Total (Organic) Carbon, Nitrogen and Sulfur Elemental Analysis of Soils and Eluates

Total (Organic) Carbon, Nitrogen and Sulfur Elemental Analysis of Soils and Eluates

Webinar

Dr. Dominik Margraf

Agenda Introduction 1

CN(S) Analysis of Soils 2

TOC Analysis of Soils and Soil Eluates 3

6/11/2015 Soil and Eluates | Webinar

Elemental Analysis of Soil


“Studies predict the world population to increase beyond 8.2 billion within the next 10 years, demanding ways to optimise the use of agrarian land to provide a larger food supply.”

• Agricultural science and analytics are the key to manage the fundamental growing demands for food, feed and water.

www.gov.uk

Elemental Analysis of Soil


• Carbon and nitrogen are important drivers in the element cycling of soils.

• Elemental analysis provides essential information about microbiological activity and organic matter, enabling a selective fertilization of arable land.

• Understanding the carbon-nitrogen ratio of soil is therefore of utmost importance.



Sample Preparation 2.1

Combustion Chemistry 2.2

Gas Separation and Detection 2.3

runAr Option: Argon vs. Helium as Carrier Gas 2.4



Challenges in Sample Preparation


• inhomogeneities within a sample may cause large deviations between two measurements

• solution • milling

• grinding

• large representative sample

– multi gram scale

vario MAX cube CN(S)– Dedicated Soil Analyzer


• Sample is simply filled in upright, reusable crucible

• Up to 5 g mineral sample

• Up to 5 ml liquid

• Up to 1 g organic sample

vario MAX cube CN(S) – Dedicated Soil Analyzer


• Automatic sample introduction via robotic arm

• soil samples form large amount of ashes

• time saving automatic ash removal • high lab efficiency

• 90 position carousel as standard

• unattended 24/7 operation

• Robust, maintenance-free mechanical design

Combustion According to Dumas Method


Organic compounds consists of C, H, N, O, S, Cl …

Combustion in O2 on oxygen donor at ~ 900°C

O2, N2, NOx, CO2 CO, CH4, SO2, H2O, HCl...

Typical problem of macro analysis (50 – 5000 mg)

Combustion tube

Unique Post-Combustion


Organic compounds consists of C, H, N, O, S, Cl …

Combustion in O2 on oxygen donor at ~ 900°C

O2, N2, NOx, CO2 CO, CH4, SO2, H2O, HCl...

post-combustion on catalyst (and H2O removal)

O2, N2, NOX, CO2, SO2, HCl...

Post-combustion tube

Unique Reduction Using Tungsten


• Reduction tube for binding of excess oxygen

• Effective tungsten for CN mode: W WO3 • one tungsten atom reacts with three oxygen atoms

• SO2 is bound on tungsten

• for CNS mode tungsten has to be replaced with copper

• Quantitative reduction of NOx to N2

• only N2, CO2 (and SO2 in CNS mode) exit reduction tube

tungsten

Reduction tube

Advanced Purge and Trap Technology

• Prior to detection gases are separated

• unique Advanced Purge and Trap Technology

• absorption column specifically removes CO2 from gas stream and N2 is being detected

• additional column in CNS mode to specifically absorb SO2

• CO2 absorption column is heated to desorption temperature • all CO2 is released at one controlled point in time

– focused, sharp peaks without overlap

– separation of C/N ratios up to 7000 : 1


Thermal Conductivity Detector with 10 Year Warranty

• measuring principle

• difference in thermoconductivity of gases causes detectable temperature difference


carrier gas + analyte gas

carrier gas

© http://wikipedia.de

gas

thermoconductivity [W/mK)]

H2 0,186 He 0,1567 Ar 0,0179 N2 0,0260

CO2 0,0168

Why Alternatives to Helium?


• helium is a limited resource

• Nobel Laureate Robert Richardson expects world supplies to last another 40 years and suggests a 150-fold increase of the helium price

• USA will sell their helium reserves

Robert Richardson Nobel Laureate in Physics 1996

Argon as Carrier Gas

• difference between argon and e.g. CO2 large enough?


carrier gas + analyte gas

carrier gas

© http://wikipedia.de

gas

thermoconductivity [W/mK)]

H2 0,186 He 0,1567 Ar 0,0179 N2 0,0260

CO2 0,0168

runAr Option Experimental Set-up


• instrument: vario MAX cube CN in helium or argon mode

• samples: certified standard soils • “sandy”, “loamy”, “silty”, “clay”,

“chalky”

• sample weight: approx. 1000 mg

• triple determination

• three independent measuring days

• identical operator

runAr Option Experimental Results Nitrogen


y = 1,014x + 1,554 R² = 0,99

0

50

100

150

200

250

300

350

400

0 100 200 300 400

ARG

ON

CAR

RIER

GAS

; ni

trog

en c

onte

nt

[ppm

]

HELIUM CARRIER GAS; nitrogen content [ppm]

NITROGEN DAY 1

sandy

silty

loamy

clay

chalky

• excellent experimental correlation

• Day 2 and Day 3 summarized as table

• error bars indicate 3 x abs. SD (99% confidence)

• for further information please

refer to

D. Margraf, Argon as Carrier Gas in CN elemental analysis of soils, Bulletin of the Swiss Chemical Soil Society, ISSN 1420-6773

runAr Option Experimental Results Carbon


• excellent experimental correlation

• Day 2 and Day 3 summarized as table

• error bars indicate 3 x abs. SD (99% confidence)

• for further information please

refer to


y = 1,000x + 63,716 R² = 0,999

0

1000

2000

3000

4000

5000

6000

0 1000 2000 3000 4000 5000 6000

ARGO

N C

ARRI

ER G

AS; c

arbo

n co

nten

t [pp

m]

HELIUM CARRIER GAS; carbon content [ppm}

CARBON DAY 1

sandy

clay; silty loamy

chalky

runAr Option Summary Experimental Results CN


• mean experimental results of three independent measuring days each run in triple determination

• exp. results ± 3 x abs. SD at 99% confidence interval

• Argon and helium based reveal excellent agreement within the experimental error


sample

nitrogen [ppm]

carbon [ppm]

Helium Argon Helium Argon

Chalky 364 ± 8 370±9 5330±40 5370±50

Clay 188 ± 6 190±20 2080±40 2190±40

Loamy 255 ± 1 260±8 2640±20 2690±50

Sandy 60 ± 10 60±2 820±10 820±30

Silty 169 ± 2 180±10 2120±20 2180±60

runAr option Experimental Results CNS


• Sample amount: 250 – 850 mg


• exp. results ± abs. SD

• runAr also suitable for a variety of matrices

C [%] N [%] S [%]

Soil helium argon

1.78 ± 0.01 1.78 ± 0.02

0.17 ± 0.001 0.18 ± 0.009

0.02 ± 0.001 0.01 ± 0.002

Maize kernel helium argon

43.2 ± 0.02 43.2 ± 0.01

2.66 ± 0.01 2.75 ± 0.01

0.22 ± 0.01 0.24 ± 0.02

Wheat flour helium argon

40.7 ± 0.04 40.5 ± 0.02

1.13 ± 0.002 1.17 ± 0.004

0.08 ± 0.005 0.08 ± 0.009

vario MAX cube – runAr Technology


• Use of Argon has been scientifically proven for the analysis of soils

• No time-consuming retrofit needed

• Argon instead of helium as a carrier gas further reduces cost-per-sample

• approx. 10% savings with runAr option based on German gas prices

• runAr option is free of charge

vario MAX cube – Analysis of Soil


• Soil from banana plantation in Ecuador • Sample weight: 1000 mg

• CN mode


Sample C [%]

N [%]

C/N ratio

Fluvisol Ah horizon 1.488 ± 0.003 0.051 ± 0.001 29.2

Fluvisol B horizon 0.670 ± 0.001 0.065 ±0.001 10.3

Fluvisol B/C horizon 1.921 ± 0.004 0.024 ± 0.001 80.0

vario MAX cube – Analysis of Soil


• Soil from a pasture Southwest USA • Sample weight: 550 - 750 mg

• six-fold determination

• 1 : 1 addition of WO3

Sample C [%]

N [%]

S [%]

Cambisol Ah horizon 1.112 ± 0.001 0.104 ± 0.001 0.0229 ± 0.0005

Cambisol B horizon 1.782 ± 0.010 0.168 ±0.001 0.0231 ± 0.0004

Cambisol Cw horizon 0.335 ± 0.013 0.0532 ± 0.027 0.0094 ± 0.003

Calcisol B horizon 4.187 ± 0.015 0.051 ± 0.001 0.0873 ± 0.0028

vario MAX cube – TC and TOC Analysis


• full agreement with ISO 10694



• TC sample weight: 1000 mg

• TOC sample weight: 300 mg • external acidification with 10% HCl

in silver foil cups

• dried at 80°C in silver foil cups

• silver foil cups simply placed in crucible

• TIC accessible by difference

TC [%] TOC [%]

Soil 1 2.91 ± 0.08 1.33 ± 0.01

Soil 2 2.61 ± 0.06 2.34 ± 0.02

Soil 3 0.525 ± 0.013 0.500 ± 0.015

Soil 4 9.37 ± 0.05 8.89 ± 0.01

Soil 5 1.59 ± 0.04 1.36 ± 0.04

Soil 6 0.685 ± 0.023 0.640 ± 0.008

Fertilizer...


Scope of Parameters

TC = TOC + TIC

TC = NPOC + POC + TIC

TC=Total Carbon

TOC=Total Organic Carbon

TIC=Total Inorganic Carbon

NPOC=Non Purgeable Organic Carbon

POC=Purgeable Organic Carbon

TNb=Total bound Nitrogen


Integrated Autosampler


Automatic sample dosing, automatic sample changing

• 32 position sampler, 40 ml vials, accepts TOC certified vials, stirrable, automatic external acidification for NPOC determination

• 50 position sampler, 12 ml vials, stirrable, automatic external acidification for NPOC determination

• 80 position sampler, 7 ml vials, manual external acidification for NPOC determination

• Suspension method possible

Real High Temperature Combustion


• Temperature programmable up to 1100°C

• High precision sample dosing

• Every part easily acccessible from the front side

• No tools required for maintenance work

• Automatic observation of maintenance intervals

Matrix Separation


Ash finger collects salt, particles

Catalyst remains clean

Nitrogen Analysis

• TNb: Total bound Nitrogen, includes all kinds of nitrogen compounds except N2

• Nitrogen is converted to NO, this reaction requires high temperatures (< 750°C not sufficient for full recovery)

• 3 detectors available

• IR: maintenance-free, high dynamic range

• Electrochemical cell: high sensitivity, most economic solution

• Chemoluminescence Detector: high sensitivity


Soil Eluates


• Challenge: high salt content from eluent

• Injection volume 0.5ml, combustion temperature 850°C; automatic external acidification

• Simultaneous TNb and TOC determination

• No clogging observed

TOC in eluates TOC [mg/l]

SDr [%]

TNb [mg/l]

SDr [%]

Soil eluate 1 CaCl2 11 g/l 6.67 4.0 na na

Soil eluate 2 K2SO4 87 g/l 71.1 1.78 12.5 11.2

Soil eluate 3 K2SO4 87 mg/l 136 3.53 27.2 7.70

Suspended Solids


• Challenge: High Amount of Non-Combustible Particles

• Pretreatment by Ultraturrax, Injection volume 0.2ml, combustion temperature 850°C, Dilution 1:1000

• No sedimentation observed

• no trend in NPOC

NPOC in solids (suspension method)

Soil

[w-%] Theor. Value: 0,37%

Sediment [w-%]

1st Injection 0,377 2,32

2nd Injection 0,362 2,26

3rd Injection 0,391 2,28

Mean 0,377 2,29

SD 0,014 0,03

SDr 3,86% 1,31%

Fully Automated Analysis of Solid Samples


• Only TOC in water analyzer worldwide with automatic sample feeder for solids

• Sample feeding by reliable ball valve technique

• Sample carousel with 80-120 positions

• Solids expansion kit for carbon amounts up to 20mg C abs.

TOC Determination in Solid Samples


• Sample weight approx. 100 mg

• Solid sample wrapped in silver foil, externally acidified and dried

• Triple determination

• Combustion temperature 900°C

TOC in solids Surface soil [w-%]

Clay [w-%]

Theor. Value: 0.139 w-%

1st det. 4,69 0,139

2nd det. 4,77 0,137

3rd det. 4,80 0,142

Mean 4,75 0,140

SD 0,05 0,003

SDr 1,1% 1,85%

Questions?

• Please use chat window

• Dr. Dominik Margraf

• [email protected]


Total (Organic) Carbon, Nitrogen and Sulfur Elemental Analysis of Soils and Eluates

Technology

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