High dynamic range in videodensitometry—a comparative study to classic videoscanning on Gentiana extracts

The advantages of high dynamic range (HDR) imaging in videodensitometry are presented and discussed on the example of Gentiana extract thin-layer fingerprints visualized under 254 nm. An inexpensive microscope camera, together with security surveillance lens, mounted instead of original camera on videodensitometry chamber, allows to grab HDR images with high tonal range using Python scripts and OpenCL library. HDR imaging preserves linearity in whole tonal range and does not destroy details in the brightest and darkest plate regions, so it can be seen as a good alternative to classical videodensitometry. Moreover, the tonemapping of HDR images can be used to present a plate photograph with enhanced visibility of weak spots and other details. Principal component analysis done on nine classic exposures and HDR image proves that HDR image contains the highest amount of extracted information from the thin-layer chromatographic plate.

The influence of the microwave oven on the production of solid culture medium and quality of microbial growth

Numerous cultivation media currently exist, whether selective, non-selective, enrichment or identification. However, they all have a common goal, which is the growth of microorganisms; the constitution and quality of the culture medium must favor it. For this reason, an important factor that directly affects the quality of a culture medium is its production. Thus, this article investigated the use of a microwave oven in the production of Sabouraud dextrose agar (SDA), and the microbial inactivation compared to the autoclave in a microbiology laboratory. The quality of the medium, time exposure, and sterilization potential were performed using fungal strains of Candida spp., Cryptococcus spp., Microsporum spp., and Aspergillus spp. The results showed that the advantages of the use of a microwave oven for the preparation of SDA are practicality, speed, lower energy expense, pH, and constituents preservation of the culture medium, resulting in a richer growth compared to autoclaved SDA. The multivariate analysis of digital images allowed the detection of melanoidins (brownish tone of medium), which are responsible for the negative influence on the microorganisms growth. This research shows the use of the microwave oven as an efficient alternative for the production of the culture medium and maintaining their best quality.

Disposable Paper-Based Biosensors for the Point-of-Care Detection of Hazardous Contaminations-A Review

The fast detection of trace amounts of hazardous contaminations can prevent serious damage to the environment. Paper-based sensors offer a new perspective on the world of analytical methods, overcoming previous limitations by fabricating a simple device with valuable benefits such as flexibility, biocompatibility, disposability, biodegradability, easy operation, large surface-to-volume ratio, and cost-effectiveness. Depending on the performance type, the device can be used to analyze the analyte in the liquid or vapor phase. For liquid samples, various structures (including a dipstick, as well as microfluidic and lateral flow) have been constructed. Paper-based 3D sensors are prepared by gluing and folding different layers of a piece of paper, being more user-friendly, due to the combination of several preparation methods, the integration of different sensor elements, and the connection between two methods of detection in a small set. Paper sensors can be used in chromatographic, electrochemical, and colorimetric processes, depending on the type of transducer. Additionally, in recent years, the applicability of these sensors has been investigated in various applications, such as food and water quality, environmental monitoring, disease diagnosis, and medical sciences. Here, we review the development (from 2010 to 2021) of paper methods in the field of the detection and determination of toxic substances.

Quaternion-based Parallel Feature Extraction: Extending the Horizon of Quantitative Analysis using TLC-SERS Sensing

Quantitative analysis using thin-layer chromatography coupled in tandem with surface-enhanced Raman scattering (TLC-SERS) still remains a grand challenge due to many uncontrollable variations during the TLC developing process and the random nature of the SERS substrates. Traditional chemometric methods solve this problem by sampling multiple SERS spectra in the sensing spot and then conducting statistical analysis of the SERS signals to mitigate the variation of quantitative analysis, while still ignoring the spatial distribution of the target species and the correlation among the multiple sampling points. In this paper, we proposed for the first time a parallel feature extraction and fusion method based on quaternion signal processing techniques, which can enable quantitative analysis using recently established TLC-SERS techniques. By marking three deterministic sampling points, we recorded spatially correlated SERS spectra to constitute an integral representation model of triple-spectra by a pure quaternion matrix. Quaternion principal component analysis (QPCA) was utilized for features extraction and followed by feature crossing among the quaternion principal components to obtain final fusion spectral feature vectors. Support vector regression (SVR) was then used to establish the quantitative model of melamine-contaminated milk samples with seven concentrations (1ppm to 250ppm). Compared with traditional TLC-SERS analysis methods, QPCA method significantly improved the accuracy of quantification by reaching only 7% and 2% quantization errors at 20 and 105 ppm concentration. Validation testing based on reasonable amount of statistic measurement results showed consistently smaller measurement errors and variance, which proved the effectiveness of QPCA method for TLC-SERS based quantitative sensing applications.

An optoelectronic tongue based on an array of gold and silver nanoparticles for analysis of natural, synthetic and biological antioxidants

A colorimetric array, which can discriminate 20 food antioxidants of natural, synthetic and biological groups, is described. It consists of gold and silver nanoparticles that were synthesized using six different reducing and/or capping agents. The function of the array relies on the interaction of the antioxidants with the nanoparticles which causes aggregation or morphological changes. This, in turn, causes a change in the sensors' colors. The array produces a unique combination of colors for each antioxidant. The resulting colorations are determined by recording the absorbances of the arrays at wavelengths of 405, 450, 490 and 630 nm, or by capturing the images with a digital camera. The discriminatory ability of the array is investigated by principle component analysis and hierarchical cluster analysis. The method was applied to quantitative assay of gallic acid, caffeic acid, catechin, dopamine, citric acid, butylated hydroxytoluene and ascorbic acid. The respective limits of detection are 4.2, 13, 53, 6.9, 47, 3.5 and 43 nM, respectively. The simultaneous determination of 5 different antioxidants is achieved utilizing partial least square regression. The root mean square errors for prediction of the test set are 0.0650, 0.0782, 0.811, 0.0206 and 0.135 nM for gallic acid, catechin, butylated hydroxytoluene, dopamine, and ascorbic acid, respectively. This method demonstrates excellent potential for analysis of antioxidants in beverages such as tea and lemon juice. Graphical abstract Schematic of a method for the simultaneous determination of several antioxidants based on changes in the color of gold and silver nanoparticles. The antioxidants cause aggregation and/or morphological changes which can be detected by using both image analysis or by colorimetry.

A time-insensitive colorimetric sensor for the determination of total protein

A newly synthesized cyanine dye was used for sensitive colorimetric determination of total protein in biological fluids.

Self-healing for nanolayered manganese oxides in the presence of cerium(iv) ammonium nitrate: new findings

We used multivariate chemometrics methods to analyze the concentration profiles of cerium(iv) ammonium nitrate and MnO₄⁻during the water oxidation reaction.

pH-independent optical sensing of heparin based on ionic liquid-capped gold nanoparticles

A simple pH-independent optical method for the sensing of heparin, as a biomedically important polyionic drug, based on aggregation of gold nanoparticles (AuNPs) is described. The polyanionic heparin induces the aggregation of positively charged ionic liquid stabilized AuNPs, which results in a shift in the surface plasmon band and a consequent color change of the AuNPs from red to blue. The color change was monitored using UV-vis spectrophotometry and image analysis methods. The aggregation was confirmed by transmission electron microscopic measurements. The degree of aggregation was found to be proportional to the concentration of the added heparin, allowing its quantitative detection. The change in the absorbance and color-value has been used to monitor the concentration of heparin. This optical method can quantify heparin as low as 0.010 μg mL(-1) and the calibration is linear for a wide range of concentration.

Antioxidant activity assay based on the inhibition of oxidation and photobleaching of L-cysteine-capped CdTe quantum dots

Quantum dots (QDs) have recently been the focus of attention of many investigators for development of diagnostic tools in many research areas. In this work, we established a new QD-based assay to evaluate the antioxidant/polyphenolic activity. This assay is based on measurement of the inhibitory effect of the antioxidant/polyphenolic compounds on the UV-induced bleaching of CdTe QDs with L-cysteine capping. QDs exhibited excellent photostability without any UV exposure, while they bleached rapidly under UV irradiation. Generation of reactive oxygen species (ROS) under UV irradiation is probably the main cause of the photobleaching of QDs. By comparing the photostability of QDs in buffer solution in the absence and presence of sodium azide, as a known (1)O(2) quencher, the involvement of (1)O(2) in photobleaching of QDs was confirmed. The photobleaching effect induced by ROS could be reduced in the presence of antioxidant/polyphenolic compounds. We tested several antioxidant/polyphenolic compounds as well as known antioxidants such as trolox and 4 different types of tea. The results obtained by the QD-based assay revealed a very good correlation with the data acquired by Folin-Ciocalteu assay. Furthermore, a deeper understanding of the mechanism and the solution for photobleaching of QDs under UV irradiation might be very meaningful in promoting their clinical applications.