| 1. |
- Khayyami, Masoud, et al.
(författare)
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Flow-injection determination of trace hydrogen peroxide or glucose utilizing an amperometric biosensor based on glucose oxidase bound to a reticulated vitreous carbon electrode
- 1996
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140. ; 43:6, s. 957-962
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Tidskriftsartikel (refereegranskat)abstract
- An electron transfer mediator, 8-dimethylamino-2,3-benzophenoxazine (Meldola Blue), dissolved in the carrier solution in a flow-injection system, was found to reduce the oxidation potential for hydrogen peroxide from 600-1200 mV without mediator to - 100 mV vs. Ag/AgCl with the mediator present. The very low background current of reticulated vitreous carbon (RVC) at this potential makes it possible to detect very low levels of hydrogen peroxide or glucose. Glucose oxidase was covalently coupled with carbodiimide to RVC, and the RVC was formed into a column inserted in a flow-injection system. The calibration curve was linear from 30 nM to 10 μM glucose with 5 μM mediator. At higher mediator concentrations, the linear range was extended to 1000 μM, but with a much higher background current. The sample throughput was about 60 h-1. The current response decreased to 50% of the original response after 20 days. The coulometric yield was high because the sample was pumped through the pores of the RVC. It was 16% and 55% at a flow rate of 1 ml min -1 at mediator concentrations of 5 and 50 μM respectively.
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| 2. |
- Andersson, Helene, et al.
(författare)
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Self-assembled and self-sorted array of chemically active beads for analytical and biochemical screening
- 2002
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 56:2, s. 301-308
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Tidskriftsartikel (refereegranskat)abstract
- A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 mum. Besides silicon, quartz and polyethylene have also been used as substrates.
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| 3. |
- 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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| 5. |
- 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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| 7. |
- Ericzon, Christina, et al.
(författare)
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Interference from iodide in the determination of trace level selenium
- 1990
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 37:7, s. 725-730
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Tidskriftsartikel (refereegranskat)abstract
- The rate of the reaction between iodide and selenium(IV) at trace levels to form selenium and iodine has been determined in 1–6M hydrochloric acid. The reaction rate increases rapidly with acidity. When hydrochloric acid is added to reduce selenate to selenite prior to the determination of total selenium, some selenium may be lost by reduction to the element if iodide is present. A table of half-lives of the selenite—iodide reaction under various conditions is presented. A method for removal of iodide is suggested.
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| 8. |
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| 9. |
- Rodushkin, Ilya, et al.
(författare)
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Multielement analysis of coal by ICP techniques using solution nebulization and laser ablation
- 2000
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 51:4, s. 743-759
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Tidskriftsartikel (refereegranskat)abstract
- The combination of inductively coupled plasma atomic emission spectrometry and high resolution inductively coupled plasma mass spectrometry for the determination of 70 elements in coal were studied. Four microwave-assisted digestion procedures with different dissolution mixtures (nitric and hydrofluoric acids, aqua regia and hydrogen peroxide), lithium metaborate fusion with and without previous sample ashing as well as direct sampling by laser ablation (LA) have been tested. Examples of spectral interferences are given and different correction procedures are discussed. Detection limits in the low ng g-1 range were obtained for most of the elements investigated by using high-purity reagents and by taking special care to prevent sample contamination during preparation. The precision was assessed from replicate analysis (including sample preparation) of coal samples and was found to be, as average values far all elements, 4-5% RSD and 10-15% RSD for procedures including sample digestion and LA sampling, respectively. The accuracy of the overall analytical procedures was estimated by analysis of certified reference materials and of a coal sample obtained from the Interlab Trace round robin test. Among the dissolution mixtures tested, the combination of nitric and hydrofluoric acids with hydrogen peroxide provide the best agreement with certified, recommended, literature-compiled or consensus values, though fusion is necessary to obtain quantitative recoveries for Si, Cr, Hf, W, Zr, Y. In general, results obtained by LA fall within ±20% of those obtained after digestion.
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| 10. |
- Tóth, I., et al.
(författare)
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Application of a sulphide-selective electrode in the absence of a pH-buffer
- 1988
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 35:10, s. 783-788
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Tidskriftsartikel (refereegranskat)abstract
- Calibration of a sulphide electrode in the pH-range 9-12 has been studied as an e.m.f. vs. (pH - p[HS-]) function by measuring e.m.f. and pH in parallel. Calibration can also be done in this pH range by using a differential amplifier with a three-electrode measuring cell (glass, sulphide-selective and reference electrodes). The effects of an antioxidant (ascorbic acid) and a complexing agent (DCTA) on the calibration of the glass-sulphide electrode cell at pH < 5 were studied. The applicability of this end-point indicator cell has been demonstrated for titrations of Ag+, Pb2+ and Bi3+ with Na2S.
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