Characterization and vapour phase interference studies of a flame heated holed quartz T-tube as atomization cell for hydride generation atomic absorption spectrometry† Patricia Grinberg,*a Iracema Takaseb and Reinaldo Calixto de Camposa aDepartment of Chemistry, Pontifý� cia Universidade Cato�lico do Rio de Janeiro, Rio de Janeiro, Brazil. E-mail: grinberg@rdc.puc-rio.br, rccampos@rdc.puc-rio.br bDepartment of Analytical Chemistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.E-mail: takaseir@iq.ufrj.br Received 23rd November 1998, Accepted 24th March 1999 Characterization and mutual hydride forming element interference studies of a flame heated holed quartz T-tube as atomization cell for HGAAS were performed. Characteristic concentrations, limits of detection and linear ranges were determined for As, Bi, Sb and Se. Also, the mutual interferences of these elements were investigated. Extended non-interferent ranges were observed in most of the studied cases and such improvement was obtained at no great expense with regard to sensitivity and detection limits. Mutual hydride forming element interference is a well known Procedure phenomenon in hydride generation atomic absorption spec- All plastic and glassware were immersed in 10% HNO3 for at trometry (HGAAS).1–10 According to the current literaleast 24 h and thoroughly rinsed with Milli-Q water before ture,11,12 the atomization mechanism in HGAAS involves a use.The reaction flask was washed with Milli-Q water between H radical mediated process and the competition for this radical successive uses to avoid memory eVects and contamination.explains these interferences. Indeed, it has been verified that, The T-tubes were pre-heated for at least 10 min before the in environments richer in H radicals, larger sensitivities may first measurement and the reagent blank value was tested be reached and mutual hydride forming element interferences periodically and always subtracted from the measured analyte are minimized.5,13 The aim of the present work is to investigate signals.All measurements were performed using 10 mL of 1, a flame heated holed quartz T-tube as an alternative atomiz- 5 and 10% v/v HCl in the reaction flask, in peak height, and ation cell for HGAAS, with special regard to mutual hydride all data given in this work are the average of five independent forming element interferences. determinations.Experimental Results Instrumentation Sensitivities, instrumental detection limits and linear ranges A Perkin-Elmer Model (Norwalk, CT, USA) MHS-10 hydride Table 2 compares the figures of merit for both tested atomizers generation batch system was used. Nitrogen was used as purge using a stoichiometric flame. Sensitivities (c0, characteristic and carrier gas. The generated hydrides were atomized in two types of flame heated quartz cell, diVering from each other in the presence or absence of holes (Fig. 1). All measurements were performed with a Varian Techtron (Palo Alto, CA, USA) Model AA5 atomic absorption spectrometer using an air– acetylene flame. Perkin-Elmer hollow cathode lamps (HCL) were used for all elements. The operating parameters and the instrumental settings were adjusted according to the manufacturers’ recommendations and some of them are listed in Table 1. No background correction was used. Reagents and Solutions Milli-Q water (Millipore-Waters, Milford, MA, USA) was used throughout and all chemicals were of analytical-reagent grade; 1.5% m/v NaBH4 (Vetec) was freshly prepared by od 2 id 10, od 12 12 51 96 18 18 17 18 dissolving the salt in 0.5% m/v NaOH (Vetec) and this solution Fig. 1 Holed quartz T-tube. All measurements are in millimetres. was always filtered before use. Analytical solutions, as well as Table 1 Operating parameters those containing interferents, were prepared from convenient dilutions and spikings of Tritisol concentrates (1000 mg L-1, Parameter As Bi Sb Se Merck, Elmsford, NY, USA) to the reaction flask. Wavelength/nm 193.7 223.1 217.6 196 Slit/nm 0.3 0.05 0.1 0.3 †Presented at the Fifth Rio Symposium on Atomic Spectrometry, HCL current/mA 7 8 10 10 Cancu� n, Mexico, October 4–10, 1998.J. Anal. At. Spectrom., 1999, 14, 827–830 827Table 2 Sensitivities (c0), detection limits and linear ranges (all in mg L-1) in the determination of As, Bi, Sb and Se in 10% v/v HCl by HGAAS using a conventional atomizer and the proposed atomizer Quartz T-tube (QTA) Holed quartz T-tube (HQTA) Characteristic Detection Linear range Characteristic Detection Linear range Element concentration limit (up to) concentration limit (up to) As 0.11 0.06 15 0.47 0.23 40 Bi 0.28 0.15 30 0.39 0.20 60 Sb 0.31 0.17 35 0.36 0.18 35 Se 0.17 0.09 30 0.25 0.16 40 Fig. 2 Interferences of Bi (+), Sb (#), Se (>) and Te (%) on the As (5 mg L-1) signal in 10 mL of 10% HCl: (a) conventional quartz T-tube; (b) holed quartz T-tube.Fig. 3 Interferences of As ($), Sb (#), Se (>) and Te (%) on the Bi (5 mg L-1) signal in 10 mL of 10% HCl: (a) conventional quartz T-tube; (b) holed quartz T-tube. concentration) and linear ranges (10% deviation from the No significant change in these analytical figures was observed in relation to the other HCl concentrations (1 and 5%) studied. linear projection) were taken from aqueous analytical curves. The instrumental detection limits were calculated from LOD= Table 2 shows that, for both atomizers, comparable characteristic concentrations and detection limits were 3ss/m, where ss is the estimated standard deviation of ten blank measurements and m is the slope of the analytical curve.observed for all tested elements, except As. Concerning the 828 J. Anal. At. Spectrom., 1999, 14, 827–830Fig. 4 Interferences of As ($), Bi (+), Se (>) and Te (%) on the Sb (20 mg L-1) signal in 10 mL of 10% HCl: (a) conventional quartz T-tube; (b) holed quartz T-tube.Fig. 5 Interferences of As ($), Bi (+), Sb (#) and Te (%) on the Se (20 mg L-1) signal in 10 mL of 10% HCl: (a) conventional quartz T-tube; (b) holed quartz T-tube. Table 3 Tolerance limits (±10%) for the studied interferent elements using a conventional atomizer and the proposed atomizer Analyte As (5 mg L-1) Bi(5mg L-1) Sb(20mg L-1) Se(20mg L-1) Interferent QTA HQTA QTA HQTA QTA HQTA QTA HQTA As — — >104 >104 >104 >104 1000 5000 Bi >104 >104 — — 7000 5000 2000 2000 Sb 300 5000 1000 >104 — — 500 >104 Se 50 2000 500 >104 300 5000 — — Te 5000 >104 600 3000 >104 >104 >104 >104 J.Anal. At. Spectrom., 1999, 14, 827–830 829linear ranges (upper concentration/LOD), extended linear concentration range. Such improvement was obtained at no large expense with regard to sensitivity and detection limits, ranges using the proposed atomizer (HQTA) were observed for all elements, except Sb.except for As where a fivefold decrease in sensitivity was observed. However, an extended linear range was observed in most cases. The use of a lean flame was also tried, with much Mutual hydride forming element interferences better tolerance limits for the HQTA, but with a large sensi- The interference behaviour for both tubes in 10% v/v HCl is tivity drop. Thus, the use of this flame is not advisable. displayed in Figs. 2–5.The relative signal is referred to as the ratio between the absorbance in the presence of the interferent Acknowledgements and that of the pure analyte solution. A similar behaviour was observed for the other HCl concentrations (1 and 5%) studied. The Brazilian National Research Council is acknowledged for The tolerance limits (±10% change in the absorption signal ) the provision of financial support. in 10% v/v HCl for the four hydride forming elements studied are summarized in Table 3.References Among the studied elements, Sb and Se were the most critical interferents for As. However, the use of the proposed 1 P. Barth, V. Krivan and R. Hausbeck, Anal. Chim. Acta, 1992, 263, 111. atomizer extended significantly the non-interferent range in 2 B. Welz and M. Melcher, Anal. Chim. Acta, 1981, 131, 17. both cases. In the case of Te as intnt, an improvement 3 K. Dittrich and R. Mandry, Analyst, 1986, 11, 269. of at least twofold was observed and, for Bi, the atomizers 4 M.Yamamoto, M. Yasuda and Y. Yamamoto, Anal. Chem., 1985, were comparable. For Bi as analyte, the proposed atomizer 57, 1382. was also able to extend the non-interferent range for all cases 5 J. Dedina, Anal. Chem., 1982, 54, 2097. of interference. Sb and Se (as analytes) were the only two 6 L. Lajunen, T. Merkkiniemi and H. Hayyrynen, Talanta, 1984, 31(9), 709. cases where no improvement was observed, both related to 7 G. Hall and J. Pelchat, J. Anal. At. Spectrom., 1997, 12, 97. the Bi interference. However, in all other situations in which 8 M. B. de la Calle, R. Torralba, Y. Madrid and W. Palacios, an interference eVect was noticed, the tolerance limit was Spectrochim. Acta, Part B, 1992, 47(10), 1165. increased by the HQTA. 9 J. Hershey and P. Keliher, Spectrochim. Acta, Part B, 1986, 41(7), 713. 10 K. Dittrich, R. Mandry and U. Udelnow, Fresenius’ Z. Anal. Final discussion and conclusion Chem., 1986, 323, 793. 11 J. Dedina and I. Rubeska, Spectrochim. Acta, Part B, 1980, 35, The holed quartz T-tube was able to induce larger tolerance 119. limits of interference in nine of the 16 mutual interference 12 B. Welz and M. Melcher, Analyst, 1983, 108, 213. possibilities studied and a comparable performance with the 13 J. Dedina, Spectrochim. Acta, Part B, 1992, 47, 689. conventional T-tube was achieved in two cases. For the five remaining cases, no interference was observed in the studied Paper 8/09154D 830 J. Anal. At. Spectrom., 1999, 14, 827–830