HCl Extraction Research Articles

The use of Agrochemicals for inc BIOAVAILABILITY OF HEAVY METALS Pb AND Cd IN LAND FOR CULTIVATYING CABBAGE IN KINTAMANI AREA BANGLI

The use of Agrochemicals for increasing the agricultural products are commonly applied on agricultural soils, especially the soil used for cultivatif cabbage in the area of Kintamani-Bangli, Province of Bali. Agricultural soils used for cultivatif cabbage in Kintamani area commonly apply inorganic fertilizers and synthetic pesticides for increasing the products. However the use of these agrochemicals tends to uncontrol and causes the soils polluted. One factor of contamination of soil is the presence of heavy metals in the soil. Intensive use of inorganic fertilizers and synthetic pesticides can lead to high levels of bioavailability of heavy metals in plants. This study intend to determine the total contents of heavy metals Pb and Cd in the agricultural soils and analyse bioavilability of those metals. The total metals was determined by the use of digestion method involving reverse aquaregia (HNO3:HCl, 3:1) and the bioavailability of the metals was determined by applying single extraction including HCl and EDTA extractions. The results show that the total contents of Pb and Cd in the soils were 4,1261 ± 0,1113 – 14,5923 ± 0,3790 mg/kg and 0,8803 ± 0,0259 - 0,9425 ± 0,0195 mg/kg respectively. The bioavailable metals of Pb and Cd in the soils was 31,14% - 42,53% and 78,70% - 80,73%, respectively.

Transformation of Phosphorus in Speciation and Bioavailability During Converting Poultry Litter to Biochar

Converting poultry litter (PL) to biochar and applying the biochar to cropland as a soil amendment may be a best approach for recovering nutrients from solid biowastes while minimizing the nutrient runoff losses from the treated field. To evaluate the potential of PL-derived biochar as a slow-release phosphorus (P) fertilizer, the speciation, mobilitylability, and bioavailability of P in PL and the derived biochars were examined and compared. Raw PL and its derived biochars through 300–600°C slow pyrolysis were analyzed for total P (TP), inorganic P (IP), and organic P (OP) contents. The TP was fractionated into readily, generally, moderately, low, and non-labile pools by sequential extraction with different solutions. The TP was further assessed for bioavailability using batch extraction by water, Olsen, Bray-1, Mehlich-3, and 1 M HCl extractants. The P species in biochars were characterized using solid-state 31P nuclear magnetic resonance (NMR) techniques. The results indicate that during pyrolysis OP in PL was transformed to IP and water-soluble P to low labile forms such as hydroxyapatite and oxyapatite especially during pyrolysis, initially to polyphosphate-P and subsequently to orthophosphate-P at higher temperature. Orthophosphate-P was the predominant form in biochar, with products from higher pyrolysis temperature demonstrating reduced labile P pools yet enlarged low to non-labile fractions. Bray-1 and Mehlich-3 were appropriate extractants for evaluating the immediate to medium-term available and the long-term available P in biochar, respectively. Converting PL to biochar through 450°C pyrolysis significantly reduced the water-soluble proportion and the lability of P but did not compromise the long-term P bioavailability, resulting in a P-enriched, slow release soil amendment that would minimize the P runoff risks following field application. The promising results need to be further validated in soil-biochar-plant systems.

Extraction, characterization and immunomodulatory property of pectic polysaccharide from pomegranate peels: Enzymatic vs conventional approach

Molecular characteristics, structural properties and immunostimulatory activities of polysaccharides from pomegranate peel were evaluated after 0.1 M HCl, Cellic CTec2 and buffer extractions. The isolated polysaccharides were mainly formed of neutral sugars (32.1%–51.1%) and uronic acids (19.9%–30.8%) as well as varying levels of proteins (15.0%–39.5%). Different levels of sugars including glucose (44.9%–68.1%), galactose (14.6%–19.4%), mannose (3.4%–18.1%), arabinose (3.1%–18.1%) and rhamnose (3.5–6.0%) constructed the structure of isolated polysaccharides. The average molecular weight (Mw) of polysaccharides differed notably and ranged from 422.5 × 103 to 18,631.8 × 103 g/mol. Polysaccharide molecules obtained using Cellic CTec2 enzyme induced RAW264.7 murine macrophage cells to release considerable amount of inflammatory mediators including nitric oxide, IL-1β, TNF-α, IL-6 and IL-10. The polysaccharide stimulation of macrophage cells initiated through NF-κB and MAPKs signaling pathways and activation of p-NF-κB, p-JNK, p-ERK and p-p38 proteins. The most potent immunostimulatory polysaccharides were consisted of (1 → 3)-linked glucose, (1 → 6)-linked galactose, (1 → 4)-linked mannose and (1 → 4)-linked arabinose residues with branching points at C6 and C3. These results indicated that the lower molecular weight of polysaccharides isolated with Cellic CTec2 enzyme could be one of the major determinant structural characteristics in stimulating macrophage cells.

Simple Extraction Cum RP-HPLC Method for Estimation of Nanotized Quercetin in Serum and Tissues of Mice

In recent years, several studies have focused on antioxidant, anti-inflammatory, and anti-cancer activities of quercetin (3,3′,4′,5, -pentahydroxyflavone). The nanotization of quercetin was shown to enhance its therapeutic efficacy due to smaller particle size. In the present study, an additional step was added to simple extraction cum RP-HPLC method for the quantification of nanotized quercetin (nQ) in biological samples to understand the pharmacokinetics and biodistribution of nQ following intravenous administration. The proposed method involves extraction of nQ from blood serum and tissues of mice with 2N HCl in comparison to well-known DMSO:MeOH mix method. The HCl extraction was found to be 2 – 3 times more efficient than DMSO:MeOH mix method. Results showed that the amount of nQ at various time intervals in the serum and tissues was 2 – 3 fold greater for HCl extraction than for DMSO:MeOH mix method, suggesting that HCl extraction must take into account nQ bound with protein. The reversed-phase HPLC was used for nQ detection, which showed the nQ retention time of 3.2 min. The limit of detection of nQ in blood serum was found to be 0.1 μg/mL. The proposed method was also validated in terms of linearity, precision, and accuracy.

Rhodosporidium sp. GROWTH IN MOLASSES MEDIUM AND EXTRACTION OF ITS ASTAXANTHIN BY USING HCl

Astaxanthin is classified as a xanthophyll-carotenoid, which is red-orange colour and powerful antioxidant activity. In this study, astaxanthin was collected from Rhodosporidum sp. by pilot culture (10 liters). Molasses medium was investigated with urea ((NH4)2CO), magnesium sulfate heptahydrate (MgSO4.7H2O) and potassium dihydrogen phosphate (KH2PO4) at different concentrations. Astaxanthin was extracted by using chlorhydric acid (HCl) method.The highest dried yeast biomass was 8.3682 g/l culture supernatant and astaxathin was 1.932 g/l culture supernatant by molasses medium containing 20 g/l sugar, 0.5 g/l ((NH4)2CO, 3 g/l MgSO4.7H2O and 10 % (v/v) inoculum. HCl extraction method was mixed 10 mg biomass: 1 ml HCl 0.6 N and incubated at 70 oC, 150 minutes.

Application of response surface methodology to acidified water extraction of black soybeans for improving anthocyanin content, total phenols content and antioxidant activity

Acidified water extraction of total anthocyanin content, total phenol content and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging activity from black soybeans (Glycine max [L.] Merr. Cheongja4ho) was optimized using response surface methodology (RSM). A five-level, three-factor central composite design was employed to optimize the conditions for the maximum yields of these three components using19 different experiments. The HCl concentration (0.3–0.5%), solid-liquid ratio (1/30–1/50 g/mL) and extraction temperature (30–50 °C) significantly affected three components. The optimized conditions were HCl concentration of 0.359%, solid-liquid ratio of 1/54.2 g/mL and extraction temperature of 56.8 °C for total anthocyanin content (136.68 mg/100 g), total phenol content (1197.09 mg/100 g) and ABTS+ scavenging activity (211.65 mg/100 g). These experimental values fit well with the predicted values. Among three anthocyanins found in the black soybean extracts, cyanidin-3-O-glucoside was the major one (65–73% of the total), followed by petunidin-3-O-glucoside (17–23%) and delphinidin-3-O-glucoside (10–12%).

Molybdenum(VI) Coordination in Tributyl Phosphate Chloride Based System

Fundamental coordination chemistry of Mo(VI) at its macroconcentrations in solvent extraction systems is of great importance for industrial processes that require the purification or recovery of large concentrations of Mo. The coordination of Mo(VI) in tri-n-butyl phosphate (TBP) from solutions of hydrochloric acid and up to 0.3 M Mo was investigated using UV, FTIR, and 31P NMR spectroscopies, as well as EXAFS. From these techniques we resolved near-neighbor atoms, speciation, structural information on the coordination environment, and thermodynamic parameters affiliated with the solvent extraction of Mo(VI) and HCl. The solvated extracted form of Mo(VI) as MoO2Cl2·2TBP was identified. High extraction yield of Mo at >5 M HCl concentration is driven by replacing HCl in the organic phase by Mo. The existence of additional organic Mo adducts is also discussed with the aid of density functional theory, however no evidence of dimeric or polymeric Mo species was found to be present in TBP.

Bioaccessible trace metals in lip cosmetics and their health risks to female consumers

Females can be exposed to toxic elements in lip cosmetics following ingestion. The bioaccessibility of Cr, Mn, Co, Ni, Cu, Cd, Sb and Pb in lip cosmetics (n = 32) were assessed via the dilute HCl extraction method, In Vitro Gastrointestinal protocol (IVG) and the United States Pharmacopeia Methodology (USPM), and then health risks were characterized. The total concentrations of trace metals (TMs) in lip cosmetics were in the range of 15.55–111.97 mg/kg (Mean: 60.99 mg/kg). Cu, Pb and Cr were the three major TMs and accounting for >75% of the total concentrations. Except Sb and Pb in 4/32 and 4/32 samples were higher than the US FDA (Food and Drug Administration of the United States) limits, the other TMs were lower than that limits. Only bioaccessible Pb in all samples significantly exceeded the FDA limit 0.1 mg/kg in candy. Using IVG or USPM might be preferable for evaluating the TMs exposure over HCl since they better represent gastrointestinal physiology. The estimated average daily intake (ADI) of bioaccessible ∑TMs through lip cosmetics ingestion of career women and female college students were under safety level. The long-term exposure of bioaccessible TMs by lip cosmetics using would inevitably cause non-carcinogenic health risk. This is the first report on the in vitro tests used for evaluating bioaccessible TMs in lip cosmetics.

Speciation and bioavailability of heavy metals in pyrolytic biochar of swine and goat manures

The analysis was performed to research the speciation and bioavailability of heavy metals in manures and the biochars obtained from pyrolysis of swine and goat manures. Manures were pyrolyzed at different temperatures (200–800 °C). The concentrations of heavy metals in biochars were found to be higher than those in manures. The remaining ratios of heavy metals in biochar decreased with increasing pyrolysis temperature. Our results demonstrated that heavy metal speciation in biochar was strongly impacted by pyrolysis temperature. The bioavailable heavy metal fractions (acid soluble/exchangeable fraction and reducible fraction) were transformed into the relatively stable fraction (oxidizable fraction) and very stable fraction (residual fraction) during pyrolysis. Moreover, the data of diethylenetriamine pentaacetic acid (DTPA), HCl extraction, and toxicity characteristic leaching procedure (TCLP) in biochar indicated that bioavailability and toxicity of heavy metals in biochar were greatly reduced after pyrolysis. In summary, the pyrolysis process at 500 °C can provide a practical way to decline the bioavailability of heavy metals in manure. Biochar obtained from manure pyrolyzed at 800 °C may minimize the direct and potential heavy metal toxicities of biochar to the environment.

Accumulation of selected heavy metals in soils and common dandelion (Taraxacum officinale) near a road with high traffic intensity

Abstract The aim of the study was to determine the levels of selected trace elements in soils and in the common dandelion depending on the distance from a traffic route. The study was conducted in Warsaw near one of the main roads in the suburb of Ursynów. Samples for testing were taken from the 0–25 cm layer at sites located directly alongside the roadway and at a distance of 30, 60 and 300 m from its edge. The amounts of Pb, Ni, Cu, Zn and Cd in the soils were determined by the AAS method, after extraction in HCl at a concentration of 1 mol·dm−3, and in the aboveground parts and roots of dandelion plants after wet mineralization in a mixture of HNO3 and HClO4 by the AAS method. On the basis of the results obtained, it was shown that the concentrations of the tested metals, both in the soils and in the biomass of the test plant, were highest directly at the edge of the roadway and decreased significantly with the distance away from the road. This correlation indicates a significant impact of road transport on heavy metal levels in the environment bordering a traffic route. It was also shown that dandelion plants accumulate higher amounts of heavy metals in the aboveground parts than in the roots, and the heavy metal contents in the dandelion biomass were found to be significantly positively correlated with the amounts of these elements in the soils.

Phosphate Leaching from Green Roof Substrates—Can Green Roofs Pollute Urban Water Bodies?

Green roofs are an effective stormwater measure due to high water retention capacity and the ability of delaying stormwater runoff. However, low importance is still given to the pollutant leaching potential of substrates used in green roof construction. The aim of the study is to estimate the concentrations and loads of P-PO43− in runoff from extensive and intensive substrates. To achieve this goal, several commonly-used fresh substrates were analyzed for P-PO43− leaching potential in different scale experiments, from laboratory batch tests, leaching column experiments, and long-term monitoring of open air green roof containers. The results of the study confirmed that fresh green roof substrates contain phosphorus in significant amounts of 17–145 mg∙P-PO43−/kg and, thus, can contribute to eutrophication of freshwater ecosystems. High correlation between phosphate content estimated by HCl extraction and cumulative load in leachate tests suggests that the batch HCl extraction test can be recommended for the comparison and selection of substrates with low potential P leaching. Volume-weighted mean concentrations and UALs of P-PO43− leaching from fresh substrates were higher in cases of intensive substrates, but there was no clear relationship between substrate type and the observed P-PO43− concentration range. To avoid increasing eutrophication of urban receivers the implementation of P reduction measures is strongly recommended.

Subcritical water extraction of amino acids from Mars analog soils.

For decades, the Martian regolith has stymied robotic mission efforts to catalog the organic molecules present. Perchlorate salts, found widely throughout Mars, are the main culprit as they breakdown and react with organics liberated from the regolith during pyrolysis, the primary extraction technique attempted to date on Mars. This work further develops subcritical water extraction (SCWE) as a technique for extraction of amino acids on future missions. The effect of SCWE temperature (185, 200, and 215°C) and duration of extraction (10-120min) on the total amount and distribution of amino acids recovered was explored for three Mars analog soils (JSC Mars-1A simulant, an Atacama desert soil, and an Antarctic Dry Valleys soil) and bovine serum albumin (as a control solution of known amino acid content). Total amounts of amino acids extracted increased with both time and temperature; however, the distribution shifted notably due to the destruction of the amino acids with charged or polar side chains at the higher temperatures. The pure bovine serum albumin solution and JSC Mars 1A also showed lower yields than the Atacama and Antarctic extractions suggesting that SCWE may be less effective at hydrolyzing large or aggregated proteins. Changing solvent from water to a dilute (10mM) HCl solution allowed total extraction efficiencies comparable to the higher temperature/time combinations while using the lowest temperature/time (185°C/20min). The dilute HCl extractions also did not lead to the shift in amino acid distribution observed at the higher temperatures. Additionally, adding sodium perchlorate salt to the extraction did not interfere with recoveries. Native magnetite in the JSC Mars-1A may have been responsible for destruction of glycine, as evidenced by its uncharacteristic decrease as the temperature/time of extraction increased. This work shows that SCWE can extract high yields of native amino acids out of Mars analog soils with minimal disruption of the distribution of those amino acids, even in the presence of a perchlorate salt.

A Statistical Review of Alternative Zinc and Copper Extraction from Mineral Fertilizers and Industrial By-Products.

Rapid, accurate, and low-cost alternative analytical methods for micronutrient quantification in fertilizers are fundamental in QC. The purpose of this study was to evaluate whether zinc (Zn) and copper (Cu) content in mineral fertilizers and industrial by-products determined by the alternative methods USEPA 3051a, 10% HCl, and 10% H2SO4 are statistically equivalent to the standard method, consisting of hot-plate digestion using concentrated HCl. The commercially marketed Zn and Cu sources in Brazil consisted of oxides, carbonate, and sulfate fertilizers and by-products consisting of galvanizing ash, galvanizing sludge, brass ash, and brass or scrap slag. The contents of sources ranged from 15 to 82% and 10 to 45%, respectively, for Zn and Cu. The Zn and Cu contents refer to the variation of the elements found in the different sources evaluated with the concentrated HCl method as shown in Table 1. A protocol based on the following criteria was used for the statistical analysis assessment of the methods: F-test modified by Graybill, t-test for the mean error, and linear correlation coefficient analysis. In terms of equivalents, 10% HCl extraction was equivalent to the standard method for Zn, and the results of the USEPA 3051a and 10% HCl methods indicated that these methods were equivalents for Cu. Therefore, these methods can be considered viable alternatives to the standard method of determination for Cu and Zn in mineral fertilizers and industrial by-products in future research for their complete validation.

Quantitative and Qualitative Analyses of Amino Acids in Morinda citrifolia (Rubiaceae)

Background: Amino acids and chemical elements play a lead role in all physiological processes in the human body. The consistency of their composition is one of the most important and critical conditions for normal functioning and development of organisms. The variation in composition of amino acids and elements in the body leads to deterioration in health status. One possibility of timely correction of violations of elemental and amino acid homeostasis in the human body is the use of extracts from medicinal plants. Morinda citrifolia, commonly known as Noni, contains essential amino acids for life. Methods: A total of fourteen essential, conditionally essential and nonessential amino acids were examined by thin-layer chromatography (TLC). Two categories of extraction solutions; aqueous extraction and 1% HCl extraction, were prepared. Total quantity of amino acids in the fruits, leaves and roots of noni were investigated by spectrophotometric method of analysis with glutamic acid solution prepared as a standard. Result: The TLC analysis showed presence and absence of amino acids in the parts investigated. The leaves extracts of noni showed the highest content of amino acids whereas the roots demonstrated the least amino acid content. Methionine, an important ingredient for tissue development and growth were found in the 1% HCl sample extraction analyzed with the leaves and roots of noni. Leucine, a muscle building compound was observed in the fruits of the aqueous sample extraction of noni. Total content of amino acids in alcohol extraction from the roots, leaves and fruits of crude extraction of Morinda citrifolia was much lower than in aqueous extractions. Conclusion: This study confirmed the presence of amino acids in noni. Higher total content of amino acids was observed in aqueous medium as compared to ethanol medium. In conclusion, therefore, aqueous extraction of noni presents an optimal amount of amino acids which play crucial antioxidative roles in living organisms.

Method of determining loosely bound compounds of heavy metals in the soil

Method of determination of heavy metals loosely bound compounds in the soil was developed using three separate extractions. The group of loosely bound compounds of metals includes exchangeable, complexed, and specifically adsorbed forms. This method is available, rapid and not expensive. Extraction takes less than 24?h. Sample procedure preparation is simple, and the analysis consists of only three steps, which can be performed simultaneously. The parallel extraction gives reliable and reproducible results and provides a relatively complete idea of the metals mobility in the soil, their availability to plants, migratory capacity, and transformation.•Method is suitable for a wide range of heavy metals and soil types. From the obtained data, the content of loosely bound compounds of heavy metals and the coefficients of metals mobility in the soil can be calculated.•Method is suitable for estimation the microelement supply of uncontaminated soils. The content of elements in the 1?N CH3COONH4 extract characterizes the actual pool of elements, and their content in the 1?N HCl extract defines their potential pool in the soil.•The coefficient of mobility (Km) is calculated to assess the contamination of soil with heavy metals. Estimation criteria of Km for Haplic Chernozem were developed.

On the Extraction of HCl and H2PtCl6 by Tributyl Phosphate: A Mode of Action Study

ABSTRACTCombining computational modeling with experimental measurements has revealed the self-assembly of nano-aggregate structures in the transfer of HCl and PtCl62– from an aqueous phase into toluene by the common industrial extractant tributyl phosphate (TBP). Molecular dynamics simulations have been coupled to analytical measurements to provide an atomistic interpretation of the mode of action of TBP under 6 M and 10 M HCl conditions. The structures conform to reverse micelles, where the Cl– or PtCl62– core is encapsulated by a hydration shell that acts as a mediating bridge to the electronegative oxygen atom in the TBP phosphate groups. For the 6 M HCl extraction model, the data support stable aggregates forming from 2–3 TBP molecules around one chloride anion if the number of water molecules encapsulating the chloride anion is no more than five; increasing the water content to 10 molecules allows a fourth TBP molecule to coordinate. For the 10 M HCl extraction model, stable structures are obtained that conform to the empirical formula (TBP.HCl.H2O)3–5. At 6 M HCl, extraction of PtCl62– is achieved by encapsulation by four TBP molecules; the data for extraction at 10 M HCl indicate larger aggregates containing multiple PtCl62– anions are likely to be forming. In all cases, the hydrated core regions of the reverse micelles are considerably exposed. The diameters of the self-assembled structures around chloride ions agree well with available literature data from small-angle neutron-scattering experiments.

Iron reduction: a mechanism for dynamic cycling of occluded cations in tropical forest soils?

Nutrient cations can limit plant productivity in highly weathered soils, but have received much less attention than phosphorus and nitrogen. The reduction of iron (Fe) in anaerobic microsites of surface soils can solubilize organic matter and P sorbed or occluded with short-range-ordered (SRO) Fe phases. This mechanism might also release occluded cations. In the Luquillo Experimental Forest, Puerto Rico, we measured cation release during anaerobic laboratory incubations, and assessed patterns of cation availability in surface soils spanning ridge-slope-valley catenas. During anaerobic incubations, potassium (K), calcium (Ca) and magnesium (Mg) significantly increased with reduced Fe (Fe(II)) in both water and 0.5 M HCl extractions, but did not change during aerobic incubations. In the field, 0.5 M HCl-extractable Fe(II) and Fe(III) were the strongest predictors of K, Mg, and Ca on ridges (R2 0.57–0.75). Here, both Ca and Mg decreased with Fe(III), while K, Ca, and Mg increased with Fe(II), consistent with release of Fe-occluded cations following Fe reduction. Manganese in ridge soils was extremely low, consistent with leaching following reductive dissolution of Mn(IV). On slopes, soil C was the strongest cation predictor, consistent with the importance of organic matter for cation exchange in these highly weathered Oxisols. In riparian valleys, cation concentrations were up to 16-fold greater than in other topographic positions but were weakly or unrelated to measured predictors, potentially reflecting cation-rich groundwater. Predictors of cation availability varied with topography, but were consistent with the potential importance of microsite Fe reduction in liberating occluded cations, particularly in the highly productive ridges. This mechanism may explain discrepancies among indices of “available” soil cations and plant cation uptake observed in other tropical forests.

Study of macro and microelements in fish from the Cienfuegos Bay. Relationship with its content in sediments.

Thirteen microelements (Al, As, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Ti, V, and Zn) and four macroelements (Ca, K, Mg, and Na) were determined in the edible muscle tissue of fish in Cienfuegos Bay. Eight species, Albula vulpes, Diapterus rhombeus, Gerres cinereus, Haemulon carbonarium, Haemulon sciurus, Micropogonias furnieri, Kyphosus sectatrix, and Lutjanus cyanopterus were studied. The total concentrations and extracted concentrations using HCl were also determined in sediments. The quality of the analysis was guaranteed by validating the used analytical methods with certified reference materials of fish and sediments. The high content of macroelements confirmed the importance of fish as a valuable source of food for the local population. New information is provided on bioaccumulation of toxic elements As, Cd, Cu, Zn, and Cr in fish of the bay, with concentrations that overcame the local or international maximum allowable levels for human consumption in most samples analyzed. A high correlation between the content of toxic elements As, Cd, Zn, and macroelement K in fish and its concentration extracted from sediments using the HCl extraction method was observed.

A cascading biorefinery process targeting sulfated polysaccharides (ulvan) from Ulva ohnoi

We evaluated eight biorefinery processes targeting the extraction of ulvan from Ulva ohnoi. Using a factorial design the effect of three sequential treatments (aqueous extraction of salt; ethanol extraction of pigments; and Na2C2O4 or HCl (0.05M) extraction of ulvan) were evaluated based on the yield (% dry weight of biomass) and quality (uronic acid, sulfate, protein and ash content, constituent sugar and molecular weight analysis) of ulvan extracted. The aqueous extraction of salt followed by HCl extraction of ulvan gave higher yields (8.2±1.1% w/w) and purity of ulvan than equivalent Na2C2O4 extracts (4.0±1.0% w/w). The total sugar content of HCl extracts (624–670μg/mg) was higher than Na2C2O4 extracts (365–426μg/mg) as determined by constituent sugar with ulvan specific monosaccharides contributing 94.7–96.2% and 70.1–84.0%, respectively. Ulvan extracted from U. ohnoi was 53.1mol% rhamnose, 27.8mol% glucuronic acid, 10.1mol% iduronic acid, and 5.3mol% xylose with molecular weights ranging from 10.5–312kDa depending on the biorefinery process employed. Therefore, the extraction of high quality ulvan from U. ohnoi is facilitated by an aqueous pre-treatment and subsequent HCl-extraction of ulvan as part of a cascading biorefinery model delivering salt, ulvan, and a protein enriched residual biomass.

Optimized high-throughput methods for quantifying iron biogeochemical dynamics in soil

Iron (Fe) redox cycling and sorption/complexation reactions influence numerous soil biogeochemical processes, and the precise, rapid, and low-cost determination of reactive Fe pools is critical for understanding these dynamics. Colorimetric methods are often used to measure Fe, yet assay conditions vary widely among studies, and the robustness of these methods and their potential interferences remain poorly characterized. Here, we developed optimized ferrozine methods (modified from water and sediment protocols) to determine Fe concentrations in three common soil extractions: reduced (Fe(II)) and oxidized Fe (Fe(III)) in 0.5M HCl (FeHCl), and Fe extracted by citrate-ascorbate (Feca) and citrate-dithionite (Fecd). These methods were adapted for 96-well microplates by employing increased buffer concentrations and longer incubation times relative to published cuvette methods. Iron quantitation was sensitive to the final pH of the reaction mixture and duration of incubation period, factors that have varied widely in previous studies. We obtained consistent results with an assay pH near 7, half hour incubations for FeHCl, and 1h incubations for Feca and Fecd. These ferrozine methods compared favorably with inductively coupled plasma optical emission spectrometry (ICP-OES) across a broad range of soils, including Oxisols, Mollisols, and Inceptisols with as much as 18% organic C. Iron determination in HCl extractions from 158 tropical forest soil samples with widely varying C content was not influenced by dissolved organic carbon (DOC) or phenolics at lower Fe concentrations (<2.5mgg−1 soil), and showed only minor effects (<6% overestimation) at higher Fe concentrations. This was likely due to co-variation between Fe and DOC, which measured as high as 691mgCL−1 in a cloud forest soil extract. These microplate-based ferrozine methods can be applied to quantify several reactive soil Fe phases with high precision and throughput, minimal interference, and low cost relative to ICP-OES.