Determination of Iron Species in Samples of Iron-Fortified Food

A Fast and Efficient Procedure of Iron Species Determination Based on HPLC with a Short Column and Detection in High Resolution ICP OES

The optimization and application of a new hyphenated procedure for iron ionic speciation, i.e., high performance liquid chromatography (HPLC) with short cation-exchange column (50 mm × 4 mm) coupled to high resolution inductively coupled plasma optical emission spectrometry (ICP hrOES), is presented in this paper. Fe(III) and Fe(II) species were separated on the column with the mobile phase containing pyridine-2,6-dicarboxylic acid (PDCA). The total time of the analysis was approx. 5 min, with a significantly low eluent flow rate (0.5 mL min^-1) compared to the literature. Additionally, a long cation-exchange column (250 mm × 4.0 mm) was used as reference. Depending on the total iron content in the sample, two plasma views were chosen, e.g., an attenuated axial (<2 g kg^-1) and an attenuated radial. The standard addition method was performed for the method's accuracy studies, and the applicability was presented on three types of samples: sediments, soils, and archaeological pottery. This study introduces a fast, efficient, and green method for leachable iron speciation in both geological and pottery samples.

Digestibility of Protein and Iron Availability from Enriched Legume Sprouts

Plant ferritin is suggested as a good source of iron for human. Usually present in trace amounts, it was induced in legumes seeds by their sprouting in FeSO₄ solution. Fortified sprouts were digested in the in vitro model of the human gastrointestinal tract. ~49% of lupine and ~ 45% of soy proteins were extracted into gastric fluid and next ~ 12% and only ~ 1% into intestine fluid from lupine and soybean, respectively. Gastric digestion released mainly ferrous iron (~ 85% from lupine and ~ 95% in soybean sprouts). Complexed iron constituted ~ 43% of total iron in intestine after lupine digestion and ~ 55% after soybean digestion. Intestine digestion doubled the total iron released from lupine sprouts (from ~ 21% up to 38%), while in soybean it increased from ~ 16% up to ~ 23%. Ferritin presence was confirmed by the specific antibodies in digestive fluids, but it is only partially extracted from sprouts during in vitro digestion.

Are Citric Acid-Iron II Complexes True Chelates or Just Physical Mixtures and How to Prove This?

Although mineral chelates are widely produced to be used as food fortifiers, the proof that these complexes are chelates is still missing. In our present work, iron II complexes using citric acid in different ratios are produced, and the occurrence of chelation is investigated along with its behavior according to a molar ratio between the ligand and the mineral. High performance liquid chromatography (HPLC), flame atomic absorption spectroscopy (FAAS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared (FTIR), and near infrared spectroscopy (NIR) were used for a non-structural characterization of these complexes. In contrast to published work, our findings show that the chelation of citric acid is achieved in the liquid form and at a low pH and that the molar ratio is very important in setting the direction of the reaction, either toward chelation or dimer formation. The ratio citric acid:iron 1:4 seems to be the most convenient ratio in which no free citric acid remains in the solution, while the 1:3 ratio behaves differently, requiring further investigations by such techniques as extended X-ray absorption fine structure spectroscopy (EXAFS), among others, in order to deeply identify the structural organization occurring in this ratio. NIR, extensively used in industries, proved to be very useful in the demonstration and characterization of chelates. These findings are particularly advantageous for pharmaceutical and food industries in offering an innovative competent fortifying agent to be used in combatting iron deficiency.

Calcium and Iron Content of Cereal-Based Gluten-Free Products

The impact of a gluten-free (GF) diet on the intake of calcium and iron is broadly unknown, as the micronutrient content of GF cereal-based products has scarcely been measured. The study aimed to measure the calcium and iron content of GF cereal-based products from the UK. Seventy-three GF products were analysed. A laboratory analysis of calcium and iron from GF food samples was performed by spectrophotometric and flame emission photometry, respectively. The values for wheat-based products were from a nutrient database. The calcium in GF white loaf samples varied greatly from 54 to 140 mg/100 g, with a lower average calcium content compared with wheat-based values (99 ± 29 mg/100 g n = 13 versus 177 mg/100 g; p < 0.01). Only 27% of the white loaves and rolls were fortified with calcium; this contrasts with 100% of white wheat-based loaves. The calcium in GF flour mixes ranged from 54 to 414 mg/100 g, with 66% fortified. GF white pasta had more calcium compared with wheat-based pasta (76 ± 27 mg/100 g n = 7 versus 24 mg/100 g; p = 0.002). The iron in GF bread loaves and pasta samples was similar to wheat-based comparators, whereas lower iron levels were observed in GF wraps (0.8 ± 0.2 n = 11 versus 1.6 mg/100 g). GF bread had a significantly higher fibre content, and the majority of GF bread had a lower protein content, compared with wheat-based bread products. These calcium and iron values provide a valuable addition towards enabling more accurate nutrient intake analysis for adults and children with coeliac disease.

Microwave-Assisted Rapid Synthesis of Luminescent Tryptophan-Stabilized Silver Nanoclusters for Ultra-Sensitive Detection of Fe(III), and Their Application in a Test Strip

A new preparation method for extreme fluorescent green emission tryptophan-stabilized silver nanoclusters (Tryp-AgNCs) is presented in this scientific research. The produced silver nanoclusters are dependent on tryptophan amino acid which contributes to normal growth in infants and the sublimation and recovery of human protein, muscles, and enzymes. Herein, we have introduced a green method by using microwave-assisted rapid synthesis. The subsequent silver nanoclusters (AgNCs) have excitation/emission peaks at 408/498 nm and display a considerable selectivity to Fe(III) ions. The tryptophan amino acid molecule was used in the synthesis process as a reducing and stabilizing agent. The Tryp-AgNCs’ properties were investigated in terms of morphology, dispersity, and modification of the synthesized particles using different advanced instruments. The luminescent nanoclusters traced the Fe(III) ions by the luminescence-quenching mechanism of the Tryp-AgNCs luminescence. Therefore, the extreme selectivity of the prepared nanoclusters was exhibited to the Fe(III) ions, permitting the sensitive tracing of ferric ions in the lab and in the real environmental samples. The limit of detection for Fe(III) ions based on Tryp-AgNCs was calculated to be 16.99 nM. The Tryp-AgNCs can be efficiently applied to a paper test strip method. The synthesized nanoclusters were used efficiently to detect the Fe(III) ions in the environmental samples. Moreover, we examined the reactivity of Tryp-AgNCs on various human tumor cell lines. The results show that the Tryp-AgNCs exhibited their activity versus the cancer cells in a dose-dependent routine for the perceived performance versus the greatest-used cancer cell lines.

Interactions of Ascorbic Acid, 5-Caffeoylquinic Acid, and Quercetin-3-Rutinoside in the Presence and Absence of Iron during Thermal Processing and the Influence on Antioxidant Activity

Bioactive compounds in fruit and vegetables influence each other’s antioxidant activity. Pure standards, and mixtures of the common plant compounds, namely ascorbic acid, 5-caffeoylquinic acid, and quercetin-3-rutinoside (sum 0.3 mM), in the presence and absence of iron, were analyzed pre- and post-thermal processing in an aqueous solution. Antioxidant activity was measured by total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (TEAC) radical-scavenging assays. Ionic ferrous iron (Fe²⁺) and ferric iron (Fe³⁺) were measured photometrically. For qualification and quantification of reaction products, HPLC was used. Results showed that thermal processing does not necessarily lead to a decreased antioxidant activity, even if the compound concentrations decreased, as then degradation products themselves have an antioxidant activity. In all used antioxidant assays the 2:1 ratio of ascorbic acid and 5-caffeoylquinic acid in the presence of iron had strong synergistic effects, while the 1:2 ratio had strong antagonistic effects. The pro-oxidant iron positively influenced the antioxidant activity in combination with the used antioxidants, while ferrous iron itself interacted with common in vitro assays for total antioxidant activity. These results indicate that the antioxidant activity of compounds is influenced by factors such as interaction with other molecules, temperature, and the minerals present.

Iron Forms Fe(II) and Fe(III) Determination in Pre-Roman Iron Age Archaeological Pottery as a New Tool in Archaeometry

This article presents studies on iron speciation in the pottery obtained from archaeological sites. The determination of iron forms Fe(II) and Fe(III) has been provided by a very simple test that is available for routine analysis involving the technique of molecular absorption spectrophotometry (UV–Vis) in the acid leachable fraction of pottery. The elemental composition of the acid leachable fraction has been determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, the total concentration of the selected elements has been determined by X-ray fluorescence spectrometry with energy dispersion (EDXRF). The results of the iron forms’ determinations in archaeological pottery samples have been applied in the archaeometric studies on the potential recognition of the pottery production technology, definitely going beyond the traditional analysis of the pottery colour.

Estimation of Iron Content and Its Contribution in Iron-Fortified Food Products Consumed by School Children in Sri Lanka

Iron fortification is an effective strategy that can be implemented to ensure supply and intake of iron for the public at large. Even though iron-fortified foods are widely available in the Sri Lankan market, the quantification of iron in those foods is not under the regulations of the food authorities in Sri Lanka. Therefore, this study aims to quantify the concentration of iron in selected iron-fortified foods available in the local market and determine their contribution to the recommended daily allowances (RDA) per serving. The iron content in most popular powdered milk, biscuits, and breakfast cereals among the children of 15-16 years in Horana Divisional Secretariat was analyzed using atomic absorption spectroscopy, and its contribution to RDA was calculated. The average iron values of iron-fortified milk powder (IFMP), iron-fortified biscuit (IFB), and iron-fortified breakfast cereals (IFBC) were found to be 18.08 ± 9.53, 7.88 ± 0.07, and 17.78 ± 7.47 mg/100 g, respectively. The average estimated daily intake (EDI) per serving of IFMP, IFB, and IFBC was 3.61 ± 1.75, 2.13 ± 0.06, and 5.60 ± 1.45 mg, respectively. The highest contribution to the RDA can be obtained by a single serving of IFBC. Only less than half of the tested products have compatible iron levels with their labeled information. Iron-fortified foods which were studied have a high amount of iron, and they can make from 5% to 35% contribution to RDAs in young children, adolescents, and adults even by a single serving.

Mutual Separation of Fe(II) and Fe(III) Using Cyclohexane/Water/Ionic-liquid Triphasic Extraction System with 2,2'-Bipyridine and Tri-n-octylphosphine Oxide

The triphasic extraction system with two extract phases can be used to separate two materials simultaneously into each phase. In this article, a possible mutual separation of Fe(II) and Fe(III) was studied using the cyclohexane/water/ionic liquid (IL) triphasic extraction system for Fe speciation. For Fe(II) and Fe(III) extraction, 2,2'-bipyridine (bpy) and tri-n-octylphosphine oxide (TOPO) were selected as extractants, respectively. It was suggested that [FeII(bpy)3]2+ and FeIII(TOPO)43+·3Tf2N- were extracted into the IL (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, C4mimTf2N) phase and the cyclohexane phase, respectively, and both of the extractants also acted as masking agents. On simultaneous separation using the triphasic system, Fe(II) and Fe(III) were quantitatively extracted into the IL phase and the cyclohexane phase, respectively, and their mutual separation was achieved.

Sensitive SQUID Bio-Magnetometry for Determination and Differentiation of Biogenic Iron and Iron Oxide Nanoparticles in the Biological Samples

This study aimed to develop the method for determination of the ultra-small superparamagnetic iron oxide nanoparticle (USPION)-originated iron (UOI) in the tissues of rats on the basis of the magnetic characteristics (MC) in the liver, left heart ventricle (LHV), kidneys, aorta and blood of Wistar-Kyoto (WKY). Rats were treated intravenously by USPIONs dispersed in saline (transmission electron microscope (TEM) mean size ~30 nm, hydrodynamic size ~51 nm, nominal iron content 1 mg Fe/mL) at the low iron dose of 1 mg/kg. MC in the form of the mass magnetisation (M) versus the magnetic field (H) curves and temperature dependences of M (determined using the SQUID magnetometer), histochemical determination of iron (by Perl's method) and USPION-induced superoxide production (by lucigenin-enhanced chemiluminescence) were investigated 100 min post-infusion. USPIONs significantly elevated superoxide production in the liver, LHV, kidney and aorta vs. the control group. Histochemical staining confirmed the presence of iron in all solid biological samples, however, this method was not suitable to unequivocally confirm the presence of UOI. We improved the SQUID magnetometric method and sample preparation to allow the determination of UOI by measurements of the MC of the tissues at 300 K in solid and liquid samples. The presence of the UOI was confirmed in all the tissues investigated in USPIONs-treated rats. The greatest levels were found in blood and lower amounts in the aorta, liver, LHV and kidneys. In conclusion, we have improved SQUID-magnetometric method to make it suitable for detection of low amounts of UOI in blood and tissues of rats.

Iron Content of Some Popular Cooked Foods Consumed by the Rural School Children in Sri Lanka

Iron is an important micronutrient that can be found in different food sources in varying quantities. Iron deficiency is common in populations consuming cereal-based diets with little or no animal-derived food products. Rice is the staple for Sri Lankans, which may not provide sufficient bioavailable iron. Sri Lankan food composition table does not contain data on iron in home-cooked foods. Aim of the present study was to determine the iron content in commonly consumed home-cooked foods (rice, vegetables, green leaves, pulses, fish, etc.) by children aged 15-16 years. The study was carried out in eight schools at the Divisional Secretariat, Horana. The average iron values of cooked rice, vegetables, green leaves, pulses, and fish were 23.29 ± 14.46, 19.34 ± 9.90, 29.56 ± 13.64, 45.16 ± 22.28, and 46.72 ± 14.53 mg/kg, respectively. A serving of cooked red raw rice (rathu kekulu) provided the highest Estimated Daily Intake (EDI) of iron. The total EDI per serving for all categories was 6.39 ± 1.06 mg, contributing to the recommended daily allowance (RDA) of 42.62% of girls and 58.12% of boys as defined by the United States Department of Agriculture. Meanwhile, based on the Sri Lankan RDA, dietary iron contribution per serving ranges from 16.39% to 17.76% in girls and 16.39% to 21.31% in boys in the 15-16 years age category. Therefore, these home-cooked foods which were prepared using local recipes have high iron content and can replenish a major proportion of recommended quotidian values for iron intake.

Iron's fingerprint of deposits-iron speciation as a geochemical marker

The article describes the studies of the iron speciation (the occurrence of Fe(II), Fe(III), and complexed iron) in acid leachable fraction of deposits. The speciation of iron was diverse for deposits of different origins and was the specific "fingerprint"-marker of deposition processes. The higher occurrence of Fe(II) may be connected with decantation which has been observed for lake sediments, the majority of Fe(III) with upper flow regime erosion-deposition processes, observed for river sediment deposition during flood episodes. As verification for this hypothesis, the explanation for the iron speciation in the different river sediment samples has been used.

Iron species determination by task-specific ionic liquid-based in situ solvent formation dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry

BACKGROUND

The task-specific ionic liquid (TSIL) of 1-ethyl-3-methylimidazolium bromide functionalized with 8-hydroxyquinoline was used as a chelating agent and extracting solvent for dispersive liquid-liquid microextraction and subsequent determination of Fe(III) by flame atomic absorption spectrometry. The in situ solvent formation of TSIL using KPF₆ provided the desired water-immiscible ionic liquid. The total Fe concentration could be determined after pre-oxidation of Fe(II) to Fe(III). Various factors affecting the proposed extraction procedure were optimized.

RESULTS

The proposed analytical conditions were: sample pH 5, TSIL amount 0.3% (w/v), KPF₆ amount 0.15% (w/v), anti-sticking 0.1% (w/v) and salt concentration 5% (w/v). Under optimal conditions, the linear dynamic ranges for Fe(III) and total Fe were 20-80 and 20-110 ng mL^-1 , respectively, with a detection limit of 6.9 ng mL^-1 for Fe(III) and relative standard deviation of 2.2%. The proposed method was successfully applied to the determination of trace Fe(III) in water (underground, tap, refined water and artificial sea water) and beverage (apple, tomato, and tea) samples.

CONCLUSION

The developed method offers advantages such as simplicity, ease of operation, and extraction of Fe(III) from aqueous solutions without the use of organic solvent. It was successfully applied for iron speciation in different real samples. © 2017 Society of Chemical Industry.

The long term tsunami impact: Evolution of iron speciation and major elements concentration in tsunami deposits from Thailand

The article describes the unique studies of the chemical composition changes of new geological object (tsunami deposits in south Thailand - Andaman Sea Coast) during four years (2005-2008) from the beginning of formation of it (deposition of tsunami transported material, 26 December 2004). The chemical composition of the acid leachable fraction of the tsunami deposits has been studied in the scope of concentration macrocompounds - concentration of calcium, magnesium, iron, manganese and iron speciation - the occurrence of Fe(II), Fe(III) and non-ionic iron species described as complexed iron (Fe complex). The changes of chemical composition and iron speciation in the acid leachable fraction of tsunami deposits have been observed with not clear tendencies of changes direction. For iron speciation changes the transformation of the Fe complex to Fe(III) has been recorded with no significant changes of the level of Fe(II).

Evaluation of Safety of Iron-Fortified Soybean Sprouts, a Potential Component of Functional Food, in Rat

Ferritin-iron is currently considered as one of the most promising iron forms to prevent iron deficiency anaemia. We found that the cultivation of soybean seeds in a solution of ferrous sulfate results in material with extremely high iron content - 560.6 mg Fe/100 g of dry matter, while ferritin iron content was 420.5 mg/100 g dry matter. To assess the potential adverse effects of a preparation containing such a high concentration of iron, male and female Wistar rats were exposed via diet to 10, 30, 60 g soybean sprouts powder/kg feed for 90 days. There were no differences in final body weight and mean food consumption between controls and rats administered sprouts. No statistically significant differences in haematology and clinical chemistry parameters were found between controls and treated rats. Microscopic examination of 22 tissues did not reveal any pathology due to soybean sprouts intake. Long term administration of the test material did not cause oxidative damage to DNA and protein in the liver as evidenced by the unchanged basal levels of DNA damage as well as carbonyl groups content. Lipid peroxidation was slightly increased only in females. The activity of several antioxidant enzymes: superoxide dismutase, glutathione peroxidase and glutathione S-transferase was increased, which substantially enhanced the antioxidant status in the liver from the rats treated with soybean sprouts. Hence, the material tested can be recommended as a component of food supplements for individuals with iron deficiency anaemia and inflammatory bowel diseases.

Plant ferritin--a source of iron to prevent its deficiency

Iron deficiency anemia affects a significant part of the human population. Due to the unique properties of plant ferritin, food enrichment with ferritin iron seems to be a promising strategy to prevent this malnutrition problem. This protein captures huge amounts of iron ions inside the apoferritin shell and isolates them from the environment. Thus, this iron form does not induce oxidative change in food and reduces the risk of gastric problems in consumers. Bioavailability of ferritin in human and animal studies is high and the mechanism of absorption via endocytosis has been confirmed in cultured cells. Legume seeds are a traditional source of plant ferritin. However, even if the percentage of ferritin iron in these seeds is high, its concentration is not sufficient for food fortification. Thus, edible plants have been biofortified in iron for many years. Plants overexpressing ferritin may find applications in the development of bioactive food. A crucial achievement would be to develop technologies warranting stability of ferritin in food and the digestive tract.