Shu-Rong Zhang

A new third‐order calibration method with application for analysis of four‐way data arrays

A novel third‐order calibration algorithm, alternating weighted residue constraint quadrilinear decomposition (AWRCQLD) based on pseudo‐fully stretched matrix forms of quadrilinear model, was developed for the quantitative analysis of four‐way data arrays. The AWRCQLD algorithm is based on the new scheme that introduces four unique constraint parts to improve the quality of four‐way PARAFAC algorithm. The tested results demonstrated that the AWRCQLD algorithm has the advantage of faster convergence rate and being insensitive to the excess component number adopted in the model compared with four‐way PARAFAC. Moreover, simulated data and real experimental data were analyzed to explore the third‐order advantage over the second‐order counterpart. The results showed that third‐order calibration methods possess third‐order advantages which allow more inherent information to be obtained from four‐way data, so it can improve the resolving and quantitative capability in contrast with second‐order calibration especially in high collinear systems. Copyright

Multi-targeted interference-free determination of ten β-blockers in human urine and plasma samples by alternating trilinear decomposition algorithm-assisted liquid chromatography-mass spectrometry in full scan mode: comparison with multiple reaction monitoring.

β-blockers are the first-line therapeutic agents for treating cardiovascular diseases and also a class of prohibited substances in athletic competitions. In this work, a smart strategy that combines three-way liquid chromatography-mass spectrometry (LC-MS) data with second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm was developed for simultaneous determination of ten β-blockers in human urine and plasma samples. This flexible strategy proved to be a useful tool to solve the problems of overlapped peaks and uncalibrated interferences encountered in quantitative LC-MS, and made the multi-targeted interference-free qualitative and quantitative analysis of β-blockers in complex matrices possible. The limits of detection were in the range of 2.0×10(-5)-6.2×10(-3) μg mL(-1), and the average recoveries were between 90 and 110% with standard deviations and average relative prediction errors less than 10%, indicating that the strategy could provide satisfactory prediction results for ten β-blockers in human urine and plasma samples only using liquid chromatography hyphenated single-quadrupole mass spectrometer in full scan mode. To further confirm the feasibility and reliability of the proposed method, the same batch samples were analyzed by multiple reaction monitoring (MRM) method. T-test demonstrated that there are no significant differences between the prediction results of the two methods. Considering the advantages of fast, low-cost, high sensitivity, and no need of complicated chromatographic and tandem mass spectrometric conditions optimization, the proposed strategy is expected to be extended as an attractive alternative method to quantify analyte(s) of interest in complex systems such as cells, biological fluids, food, environment, pharmaceuticals and other complex samples.

Interference-free determination of abscisic acid and gibberellin in plant samples using excitation-emission matrix fluorescence based on oxidation derivatization coupled with second-order calibration methods.

A sensitive excitation-emission fluorescence method with a second-order calibration strategy is proposed to simultaneously determine abscisic acid (ABA) and gibberellin (GA) contents in extracts of leaves and buds of ginkgo. The methodology is based on the alternating normalization-weighed error (ANWE) and the parallel factor analysis (PARAFAC) algorithms, which make it possible that the ABA and GA concentration can be attained in extract of plants even in the presence of unknown interference from potential interfering matrix contaminants introduced during the simple pretreatment procedure. Satisfactory recoveries were obtained although the excitation and emission profiles of the analytes were heavily overlapped with each other and the background in the extracts. The limits of detection obtained for GA and ABA in leaf samples were 9.6 and 6.9 ng mL-1, respectively, which were in the concentration range (from hundreds to several ng g-1) for GA and ABA in leaves in different periods. Furthermore, in order to investigate the performance of the developed method, some statistical parameters and figures of merit of ANWE and PARAFAC are evaluated. The method proposed lights a new avenue to determine quantitatively phytohormones in extracts of plants with a simple pretreatment procedure, and may hold potential to be extended as a promising alternative for more practical applications in plant growth processes.

Self-weighted alternating normalized residue fitting algorithm with application to quantitative analysis of excitation-emission matrix fluorescence data

In this paper, a novel algorithm named as self-weighted alternating normalized residue fitting (SWANRF) has been proposed for quantitative analysis of excitation-emission matrix fluorescence data. The proposed algorithm can obtain satisfactory solutions for the analytes of interest even in the presence of potentially unknown interferences, fully exploiting the second-order advantage. By comparing the performance of the alternating trilinear decomposion (ATLD) algorithm, and PARAFAC-ALS on one simulated and two real fluorescence spectral data arrays, SWANRF can deal with higher collinearity problems, obtain improved convergence rate through shuffling the computational matrices, and partially reextract valid information from the residue and further remove invalid information to the residue. In addition, SWANRF can only behave more stably, independent of the used initial values unlike PARAFAC, but also achieves very smooth profiles at high noise level, where ATLD may be helpless with the actual component and has to resort to additional component(s) to fit noise, yielding rough profiles. Based on these attractive merits, such a novel method may hold great potential to be extended as a promising alternative for three-way data array analysis.

A novel method to handle Rayleigh scattering in three-way excitation-emission fluorescence data

Rayleigh scattering, which is often contained in excitation-emission fluorescence data, does not conform to a trilinear structure and its existence can complicate decomposition using second-order calibration methods. In this paper, a novel method, two-direction resection PARAFAC (TDR-PARAFAC) is proposed to deal with three-way fluorescence data including Rayleigh scattering. This is a convenient method where only two parameters, i.e. the scattering regions and the number of components, are required. A simulated data set was employed to demonstrate the reasonability of the new method. It was successfully used to analyze two experimental data sets in which interferents and significant Rayleigh scattering were present. The performance of the new method was compared by inserting missing values within PARAFAC (IMV-PARAFAC). The final results suggest that TDR-PARAFAC can not only obtain more stable and satisfactory resolution than IMV-PARAFAC, but also that it speeds up the analysis. In addition, the new method can be applied to other interferences such as Rayleigh scattering, which appear in the same position in each sample matrix.

A study on the differential strategy of some iterative trilinear decomposition algorithms: PARAFAC-ALS, ATLD, SWATLD, and APTLD

This study presents an in‐depth discussion of the differential properties of various iterative trilinear decomposition algorithms, including Parallel Factor Analysis‐Alternating Least Squares (PARAFAC‐ALS), Alternating Trilinear Decomposition (ATLD), Self‐Weighted Alternating Trilinear Decomposition (SWATLD), and Alternating Penalty Trilinear Decomposition (APTLD). The shape of each algorithms objective function (“convex” or “strictly convex”) is related to the algorithms sensitivity to the estimated component number of the trilinear system. Different situations near the objective solution are analyzed both theoretically and numerically. The wall of perturbation generated by deviations in the iterative steps prevents the PARAFAC algorithm from achieving the objective solution when the component number is overestimated. This may explain, from a calculational perspective, why the PARAFAC algorithm could not obtain the objective solution or any equivalent thereto (although equivalents might still be chemically meaningful optimal solutions). The different effects of deviation and residual on the algorithms are demonstrated by numerical analysis in this paper. The convergence rate can be improved by the use of high‐performance computing strategy of the specific algorithm. The concept of solution set discussed in this paper complements the theory of the uniqueness of trilinear decomposition. Copyright

The maintenance of the second-order advantage: Second-order calibration of excitation–emission matrix fluorescence for quantitative analysis of herbicide napropamide in various environmental samples

A rapid non-separative spectrofluorometric method based on the second-order calibration of excitation-emission matrix (EEM) fluorescence was proposed for the determination of napropamide (NAP) in soil, river sediment, and wastewater as well as river water samples. With 0.10 mol L(-1) sodium citrate-hydrochloric acid (HCl) buffer solution of pH 2.2, the system of NAP has a large increase in fluorescence intensity. To handle the intrinsic fluorescence interferences of environmental samples, the alternating penalty trilinear decomposition (APTLD) algorithm as an efficient second-order calibration method was employed. Satisfactory results have been achieved for NAP in complex environmental samples. The limit of detection obtained for NAP in soil, river sediment, wastewater and river water samples were 0.80, 0.24, 0.12, 0.071 ng mL(-1), respectively. Furthermore, in order to fully investigate the performance of second-order calibration method, we test the second-order calibration method using different calibration approaches including the single matrix model, the intra-day various matrices model and the global model based on the APTLD algorithm with nature environmental datasets. The results showed the second-order calibration methods also enable one or more analyte(s) of interest to be determined simultaneously in the samples with various types of matrices. The maintenance of second-order advantage has been demonstrated in simultaneous determinations of the analyte of interests in the environmental samples of various matrices.

Quantitative analysis of fluphenazine hydrochloride in human urine using excitation-emission matrix fluorescence based on oxidation derivatization and combined with second-order calibration methods

An effective excitation-emission fluorescence method was proposed to determine fluphenazine hydrochloride (FPH) in the presence of chlorprothixene (CPT) in human urine samples with the aid of second-order calibration methods based on the full rank parallel factor analysis (FRA-PARAFAC) and parallel factor analysis (PARAFAC) algorithms respectively. FPH can be transformed into a highly fluorescent derivative through oxidation reaction with KMnO4. Both methods have been recommended to attain FPH concentration in urine samples free from interferents of urine matrix, even in the presence of another antipsychotic drug chlorprothixene (CPT). Satisfactory results have been achieved for FPH in predicted samples, fully exploiting “second-order advantage”. The average recoveries of FPH in the urine samples obtained by using both FRA-PARAFAC and PARAFAC with N = 4 are 101.0 ± 2.8% and 102.3 ± 2.8%, respectively. Furthermore, in order to investigate the performance of the proposed methods, some statistical parameters and figures of merit of FRA-PARAFAC and PARAFAC, i.e., sensitivity (SEN), selectivity (SEL) and limit of detection (LOD) were evaluated, and the accuracy of both algorithms was also validated by the elliptical joint confidence region (EJCR) test.

Interaction of epicatechin with bovine serum albumin using fluorescence quenching combined with chemometrics

The interaction between BSA and epicatechin was studied using fluorescence quenching titrations combined with trilinear decomposition method and excitation-emission matrix (EEM) fluorescence. The resolved spectra were highly similar with the actual ones which indicated that the resolved results were reliable. The relevant parameters of the binding process were obtained by quantifying each substance in the complicated mixtures in situ. The quenching was static quenching, epicatechin had a weak interaction with BSA and the binding site was one. The total concentration and the free concentration of quenchers had different effect on the system. The results demonstrated that the method exploited in this article is a useful tool to investigate complicated interactions, avoiding complicated pretreatment and simplify experimental procedure.

Quantitative study of state switching in proteins using a single probe combined with trilinear decomposition

The present investigation attempts to separate the variation in time domain from steady-state fluorescence and to discuss quantitatively the state-switching of α-chymotrypsin (CHT). The activity of CHT is pH dependent (inactive at low pH, such as 2.2, but active at physiological pH, such as 8). ANS (1-anilinonaphthalene-8-sulfonate) has two states of fluorescence corresponding to different excitation and emission processes. Though a steady-state technique, Excitation–Emission Matrix fluorescence (EEM) can record all the excitation and emission signals for the ANS–CHT complex system. The trilinear decomposition of the constructed three-way data set (using EEM data of different samples) can provide excitation and emission spectra indicating specific excitation and emission processes, respectively, and a quantitative description for the time domain processes. Besides a detailed description of the excitation–emission processes of ANS, the quantitative investigation of state-switching by CHT is also possible because the fluorescence, due to the S1,ct state of ANS, is sensitive to the solvation environment, which is one of the indicators of CHT activity. Finally, the switching output curve of the ANS–CHT system over a wide pH range is obtained. This study proposes a convenient and economical protocol for investigating state-switching in proteins.