Slide 2 2400 Series 2 CHNS/O Analyser Paul Gabbott PETA Slide 3
Page 2 Slide 4 Organic Elemental Analysis The PE 2400 CHNS/O
Elemental Analyzer is a combustion technique that determines weight
percent carbon, hydrogen, nitrogen, sulfur or oxygen in a variety
of sample types Capable of operating in 3 modes; CHN, CHNS and
Oxygen Page 3 Slide 5 Organic Elemental Analysis The 2400 is an
organic elemental analyser It is designed to analyser organic
materials such as those produced in a chemical laboratory It is not
designed for inorganics eg carbon in steel Nor is it a TOC analyser
(total organic carbon). In some instances the 2400 could act as a
TOC but it is not designed to continuously handle applications such
as TOC in seawater Page 4 Slide 6 How does it work ? Combustion
technique Typically a sample is weighed into a tin capsule and
placed in the autosampler carousel. Information is entered into the
instrument (ID & wt) and the run started. The sample is
combusted into simple gases, CO2, H2O and N2, collected in the
mixing chamber, separated by frontal chromatography and measured by
TC Page 5 Slide 7 2400 Design Schematic Page 6
DetectionSeparationGas Control ZoneCombustion Zone Slide 8
Combustion Process Completely combusting a weighed sample is
critical to obtaining accurate results Page 7 Static and Dynamic 4
steps to combustion Sample introduced into oxygen environment
Additional oxygen introduced Allowed to sit and burn Additional
oxygen introduced Operator programmable Slide 9 CHN Combustion Tube
Slide 10 Combustion Tube Page 9 Ultra high gases and pure quality
reagents are required Oxidizing & Removes interferences
i.e.,halogens and sulfur Aids in the combustion of the sample
Prevents unwanted elements from interfering with the analysis and
keeps the system cleaner Slide 11 CHN Reduction Tube Slide 12
Combustion and Reduction Packing Combustion Tube Silver Vanadate
Silver Tungstate EA-1000 Reduction Tube Copper 60-80 mesh Pack the
Copper as tight as you can Cuprox Copper Plug Leave about inch
space from top of copper plug and the top of the tube Slide 13
Reduction Tube Removes excess oxygen Reduces NO X to Nitrogen
Copper oxide at the end converts any CO to CO 2 Operates at about
640C (the best temp is often debated) Slide 14 Consumables
N241-0680 CHN Combustion Kit 2 Combustion tubes & Chemicals
2000 runs N241-0681 CHN Reduction tube Kit 2 tubes 500 runs total
Consumables are supplied individually or in kits Slide 15 Gas
Control Zone Homogenous mixture of product gases will achieve the
highest precision Page 14 Constant temperature, volume and pressure
maintained in the mixing chamber Environmental conditions such as
changes in barometric pressure do not affect results Achieve
highest precision Separates the combustion area from the separation
area, so we can change the amount of O2 without change in retention
times Mechanical mixing Ensures a homogenous mixture of product
gases Slide 16 Separation Page 15 Frontal Chromatography Steady
State Signal Simple difference calculation determines signal Easier
to calculate a small step change than a small peak Slide 17 Frontal
Chromatography Page 16 Slide 18 Modes of Operation CHN mode is the
most universal of the analysis CHN mode has the best reagent design
and allows use of the Optimize Combustion control parameters.
Interfering elements (halogens and sulphur) are removed. CHNS mode
designed to include sulphur, which reduces universality. This
includes limiting the range of sample types and sample size (1 to 2
mgs recommended). Metal cations are excluded. Special care must be
used in calibration and blanks for lower levels of sulphur. The
Oxygen mode where oxygen in a sample is converted to carbon
monoxide over platinised carbon. This mode excludes compounds
containing phosphorous, fluorine, silicon and metal cations.
Samples containing mineral matter must be demineralised prior to
analysis. Upgradeability The user may choose any or all modes. The
2400 Series II may be freely upgraded at any time to add additional
mode capability to suit the needs of the laboratory. Page 17 Slide
19 Sulphur CHNS is determined in a similar manner to CHN Sulphur
separates after water so gives a step after water This gives a
longer analysis time However the combustion tube is completely
different Slide 20 Sulphur Tube Operating temperature around 975C
Slide 21 Sulphur tube Sulphur burns to SO 3 and SO 2 The SO 3 must
be removed (reduced) immediately because of its reactivity This is
achieved by adding copper to the combustion tube Normal catalysts
are replaced with EA 6000 because they scrub for sulphur Dynamic
combustion conditions are required, and this restricts the use of
the ability to extend combustion time or add extra oxygen CHNS does
not use a separate reduction tube Slide 22 Oxygen Analysis Oxygen
is converted to carbon monoxide over platinised carbon in a helium
gas stream using silver capsules. Helium / hydrogen (approx 5%) gas
stream enhances conversion to CO and allows the use of tin
capsules. Copper is used to convert any CO 2 formed back to CO Acid
gases are scrubbed in a trap installed on the side of the analyser
Slide 23 Oxygen Tubes Slide 24 Trap used with oxygen Slide 25
Oxygen detection Slide 26 Oxygen applications Often involve coals
or fuels Note that coals must be demineralised for which procedures
exist, but it is not as simple. Slide 27 CHNS and O2 CHNS Tubes
Copper EA-6000 Oxygen Tubes Copper Slide 28 Analysis Times Analysis
times CHN: 6 min, CHNS: 8 min, Oxygen: 4 min Sample size 0 to 3 mgs
typically depending on sample type. Small samples will generally be
limited by weighing errors, but may be used. Large samples may be
used if the combustible content is low Analytical Element Range
(mgs) detector range C 0.001 - 3.6 S 0.001 - 2.0 H 0.001 - 1.0 O
0.001 - 2.0 N 0.001 - 6.0 Page 27 Slide 29 Capabilities of EA 2400
Data Manager Collect and store complete run information Search
stored runs Create reports 21 CFR part 11 compliant option audit
trail signature points permissions Complete analyzer history stored
Instrument messages Leak test output Timing events Monitored
components Advanced calculations Statistics Recalculation
capabilities Archive data Page 28 Slide 30 EA 2400 Data Manager
Main Run Window Page 29 Slide 31 Queries Page 30 Specify your
search using AND/OR statements on sample ID date operator project
run type mode Set limits like is contains does not contain starts
with between before after on Slide 32 Advanced calculations and
Statistics Page 31 Advanced calculations provide additional
information on results Statistics can be preformed on a set of runs
Slide 33 Printing reports and exporting data Print Table Report
template Save to a file RTF TXT PDF Export formats Excel CSV Page
32 Slide 34 Diagnostics Page 33 For confidence in instrument
performance and for easy evaluation of instrument history the
operator can send vital information to the database, including
Instrument status temperatures pressures detector signals voltages
Leak test results Parameter settings Purge times Slide 35 21 CFR
part 11 compliance Page 34 Slide 36 EA 2400 CHNS/O Analyzer Unique
technology features and newest most modern Data Manager Software
Page 35 Slide 37 EA 2400 CHNS/O Analyzer Operating the system
Purging the analyser Blanks Conditioners K-Factors Samples Page 36
Slide 38 CHNS and CHN Purge Gases Gases : Helium and O2 @ 99.995 %
N2 or Air for the Pneumatics @ 99.95 to 99.99% Slide 39 Purging
prior to analysis The analyser uses helium as a purge gas and
oxygen as a combustion gas Purge gases contain amounts of carbon,
hydrogen and nitrogen which need to be determined. In addition
contaminants from the atmosphere get into the instrument and gas
lines, particularly overnight and when the system is left unused.
Purging is required to make sure the analyser and gas lines are
free of contamination before starting. The longer the gas lines the
longer the purge times Oxygen is used only as required so the
oxygen lines are more prone to contamination when the system is
unused Page 38 Slide 40 System Purging Helium purge Use as long as
found necessary to purge the analyser Afterwards a series of helium
blanks can be performed to ensure the analyser is free of
contaminants Oxygen Purge Oxygen purging will pass through the
copper tube and can cause a significant loss in lifetime of the
copper Oxygen purging should be kept to a minimum The end of the
combustion tube may be loosened to allow oxygen escape before the
reduction tube. Gas Lines These must be copper or steel and
completely free of leaks. Any leaks will seriously compromise
performance. As a result gas lines must be connected straight to a
cylinder and not used by any other equipment whatsoever. Page 39
Slide 41 Leak tests Leak Tests #1 Mixing Volume #2 Combustion
/Auto-Injector #3 Column/Detector Must pass Leak test 1 Pressure
should get to 760 mm, you will here a click around 730mm. Pressure
will hold for 5 mins @ 760 mm. Test 2 will pressure around 780 to
800 mm, you may get a small drop in pressure +/- 2 mm If this fails
Check for Cracked tubes, Auto-injector o-rings Slide 42 Leak Tests
Leak test 3 adds the detector and column Cap sensing vent Sensing
vent is the peek tubing a yellow heat shirk tubing on it Slide 43
Blanks Blanks consist of running the system without any sample to
determine background levels of contamination. These are then
subtracted from the sample values. Tin (and all other) capsules
contain levels of impurities which must be measured so need to be
included. Full oxygen blanks contain everything except a sample
They use up copper at a high rate so should be kept to a minimum
Helium blanks are run without oxygen or a capsule and are used to
make sure the system is purged, stable and ready to be used. They
do not use up chemicals so can be used freely. Page 42 Slide 44
Conditioners Blanks decondition the system by removing adsorbed
water from internal surfaces A series of blanks will therefore
continuously reduce the hydrogen background value Any sample run
afterwards will show lower levels of hydrogen than it should
because some of the water will be used to re-establish the adsorbed
water equilibrium. As a result a conditioner must be run after a
blank. Normally this is a sample of the reference standard It does
not have to be weighed because no use will be made of the result,
but normally this is good practice to make sure a sensible amount
is used, (eg 2mg similar to a sample) Page 43 Slide 45 Blank Values
Blank values are determined from a running average of three blanks
interspersed with conditioners. The system automatically averages
the results unless blanks are run sequentially The manual makes the
following comments Slide 46 K Factors K Factors are the calibration
factors determined for each element by running known standards. The
step height of the signal for each element is measured in
microvolts per microgram (or whatever units the software uses) of
element present. Sample response divided by the K Factor allows the
amount of each element to be determined. This is converted to a
weight percent when the weight is known. Page 45 Slide 47 K Factors
K factors are determined from the running average of three or more
values. Typical values as given by the manual are shown below.
Slide 48 K-factors K-Factors should be run periodically to account
for any drift or instability in the system. Standards used Should
be appropriate to the samples being run Eg if a 5% nitrogen
standard is run with a 50% sample any error will be magnified 10
times Different standards can be used for different elements if
required. Page 47 Slide 49 Typical Sart-up Sequence Check Leak
tests 5 Helium blanks Conditioner Blank Conditioner Blank
Conditioner Blank Conditioner 3 K-Factors Samples Page 48 Slide 50
Samples Solid samples are encapsulated in tin foil capsules which
are folded manually using a pair of tweezers Care must be taken not
to tare the foil or lose sample in this process This is one of the
most important and time consuming aspects of analysis Page 49 Slide
51 Weighing Samples Samples need to be weighed to at least six
figures (microgram) level weighing accuracy of a 1mg sample weighed
to 6 figures is +/- 0.1% weighing accuracy of a 1mg sample weighed
to 5 figures is +/- 1% Slide 52 Weight range specification Total
weight of each element must not exceed the analytical range below
Slide 53 Homogeneity Since samples are small they must be
representative of the material they are from Inhomogeneous samples
should be ground and a small amount of the resulting fines taken
Potentially Inhomogeneous samples include Polymers and Composites
Coals and minerals Solis and biological materials Page 52 Slide 54
Liquid Samples Volatile free flowing liquids can be syringed into
small aluminium capsules (which contain around 2mg material)
sealed, and weighed. These are then inserted into tin capsules
since tin aids the combustion Non volatile liquids can be inserted
into thicker walled tin capsules. It is always good to minimise the
amount of aluminium put into the combustion tubes it can wet quartz
and cause the tube to crack Viscous volatile liquids use volatile
aluminium pans more frequently associated with DSC Page 53 Slide 55
Liquid samples If a lot of aluminium is used then the quartz tube
may need to be protected. This can be done using zirconia cloth, or
a sacrificial quartz inner tube. Do not cool the furnaces overnight
and replace the vial receptacle more frequently Slide 56 Handling
Samples N241-1255Standard tin capsules. For solids and viscous,
non-volatile liquids N241-1362Large tin capsules. For larger sample
weights of solids with inert material(soil, silica beads) and lower
carbon. N241-0320Volatile tin pans and covers. Requires sealer,
0219-0061. For volatile viscous liquids i.e. urea formaldehyde.
0240-06424 l aluminum capsules. Requires sealer B019-8093. For
volatile, non- viscous liquids i.e. gasoline. 0009-0709 30
microliter aluminum capsules. Requires sealer B019-8093. For
volatile, slightly viscous liquids. N241-1363Tin disks. For
particulate material collected on a glass filter. N241-xxxxThick
walled tin capsules for liquids Slide 57 Accuracy Specifications
Slide 58 Optimise Combustion Slide 59 For most CHN work the
extended combustion time can be set to 10 20 seconds Increased
oxygen usage should be avoided if not needed since it reduces the
life of the copper tube. Slide 60 High carbon containing samples
POLYNUCLEAR AROMATICS These are quite demanding materials due to
high Carbon content and difficult to burn structure. Typically
limit max sample size to about 2.5mg, add extra combustion time and
extra oxygen if incomplete combustion is found. Slide 61 Incomplete
combustion Quite rare but may occur with very high carbon
containing materials or if the combustion tube needs to be changed
How is this evident Increasing carbon background (blank) Production
of methane (shows as a high nitrogen / low carbon result) Remove
residue by running some oxygen blanks or Purge with oxygen to burn
any remaining carbon Extend combustion time and amount of available
oxygen for future runs or reduce sample weight. Slide 62 High
carbon containing samples Carbon Fibre Increase combustion furnace
to 980C Max weight around 2mg Slide 63 Low combustible (carbon)
content SOILS Soils work well on the 2400 because higher wts can be
used and the furnace conditions can be optimised to burn them.
Samples should be well dried first. I typically work with approx
20mg samples thought weights can be higher if required, add 20
seconds to combustion and add a second to oxyfill and oxyboost1
Slide 64 Coal Actually it does not burn easily Needs time and
available oxygen, but 20 secs extended combustion and typically 2
secs extra oxygen are sufficient Homogeneity is always an issue and
how well it is ground Moisture content is another, usually it is
analysed after drying Usually analysed for its calorific content
which is calculated from its elemental composition Slide 65
Particulate matter in water or air This is an increasingly common
requirement Applications include air quality exhaust emissions
Plankton in seawater Material is collected on filter discs which
can be analysed completely in the 2400 Slide 66 Rolling up a glass
fibre filter disk Slide 67 Filters Use a sacrificial quartz liner
Do not drop furnace temps in case of wetting Extend combustion
times Calculate C/N ratios Slide 68 Silicon containing compounds
May form a stable silane or the extremely stable silicon carbide.
The general approach to analysis of this type of material is to add
vanadium pentoxide to the capsule if required. Tin also promotes
combustion of this type of material, one reason for using it. Slide
69 Refractory carbides Slide 70 Organometallic compounds As with
silicon containing compounds these are susceptible to the formation
of stable carbides, eg boron carbide which is a stable glass. The
tin capsule acts as a combustion aid but if difficulties emerge
then vanadium pentoxide should be added to the capsule. Slide 71
Mercury containing complexes If mercury compounds are in use then
as a precaution add pelleted gold to the combustion tube to trap
any potentially volatile mercury produced REPLACE TUBE AFTER THE
ANALYSIS HAS FINISHED Use a similar approach with other potentially
hazardous metal complexes most will produce stable oxides The tube
catalysts and the copper tube are actually very good at scrubbing
for these products It is therefore good practice to replace the
combustion tube regularly before any unwanted elements pass through
the system Slide 72 Varying H content The equilibration effect of
water during blanks has already been noted It also has an effect as
samples are run High H followed by low H will result in a higher
value for the low H material than it should have. Low H followed by
high H will result in a low value for the latter material All
results are should still be within specification but these effects
are easily noticeable. Slide 73 Effect of a hydrate Water content
has a significant effect on results as shown in this example of a
hydrate. Solvates also have a significant effect. Slide 74 Effect
of Solvate / Hydrate Calculations exist that allow the operator to
fit the data to a known solvate. However the material may not be
fully solvated which causes difficulties Slide 75 Effect of
moisture It is no surprise that moisture has a similar effect If a
sample is not dry then accurate CHN data is difficult It can be
back calculated but again this is not ideal Impure (wet) samples
give inaccurate results Slide 76 Sulphur CHNS determination works
but the system is not as optimised as for CHN Additionally the
separation of water and sulphur is not complete This makes
determination of low levels of sulphur difficult unless the water
is removed using an in-line trap. Slide 77 Final practical comments
Slide 78 Drying the catalysts The EA 1000 and silver tungstate on
magnesium oxide are best dried before use. Use a muffle furnace at
900C for 30 minutes, longer at lower temps Store in a dessicator
Damp material leads to high hydrogen blanks that drift down and the
water evolved can also promote devitrification of the quartz Slide
79 Diagnostics-Signal Timing Signal Timing Make sure signals are
properly timed Slide 80 Filter Disks Install Filter disks on both
sides of the cross- over and at the top of the Reduction tube This
will help in keeping the cross-over and the parts after the
reduction tube clean Place filters on both side of the cross-over
and the top of the reduction tube Slide 81 CHN Reduction Tube
Copper reduction tube with support for filling If not properly
filled this is the main cause of drift in an analyser Wire form
copper is easier to pack but is less efficient Copper powder gives
the longest life but often settles in use
