Current state of diagnostic, screening and surveillance testing methods for COVID-19 from an analytical chemistry point of view.

Since December 2019, we have been in the battlefield with a new threat to the humanity known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we describe the four main methods used for diagnosis, screening and/or surveillance of SARS-CoV-2: Real-time reverse transcription polymerase chain reaction (RT-PCR); chest computed tomography (CT); and different complementary alternatives developed in order to obtain rapid results, antigen and antibody detection. All of them compare the highlighting advantages and disadvantages from an analytical point of view. The gold standard method in terms of sensitivity and specificity is the RT-PCR. The different modifications propose to make it more rapid and applicable at point of care (POC) are also presented and discussed. CT images are limited to central hospitals. However, being combined with RT-PCR is the most robust and accurate way to confirm COVID-19 infection. Antibody tests, although unable to provide reliable results on the status of the infection, are suitable for carrying out maximum screening of the population in order to know the immune capacity. More recently, antigen tests, less sensitive than RT-PCR, have been authorized to determine in a quicker way whether the patient is infected at the time of analysis and without the need of specific instruments.

Characterization of commercial Sacha inchi oil according to its composition: tocopherols, fatty acids, sterols, triterpene and aliphatic alcohols.

Sacha inchi oil (SIO) is one of the largest vegetable oil exports in Peru, used for consumption, in the food industry, cosmetics, and pharmaceuticals; it represents a significant economic income for producers. This study addresses the characterization and quantification of fatty acids, tocopherols, sterols, and alcohols of commercial Sacha inchi oils from Peru. Some of the SIO samples received had a high substance consistency, while others differed in the compounds studied. The results showed that some of the commercialized oils present high levels of γ-tocopherol and δ-tocopherol, while other samples had variable fatty acid compositions; especially in α-linolenic, linoleic, oleic and palmitic acids. Fourteen sterols and eleven alcohols were identified (ß-sitosterol, stigmasterol, campesterol, Δ5-avenasterol, triterpene alcohol, lanosterol isomer 1 and cycloartenol) being the major components. Some SIO samples presented the following ratios: The δ-tocopherol/γ-tocopherol ratio was 0.33-0.81, ω-6/ω-3 ratio was 0.77 and a stigmasterol/campesterol ratio of 3.13. The presence of brassicasterol in some commercial oils indicates the addition of rapeseed or canola oil. Tocopherols, fatty acids, sterols and alcohol data provided a classification of SIO samples, by an efficient k-means clustering algorithm analysis. The ANOVA found significant differences between clusters for palmitic acid, oleic acid, γ-tocopherol, δ-tocopherol, campesterol and stigmasterol; these compounds could be used as markers of authenticity in commercial Sacha inchi oils.

Antioxidant Capacity of Anthocyanins and Other Vegetal Pigments: Modern Assisted Extraction Methods and Analysis.

Anthocyanins [...].

Up-To-Date Analysis of the Extraction Methods for Anthocyanins: Principles of the Techniques, Optimization, Technical Progress, and Industrial Application.

Nowadays, food industries are concerned about satisfying legal requirements related to waste policy and environmental protection. In addition, they take steps to ensure food safety and quality products that have high nutritional properties. Anthocyanins are considered high added-value compounds due to their sensory qualities, colors, and nutritional properties; they are considered bioactive ingredients. They are found in high concentrations in many by-products across the food industry. Thus, the non-conventional extraction techniques presented here are useful in satisfying the current food industry requirements. However, selecting more convenient extraction techniques is not easy. Multiple factors are implicated in the decision. In this review, we compile the most recent applications (since 2015) used to extract anthocyanins from different natural matrices, via conventional and non-conventional extraction techniques. We analyze the main advantages and disadvantages of anthocyanin extraction techniques from different natural matrices and discuss the selection criteria for sustainability of the processes. We present an up-to-date analysis of the principles of the techniques and an optimization of the extraction conditions, technical progress, and industrial applications. Finally, we provide a critical comparison between these techniques and some recommendations, to select and optimize the techniques for industrial applications.

Assessment of phenolic and volatile compounds of commercial Sacha inchi oils and sensory evaluation.

Sacha inchi is a super seed primarily grown in the Amazon rainforest of Peru. One of the main products obtained from seeds is oil. This product is rich in polyunsaturated fatty acids, tocopherols, and sterols. The objective of this work was to authenticity evaluate of the Sacha inchi oil by means of characterization of phenols, volatile compounds, and sensory profile. The phenolic and volatile compounds were analyzed using liquid chromatography-electrospray ionization-time of flight/mass spectrometry (HPLC-ESI-TOF/MS) and headspace solid phase microextraction combined with gas chromatography and mass spectrometry (HS-SPME/GC-MS), respectively. A total of 16 phenolic compounds were detected in commercial Sacha inchi oils, while 54 compounds have been found in the volatile fraction. These compounds mainly correspond to notes generated by alcohols, aldehydes, acids, ketones, and terpenoids. Principal component analysis (PCA) showed that the first two PCs account for 71.13% of total variance. Statistical analysis was used to observe the relationships between phenolic and volatile compounds; therefore, consequently, it has been found that 16 volatile compounds may have a significant influence upon overall perceived flavor and odor of the commercial Sacha inchi oils. According to the odor and flavor, the Sacha inchi oil is characterized by "green" odor notes, seed, dried fruit and rough.

Antioxidant Capacity of Anthocyanins and other Vegetal Pigments.

Anthocyanins are the largest group of phenolic pigments, being effective hydrogen donors [...].

State of the Art of Anthocyanins: Antioxidant Activity, Sources, Bioavailability, and Therapeutic Effect in Human Health.

The antioxidant activity of anthocyanins in food is well known. Numerous antioxidant assays have been proposed to measure the capacity of anthocyanins to prevent the oxidation process that naturally occurs. Different solvents, temperatures, and pH levels are applied in each assay, and these factors should be taken into account in order to obtain useful and reproducible results. The concentration and the structure of these compounds are directly related to their antioxidant capacity and their environment. However, the effectiveness of the anthocyanin ingestion against diseases is also influenced by its bioavailability. Novel methodologies that simulate the digestion process have been developed in order to facilitate the current knowledge of anthocyanins bioavailability. Studies highlight the potential synergy effect between parent compounds and their derivatives (metabolites, conjugated products, and microbe-generated metabolites). The aim of this review is to provide an overview of advantages and disadvantages of the most common methods to determine the antioxidant activity of anthocyanins, chemical structure, and concentration of these compounds in different edible fruits, vegetables, and plants; their bioavailability after intake; as well as the main therapeutic effect described in the scientific literature.

Recovery of Anthocyanins Using Membrane Technologies: A Review.

Anthocyanins are naturally occurring polyphenolic compounds and give many flowers, fruits and vegetable their orange, red, purple and blue colors. Besides their color attributes, anthocyanins have received much attention in recent years due to the growing evidence of their antioxidant capacity and health benefits on humans. However, these compounds usually occur in low concentrations in mixtures of complex matrices, and therefore large-scale harvesting is needed to obtain sufficient amounts for their practical usage. Effective fractionation or separation technologies are therefore essential for the screening and production of these bioactive compounds. In this context, membrane technologies have become popular due to their operational simplicity, the capacity to achieve good simultaneous separation/pre-concentration and matrix reduction with lower temperature and lower operating cost in comparison to other sample preparation methods. Membrane fractionation is based on the molecular or particle sizes (pressure-driven processes), on their charge (electrically driven processes) or are dependent on both size and charge. Other non-pressure-driven membrane processes (osmotic pressure and vapor pressure-driven) have been developed in recent years and employed as alternatives for the separation or fractionation of bioactive compounds at ambient conditions without product deterioration. These technologies are applied either individually or in combination as an integrated membrane system to meet the different requirements for the separation of bioactive compounds. The first section of this review examines the basic principles of membrane processes, including the different types of membranes, their structure, morphology and geometry. The most frequently used techniques are also discussed. Last, the specific application of these technologies for the separation, purification and concentration of phenolic compounds, with special emphasis on anthocyanins, are also provided.

Spectrophotometric evaluation of stability constants of 1:1 weak complexes from continuous variation data.

A bilogarithmic hyperbolic cosine method for the spectrophotometric evaluation of stability constants of 1:1 weak complexes from continuous variation data has been devised and applied to literature data. A weighting scheme, however, is necessary in order to take into account the transformation for linearization. The method may be considered a useful alternative to methods in which one variable is involved on both sides of the basic equation (i.e. Heller and Schwarzenbach, Likussar and Adsul and Ramanathan). Classical least squares lead in those instances to biased and approximate stability constants and limiting absorbance values. The advantages of the proposed method are: the method gives a clear indication of the existence of only one complex in solution, it is flexible enough to allow for weighting of measurements and the computation procedure yield the best value of logbeta11 and its limit of error. The agreement between the values obtained by applying the weighted hyperbolic cosine method and the non-linear regression (NLR) method is good, being in both cases the mean quadratic error at a minimum.

A bilogarithmic method for the spectrophotometric evaluation of stability constants of 1:1 weak complexes from mole ratio data.

The absorbance changes that occur when the mole ratio of the components of ligand complex equilibria is varied while the concentration of one component is kept constant (mole ratio method) allow evaluating stability constants in favourable conditions. Values of the corresponding stability (association) constants are normally assigned on the basis of spectrophotometric analysis. Determination of stability constants can be performed by a number of linear procedures, but most of these, suffer from theoretical and practical drawbacks, e.g., linear transformation of the rectangular hyperbola type of binding constants, is valid only when one of the two species is present in a large excess. A rigorous treatment of the experimental mole ratio data for 1:1 weak complexes is carried out in this paper with the aim of eliminating some of the assumptions involved in the other methods usually applied for evaluating stability constants. Orthogonal regression is required in order to take into account the error in both axes. The method has been applied to literature data for the iron(III)-thiocyanate and nickel(II)-selenocyanate systems, as well as to a number of host-guest cyclodextrin complexes.

Continuous variation data: 1:1 or 2:2 weak complexes?

An attempt to distinguish between 1:1 and 2: 2 weak complexes from continuous variation data is given. A modification of the Heller and Schwarzenbach's method which involves the use of the absorbance ratio y=A/A(lim) (once the limiting absorbance, A(lim) is known) may be applied to 1:1 weak complexes. This allows checking if the slope obtained is close to the theoretical value of -0.25. A curvature appears and the residuals have a pattern when a wrong 1:1 model is selected for a true 2:2 stoichiometry.

"Why not stoichiometry" versus "stoichiometry--why not?" Part I: General context.

The elementary concepts involved with stoichiometry are considered from different viewpoints. Some examples of approximate calculations made according to the stoichiometric scheme are indicated, and correct resolution of the problems involved is presented. The principles of balancing chemical equations, based on their apparent similarities with algebraic equations, are criticized. The review concerns some peculiarities inherent in chemical reaction notation and its use (and abuse) in stoichiometric calculations that provide inconsistent results for various reasons. This "conventional" approach to stoichiometry is put in context with the generalized approach to electrolytic systems (GATES) established by Michalowski. The article contains a number of proposals that could potentially be taken into account and included in the next edition of the Orange Book. Notation of ions used in this article is not, deliberately, in accordance with actual IUPAC requirements in this respect. This article is intended to be provocative with the hope that some critical debate around the important topics treated should be generated and creatively expanded in the scientific community.

"Why not stoichiometry" versus "Stoichiometry--why not?" Part II: GATES in context with redox systems.

Redox equilibria and titration play an important role in chemical analysis, and the formulation of an accurate mathematical description is a challenge. This article is devoted to static and (mainly) dynamic redox systems; the dynamic systems are represented by redox titrations. An overview addresses earlier approaches to static redox systems (redox diagram plots, including Pourbaix diagrams) and to titration redox systems, thereby covering a gap in the literature. After this short review, the generalized approach to electrolytic systems (GATES) is introduced, with generalized electron balance (GEB) as its inherent part within GATES/GEB. Computer simulation, performed according to GATES/GEB, enables following the changes in potential and pH of the solution, together with chemical speciation at each step of a titration, thus providing better insight into this procedure. The undeniable advantages of GATES/GEB over earlier approaches are indicated. Formulation of GEB according to two approaches (I and II) is presented on the respective examples. A general criterion distinguishing between non-redox and redox systems is presented. It is indicated that the formulation of GEB according to Approach II does not need the knowledge of oxidation degrees of particular elements; knowledge of the composition, expressed by chemical formula of the species and its charge, is sufficient for this purpose. Approach I to GEB, known also as the "short" version of GEB, is applicable if oxidation degrees for all elements of the system are known beforehand. The roles of oxidants and reductants are not ascribed to particular components forming a system and to the species thus formed. This is the complete opposite of earlier approaches to redox titrations, based on the stoichiometric redox reaction, formulated for this purpose. GEB, perceived as a law of matter conservation, is fully compatible with other (charge and concentration) balances related to the system in question. The applicability of GATES/GEB in optimization a priori of chemical analyses made with use of redox titration is indicated. The article is illustrated with many examples of static and dynamic redox systems. The related plots are obtained from calculations made according to iterative computer programs. This way, GATES/GEB enables seeing details invisible in real experiments.

"Why Not Stoichiometry" versus "Stoichiometry­Why Not?" Part III: Extension of GATES/GEB on Complex Dynamic Redox Systems.

In the third part of a series of articles issued under a common title, some examples of complex dynamic redox systems are presented and considered from analytical and physico-chemical viewpoints; the analysis is a leitmotiv for detailed, physico-chemical considerations. All attainable physico-chemical knowledge is involved in algorithms applied for resolution of the systems, realized with use of iterative computer programs. The first redox system (System I) is related to titration of FeSO4 + H2C2O4 with KMnO4 solution in acidic (H2SO4) medium, where simultaneous determination of both analytes from a single curve of potentiometric titration is possible. The possibility of the formation of precipitates (FeC2O4 and/or MnC2O4) in this system is taken into considerations. The second system (System II) relates to the complete analytical procedure involved in the iodometric determination of Cu; four consecutive steps of this analysis are considered. As a reasonable tool for explanation of processes occurring during simulated redox titration, speciation diagrams are suggested. This explanation is based on graphical presentation of results obtained from the calculations. The calculations made for this purpose are performed in accordance with principles of the generalized approach to electrolytic systems (GATES) with generalized electron balance (GEB) or GATES/GEB and realized with use of iterative computer programs offered by MATLAB. The reactions proceeding in this system can be formulated, together with their efficiencies, at any stage of the titration. Stoichiometry is considered as the derivative concept when put in context with GATES/GEB. The article illustrates the enormous possibilities and advantages offered by GATES/GEB.

Characterization of anthocyanins from the fruits of baguaçu (Eugenia umbelliflora Berg).

Anthocyanin pigments in the berries of baguaçu (Eugenia umbelliflora Berg), a tropical fruit from Brazil, were extracted with 0.1% HCl in ethanol, and the crude anthocyanin extract was purified by Amberlite XAD-7 open-column chromatography. Six major anthocyanins were isolated by preparative HPLC, and their chemical structures were identified by spectroscopic methods (TLC, UV-vis, MS, and (1)H NMR). Delphinidin 3-O-beta-glucopyranoside, cyanidin 3-O-beta-glucopyranoside, petunidin 3-O-beta-glucopyranoside, pelargonidin 3-O-beta-glucopyranoside, peonidin 3-O-beta-glucopyranoside, and malvidin 3-O-beta-glucopyranoside were identified. On the basis of chromatographic data the total anthocyanin content was 342 mg/100 g of fresh baguaçu berries. Therefore, the concomitant presence of six anthocyanins in a single plant species makes this product promising as a new pigment source.

HPLC-DAD determination of CNS-acting drugs in human blood, plasma, and serum.

This is a review of the literature regarding high-performance liquid chromatography-diode array detection (HPLC-DAD) procedures for the detection and determination of several categories of central nervous system-acting drugs in blood, plasma, or serum samples. Psychiatric and neurological drugs, such as antidepressants, benzodiazepines, antipsychotics, antiepileptics, and antiparkinsonians, have been included because of their relevance to therapeutic drug monitoring and systematic toxicological analysis. Articles published between 2000 and January 2012 have been taken into consideration. This review has focused on methodological approaches, sample pretreatment techniques, and other practical aspects.

A uniform nonlinearity criterion for rational functions applied to calibration curve and standard addition methods.

Rational functions of the Padé type are used for the calibration curve (CCM), and standard addition (SAM) methods purposes. In this paper, the related functions were applied to results obtained from the analyses of (a) nickel with use of FAAS method, (b) potassium according to FAES method, and (c) salicylic acid according to HPLC-MS/MS method. A uniform, integral criterion of nonlinearity of the curves, obtained according to CCM and SAM, is suggested. This uniformity is based on normalization of the approximating functions within the frames of a unit area.

On the isohydricity concept--some comments.

The isohydricity property, referred to systems composed of acids or bases, is presented. The related isohydricity conditions are formulated for different pairs of solutions. The pH titrations in the system of isohydric solutions are put in context with conductometric titrations. The differences between pK1 values obtained according to both methods are not too significant and the conductometric titration can be perceived, in some instances, as a reasonable alternative to the pH titration.

Application of rational functions for the standard addition method.

Some rational functions are considered as the basis for calculation of unknown concentration (x0) of an analyte X determined according to the standard addition method (SAM). The correction for dilution of the sample tested during addition of successive increments of standard(ised) solution of X is involved in the related algorithm applied for calculation of the x0 value. The formulae derived were put in context with experimental data, obtained according to the AAS method from Cu-measurements in samples obtained by digestion of an ash obtained from incinerated sludge. It was stated that the use of rational functions for modeling purposes strengthens the robustness of the results thus obtained.

Determination of dissociation parameters of weak acids in different media according to the isohydric method.

The isohydricity (pH constancy) principle is referred to the pair of solutions: weak acid (HL, C(0)mol/L) and strong acid (HB, C mol/L) when mixed e.g., according to titrimetric mode. Such a case takes place if the relation C(0)=C+C(2) × 10(pK(1)) is valid, where pK(1)=-log K(1), K(1) - dissociation constant for a weak monoprotic acid HL. This principle, outlined and formulated in earlier paper (Michalowski et al., Talanta 82 (2010) 1965), is the basis for a sensitive method of pK(1) determination, confirmed for a series of weak acids in presence of basal electrolytes or in water+organic solvent (dimethyl sulphoxide, methanol, isopropanol) media. The results of titrations were elaborated according to principles of regression analysis, with use of least squares method. A new criterion for precision of the results obtained according to this method is formulated. The pK(1) values obtained are comparable with ones found in literature.