Simultaneous speciation of selenomethionine and 2-hydroxy-4-methylselenobutanoic acid by HPLC–ICP MS in biological samples

An analytical method was developed for the simultaneous speciation of selenomethionine (SeMet) and 2-hydroxy-4-methylselenobutanoic acid (NutraSelen^®), a new SeMet precursor. The compounds could be baseline resolved by ion-pairing reversed-phase HPLC using ICP MS detection. Detection limits of 1 ng mL^?1 (Se content) could be reached. SELM-1 reference material was used to validate the SeMet measurement. Additionally, the quantification of NutraSelen^® was validated by standard addition together with checking the Se mass balance. The procedure developed was then applied to the monitoring of the conversion of NutraSelen^® into SeMet by yeast.     

Validation of method for total selenium determination in yeast by flame atomic absorption spectrometry

A procedure using open digestion followed by flame atomic absorption spectrometry is described for measuring the total selenium content of Se-enriched yeast. The limits of detection and quantitation were 2.5 mg/L and 5 mg/L Se, respectively. The signal response was linear over the range of 5–50 mg/L Se, and the average recovery from spiked samples was 98.9%. The validated method was used to measure the Se content of Se-enriched yeast reference material and produced a result of 2145±38 mg/kg (n=3), which is in good agreement with the certified level of 2125 ±65 mg/kg.     

Room Temperature Ionic Liquid-Based Dispersive Liquid Phase Microextraction for the Separation/Preconcentration of Trace Cd2+ as 1-(2-pyridylazo)-2-naphthol (PAN) Complex from Environmental and Biological Samples and Determined by FAAS

The current work develops a new green methodology for the separation/preconcentration of cadmium ions (Cd²⁺) using room temperature ionic liquid-dispersive liquid phase microextraction (RTIL–DLME) prior to analysis by flame atomic absorption spectrometry with microsample introduction system. Room temperature ionic liquids (RTIL) are considered “Green Solvents” for their thermally stable and non-volatile properties, here 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] was used as an extractant. The preconcentration of Cd²⁺ in different waters and acid digested scalp hair samples were complexed with 1-(2-pyridylazo)-2-naphthol and extracted into the fine drops of RTILs. Some significant factors influencing the extraction efficiency of Cd²⁺ and its subsequent determination, including pH, amount of ligand, volume of RTIL, dispersant solvent, sample volume, temperature, and incubation time were investigated in detail. The limit of detection and the enhancement factor under the optimal conditions were 0.05 μg/L and 50, respectively. The relative standard deviation of 100 μg/L Cd²⁺ was 4.3 %. The validity of the proposed method was checked by determining Cd²⁺ in certified reference material (TM-25.3 fortified water). The sufficient recovery (>98 %) of Cd²⁺ with the certified value. The mean concentrations of Cd in lake water 13.2, waste water 15.7 and hair sample 16.8 μg/L, respectively and the developed method was applied satisfactorily to the preconcentration and determination of Cd²⁺ in real samples.     

Development of a Rapid and Simple Digestion Method of Freshwater Sediments for As,Cd, Cr,Cu, Pb,Fe, and Zn Determination by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES): An Evaluation of Dilute Nitric Acid

In this study, a simple and rapid methodology based on the hot-plate digestion method using dilute nitric acid solution was used to extract trace metals (such as As, Cd, Cr, Cu, Pb, Fe, and Zn) from freshwater sediments. The concentrations of the elements were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). The factors (temperature, nitric acid concentration, and volume) affecting the digestion method were optimized using one-factor-at-a-time (OFAT) or univariate methodology, and the optimization process was carried out using freshwater sediment certified reference material (CRM015). The optimal conditions for temperature, nitric acid concentration, and time in the method were 180°C, 10 mL of 5 mol L^?1 HNO₃, and 45 min, respectively. Under optimum conditions, the limit of detection (LOD) ranged between 0.02 and 0.08 µg L^?1 and the limit of quantification (LOQ) ranged from 0.07 and 0.27 µg L^?1. In addition, the method detection limits (MDLs) and method quantification limits (MQLs) were 0.10–0.17 and 0.30?0.57 µg g^?1, respectively. The overall accuracy of the method determined by recovery of the trace elements in the CRMs ranged from 98 to 111% with the precision ranging from 1.4 to 5.8%. The method was successfully applied for the determination of target metals from real freshwater sediment samples.     

Metabolic and bioprocess engineering for production of selenized yeast with increased content of seleno-methylselenocysteine

Specific Se-metabolites have been recognized to be the main elements responsible for beneficial effects of Se-enriched diet, and Se-methylselenocysteine (SeMCys) is thought to be among the most effective ones. Here we show that an engineered Saccharomyces cerevisiae strain, expressing a codon optimized heterologous selenocysteine methyltransferase and endowed with high intracellular levels of S-adenosyl-methionine, was able to accumulate SeMCys at levels higher than commercial selenized yeasts. A fine tuned carbon- and sulfate-limited fed-batch bioprocess was crucial to achieve good yields of biomass and SeMCys. Through the coupling of metabolic and bioprocess engineering we achieved a ～24-fold increase in SeMCys, compared to certified reference material of selenized yeast. In addition, we investigated the interplay between sulfur and selenium metabolism and the possibility that redox imbalance occurred along with intracellular accumulation of Se. Collectively, our data show how the combination of metabolic and bioprocess engineering can be used for the production of selenized yeast enriched with beneficial Se-metabolites.     

The Use of Fungal Biomass Agaricus bisporus Immobilized on Amberlite XAD-4 Resin for the Solid-Phase Preconcentration of Thorium

Solid-phase extraction method was developed for the preconcentration of thorium (Th). Fungal biomass Agaricus bisporus was immobilized to Amberlite XAD-4 as solid-phase sorbent. The critical parameters such as pH of the sample solution, flow rate of the sample, volume of the sample, and the effect of major ions that affect the preconcentration of thorium in this system were evaluated. The optimum pH for the sorption of Th is 6.0, and quantitative elution occurs with 1.0 mol L^?1HCl. The loading capacity was determined as 0.079 mmol g^?1. The optimized method was validated through analysis of the certified reference material of tea leaves (NCS ZC73014) and successfully applied to the determination of Th in a real ore sample with satisfactory results.     

A multicomponent method for Fusarium toxins in cereal based food and feed samples using HPLC-MS/MS

A reliable, sensitive and selective multicomponent method has been developed to determine 12 differentFusarium mycotoxins (trichothecenes type A and B, zearalenone) simultaneously in cereal and grain samples using liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). The sample preparation based on a standard extraction step followed by two different kinds of solid phase clean-up (multifunctional MycoSep^® material) for trichothecenes, and an immuno-affinity purification which combined antibodies for aflatoxins, ochratoxin A and zearalenone (AOZ-IAC). For quantification of zearalenone (ZON) an internal standard (zearalanone, ZAN) was used, whereas for trichothecenes a recovery standard (verrucarol, VOL) was applied. The average recoveries for the trichothecenes ranged from 65% for nivalenol (NIV) up to 96% for deoxynivalenol (DON) and 89% for zearalenone. The limit of quantification is different for each of the individual trichothecenes and in the range of 1 ppb to 10 ppb.     

Onsite chelate resin solid-phase extraction of rare earth elements in natural water samples: its implication for studying past redox changes by inorganic geochemistry

Rare earth element (REE) patterns in natural water and geological samples provide information on previous changes in environmental conditions, such as redox changes and material cycles; however, quantitative analysis of REEs in these samples is complicated by the relatively low contents of REEs in such samples as well as mass interference from ¹³⁵Ba¹⁶O and ¹³⁷Ba¹⁶O in inductively coupled plasma mass spectrometry (ICP-MS) analyses. In this study, onsite solid-phase extraction and preconcentration methods for REEs using an iminobisacetic acid–ethylenediaminetriacetic acid chelate resin (Nobias Chelate PA1, Hitachi High-Tech Fielding) were adopted for the analyses. Standard reference materials (SPS-SW1 artificial surface water) and natural ground water and spring water samples were used to evaluate the methods. Using the chelate resin, background levels of REEs were found to be less than 0.3 ng L^?1 and recovery rates (REEs, 1 ng L^?1) were 97.9–106.7% for the artificial surface water. Ba contents were lower than the detection limit after extraction. Additionally, duplicate analyses were performed to check the reproducibility of the onsite extraction. The REE patterns in the natural water samples were in good agreement with those obtained using a previous method (the interference calibration method without solid-phase extraction). Therefore, onsite solid-phase extraction using the chelate resin was demonstrated to be a rapid and simple preparation technique for REE analyses.     

Single laboratory evaluation of a planar waveguide-based system for a simple simultaneous analysis of four mycotoxins in wheat

The accuracy and precision of a commercially available system based on an indirect competitive immunoassay and planar waveguide technology was evaluated for the analysis of deoxynivalenol (DON), ochratoxin A (OTA), zearalenone (ZEAR), and T-2 toxin in wheat. The system generally performed well at the tested concentrations that were close to the regulatory limits of DON and OTA in wheat. The mean percent recovery of OTA from certified and in-house reference materials ranged from 90 to 111 %, with a relative standard deviation of 8–16 % (at 4.2, 4.9, and 7.0 μg/kg). Mean percent recoveries of DON ranged from 75 to 103 %, with a relative standard deviation of 14–20 % (at 610, 940, and 1300 μg/kg). As analyte concentrations approached the lower limits of the working range of 3 μg/kg OTA and 400 μg/kg DON, the mean percent recoveries and relative standard deviation increased for both DON and OTA. A lack of reference materials precluded a thorough evaluation of the method for the analysis of ZEAR and T-2. The particular strength of the technology was that multiple mycotoxins were analyzed simultaneously.     

A process optimization study on ultrasonic extraction of paclitaxel from Taxus cuspidata

This study aimed to improve the extraction rate of paclitaxel from Taxus cuspidata in order to determine the most effective combination of ultrasonic extraction and thin-layer chromatography–ultraviolet (TLC-UV) rapid separation method. The study was performed using the Box–Behnken test design to conduct single-factor experiments using ultrasonic extraction of paclitaxel from Taxus cuspidata. The study showed ethanol to be the best extraction solvent. When mixed with dichloromethane (1:1), the ratio of material to liquid was 1:50 when using an ultrasonic time of 1 hr at a power of 200 W. The correction coefficient K for the separation and detection of paclitaxel using the TLC-UV spectrophotometric method was 0.009152. Multifactor experiments determined the effect of the rate of liquid to material (X1), ultrasonic time (X2), and ultrasonic power (X3) on extraction using extraction volume as the dependent variable. Response surface analysis allowed a regression equation to be obtained, with the optimal conditions for extraction when the rate of liquid to material was 53.23 mL/g as an ultrasonic time of 1.11 hr and an ultrasonic power of 207.88 W. Using these parameters, the average amount of extracted paclitaxel was about 130.576 µg/g, which was significantly better than for other extraction methods.     

An improved process for cell disruption and astaxanthin extraction from Phaffia rhodozyma

Phaffia rhodozyma is one of the most important natural sources of the carotenoid astaxanthin, and the key process for extracting intracellular astaxanthin is disrption of the thick cell wall. In this work, an improved process for cell disruption and astaxanthin extraction from Phaffica rhodozyma was studied using an autoclave at low acid concentration. Under the optimum conditions (HCl 0.5 M and autoclave pressure 0.1 Mpa, 15 min), the relative residual astaxanthin and astaxanthin extractability reached 90.4 ± 3.5% and 84.8 ± 3.2%, respectively. The scanning electron microscopy pictures showed that all yeast cells shattered into fragments after autoclave treatment at low acid concentration condition, whereas cells were intact or partly broken after treatment by some other physical and chemical processes. This new method left no residual toxin and gavehigher extraction recovery, with good prospects for industrial use.     

Highly Simple Deep Eutectic Solvent Extraction of Manganese in Vegetable Samples Prior to Its ICP-OES Analysis

In the present work, simple and sensitive extraction methods for selective determination of manganese have been successfully developed. The methods were based on solubilization of manganese in deep eutectic solvent medium. Three deep eutectic solvents with choline chloride (vitamin B4) and tartaric/oxalic/citric acids have been prepared. Extraction parameters were optimized with using standard reference material (1573a tomato leaves). The quantitative recovery values were obtained with 1.25 g/L sample to deep eutectic solvent (DES) volume, at 95 °C for 2 h. The limit of detection was found as 0.50, 0.34, and 1.23 μg/L for DES/tartaric, DES/oxalic, and DES/citric acid, respectively. At optimum conditions, the analytical signal was linear for the range of 10–3000 μg/L for all studied DESs with the correlation coefficient >0.99. The extraction methods were applied to different real samples such as basil herb, spinach, dill, and cucumber barks. The known amount of manganese was spiked to samples, and good recovery results were obtained.     

Two strings to the systems biology bow: co-extracting the metabolome and proteome of yeast

Experimental samples are valuable and can represent a significant investment in time and resources. It is highly desirable at times to obtain as much information as possible from a single sample. This is especially relevant for systems biology approaches in which several ‘omics platforms are studied simultaneously. Unfortunately, each platform has a particular extraction methodology which increases sample number and sample volume requirements when multiple ‘omics are analyzed. We evaluated the integration of a yeast extraction method; specifically we explored whether fractions from a single metabolite extraction could be apportioned to multiple downstream ‘omics analytical platforms. In addition, we examined how variations to a chloroform/methanol yeast metabolite extraction regime influence metabolite recoveries. We show that protein suitable for proteomic analysis can be recovered from a metabolite extraction and that recovery of lipids, while reproducible, are not wholly quantitative. Higher quenching solution temperatures (?30 °C) can be used without significant leakage of intracellular metabolites when lower fermentation temperatures (20 °C) are employed. However, extended residence time in quenching solution, in combination with vigorous washing of quenched cell pellets, leads to extensive leakage of intracellular metabolites. Finally, there is minimal difference in metabolite amounts obtained when metabolite extractions are performed at 4 °C compared to extractions at ?20 °C. The evaluated extraction method delivers material suitable for metabolomic and proteomic analyses from the same sample preparation.     

SeMet Inhibits IL-1β-Induced Rheumatoid Fibroblast-Like Synoviocytes Proliferation and the Production of Inflammatory Mediators

Previous studies demonstrated that Se has anti-inflammatory activities and that it plays an important role in maintaining normal cartilage metabolism. Nevertheless, little is known about the effects of Se on the production of inflammatory mediators in rheumatoid fibroblast-like synoviocytes (FLSs). The objective of this study was to determine the effects of Se on the interleukin-1β (IL-1β)-induced proliferation of FLSs and production of matrix metalloproteinases (MMPs) and inflammatory mediators by FLSs. In this study, the proliferation of FLSs was assessed using the MTT assay after cultured with/without the presence of IL-1β and SeMet. Human FLSs were pretreated with SeMet (0.5 μM) and subsequently stimulated with IL-1β (5 ng/ml) for 24 h. Production of NO and PGE2 were evaluated by the Griess reaction and ELISA. Gene expression of MMP-3, MMP-13, iNOS, and COX-2 was measured by real-time PCR. MMP-3 and MMP-13 proteins in culture medium were determined using cytokine-specific ELISA. Western immunoblotting was used to analyze the iNOS and COX-2 protein production in the culture medium and the activity of phosphorylation of P38 MAPK pathways. We found that SeMet significantly inhibits IL-1β-induced proliferation of FLSs. SeMet also inhibited the production of PGE2 and NO induced by IL-1β. SeMet significantly decreased IL-1β-stimulated gene expression and production of MMP-3, MMP-13, iNOS, and COX-2 in human FLSs. In addition, we found SeMet partly inhibited the IL-1β-induced activation of p38 MAPK pathways. The present report is first to demonstrate that SeMet inhibits IL-1β-induced expression of MMPs and production of inflammatory factors in cultured FLSs, indicating that SeMet may be a potential agent in the treatment of rheumatoid arthritis.     

Concurrent quantitative HPLC–mass spectrometry profiling of small selenium species in human serum and urine after ingestion of selenium supplements

Selenium metabolic patterns in the human body originating from five distinct selenium dietary sources, selenate, selenite, selenomethionine (SeMet), methylselenocysteine (MeSeCys) and selenized yeast, were investigated by performing concurrent HPLC–mass spectrometric analysis of human serum and urine. Total selenium and selenium species time profiles were generated by sampling and analyzing serum and urine from volunteers treated with selenium supplements, up to 5 and 24 h following ingestion, respectively. We found that an increase in total serum selenium levels, accompanied by elevated selenium urinary excretion, was the common pattern for all treatments, except for that of selenite supplementation. Selenosugar 1 was a universal serum metabolite in all treatments, indicating that ingested selenium is favorably metabolized to the sugar. Except for selenite and selenized yeast ingestion, these patterns were reflected in the urine time series of the different treatments. Selenosugar 1 was the major selenium species present in urine in all treatments except for the selenate treatment, accounting for about 80% of the identified excreted species within 24 h of ingestion. Furthermore, the urinary metabolite trimethylselenonium ion (TMSe) was detected for the first time in human background serum by using HPLC coupled to elemental and molecular mass spectrometry. The concurrent monitoring of non-protein selenium species in both body fluids provides the relation between bioavailability and excretion of the individual ingested species and of their metabolic products, while the combined use of elemental and molecular mass spectrometry enables the accurate quantitation of structurally confirmed species. This successfully applied approach is anticipated to be a useful tool for more extensive future studies into human selenium metabolism.     

Alterations of Mg<Superscript>2+</Superscript> After Hemorrhagic Shock

The objectives of this study were to measure the concentrations of elements in raw milk by inductively coupled plasma-mass spectrometry (ICP-MS) and evaluate differences in element concentrations among animal species and regions of China. Furthermore, drinking water and feed samples were analyzed to investigate whether the element concentrations in raw milk are correlated with those in water and feed. All samples were analyzed by ICP-MS following microwave-assisted acid digestion. The mean recovery of the elements was 98.7 % from milk, 103.7 % from water, and 93.3 % from a certified reference material (cabbage). Principal component analysis results revealed that element concentrations differed among animal species and regions. Correlation analysis showed that trace elements Mn, Fe, Ni, Ga, Se, Sr, Cs, U in water and Co, Ni, Cu, Se, U in feed were significantly correlated with those in milk (p < 0.05). Toxic and potential toxic elements Cr, As, Cd, Tl, Pb in water and Al, Cr, As, Hg, Tl in feed were significantly correlated with those in milk (p < 0.05). Results of correlation analysis revealed that elements in water and feed might contribute to the elements in milk.     

Recovery of residual soluble protein by two-step precipitation process with concomitant COD reduction from the yeast-cultivated cheese whey

The present study was conducted to recover the residual soluble protein after cultivation of yeast (K. marxianus) in cheese whey. Cheese whey continuous fermentation with cell recycle system was carried out at 40 °C and pH 3.5. The yeast biomass was separated from the fermented broth by centrifugation and residual soluble protein from fermented whey supernatant was precipitated by heat treatment (at 100 °C, pH 4.5 and 10 min incubation). The maximum soluble protein recovery up to 53 % was achieved at pH 4.5 with 54 % residual COD removal. However, gravity sedimentable precipitates were obtained at pH 3.5 with 47 % protein recovery. Therefore, the reactor (scale up) study was conducted at pH 3.5 with agitation, which resulted in 68 % of residual soluble protein recovery and simultaneously residual COD removal of 62 %. Further precipitation/coagulation of soluble protein was also evaluated using carboxymethylcellulose (CMC) and then two precipitation (thermal followed by CMC precipitation) processes were combined to increase the protein precipitation, which finally reached up to 81 % of total soluble protein recovery from the supernatant. This optimized process could be applied to recover the residual protein left after fermentation of cheese whey without centrifugation.     

Anoxybacillus sp. SO B1–Immobilized Amberlite XAD-16 for Solid-Phase Preconcentration of Cu(II) and Pb(II) and Their Determinations by Flame Atomic Absorption Spectrometry

A new method for the determination of Cu(II) and Pb(II) by flame atomic absorption spectrometry (FAAS) after preconcentrating on a column containing Anoxybacillus sp. SO B1–immobilized Amberlite XAD-16 was developed. The functional groups of Anoxybacillus sp. SO B1 immobilized on Amberlite XAD-16 were characterized in KBr tablets by Fourier transform infrared (FT-IR) spectrometry. Various parameters such as pH, amount of the adsorbent, eluent type and volume, and flow rate of the sample solution were studied. The optimum pH values of quantitative sorption for Cu(II) and Pb(II) were found to be pH 7.0 and 5.0 and Cu(II) and Pb(II) ions could be quantitatively eluted with 5.0 ml of 1.0 mol L^?1 HCI and 10.0 ml of 0.25 mol L^?1 HNO₃, respectively. Recoveries of Cu(II) and Pb(II) were found to be 100.9 ± 1.57% and 100.3 ± 0.49% (N = 5), the limits of detection of Cu(II) and Pb(II) in the determination by FAAS (3 s, N = 10) were found to be 0.8 and 1.6 μg L^?1, respectively. The proposed enrichment method was applied for metal ion determination from water samples such as two parts of Tigris River water in Diyarbak?r and Elaz??, Lake of Hazar in Elaz??, and tap water in Diyarbak?r. Furthermore, the accuracy of the proposed method was verified by studying the analytical recovery and by analyzing certified reference material (NCS-DC 73350 leaves of poplar).     

Determination of selenium in duplicate diets of residents of Pinhel,Portugal, by neutron activation

A rapid cyclic instrumental neutron activation analysis (CINAA) method has been used to determine the selenium content of 27 duplicate diet samples from each of the 27 districts surrounding Pinhel, Portugal. The accuracy and precision of the CINAA method have been evaluated by analyzing certified reference materials and observed to be within ±5–10% for samples containing at least 40 ppb of selenium. The detection limit has been found to vary between 26–42 ppb selenium depending on the sample composition. The average daily dietary intake has been calculated as 37 μg of selenium per day.