A comprehensive review of the current trends and recent advancements on the authenticity of honey.

The authenticity of honey currently poses challenges to food quality control, thus requiring continuous modernization and improvement of related analytical methodologies. This review provides a comprehensively overview of honey authenticity challenges and related analytical methods. Firstly, direct and indirect methods of honey adulteration were described in detail, commenting the existing challenges in current detection methods and market supervision approaches. As an important part, the integrated metabolomic workflow involving sample processing procedures, instrumental analysis techniques, and chemometric tools in honey authenticity studies were discussed, with a focus on their advantages, disadvantages, and scopes. Among them, various improved microscale extraction methods, combined with hyphenated instrumental analysis techniques and chemometric data processing tools, have broad application potential in honey authenticity research. The future of honey authenticity determination will involve the use of simplified and portable methods, which will enable on-site rapid detection and transfer detection technologies from the laboratory to the industry.

A bimetallic (Ni/Co) metal-organic framework with excellent oxidase-like activity for colorimetric sensing of ascorbic acid.

A novel nanozyme of bimetallic (Ni/Co) metal-organic framework (Ni/Co-MOF) was synthesized using a simultaneous precipitation and acid etching method with a zeolitic imidazolate framework ZIF-67 as the template. The as-synthesized Ni/Co-MOF catalyst presented a three-dimensional hollow nanocage structure and exhibited excellent intrinsic oxidase-like activity. It was demonstrated that Ni/Co-MOF could directly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product (oxidized TMB, oxTMB) in the absence of H2O2. The mechanisms and kinetics of this nanozyme activity were investigated, and it was determined that the catalytic activity of Ni/Co-MOF was closely related to temperature and solution pH. Owing to its strong reducibility, ascorbic acid (AA) could reduce oxTMB, and the blue color of the reaction mixture faded over time. Therefore, a novel colorimetric platform was constructed to detect AA based on the oxidase-like activity of Ni/Co-MOF. Under optimal conditions, the absorbance of ox-TMB at 652 nm decreased linearly over the 0.015-50 µM AA range with a detection limit of 0.004 µM.

Four-way self-weighted alternating normalized residue fitting algorithm with application for the analysis of serotonin in human plasma.

A novel algorithm, four-way self-weighted alternating normalized residue fitting (SWANRF), which is an extension of its three-way form, for the decomposition of quadrilinear data with new weight factors, was proposed and applied to the quantitative analysis of serotonin contents in plasma samples. It was observed that the third-order calibration could not only retain a "second-order advantage" and but also obtain other advantages. The introduction of a fourth mode can relieve the serious problem of collinearity, which seems to be one of the "third-order advantages". The proposed algorithm shows great potential as a promising alternative for the third-order calibration of a four-way data array by contrasting with four-way parallel factor analysis (four-way PARAFAC). Furthermore, both algorithms mentioned above were utilized to analyze the 5-hydroxytryptamine (serotonin) contents in plasma samples by obtaining four-way array (excitation-emission-pH-sample) data, and produced satisfactory results. The serotonin contents in plasma samples obtained by using four-way SWANRF and four-way PARAFAC were 0.324 ± 0.005 and 0.348 ± 0.006 nmol mL(-1), respectively.

Simultaneous determination of dextromethorphan and its metabolite dextrorphan in plasma samples using second-order calibration coupled with excitation-emission matrix fluorescence.

Dextromethorphan (DEX) is an antitussive agent used in many cough and cold medications, and dextrorphan (DOR) is its metabolite. Owing to their similar structures, optimization of the condition for the chromatography approach, which is in common use for determination, is both demanding and time-consuming. This paper describes a methodology that combines excitation-emission matrix fluorescence spectra with second-order calibration, and was applied to simultaneously and directly determine DEX and DOR contents in plasma samples.

Combining the least correlation design, wavelet packet transform and correlation coefficient test to reduce the size of calibration set for NIR quantitative analysis in multi-component systems.

The paper focuses on solving a common and important problem of NIR quantitative analysis in multi-component systems: how to significantly reduce the size of the calibration set while not impairing the predictive precision. To cope with the problem orthogonal discrete wavelet packet transform (WPT), the least correlation design and correlation coefficient test (r-test) have been combined together. As three examples, a two-component carbon tetrachloride system with 21 calibration samples, a two-component aqueous system with 21 calibration samples, and a two-component aqueous system with 41 calibration samples have been treated with the proposed strategy, respectively. In comparison with some previous methods based on much more calibration samples, the results out of the strategy showed that the predictive ability was not obviously decreased for the first system while being clearly strengthened for the second one, and the predictive precision out of the third one was even satisfactory enough for most cases of quantitative analysis. In addition, all important factors and parameters related to our strategy are discussed in detail.

Quantitative analysis of levodopa, carbidopa and methyldopa in human plasma samples using HPLC-DAD combined with second-order calibration based on alternating trilinear decomposition algorithm.

An HPLC method combined with second-order calibration based on alternating trilinear decomposition (ATLD) algorithm has been developed for the quantitative analysis of levodopa (LVD), carbidopa (CBD) and methyldopa (MTD) in human plasma samples. Prior to the analysis of the analytes by ATLD algorithm, three time regions of chromatograms were selected purposely for each analyte to avoid serious collinearity. Although the spectra of these analytes were similar and interferents coeluted with the analytes studied in biological samples, good recoveries of the analytes could be obtained with HPLC-DAD coupled with second-order calibration based on ATLD algorithm, additional benefits are decreasing times of analysis and less solvent consumption. The average recoveries achieved from ATLD with the factor number of 3 (N=3) were 100.1+/-2.1, 96.8+/-1.7 and 104.2+/-2.6% for LVD, CBD and MTD, respectively. In addition, elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM) were employed to evaluate the accuracy of the method.

Variable-weighted least-squares support vector machine for multivariate spectral analysis.

Multivariate spectral analysis has been widely applied in chemistry and other fields. Spectral data consisting of measurements at hundreds and even thousands of analytical channels can now be obtained in a few seconds. It is widely accepted that before a multivariate regression model is built, a well-performed variable selection can be helpful to improve the predictive ability of the model. In this paper, the concept of traditional wavelength variable selection has been extended and the idea of variable weighting is incorporated into least-squares support vector machine (LS-SVM). A recently proposed global optimization method, particle swarm optimization (PSO) algorithm is used to search for the weights of variables and the hyper-parameters involved in LS-SVM optimizing the training of a calibration set and the prediction of an independent validation set. All the computation process of this method is automatic. Two real data sets are investigated and the results are compared those of PLS, uninformative variable elimination-PLS (UVE-PLS) and LS-SVM models to demonstrate the advantages of the proposed method.

Quantitative analysis of epinephrine in human plasma samples using kinetic fluorometric method combined with second-order calibration.

A kinetic fluorometric method was proposed for the quantitative determination of epinephrine (EP) in human plasma samples with the aid of second-order calibration methods based on alternating trilinear decomposition (ATLD) and alternating fitting residue (AFR) algorithms. It was based on that EP could be gradually converted to a highly fluorescent intermediate product by an oxidation reaction, and further to a non-fluorescent degradation product (o-quinone). These methodologies fully exploit the second-order advantage of the employed three-way kinetic fluorescence data, allowing the concentrations of EP to be quantified even in the presence of uncalibrated interferences. The average recoveries obtained from ATLD and AFR with a factor number of 2 (N = 2) were 100.7 +/- 3.3 and 100.4 +/- 2.2%, respectively. In addition, elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM) were employed to evaluate the accuracy of the two algorithms.

Multi-way chemometric methodologies and applications: a central summary of our research work.

Multi-way data analysis and tensorial calibration are gaining widespread acceptance with the rapid development of modern analytical instruments. In recent years, our group working in State Key Laboratory of Chemo/Biosensing and Chemometrics in Hunan University has carried out exhaustive scientific research work in this area, such as building more canonical symbol systems, seeking the inner mathematical cyclic symmetry property for trilinear or multilinear decomposition, suggesting a series of multi-way calibration algorithms, exploring the rank estimation of three-way trilinear data array and analyzing different application systems. In this present paper, an overview from second-order data to third-order data covering about theories and applications in analytical chemistry has been presented.

Fluorescent quantification of terazosin hydrochloride content in human plasma and tablets using second-order calibration based on both parallel factor analysis and alternating penalty trilinear decomposition.

Two second-order calibration methods based on the parallel factor analysis (PARAFAC) and the alternating penalty trilinear decomposition (APTLD) method, have been utilized for the direct determination of terazosin hydrochloride (THD) in human plasma samples, coupled with the excitation-emission matrix fluorescence spectroscopy. Meanwhile, the two algorithms combing with the standard addition procedures have been applied for the determination of terazosin hydrochloride in tablets and the results were validated by the high-performance liquid chromatography with fluorescence detection. These second-order calibrations all adequately exploited the second-order advantages. For human plasma samples, the average recoveries by the PARAFAC and APTLD algorithms with the factor number of 2 (N=2) were 100.4+/-2.7% and 99.2+/-2.4%, respectively. The accuracy of two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests and t-test. It was found that both algorithms could give accurate results, and only the performance of APTLD was slightly better than that of PARAFAC. Figures of merit, such as sensitivity (SEN), selectivity (SEL) and limit of detection (LOD) were also calculated to compare the performances of the two strategies. For tablets, the average concentrations of THD in tablet were 63.5 and 63.2 ng mL(-1) by using the PARAFAC and APTLD algorithms, respectively. The accuracy was evaluated by t-test and both algorithms could give accurate results, too.

Simultaneous determination of psoralen and isopsoralen in plasma and Chinese medicine Xian Ling Gu Bao capsule by using HPLC-DAD coupled with alternating trilinear decomposition algorithm.

A method using high performance liquid chromatography with photodiode-array detection (HPLC-DAD) coupled with alternating trilinear decomposition (ATLD) algorithm was proposed for simultaneous determination of psoralen and isopsoralen in plasma and Chinese medicine "Xian Ling Gu Bao" capsule (XLGBC). In this paper, the application of ATLD algorithm into traditional chromatographic method can handle this problem that the chromatographic and spectral peaks are heavily overlapped among the analytes and even between the analytes and interferences from the background matrices. A simple improvement of chromatographic condition like mobile phase is not enough to realize effective separation for the two isomeric compounds, especially in the presence of interferences. However, the ATLD algorithm utilized "mathematical separation" instead of partial "physical or chemical separation" to directly determine the spectral profiles of the analytes of interests in complex system. The satisfactory quantification results have been gained with simple mobile phase. In the analysis of real Chinese medicine samples, the accuracy of the concentrations which were obtained by ATLD was also validated by HPLC-MS method.

Studying the interaction of pirarubicin with DNA and determining pirarubicin in human urine samples: combining excitation-emission fluorescence matrices with second-order calibration methods.

In this paper, UV-vis spectroscopy and fluorescence were combined to study the binding of Calf thymus DNA (ct-DNA) with the anthacycline antibiotic drug pirarubicin (THP). Ethidium bromide (EB) as the fluorescence probe was used to study the competitive binding interactions of THP with DNA by excitation-emission fluorescence matrices (EEFMs) coupled with the parallel factor analysis (PARAFAC) and the alternating normalization-weighted error algorithm (ANWE) with the second-order advantage. All the results conformed that THP mainly bound with DNA by intercalation. Meanwhile, the two second-order calibration methods have been successfully applied to quantify THP in urine samples. Figures of merit were applied to compare the performance of the two methods. The results presented in this work showed that both the PARAFAC and ANWE methods were the convincing way to be applied in the complex biological systems even in the presence of uncalibrated interferences.

Excitation-emission-kinetic fluorescence coupled with third-order calibration for quantifying carbaryl and investigating the hydrolysis in effluent water.

A novel method for determination of carbaryl in effluent was proposed in this study. The kinetic evolution of excitation-emission matrix fluorescence (EEM) for the pesticide were recorded and come into being a four-way data array. The four-way fluorescence data were analyzed using the parallel factor analysis (PARAFAC). The methodology exploits the second-order advantage of three-order calibration based on quadrilinear parallel factor analysis, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. It gave the satisfactory results for determination of the carbaryl in effluent samples. In addition, the kinetic study of degradation of carbaryl was performed according to the kinetic profile provided by the calibration.

Determination of indole-3-acetic acid in soil using excitation-emission matrix fluorescence with trilinear decomposition-based calibration methods.

Indole-3-acetic acid (IAA) is a phytohormone of the auxin group and is capable of coordinating the overall processes of plant growth and development. IAA is active in the very low concentration range. Therefore, it is important to quantify IAA in the low concentration range in complex system. In this work, a new spectrofluorometric method for the direct determination of IAA in soil is proposed and discussed. It combines the fluorescence excitation-emission matrices (EEMs) with second-order calibration methods based on the alternating trilinear decomposition (ATLD) algorithm and the self-weighed alternating trilinear decomposition (SWATLD) algorithm. These methodologies fully exploit the second-order advantage of the three-way fluorescence data, allowing the analyte concentrations to be quantified even in the presence of unknown fluorescent interferents. IAA recoveries in soil were determined as 100.6 +/- 3.0 and 96.9 +/- 1.1% with ATLD and SWATLD, respectively. The limits of detection obtained were 17.6 and 4.6 ng mL(-1), and the limits of quantification were 52.9 and 13.9 ng mL(-1) with ATLD and SWATLD, respectively.

Interference-free determination of and in plant samples using excitation-emission matrix fluorescence based on oxidationderivatization 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.

Simultaneous determination of 6-methylcoumarin and 7-methoxycoumarin in cosmetics using three-dimensional excitation-emission matrix fluorescence coupled with second-order calibration methods.

This paper reports a simple, rapid, and effective method for quantitative analysis of 6-methylcoumarin (6-MC) and 7-methoxycoumarin (7-MOC) in cosmetics using excitation-emission matrix (EEM) fluorescence coupled with second-order calibration. After simple pretreatments, the adopted calibration algorithms exploiting the second-order advantage, i.e., parallel factor analysis (PARAFAC) and self-weighted alternating tri-linear decomposition (SWATLD), could allow the individual concentrations of the analytes of interest to be predicted even in the presence of uncalibrated interferences. In the analysis of facial spray, with the external calibration method, the average recoveries attained from PARAFAC and SWATLD with the factor number of 3 (N=3) were 101.4+/-5.5 and 97.5+/-4.1% for 6-MC, and 103.3+/-1.7 and 101.7+/-1.8% for 7-MOC, respectively. Moreover, in the analysis of oil control nourishing toner, the standard addition method (SAM) was suggested to overcome the partial fluorescence quenching of 6-MC induced by the analyte-background interaction, which also yielded satisfactory prediction results. In addition, the accuracy of the two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM), including sensitivity (SEN), selectivity (SEL) and limit of detection (LOD). It was found that both algorithms could give accurate results, only the performance of SWATLD was slightly better than that of PARAFAC in the cases suffering from matrix effects. The method proposed lights a new avenue to determine quantitatively 6-MC and 7-MOC in cosmetics, and may hold great potential to be extended as a promising alternative for more practical applications in cosmetic quality control, due to its advantages of easy sample pretreatment, non-toxic and non-destructive analysis, and accurate spectral resolution and concentration prediction.

Determination of sulpiride in human urine using excitation-emission matrix fluorescence coupled with second-order calibration.

This paper proposes a new and effective approach for the quantitative analysis of sulpiride, a significant antipsychotic drug, in human urine samples by the incorporation of excitation-emission matrix (EEM) fluorescence and second-order calibration methodologies based on the alternating fitting residue (AFR) and self-weighted alternating trilinear decomposition (SWATLD) algorithms. With the application of a second-order advantage, the proposed strategy could be utilized for a direct concentration determination of sulpiride with a simple pretreatment step, even in the presence of serious natural fluorescent interferences. The average recoveries of sulpiride in complex urine samples by using AFR and SWATLD with an estimated component number of three were 101.2 +/- 2.1 and 94.4 +/- 0.7%, respectively. Moreover, the accuracy of the two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests as well as the figures of merit, such as sensitivity (SEN), selectivity (SEL) and limit of detection (LOD). The experimental results demonstrated that both algorithms, as promising quantitative alternatives, have been satisfactorily applied to the determination of sulpiride in human urine, but the performance of AFR was slightly better than that of SWATLD.