Simultaneous quantitative analysis of K+ and Tl+ in serum and drinking water based on UV-Vis spectra and chemometrics

Quantitative and qualitative analyses of metal ions in food and water by using a multicolor sensor array and chemometrics

Rapid and accurate detection of toxic metal ions is the key to combating food contamination and environmental pollution. In sensor arrays, gold nanoparticles play a crucial role in monitoring metal ions based on surface plasmon resonance. However, identifying metal ions with unknown concentrations in a complex system through this assay is difficult because of its monotonous color change and weak anti-interference ability. To overcome these limitations, a sensitive, flexible, low-cost, and multicolor sensor array was designed herein. The applicability of the sensor array for the qualitative and quantitative analyses of metal ions in food and water was also verified. The developed sensor array could classify 14 metal ions (Cu²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Cr³⁺, Co²⁺, Ba²⁺, K⁺, Tl⁺, Pb²⁺, and Hg²⁺) of unknown concentration with an accuracy of 100%. In addition, partial least squares models were established to quantify Tl⁺, Pb²⁺, and Hg²⁺ in water and rice samples, with square correlation coefficients (R²) of 0.9991, 0.9742, and 0.9731, respectively. This method can be used for accurate quantitative and qualitative analyses of heavy metal ions in water and food.

Analysis of serum total bilirubin content based on dual-position joint spectrum of "M plus N" theory and the logarithmic method

At present, in the chemical quantitative analysis of complex solutions based on spectroscopy, the accuracy of the content analysis of complex solution is difficult to meet the requirements due to the overlapping spectral lines, low signal-to-noise ratio, and scattering characteristics of various components of complex solution. In this paper, the logarithmic method is used to preprocess the spectral data in the spectral preprocessing stage, and the two-position and multi-mode joint spectral strategy of "M plus N" theory is applied to the quantitative analysis of serum components. The serum samples are illuminated by dual-position ultraviolet LED light source, and the two spectra of the vertical position and the coaxial facing position of the light source and the optical fiber are collected respectively. Then the partial least square (PLS) method was used to establish models to analyze the concentration of total bilirubin in serum by the spectrum of vertical position, the spectrum of coaxial facing position, and the spectrum of the combination of the former two. Among the experimental results, the model established by the combination of the two spectra collected by two positions has a good result. The correlation coefficient of all samples predicted by this model is 0.971223, and the root mean square error is 1.96645 μmol/L. This study shows that the method of the logarithmic, collecting spectra and analyzing the composition content of complex solutions by using the multi-location and multi-mode strategy of "M + N" theory can effectively improve the prediction accuracy of the model and has practical significance for the chemical quantitative analysis of complex solutions based on spectroscopy.

Dual dye-labeled G-quadruplex aptasensor for detection of thallium(I) using ratiometric fluorescence resonance energy transfer

A fluorescent probe was developed for ratiometric detection of thallium ions in mineral water samples by modifying a G-rich aptamer (PS2.M - 7) with a fluorescence donor (Cyanine-3, Cy₃) and a quencher (Cyanine-5, Cy₅). The probe had a random coil structure that changed into a G-quadruplex structure upon binding with Tl⁺. This change in structure decreased the distance between the donor and acceptor moieties, which resulted in fluorescence resonance energy transfer between Cy₃ and Cy₅. Under optimized conditions, the limit of detection and linear concentration range for Tl⁺ were 30.1 μM (3σ) and 10 μM-10 mM (R² = 0.9981), respectively. This simple and cost-effective fluorescence sensor provided satisfactory results for detection of thallium ions in spiked mineral water samples.

Refractive index-assisted UV/Vis spectrophotometry to overcome spectral interference by impurities

A major challenge hindering the application of techniques like UV/Vis spectrophotometry in determining concentration is spectral interference from contaminants. Since molar absorptivities vary significantly, even minuscule amounts of specific contaminants may cause relatively large errors in UV/Vis spectrophotometry based quantification. Current methods to deal with this are slow, cost-intensive, or ineffective for unknown interferents. We propose constrained refractometry as an expedient technique to aid UV/Vis spectrophotometry, avoiding large errors due to spectral interference. Based on a modified Lorentz Lorenz equation, the technique helps not only in detecting and reducing error from unknown contaminants but also in identifying the significant impurity. Experimental results show a significant reduction of error in concentration determination even for multiple unknown interfering contaminants.

Application of Chemometrics in Biosensing: A Review

The field of biosensing is rapidly developing, and the number of novel sensor architectures and different sensing elements is growing fast. One of the most important features of all biosensors is their very high selectivity stemming from the use of bioreceptor recognition elements. The typical calibration of a biosensor requires simple univariate regression to relate a response value with an analyte concentration. Nevertheless, dealing with complex real-world sample matrices may sometimes lead to undesired interference effects from various components. This is where chemometric tools can do a good job in extracting relevant information, improving selectivity, circumventing a non-linearity in a response. This brief review aims to discuss the motivation for the application of chemometric tools in biosensing and provide some examples of such applications from the recent literature.