Pushing the frontiers: boron-11 NMR as a method for quantitative boron analysis and its application to determine boric acid in commercial biocides

Abstract

Quantitative boron-11 NMR (11B qNMR) spectroscopy has been introduced for the first time as a method to determine boric acid content in commercial biocides. Validation of the method affords a limit of detection of 0.02% w/w and a limit of quantification of 0.04% w/w, which are low enough to determine boric acid in commercial biocides. Other figures of merit such as linearity (R2 > 0.99), recovery (93.6%-106.2%), intra- and inter-day precision (from 0.7 to 2.0%), uncertainty (3.7 to 4.4%) and matrix effects were also evaluated. This method was successfully applied to determine boric acid in five different commercial biocides in a wide range of concentrations (<0.05 to 10% w/w) providing excellent results when they were compared with those obtained using inductively coupled plasma-mass spectrometry (ICP-MS). The suitability of this method for a fast and reliable quantification of boric acid in commercial biocide preparations has been demonstrated. The absence of the matrix effect allows the application of this validated method for the determination of boric acid in other matrices of diverse composition.

Accurate detection of perchlorate in epoxy resins via chlorine-35 quantitative quadrupolar NMR (qQNMR)

“…As previously observed [18][19][20] we found a linear correlation within the number of scans (Fig. 1a).…”

“…17 Our group has already validated three qQNMR methods for the first time. The first method based on 11 B (I = 3/2) was developed for the quantification of boric acid in commercial biocides, 18 and the second and third employed 14 N (I = 1) for the quantification of choline in complex matrixes such as coffee, quinoa or nutritional formulations 19 and L-carnitine in food supplements. 20 Chlorine-35 is the major isotope of the chlorine atom (natural abundance of 75.8%), being as active in terms of NMR as its isotope chlorine-37.…”

Molecular Boronic Acid-Based Saccharide Sensors

“…When considering the use of NMR to study the binding of boronic acids to diols, it may seem obvious to first consider 11 B NMR. While such studies have been undertaken, the 11 B nucleus is quadrupolar, leading to broad peaks which offer poor resolution, and requires the use of quartz NMR tubes to avoid excessive background signals from borosilicate glass; the use of 19 F NMR circumvents these challenges.…”

Restoration of catalytic activity by the preservation of ligand structure: Cu-catalysed asymmetric conjugate addition with 1,1-diborylmethane

“…During the reaction, a significant portion of the initially administered LiO t -Bu nucleophiles was consumed: in the case of the Li(acac)-free conditions the effective concentration of LiO t -Bu is 50% higher than that of the conditions with Li(acac). 15 …”