Chemical studies of anthocyanins: A review

The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.

https://journals.sagepub.com/doi/pdf/10.1366/11-06574

Laser-induced breakdown spectroscopy (LIBS), part II: review of instrumental and methodological approaches to material analysis and applications to different fields.

We propose a data mining approach to predict human wine taste preferences that is based on easily available analytical tests at the certification step. A large dataset (when compared to other studies in this domain) is considered, with white and red vinho verde samples (from Portugal). Three regression techniques were applied, under a computationally efficient procedure that performs simultaneous variable and model selection. The support vector machine achieved promising results, outperforming the multiple regression and neural network methods. Such model is useful to support the oenologist wine tasting evaluations and improve wine production. Furthermore, similar techniques can help in target marketing by modeling consumer tastes from niche markets.

/pdf/modeling-wine-preferences-by-data-mining-from-3fxk2fcdej.pdf

Modeling wine preferences by data mining from physicochemical properties

Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.

/pdf/label-free-impedance-biosensors-opportunities-and-challenges-3b721lxxqy.pdf

Label-Free Impedance Biosensors: Opportunities and Challenges.

Applications of solid-phase microextraction in food analysis.

The extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspace-SPME (HS/SPME) and multiple-headspace-extraction-SPME (MHE/SPME). The aromagrams obtained by HS/SPME-CGC were evaluated with chemometrical methods for the varietal classification of wines.

Use of solid-phase microextraction-capillary-gas chromatography (SPME-CGC) for the varietal characterization of wines by means of chemometrical methods

Modern strategies in the treatment of Diabetes mellitus require frequent blood glucose tests. Near-infrared spectroscopy [NIR] is considered to be a method for non-invasive blood glucose testing. The present study evaluated the long-term accuracy and stability of the method. Spectra of 10 patients were recorded. An individual calibration models were calculated for each patient from spectra which were recorded at the beginning of the investigation. These models were then applied to calculate blood glucose values from spectra which were recorded 84 to 169 days later. The long-term accuracy and stability of the calibration models expressed as root mean squared error of prediction [RMSP] varied from 3.1 to 35.9 mmol/l and the error grid analysis [EGA] from 13 to 92% clinically acceptable values in zones A and B. The results of the investigation indicate that long-term monitoring of blood glocose by means of NIR-spectroscopy and individual calibration models over a period of 3 to 4 months is basically possible once long-term stability of the method will be improved. Further technological progress and a better understanding of the underlying physiological processes is necessary to achieve a level of accuracy, reliability and stability of the method as required for clinical application.

Non-invasive blood glucose monitoring by means of near infrared spectroscopy: investigation of long-term accuracy and stability.

Calibration in analytical chemistry refers to the relation between sample domain and measurement domain (signal domain) expressed by an analytical function x = fs(Q) representing a pattern of chemical species Q and their amounts or concentrations x in a given test sample on the one hand and a measured function y = f(z) that may be a spectrum, chromatogram, etc. Simultaneous multispecies analyses are carried out mainly by spectroscopic and chromatographic methods in a more or less selective way. For the determination of n species Qi (i = 1,2 …n), at least n signals must be measured which should be well separated in the ideal case. In analytical practice, the situation can be different.

Guidelines for calibration in analytical chemistry. Part 2: Multicomponent calibration (IUPAC Technical Report)

Information theory makes it possible to judge and evaluate methods and results in chemical analysis The obtained information can be expressed in different ways One way is to define information as the decrease of uncertainity after analysis Conditional probabilities are therefore considered when evaluating the information provided by qualitative analyses However, the use of other information measures, such as the information gain, is often preferable In multicomponent analysis the translation of information from signals to the amounts of the analytes has been investigated along with the relevance of individual components Information theory can also be applied to find the optimum experimental conditions The evaluation of the properties of analytical methods by information theory has been proposed

A review of information theory in analytical chemometrics

Selectivity and specificity are performance characteristics of analytical methods which are frequently used in analytical literature. In general, the terms are applied verbally and a quantification of selectivity and specificity is given rarely. Excepted are methods like chromatography and ISE sensoring which use individual quantities such as selectivity coefficients, indices and other parameters to characterize analytical procedures and systems. Here a proposal is given to characterize selectivity and specificity quantitatively by relative values in a range of 0 to 1 expressing so a certain degree of selectivity and specificity. By examples it will be shown that the derived quantities characterize analytical methods and problems in a plausible way.

Klaus Danzer

Papers

Use of solid-phase microextraction-capillary-gas chromatography (SPME-CGC) for the varietal characterization of wines by means of chemometrical methods

Non-invasive blood glucose monitoring by means of near infrared spectroscopy: investigation of long-term accuracy and stability.

Guidelines for calibration in analytical chemistry. Part 2: Multicomponent calibration (IUPAC Technical Report)

A review of information theory in analytical chemometrics

Selectivity and specificity in analytical chemistry. General considerations and attempt of a definition and quantification