Design of a New Concentration Series for the Orthogonal Sample Design Approach and Estimation of the Number of Reactions in Chemical Systems

Abstract

A new concentration series is proposed for the construction of a two-dimensional (2D) synchronous spectrum for orthogonal sample design analysis to probe intermolecular interaction between solutes dissolved in the same solutions. The obtained 2D synchronous spectrum possesses the following two properties: (1) cross peaks in the 2D synchronous spectra can be used to reflect intermolecular interaction reliably, since interference portions that have nothing to do with intermolecular interaction are completely removed, and (2) the two-dimensional synchronous spectrum produced can effectively avoid accidental collinearity. Hence, the correct number of nonzero eigenvalues can be obtained so that the number of chemical reactions can be estimated. In a real chemical system, noise present in one-dimensional spectra may also produce nonzero eigenvalues. To get the correct number of chemical reactions, we classified nonzero eigenvalues into significant nonzero eigenvalues and insignificant nonzero eigenvalues. Significant nonzero eigenvalues can be identified by inspecting the pattern of the corresponding eigenvector with help of the Durbin-Watson statistic. As a result, the correct number of chemical reactions can be obtained from significant nonzero eigenvalues. This approach provides a solid basis to obtain insight into subtle spectral variations caused by intermolecular interaction.

Intensity Enhancement of a Two-Dimensional Asynchronous Spectrum Without Noise Level Fluctuation Escalation Using a One-Dimensional Spectra Sequence Change

“…In practice, a considerable amount of noise is always unavoidable in 1D spectra that are used to construct 2D/ n D spectra. 34 As demonstrated in our previous work, noise in 1D spectra is magnified in the generation of a 2D asynchronous spectrum. 35 The interference of noise is even exacerbated when an n D spectrum is constructed in the analysis of bilinear data from mixture containing multiple components.…”

Two-dimensional asynchronous spectrum with auxiliary cross peaks in probing intermolecular interactions

“…According to our previous work [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] , the following experiment is Figure 2b, we learn that the interactions between benzo-15-crown-5 and Li + make the characteristic peak of benzo-15-crown-5 undergo blue-shift (∆x U >0). In domain II, a pair of vertical auxiliary cross peaks can be observed.…”

“…According to our previous work, [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] the following experiment is performed: benzo-15-crown-5 is dissolved in methanol alone. A good linear relationship between the absorbance of the 1597 cm À1 band and the concentration of benzo-15-crown-5 can be obtained when the concentration range of benzo-15-crown-5 is between 0.00 mol L À1 and 0.30 mol L À1 (ESI †).…”

“…To address the problem, we proposed orthogonal sample design scheme (OSD) approach in our previous work [48][49][50][51][52][53] . The brief description of the OSD approach by Noda in his recent review [43] is given as follows:…”

“…To address the problem, we proposed an orthogonal sample design scheme (OSD) approach in our previous work. [48][49][50][51][52][53] The brief description of the OSD approach by Noda in his recent review 43 is given as follows: the basic concept of OSD is to use a well-designed set of concentration series for two different constituents in solution mixtures, such that patterns of concentration variations of the two species will become mathematically orthogonal to each other. The imposed orthogonality will break down when the apparent deviation from the Beers-Lambert law, oen associated with the presence of specic intermolecular interactions, is observed.…”