Orpington, United Kingdom
Orpington, United Kingdom

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Brombach C.-C.,University of Aberdeen | Manorut P.,University of Aberdeen | Kolambage-Dona P.P.P.,PS Analytical | Ezzeldin M.F.,University of Aberdeen | And 5 more authors.
Food Chemistry | Year: 2017

Rice is known to accumulate methylmercury (MeHg) in the rice grains. MeHg as a neurotoxin impacts on the human central nervous systems and especially on the developing brain. In this exploratory study, 87 commercial rice products sold in Europe, including nine baby-rice products, were analyzed for total Hg and MeHg content. MeHg concentration in all rice products investigated range from 0.11 to 6.45 μg kg−1 with an average value of 1.91 ± 1.07 μg kg−1 and baby-rice is not significantly different from other rice products. Total Hg ranges from 0.53 to 11.1 μg kg−1 with an average of 3.04 ± 2.07 μg kg−1. MeHg concentrations in all rice products studied in this work would not exceed the provisional tolerable weekly intake (PTWI). 30% of all commercial market rice products exceeded 10% of the PTWI calculated for toddlers or 13% of products for adults with rice based diet. © 2016 Elsevier Ltd


Brown R.J.C.,National Physical Laboratory United Kingdom | Pirrone N.,CNR Institute of Atmospheric Pollution Research | van Hoek C.,Dutch Standardization Institute | Horvat M.,Jozef Stefan Institute | And 5 more authors.
Accreditation and Quality Assurance | Year: 2010

A standard method for the measurement of mercury in deposition is currently being finalised by Working Group 25 of the European Committee for Standardisation's Technical Committee 264 'Air Quality', in response to the requirements of the European Union's Fourth Air Quality Daughter Directive. This paper reports the results of a field measurement programme which was undertaken to assess the uncertainty of the proposed standard method, define its working range and determine its compliance with the required data quality objectives of the Fourth Air Quality Daughter Directive. © 2010 Springer-Verlag.


Brombach C.-C.,University of Aberdeen | Chen B.,PS Analytical | Corns W.T.,PS Analytical | Feldmann J.,University of Aberdeen | Krupp E.M.,University of Aberdeen
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2015

Ultra-traces of methylmercury at the sub-ppt level can be magnified in the foodweb and is of concern. In environmental monitoring a routine robust analytical method is needed to determine methylmercury in water. The development of an analytical method for ultra-trace speciation analysis of methylmercury (MeHg) in water samples is described. The approach is based on HPLC-CV-AFS with on-line preconcentration of water samples up to 200 mL, resulting in a detection limit of 40 pg/L (ppq) for MeHg, expressed as Hg. The unit consists of an optimized preconcentration column filled with a sulfur-based sorption material, on which mercury species are preconcentrated and subsequently eluted, separated and detected via HPLC-CV-AFS (high performance liquid chromatography-cold vapor atomic fluorescence spectrometry). During the method development a type of adsorbate material, the pH dependence, the sample load rate and the carry-over were investigated using breakthrough experiments. The method shows broad pH stability in the range of pH 0 to 7, without the need for buffer addition and shows limited matrix effects so that MeHg is quantitatively recovered from sewage, river and seawater directly in the acidified samples without sample preparation. © 2014 Elsevier B.V. All rights reserved.


PubMed | Claro, PS Analytical, University of Sao Paulo and Vrije Universiteit Brussel
Type: | Journal: Talanta | Year: 2014

In this work, a device based on diffusive gradients in thin films (DGT) was evaluated for the determination of Hg(II) in river water. The DGT device was assembled with a cellulose phosphate ion exchange membrane (P81 Whatman) as a binding phase and agarose gel 1.5% (m/v) as a diffusive layer. Laboratory deployments showed that the binding of Hg(2+) ([Hg(DGT)]/[Hg(solution)]) by P81 membrane was more effective (97%) than the Chelex 100 resin (80%).The effect of ionic strength, pH and potential interfering ions on Hg binding with DGTs was investigated. The results showed no significant effect on the binding of Hg(II) at pH range from 3.5 to 8.5 and at an ionic strength range from 0.0005 to 0.1 mol L(-1). Uptakes of 50 g L(-1) Hg(II) by P81 membrane were not affected by Fe, Mn, Zn, Cu, Ca and Mg at the concentration range of 200-1800 g L(-1). Finally, the DGT device using the P81 as the binding layer was applied for in situ measurements of Hg in river water. For in situ measurements, the labile Hg concentration (from <2 to 13 ng L(-1)) was lower than 10% of the dissolved fraction (from 155 to 446 ng L(-1)).


PubMed | University of Dammam, PS Analytical and University of Aberdeen
Type: | Journal: Food chemistry | Year: 2016

Rice is known to accumulate methylmercury (MeHg) in the rice grains. MeHg as a neurotoxin impacts on the human central nervous systems and especially on the developing brain. In this exploratory study, 87 commercial rice products sold in Europe, including nine baby-rice products, were analyzed for total Hg and MeHg content. MeHg concentration in all rice products investigated range from 0.11 to 6.45gkg(-1) with an average value of 1.911.07gkg(-1) and baby-rice is not significantly different from other rice products. Total Hg ranges from 0.53 to 11.1gkg(-1) with an average of 3.042.07gkg(-1). MeHg concentrations in all rice products studied in this work would not exceed the provisional tolerable weekly intake (PTWI). 30% of all commercial market rice products exceeded 10% of the PTWI calculated for toddlers or 13% of products for adults with rice based diet.


Lummas S.,University of Lincoln | Ruiz-Jimenez J.,University of Cordoba, Spain | de Castro M.D.L.,University of Cordoba, Spain | Colston B.,University of Lincoln | And 3 more authors.
Analytical Letters | Year: 2011

A dynamic ultrasound-assisted extraction method using Atomic Absorption and Atomic Fluorescence spectrometers as detectors was developed to analyze mercury, arsenic, and barium from herbarium mount paper originating from the herbarium collection of the National Museum of Wales. The variables influencing extraction were optimized by a multivariate approach. The optimal conditions were found to be 1% HNO 3 extractant solution used at a flow rate of 1mL min -1. The duty cycle and amplitude of the ultrasonic probe was found to be 50% in both cases with an ultrasound power of 400 W. The optimal distance between the probe and the top face of the extraction chamber was found to be 0 cm. Under these conditions the time required for complete extraction of the three analytes was 25 min. Cold vapor and hydride generation coupled to atomic fluorescence spectrometry was utilized to determine mercury and arsenic, respectively. The chemical and instrumental conditions were optimized to provide detection limits of 0.01 ng g -1 and 1.25 ng g -1 for mercury and arsenic, respectively. Barium was determined by graphite-furnace atomic absorption spectrometry, with a detection limit of 25 ng g -1. By using 0.5 g of sample, the concentrations of the target analytes varied for the different types of paper and ranged between 0.4-2.55 μg g -1 for Ba, 0.035-10.47 μg g -1 for As, and 0.0046-2.37 μg g -1 for Hg. © Taylor & Francis Group, LLC.


Brown A.S.,National Physical Laboratory United Kingdom | Brown R.J.C.,National Physical Laboratory United Kingdom | Dexter M.A.,PS Analytical | Corns W.T.,PS Analytical | Stockwell P.B.,PS Analytical
Analytical Methods | Year: 2010

The measurement of mercury vapour in ambient air is required in order to ensure the quality life of the general public. New legislation introduced recently by the European Commission has mandated that sampling and analysis be performed in situ at monitoring sites, and that mass concentration of mercury vapour in ambient air is determined within a maximum uncertainty. This paper presents a novel and innovative automatic method for such in situ measurements of mercury vapour in ambient air using atomic fluorescence spectrometry, where calibration, sampling and analysis are all performed fully automatically without manual intervention. A robust measurement equation and uncertainty budget for this automatic method is developed, and the overall relative expanded uncertainty for an exemplar measurement has been found to be 21%, well below the target expanded uncertainty of 50% set by the European Commission for these measurements. The uncertainty of a semi-automatic method (automatic sampling and analysis, but manual calibration) has also been assessed, and compared with the uncertainty of the novel automatic method, and the uncertainty of a manual (remote sampling and manual calibration and analysis) method presented in a previous study. © 2010 The Royal Society of Chemistry.


Stockwell P.B.,P.S. Analytical
American Laboratory | Year: 2012

Atomic fluorescence spectrometry (AFS) is used to determine mercury in its various forms at very low levels in the environment, especially in difficult matrices such as petrochemicals. It is a spectroscopic process that is based on the absorption of radiation of a certain wavelength by an atomic vapor and subsequent radiational deactivation of the excited atoms toward the detection device. The basic layout of an AFS instrument is similar to atomic absorption spectrometry (AAS), except that the light source and detectors are placed at right angles. The system involves the coupling of the mercury analyzer with a UV cracker and associated cooling modules The sample is mixed with an oxidant stream of acidified bromide/bromate, which then passes through the UV digestion system. Samples can be analyzed without any sample pretreatment. Apart from analytical techniques, reliable data should be provided, allowing process operators to control the processes and avoid costly plant shutdowns.


Chen B.,PS Analytical | Corns W.T.,PS Analytical | Stockwell P.B.,PS Analytical | Huang J.-H.,University of Basel
Analytical Methods | Year: 2014

Two novel methods based on hydride generation atomic fluorescence spectrometry for the accurate screening of total and inorganic arsenic (As) in rice grain digests in 5 and 2 minutes, respectively, are proposed here. Total As determination was achieved using online UV photolysis aided by alkaline potassium persulphate oxidation, which converted all organic As to arsenate and thus allowed quantitative hydride generation. Determination of inorganic As in rice grains was accomplished by selective hydride generation at high acidity (4.8 M HCl), which allowed ∼50 times higher efficiency for hydride generation of arsenite than the prevalent form of organic As in rice, namely dimethylarsonic acid (DMA), after pre-reduction of all inorganic As using potassium iodide/ascorbic acid. The accuracy of the method was verified by (1) excellent agreement with the certified value of total As and the literature values of inorganic As in NIST SRM 1658a; (2) complete recovery of total As in NIST SRM 1568a spiked with additional 2 ng As g-1 of DMA; (3) excellent agreement of total and inorganic As values in 80 samples of different types, origins and treatments (standing for different matrices) compared to ICP-MS and HPLC-ICP-MS measurements; (4) ∼100% recovery of inorganic As in ERM-BC-211 and a round grain rice sample even spiked with DMA up to 200 ng As g-1. Additionally, the low data dispersion was indicated by the low relative standard deviation (∼4.3%) in the day-to-day precision for quantifying inorganic As in NIST SRM 1568a on 7 different days. © the Partner Organisations 2014.


Brown R.J.C.,National Physical Laboratory United Kingdom | Kumar Y.,National Physical Laboratory United Kingdom | Brown A.S.,National Physical Laboratory United Kingdom | Dexter M.A.,PS Analytical | Corns W.T.,PS Analytical
Journal of Environmental Monitoring | Year: 2012

The manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air have been compared in a field trial for the first time. The comparison results have shown that whilst the expected random scatter is present, there was no significant systematic bias between the two methods, whose operational differences have also been outlined and analysed in this work. Furthermore it has been observed that because variation in instrument sensitivity is largely random in nature there is little effect on the results of the comparison if the period between instrument calibrations is altered. When the manual and semi-automatic methods are compared according to guidelines produced by the European Commission the results presented here, taken together with other supporting evidence, strongly suggest that the two methods are equivalent. © 2012 The Royal Society of Chemistry.

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