The measurement of total and soluble oxalates followed the method outlined by Savage et al. (2000 ). Three replicates of 5 g of each sample of freshly chopped bitter gourd fruits and wok‐fried fruits and 5 g of the extracted juice were used to measure the total oxalate content, and three replicates were extracted to measure the soluble oxalate contents. Forty ml of 0.2 M HCl (Aristar, BDH Chemicals, Ltd., Poole, Dorset, UK) was added to flasks for the total oxalate extraction, and 40 ml of high purity water (Barnstead International, Dubuque, Iowa, USA, 18 MΩ·cm) was added for the extraction of soluble oxalates. All flasks were placed in an 80°C shaking water bath for 20 min. The solutions were then quantitatively transferred into volumetric flasks, allowed to cool and then made up to 100 ml with 0.2 M HCl and high purity water, respectively.
Aristar
Manufactured by Avantor
Sourced in United Kingdom
Aristar is a line of high-purity laboratory chemicals and reagents produced by Avantor. The products are designed to meet the stringent requirements of analytical and research applications.
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8 protocols using aristar
1
Oxalate Measurement in Bitter Gourd
2
Fatty Acid Profiling via FAME Analysis
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The fatty acid (FA) profile of samples were determined by fatty acid methyl esters (FAME) prepared from total lipid extracts that had undergone acid-catalysed transmethylation at 50 • C for 16 h using 2 ml 1% (v/v) sulphuric acid (95%, Aristar, BDH Chemicals, Poole, UK) in methanol and 1 ml toluene (Christie, 2003) . FAME were extracted and purified according to (Tocher and Harvie, 1988) (link) and separated and quantified by gas-liquid chromatography. Individual FAME were identified by comparison to known standards (in-house marine oil and Restek 20-FAME Marine Oil Standard; Thames Restek UK Ltd., Buckinghamshire, UK), in addition to published literature (Ackman, 1980; (link)Tocher and Harvie, 1988) (link). Data were collected and processed using Chromcard for Windows (Version 2.11; Thermo Fisher Scientific Inc., Milan, Italy) . Fatty acid content per g sample was calculated using heptadecanoic acid (17:0) as internal standard.
3
Standardization of Acid-Base Solutions
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Nitric acid
(HNO3) solutions were prepared at ∼10–1 M by dilution of the concentrated acid (Aristar - VWR Chemicals,
69%) and standardized against sodium carbonate (Aldrich, 99.95–100.5%).
Carbonate-free sodium hydroxide (NaOH) solutions were prepared at
∼10–1 M from commercial pellets (Fluka, 99%
min) using freshly boiled ultrapure water and standardized using the
previously standardized acid. The ligand stock solutions were prepared
by direct dissolution of a weighed portion of ligand in water at ∼10–3 M. HNO3 was coadded to increase the solubility
and avoid carbonatation phenomena. Pb2+ solutions were
preprepared from analytical-grade nitrate salt (Pb(NO3)2, Sigma-Aldrich, 99%) and standardized using complexometric
titrations with ethylenediaminetetraacetic acid (EDTA)
with xylenole orange as an indicator. The ionic strength (I) was fixed to 0.15 M using sodium nitrate (NaNO3) as background electrolytes. All of the experiments described below
were repeated at least in triplicate.
(HNO3) solutions were prepared at ∼10–1 M by dilution of the concentrated acid (Aristar - VWR Chemicals,
69%) and standardized against sodium carbonate (Aldrich, 99.95–100.5%).
Carbonate-free sodium hydroxide (NaOH) solutions were prepared at
∼10–1 M from commercial pellets (Fluka, 99%
min) using freshly boiled ultrapure water and standardized using the
previously standardized acid. The ligand stock solutions were prepared
by direct dissolution of a weighed portion of ligand in water at ∼10–3 M. HNO3 was coadded to increase the solubility
and avoid carbonatation phenomena. Pb2+ solutions were
preprepared from analytical-grade nitrate salt (Pb(NO3)2, Sigma-Aldrich, 99%) and standardized using complexometric
titrations with ethylenediaminetetraacetic acid (EDTA)
with xylenole orange as an indicator. The ionic strength (I) was fixed to 0.15 M using sodium nitrate (NaNO3) as background electrolytes. All of the experiments described below
were repeated at least in triplicate.
4
Trace Element Analysis in Biological Samples
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Trace-analysis-quality nitric acid (69 m/m%, Aristar) and hydrogen peroxide (30 m/m%, Normapur) were applied for sample preparation; both were purchased from VWR International Ltd., Leicestershire, UK. Calibration was carried out with ICP multi- and mono-element standards acquired from Perkin Elmer Inc., Shelton, CT, USA and VWR International Ltd., Leicestershire, UK for quantitative ICP measurement. For determinations, argon gas was used with a 4.6 purity (Messer Hungarogáz Ltd., Budapest, Hungary). Quality controls (QC) were prepared using mussel tissue (ERM-CE278k) and tuna fish (ERM-CE464) originated from the European Commission, Joint Research Centre, Geel, Belgium.
5
Quantification of Serum Selenium Levels
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To determine selenium serum (SeS) concentrations, Bioclinica collected venous blood samples from subjects under fasting conditions and analyzed them with the ICPMS-2030 Inductively Coupled Plasma Mass Spectrometer by Shimadzu (Shimadzu Europa GmbH, Duisburg, Germany). Determinations were made according to the instructions for the use of the laboratory equipment (Laboratory Test Handbook). The ICPMS calibration with an internal standard was employed. A twelve-point calibration standard was generated using a multielement quality control standard, 100 mg/L in 5% nitric acid for 28 elements, ARISTAR® (VWR International, Radnor, PA, USA), Reference 85006.186. The limit of detection (LOD), defined as 3 times the standard deviation (3 s) of the blank, was 0.0231 μg/L, and the limit of quantification (LOQ), defined as 10 s of the blank, was 0.0770 μg/L. Precision was expressed as a percentage of coefficient of variation (CV%), which was 5.6%. ClinChek® Serum Control lyophilized Levels 1 and 2 (RECIPE Chemicals + Instruments GmbH, München, Germany) were used as the reference and control samples. The human-derived multielement serum control materials enabled quality assessment at two concentration levels. Prior to analysis, the control materials were reconstituted according to the manufacturer’s protocol and processed similarly as described for the serum samples.
6
Measuring Soil Metal Bioavailability
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The pH of the extracts (pHKCl) was measured immediately after extraction by potentiometry using a microelectrode (E16M331, Radiometer Analytical®). The total concentrations of dissolved Ca, Cu, Fe, Mn and Zn were determined by ICP-OES (Agilent ®) in a 5-mL aliquot acidified with 2 % HNO3 (Aristar® for trace analysis purity 69 %, VWR Chemicals®). Free Cu activity was measured in non-acidified 5-mL aliquots using a cupric ion-selective electrode (ISE, 9629BNWP, Thermo Scientific Orion®). The ISE was calibrated in Cu solutions buffered with iminodiacetic acid and potassium phthalate with pCu (= -log10 aCu 2+ ) ranging from 5.5 to 13 as described in (Bravin et al. 2009 (link)). The calibration curve (R²=0.98, n=67) showed 85 % slope efficiency compared to the theoretical Nernstian slope (Fig. S1). The concentrations of free Cu 2+ were determined from pCu values and from the Cu 2+ activity coefficient, calculated from the extended Debye-Hückel equation (Ritsema 1993) (link).
7
Microwave Digestion of Soil Samples
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Microwave digestion was carried out via MARS5 (CEM) microwave digestion apparatus using the methodology and variables as follows. Ashed samples were transferred into a clean microwave vessel (HP-500, CEM) and the remaining residue washed into the vessel from the glass beaker using 10 ml of concentrated HNO3 (ARISTAR, 69% w/v, VWR Ltd.). In order to dissolve silicate materials in the sample, 1 ml of hydrofluoric acid (HF) was also added to the vessel (used as supplied, ARISTAR grade, 48% w/v, VWR Ltd.). Twelve soil samples, a blank and a reference material vessel were incorporated into each microwave run. The EPA3052H -HP500 method (#3052) was used to microwave the samples.
After the apparatus had cooled the vessels were removed from the carousel and vented with care. The solutions were transferred into clean Teflon beakers and the vessels rinsed with 1 -2 ml of 2% ARISTAR HNO3 to ensure complete sample transfer. The Teflon beakers were heated on a hot plate until around 1-2 ml of solution remained. The flasks were made up to the 25 ml mark using 2 % (v/v) ARISTAR HNO3. The contents of the flasks were transferred into labelled 30 ml plastic tubes and stored at room temperature for further analysis.
After the apparatus had cooled the vessels were removed from the carousel and vented with care. The solutions were transferred into clean Teflon beakers and the vessels rinsed with 1 -2 ml of 2% ARISTAR HNO3 to ensure complete sample transfer. The Teflon beakers were heated on a hot plate until around 1-2 ml of solution remained. The flasks were made up to the 25 ml mark using 2 % (v/v) ARISTAR HNO3. The contents of the flasks were transferred into labelled 30 ml plastic tubes and stored at room temperature for further analysis.
8
Water Sample Pretreatment and Concentration
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Sub-samples (200 mL) of the stream water samples were acidified with 100 μL c.HNO 3 (Aristar, VWR International Ltd., Leics., UK), filtered through 1 μm membranes (Whatman cellulose nitrate membrane filter paper; VWR International Ltd., Leics., UK) and slowly concentrated tenfold on a hotplate. Reagent blanks were similarly prepared. The surface flow waters did not require pre concentration.
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