Removal of Paramagnetic Ions Prior to Analysis of Organic Reactions in Aqueous Solutions by NMR Spectroscopy

Abstract

This article describes a method for improving 1 H NMR spectra of aqueous samples containing paramagnetic metals by precipitation of metal cations with a variety of counteranions. The addition of hydroxide, phosphate, carbonate, and arsenate to solutions of transition metals such as Fe 2+ and Mn 2+ can reduce line broadening and improve the ability of a spectrometer to lock on the signal of deuterium. The method is most effective under strongly alkaline conditions, and care must be taken to observe whether the organic substrates undergo side reactions or are themselves removed from solution upon addition of the precipitating salts. As a demonstration of the practical value of the method, we show that NMR spectroscopy can be used to monitor the transition-metal-mediated hydrolysis of glycylglycine (Gly 2 ).

Unraveling the Origin of an Unusual Shift in the Electroluminescence of 1D CsCu2I3 Light-Emitting Diodes

“…Note that the Cu + in this mixture can be easily oxidized to paramagnetic Cu 2+ , and it can create local magnetic fields that are different from the applied magnetic field, which may lead to significant line broadening or signal suppression. 37,38 Overall, the changes in ETL resonances in the presence of CsCu 2 I 3 are insignificant; therefore, there is no concrete evidence from NMR data supporting the formation of complex between CsCu 2 I 3 and ETLs. Further, to determine the complex formation between ETLs and 1D metal halides, we performed FTIR analyses (Figure S10) on ETLs before and after mixing with CsI, CuI, and CsCu 2 I 3 .…”

Proton nuclear magnetic resonance (1H NMR) of flammable organic chemicals in radioactive high‐level supernatant waste at the Savannah River Site (SRS)

“…“As received” samples with low hydroxyl concentration (<1 M) received ion‐exchanged treatment only. One benefit of samples with high hydroxide concentration is their low concentration of ions with high magnetic susceptibility, like Fe 2+ and Mn 2+ , which precipitates in caustic solutions 44 …”

“…One benefit of samples with high hydroxide concentration is their low concentration of ions with high magnetic susceptibility, like Fe 2+ and Mn 2+ , which precipitates in caustic solutions. 44 For building a calibration line that can estimate the glycolate concentration, the samples were treated as follows: The treated sample (supernatant) was divided into various portions (five portions). Each portion was…”

Ionometallurgy: an academic exercise or promising approach?

“…However, it has to be taken into account, that the detection limit is relatively high and that especially the presence of paramagnetic metal ions signicantly affects the quality of the spectra. [174][175][176] Mass spectrometry is a suitable addition that allows for the identication of traces of compounds that potentially accumulate during repeated IL or DES usage. This will contribute to a critical assessment of newly developed ILs and DESs from the beginning.…”