Second-order advantage achieved by modeling excitation–emission fluorescence matrices affected by inner filter effects using a strategy which combines standardization and calibration: Reducing experimental and increasing analytical sensitivity

A smartphone digital image colorimetric method based on nanoparticles for determination of lamotrigine

Aim: A colorimetric approach for quantification of lamotrigine using spectrophotometric and smartphone image analysis is described in this study. Methods: For full optimization and validation procedures, UV-visible spectroscopy was used, and image analysis was carried out with the help of an app (PhotoMetrix PRO®). Then, as a multivariate calibration method, parallel factor analysis was used for data analysis. Results: The results demonstrated the capacity of these methods to estimate lamotrigine concentrations in the range of 0.1-7.0 μg.ml-1 in exhaled breath condensate, indicating the value of using digital images and smartphone applications in combination with chemometric tools. Conclusion: The image analysis can be superior for its fast and reliable lamotrigine analysis in biological samples.

Application of derivative emission fluorescence spectroscopy for determination of ibuprofen and phenylephrine simultaneously in tablets and biological fluids

Two sensitive, rapid, and accurate derivative emission spectrofluorimetric methods applying zero crossing techniques were developed for simultaneous determination of binary mixtures of ibuprofen (IBU) and phenylephrine hydrochloride (PHE) in pure powder, synthetic mixture and combined tablets. The proposed methods were performed via measuring the intersected drug derivative amplitude of one drug at the zero crossing points for the other one and vice versa. The two methods rely on the measurement of the combined drugs native fluorescence after excitation at 270 nm in methanol directly, followed by differentiation using first (D₁) and second derivative (D₂) techniques. Applying the D₁, IBU was measured quantitatively at 293.1 nm at zero crossing of PHE, on the other side; PHE was measured quantitatively at 300.7 nm at zero crossing of IBU. By the same way, applying the D₂, the wavelengths selected were 303.5 nm for IBU and 312.9 nm for PHE. The concentration plots of derivative fluorescence intensity were rectilinear over the range of 0.5-10 μg/mL and 0.025-0.5 μg/mL for IBU and PHE, respectively. The results obtained with average % recoveries ± RSD are 99.73 ± 0.72 (IBU, D₁), 99.49 ± 0.95 (PHE, D₁), 99.79 ± 0.47 (IBU, D₂), and 99.88 ± 0.34 (PHE, D₂) were in good agreement with the comparison method. The proposed methods offer high sensitivity that enable direct analysis of IBU and PHE in spiked human plasma. The proposed methods were entirely validated in terms of ICH guidelines.

Pharmacokinetic Analysis of Four Bioactive Iridoid and Secoiridoid Glycoside Components of Radix Gentianae Macrophyllae and Their Synergistic Excretion by HPLC-DAD Combined with Second-Order Calibration

An HPLC-DAD method combined with second-order calibration based on the alternating trilinear decomposition (ATLD) algorithm with the aid of region selection was developed to simultaneously and quantitatively characterize the synergistic relationships and cumulative excretion of the four bioactive ingredients of Radix Gentianae Macrophyllae in vivo. Although the analytes spectra substantially overlapped with that of the biological matrix, the overlapping profiles between analytes and co-eluting interferences can be successfully separated and accurately quantified by the ATLD method on the basis of the strength of region selection. The proposed approach not only determined the content change but also revealed the synergistic relationships and the cumulative excretion in vivo of the four ingredients in urine and feces samples collected at different excretion time intervals. In addition, several statistical parameters were employed to evaluate the accuracy and precision of the method. Quantitative results were confirmed by HPLC-mass spectrometry. Satisfactory results indicated that the proposed approach can be utilized to investigate the pharmacokinetics of Radix Gentianae Macrophyllae excretion in vivo.

Calibration, standardization, and quantitative analysis of multidimensional fluorescence (MDF) measurements on complex mixtures (IUPAC Technical Report)

This IUPAC Technical Report describes and compares the currently applied methods for the calibration and standardization of multi-dimensional fluorescence (MDF) spectroscopy data as well as recommendations on the correct use of chemometric methods for MDF data analysis. The paper starts with a brief description of the measurement principles for the most important MDF techniques and a short introduction to the most important applications. Recommendations are provided for instrument calibration, sample preparation and handling, and data collection, as well as the proper use of chemometric data analysis methods.

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.

Single excitation-emission fluorescence spectrum (EEF) for determination of cetane improver in diesel fuel

A highly sensitive spectrofluorimetric method has been developed for the determination of 2-ethylhexyl nitrate in diesel fuel. Usually, this compound is used as an additive in order to improve cetane number. The analytical method consists in building the chemometric model as a first step. Then, it is possible to quantify the analyte with only recording a single excitation-emission fluorescence spectrum (EEF), whose data are introduced in the chemometric model above mentioned. Another important characteristic of this method is that the fuel sample was used without any pre-treatment for EEF. This work provides an interest improvement to fluorescence techniques using the rapid and easily applicable EEF approach to analyze such complex matrices. Exploding EEF was the key to a successful determination, obtaining a detection limit of 0.00434% (v/v) and a limit of quantification of 0.01446% (v/v).