Elemental, My Dear Watson
Paul Middlestead
University of Ottawa, G.G. Hatch Laboratory
For 19th Continuous Flow Conference, Calgary, 2013
Who/what is this talk for?

This talk is for new users
We will touch the basics on Elemental analysers
A mix bag of tricks and advices
Refer to manufacturer’s instruction manuals
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Only endorsed products are:
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Rickards White
Rickards Red
and
Meet my family
Large
capacity
EA
TC/EA
Combustion
Pyrolysis
NCHS
HO
S only
TOC
Stable
isotopes
12000C
15000C
Meet Grand Pa


Leco is the most popular manufacturer of elemental analysers.
Every department has one or two of those accumulating dust.
Static combustion using oxygen: not suitable for IRMS
Let’s touch on
•Elemental Analyser as an…instrument
•Schematics
•Autosamplers
•Flash combustion
•Chemicals & Configurations
•Gas Chromatography
•Thermal Conductivity Detector
•Typical run
•Common problems
•EA-IRMS
EA as an …. instrument
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Simultaneous determination of Nitrogen, Carbon, Hydrogen,
Sulfur, Oxygen
Measuring range: 100 ppm to 100%
Sample size: 0.1 to 1000 mg / 0.1 to 25 ul
Detection limit: 10 ppm
Accuracy: 0.3% - 0.02% absolute
Manufacturers, models blablabla
CE instruments (Carlo Erba) models 1108,
1110, NA 1500, NA 2100, Flash 1112
 Costech Model ECS4010
 Elementar cube family
 Eurovector models EuroEa3028-HT, Ea3024IRMS, pyrolysis model
 Sercon-Integra
 TC\EA Thermo
…
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EA : Bulk analysis of NCHS/O
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Organic compounds
Pharmaceuticals
Organometallics
Petrochemicals
Gasoline & fuels
Graphite
Carbides & nitrides
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Metals & alloys
Polymers
Explosives
Hydrocarbons
Soils
Coal & coke
Liquids
In short, you can combust your grandmother!
Typical EA setup with IRMS
Ref gas 1
Ref gas 2
Elemental
Analyser
(CNS)
(OH)
He
2m
Interface
Isotope Ratio
Mass Spectrometer
EA picture
Elemental Analyser Schematic
He
O2
Autosampler
Gas chromatography
Column in oven
Thermal Conductivity Detector
Water
Trap
TCD
N2
Combustion
Chemicals
1020C
Reduction
Chemicals
650C
CO2
H2O
SO2
EA line
out
Found the problem with the
previous slide?
A beer if you do…
(5 seconds)
Elemental Analyser Schematic
He
O2
Autosampler
Gas chromatography
Column in oven
Thermocouple
Detector
Water
Trap
TCD
N2
Combustion
Chemicals
1020C
Reduction
Chemicals
700C
CO2
H2O
SO2
EA line
out
A cold Rickard’s Red
for me please.
Typical Analysis Procedure for EA
1.
2.
Sample/Std is weighed and wrapped in tin
foil, placed in culture tray/autosampler
Sample drops is flash-combusted in O2 in He
stream, causing rapid cracking and oxidation
of gases stoichiometrically equivalent to their
elemental components, some gas oxides need
to be reduced before obtaining final products
(N2, CO2, H2O, SO2) i.e. oxidation and
reducing reactions involved
Typical Analysis Procedure for EA
3. Separation of gases by gas chromatography
or chemical column traps
4. Detection by thermal conductivity detector
(TCD) or IRMS.
5. Curve made from weighing certified stds (for
isotope and/or quantitative measurements)
Some torture tools…
Well well, got culture?
Super size me
MAIS C’EST IMPOSSIBLE!
C’EST FANTASTIQUE!
Filters? Careful!
Not flat please
Autosamplers (AS128)
Autosamplers (AS200)
Zero Blank
Zero Blank modified
Special tools required
ECS 4010
Be good to yourself
Take 20 minutes to study the gas
schematics of your instrument
Loop concept (a)
TO AUTOSAMPLER
He only
He
99.996
O2
99.998
SAMPLE LOOP
10 , 5 , 3 ML
OXYGEN
OUT
Loop concept (b)
TO AUTOSAMPLER
He + O2 + He
He
O2
SAMPLE LOOP
10 , 5 , 3 ML
OXYGEN
OUT
Sample dropping
Combustion starts
Injected O2
Sample drops
Flash should occur
within 2-3 seconds
of being dropped
START
0
10
20
seconds
30
40
Why you Tin man?
•
•
•
•
PLATINUM: Absorbs much of the heat of the reactor
before passing it on to the sample, slowing down
reaction
ALUMINIUM: Supplies good oxidation flash and
prime sample ignition but does not melt or mix with
the sample thus does not promote inner oxidation
SILVER: Melts at 9600C, does not take part in the
combustion, retains trace of carbon when in molten
state
TIN: Inexpensive & takes active part in process. Melts
at 2350C with very low enthalpy, intermixes with
organic and inorganic substances, expedites the final
oxidation reaction
Dynamic Flash Combustion
Oxidation of TIN gives a tremendous enthalpy reaction
Sn + O2
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2350C
SnO2 + 142 000 cal
1700-1800C
Increases local temperature from 10200C to 170018000C, accelerating combustion
Cancels the endothermic effects of tin melting (0.14
calories required for melting vs 11.96 calories given
off during flash)
Equalizes the thermal degradation of any substance
Uses available oxygen immediately and requires
less
Dynamic Flash Combustion
Oxidation of TIN gives a tremendous enthalpy reaction
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Ensures that sample oxidation is performed in
gaseous phase (95%) rather than in the catalytic
reactions
Breaks down any matrix without combustion aid
Converts the sample into a homogenous,
quantitative combustion gas mixture
(unfractionated)
Provides a gaseous plug for the entry into the GC
column
Forms tin oxide, an oxidation catalyst
Provides visual indication of the reaction
Let’s get cracking
C
N
Combustion
tube
Reduction
tube
CO2
CO2
N2 + NxOx
N2
H
H2O
H2O
S
SO2 + SO3
SO2
Chemicals and Configurations
• System should be optimized for element(s) to be analyzed
• One-tube system: both oxidant catalyst and reducing
chemicals in one tube; usually used if S is to be analyzed
• Two-tube system: one tube for oxidant, one tube for reducing
chemicals; usually used for N, NC or NCH
• Chemical traps: Mg Perchlorate or Anhydrone will trap H2O,
and Carbosorb will trap CO2 (and SO2)
Configuration
CN
Configuration
S
Small is
beautiful
More torture tools
Using grinding tools and diluted Nitric acid, one can re-use
combustion and reduction tubes
Gas Chromatography
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Gas chromatographic columns will separate different
components according to their polarity and molecular size.
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Factors influencing the quality of the chromatography:
column length, size of packing, tube diameter, stationary
phase type, flow rate, temperature.
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Packed column: packed polymer beads, different sizes
available. High capacity , low resolution.
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Capillary column: small capillary with polymeric film on
inner wall. High resolution, low capacity.
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Deactivated fused silica is free of adsorption problems
encountered with most packings or capillaries columns.
Gas Separation/ GC
He + N2 , CO2 , H2O , SO2 + He
He + SO2 + H2O + CO2 + N2 + He
INCREASING POLARITY
OF GASES
What after we separate?
He + SO2 + H2O + CO2 + N2 + He
DETECTOR
DETECTOR
CO2
N2
SO2
H20
TIME
Gas Separation / Purge & Trap
TCD
SO2
H2O
CO2
Detectors
Thermal conductivity detector (TCD)
Heated filament from which heat is removed at a
constant rate by He gas stream. Change in heat
transfer is caused by presence of analyte molecules
with different thermal conductivities than He.
Relatively low sensitivity, excellent range and linearity.
Non-destructive.
Electron capture detector (ECD)
Electrons are captured by organic species in ionized
carrier; used for trace sulfur determination.
Isotope Ratio Mass Spectrometer (IRMS)
TCD schematic
Typical output of EA, text book
CO2
N2
H2O
SO2
Balance
Balance: Get the best
A 0.01mg readability translates in an error of
0.25% on a 2 mg sample (say on 100% carbon)
IAEA (and NIST) standards
Links available on Isogeochem
STD: Making it on your own…
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Best : %N, 15N, %C, 13C
Test different materials and pray
Make your own:
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Caffeine
L-glutamic acid
Mixtures such as sucrose + potassium nitrate
Mix in solution of natural + enriched/depleted material then dried,
powdered, sieved
STD: Not making it on your own…
STD: Not making it on your own…
Can also contact other
university labs to buy or
obtain their internal
standards.
Calculation Methods
1. K-Factor (Single point calibration with blank substraction)
Calculated % = K * (Area unk – Area blk)
Weight unk
Where K = Weight std * Theor std %
Area std - Area blk
Calculation Methods
Wt * Th std %
2. Linear Fit (Least square linear regression)
Calculated % = m * Area unk + b
Weight unk
Peak Area
Calculation Methods
Wt * Th std %
3. Quadratic Fit (Least square quadratic regression)
Calculated % =
a * Area unk2 + b * Area unk + c
Weight unk
Peak Area
An update…
Most elemental analysers manufacturers
have considerably refined their calculation
methods, with more complex algorithms,
low-high ranges and statistical tools.
Common Problems (I)
CO2 Blank
•Contaminated capsules
Wash or change batch
•Memory effect due to ashes
Remove ashes
Unreproducible blank
N2 Blank
Increasing blank values
•Copper exhausted
Repack reduction tube
•High mass 30
Repack reduction tube
Common Problems (II)
•Autosampler purge off
•Very high mass 28
Switch on!!
Very high blank values
•Impure oxygen
• High mass 28
Replace O2
High & constant blank
Common Problems (III)
No signal
N2
?
CO2?
Ghost/double peaks
•Detector off
Switch on!
•Broken filament
Call engineer
•Low carrier flow
Check flow rate & blockage
•MS valve closed, open split problem
•Leak
Find and fix
•CO2 or H2O trap exhausted
Replace packing of trap
Common Problems (IV)
Peak broadening
Baseline drift
•Presence of dead volume
Check trap(s) or packing
•Incomplete combustion
Remove ashes, check drop time
(flash), exhausted chemicals
•Leak
Find and fix
•Carrier flow fluctuating
Check GC oven temperature
•Outgassing of chemicals
Leak check or check leaks (1)
Pressure check
EA
•Cap exit port
•Increase P of He to 1.3 bar, wait 3 minutes
•Close regulator
•Pressure gauge should not move for 5 minutes
Flow check (requires electronic mass flow controller)
EA
•Cap exit port
•Monitor flow for 3 minutes
•Flow should drop to 0 ml/min
Leak check or check leaks (2)
Leak check with IRMS
Interface
EA
•EA has been leak checked
•EA chemicals have outgassed (12 hours)
•Tune to Ar (mass 40)
•Should meet manufacturer’s requirements
•Use Ar cylinder to hunt
Ar
MS
Elemental Analyser Schematic for IRMS
Autosampler
Water trap
Gas chromatography
Column
Thermocouple
Detector
TCD
N2
Combustion tube Reduction tube
CO2
To MS
Interface
Diluter &
ref gas
WAKE UP!
Did you find the small error in the last slide?
Elemental Analyser Schematic for IRMS
Autosampler
Water trap
Gas chromatography
Column
Thermocouple
Detector
TCD
N2
Combustion tube Reduction tube
CO2
To MS
Interface
Diluter &
ref gas
Considerations for EA-IRMS
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Water is removed via Mg Perchlorate/sicapent trap
---water and mass spectrometer do not mix---Configuration should be optimized for gas of
interest
Leak free (mass 28 & 40, use Argon as leak probe)
Low and stable background (mass 28, 18, 40, 44)
Dynamic range must be respected, do use target
beam
Best sequence is carefully planned ie known
concentration of samples
Garbage in……Garbage out
Some useful info
Lab No.
Sample type
Nitrogen
Carbon
Hydrogen
Sulphur
C/N
Comments
10,20
50,97
na
na
5,00
Whall JD, Trent U.
97-256-010
Adult mysids
97-220-003
Amphipods
6,81
33,20
5,66
0,00
4,88
Pastershank G., U of O/ Biology
97-256-004
Chironomids
8,98
37,23
na
na
4,15
Whall JD, Trent U.
97-256-014
Clam
12,30
48,91
na
na
3,98
Whall JD, Trent U.
97-220-004
Clam muscle
11,26
43,41
6,77
1,10
3,85
Pastershank G., U of O/ Biology
0,05
11,91
0,19
0,00
10,03
37,22
5,91
0,00
3,71
Pastershank G., U of O/ Biology
0,00
0,74
0,09
0,00
N.A.
Bad trace
97-220-005
Clam shell
231,6
3
Pastershank G., U of O/ Biology
97-220-018
Cragon (shrimp)
97-220-020
Diatom
97-220-002
Egg white
11,85
45,83
6,93
1,14
3,87
Pastershank G., U of O/ Biology
97-220-001
Egg yolk
5,41
62,69
9,73
0,00
11,59
Pastershank G., U of O/ Biology
97-220-009
Fish bone
6,43
19,53
3,51
0,00
3,04
Pastershank G., U of O/ Biology
97-220-008
Fish eye
12,90
48,70
7,05
2,13
3,77
Pastershank G., U of O/ Biology
97-220-013
Fish fin
10,01
34,36
5,35
0,00
3,43
Pastershank G., U of O/ Biology
97-220-014
Fish gill
13,28
47,10
7,06
0,00
3,55
Pastershank G., U of O/ Biology
97-220-015
Fish gut content
9,56
44,88
7,07
1,13
4,69
Pastershank G., U of O/ Biology
Filters, we can do that!
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Best are quartz filters; they are stable. However they
are more expensive and offer less choice.
Silver filters are great too.
Mostly glass filters, cheap, huge choice.
How much to use?
Filters, we can do that!
Area = P*R2
In this case, a punch is about 16mm2 and our whole filter
is about 1490mm2 .
Our punch hole is roughly 1% of the filter.
Sediment contamination
Inorganic Carbon
Organic Carbon
Average d13C: 0‰
Average d13C: -25‰
0%
1%
5%
10%
50%
+
+
+
+
+
100%
99%
95%
90%
50%
= Total Carbon
=
=
=
=
=
-25 ‰
-24.75 ‰
-23.75 ‰
-22.50 ‰
-12.5 ‰
Honey, you think I’m fat?
% Nitrogen
100
10
5
2
1
0.1
0.001
Wt required
0.1mg
1.0mg
5mg
7mg
10mg
100mg
Yeah, right!
Optimal amount
of Nitrogen:
0.1mg
Open split, magical stuff
EA 100 ml/min
He + CO2 + N2 + He
2mm or 1/16” SS
line from EA
Fused silica capillary
100 um, 2m, inserted
about 30cm in EA line,
0.4 ml/min going into
source of IRMS
In real life…Open split
EA
Ref
6
Ref
5 Ref
7
Ref 3 Ref 4
Ref 8
He
Ref 9
Ref 10
Ref 1
Ref 11
Ref 12
Ref 2
IRMS
In real life…Open split
EA
Ref
6
Ref
5 Ref
7
Ref 3 Ref 4
Ref 8
He
Ref 9
Ref 10
Ref 1
Ref 11
Ref 12
Ref 2
IRMS
The joy of sniffing EA only
CO2
TCD output from EA
N2
Mass spectrometer output
Mass 44,45,46
Mass 28, 29
Magnet
Peakjump
The joy of sniffing, total
CO2
TCD output from EA
N2
Mass spectrometer
output
Masses 28 & 29
Masses 44, 45 & 46
Mass 44,45,46
Mass 28, 29
Magnet
Peakjump
To dilute or Not to dilute?
Second last suggestion
I strongly recommend that you create a
basic document for your users explaining
the limits and pitfalls of EA-IRMS analysis,
this will save you (and your users) an
enormous amount of time.
Some unresolved issues
with EA
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Removing inorganic carbon is not trivial
Alkalies (Sodium, Potassium, Calcium) are difficult to combust,
catalist is definitively required to bind and help with oxydation.
Oxygen contribution to d34S is still a problem.
Last suggestion and only
Official Endorsement
The only product fully and officially
endorsed by the author is:
Rickard’s Red
Thank you for not snoring
My thanks to:
Wendy Abdi, Nik Binder, Fred Longstaffe, Scott Hughes,
Gilles St-Jean, Peter Stow and Patricia Wickham for the use of
material, brain power and time …