Accurate and Precise Sulfur Analysis using the Thermo Scientific FlashSmart Elemental Analyzer

Key WordsAccuracy, Combustion, Precision, Repeatability, Reproducibility, Sulfur

Goal To demonstrate the performance of the Thermo Scientific FlashSmart Elemental Analyzer for sulfur determination.

Introduction The importance of sulfur determination has grown significantly in geology, agronomy, petrochemistry, environmental sciences, food authenticity and forensics. Today many of the classical methods are no longer suitable for routine analysis. However, analytical instruments improve the reliability of data and laboratory productivity, without the use of hazardous chemicals.

AN

42266

APPLICATION NOTE

Dr. Liliana Krotz, Dr. Francesco Leone and Dr. Guido Giazzi Thermo Fisher Scientific, Milan, Italy

Figure 1. Thermo Scientific FlashSmart Elemental Analyzer.

The Thermo Scientific™ FlashSmart™ Elemental Analyzer (Figure 1), copes effortlessly with the wide array of laboratory requirements such as accuracy, reproducibility, and high sample throughput.

MethodsThe FlashSmart Elemental Analyzer operates according to the dynamic flash combustion of the sample (modified Dumas method). Samples are weighed in tin containers and introduced into the combustion reactor from the Thermo Scientific™ MAS Plus Autosampler with the proper amount of oxygen.

For simultaneous CHNS determination, after combustion, the analyte gases are carried by helium to a layer filled with copper, then onto the GC column (2 meters) that separates the combustion gases before detection by a Thermal Conductivity Detector (TCD), Figure 2.

For single sulfur determination or simultaneous NCS, after combustion, the analyte gases are carried by helium to a layer filled with copper, then swept through a water trap before entering the GC column (0.80 or 2 meters) which separates the combustion gases before detection by a Thermal Conductivity Detector (TCD), Figure 3.

For trace sulfur determination, after combustion, the analyte gases are carried by helium to a layer filled with copper, then swept through a water trap before entering the GC column (0.15 meter) which separates the combustion gases before detection by a Flame Photometric Detector (FPD), Figure 4 and Figure 5.

For weight percent determination a complete report is automatically generated by the Thermo Scientific™ EagerSmart™ Data Handling Software and displayed at the end of the analysis.

Figure 2. FlashSmart CHNS Configuration.

Figure 3. FlashSmart NCS or single S Configuration.

Figure 4. FlashSmart Sulfur Configuration by FPD Detector.

Figure 5. The FlashSmart EA with the Flame Photometric Detector.

Technical Specification FlashSmart Analyzers

ElementTheoretical Range 1 2 3 4 5

% (±) % RSD% % RSD% % RSD% % RSD% % RSD%

N 16.27 0.1616.2516.2816.28

0.1116.2816.2916.28

0.0416.3216.2916.31

0.0916.2316.2416.21

0.0916.2816.3016.27

0.09

C 41.84 0.3041.9641.9741.96

0.0141.7741.7941.68

0.1441.8041.8741.94

0.1741.9141.9241.92

0.0141.6641.6541.63

0.04

H 4.68 0.074.654.664.64

0.214.684.684.68

0.004.644.654.65

0.124.684.684.69

0.124.694.694.69

0.00

S 18.62 0.2018.7518.7418.73

0.0518.7718.7718.73

0.1218.6818.6218.70

0.2218.7718.5518.77

0.6818.7518.7118.78

0.19

Table 1. Sulfur data on Sulfanilamide in CHNS configuration.

Technical Specification FlashSmart Analyzers

ElementTheoretical Range 1 2 3 4 5

% (±) % RSD% % RSD% % RSD% % RSD% % RSD%

N 16.27 0.1616.3416.2816.32

0.1916.2916.3116.28

0.0916.2816.2816.26

0.0716.3116.3016.26

0.1616.2416.2716.21

0.18

C 41.84 0.3041.9541.9441.84

0.1542.0041.9341.94

0.0941.8741.7541.68

0.2341.6941.6841.63

0.0842.0341.9542.03

0.11

S 18.62 0.2018.6118.6818.64

0.1918.7418.7818.77

0.1118.5918.6118.79

0.5918.7118.6818.78

0.2718.7918.7618.71

0.21

Table 2. Sulfur data on Sulfanilamide in NCS configuration.

ResultsTo demonstrate the performance of the FlashSmart Analyzer for sulfur determination in CHNS, NCS and S-only configurations, three systems were set-up to perform typical analytical tests. For CHNS and NCS, the calibration was performed with Methionine standard using K factor as the calibration method.

Then, three analyses of sulfanilamide were performed as unknown. Table 1 shows the correlation between the CHNS theoretical percentages of the sulfanilamide standard, the accepted range according to the technical

specification of the system and the experimental data obtained in triplicate measurements for each instrument. Table 2 shows the relative NCS data.

The sulfur data obtained in CHNS configuration are comparable with those obtained in NCS configuration confirming the proper quantification of the sulfur content without adsorption of sulfur in the water trap or on the GC columns. All data are acceptable and comparable confirming the repeatability and reproducibility expected under different configurations.

The validation of the concentration range for sulfur, which is determined using the TCD Detector from low to high amounts, was checked by the analysis of three samples at low, medium and high sulfur concentrations. For the low range a Soil Reference Material (0.0140 S%) was used; for the medium range, sulfanilamide standard (theoretical 18.62 S%, accepted range ±0.2) was chosen for analysis. For the high range, sulfur powder was chosen (99.98 S%).

Technical Specification FlashSmart Analyzers

ElementTheoretical Range 1 2 3 4 5

% (±) % RSD% % RSD% % RSD% % RSD% % RSD%

S 0.135 0.040.1350.1360.135

0.4270.1370.1380.137

0.4200.1360.1350.135

0.4250.1350.1350.134

0.4290.1370.1370.136

0.422

Table 3. Sulfur data measured on Thermo Scientific Pasta Reference Material.

Low Range Medium Range High Range

Sample S% RSD% Sample S% RSD% Sample S% RSD%

Soil Ref. Mat(0.0140 S%)

0.01410.01360.01380.01440.0140

2.1696Sulfanilamide

(18.62 S%)

18.6818.6518.6818.6418.71

0.1486Sulfur

Powder (99.98 S%)

99.9999.9099.8599.8699.99

0.0684

Table 4. Performance of sulfur determination by TCD Detector.

In order to evaluate the accuracy of the analyses in matrices that are different from pure organic standards, several Reference Materials were analyzed in simultaneous NCS and for sulfur as single determination. The calibration was performed with BBOT using K factor as the calibration method.

Table 5 shows the certified percentages and the relative uncertainty while Table 6 shows the experimental results obtained. The sulfur data obtained are reproducible and comparable between both configurations, confirming the complete conversion and quantification of sulfur.

Table 4 reports the analytical data that demonstrates the accuracy and precision of the Analyzer for sulfur determination.

For trace sulfur determination by FPD Detector, Thermo Scientific™ Pasta Reference Material was analyzed. The calibration method used was Quadratic Fit.

Table 3 shows the certified sulfur data, the accepted range and the experimental sulfur data obtained on five FlashSmart Analyzers demonstrating accuracy and precision on the different instruments.

Reference Material Information

Specification

N% Uncertainty (±) C% Uncertainty (±) S% Uncertainty (±)

Low Organic Content Soil 0.13 0.023 1.61 0.09 0.01 n.a.

Loamy Soil 0.27 0.02 2.75 0.12 0.04 n.a.

Sandy Soil 0.07 0.01 0.83 0.05 0.01 n.a.

Birch Leaves 2.12 0.06 48.09 0.51 0.17 0.03

Orchard Leaves 2.28 0.04 50.40 0.40 0.16 0.01

Alfalfa 3.01 0.20 n.a. n.a. 0.27 0.04

Bladderwrack Algae 1.25 0.02 33.67 0.29 2.29

Spirulina Algae 10.81 0.06 47.21 0.39 0.60 0.03

ReferenceMaterial

Simultaneous NCS analysis Sulfur single analysis

N% RSD% C% RSD% S% RSD% S% RSD%

Low Organic Content

0.1300.1320.131

0.881.6051.6151.612

0.320.01340.01330.0132

0.750.01310.01320.0130

0.76

Loamy Soil0.2720.2680.270

0.742.732.742.74

0.200.04320.04250.0431

0.880.04320.04280.0429

0.48

Sandy Soil0.07050.07110.0715

0.710.8440.8480.851

0.560.01520.01540.0155

0.980.01560.01570.0159

0.97

Birch Leaves2.142.142.13

0.1048.1148.3141.25

0.210.1670.1690.168

0.600.1680.1690.169

0.34

Orchard Leaves2.292.282.29

0.1550.2550.3550.22

0.140.1530.1540.155

0.640.1520.1530.154

0.65

Alfalfa3.043.063.06

0.3843.7743.6943.75

0.100.2680.2710.269

0.570.2770.2740.273

0.56

Bladderwrack Algae

1.261.261.26

0.0033.6933.6633.62

0.112.2822.2762.286

0.222.2782.2742.283

0.20

Spirulina Algae10.8110.8910.85

0.3747.2247.2647.29

0.070.5940.5950.598

0.350.5940.5930.590

0.35

Table 5. Certified values of Reference Materials.

Table 6. Experimental NCS and S data from several Reference Materials.

Finally, different matrices were analyzed using CHNS and NCS configuration by TCD Detector (Tables 7 and 8) and trace sulfur by FPD Detector (Table 9) to show the aplicability of sulfur determination in different application fields.

Table 7. CHNS determination of different matrices by TCD Detector.

Application field Sample N% RSD% C% RSD% H% RSD% S% RSD%

Geological

Rock 10.00620.00650.0064

2.3990.15110.15590.1577

2.2020.16430.17740.1690

3.8990.17910.17330.1800

2.049

Rock 20.00330.00350.0031

6.0600.09970.09820.0975

1.1400.3680.3680.368

0.0980.02690.02550.0260

2.682

Food

Supplement0.3300.3330.329

0.53340.61540.39640.630

0.3236.2746.3316.323

0.4880.3660.3680.357

1.581

Gelatine15.79615.83515.838

0.14844.61544.64744.624

0.0376.6236.6586.622

0.3090.5310.5360.537

0.601

Petrochemical

Black Coal1.3351.3301.328

0.27179.86379.66879.685

0.1364.5634.5694.559

0.1100.3450.3400.351

1.595

Bio-Fuel0.503 0.499 0.500

0.42545.19745.17944.952

0.3035.6715.6385.596

0.6630.03240.03170.0327

1.590

Material Characterization

Carbon Fiber3.78803.76673.8433

1.040693.630693.241193.6027

0.23240.31330.32900.3125

2.92330.03240.03590.0339

5.1544

Rubber0.6260.6280.622

0.47081.96281.86682.361

0.32011.21811.24911.272

0.2431.5611.5531.572

0.606

The data obtained show an excellent repeatability without matrix effect, which indicates complete combustion of the samples, no memory effect and proper quantification of the elements.

Table 8. NCS determination of different matrices by TCD Detector.

Table 9. Sulfur determination of different matrices by FPD Detector.

Application field Sample N% RSD% C% RSD% S% RSD%

Agronomy

Soil 0.0590.0580.058

0.2600.8740.8710.870

0.2400.0100.0100.010

1.490

Leaves2.4202.4582.436

0.78242.06042.09242.085

0.0410.3190.3140.310

1.450

Food

Meat12.93912.97913.013

0.28651.06450.88650.879

0.2060.7240.7320.721

0.742

Animal Feed3.8923.8453.810

1.06944.75244.89344.235

0.7760.2870.2820.277

1.773

Petrochemical

Carbon Black0.1350.1340.140

2.15696.32996.24196.300

0.0460.7110.7040.709

0.505

Lubricant0.1210.1180.121

1.04284.50584.54084.418

0.0750.6490.6480.654

0.472

Environmental

Solid Compost1.6071.6221.601

0.67216.71116.79116.844

0.3992.9202.8972.903

0.425

Liquid Compost0.1430.1460.144

0.8222.3622.3322.389

1.2100.0500.0500.050

0.614

Material Characterization

Paper0.0280.0300.028

3.02742.33742.36642.327

0.0470.0390.0420.039

4.337

Additive0.9250.9300.917

0.66575.43775.29975.319

0.0992.9882.9802.969

0.318

Application field Sample ppm S RSD% Application field Sample ppm S RSD%

Geological Sand171517

7.070 Petrochemical Graphite464645

1.264

Food Maize Starch656365

1.795Material

CharacterizationCatalyst

131111

9.897

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For Research Use Only. Not for use in diagnostic procedures. © 2016 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries unless otherwise specified. AN42266-EN 0716

ConclusionsThe Thermo Scientific FlashSmart Elemental Analyzer is a robust solution for weight percent sulfur analysis in all type of sample matrices (solids, viscous and liquid samples) in terms of accuracy, precision, repeatability and sensitivity of results.

The inherent automation and high speed of analysis improves efficiency and help reduce overall operational costs.

The FlashSmart Analyzer can determine sulfur concentration in simultaneous CHNS and NCS mode, and also as sulfur measured on its own TCD Detector (100 ppm–100 S%). Additionally, with a simple upgrade, trace sulfur amounts can be measured when the Analyzer is coupled with a FPD Detector (5–500 ppm S).

The analyses show that no differences for sulfur percent determination between CHNS, NCS or single S determination modes, indicating:

• No interference from the hydrogen peak on sulfur peak.

• No matrix effect, even when changing the sample and element content.

• No adsorption of sulfur by the water trap.

• No adsorption of sulfur on the GC columns used.

• No influence from the nitrogen or carbon content.

• Complete combustion of all sample matrices.

• Complete conversion of sulfur to SO2.

• Proper quantification of the sulfur in all types of matrices.

The EagerSmart Data Handling Software controls the TCD and FPD Detectors without any upgrade needed.

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