Computational Modelling of the Hydride Generation Reaction in a Tubular Reactor and Atomization in a Quartz Cell Atomizer
- 1 Department of Chemical and Biological Engineering, The University of Sheffield, Sheffield, UK
- 2 Department of Chemical and Biological Engineering, The University of Sheffield, Sheffield, UK.
Abstract
In this study, we present a model whereby the centre of the atomization channel is shown to be the optimal location for the spectrometric data acquisition in a quartz cell atomizer. The study aims to explore the hydride generation technique which is normally coupled with efficient thermal source to apply determination of heavy metals in water samples via spectrometric analysis. The arsenic hydride generation process and the atomization of the generated hydride in a quartz cell atomizer were studied analytically as model case studies. The hydride generation (HG) process was analyzed by adopting two hypotheses, the nascent hydrogen and formation of intermediate hydroboron species, where the results based on the second hypothesis are found to be more realistic for design purposes. Moreover, the release of the generated hydride from the liquid phase and their transport to the gas phase is simulated in a helical tubular section, in which the actual tubular section length required for separation is deduced. The analytical results have been verified experimentally by measuring the signal intensity for the free arsenic atoms against several reaction tube lengths, in which increasing the tubular section length from 12 cm to 100 cm results in signal amelioration by no more than 6.6%. Furthermore, the atomization of the hydride and the distribution of the generated free atoms are deduced in two configurations of tubular quartz atomizers. The results obtained from both studied cases illustrate that a high concentration of the free analyte atoms is generated in the first part of the atomization channel, saturates to a maximum in a position at the atomizer centre, and dissipates at the inside wall of the tubular atomizer before reaching the atomizer outlet edge, which is found to be in total agreement with the current understanding of atomization mechanism in tubular atomizer and emphasizes the fact that the centre of the quartz cell atomizer is the best location for the spectrometric data acquisition.
- J. Dedina and D. Tsalev, “Hydride Generation Atomic Absorption Spectrometry,” John Wiley & Sons Ltd., Chichester, 1995.
- Y. Feng, J. Lam and R. Sturgeon, “Expanding the Scope of Chemical Vapor Generation for Noble and Transition Metals,” Analyst, Vol. 126, No. 11, 2001, pp. 1833-1837. doi:10.1039/b107494f
- P. Pohl and B. Prusisz, “Chemical Vapor Generation of Noble Metals for Analytical Spectrometry,” Analytical and Bioanalytical Chemistry, Vol. 388, No. 4, 2007, pp. 753-762. doi:10.1007/s00216-006-0678-9
- J. Dedina, “Optimization of Hydride Generation Methods for AAS,” Fresenius’ Journal of Analytical Chemistry, Vol. 323, 1986, pp. 771-782.
- X. Wang, “A Mathematical Model for Continuous Hydride Generation with Inductively Coupled Plasma Spectrometry Analysis: I. Hydride Transfer,” Spectrochimica Acta Part B: Atomic Spectroscopy, Vol. 41, No. 9, pp. 967-977. doi:10.1016/0584-8547(86)80100-8
- X. Wang and R. Barnes, “A Mathematical Model for Continuous Hydride Generation with Inductively Coupled Plasma Spectrometry: II. pH Dependence of Hydride Forming Elements,” Spectrochimica Acta Part B: Atomic Spectroscopy, Vol. 42, No. 1-2, 1987, pp. 139-156. doi:10.1016/0584-8547(87)80057-5
- A. D’ulivo, Z. Mester and R. Sturgeon, “The Mechanism of Formation of Volatile Hydrides by Tetrahydroborate (III) Derivatization: A Mass Spectrometric Study Performed with Deuterium Labeled Reagents,” Spectrochimica Acta Part B: Atomic Spectroscopy, Vol. 60, No. 4, 2005, pp. 423-438. doi:10.1016/j.sab.2005.03.015
- A. D’ulivo, M. Onor and E. Pitzalis, “Role of Hydroboron Intermediates in the Mechanism of Chemical Vapor Generation in Strongly Acidic Media,” Analytical Chemistry, Vol. 76, No. 21, 2004, pp. 6342-6352. doi:10.1021/ac040078o
- A. D’ulivo, J. Dědina, Z. Mester, R. sturgeon, Q. Wang and B. Welz, “Mechanisms of Chemical Generation of Volatile Hydrides for Trace Element Determination (IU-PAC Technical Report),” Pure and Applied Chemistry, Vol. 83, No. 6, 2011, pp. 1283-1340. doi:10.1351/PAC-REP-09-10-03
- S. Van Wagenen, D. Carter, A. Ragheb and Q. Fernando, “Kinetic Control of Peak Shapes in Atomic Absorption Arsenic Determinations by Arsine Generation,” Analytical chemistry, Vol. 59, No. 6, 1987, pp. 891-896. doi:10.1021/ac00133a022
- B. Welz and M. Melcher, “Investigations on Atomisation Mechanisms of Volatile Hydride-Forming Elements in a Heated Quartz Cell. Part 1. Gas-Phase and Surface Effects; Decomposition and Atomisation of Arsine,” Analyst, Vol. 108, No. 1283, 1983, pp. 213-224. doi:10.1039/an9830800213