Quantitative determination of surface silanol groups in silicagel by deuterium exchange combined with infrared spectroscopy and chemometrics

Abstract

Concentration of silanol groups on silica gel surface has been quantitatively determined using the deuterium exchange method. Simple and effective procedures have been used in pre-sample drying, deuterium exchange and extraction of resulting isotopic mixture from the exchange reaction. Each of four silica gel samples with varying surface area has been subjected to pre-drying to remove adsorbed water and then quantitatively mixed with deuterium oxide in a steel bomb for isotopic exchange. The resulting D(2)O/water mixture was then extracted by applying high pressure using infrared pellet press. The infrared spectrum of the isotopic mixture was measured and the composition was then determined by a multivariate calibration model established between infrared profiles of water in D(2)O standard mixtures and their composition. The results show that the silanol group concentration determined agrees with the values reported in the literature.

Mass spectrometric separation and quantitation of overlapping isotopologues. H2O/HOD/D2O and H2Se/HDSe/D2Se mixtures

“…Alternating least-squares have been used previously in spectroscopy to reconstruct the infrared spectra of HOD and eventually determine the individual amounts of H 2 O, HOD, and [3,4]. This technique is also of general interest in solving liquid chromatography mass spectrometry co-elution problems [5].…”

“…The following reagents were used: NaBH 4 pellets (Alfa Aesar, Ward Hill, MA); NaBD 4 Se(IV) in HNO 3 aqueous media (Oak Ridge National Laboratory, Oak Ridge, TN) was used to spike the reaction media in septum-sealed vials for cold vapor generation of their corresponding hydrides. All other reagents were of analytical grade.…”

New insights into the surface functionalities and adsorption evolution of water molecules on silica gel surface: A study by second derivative near infrared spectroscopy

“…7 shows that the sample C contains around 68% of the silanol groups still remaining on the surface after adsorbing 1.5 water molecules/nm 2 . The sample also has a silanol number 3 [27]. This means that the water molecules are bound to only 32%…”

Our Experience of Using Thermally Recycled Silica Gel in a Teaching and Small Research Laboratory Setting

“…There has been an ongoing discussion [1][2][3][4] on the usefulness of recycling silica gel as stationary phase material, where oftentimes the recycling suggested consists of eluting and thereby removing adsorbed substances with polar solvents such as with ethyl acetate and methanol, followed by water and drying the silica gel in an oven at 800 °C [1] or oxidative treatment, e.g., with an aqueous solution of KMnO4 and H2SO4, with subsequent washings with oxalic acid and deionized water, followed by heat treatment at 120 °C [1] or with a treatment of an aqueous solution of H2O2 and subsequently deionized water, followed by heat treatment at 120 °C [1]or by H2O2-solar light [2]. It has been noted that silica gel will lose adsorbed water at its surface already below 150 °C and that silanol groups will convert to siloxanes at above 300 °C [5][6][7] and that this may lead to structural instability [4] and thus to lower separation properties of the heat-treated silica. In addition, it has been warned against using such recycled silica gel for the work-up of untested reactions in research.…”