Second-order Calibration Method Research Articles

Green Approach for Simultaneous Quantitative Analysis of Fluoroquinolones in the Environment using Three-Dimensional Fluorescence Coupled with Second-Order Calibration Method.

In this study, a straightforward and quick analytical technique based on the self-weighted alternating trilinear decomposition (SWATLD) algorithm in conjunction with excitation-emission matrix (EEM) fluorescence for the simultaneous determination of the antibiotics levofloxacin (LVFX) and ciprofloxacin (CIP) in environmental waters and sediments was developed. This approach completely utilizes the "second-order advantage" and inherits the great sensitivity of classic fluorescence. It replaces or improves the conventional "physical/chemical separation" with "mathematical separation", enabling direct and quick quantification of the target analytes even in the presence of unknown interferences, greatly streamlining sample preparation procedures, consuming less solvent, and speeding up analysis time, and allows successful and environmentally friendly solution of overlapping fluorescence spectra of multiple components in complicated environmental matrices without cumbersome pretreatment steps and complex and expensive instrumentation. The limits of detection varied between 0.34 and 0.67 ng mL- 1, and the average spiking recoveries of LVFX and CIP in water and sediment ranged from 97.6 to 107.7% with relative standard deviations lower than 6.6%. The developed method shows the reliability of the technology and the ability to quickly detect trace antibiotics in lake water even in the presence of unidentified interferents.

The advantages behind the efforts of performing higher-order calibration methods – A case study

BackgroundAcross numerous investigations delved into second- and higher-order data, an undoubted finding emerges: models based on such data can effectively exploit the second-order advantage. However, whether further benefits can be achieved by modeling data of higher dimensions remains a subject of inquiry. In this regard, a prevailing question emerges in third-order data-based applications regarding the fundamental need to increase the data dimension and, hence, the data analysis complexity. This study aims to provide meaningful evidence to support the advantages inherent in employing third-order calibration methods despite the associated efforts, such as instrumentation and data analysis complexity. ResultsThis study compares the analytical performance achieved using a third-order calibration method with those obtained from most of the possible second-order calibration approaches derived from the same dataset. This work delves into the structural properties of the data, modeling limitations, and analytical characteristics associated with each model. Additionally, it includes a comprehensive statistical comparison of the models based on their recovery performance. First, the outcomes demonstrate the importance of capitalizing on all available chemical information and harnessing the full potential of data to maximize its benefits. Moreover, the results provide evidence that asserts the fact that third-order calibration methods bring the opportunity to increase the number of analytes that can be simultaneously determined, notwithstanding the need for more tedious experimental protocols, specialized instrumentation (sometimes), and quite complex data analysis. Significancethis research marks the first extensive comparison of third-order data calibration models with possible second-order calibration methods. Moreover, this work pioneers the incorporation of highly challenging non-multilinear data. The advancements detailed in this study emphasize the advantages of third-order data acquisition, notwithstanding the need for more tedious experimental protocols, specialized instrumentation (sometimes), and quite complex data analysis.

Third-order calibration applied to process surfactant-modulated excitation-emission matrix four-way fluorescence data for the direct determination of four polycyclic aromatic hydrocarbons in oilfield produced water

Fluorescence spectroscopy is a powerful tool to determine polycyclic aromatic hydrocarbons (PAHs) owing to the strong endogenous fluorescence of these compounds. However, the presence of unknown interferences and overlapped spectra hinders the accurate determination of PAHs in oilfield produced water. Moreover, surfactants frequently coexist in oilfield produced water and will seriously affect the fluorescence signals of PAHs. Herein, a new methodology applying third-order calibration to process four-way (4D) fluorescence data was proposed to solve these problems and achieve accurate determination of pyrene, fluorene, phenanthrene, and fluoranthene as an example in oilfield produced water. The methodology is based on excitation-emission matrix fluorescence modulated by different concentrations of sodium dodecyl benzene sulfonate (SDBS) in the analyzed samples. The 4D fluorescence data were processed by third-order calibration methods including four-way parallel factor analysis (4-PARAFAC) and alternating weighted residue constraint quadrilinear decomposition (AWRCQLD), and the results were compared with those of second-order calibration methods. It was proved that third-order calibration was capable of accurately identifying and quantifying PAHs together with SDBS in oilfield produced water, which has better quantitative results and figures of merit compared to second-order calibration. This study provided a new approach to generating 4D fluorescence data and opened up an avenue for the accurate determination of PAHs in complex oilfield produced water with surfactants.

Fabrication of a novel molecularly imprinted biosensor assisted by higher-order calibration methods and a computer-generated experimental design for determination of thyroglobulin in the presence of thyroxine and triiodothyronine as uncalibrated interference

In this work, a novel electrochemical biosensor was fabricated by modification of a rotating glassy carbon electrode (GCE) with fullerene C60-ionic liquid (C60-IL), and electrochemical synthesis of molecularly imprinted polymers (MIPs) on its surface for selective and sensitive determination of thyroglobulin (TG) in the presence of thyroxine (T4) and triiodothyronine (T3) as uncalibrated interference. The MIPs were synthesized onto the surface of electrochemically activated C60-IL/GCE by electropolymerization of 4-aminothiophenol, methacrylic acid, ethylene glycol dimethacrylate (as cross linker), and TG (as template molecule). By incubation of the biosensor in TG solution, the TGs were entrapped within the pathways of the MIPs, and by incubation of the biosensor in electrochemical probe solution, the pathways for reaching the probe molecules to biosensor were decreased which caused the hydrodynamic differential pulse voltammetric (HDPV) response of the biosensor to be decreased. The effects of experimental parameters on response of the biosensor were optimized by a quadratic central composite design, and at optimized conditions determination of TG in the presence of T4 and T3 as uncalibrated interference was performed. The selectivity of the biosensor was further assisted by supporting the biosensor response with the help of second-order calibration methods and generation of second-order HDPV data with the aim of exploiting second-order advantage. Second-order calibration models were developed by MCR-ALS, PARAFAC2, N-PLS/RBL, and U-PLS/RBL with the aim of choosing the best model for assisting the biosensor for selective determination of the TG in the presence of T4 and T3 as uncalibrated interference. The results confirmed the best performance was observed for the biosensor assisted by PARAFAC2 in both synthetic and real matrices which was comparable with HPLC-UV as the reference method, and can be suggested as an alternative method for chromatographic methods.

Chemometrics-assisted excitation-emission matrix fluorescence spectroscopy for real-time migration monitoring of multiple polycyclic aromatic hydrocarbons from plastic products to food simulants

Polycyclic aromatic hydrocarbons (PAHs), as a class of organic pollutants that have attracted much attention, are likely to be formed with the production and processing of plastic products, and they may migrate from contaminated plastic products to food, causing the risk of poisoning or cancer. In this study, migration tests were carried out on disposable plastic products for food contact, and a novel strategy that combines excitation-emission matrix (EEM) fluorescence spectroscopy with the advanced second-order calibration method based on the three-direction resection alternating trilinear decomposition (TDR-ATLD) algorithm was used to monitor the migration of three PAHs anthracene (ANT), pyrene (PYR), and phenanthrene (PHE) from the plastic products to food simulants in real-time. With the “second-order advantage”, even if the fluorescence spectra of the target analytes overlapped seriously, and other unknown substances migrated from the plastic products to food simulants, accurate qualitative and quantitative results were still obtained by the proposed method. In the static system, the coefficient of determination (R2) of the three PAHs within the calibration range were all greater than 0.99, and the average spiked recoveries were 99.5-107.1%, with the standard deviation lower than 8.9%. The figures of merit (FOMs) and intra- or inter-day precision also showed good feasibility and reliability of the method. In the simulation study of the migration kinetic process, three PAHs can be quantified in real-time in complex matrix, then the related migration equations were established. The results indicate that the proposed method can be used for real-time migration quantitative monitoring of PAHs, providing a potential and available method for the study of the migration kinetics of hazardous substances from food contact materials to food or food simulants.

An intelligent and novel electrochemical biosensor for simultaneous enzymatic biosensing of cholesterol and glucose in the presence of uric acid based on first-and second-order calibration methods

In this work, for the first time, a novel electrochemical biosensor was fabricated based on modification of a glassy carbon electrode with multi-walled carbon nanotubes-ionic liquid (MWCNTs-IL) which was used as a platform to the synthesis of molecularly imprinted polymers having glucose (GL), glucose oxidase (GO), cholesterol (CL), cholesterol oxidase (CO), cholesterol esterase (CE), horse radish peroxidase (HRP), and uric acid (UA) as template molecules. For simultaneous biosensing of GL and CL, the biosensor (MIPs/MWCNTs-IL/GCE) was incubated with the enzymes and then, it was individually incubated with GL and CL. Response of the biosensor was based on the reduction of the hydrogen peroxide produced from enzymatic reactions. Individual incubation of the biosensor with GL and CL generated two very similar peaks while its incubation with both GL and CL generated a single peak which needed to be assisted by first- and second-order calibration methods to choose the best method. Second-order hydrodynamic differential pulse voltammetric data were generated and modeled by MCR-ALS, PARASIAS, and PARAFAC2 to simultaneous determination of them in the presence of UA as uncalibrated interference based on exploiting second-order advantage. Amperometric responses of the biosensor to GL and CL were also calibrated and assisted by first-order calibration methods for simultaneous determination of GL and CL in the presence of UA based on exploiting first-order advantage. The result confirmed that the biosensor assisted by second-order data modeled by MCR-ALS showed the best performance for simultaneous determination of CL and GL in the presence of UA as uncalibrated interference in both synthetic samples and human serum samples which was comparable with HPLC-UV as the reference method. It should be noted the biosensor was able to simultaneous determination of CL and GL in the ranges of 0.5–15 pM and 1–18 pM with limits of detection of 0.81 pM and 0.23 pM, respectively, and response of the biosensor was stable, selective, ultrasensitive, repeatable, and reproducible. This work as the first report chemometric assisted enzymatic biosensing of GL and CL can be continued to develop more projects for biomedical purposes.

Interference-free and simultaneous quantification of three breast cancer-related DNAs in multiple biological fluids using excitation-emission matrix fluorescence spectroscopy combined with second-order calibration method

Breast cancer is the leading cause of cancer deaths in women worldwide. Quantitation of breast cancer-related biomarkers facilitates cancer research, diagnosis, and prognosis. However, few studies have determined multiple biomarkers associated with breast cancer simultaneously. We presented a chemometrics-enhanced excitation-emission matrix fluorescence (EEMF) spectroscopy strategy for the simultaneous quantification of three biomarkers associated with breast cancer. Three molecular beacons (MBs) were designed to detect the target analytes in complex biological systems. Even in the existence of unexpected interferences and seriously overlapped fluorescent peaks, the alternating normalization-weighted error (ANWE) method can accurately resolve the spectral profiles and provide satisfactory qualitative and quantitative results. The proposed strategy showed good linearity (r ≥ 0.9971) and satisfactory average spiked recoveries (92.3%-107.8%). Furthermore, figures of merit (FOM), precision, and the elliptic joint confidence region (EJCR) test were applied to evaluate the feasibility and reliability of the method. These results demonstrate that the proposed strategy has the advantages of being simple, rapid, cost-effective, and anti-interference. Therefore, this study provides a new pathway for the simultaneous determination of multiple cancer-related biomarkers in complex matrices, which is expected to bring a valuable reference for cancer research and disease diagnosis.

A novel quadruple templates molecularly imprinted polymer electrochemical sensor assisted by second-order calibration methods for detection of Sustanon abuse

Sustanon (SUS) consists of testosterone propionate (TP), testosterone phenylpropionate (TPP), testosterone isocaproate (TIC) and testosterone decanoate (TD) which is generally used as a medication to treat the testosterone deficiency in men. Misuse of SUS to enhance the ability of the athletes can be a very serious risk for their health which is discouraged. Therefore, the main aim of this work was based on developing a novel biosensing system for determination of different types of testosterones in SUS to monitor it. A rotating glassy carbon electrode (GCE) was modified with fullerene C60-multiwalled carbon nanotubes-ionic liquid (C60-MWCNTs-IL) and used as the working electrode for recording second-order hydrodynamic square wave voltammetric (hydrodynamic SWV) data at different step potentials including 0.02, 0.025, 0.03, 0.035, 0.04 and 0.045 V as a sensitive method. Different types of testosterones were extracted and preconcentrated by quadruple templates molecularly imprinted polymers (QTMIPs) and they were determined by C60-MWCNTs-IL/GCE. The testosterones showed severely overlapped peaks at the surface of C60-MWCNTs-IL/GCE which were resolved by three-way calibration based on second-order hydrodynamic SWV data. Therefore, a novel sensor assisted by QTMIPs and second-order calibration methods was developed which had a very good performance for the analysis of synthetic and real matrices in simultaneous determination of TP, TPP, TIC and TD with aim of monitoring the SUS.

A novel triple templates molecularly imprinted biosensor assisted by second-order calibration methods based on generation of second-order hydrodynamic linear sweep voltammetric data for simultaneous biosensing of insulin, proinsulin and C-peptide: Application to comparing PARAFAC2 and PARASIAS

In this work, a novel, very sensitive and selective electrochemical biosensor was fabricated based on excellent modification of a thick-film boron doped diamond electrode (TFBDDE) for simultaneous biosensing of insulin (IN), proinsulin (PIN) and C-peptide (CPT). The TFBDDE was modified with multiwalled carbon nanotubes-fullerene C60-graphene-ionic liquid (MWCNTs-C60-GR-IL). Then, IN, PIN and CPT as template molecules were mixed with N-methacryloyl-(L) 3-histidine methyl ester, 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate, and drop-casted onto the sensor surface for the synthesis of triple templates molecularly imprinted polymers (TTMIPs) by ultraviolet polymerization method. After individual immersion of the biosensor with IN, PIN and CPT, its hydrodynamic linear sweep voltammetric (HLSV) responses were recorded. Immersion of the biosensor in a ternary solution of IN, PIN and CPT generated a single HLSV response which forced us to use multi-way calibration methods for simultaneous determination of IN, PIN and CPT based on generation of second-order HLSV data at different step potentials. Building three-way calibration models by PARAFAC2 and PARASIAS was performed, and the results confirmed superiority of PARASIAS than PARAFAC2 in simultaneous determination of IN, PIN and CPT in the ranges of 1–16 pM, 4–25 pM and 8–88 pM, respectively, in both artificial and real human serum samples. According to the results obtained in this work, the biosensor assisted by PARASIAS can be used as a reliable device for simultaneous determination of IN, PIN and CPT in serum samples.

Piecewise direct standardization assisted with second-order calibration methods to solve signal instability in high-performance liquid chromatography-diode array detection systems

In this paper, in order to solve signal instability of high-performance liquid chromatography-diode array detection (HPLC-DAD) data and maintain the second-order advantage, this work proposed piecewise direct standardization (PDS) assisted with second-order calibration methods to analyze two different complex HPLC-DAD data with signal instability, including simulated HPLC-DAD data and the data of pesticide residues in saffron. Accurate quantitative results of target analytes can be obtained by PDS combined with alternating trilinear decomposition algorithm (ATLD) and alternating trilinear decomposition assisted multivariate curve resolution algorithm (ATLD-MCR) in the presence of signal instability with time shifts and changes of peak shape. Quantitative results of the model after calibration transfer are better than those of the model established by calibration sets and prediction sets with signal instability using ATLD algorithm and ATLD-MCR algorithm under different situations. Meanwhile, t-test was used to judge whether there are significant differences between these quantitative results of models. The performances of MCR-ALS algorithm were compared with that of PDS-ATLD method and PDS-ATLD-MCR method and the proposed methods have greater potential in dealing with the case of signal instability with time shifts and changes of peak shape. In a word, this methodology can reduce the number of calibration samples for recalibration and modeling, improve the efficiency of experiment, conform to the principle of green chemistry, and obtain satisfactory quantitative results in the presence of signal instability with time shifts and changes of peak shape.

A novel and highly selective aptamer-based sandwich-type biosensor assisted by second-order calibration methods for efficient biosensing of Streptococcus pneumoniae

In this article, a novel electrochemical biosensor was fabricated based on modification of a screen printed carbon electrode (SPCE) with 5′-GTT GGAATG CTG AGA AAA AAA AAA-Thiol-C3-3' (CAP)/lead nanoparticles/fullerene C60-multiwalled carbon nanotubes with the aim of biosensing of the Streptococcus pneumoniae (SPP). Single stranded DNAs extracted from the SPPs were used as targets (TAGs) which were captured by the CAPs, and by 5′-6-Fam-AAAAAC GGT TGAACT GAT TG-3' (APT) formed an APT-TAG-CAP sandwich assay for the detection of single stranded DNAs of the SPP. The differential pulse voltammetric (DPV) response of the biosensor immersed into the electrochemical probe solution was changed upon formation of the APT-TAG-CAP sandwich assay which was used to the determination of the number of the SPPs. In order to increase the selectivity of the biosensor towards determination of the number of the SPPs, it was assisted by second-order calibration methods based on generation of second-order DPV data, data pre-processing, trouble shooting, and data analysis by U-PLS/RBL (sensitivity: 22 ​μA ​(ng/μL)-1 single stranded DNA/22 ​μA (283 SPPs)-1 and LOD: 0.1 ​ng/μL single stranded DNA/28 SPPs) and N-PLS/RBL as well-known second-order algorithms. The biosensor assisted by U-PLS/RBL showed a better performance towards determination of the SPP whose performance was comparable with the NanoDrop method as reference method.

Simultaneous determination of nine tyrosine kinase inhibitors in three complex biological matrices by using high-performance liquid chromatography-diode array detection combined with a second-order calibration method.

An intelligent chemometric second-order calibration method called alternating trilinear decomposition- assisted multivariate curve resolution combined with high-performance liquid chromatography-diode array detection was used for the simultaneous quantification of nine tyrosine kinase inhibitors in three complex biological systems. The method allows simultaneous quantification of the components in different biological matrices without the need for cumbersome pre-treatment steps, complex elution conditions, and complete peak separation. Even with the varying time shift, severe peak overlap, and various unknown interferences, the proposed method can extract pure chromatographic and spectroscopic information for each analyte, while providing accurate qualitative and quantitative results of nine common tyrosine kinase inhibitors in three different biological matrices. All the drugs were eluted in 7 min. The results showed that the nine drugs in each matrix showed good linearity (r>0.984) in the calibration range with a root mean square error of calibration less than 0.9μg/mL. The average spiked recoveries of the target analytes were all in the range of 83.4-110.0%, with standard deviations less than 9.0%. Finally, the classical method was used to validate the proposed method. In comparison to the traditional method, the proposed strategy is accuracy, simultaneous, and interference-free.

Quantitative analysis of carbaryl and thiabendazole in complex matrices using excitation-emission fluorescence matrices with second-order calibration methods

In this paper, a fast and efficient analytical strategy was proposed that chemometrics assisted with excitation-emission fluorescence matrices was used to quantify carbaryl (CAR) and thiabendazole (TBZ) in peach, soil and sewage. Even if there are serious overlapped peaks and unknown interferences in fluorescence analysis, the second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm can be used to analyze CAR and TBZ in peach, soil and sewage. The recoveries of CAR and TBZ in peach are 110.4% and 99.7% and their standard deviations are lower than 2.1% and 0.3%, respectively. In addition, the accuracy of the method was assessed with figures of merit as well as intra-day and inter-day precision. The limit of detection, the limit of quantitation of CAR and TBZ in peach are 1.2 ng mL−1 and 0.3 ng mL−1, 3.5 ng mL−1 and 0.8 ng mL−1, respectively. And their root-mean-square error of prediction are 17.0 ng mL−1 and 5.0 ng mL−1 and there are high sensitivity and selectivity in this method. Meanwhile, the results obtained by ATLD algorithm were compared with those obtained by the self-weighted alternate trilinear decomposition algorithm (SWATLD) and the parallel factor analysis (PARAFAC) algorithm, and statistical methods such as the t-test, F-test and the elliptic joint confidence region were used to evaluate for analysis. There were no significant differences among these methods. At last, high performance liquid chromatography-fluorescence detector (HPLC-FLD) was used to evaluate the accuracy and reliability of the proposed method. These results are satisfactory and indicate that the proposed method can be used for accurate and rapid determination of pesticides in complex systems.

Determination of melamine in milk by fluorescence spectroscopy and second-order calibration

Melamine is a compound commonly used in the manufacturing of plastic and flame retardant products, but due to its solubility on water and high nitrogen content, it is also used to adulterate milk to mask adulteration by dilution in protein content tests. This work proposes a quick method using excitation-emission matrix (EEM) fluorescence spectroscopy and second-order calibration methods (PARAFAC and U-PLS/RBL) for the identification and quantification of melamine in milk. The proposed method uses a single clean-up step with acetic acid, resulting in a quick, low-cost, and environmentally friendly procedure, in agreement with green chemistry principles. Both PARAFAC and U-PLS/RBL were capable of detecting melamine in milk above 120.6 and 146.5 ppm respectively, adequate for adulterations above 2% in volume, with RMSEPs of 68.6 and 81.9 ppm, respectively.

Three efficient chemometrics assisted fluorimetric detection methods for interference-free, rapid, and simultaneous determination of ibrutinib and pralatrexate in various complicated biological fluids

In this study, a series of green, interference-free fluorimetric detection methods of the excitation-emission matrix coupled with the second-order calibration methods were proposed for the determination of ibrutinib and pralatrexate in various complicated biological fluids. The second-order advantage of the proposed method can overcome the problem of poor selectivity caused by the wide spectra of the fluorescence method. Even in the presence of uncalibrated interferences and severe peak overlap, the signal of pure substance and accurate quantitative results were still obtained. The average recoveries of the three methods were 94.5–104.9% for Alternating Trilinear Decomposition (ATLD) algorithm, 95.5–105.8% for Alternating Normalization Weighted Error (ANWE) algorithm and 94.4–105.7% for Parallel Factor Analysis (PARAFAC) algorithm, respectively. For ATLD, ANWE and PARAFAC, the relative standard deviations (RSD) were lower than 9.2%, 6.8% and 9.2%, and the RMSEPs were less than 8.1, 8.4 and 8.6 ng mL−1, respectively. In addition, the elliptic joint confidence region (EJCR) was adopted to further prove the accuracy of the three methods. The results showed that the three methods can accurately be quantified without significant difference. Good figures of merit parameters were also obtained. Among them, the limit of detection (LOD) and limit of quantification (LOQ) of ibrutinib and pralatrexate were in the range of 0.11–0.76 ng mL−1 and 0.21–1.12 ng mL−1, respectively, which were lower than the corresponding blood concentrations. These results indicate that the proposed method provides a promising, alternative and universal analysis strategy for clinical drug monitoring.

Rapid determination of sulfamethoxazole and trimethoprim illegally added to health products using excitation-emission matrix fluorescence coupled with the second-order calibration method.

In this work, a simple and fast analytical method based on a self-weighted alternating trilinear decomposition (SWATLD) algorithm coupled with excitation-emission matrix (EEM) fluorescence was developed for the simultaneous determination of sulfamethoxazole (SMZ) and trimethoprim (TMP) illegally added to health products. With the second-order advantage, the proposed method obtained satisfactory results in the presence of peak overlap and unknown interferences. The analysis time for a single sample is only 0.8 minutes. The average spiked recoveries of SMZ and TMP in three health product spiked samples were in the range of 91.0-106.2% and 86.8-107.8%, respectively. The relative standard deviations (RSDs) were lower than 8.6%. In addition, verification parameters including sensitivity (SEN), selectivity (SEL), the limit of detection (LOD), the limit of quantification (LOQ), intra-day precision, and inter-day precision were calculated, and the results show that the proposed method is feasible. The quantitative results of the proposed method were further confirmed by the LC-MS/MS method, which proved that the proposed method was efficient and green for drug-abuse monitoring of SMZ and TMP in health products.

Interference-free analysis of multi-class preservatives in cosmetic products using alternating trilinear decomposition modeling of liquid chromatography diode array detection data

In this work, a simple and effective strategy was proposed based on the combination of liquid chromatography diode array detection (HPLC-DAD) with second-order calibration method for fast and simultaneous determination of twelve preservatives in a variety of cosmetic products. The twelve preservatives were completely eluted out within 10.5 min under a simple sample preparation step. The proposed method shows “second-order advantage”, which enables one to accurately quantify the twelve preservatives in complex cosmetics in the presence of co-eluting chromatographic peaks and diverse unknown interferences. As a result, the consumption of organic solvents was markedly reduced and analysis time was greatly shortened. All target analytes showed good linearity in the calibration range with root-mean-square error of calibration (RMSEC) less than 0.84. The average spiked recoveries for all target analytes were in the range of 93.9%-110.5% with standard deviations less than 9.3%. In addition, analytical figures of merit were calculated to validate the performance of the proposed method. All these results demonstrated that the developed strategy was fast, green and accurate. Consequently, it could be used as an attractive alternative for the determination of multiple preservatives in complex cosmetic samples.

Fast high-performance liquid chromatography quantification of ten phenolic acids in honey using chemometric second-order calibration method

This study aims at the determination of ten phenolic acids in honey using high-performance liquid chromatography-diode array detection (HPLC-DAD) combined with a chemometric second-order calibration method. First, the accuracy of the model was investigated by analysis of the calibration samples and validation samples. Satisfactory results were obtained; the ten phenolic acids exhibited good linearity, and the correlation coefficient (R) was in the range 0.9982-0.9999, with average recoveries of 97.6% to 101.1%, which proved that the model was stable and reliable. Second, the types and operating conditions of the SPE columns were determined by experiments using simulated honey; HLB column was selected, washed with 0.1%(v/v) formic acid aqueous solution, and eluted with methanol. Finally, the phenolic acid contents in jujube flower honey were determined under the optimum conditions for simulated honey. The recoveries of the analytes were 62.1%-93.8%, which met the requirements considering the variety of target analytes and the complexity of the honey substrate. In addition, the efficiency of the method was validated by figures of merit and statistical parameters, including sensitivity (SEN), selectivity (SEL), root-mean-square error of prediction (RMSEP), limit of detection (LOD), and limit of quantification (LOQ); the obtained results were satisfactory. This method is simple, fast, and accurate, and it can be used for the quantitative analysis of the target analytes in complex substrates.

A chemometric comparison of different models in fluorescence analysis of dabigatran etexilate and dabigatran.

In this paper, a simple, rapid, low-cost and potential method was established for the simultaneous quantitative analysis of dabigatran etexilate (DABE) and dabigatran (DAB) in spiked biological fluids. It combined excitation-emission matrix fluorescence (EEMF) with different second-order calibration methods, including the self-weighted alternating normalized residue fitting (SWANRF) algorithm based on trilinear decomposition model, the multivariate curve resolution - alternating least-squares (MCR-ALS) based on bilinear decomposition model and the unfolded partial least-square coupled with residual bilinearization (U-PLS/RBL) based on latent variables model. The proposed method showed "second-order advantage", that is, satisfactory quantitative results were successfully obtained even in the presence of unknown interferences and serious spectral overlap. The recoveries of DABE and DAB in spiked biological fluids were 91.7%-101.7% for SWANRF, 95.9%-117.8% for MCR-ALS, 83.0%-109.6% for U-PLS/RBL, respectively. Figures of merit and other statistical parameters were also calculated to assess the performance of the proposed method. Moreover, the modeling procedures and characteristics of three different models in EEMF analysis were discussed and compared.

Chemometrics-enhanced HPLC–DAD as a rapid and interference-free strategy for simultaneous quantitative analysis of flavonoids in Chinese propolis

In this paper, the application of chemometrics coupled with high-performance liquid chromatography-diode array detection (HPLC–DAD) for the rapid and sensitive quantitative analysis of seven flavonoids in the raw and purified propolis samples was investigated. The objective of this paper was to receive a successful resolution of the complex propolis matrix with minimum experimental time (3.5 min) when appearing unknown interferences, highly overlapping peaks, time and baseline drifts among chromatograms. First, the validation samples contained seven flavonoids at five levels, helped to understand and interpret the features of the second-order calibration method based on the alternating trilinear decomposition (ATLD) algorithm. Second, the experimental data were studied for the simultaneous determination of flavonoids in the raw and purified propolis samples using the function of "mathematical separation" of ATLD algorithm. Except for myricetin (MY), the average recoveries of other analytes were 95.79–105.82% for the raw propolis samples, 94.41–108.06% for the purified propolis samples. In addition, the limit of detection (LOD, 0.01–0.20 μg mL−1), limit of quantification (LOQ, 0.03–0.60 μg mL−1), sensitivity (SEN, 15.97–184.31 mL μg−1), selectivity (SEL, 0.16–0.76) and root-mean-squared error of prediction (RMSEP, 0.29–1.64 μg mL−1) of the proposed method, demonstrated that all the target analytes have good sensitivity, low detection limit. According to the experimental results, the total content of flavonoids in purified propolis is about twice that in raw propolis, which is consistent with the actual situation. This analytical strategy will be extremely promising for the identification and quantification of analytes studied in the complex samples.