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- Andersson, Marit, et al.
(författare)
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A modified standard addition method in X-ray fluorescence spectrometry
- 1993
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 40:5, s. 669-674
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Tidskriftsartikel (refereegranskat)abstract
- A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.
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| 4. |
- Andersson, Marit, et al.
(författare)
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Determination of bromine, chlorine, sulphur and phosphorus in peat by X-ray fluorescence spectrometry combined with single-element and multi-element standard addition
- 1990
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 37:2, s. 185-191
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Tidskriftsartikel (refereegranskat)abstract
- Bromine (20-40 ppm), chlorine (200-500 ppm), sulphur (0.2-3%) and phosphorus (300-1000 ppm) in peat have been determined by X-ray fluorescence spectrometry (XRFS) combined with the standard-addition method. Chlorine, sulphur and phosphorus have also been determined by other methods and agreement between the results is good. Theoretical calculations based on the Sherman equation were made to validate the linearity of the standard-addition curves. A multi-element standard-addition technique has been tested with addition of all elements at the same time. The results for chlorine were high but after correction for the difference in attenuation coefficient between the sample and added compound the results agreed with those from single-element standard addition.
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- Andersson, Marit, et al.
(författare)
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Determination of lead in fly-ash from a garbage incinerator by atomic-absorption and x-ray fluorescence spectrometry
- 1988
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 35:5, s. 337-41
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Tidskriftsartikel (refereegranskat)abstract
- The lead content in fly-ash collected by an electrostatic precipitator has been determined by atomic-absorption spectrometry (AAS) after decomposition by four different leaching/dissolution techniques, and also determined by X-ray fluorescence spectrometry (XRFS) by the standard-addition method. The XRFS data were evaluated by non-linear regression since the standard additions affected the attenuation coefficient of the sample. Good agreement was obtained between the results obtained with AAS and XRFS. It is concluded that lead is quantitatively extracted by hot 1M nitric acid or treatment with hydrofluoric acid/nitric acid. Direct measurement of briquetted samples by XRFS is suggested for rapid monitoring of the lead content in fly-ash from garbage incineration.
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| 6. |
- Andersson, Marit, et al.
(författare)
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Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique
- 1991
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 38:4, s. 385-390
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Tidskriftsartikel (refereegranskat)abstract
- Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.
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| 9. |
- Hashemi, Payman, et al.
(författare)
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Agarose film coated glass slides for preparation of pH optical sensors
- 2007
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 121:2, s. 396-400
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Tidskriftsartikel (refereegranskat)abstract
- A method for preparation of optical sensors was developed by agarose film coating on aminosilanated glass slides. An optical pH sensor was accordingly prepared by epoxy activation of the agarose film, followed by chemical immobilization of Neutral Red dye. In an optimized coupling pH of 12 and a dye concentration of 10(-2) mol L-1 a pH sensor for a pH range of 2-8.5 was obtained. A theoretical equation was derived using the extended Henderson-Hasselbalch equation that reproduced the measured data well. The sensor was mounted in a flow cell and successfully applied for on-line pH measurements. The sensor responded rapidly to the pH changes with a response time of less than 2 min and reproducibility better than 0.40% (R.S.D.). In comparison to a stand-alone agarose membrane, the agarose coated glass slide showed better physical properties and easier handling and application but slightly slower response times. No evidence of leaching of the dye or any signal drift was observed.
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- Heverin, Maura, et al.
(författare)
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On the regulatory importance of 27-hydroxycholesterol in mouse liver
- 2017
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Ingår i: Journal of Steroid Biochemistry and Molecular Biology. - : Elsevier. - 0960-0760 .- 1879-1220. ; 169, s. 10-21
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Forskningsöversikt (refereegranskat)abstract
- 27-Hydroxycholesterol (27OH) is a strong suppressor of cholesterol synthesis and a weak activator of LXR in vitro. The regulatory importance of 27OH in vivo is controversial. Here we utilized male mice with increased levels of 27OH either due to increased production (CYP27A1 transgenic mice) or reduced metabolism (Cyp7b1-/- mice). We also used mice lacking 27OH due to a knockout of Cyp27a1. The latter mice were treated with cholic acid to compensate for reduced bile acid synthesis. The effects of the different levels of 27OH on Srebp- and other LXR-regulated genes in the liver were investigated. In the liver of CYP27tg mice we found a modest increase of the mRNA levels corresponding to the LXR target genes Cyp7b1 and Abca1. A number of other LXR-regulated genes were not affected. The effect on Abca1 mRNA was not seen in the liver of Cyp7b1-/- mice. There were little or no effects on cholesterol synthesis. In the liver of the Cyp27-/- mice treated with 0.025% cholic acid there was no significant effect of the knockout on the LXR target genes. In a previous work triple-knockout mice deficient in the biosynthesis of 24S-hydroxycholesterol, 25-hydroxycholesterol and 27OH were shown to have impaired response to dietary cholesterol, suggesting side-chain oxidized oxysterols to be mediators in cholesterol-induced effects on LXR target genes at a transcriptional level (Chen W. et al., Cell Metab. 5 (2007) 73-79). The hydroxylated oxysterol responsible for the effect was not defined. We show here that treatment of wildtype mice with dietary cholesterol under the same conditions as in the above study induced the LXR target genes Lpl, Abcg8 and Srebp1c in wild type mice but failed to activate the same genes in mice lacking 27-hydroxycholesterol due to a knockout of Cyp27. We failed to demonstrate the above effects at the protein level (Abcg8) or at the activity level (Lpl). The results suggest that 27OH is not an important regulator of Srebp- or LXR regulated genes under basal conditions in mouse liver. On the other hand 27OH appears to mediate cholesterol-induced effects on some LXR target genes at a transcriptional level under some in vivo conditions.
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