Sample preparation in elemental analysis - drying, grinding, weighing, wrapping...

Sample preparation in elemental analysis
- drying, grinding, weighing, wrapping,… -
August, 27th 2015
Dr. Marc Ruppenthal
Product Manager Elemental Analysis
Webinar

Your host
• Dr. Marc Ruppenthal
• Product Manager Elemental Analysis
• Responsible for vario MICRO cube, vario EL cube, rapid
OXY cube and EA-IRMS interface analyzers
• PhD in geoecology, studied hydrogen isotope ratios in soil
organic matter
• Joined Elementar in 2014
28/08/2015 Sample preparation in elemental analysis - webinar - 2

Agenda
About ElementarGroup1
The importance of sample preparation2
Sample handling3
Summary4

The elementargroup – about us
• The technology leader in
• Elemental Analysis (EA)
• Isotope Ratio Mass Spectrometry (IRMS)
• Offers an unmatched combination of
• innovative technologies,
• tailor-made solutions and
• comprehensive support.

The elementargroup – the subsidiaries
Elementar Americas
Elementar Headquarters
Elementar France
Isoprime Ltd.
Elementar Italia
Elementar Trading (Shanghai)
Elementar Australia

The elementargroup – the distribution network
Represented in all relevant world markets by our own sales
organisation and a network of well-chosen distributors

The elementargroup history
was founded
1851
Dennstedt patent "über die vereinfachte
Elementaranalytik" was the basis for the
1st instrument generation
1904
The first elemental analyzer for
simultaneous detection of carbon, hydrogen
and nitrogen was invented.
1932
The first Dumas Nitrogen/Protein
analyzer was introduced
1964
The EA business of Heraeus was sold in
a management buyout and restructured
under the brand name Elementar.
1995
The High temperature TOC analyzer
was introduced
1973
The first fully automatic elemental analyzer
with TCD detection was introduced
1980

Introduction of the "cube" platform
vario MICRO cube, vario EL cube,
vario MACRO cube, rapid N cube
2006
vario TOC cube
2008
rapid CS cube, vario ISOTOPE cube,
vario PYRO cube
2009
rapid N exceed, rapid OXY cube
2014
trace SN cube
2010
vario MAX cube, iso TOC cube
2012
Isoprime Ltd was acquired

Introduction of the inductar series
inductar CS cube, inductar ONH cube,
inductar EL cube
2015
rapid MAX N exceed, rapid MiCRO N cube

The elementargroup – key markets
AgricultureChemicals EnvironmentalEnergy MaterialsForensics

Tailor-Made to Customer Needs
• Elemental analyzer optimized for different analytical tasks
• vario Series - Industry-leading versatility in elemental analysis
• rapid Series - Dedicated instruments serving today’s customer needs
• trace Series - Trace-level detection of elements
• TOC Series - Fast and easy determination of total organic carbon
• inductar Series – Dedicated instruments for the analysis of metals and inorganics

Some of our customers

Agenda
Sample homogeneity2.1
Sample drying2.2
Sample wrapping2.3
Sample handling3
Summary4

Sample preparation and handling is essential
for your analytical results
• Does the sample have acceptable homogeneity?
• Is drying necessary?
• Is sample wrapping necessary?
• Are additives necessary or recommended?
• What is the right sample weight?

Elementar can help you answering these questions!

Agenda
Sample drying2.2
Sample wrapping2.3
Sample handling3
Summary4

Homogeneity
• A homogeneous substance is defined as a
substance of uniform structure or composition
throughout the entire sample matrix.
• In most substances there is a relationship
between homogeneity and sample amount.

The relationship of homogeneity and sample amount
• The larger the sample amount, the higher the
homogeneity
•  i.e., the bigger the chance that the analyzed
sample is representative for the entire substance
Sample amount
Sample homogeneity

How to guarantee sufficient homogeneity?
• 1) Through sample preparation…
• There are many effective ways to grind
samples including the use of a planetary ball
mill, Wiley mill, freezer mill, roller grinder, or
the standard mortar and pestle.

How to guarantee sufficient homogeneity?
• …followed by analysis in a Micro or Semi-
Macro elemental analyzer, e.g., vario EL cube
• ! Microbalance necessary !
• OR 

Simplified Sample Preparation
– with vario MAX cube or rapid MAX N exceed
• No grinding or milling
• Large capacity crucibles for large sample amount
• Broad sample weight range
• Up to 5 g / 5 ml sample
• Up to 500 mg total carbon and 330 mg total nitrogen
• Highest sample flexibility
• Inhomogeneous samples
• Samples with high ash content
Weigh in the crude samples
into reusable crucibles
Place them on the
autosampler
Start the sequence
Get the results!

vario MAX cube and rapid MAX N exceed
– Automatic Ash Removal Technology
• Reusable stainless steel crucibles
• Robotic arm inserts the sample automatically and
removes the crucible including the ash after the
analysis

vario MAX cube and rapid MAX N exceed
– Area of Application
• Address any high throughput laboratory
• Designed for 24/7 operation
• Available in N mode (rapid MAX N exceed)
or CN and CNS Mode (vario MAX cube)

Agenda
Sample drying2.2
Sample wrapping2.3
Sample handling3
Summary4

Moisture in elemental analysis
• Environmental substances can contain water in
the forms of
• Absorbed moisture (e.g., coal)
• Structural water (e.g., silicate minerals)H2O
H2O
H2O
H2O
H2O
H2O

Moisture effects in elemental analysis
• Moisture increases hydrogen and oxygen
concentration of a sample
• Moisture decreases all other element
concentrations (C,N,S,…), because the elemental
analysis result is based on the too high moist
weight of the sample, instead of the dry weight.
H2O
H2O
H2O
H2O
H2O
H2O

How to get rid of moisture?
1. Sample drying in a laboratory oven with
subsequent cooling in a dessicator
2. Sample drying directly on the Elementar heated
sample carousel prior to the analysis
3. Sample drying in a laboratory oven with
subsequent cooling in a dessicator and loading
on the Elementar heated sample carousel to
avoid reabsorption of moisture
H2O
H2O
H2O
H2O
H2O
H2O

How to correct for the effect of moisture?
1) Determine moisture content
MCdb = (Wi-Wf / Wf) * 100
• MCdb = Moisture content dry basis [%]
• Wi = Initial weight
• Wf = Final weight after drying (e.g., 105 °C)
 2) Use Elementar Software to automatically
correct your results for moisture content

Humidity correction through the software

Agenda
Sample drying2.2
Sample wrapping2.3
Sample handling3
Summary4

Foils, boats and capsules in different materials for
different purposes
• Tin  Exothermic oxidation of tin locally increases the
combustion temperature to ~ 1800 °C, supporting
the combustion
• Aluminum No exothermic reaction of aluminum inside the
combustion furnace  material suited for analysis of
explosives
• Silver  Absorbs halogens, recommended for samples with
very high halogen content
• Nitrogen-free paper  Cost-saving alternative to tin in
N/Protein analysis

Sample wrapping

Trusted quality
• All Elementar consumables are designed to meet
the highest quality standards and reliability
• They are certified and validated in accordance
with international norms and standards
• Elementar applies the tightest international
regulations governing quality control and product
safety

Agenda
Sample handling3
Additives for better results and increased lifetime3.1
Weighing3.2
Accessories for saving you time and money3.3
Summary4

Sample preparation and handling is essential
for your analytical results
• Does the sample have acceptable homogenity?
• Sample wrapping necessary?

Elementar can help you answering these questions!

Agenda
Sample handling3
Weighing3.2
Summary4

Additives to improve results and instrument lifetime
• Addition of WO3?
 for S analysis of soils, sulfates (3:1),
 for adsorption of alkali ions (1:1)
 not necessary for pure organic compounds
• Addition of polyethylene foil?
 for conditioning the pyrolysis reactor for O analysis using the oxygen option
 not necessary for rapid OXY cube

Additives to improve results and instrument lifetime
• Elementar Fluorine kit
Flourine containing samples devitrify the quartz glass in CHNS/CNS/S modes, attack the SO2
purge & trap column, and can create dummy peaks of C or S
4HF + SiO2  2H2O + SiF4 (destroys quartz glass!)
 Solution: Use Elementar F-kit!  Addition of MgO and utilization of ceramic items
MgO + 2HF  MgF2 + H2O

Agenda
Sample handling3
Weighing3.2
Summary4

Weighing is critical!

Weighing is critical!
• Please make sure that you use a good balance.
Balance and elemental analyzer form a system.
If the weighing is not done carefully, the analysis
will be wrong. Even with the best elemental
analyzer on earth!

Weighing - influencing factors -
Weighing bench
• Stable (lab bench, lab table, stone bench).
• Your weighing bench should not sag when work
is carried out on it and
• Should transfer as few vibrations as possible
• Antimagnetic (no steel plate)
• Protected against electrostatic charges (no
plastic or glass)
• Reserved for the balance

Work room
• Should be as vibration-free as possible
• Corners are the most vibration-free areas of a
building

• Positioning of the weight
(„corner load“)
• Always place samples in the
center of the weighing pan

Gravitation
• The weighing values are different when the
weighing height changes.
 Level and adjust the balance whenever it is
moved !

Temperature
• Direct influence through temperature
dependent drift of the balance
• Indirect influence when there is a
temperature gradient between the
weighing sample and the surroundings,
producing air currents along the
weighing vessel
• Condensation of ambient humidity on
the surface of the vessel

Humidity
• Balances should never be operated
above or below the measuring range of
20 to 80 % relative humidity
Light
• If possible, place the balance on a
window-free wall. Direct sunlight (heat)
will influence the weighing result.
x

Moisture gain / evaporation
• Volatile or hygroscopic
substances can cause drift of
the balance (through
evaporation of the sample or
uptake of ambient humidity)

Magnetism
• Magnetic and magnetically permeable
objects exert a mutual attraction. The
additional forces that arise are wrongly
interpreted as a load by the balance.

Electrostatic charge
• Materials with low electrical conductivity such as glass, plastics,
powder or granulates can only very slowly (over hours) drain
away electrostatic charges
• The charging occurs primarily through stirring or rubbing
during the handling or transport of containers or materials
• Dry air with less than 40 % relative humidity increases the risk
of this effect
 Antistatic kits provided by balance manufacturers are a
possible remedy

Air circulation
• Do not place the balance in the
air flow of devices with
ventilators, such as computers
or large laboratory devices
• Do not place the balance next
to a door
• Passersby will usually create a
draft at the weighing location

What is the right sample weight?
Capacity of the
purge & trap column
Sample homogeneity
• Low sample homogeneity requires that larger sample
amounts are analyzed
•  Larger sample amounts in turn produce more
combustion gases and thus require larger capacities for
the purge & trap columns

• Ideal sample weight therefore depends on a
combination of the type of samples you are
analyzing and the type of elemental analyzer you
are using
• Note: Aggresive samples (high halogen or salt
content) should be analyzed with the lowest
possible weight to increase lifetime of both
consumables and instrument

• Ideal sample weight therefore depends on the interplay of the
type of samples you are analyzing and the type of elemental
analyzer (and type of balance) you are using !
• Note: Aggressive samples (high halogen or salt content) should be
analyzed with the lowest possible weight to increase lifetime of both
consumables and instrument
• Of course you will always have to operate above the detection limit of the
elemental analyzer

Agenda
Sample handling3
Weighing3.2
Summary4

Capsule sealing press for liquid or volatile samples
• For gas-tight sealing of samples inside capsules
• Possibility to connect an inert gas for sealing
under protective atmosphere

Manual pressing tool to form sample pellets
• For fast packing of the sample and
elimination of ambient air through
sample compaction

Solid sample former
• For fast packing of the sample and
even better elimination of ambient air
through better sample compaction

Vario Liquid Sampler (VLS)
• For fast analysis of liquids without the
necessity to seal liquids in a capsule
• Large injection range
• Random access to any of the 50 sample
positions including priority sampling
function
• For all cube models (except models from
the vario MAX and rapid N families)

Agenda
Sample handling3
Summary4

Summary
• Does the sample have acceptable homogenity?
• Sample wrapping necessary?

Summary
• The quality of your elemental analysis is not only
determined by your elemental analyzer!
• Ask yourself the following questions when setting up a new
laboratory procedure:
• Is sample homogeneity sufficient?
• Could moisture have a substantial effect?
• Is sample wrapping necessary?
• Are additives recommended?
• Is the weighing carried out properly?
• Could my work be facilitated by accessories?
• Elementar can help! Please feel invited to contact us
at info@elementar.de

Elementar thanks
for your attention !

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