Advanced Sample PreparationTechniques
G. KnappGraz University of Technology October 2004 1
Günter KnappInstitute for Analytical Chemistry and Radiochemistry
Graz University of TechnologyAustria
High Performance Sample Digestion
G. KnappGraz University of Technology October 2004 2
•Losses of elements ?•Contamination ?•Interferences with residual organic compounds ?
• Wet digestion– in closed pressurized vessels– in open pressurized vessel– with microwave boosted UV-lamps
• Combustion
Nitric Acid –Optimum Reagent for Wet Digestion
G. KnappGraz University of Technology October 2004 3
• Ultra pure after subboiling distillation
• Little interferences with subsequent measurement methods– Atomic absorption– ICP – OES– ICP – MS
Subboiling Distillation Apparatus
G. KnappGraz University of Technology October 2004 4
Teflon IR heated subboilingstill in class-100 clean air hoodwith leveling reservoirconstructed from modular Teflon PFA segments.
PFA Labware Catalog; Savillex Corp.: Minnetonka, MN, 1995
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G. KnappGraz University of Technology October 2004 5
Oxidation Efficiency ofPressure Decomposition with HNO3 (65%)
Ref.: P. Fecher, CLUA Erlangen, Germany
02468
1012
150 °C 200 °C 250 °C 300 °C
30%% C
Milk PowderCitrus LeavesFish TissueBovine LiverMargarine
G. KnappGraz University of Technology October 2004 6
Pine Needles Milk Powder Bovine Liver Polyethylene Crude Oil0
5
10
15
20
25
Pine Needles Milk Powder Bovine Liver Polyethylene Crude Oil
LP-Microwave HP-Microwave HPA-S
% C > 30 % , not mineralized X X
Oxidation Efficiency –Comparison of Commercial Equipments
G. KnappGraz University of Technology October 2004 7
High Temperature Wet Digestion (320°C)High Pressure Asher HPA-S
HPA-SAnton Paar, Graz, Austria; www.anton-paar.com/ap/
G. KnappGraz University of Technology October 2004 8
Wet Digestion at High TemperaturePressurized Digestion in Closed Vessels
Tem
pera
ture
[°C
]
240
220
200
180
160
140
Res
idua
l Car
bon
Con
tent
[%]
2,5
2,0
1,5
1,0
0,5
0,2 0,4 0,6 0,8 1,0 1,2Sample Weight [g]
Temp TOC
ptotal = pCO2 + pHNO3 + pNOx
pHNO3 ≈ T pCO2 ≈ sample weight &
vessel volumepmax depends on the
digestion system
Resultincreasing sample weightdecreasing digestion temperatureincreasing organic residue
G. KnappGraz University of Technology October 2004 9
Design of Pressure Vesselsfor Microwave Assisted Wet Digestion
SCREW FASTENED LID SPRING FASTENED LID PISTON TYPE LID
Coolingair
Stopper withrupture discand sealing
Screw cap
Digestionvessel
Vesseljacket
Screw
Spring
Adapterplate
Lid
Liner
Jacket
Rotor
Vent stem
Rupturedisc
Lid
Screw cap
Liner
Jacket
Cooling air
Simultaneous Pressure Measurement
G. KnappGraz University of Technology October 2004 10
M. Zischka, P. Kettisch, A. Schalk, G. Knapp; Fresenius J. Anal. Chem. 361 (1998) 90
decompositionvessel
vessel jacket
screw cap
lid
cooling air
cooling air
cooling airpiston
G. KnappGraz University of Technology October 2004 11
Simultaneous Pressure MeasurementRotor-System
M. Zischka, P. Kettisch, A. Schalk, G. Knapp; Fresenius J. Anal. Chem. 361 (1998) 90
1
2
3
45
67
8
9 9
1 pressure vessel2 vessel jacket3 piston type lid4 piston5 hydraulic fluid6 pressure transducer7 IR pressure signal8 Cooling air9 IR temperature signal
G. KnappGraz University of Technology October 2004 12
Simultaneous Pressure MeasurementRotor MULTIWAVE 3000Anton Paar, Graz, Austria; www.anton-paar.com/ap/
G. KnappGraz University of Technology October 2004 13
Simultaneous Pressure MeasurementMULTIWAVE 3000
Anton Paar, Graz, Austria; www.anton-paar.com/ap/
G. KnappGraz University of Technology October 2004 14
Multiwave 3000High Performance Sample Decomposition
Digestion of 0,3 g polyethylenewith 5 ml conc. nitric acidin a 80 ml quartz vesselat 250°C and 80 bar
G. KnappGraz University of Technology October 2004 15
G. KnappGraz University of Technology October 2004 16
Multiwave 3000High Safety Standards
Explosion of an overloaded vesselDigestion of 0.5 g polypropylenewith 5 ml conc. nitric acidin a 80 ml quartz vesselat 250°C and 80 bar
G. KnappGraz University of Technology October 2004 17
G. KnappGraz University of Technology October 2004 18
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
Advantage•Quasi infinite vessel volume
•Maximum possible temperature depends
only from applied pressure
•Simple digestion vessels
G. KnappGraz University of Technology October 2004 19
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
HPA-S®
(Anton Paar Comp., Graz, Austria)
1 Autoclave2 Lid of the autoclave3 Ring retainer4 Rupture disc5 PTFE liner6 Heating element7 Thermocouple8 Water bath9 Quartz vessel
10 PFA vessel11 PTFE lid for digestion vessel12 Vessel rack made of titanium
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B. Maichin, M. Zischka, G. Knapp; Pressurized Wet Digestion in Open Vessels, J. Anal. Bioanal. Chem. 2003 in press
G. KnappGraz University of Technology October 2004 20
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
HPA-S
G. KnappGraz University of Technology October 2004 21
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
Quatz Vessels50 mL
PFA Vessels25 mL
AutosamplerCups (PFA)
1.5 mL
Sampleamount 1.0 g 0.5 g 50 mg
Digestionmixture
5.0 mL HNO3 +0.2 mL HCl
5.0 mL HNO3 +0.2 mL HCl
0.2 mL HNO3 +0.5 mL H2O +0.2 mL H2O2
G. KnappGraz University of Technology October 2004 22
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
• Digested Materials:• Cocoa, pumkin seeds, lubrication oil, polyethylene, polypropylene,
bovine liver, sunflower oil,
• Digestion program• Linear temperature ramp up to 250°C (270°C) within 90 min.• Hold 250°C (270°C) 30 min. ( 270°C - temperature for quartz vessels)• Cooling time 30 min.
• Residual carbon content• 0.2 – 2.0 %
G. KnappGraz University of Technology October 2004 23
Wet Digestion at High TemperaturePressurized Digestion in Open Vessels
UltraClave(Milestone)
UV – Assisted Wet Digestion
G. KnappGraz University of Technology October 2004 24
M. Kolb, P. Rach, J. Schäfer, A. Wild; Fresenius J. Anal. Chem. 342 (1992) 341G. Schwedt, J. Petri; Labor Praxis (1992) 1223
• Advantages– Very low acid concentration– Low blank levels
• Disadvantages– Long digestion time– Only for aqueous samples with low organic content
UV – Assisted Wet Digestion
G. KnappGraz University of Technology October 2004 25
Quartz Vessel
Digestion Solution
UV - Lamp
Principle of the digestionapparatus.
Very low concentrationof HNO3 and H2O2
G. KnappGraz University of Technology October 2004 26
Microwave Assisted High TemperatureUV – Sample Digestion
Dieter Florian, Günter Knapp; Anal. Chem. 2001, 73, 1515-1520G. Knapp, US Pat. 6,210,538 B1; Apr. 2001
Microwaves as energy sourcefor simultaneous heating of the reaction mixtureand for generation of UV radiation.
G. KnappGraz University of Technology October 2004 27
Microwave Boosted UV-Reactorfor Photochemical Reactions
at High Temperatures
Microwave Assisted UV Digestionof Organic Substances at High Temperatures
G. KnappGraz University of Technology October 2004 28
Advantages of Microwave AssistedUV Digestion at High Temperatures
G. KnappGraz University of Technology October 2004 29
• Acceleration of the degradation process owing to high reaction temperature (250 – 280 °C)
• Best efficiency of generated UV-radiation (immersion system)
• Enhancement of reactivity due to simultaneous microwave and UV-irradiation
• Closed system and therefore low risk of systematic errors
Microwave Assisted UV Digestion –Procedure
G. KnappGraz University of Technology October 2004 30
Equipment for high pressure microwave digestion:Multiwave 3000 (Anton Paar Comp. / Perkin Elmer)80 mL quartz vessel
MWL: Low pressure Cd-discharge lamp (Anton Paar Comp.)
Sample materials:Phenylalanine, glycine, wheat flour, bovine liver
Procedure:50 – 100 mg sample + 7 mL H2O + 1 mL H2O2 + 0.05 mL HNO3vessel pressurized with 10 bar oxygen30 Min. at 80 bar (about 250°C)
Microwave Assisted UV Digestion –Results
G. KnappGraz University of Technology October 2004 31
Comparison of sample digestion with and without MWL
Sample material Sample weight Residual carbon[mg] [%]
with lamp without lamp
Phenylalanine 50 1,9 12,3
Glycine 50 0,9 19,5
Bovine liver 100 8,2 24,6
Wheat flour 100 0,9 5,3
Combustion Systems
G. KnappGraz University of Technology October 2004 32
Combustion of organic samples in closed systemsis state of the art for the determination
of volatile nonmetals.
Combustion Systems –Oxygen Bomb
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a) Steel bombb) Lid with valvec) Electrodesd) Ignition wiree) Sample holder
Combustion Systems –Oxygen Bomb
G. KnappGraz University of Technology October 2004 34
• 500 mL steel combustion bomb from Parr Instr. USA.• About 0.5 g sample material is pressed into a tablet, which is placed in a cup made of
porcelain, platinum or silica.• The bomb is filled with 25 – 50 mL of absorption solution.• The bomb is closed with the lid and filled with oxygen to the required pressure
of 25 – 40 bar.• The sample is ignited electrically by means of an iron wire.• Time for absorption (the bomb must be shaken every 15 min.):
Cl-, Br-, J-, SO42- 1 hourF- 3 hours
• Absorption solution:Cl-, F- ion chromatography eluent (CO32- / HCO3-)Br-, J-, SO42- ion chromatography eluent (CO32- / HCO3-)
or diluted NaOH + 3 drops 30% H2O2
Combustion Systems –Microwave Assisted Sample Combustion
G. KnappGraz University of Technology October 2004 35
E.M. Flores, J.N. Paniz, J.S. Barin, J.A. Medeiros; Pat. Pen.
Combustion Systems –Microwave Assisted Sample Combustion
G. KnappGraz University of Technology October 2004 36
decompositionvessel
vessel jacket
screw cap
stopperwith rupture discand sealing
cooling air
cooling air
cooling air
sample
sample holder
• MULTIWAVE 3000• 80 mL quartz vessels• 0.3-0.4 g sample depending on the
organic material• Loaded with 20 bar oxygen• Ignited with microwave power
by means of impregnated filter paper• 8 combustions simultaneously• Absorption solution mobile phase
from ion chromatography• Absorption time 1 hour• IC for Cl-, Br-, I- and S (sulfate)• Ion selective electrode for F-
Microwave Assisted Sample CombustionResults
G. KnappGraz University of Technology October 2004 37
Cl S
certified measured certified measured
BCR 60Aquatic plant
10g / kg
9.3 ± 0.8g / kg
5.2g / kg
5.0 ± 0.4g / kg
BCR 61Aquatic plant
2.3g / kg
2.3 ± 0.3g / kg
2.3g / kg
2.1 ± 0.3g / kg
BCR 63Milk powder
9.94 ± 0,3g / kg
10.1 ± 1.0g / kg
BCR 100Peach leaves
1.49 ± 0.06g / kg
1.55 ± 0.1g / kg
2.69 ± 0.04g / kg
2.7 ± 0.1g / kg
BCR 186Pig kidney
9.4g / kg
9.5 ± 0.5g / kg
Microwave Assisted Sample CombustionDemonstration
G. KnappGraz University of Technology October 2004 38
• Combustion of 0.4 g Milkpowder
• MULTIWAVE 3000
• 80 mL Quartz vessel
• Loaded with 20 bar oxygen
G. KnappGraz University of Technology October 2004 39
Trends inSample Preparation
2006
G. KnappGraz University of Technology October 2004 40
July 02th – 05th, 2006Seggau-Castle / StyriaAUSTRIA
www.analytchem.TUGraz.at/acmr/en/events/2004
Trends inSample Preparation
2006
G. KnappGraz University of Technology October 2004 41
July 2th – 5th, 2006Seggau-Castle / Austriahttp://www.analytchem.tugraz.at/acmr/en/events/
Topics:
•Inorganic analysis:drying; homogenization; wet digestion; combustion; fusion; etc.
•Organic analysis:extraction; derivatization; etc.
•Speciation analysis:extraction; derivatization; etc.
•Microwave techniques for sample preparation;