance evaluation according to ASTM E691-22 on a population of instruments: Molar substitution determination in hydroxypropyl betadex as a case study for use in quality control environments.

The inclusion of quantitative nuclear magnetic resonance (qNMR) spectroscopy in industry has historically been stifled by a lack of accessibility, caused in-part by the large costs of traditional high-field spectrometers, the maintenance required for these, and the expertise necessary to manage and use them. In recent years, the emergence of benchtop NMR technology, an accessible, affordable, and automatable alternative, has led to a more feasible incorporation of NMR into quality control spaces, an area traditionally reserved for other techniques such as gas chromatography and liquid chromatography, which are routinely combined with detection techniques such as mass spectrometry. While these techniques are commonly used in analyzer-type applications using gold standard methods of analysis, wherein an instrument is dedicated to performing specific assays, this remains uncommon for NMR. Herein, we perform a full method verification using benchtop qNMR on a population of benchtop NMR instruments according to the ASTM designation E691-22, a standard used to determine the precision of a test method. To our knowledge, this is the first published example of this type of study for benchtop NMR spectroscopy. For this work, a total of five analysts performed assays on 23 different benchtop NMR instruments for the analysis of hydroxypropyl betadex according to the USP-NF method, and the results are compared using a variety of statistical methods. The results of this work demonstrate that benchtop NMR technology is effective and robust under repeatability and reproducibility conditions and is a powerful tool for these types of routine quality control analyses.

Determination of copolymer compositions in polyhydroxyalkanoates using 1H benchtop nuclear magnetic resonance spectroscopy.

Continuous research into polyhydroxyalkanoates (PHAs), biodegradable polymers which can be produced by, and harvested from, various bacteria has led to more cost-effective ways of isolating and commercializing them. As bio-based polymers, PHAs can be transformed into compostable bioplastics and utilized for a variety of applications. Often isolated as copolymers, the monomeric ratio compositions of these products greatly affect both the properties and consequently, possible end uses of these products. As such, methods of reliably characterizing these ratios are important for quality control and product development purposes. Herein, we discuss how 1H benchtop nuclear magnetic resonance (NMR) instruments can be used for the determination of monomeric ratio compositions in PHAs and compare results obtained at three different NMR field strengths: 1.40 T (60 MHz), 2.35 T (100 MHz), and 9.4 T (400 MHz).

Identification of seven psychedelic 2,5-dimethoxy-phenylethyl-amine-based designer drugs via benchtop 1 H nuclear magnetic resonance spectroscopy.

The dissemination of spectral information of new psychoactive substances (NPS) acquired on benchtop nuclear magnetic resonance (NMR) spectrometers is of high importance considering the emerging application of such portable and accessible instruments in forensic analyses. Seven members of the 2C-X series (2C-B, 2C-C, 2C-D, 2C-E, 2C-P, 2C-T2, and 2C-T7) of NPS were analyzed via 60 MHz 1 H benchtop NMR spectroscopy and their molecular structural relations are discussed with respect to the observed proton NMR spectra.

3,4-Methylenedioxymethamphetamine quantification via benchtop 1H qNMR spectroscopy: Method validation and its application to ecstasy tablets collected at music festivals.

We describe a method validation for the quantification of 3,4-methylenedioxymethamphetamine (MDMA) in tablets based on the United Nations Office on Drugs and Crime (UNODC) guideline for quantitative Nuclear Magnetic Resonance analysis (qNMR). qNMR experiments were carried out on a 60 MHz benchtop NMR spectrometer employing ethylene carbonate as an internal calibrant. A series of 'ecstasy' tablets seized at music events were quantified and the results discussed regarding their within-batch variation and yearly median dose. The method showed good specificity and selectivity, with linearity, precision, accuracy, and recovery well within the UNODC recommended criteria. The limit of detection and quantification are 0.33 mg/mL and 0.10 mg/mL respectively, proving the method works well on small amounts of MDMA. Overall, the lowest amount of MDMA free base detected in this study was 9.35 mg in a piperazine mix, while the highest dosed tablet contained 237.55 mg MDMA free base, with a 9.1% decrease in median amount compared to the pre-pandemic data (2019), but still higher than the data collected in a previous study (105 mg median amount of MDMA free base in 2018). The within-batch variation was insignificant for one of the seizures but showed greater variation for the other, which confirmed that the MDMA content of a single tablet may not reflect that of the whole batch. This dynamic upward change in tablet dosage highlights the importance of ongoing trend monitoring and specific prevention intervention to counteract the negative consequences associated with MDMA use. Benchtop NMR has been successfully employed in quality control, material science and more recently, drug analysis. The present study demonstrates its beneficial application in forensic science overcoming the limitations of currently available instruments and techniques employed in harm reduction and field testing.

Lithium-7 qNMR as a method to quantify lithium content in brines using benchtop NMR.

A novel 7Li quantitative NMR (qNMR) method to analyze lithium was developed to determine the lithium content in real brine samples using benchtop NMR instruments. The method was validated, and limits of detection and quantification of 40 and 100 ppm, respectively, were determined. Linearity, precision, and bias were also experimentally determined, and the results are presented herein. The results were compared to those obtained using atomic absorption (AA) spectroscopy, currently one of the few validated methods for the quantification of lithium. The method provides both accurate and precise results, as well as excellent correlation with AA. The absence of matrix effects, combined with no need for sample preparation or deuterated solvents, shows potential applicability in the mining industry.

Quantitative analysis of cannabinoids using benchtop NMR instruments.

The quantification of cannabinoids is an essential part of cannabis profiling and testing, whether for medical or recreational use. As regulatory bodies continue to increase testing requirements for these products, it is crucial that alternative and effective analytical methods be developed. Herein, we describe the use of benchtop NMR instruments for the quantification of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in a variety of cannabis concentrates and compare the values to those obtained using HPLC, the most common approach for the quantification of cannabinoids. Based on the discrepancies observed in test values from different laboratories using only HPLC, the value of orthogonal testing methods has been identified and is increasingly desired.

BN-Dibenzo[a,o]picenes: analogues of an unknown polycyclic aromatic hydrocarbon.

Reflecting on synthetic pinnacles: Whereas the parent hydrocarbon is not readily accessible, several examples of BN substituted-dibenzo[a,o]picenes can be prepared in two steps from known starting materials. These non-linear heptacene analogues are water-stable materials. Their preparation utilizes a potentially general method for preparing extended BN analogues of difficult-to-synthesize polycyclic aromatic hydrocarbon frameworks.

Photochemical synthesis of a ladder diborole: a new boron-containing conjugate material.

Climbing the ladder: Reductive cyclization of alkynyl haloboranes lead to the bis-benzocycloborabutylidene rather than the expected ladder diborole, despite the former being much less thermodynamically favored. Photochemical conversion to the ladder diborole was, however, quite facile upon irradiation at 254 nm.