Accurate and Precise Analysis by Combustion with Elemental Analysis

Liliana Krotz, Francesco Leone and Guido Giazzi, Thermo Fisher Scientific, Strada Rivoltana, Milan, 20090, Italy

± ± The performance of the FlashSmart Analyzer with TCD Detector was evaluated with the Finally, an inorganic standard, ammonium sulfate (21.14 N% 0.20; 6.10 H% 0.10; 24.27 RESULTS S% ± 0.23) was analyzed five times to evaluate the accuracy and repeatability of the system ABSTRACT participation in International Round Robin Tests WEPAL (Wageningen Evaluating Programs

for Analytical Laboratories, Wageningen University, Netherlands) for NCS determination of for inorganic samples. Table 7 shows the data obtained. The validation of the Analyzer using the TCD Detector from low to high levels of sulfur was The importance of sulfur determination has grown significantly in the last years in many soil and plants. Table 4 shows the NCS results, which fall within the range of concentration performed by the analysis of three samples at low, medium and high sulfur concentrations. application fields (for example geological, agronomy, petrochemistry, environmental, food approved by the WEPAL statistic studies. Table 7. , and sulfur of ammonium sulfate by TCD Detector. For the low range the Soil Reference Material (0.014 S%) was used, for the medium range authenticity and forensic) and many of the classic methods are no longer suitable for sulfanilamide standard (theoretical 18.62 S%, accepted range ± 0.2) was chosen for the N% RSD% H% RSD% S% RSD% routine analysis. The Thermo Scientific™ FlashSmart™ Elemental Analyzer copes Table 4. NCS determination of Soils and Plants WEPAL samples by TCD Detector. analysis. For the high range, Sulfur Powder Reference Material was chosen (99.98 S%). effortlessly with laboratory requirements such as accuracy, reproducibility, and high 21.20 6.15 24.38 Table 1 shows the data obtained, demonstrating the performance of the Analyzer for sulfur 21.23 6.18 24.21 sample throughput. This paper presents sulfur data of pure organic standards, reference Nitrogen % % Sulfur % determination. 21.31 0.24 6.04 0.87 24.31 0.29 materials and several matrices to evaluate the accuracy and precision of the data using Sample 21.18 6.10 24.36 Wepal FlashSmart Wepal FlashSmart Wepal FlashSmart the different configurations and detectors. range Analyzer range Analyzer range Analyzer 21.21 6.13 24.26 Table 1. Performance of Sulfur determination by TCD Detector.

Sandy Soil 0.200-0.242 0.2316 2.41-2.85 2.43 0.0449-0.0550 0.0549 Low Range Medium range High Range (cod. 90)

INTRODUCTION Sample S% RSD% Sample S% RSD% Sample S% RSD% River Clay 0.158-0.195 0.177 1.66-1.80 1.68 0.0285-0.0338 0.0310

0.0141 18.68 99.99 The Thermo Scientific FlashSmart™ Elemental Analyzer (Figure 1) operates according Soil 0.0136 18.65 Sulfur 99.90 Sulfanilamide 0.177-0.230 0.210 3.13-3.62 3.32 0.0184-0.0252 0.0228 to the dynamic flash combustion of the sample (modified Dumas method) and can Ref. Mat. 0.0138 2.17 18.68 0.15 Powder 99.85 0.07 Sandy Soil (18.62 S%) determine the total sulfur concentration in simultaneous as CHNS, NCS modes, and as (0.0140 S%) 0.0144 18.64 (99.98 S%) 99.86 Moist Clay 0.066-0.091 0.077 0.84-0.94 0.881 0.0080-0.0120 0.0112 single sulfur analysis using the Thermal Conductivity Detector (TCD). Additionally, trace 0.0140 18.71 99.99 total Sulfur content can be accurately determined by the Flame Photometric Detector Lucerne 2.87-3.33 2.94 41.4-47.4 43.8 0.2342-0.2816 0.2512 (FPD). The coupling is simple and it allows the determination of total sulfur at high and In order to evaluate the accuracy of the analyses in non-organic standard sample matrices, Leaves low concentrations (up to 5-10 ppm) in the same analytical system, without matrix effect. Reference Materials were analyzed in simultaneous NCS and sulfur as single determination. Cherry 1.50-1.78 1.62 44.9-47.7 45.8 0.0646-0.0854 0.0709 The calibration was performed with BBOT using K factor. Table 2 shows the certified Laurel Leaf

Figure 1. Thermo Scientific FlashSmart Elemental Analyzer coupled with percentages and the relative uncertainty (±) while Table 3 shows the experimental results Pepper 1.76-2.16 1.92 38.5-43.2 39.6 0.5760-0.6912 0.5885 FPD Detector. obtained. The samples were analyzed in triplicate. The sulfur data are reproducible and Plant

comparable between both configurations, confirming the complete conversion and Carnation quantification of sulfur. 1.55-1.94 1.73 38.1-41.5 39.5 0.2489-0.2880 0.2589 (Straw)

Table 2. Certified Values of reference materials. Different matrices covering several application fields were analyzed using NCS configuration

by TCD Detector (Table 5) and only sulfur by FPD Detector (Table 6). The data shows Specification Reference Material excellent repeatability without matrix effect or influence of the nitrogen or carbon content, ± ± ± N% C% S% indicating complete combustion of the samples and proper quantification of the elements. CONCLUSIONS Low Organic Soil 0.133 0.023 1.61 0.09 0.014 n.a.

Table 5. NCS determination of different matrices by TCD Detector. The Thermo Scientific FlashSmart Elemental Analyzer, based on Dumas method, is a valuable Loamy Soil 0.27 0.02 2.75 0.12 0.044 n.a. solution for the weight percent sulfur analysis in all types of matrices (solids, viscous and liquid

Sandy Soil 0.07 0.01 0.83 0.05 0.014 n.a. samples) in terms of accuracy, precision, repeatability and sensitivity of results. Its automation Application Birch Leaves 2.12 0.06 48.09 0.51 0.172 0.03 Sample N% RSD% C% RSD% S% RSD% and high speed of analysis allow efficient analysis and help reduce overall operational costs. Field With a simple upgrade, the FlashSmart EA can determine simultaneously CHNS or NCS or Orchard Leaves 2.28 0.04 50.40 0.40 0.156 0.01 0.0585 0.8741 0.0103 sulfur single determination by TCD Detector (100 ppm-100 S%), or trace sulfur analysis when Soil 0.0582 0.26 0.8708 0.24 0.0104 1.49 Alfalfa 3.01 0.20 n.a. n.a. 0.27 0.04 the system is coupled with the FPD Detector (5-500 ppm S). The FlashSmart Analyzer 0.0583 0.8702 0.0101 Bladderwrack Algae 1.25 0.02 33.67 0.29 2.28 0.06 Agronomy performs the analysis without matrix effect when changing the sample and element content.

2.42 42.06 0.3192 The EagerSmart Data Handling Software controls both TCD and FPD Detectors with no need Spirulina Algae 10.81 0.25 47.21 0.39 0.60 0.03 Leaves 2.46 0.78 46.09 0.04 0.3144 1.45 for upgrades. 2.44 46.08 0.3101

12.94 51.06 0.7240 No differences in sulfur percentage was observed using CHNS, NCS or single S determination, METHODS Table 3. Experimental NCS and S data of reference materials. Meat 12.98 0.29 50.89 0.21 0.7320 0.74 indicating: 13.01 50.88 0.7212 Sulfur single Food • No interference of hydrogen peak on sulfur determination. Samples are weighed in tin containers and introduced into the combustion reactor via the Simultaneous NCS analysis 3.89 44.75 0.2870 Ref.Mat. analysis Animal • No adsorption of sulfur by the water trap. Thermo Scientific™ MAS Plus Autosampler with oxygen. After combustion, the analyte 3.85 1.07 44.89 0.78 0.2821 1.77 Feed • No adsorption of sulfur in the GC columns. By using 0.80 m or 2.00 m GC columns the data gases are carried by helium to a layer filled with copper, then swept through a water trap N% RSD% C% RSD% S% RSD% S% RSD% 3.81 44.24 0.2773 is comparable. before entering the GC column that separates the combustion gases before detection by 0.1350 96.33 0.7110 Low Org. Soil 0.131 0.88 1.611 0.32 0.133 0.75 0.131 0.76 Carbon • No influence of the content of nitrogen or carbon in the sample. the Thermal Conductivity Detector (TCD) or Flame Photometric Detector (FPD) 0.1343 2.26 96.24 0.05 0.7043 0.51 Black • Complete combustion. (Figure 2 and 3). For weight percent determination a complete report is automatically 0.1400 96.30 0.7091 Loamy Soil 0.271 0.74 2.738 0.20 0.0429 0.88 0.0430 0.48 Petrochemical • Complete conversion of sulfur in SO . generated by the Thermo Scientific™ EagerSmart™ Data Handling Software and 2 0.1205 84.50 0.6492 • Proper quantification of the sulfur in all types of matrices. displayed at the end of the analysis. Lubricant 0.1185 1.04 84.54 0.07 0.6477 0.47

Sandy Soil 0.709 0.71 0.848 0.56 0.154 0.98 0.157 0.97 0.1208 84.42 0.6536

Figure 2. Sulfur configuration by Figure 3. Sulfur configuration by Table 6. Sulfur determination of different matrices by FPD Detector. TCD Detector. FPD Detector. Birch Leaves 2.135 0.10 48.22 0.21 0.168 0.60 0.169 0.34 TRADEMARKS/LICENSING

Orchard Leaves 2.291 0.15 50.27 0.14 0.154 0.64 0.153 0.65 Application Application © 2017 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Sample ppm S RSD% Sample ppm S RSD% Field Field Thermo Fisher Scientific and its subsidiaries unless otherwise specified.

Alfalfa 3.056 0.38 43.74 0.10 0.269 0.57 0.275 0.56 17 46 Geological Sand 15 7.07 Petrochemical Graphite 46 1.26 Published at PittCon Conference and Expo, March 5-9, 2017, Chicago, IL, USA

Bladderwrack 17 45 1.260 0.00 33.66 0.11 2.281 0.22 2.278 0.20 Algae 65 13 PO42274 Maize Material Food 63 1.79 Catalyst 11 9.90 10.85 0.37 47.26 0.07 0.596 0.35 0.592 0.35 Starch Characterization Spirulina Algae 63 11

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