Li-Xia Xie

A chemometrics-assisted excitation–emission matrix fluorescence method for simultaneous determination of arbutin and hydroquinone in cosmetic products

A fast analytical method that combines second-order calibration based on alternating trilinear decomposition (ATLD) algorithm with excitation–emission matrix (EEM) fluorescence technique is proposed to mathematically separate the overlapped spectra and simultaneously quantify arbutin (AR) and hydroquinone (HQ) in cosmetic products. This method inherits the merit of high sensitivity of traditional fluorescence and fully realizes the “second-order advantage”. For AR and HQ, the calibration ranges are 40.00–400.00 and 20.00–200.00 ng mL−1, respectively. The limits of detection for both analytes are in the range of 1.51–4.01 ng mL−1. The proposed method could be applied to diluted samples of different cosmetic products with satisfactory results. The actual concentrations of AR in the tested cosmetic products are found to be in the allowable concentration range (7%); while, the prohibited skin whitening agent HQ is detected in lotion. The contents of AR and HQ in the tested cosmetic products obtained by the proposed method are also in accordance with those of the validated high-performance liquid chromatographic method. These satisfactory results indicate that the proposed method has the potential to accurately quantify AR and HQ in complex matrices containing uncalibrated interferents, and shows promise as a reliable tool for quality monitoring of cosmetic products.

Rapid and simultaneous determination of five vinca alkaloids in Catharanthus roseus and human serum using trilinear component modeling of liquid chromatography–diode array detection data

A novel chemometrics-assisted high performance liquid chromatography method coupled with diode array detector (HPLC-DAD) was proposed for the simultaneous determination of vincristine (VCR), vinblastine (VLB), vindoline (VDL), catharanthine (CAT) and yohimbine (YHB) in Catharanthus roseus (C. roseus) and human serum samples. With the second-order advantage of the alternating trilinear decomposition (ATLD) method, the resolution and rapid determination of five components of interest in complex matrices were performed, even in the present of heavy overlaps and unknown interferences. Therefore, multi-step purification was omitted and five components could be fast eluted out within 7.5min under simple isocratic elution condition (acetonitrile/0.2% formic acid water, 37:63, v/v). Statistical parameters, such as the linear correlation coefficient (R(2)), root-mean-square error of prediction (RMSEP), limit of detection (LOD) and limit of quantitation (LOQ) had been calculated to investigate the accuracy and reliability of the method. The average recoveries of five vinca alkaloids ranged from 97.1% to 101.9% and 98.8% to 103.0% in C. roseus and human serum samples, respectively. The five vinca alkaloids were adequately determined with limits of detection (LODs) of 29.5-49.3ngmL(-1) in C. roseus and 12.4-27.2ngmL(-1) in human serum samples, respectively. The obtained results demonstrated that the analytical strategy provided a feasible alternative for synchronously monitoring the quality of raw herb and the concentration of blood drugs.

Simultaneous determination of aromatic amino acids in different systems using three-way calibration based on the PARAFAC-ALS algorithm coupled with EEM fluorescence: exploration of second-order advantages

A practical analytical method based on intrinsic fluorescence is proposed for simultaneous determination of L-phenylalanine, L-tyrosine, and L-tryptophan in cell culture and human plasma. By using a three-way calibration method coupled with excitation–emission matrix fluorescence, the proposed method successfully achieved quantitative analysis of the three aromatic amino acids in the two different complex systems simultaneously, even in the presence of three unknown, uncalibrated serious interferents. The method needs little preparation by using “mathematical separation” instead of chemical or physical separation, which makes it efficient and environmentally friendly. Satisfactory results have been achieved for calibration, validation, and prediction sets. For phenylalanine, tyrosine, and tryptophan, the calibration ranges are 6.00 to 60.00, 0.40 to 4.00, and 0.10 to 1.00 μg mL−1 respectively. The average spike recoveries (mean ± standard deviation) are 98.5 ± 7.8%, 103.7 ± 6.9%, and 102.3 ± 7.9% respectively. The relative errors are −4.2%, 6.3%, and −0.8% for predicting real contents of phenylalanine, tyrosine, and tryptophan in cell culture respectively. Additionally, we discussed the potential of the three-way calibration method for determining analytes of interest in different systems simultaneously, to further explore the second-order advantages. The paired t-test results indicate that the predicted results between prediction in two systems simultaneously and prediction in a single system individually have no significant difference. The satisfactory results obtained in this work indicate that the use of the three-way calibration method coupled with the EEM array is a promising tool for multi-component simultaneous determination in multiple complex systems containing uncalibrated spectral interferents.

Direct and interference-free determination of thirteen phenolic compounds in red wines using a chemometrics-assisted HPLC-DAD strategy for authentication of vintage year

In the present work, a novel chemometrics-assisted analytical strategy that combines three-way high performance liquid chromatography-diode array detection (HPLC-DAD) data with a second-order calibration method based on the alternating trilinear decomposition (ATLD) algorithm was developed for direct, accurate and simultaneous determination of thirteen phenolic compounds in complex red wine samples without an intricate clean-up step. All analytes were rapidly eluted out (7.5 min) under a simple gradient LC-separation and then detected in a multi-channel UV window. With the aid of the prominent “second-order advantage” of the ATLD algorithm, four common HPLC problems, i.e. solvent peaks, peak overlaps, unknown interferents and baseline drifts, could be mathematically calibrated, enabling “pure signals” of analytes to be extracted out from interference-heavy but information-rich HPLC-DAD profiles. The new strategy could avoid the loss of analytes of interest to significantly improve the analytical accuracy. Validation parameters, i.e. recovery (97.7–104%), precision (RSD < 7.1%), matrix effect, limits of detection (LODs, 0.02–0.27 μg mL−1) and limits of quantitation (LOQs, 0.06–0.82 μg mL−1) of thirteen analytes, were surveyed and further confirmed by the LC-MS/MS method. Based on the indexes of phenolic compositions in wines, pattern recognition methods, i.e. principal component analysis and linear discriminant analysis (PCA-LDA), were applied for distinguishing wines of different storage years, and the discriminant accuracies were higher than 90%, which proved that this chemometrics-assisted HPLC-DAD strategy was an excellent method for direct and accurate determination of phenolic compositions in complex wine samples as well as the authentication of vintage year.

Interference-free analysis of aflatoxin B1 and G1 in various foodstuffs using trilinear component modeling of excitation–emission matrix fluorescence data enhanced through photochemical derivatization

A novel ‘dilute-and-shoot’ analytical strategy coupling a self-weighted alternating normalized residue fitting (SWANRF) algorithm with two-dimensional fluorescence detection enhanced through photochemical derivatization (PD) was proposed in the present work for rapid, simultaneous and accurate quantitative analysis of aflatoxin B1 and G1 in various foodstuffs (including cereals, honey, and edible oil). By coupling the predominant second-order advantage of the SWANRF algorithm with the ultra-sensitivity of fluorescence detection enhanced through off-line photochemical derivatization, the specific quantitative information of both analytes could be successfully extracted from heavily interferential matrices without complicated multi-step purification and chromatographic separation procedures. Consequently, the whole analytical time and expense were significantly decreased, accurate recoveries (with relative standard deviations, RSDs) (93.5 ± 6.6–102.8 ± 4.0% for AFB1, and 96.4 ± 3.6–107.2 ± 6.0% for AFG1) and extremely low limits of detection (LODs) (0.12–0.21 ng mL−1 for AFB1, and 0.27–0.75 ng mL−1 for AFG1) were obtained for analytical foodstuff matrices. In addition, all quantitative results of this proposed strategy were carefully compared with the standard IAC-LC-ESI+-MS method for further confirmation, which proved that SWANRF-EEMs are promising as an alternative analytical strategy for the routine analysis of multiplex aflatoxins, and a theoretical basis for developing portable detecting devices.

Solving signal instability to maintain the second-order advantage in the resolution and determination of multi-analytes in complex systems by modeling liquid chromatography-mass spectrometry data using alternating trilinear decomposition method assisted with piecewise direct standardization.

The application of calibration transfer methods has been successful in combination with near-infrared spectroscopy or other tools for prediction of chemical composition. One of the developed methods that can provide accurate performances is the piecewise direct standardization (PDS) method, which in this paper is firstly applied to transfer from one day to another the second-order calibration model based on alternating trilinear decomposition (ATLD) method built for the interference-free resolution and determination of multi-analytes in complex systems by liquid chromatography-mass spectrometry (LC-MS) in full scan mode. This is an example of LC-MS analysis in which interferences have been found, making necessary the use of second-order calibration because of its capacity for modeling this phenomenon, which implies analytes of interest can be resolved and quantified even in the presence of overlapped peaks and unknown interferences. Once the second-order calibration model based on ATLD method was built, the calibration transfer was conducted to compensate for the signal instability of LC-MS instrument over time. This allows one to reduce the volume of the heavy works for complete recalibration which is necessary for later accurate determinations. The root-mean-square error of prediction (RMSEP) and average recovery were used to evaluate the performances of the proposed strategy. Results showed that the number of calibration samples used on the real LC-MS data was reduced by using the PDS method from 11 to 3 while producing comparable RMSEP values and recovery values that were statistically the same (F-test, 95% confidence level) to those obtained with 11 calibration samples. This methodology is in accordance with the highly recommended green analytical chemistry principles, since it can reduce the experimental efforts and cost with regard to the use of a new calibration model built in modified conditions.

Quantitative investigation of the dynamic interaction of human serum albumin with procaine using a multi-way calibration method coupled with three-dimensional fluorescence spectroscopy

In fluorospectrophotometric studies on protein–drug interactions, the fluorescence intensity of proteins is often vulnerable to interference from ligands or newly produced complexes which exhibit significant fluorescence at the chosen excitation or emission wavelengths. Alternatively, this paper suggests an effective and sensitive method for quantitative determination of free human serum albumin (HSA) in a dynamic interaction system with procaine (PRO) and further investigation of their interaction mechanism using a multi-way calibration method coupled with three-dimensional fluorescence spectroscopy. A second-order calibration method realized the quantitative determination of free HSA in a dynamic system with overlapping spectra even in the presence of an uncalibrated interferent. The quantitative results were used to further calculate the binding parameters, including the binding constant, binding site number, thermodynamic parameters and nature of binding forces. Furthermore, the four-way excitation–emission–temperature–sample data were analyzed to investigate the effect of temperature on the interaction system studied.

Simultaneous and interference-free determination of eleven non-steroidal anti-inflammatory drugs illegally added into Chinese patent drugs using chemometrics-assisted HPLC-DAD strategy

In this work, a smart strategy that combines three-way high performance liquid chromatography-diode array detection (HPLCDAD) data with second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm was proposed for simultaneous determination of eleven non-steroidal anti-inflammatory drugs (NSAIDs) illegally added into Chinese patent drugs and health products. All target analytes were rapidly eluted out within 14.5 min under a simple gradient elution. With the aid of the prominent “second-order advantage” of the ATLD algorithm, three HPLC problems, i.e. peak overlaps, unknown interferences and baseline drift, could be mathematically calibrated, and pure signals of target analytes could be extracted out from heavy-interference but information-rich HPLC-DAD data. The average spiked recoveries for all target analytes were in the range of 95.9%–106.4% with standard deviations lower than 7.5%. Validation parameters including sensitivity (SEN), selectivity (SEL), limit of detection (LOD), limit of quantitation (LOQ) and precisions of intra-day and inter-day were calculated to validate the accuracy of the proposed method, quantitative results were further confirmed by the classic HPLC method, which proved that chemometrics-assisted HPLC-DAD analytical strategy was highly efficient, accurate and green for drug-abuse monitoring of NSAIDs in Chinese patent drugs and health products.

Chemometrics-assisted liquid chromatography-full scan mass spectrometry for simultaneous determination of multi-class estrogens in infant milk powder

In the present study, a smart analytical strategy that combines liquid chromatography-full scan mass spectrometry with the second-order calibration method based on the alternating trilinear decomposition (ATLD) algorithm was developed for the simultaneous determination of seven estrogens in infant milk powders. The seven estrogens were rapidly eluted out within 7.0 min under a simple gradient condition and then, they were detected by mass spectrometry operated in the full scan mode. With the aid of the prominent “second-order advantage” of the algorithm, specific qualitative and quantitative information about the target analytes could be extracted from the complex system even in the presence of considerable peak overlaps, baseline drifts and unknown interferences. The proposed strategy avoided time-consuming and laborious sample pretreatment procedures, resulting in minimal loss of analytes, which improved the analytical accuracy. Average recoveries of the seven estrogens in two spiked infant milk powder samples were in the range of 91.2–104.2% with the relative standard deviations (RSDs) lower than 5.0% (with the exception for 17α-estradiol), and the limits of detection (LOD) ranged from 0.07 to 2.49 ng mL−1. Besides, to further confirm the feasibility and reliability of the proposed method, the same batch of samples was analyzed using the LC-MS/MS method, and the statistical tests showed that no significant difference existed between the two methods, which fully indicated that the proposed strategy could provide satisfactory prediction results in real infant milk powder samples as well as other actual chemical systems.

A flexible and novel strategy of alternating trilinear decomposition method coupled with two-dimensional linear discriminant analysis for three-way chemical data analysis: Characterization and classification

This paper proposes a flexible and novel strategy that alternating trilinear decomposition (ATLD) method combines with two-dimensional linear discriminant analysis (2D-LDA). The developed strategy was applied to three-way chemical data for the characterization and classification of samples. In order to confirm the methodology performances of characterization and classification, a series of simulated three-way data arrays and a real-life EEMs data set involving the characterization and classification of tea samples according to the tea varieties were subjected to ATLD-2DLDA analysis. Further, the obtained results were compared with those obtained by using LDA based on relative concentrations of ATLD (ATLD-LDA), discriminant analysis by N-way partial least square (N-PLS-DA) and 2D-LDA method. For the simulated data sets with respect to different levels of noise and class overlap as well as number of groups, the ATLD-2DLDA always obtains superior classification performances than the ATLD-LDA, 2D-LDA and N-PLS-DA methods. Regarding the real EEMs data set of tea samples, the proposed methodology not only could provide a chemically meaningful model of the data for characterizing the different tea varieties, but also achieved the best correct classification rate (100%) for the test samples, compared with the results of ATLD-LDA (83.9%), 2D-LDA (90.3%) and N-PLS-DA (90.3%). These results demonstrated that the proposed methodology was indeed a feasible and reliable tool for characterization and classification of three-way chemical data arrays in a flexible and accurate manner.