Purificación Sáez-Plaza’s research while affiliated with University of Seville and other places
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Halogens have been a particular battlefield of pharmaceutical researchers. Chlorine, bromine and iodine, are closely related to the volumetric methods, in its beginnings. The blue colour of the iodine-starch complex observed by Colin and Gaultier de Claubry, and Stromeyer (1814), serves as an indicator for the detection of trace quantities of iodine. Houtou de Labillardière (1825) introduces the use of iodine in volumetry, proposing an alternative procedure for the estimation of the chlorine content in commercial calcium hypochlorite. Dupasquier (1840) warns the possibility of accurately and quickly assessing hydrogen sulfide (hepatic gas) free or combined, with the help of a titrated solution of iodine in the presence of starch as an indicator. Fordos and Gelis show in 1843 that two iodine atoms quantitatively oxidize two molecules of sodium hyposulfite (thiosulfate), a reaction that constitutes the fundamental basis of iodometry. This paper reviews the iodometric methods of analysis from its inception to Bunsen, covering aspects of the life and work of the researchers involved, as well as their mutual connections, including transnational ones.
This paper reviews the first published textbooks on volumetric analysis providing data on the life and work of their authors: Schwarz, Mohr, Poggiale and Beckurts.
In 1883 Kjeldahl devised a method for the determination of nitrogen, which has become a classical measurement in analytical chemistry and has been used extensively over the past 130 years. In the original method, sulfuric acid alone was used as a digestion medium. The use of a catalyst in Kjeldahl digestion accelerates oxidation and completes the digestion to allow the subsequent determination of nitrogen. Mercury (its use being in decline because of environmental concerns), selenium, and copper are the catalysts of choice, though for certain applications titanium has found some usage. Short digestion times in association with maximum nitrogen recovery may be achieved by using a methodology based on experimental design and response surfaces, with microwave digestion processes, and with the aid of the couple sulfuric acid-hydrogen peroxide without catalyst. The quantification of distilled ammonia is generally achieved by titration; the ammonia is absorbed in an excess of boric acid, followed by titration with standard acid in the presence of a suitable indicator. The Kjeldahl method can be done with limited resources; nitrogen determination with the Kjeldahl method does not require expensive devices nor specialized techniques and is precise and accurate. The Kjeldahl method is used for calibrating other protein assays; it is still the primary reference method for protein analysis today. The original method as presented by Kjeldahl has been continuously improved. Today's digestion systems offer safety both from a personal perspective and from an environmental point of view. The determination of nitrogen content is a frequently conducted analysis in industry and commerce, and numerous organizations have official methods. The use of instrumental finish in Kjeldhal applications will be the subject of the second part of this review.
The Kjeldahl method was introduced in 1883 and consists of three main steps: sample digestion, distillation, and ammonia determination (titration being the primary method). The Kjeldahl method uses sulfuric acid, a variety of catalysts, and salts to convert organically bound nitrogen in samples to ammonium with its subsequent measurement (Sáez-Plaza et al., 2013). Today, this method is universally accepted and used in tens of thousands of laboratories throughout the world for nitrogen analysis in a wide variety of materials, such as foods, beverages, agricultural products, environmental samples, chemicals, biochemicals, and pharmaceuticals. However, successful analysis requires proper sampling and sample handling, which depend on the type of material. The Kjeldahl method has been validated and standardized for total (crude) protein estimation for a wide variety of food matrices, indirectly determined by their nitrogen content, and is the reference method adopted by many international organizations. The Kjeldahl procedure has several variants, based mainly on a sample size and apparatus required. A number of rapid and accurate instrumental methods have been gradually introduced that have some advantages compared to older techniques, if a large number of samples are to be run. Thus, extracted nitrogen from Kjeldahl can be determined by several other methods, i.e., spectrophotometric, potentiometric with ion selective electrode, FIA, ion chromatographic, and chemiluminescent methods. Quality control is essential for accurate and precise measurements of nitrogen by the Kjeldahl method. The importance of quality control in Kjeldahl analysis is stressed in this review. Despite some negative factors (i.e., it is hazardous, lengthy, and labor intensive), the Kjeldahl method and its variants with instrumental finish remain as accurate and reliable methods.
Anthocyanins are one of the many compound classes that belong to the polyphenolic flavonoid group. This group species of secondary metabolites are synthesized in almost all higher order plants, conferring the bright red, blue, and purple colors to berries and fruits. They have recently been the focus of significant beneficial health claims due to their antioxidant capacity. The interest of both consumers and academics in understanding the medicinal, therapeutical, and nutritional value provided by these naturally occurring phytochemical compounds is increasing. The development of analytical techniques to determine the identity and quantities of anthocyanins in natural products, as well as their effects in vivo and in vitro, is challenging. There is a need for extensive collection of information on the composition of natural colors and their recovery methods as a consequence of the increased demand for natural colors by industries. Numerous procedures have been used over the years for the sample treatment of phytochemicals. In this review special attention is paid to topics concerning with sampling and sample preparation methods, with the focus on anthocyanins; useful information is collected in tabular form.
Anthocyanins are naturally occurring polyphenol compounds that impart orange, red, purple, and blue color to many fruits, vegetables, grains, flowers, and plants. In recent decades, interest in anthocyanin pigments has increased due to their possible utilization as natural food colorants and especially because their consumption has been linked to protection against many chronic diseases. It seems that anthocyanin posseses strong antioxidant properties leading to a variety of health benefits. Coupled to increasing consumer demand, food manufacturers have moved towards increased usage of approved natural colors. Despite the great potential in applications that anthocyanins represent for food, pharmaceutical, and cosmetic industries, their use has been limited because of their relative instability and low extraction percentage. Growing demands have been made on sample pretreatment, and over time some novel extraction techniques have been developed. Solid phase extraction, countercurrent chromatography, adsorption, pressurized liquid or fluid extraction, and microwave-assisted extraction are environmentally friendlier in terms of using smaller amount of solvents (often nontoxic) and reducing working time. The past few years have been characterized by wide interest in these techniques, and many contributions describing these methods have been published. The aim of this article is to review the literature available on the most important procedures proposed for the extraction of anthocyanins; the use of non-thermal technologies in the assisted extraction of anthocyanins will be covered in a separate report.
Anthocyanins belong to a large group of secondary plant metabolites collectively known as flavonoids, a subclass of the polyphenol family. They are a group of very efficient bioactive compounds that are widely distributed in plant food. Anthocyanins occur in all plant tissues, including leaves, stems, roots, flowers, and fruits. Research on phenolic compounds through the last century, from the chemical, biochemical, and biological points of view, has focused mainly on the anthocyanins. Anthocyanins have structures consisting of two aromatic rings linked by three carbons in an oxygenated heterocycle (i.e., a chromane ring bearing a second aromatic ring in position 2). The basic chromophore of anthocyanins is the 7-hydroxyflavilyum ion. Anthocyanin pigments consist of two or three chemical units: an aglycon base or flavylium ring (anthocyanidin), sugars, and possibly acylating groups. Only six of the different anthocyanidins found in nature occur frequently and are of dietary importance: cyanidin, delphinidin, petunidin, peonidin, pelargonidin, and malvidin. Each aglycon may be glycosilated or acylated by different sugars and aromatic or aliphatic acids, yielding over 600 different anthocyanins reported from plants. The sugar moiety is typically attached at the 3-position on the C-ring or the 5-position on the A-ring. The chromophore of eight conjugate double bonds carrying a positive charge on the heterocyclic oxygen ring is responsible for the intensive red-orange to blue-violet color produced by anthocyanins under acidic conditions. Anthocyanins occur in solution as a mixture of different secondary structures: flavylium ion, a quinoidal base, a carbinol base, and a chalcone pseudobase. Self-association, intermolecular, and intramolecular co-pigmentation of anthocyanins leads to the formation of tertiary structures through varying stabilization mechanisms. Anthocyanin composition has been used as a botanical tool for taxonomic classification of plants. In addition, anthocyanin profiles of fruits and vegetables allow detecting adulteration of anthocyanin-based products and are indicators of product quality. Anthocyanins are common components of the human diet, as they are present in many foods, fruits, and vegetables, especially in berries. Moreover, anthocyanins have an antioxidant activity, depending to a large extent upon their chemical structure. Many epidemiological studies have shown the benefits of a diet rich in fruit and vegetables to human health, and for the prevention of various diseases associated with oxidative stress, such as cancer and cardiovascular diseases. Anthocyanin-rich extracts are increasingly attractive to the food industry as natural alternatives to synthetic FD&C dyes and lakes, because of their coloring properties. Anthocyanins are also one of the nine European Union-designated natural color classes. Various adverse effects on health have frequently been attributed to synthetic antioxidants. For these reasons, currently, there is a trend towards relying on antioxidants derived from natural products. Anthocyanins act as antioxidants both in the foodstuffs in which they are found and in the organism after intake of these foods. This review, like the first one of the series, intends to reflect the interdisciplinary nature of the research that is currently carried out in this prolific area.
Many epidemiological studies have shown the benefits of a diet rich in fruit and vegetables to human health and for the prevention of various diseases associated with oxidative stress, such as cancer and cardiovascular diseases. Anthocyanins, natural pigments belonging to the group of flavonoids, are common components of the human diet, as they are present in many foods, fruits, and vegetables, especially in berries. Their use as colorants has considerable interest because of their coloring properties. Moreover, they have an antioxidant activity. Various adverse effects on health have frequently been attributed to synthetic antioxidants. For these reasons, currently, there is a trend towards relying on antioxidants derived from natural products. The efficacy of anthocyanins as antioxidants depends, to a large extent, upon their chemical structure. They act as antioxidants both in the foodstuffs in which they are found and in the organism after intake of these foods. With this in mind, an introduction to polyphenols is made with emphasis on their role as secondary metabolites, classification, and health relevance. Flavonoid intake, biological activities, databases, classification and structure, distribution, and dietary sources are then considered. Aspects of anthocyanin concerning its early history and chemical structure, color, and intake are dealt with in the second part of the series. The extraction and analysis of anthocyanin pigments and their antioxidant power, paying special attention to the oxidation process, will be the subject of the third part. Bioavailability and metabolism of anthocyanic pigments, the methods used for measuring the antioxidant activity of anthocyanins, and the influence of anthocyanins on the antioxidant activity of wine will finally be covered in the fourth part. The present review intends to reflect the interdisciplinary nature of the research that is currently carried out in this prolific area. Key research articles and reviews are mainly referenced, and we apologize to those researchers whose work is not cited directly by us.
... Iodometry, the titrimetric determination of iodine, is steeped in chemical history 8,9 and is the basis of many important analytical methods. 10 It was first described by Bunsen in 1853, 8 following the introduction of quantitative titrimetric methods by Gay-Lussac around 1824 11 (coincidently, Gay-Lussac named the element iodine, from which iodometry gets its name). ...
... Ash content was determined using a muffle ramp up to 575 • C (Type F62700 Furnace, Barnstead International) [39]. Protein content with the Kjeldahl method [40] using a Nitrogen to protein conversion factor of 6.25 [41]. For extractives, Soxhlet extractions were performed sequentially with water, ethanol, and hexane [42] and measured gravimetrically after solvent removal with the help of a rotary evaporator (RV 10 digital V Rotary evaporator, IKA). ...
... Soil organic matter was quantified by K 2 Cr 2 O 7 -H 2 SO 4 wet oxidation method (Soil Survey Staff, 2014). The semi-micro Kjeldahl method was adopted for determining Soil total N (TN) (Sáez-Plaza et al., 2013). Soil cation exchange capacity (CEC) and exchangeable base cations were identified following the buffered ammonium acetate method (1 M, pH=7.0) ...
... In static mode, following extraction, the system is rinsed with solvent to transfer the extract, whereas dynamic mode entails continuous solvent pumping. Both operational modes adhere to Fick's law of difusion [33,[36][37][38][39][40][41]. PLE fnds specifc applications in the extraction of ACNs from various natural sources. ...
... They are distinctive from the other flavonoids by their ability to form flavylium cations ( Fig. 1) (Mazza, 2007). ANCs consist of an aglycon base or flavylium ring (anthocyanidin), sugars, and may contain acylating groups (Bueno et al., 2012). From the several anthocyanidins found in nature, only cyanidin, delphinidin, petunidin, peonidin, pelargonidin, and malvidin ( Fig. 1) are of importance in human nutrition (Harborne, 1998;Jaganath & Crozier, 2010;Bueno et al., 2012). ...
... Flavan-3-ols, including the monomer catechin and its polymer condensed tannins, are effective anti-fungal and anti-herbivore compounds (Bueno et al., 2012, Hammerbacher et al., 2020. Even low catechin concentrations (0.1% dw) reduce the tunnelling of Ips typographus males by 50% (Faccoli and Schlyter, 2007). ...
... Thus, further sample clean-up/cleansing with sorption columns is required to get a highly pure product which should be as compatible as with the chosen analytical instrument; (iv) analysis-the product with enriched compounds-of-interest is further subjected to the sensitive analysis using a front-end analytical instrumentation commonly mantled as a tandem of chromatograph and detection unit (on-line scheme); (v) assessment-results from analysis obtained in the form of analytical intensities are ultimately assigned to the particular analytes. [19,20] The successive sections will describe preconcentrationbased sample preparation methods of chiral compounds where analytes were extracted to a liquid extraction phase. Considering $120 papers reporting microextraction methods for the quantification of chiral compounds in biological and environmental samples, only 39 papers deal with LPME techniques (Figure 2). ...