Shou-Xia Xiang

Chemometrics-assisted high performance liquid chromatography-diode array detection strategy to solve varying interfering patterns from different chromatographic columns and sample matrices for beverage analysis

This work reports a chemometrics-assisted high performance liquid chromatography-diode array detection (HPLC-DAD) strategy to solve varying interfering patterns from different chromatographic columns and sample matrices for the rapid simultaneous determination of six synthetic colorants in five kinds of beverages with little sample pretreatment. The investigation was performed using two types of LC columns under the same elution conditions. Although analytes using different columns have different co-elution patterns that appear more seriously in complex backgrounds, all colorants were properly resolved by alternating trilinear decomposition (ATLD) method and accurate chromatographic elution profiles, spectral profiles as well as relative concentrations were obtained. The results were confirmed by those obtained from traditional HPLC-UV method at a particular wavelength and the results of both methods were consistent with each other. All results demonstrated that the proposed chemometrics-assisted HPLC-DAD method is accurate, economical and universal, and can be promisingly applied to solve varying interfering patterns from different chromatographic columns and sample matrices for the analysis of complex food samples.

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.

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.

Quantitative fluorescence kinetic analysis of NADH and FAD in human plasma using three- and four-way calibration methods capable of providing the second-order advantage.

The metabolic coenzymes reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are the primary electron donor and acceptor respectively, participate in almost all biological metabolic pathways. This study develops a novel method for the quantitative kinetic analysis of the degradation reaction of NADH and the formation reaction of FAD in human plasma containing an uncalibrated interferent, by using three-way calibration based on multi-way fluorescence technique. In the three-way analysis, by using the calibration set in a static manner, we directly predicted the concentrations of both analytes in the mixture at any time after the start of their reactions, even in the presence of an uncalibrated spectral interferent and a varying background interferent. The satisfactory quantitative results indicate that the proposed method allows one to directly monitor the concentration of each analyte in the mixture as the function of time in real-time and nondestructively, instead of determining the concentration after the analytical separation. Thereafter, we fitted the first-order rate law to their concentration data throughout their reactions. Additionally, a four-way calibration procedure is developed as an alternative for highly collinear systems. The results of the four-way analysis confirmed the results of the three-way analysis and revealed that both the degradation reaction of NADH and the formation reaction of FAD in human plasma fit the first-order rate law. The proposed methods could be expected to provide promising tools for simultaneous kinetic analysis of multiple reactions in complex systems in real-time and nondestructively.

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.

Chemometrics-assisted determination of amiloride and triamterene in biological fluids with overlapped peaks and unknown interferences

BACKGROUND Amiloride (AMI) and triamterene (TRI) are both potassium-saving diuretics, which are ordinarily used as doping to enhance the performance of athletes in sports. For the similar structures and complex matrices existence, chromatography and extraction are commonly employed to realize the determination of AMI and TRI in biological fluids, which are very time-consuming and laborious. RESULTS A novel method is presented to simultaneous interference-free determination of AMI and TRI in complex biological fluids samples using excitation-emission matrix fluorescence coupled with second-order calibration method based on alternating normalization-weight error algorithm. CONCLUSION The proposed method can obtain accurate qualitative and quantitative information of the analytes, even in the presence of the interference from complex biological fluids, which requires few prior purification and separation procedures.

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.