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Download Author Version (PDF) Analytical Methods Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/methods Page 1 of 21 Analytical Methods 1 2 3 4 Multi-element analysis of sulfuric acid by oaTOF-ICP-MS after matrix 5 6 modification with barium bromide 7 8 9 10 11 Lenka Husáková*, Iva Urbanová, Tereza Šídová, Tomáš Mikysek 12 13 14 Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, 15 16 Pardubice, Studentska 573 HB/D, CZ-532 10, Czech Republic 17 18 19 20 21 * Corresponding author: Tel. +420 466 037 029 fax: +420 466 037 068 Manuscript 22 23 E-mail address: Lenka.Husakova@upce.cz 24 25 26 27 28 29 30 31 Accepted 32 33 34 35 36 37 38 39 40 Methods 41 42 43 44 45 46 47 48 49 50 51 Analytical 52 53 54 55 56 57 58 59 60 1 Analytical Methods Page 2 of 21 1 2 3 Abstract 4 5 6 In this work a novel method for simultaneous multi-element analysis of sulfuric acid by 7 8 inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (oaTOF- 9 10 ICP-MS) after matrix modification with barium bromide was introduced. For this purpose sample 11 12 13 aliquots consisting of 10% (w/w) sulfuric acid were mixed with barium bromide, after the 14 15 precipitation of sulfates the resulting liquid phase was aspirated with a concentric glass nebulizer 16 17 18 for TOF-ICP-MS determination. Separation of sulfur as a precipitated non-soluble barium sulfate 19 20 enables the elimination of spectral interferences originating from different sulfur containing 21 Manuscript 22 + + + + + + + + + + species like SN , SNH , SO , SOH , SOH2, SCO , SNOH , SO2 , S2 , SO2H , or S2H onto the 23 24 25 determination of e.g. Ti, Zn, Ge, Cu,. After that, direct, reliable, and simultaneous determination 26 27 of 15 elements (Be, Ti, V, Cr, Mn, Ni, Co, Cu, Zn, Ga, Ge, As, Sn, Sb, Te) at trace and ultra- 28 29 trace levels in sulfuric acid can be performed under optimum instrumental conditions and by 30 31 Accepted 32 using Rh as an internal standard. Accuracy and precision was assessed by analysing sulfuric acid 33 34 and by comparison of the results of the proposed method with those found by high resolution 35 36 ICP-MS method. Results of both methods were in a good agreement for Ti, V, Cr, Mn, Ni, Co, 37 38 39 Cu, Zn, Ga, Ge, and As. The accuracy was for all of the 15 elements also checked by analytical 40 Methods 41 recovery study. The reported method has a precision better than 12.5%. 42 43 44 45 Keywords: oaTOF-ICP-MS; Trace elements; Sulfuric acid; Interferences in inductively coupled 46 47 plasma mass spectrometry; Precipitation; Barium bromide; Matrix modification 48 49 50 51 Analytical 52 53 54 55 56 57 58 59 60 2 Page 3 of 21 Analytical Methods 1 2 3 4 5 6 7 8 1. Introduction 9 10 Large quantities of sulfuric acid are used in many applications in a wide range of 11 12 13 industries including the manufacture of fertilizers, lubricants, drugs-pharmaceuticals, rayon, 14 15 metal processing, batteries, food, dyes and pigments, or chemical manufacturing1. Due to its 16 17 aggressive dissolution properties sulfuric acid is prone to acquire metals from other sources and 18 19 2 20 may represent a significant source of contamination in the above applications . As the sulfuric 21 Manuscript 22 acid quality and purity determines its use for different industrial processes, the targeted trace 23 24 2-6 25 metal content must be frequently monitored . 26 27 In order to determine trace element purity levels in sulfuric acid, inductively coupled 28 29 plasma mass spectrometry is an indispensable analytical tool. However, direct analysis of even 30 31 Accepted 32 diluted sulfuric acid is not easy as it can produce rapid corrosion of nickel cones which are 33 34 commonly used in ICP-MS6. In addition matrix-based interferences make the determination 35 36 difficult3, 4. Some non-spectroscopic effects can be compensated by dilution of the sample 1:10 37 38 3-6 3 2 39 m/m in high purity water , evaporation of the sample , use of hot-plasma conditions , analysis 40 Methods 41 by standard addition or the use of internal standard elements4. However, spectral interferences7, 8 42 43 originating from S-based species produced from matrix components in the plasma can be difficult 44 45 2-6, 9 2, 3, 46 to overcome , especially with conventional low-resolution quadrupole mass spectrometers 47 48 5. While cool-plasma ICP-MS can be used successfully to remove Ar, ArH+, ArO+ interfering 49 50 3, 4 51 species on Ca, K, and Fe respectively , S-based interferences are still important with the Analytical 52 2-5 53 elements such as Ti, Cr, Co, Ni, Cu, Zn, As, when direct analysis is performed . For 54 55 conventional low-resolution quadrupole ICP-MS the collision/reaction cell ICP-MS is a powerful 56 57 2, 3 58 correction technique to minimize interferences on analyte of interest .While for older Q-ICP- 59 60 3 Analytical Methods Page 4 of 21 1 2 3 MS systems the reduction of the multi-element capabilities can be observed, for modern 4 5 6 quadrupole ICP-MS systems this problem has been overcome. Sector-field ICP-MS with its high 7 8 mass resolution can deal with polyatomic interferences originating from major elements even for 9 10 samples with a complex matrix.4, 6. While losing sensitivity in the high resolution mode, the 11 12 13 multi-element capability is maintained. These methods may be, however, less accessible to 14 15 routine analytical laboratories owing to the high cost of the instrumentation. 16 17 18 ICP time-of-flight mass spectrometers are more accessible to routine analytical 19 20 laboratories, and can overcome the major limitations associated with the scanning nature of other 21 Manuscript 22 ICP-MS instrumentation with the advantages of high speed and simultaneous mass determination 23 24 10 25 without any compromise in mass range, sensitivity or precision . Enhanced resolution for the 26 27 oaTOF mass analyzer is another advantage; however this is not sufficient to completely resolve 28 29 interference signals from different polyatomic species during the analysis of complex samples. In 30 31 Accepted 32 order to control the spectral effects during the TOF-ICP-MS analysis the mathematical correction 33 34 equations11, 12 without11 or with the implementation of microwave digestion12 or some another 35 36 approaches employing matrix modification13 were used for the analysis of urine11 and food 37 38 12, 13 39 samples previously . 40 Methods 41 Despite the development of methods for the analysis of sulfuric acid by quadrupole ICP- 42 43 2, 3, 5 44 MS which employ collision/reaction cells for interference removal and high resolution ICP- 45 4, 6 46 MS instruments , currently no method is available for this purpose when using TOF-ICP-MS. 47 48 In this work modification of the sample preparation procedure by the addition of barium bromide 49 50 51 to sulfuric acid samples in order to precipitate and separate sulfates prior to TOF-ICP-MS Analytical 52 53 analysis is introduced. The main advantage of this approach is that it serves as a cheap, rapid and 54 55 simple solution for overcoming the spectral effects from different S-based polyatomic species on 56 57 58 the determination of some elements (e.g. on Ti, Zn, and Cu) whose determination is difficult 59 60 4 Page 5 of 21 Analytical Methods 1 2 3 when using instruments with low resolving power. Finally, the developed method was found to 4 5 6 be accurate and precise for a multi-element determination of 15 trace elements in sulfuric acid. 7 8 9 10 11 2. Material and methods 12 13 14 2.1 Instrumentation 15 16 The Optimass8000 oaTOF-ICP-MS instrument (GBC Scientific Equipment Pty. Ltd., 17 18 10 19 Australia) of which a detailed description is given in ref. was used throughout this study. 20 21 Details of the instrument and the operating conditions are summarized in Table 1. Using typical Manuscript 22 23 -1 -1 24 operating conditions sensitivity of 15000 counts s per µg L (mass integrated peak) and 25 26 resolution (full width at half maximum intensity) of 1800 was achieved for 139La+. For 238U+, the 27 28 same parameters were 17000 counts s-1 per g L-1 and 2100, respectively. 29 µ 30 31 Comparative measurements were performed using a high performance, double focusing Accepted 32 33 magnetic sector field Thermo Scientific™ ELEMENT 2™ ICP-MS (Thermo Scientific, Bremen) 34 35 36 attached to a CETAC Aridus II™ Desolvating Nebulizer system (CETAC Technologies Inc., 37 38 USA).
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