Elemental analysis: NC determination by single and double reactor of high weight sample with the FlashSmart EA

TECHNICAL NOTE 42285

IntroductionThe Thermo Scientifi c™ FlashSmart™ Analyzer (Figure 1), operating with the dynamic fl ash combustion of the sample (modifi ed Dumas method), meets laboratory requirements, such as accuracy, reproducibility and high sample throughput for nitrogen and carbon determination.

The standard confi guration for NC analysis is based on a double-reactor system: the fi rst reactor is for the combustion and the catalytic oxidation of the combustion gases, the second one is used to reduce nitrous oxides as N2. The superior performance of the Thermo Scientifi c FlashSmart™ Elemental Analyzer reducing the amount of oxidation catalyst needed for NC analysis using a single combustion/reduction reactor tube (25 mm diameter). The reactor fi lled with less amount of oxidation catalyst and copper ensures the complete conversion of gases produced by the combustion.

Both confi gurations offer advantages such as the performance of a higher number of analyses before maintenance is needed. Additionally, with both solutions, similar range of sample weight can be used from low to high weight according to the sample nature and laboratory requirements. The data obtained are comparable, demonstrating the superior performance of the system.

AuthorsDr. Liliana Krotz, Dr. Francesco Leone and Dr. Guido Giazzi, Thermo Fisher Scientifi c, Milan, Italy

KeywordsAccuracy, Automatism, Combustion, Elemental Analysis, NC Single Reactor, NC Double Reactor, Repeatability

GoalTo demonstrate the performance of the Thermo Scientifi c FlashSmart

Elemental Analyzer for the nitrogen and carbon determination at high sample weight.

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MethodThe FlashSmart EA operates according to the dynamic flash combustion method. Samples are weighed in tin containers and introduced into the combustion reactor via the Thermo Scientific MAS Plus Autosampler with oxygen.

For NC double reactor configuration, after combustion, the resultant gases are carried by a helium flow to the oxidation catalyst (combustion reactor), then to a second reactor filled with copper, then through a water trap, a GC column and finally, detected by the Thermal Conductivity Detector (TCD) (Figure 2).

For NC single reactor configuration, after combustion, the resultant gases are carried by a helium flow to oxidation catalyst and to reduced copper, and pass through a halogen and sulfur absorber located inside the reaction tube. After the reaction tube, water is trapped, a GC column separates gases and at the end gases are detected by the Thermal Conductivity Detector (TCD) (Figure 3). To allow a high quality separation between nitrogen and carbon, a 3 meter gascromatographic column, installed in the oven, is used.

A complete report is automatically generated by the dedicated Thermo Scientific™ EagerSmart™ Data Handling Software and displayed at the end of the analysis.

ResultsA Reference Material and three different samples were analyzed in order to evaluate the performance of the FlashSmart Analyzer at high sample weight.

The Sandy Soil Reference Material (0.07 N% ± 0.01, 0.83 C% ± 0.05) was analyzed ten times by single and double reactor configurations. The sample weight was about 550 mg and 700 mg respectively. With single reactor, the system was calibrated with 6-7 mg of acetanilide while for double reactor 4-5 mg of aspartic acid was analyzed as standard, in both cases K factor was used as the calibration method. Table 1 shows the NC data obtained. All results are comparable with the expected values and fall within the uncertainty declared.

Figure 1. Thermo Scientific FlashSmart Elemental Analyzer.

TCD EagerSmartGC Column

Oxidation Reduction

Oxygen Helium

Autosampler

H2O Trap

Figure 2. NC double reactor configuration.

TCD EagerSmartGC Column

H2O Trap

High Quality Copper

HPAR Reactor

Ag/Co3O4

Copper Oxide

Autosampler

Ag/Co3O4

Oxygen Helium

Figure 3. NC single reactor configuration.

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Three different soil and sand samples were analyzed ten times to evaluate the repeatability of the analyzer, using single and double reactor configurations. Table 2 shows the NC data obtained using single reactor, while Table 3 shows the NC data obtained using the double reactor, including sample weights.

In Table 4 NC single and double reactors data at higher sample weight (up to 1 g) is compared. Data is comparable and the repeatability is acceptable relatively to the expected values.

ConclusionsThe Thermo Scientific FlashSmart Elemental Analyzer represents a valuable solution for the quantitative determination of nitrogen and carbon within different applications with excellent reproducibility and accuracy, relatively to the values expected.

Table 1. NC data of Sandy Soil reference Material.

NC single reactor configuration NC double reactor configuration

Weight (mg)

N%s.d.

RSD%C%

s.d.RSD%

Weight (mg)

N%s.d.

RSD%C %

s.d.RSD%

525.0 0.0724 0.853 697.5 0.0703 0.842

548.2 0.0713 0.853 680.9 0.0705 0.842

560.1 0.0715 0.840 693.1 0.0699 0.836

564.2 0.0709 0.841 672.1 0.0700 0.840

544.9 0.0716 0.0006 0.847 0.0056 696.0 0.0705 0.0003 0.834 0.0033

538.1 0.0722 0.81 0.852 0.66 694.4 0.0699 0.40 0.843 0.36

567.2 0.0712 0.839 719.7 0.0701 0.845

556.2 0.0714 0.853 696.2 0.0706 0.842

531.3 0.0717 0.846 700.5 0.0704 0.839

534.6 0.0704 0.846 608.6 0.0699 0.841

Soil A Soil B Sand

W (mg) N% C% W (mg) N% C% W (mg) N% C%601.2 0.0209 0.492 589.6 0.0385 0.842 990.4 0.0111 0.208

581.8 0.0201 0.494 594.2 0.0382 0.836 1001.0 0.0110 0.206

618.6 0.0207 0.496 595.6 0.0381 0.834 998.9 0.0110 0.206

602.3 0.0201 0.487 598.1 0.0379 0.830 1003.4 0.0110 0.205

610.7 0.0210 0.496 596.6 0.0380 0.832 996.7 0.0110 0.207

609.1 0.0204 0.491 595.3 0.0381 0.834 985.4 0.0112 0.209

589.7 0.0209 0.493 593.4 0.0383 0.837 1001.4 0.0110 0.206

605.2 0.0210 0.497 596.2 0.0381 0.833 982.6 0.0112 0.210

588.9 0.0204 0.496 603.6 0.0376 0.823 1007.3 0.0109 0.205

595.6 0.0206 0.495 593.6 0.0382 0.836 1005.6 0.0109 0.205

s.d. 0.0003 0.0031 s.d. 0.0002 0.0050 s.d. 0.0001 0.0177

RSD% 0.93 0.62 RSD% 0.63 0.60 RSD% 0.96 0.85

Table 2. NC data using single reactor configuration.

The nitrogen and carbon data of the Sandy Soil Reference Material obtained with the Thermo Scientific FlashSmart Analyzer fall within the range of the Reference Materials certificate. No memory effect was observed when changing the type of sample or the sample weight, indicating the complete detection of the nitrogen and carbon in the sample.

Thanks to the modularity of the FlashSmart Analyzer, same hardware, autosamplers and software can be used for single and double reactor configurations by using consumables upgrade kits. Thermo Scientific FlashSmart Analyzer can also work with Argon as carrier gas.

The FlashSmart Analyzer meets the requirements of several Official Methods for nitrogen and carbon determination.

Soil A Soil B Sand

W (mg) N% C% W (mg) N% C% W (mg) N% C%

703.2 0.0198 0.495 696.4 0.0384 0.834 1001.9 0.0116 0.212

703.3 0.0198 0.495 696.4 0.0383 0.832 999.8 0.0116 0.213

699.3 0.0199 0.498 696.3 0.0385 0.838 990.2 0.0118 0.215

705.3 0.0197 0.494 693.2 0.0386 0.838 1004.5 0.0116 0.212

693.7 0.0200 0.502 701.3 0.0381 0.828 1000.2 0.0116 0.212

704.4 0.0197 0.495 702.3 0.0381 0.827 996.3 0.0117 0.213

695.6 0.0200 0.501 700.4 0.0382 0.830 1005.7 0.0116 0.211

701.2 0.0197 0.497 699.3 0.0382 0.831 1000.2 0.0116 0.212

695.6 0.0200 0.501 692.2 0.0386 0.839 1006.6 0.0116 0.211

695.3 0.0200 0.500 703.3 0.0380 0.826 998.7 0.0117 0.213

s.d. 0.0001 0.0030 s.d. 0.0002 0.0048 s.d. 0.0000 0.011

RSD% 0.63 0.60 RSD% 0.56 0.52 RSD% 0.60 0.85

Table 3. NC data using double reactor configuration.

Sample

NC single reactor configuration NC double reactor configuration

W(mg)

Av. N%

s.d.RSD%

Av. C%

s.d.RSD%

W (mg)

Av. N%

s.d.RSD%

Av. C%

s.d.RSD%

Sandy Soil Ref. Mat.

- 550 0.07150.00060.81

0.8470.00560.66

- 700 0.07020.00030.40

0.8400.00330.36

Soil A - 600 0.02060.00030.93

0.4940.00310.62

- 700 0.01990.00010.63

0.4980.00300.60

Soil B - 600 0.03810.00020.63

0.8340.00500.60

- 700 0.03830.00020.56

0.8320.00480.52

Sand - 1000 0.01100.00010.96

0.2070.00180.85

- 1000 0.01160.00000.60

0.2120.00110.55

Table 4. Comparison of NC data at higher sample weight.

Official Organization Method

Official Italian Method on Soils Analytical Chemistry (Gazzetta Ufficiale)Method 248, 1999.

Nitrogen, Carbon and Organic Carbon in Soils

AOAC (Association of Official Analytical Chemists). Official Method 993.13.

Nitrogen (Total) in Fertilizers 2.4.02

ISO 10694, 1995 Soil Quality – Determination of organic and total Carbon after dry combustion (elementary analysis)

ISO 13878, 1998 Soil Quality – Determination of total Nitrogen content by dry

combustion (elemental analysis)

ISO 13878, 1998 Soil quality – Determination of total Nitrogen content by dry combustion (“elemental analysis”)

UNI EN 13654-2Soil improvers and growing media. Determination of nitrogen by combustion method.

Official Italian Method, Gazzetta Ufficiale, n. 146, 1998 New regulations for fertilizer’s control

EPA (Environmental Protection Agency) Method 440.0, 1997Determination of Carbon and Nitrogen in Sediments and Particulates of Estuarine/Coastal Waters Using Elemental Analysis

Find out more at www.thermofisher.com/OEA

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Table 5. Official Methods for nitrogen and carbon determination.