Atomic fluorescence spectroscopy

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Determ,ination of Lead and Cadmium in Potable Waters by Atom-trapping Atomic-absorption Spectrophotometry

A simple method for the determination of lead and cadmium in potable waters using an atom-trapping technique is described. The method uses two water-cooled silica tubes mounted in an air -acetylene flame to trap the determinand atoms. Criteria of detection of 2.0 and 0.25 pg 1-1 are observed for lead and cadmium, respectively. Basic performance characteristics are also given for arsenic, copper, selenium and silver. Keywords: Lead and cadmium determination; atom trapping; water-cooled silica tube; atomic-absorption spectrophotometry; potable water The maximum admissible concentrations of lead and cadmium in potable waters are 50 and 5 pg 1-1, respective1y.l For monitoring a determinand at a given maximum admissible concentration, the laboratory aims to develop a method with a criterion of detection2 equal to or below one tenth of the maximum admissible concentration. The purpose of this study was to develop a potable water analysis technique with a criterion of detection better than 5 pg 1-1 for lead and 0.5 pg 1-1 for cadmium using a simply modified flame atomicabsorption spectrophotometer. The technique was to be used as a back-up for the routinely employed electrothermal atomisation technique. The sensitivity of conventional flame atomic-absorption spectrophotometry (AAS) is limited by the fact that the efficiency of a typical nebuliser -spray chamber system is only ca. 5%. Thus a nebuliser with an uptake of 5 ml min-1 supplying an air -acetylene flame with a combined air and acetylene flow-rate of 12 1 min-1 will result in an over-all sample dilution (ignoring air entrainment) of 12 00015 X 0.05 = 48000 times. Lau et a1.3 minimised the effect of this large sample dilution by placing a water-cooled silica tube in an air -acetylene flame. The sample was then nebulised for a pre-set time (typically 1-10 min) with the result that determinand (either as atoms or their precursors) condensed on the cooled tube. When the collection was completed, the water was rapidly ejected from the silica tube. The tube then rapidly heated up and released the collected determinand into the light beam above the tube. The transient signal observed was significantly greater than that observed using conventional flame AAS for a number of relatively volatile elements. Ure and coworkers4-10 have extended the use of the technique to a number of relatively volatile elements (Ag, As, Au, Bi, Cd, Cu, Mn, Pb, Sb, Se, T1 and Zn) with sensitivity increases for a 2-min collection time of between 8 and 40 times over conventional flame AAS. Coating the silica tube with aluminium oxide and/or iron(II1) oxide was found to minimise inter-element effects. In addition , these coatings were found to prevent direct interaction of the alkali and alkaline earth metals with the silica surface of the tube and at the same time greatly increased the effective surface area for the trapping of both determinand and concomitant species. This paper outlines the development of a method for the determination of cadmium and lead in potable waters using a dual silica tube mounted in an air -acetylene flame

Prenatal factors contribute to the emergence of kwoshiorkor or marasmus in severe undernutrition: evidence for the predictive adaptation model

Severe acute malnutrition in childhood manifests as oedematous (kwashiorkor, marasmic kwashiorkor) and non-oedematous (marasmus) syndromes with very different prognoses. Kwashiorkor differs from marasmus in the patterns of protein, amino acid and lipid metabolism when patients are acutely ill as well as after rehabilitation to ideal weight for height. Metabolic patterns among marasmic patients define them as metabolically thrifty, while kwashiorkor patients function as metabolically profligate. Such differences might underlie syndromic presentation and prognosis. However, no fundamental explanation exists for these differences in metabolism, nor clinical pictures, given similar exposures to undernutrition. We hypothesized that different developmental trajectories underlie these clinical-metabolic phenotypes: if so this would be strong evidence in support of predictive adaptation model of developmental plasticity

Alpha-1 antitrypsin protein and gene therapies decrease autoimmunity and delay arthritis development in mouse model

<p>Abstract</p> <p>Background</p> <p>Alpha-1 antitrypsin (AAT) is a multi-functional protein that has anti-inflammatory and tissue protective properties. We previously reported that human AAT (hAAT) gene therapy prevented autoimmune diabetes in non-obese diabetic (NOD) mice and suppressed arthritis development in combination with doxycycline in mice. In the present study we investigated the feasibility of hAAT monotherapy for the treatment of chronic arthritis in collagen-induced arthritis (CIA), a mouse model of rheumatoid arthritis (RA).</p> <p>Methods</p> <p>DBA/1 mice were immunized with bovine type II collagen (bCII) to induce arthritis. These mice were pretreated either with hAAT protein or with recombinant adeno-associated virus vector expressing hAAT (rAAV-hAAT). Control groups received saline injections. Arthritis development was evaluated by prevalence of arthritis and arthritic index. Serum levels of B-cell activating factor of the TNF-α family (BAFF), antibodies against both bovine (bCII) and mouse collagen II (mCII) were tested by ELISA.</p> <p>Results</p> <p>Human AAT protein therapy as well as recombinant adeno-associated virus (rAAV8)-mediated hAAT gene therapy significantly delayed onset and ameliorated disease development of arthritis in CIA mouse model. Importantly, hAAT therapies significantly reduced serum levels of BAFF and autoantibodies against bCII and mCII, suggesting that the effects are mediated via B-cells, at least partially.</p> <p>Conclusion</p> <p>These results present a new drug for arthritis therapy. Human AAT protein and gene therapies are able to ameliorate and delay arthritis development and reduce autoimmunity, indicating promising potential of these therapies as a new treatment strategy for RA.</p

Limitations of fasting indices in the measurement of insulin sensitivity in Afro-Caribbean adults

In young Afro-Caribbean adults, HOMA-IR compared poorly with other measures of insulin sensitivity. It remains important to determine whether similar findings occur in a more insulin resistant population. However, HOMA-IR correlated with clinical measures of insulin sensitivity (i.e. adiposity), so it may still be useful in epidemiological studies

Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions

We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56–poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA–PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20–100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56–poly(benzyl methacrylate)300 [PGMA56–PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56–PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39–poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39–PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral attenuation

'Country life'? Rurality, folk music and 'Show of Hands'

This paper examines the contribution of folk music to understanding the dynamic, fluid and multi-experiential nature of the countryside. Drawing from literature on the geographies of music, it examines the work of 'Show of Hands', a contemporary folk band from Devon in England. Three areas are studied. First, the paper examines the musical style of Show of Hands in order to explore how hybridised, yet distinctive, styles of music emerge in particular places. Second, it demonstrates how Show of Hands' hybrid musical style has become closely associated with the Southwest of England. Finally, within these spatial and hybrid contexts, attention is given to the ways in which their music represents the 'everyday lives of the rural'. Taken together these themes assess the relevance of music in the understanding of rurality as hybrid space. © 2008 Elsevier Ltd. All rights reserved

Survival time and differences between dementia with Lewy bodies and Alzheimer's disease following diagnosis: A meta-analysis of longitudinal studies.

OBJECTIVE: To synthesize the evidence across longitudinal studies comparing survival in dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). METHODS: We conducted a systematic review and meta-analysis of studies comparing survival in clinically diagnosed DLB to AD. Longitudinal cohort studies were identified through a systematic search of major electronic databases from inception to May 2018. A random effects meta-analysis was performed to calculate survival time and relative risk of death. RESULTS: Overall, 11 studies were identified including 22,952 patients with dementia: 2029 with DLB (mean diagnosis age 76.3; 47% female) compared with 20,923 with AD (mean diagnosis age 77.2; 65.1% female). Average survival time in DLB from diagnosis was 4.11 years (SD ± 4.10) and in AD 5.66 (SD ± 5.32) years, equating to a 1.60 (95% CI: -2.44 to -0.77) years shorter survival in DLB (p < 0.01). Relative risk of death was increased by 1.35 (95%CI: 1.17-1.55) in DLB compared to AD (p < 0.01). Differences in survival were not explained by follow-up time, age at diagnosis, gender, or cognitive score. CONCLUSIONS: There is consistent evidence for higher and earlier mortality in DLB compared to AD. This is important for all stakeholders and underlines the importance of expanding research into DLB.NIH