Advanced Sample Preparation Techniques

Transcription

1 Advanced Sample Preparation Techniques Günter Knapp Institute for Analytical Chemistry and Radiochemistry Graz University of Technology Austria Graz University of Technology October

2 High Performance Sample Digestion 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 Graz University of Technology October

3 Nitric Acid Optimum Reagent for Wet Digestion Ultra pure after subboiling distillation Little interferences with subsequent measurement methods Atomic absorption ICP OES ICP MS Graz University of Technology October

4 Subboiling Distillation Apparatus Teflon IR heated subboiling still in class-100 clean air hood with leveling reservoir constructed from modular Teflon PFA segments. PFA Labware Catalog; Savillex Corp.: Minnetonka, MN, 1995 Graz University of Technology October

5 Oxidation Efficiency of Pressure Decomposition with HNO 3 (65%) Ref.: P. Fecher, CLUA Erlangen, Germany % C % Milk Powder Citrus Leaves Fish Tissue Bovine Liver Margarine 150 C 200 C 250 C 300 C Graz University of Technology October

6 Oxidation Efficiency Comparison of Commercial Equipments % C 25 > 30 %, not mineralized X X Pine Needles Milk Powder Bovine Liver Polyethylene Crude Oil LP-Microwave HP-Microwave HPA-S Graz University of Technology October

7 High Temperature Wet Digestion (320 C) High Pressure Asher HPA-S Anton Paar, Graz, Austria; HPA-S Graz University of Technology October

8 Temperature [ C] Residual Carbon Content [%] Wet Digestion at High Temperature Pressurized Digestion in Closed Vessels 240 p total = p CO2 + p HNO3 + p NOx p HNO3 T p CO2 sample weight & vessel volume p max depends on the digestion system Result increasing sample weight decreasing digestion temperature increasing organic residue Temp TOC 0,2 0,4 0,6 0,8 1,0 1,2 Sample Weight [g] 2,5 2,0 1,5 1,0 0,5 Graz University of Technology October

9 Design of Pressure Vessels for Microwave Assisted Wet Digestion SCREW FASTENED LID SPRING FASTENED LID PISTON TYPE LID Vent stem Rupture disc Lid Screw cap Liner Jacket Screw Spring Adapter plate Lid Liner Jacket Rotor Cooling air Stopper with rupture disc and sealing Screw cap Digestion vessel Vessel jacket Cooling air Graz University of Technology October

10 Simultaneous Pressure Measurement M. Zischka, P. Kettisch, A. Schalk, ; Fresenius J. Anal. Chem. 361 (1998) 90 cooling air piston cooling air lid screw cap decomposition vessel vessel jacket cooling air Graz University of Technology October

11 Simultaneous Pressure Measurement Rotor-System pressure vessel 2 vessel jacket 3 piston type lid 4 piston 5 hydraulic fluid 6 pressure transducer 7 IR pressure signal 8 Cooling air 9 IR temperature signal M. Zischka, P. Kettisch, A. Schalk, ; Fresenius J. Anal. Chem. 361 (1998) 90 Graz University of Technology October

12 Simultaneous Pressure Measurement Rotor MULTIWAVE 3000 Anton Paar, Graz, Austria; Graz University of Technology October

13 Simultaneous Pressure Measurement MULTIWAVE 3000 Anton Paar, Graz, Austria; Graz University of Technology October

14 Multiwave 3000 High Performance Sample Decomposition Digestion of 0,3 g polyethylene with 5 ml conc. nitric acid in a 80 ml quartz vessel at 250 C and 80 bar Graz University of Technology October

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16 Multiwave 3000 High Safety Standards Explosion of an overloaded vessel Digestion of 0.5 g polypropylene with 5 ml conc. nitric acid in a 80 ml quartz vessel at 250 C and 80 bar Graz University of Technology October

17 Graz University of Technology October

18 Wet Digestion at High Temperature Pressurized Digestion in Open Vessels Advantage Quasi infinite vessel volume Maximum possible temperature depends only from applied pressure Simple digestion vessels Graz University of Technology October

19 Wet Digestion at High Temperature Pressurized Digestion in Open Vessels B. Maichin, M. Zischka, ; Pressurized Wet Digestion in Open Vessels, J. Anal. Bioanal. Chem in press HPA-S (Anton Paar Comp., Graz, Austria) 1 Autoclave 2 Lid of the autoclave 3 Ring retainer 4 Rupture disc 5 PTFE liner 6 Heating element 7 Thermocouple 8 Water bath 9 Quartz vessel 10 PFA vessel 11 PTFE lid for digestion vessel 12 Vessel rack made of titanium Graz University of Technology October

20 Wet Digestion at High Temperature Pressurized Digestion in Open Vessels HPA-S Graz University of Technology October

21 Wet Digestion at High Temperature Pressurized Digestion in Open Vessels Quatz Vessels 50 ml PFA Vessels 25 ml Autosampler Cups (PFA) 1.5 ml Sample amount 1.0 g 0.5 g 50 mg Digestion mixture 5.0 ml HNO ml HCl 5.0 ml HNO ml HCl 0.2 ml HNO ml H2O ml H2O2 Graz University of Technology October

22 Wet Digestion at High Temperature Pressurized 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 % Graz University of Technology October

23 Wet Digestion at High Temperature Pressurized Digestion in Open Vessels UltraClave (Milestone) Graz University of Technology October

24 UV Assisted Wet Digestion M. Kolb, P. Rach, J. Schäfer, A. Wild; Fresenius J. Anal. Chem. 342 (1992) 341 G. 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 Graz University of Technology October

25 UV Assisted Wet Digestion Principle of the digestion apparatus. Very low concentration of HNO3 and H2O2 Quartz Vessel Digestion Solution UV - Lamp Graz University of Technology October

26 Microwave Assisted High Temperature UV Sample Digestion Dieter Florian, Günter Knapp; Anal. Chem. 2001, 73, , US Pat. 6,210,538 B1; Apr Microwaves as energy source for simultaneous heating of the reaction mixture and for generation of UV radiation. Graz University of Technology October

27 Microwave Boosted UV-Reactor for Photochemical Reactions at High Temperatures Graz University of Technology October

28 Microwave Assisted UV Digestion of Organic Substances at High Temperatures Graz University of Technology October

29 Advantages of Microwave Assisted UV Digestion at High Temperatures Acceleration of the degradation process owing to high reaction temperature ( C) Best efficiency of generated UV-radiation (immersion system) Enhancement of reactivity due to simultaneous microwave and UVirradiation Closed system and therefore low risk of systematic errors Graz University of Technology October

30 Microwave Assisted UV Digestion Procedure 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: mg sample + 7 ml H 2 O + 1 ml H 2 O ml HNO 3 vessel pressurized with 10 bar oxygen 30 Min. at 80 bar (about 250 C) Graz University of Technology October

31 Microwave Assisted UV Digestion Results 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 Graz University of Technology October

32 Combustion Systems Combustion of organic samples in closed systems is state of the art for the determination of volatile nonmetals. Graz University of Technology October

33 Combustion Systems Oxygen Bomb a) Steel bomb b) Lid with valve c) Electrodes d) Ignition wire e) Sample holder Graz University of Technology October

34 Combustion Systems Oxygen Bomb 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 ml of absorption solution. The bomb is closed with the lid and filled with oxygen to the required pressure of 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 -, SO4 2-1 hour F - 3 hours Absorption solution: Cl -, F - ion chromatography eluent (CO3 2- / HCO3 - ) Br -, J -, SO4 2- ion chromatography eluent (CO3 2- / HCO3 - ) or diluted NaOH + 3 drops 30% H 2 O 2 Graz University of Technology October

35 Combustion Systems Microwave Assisted Sample Combustion E.M. Flores, J.N. Paniz, J.S. Barin, J.A. Medeiros; Pat. Pen. Graz University of Technology October

36 Combustion Systems Microwave Assisted Sample Combustion MULTIWAVE ml quartz vessels 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 - cooling air cooling air stopper with rupture disc and sealing screw cap sample sample holder decomposition vessel vessel jacket cooling air Graz University of Technology October

37 Microwave Assisted Sample Combustion Results Cl S certified measured certified measured BCR 60 Aquatic plant 10 g / kg 9.3 ± 0.8 g / kg 5.2 g / kg 5.0 ± 0.4 g / kg BCR 61 Aquatic plant 2.3 g / kg 2.3 ± 0.3 g / kg 2.3 g / kg 2.1 ± 0.3 g / kg BCR 63 Milk powder 9.94 ± 0,3 g / kg 10.1 ± 1.0 g / kg BCR 100 Peach leaves 1.49 ± 0.06 g / kg 1.55 ± 0.1 g / kg 2.69 ± 0.04 g / kg 2.7 ± 0.1 g / kg BCR 186 Pig kidney 9.4 g / kg 9.5 ± 0.5 g / kg Graz University of Technology October

38 Microwave Assisted Sample Combustion Demonstration Combustion of 0.4 g Milkpowder MULTIWAVE ml Quartz vessel Loaded with 20 bar oxygen Graz University of Technology October

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40 Trends in Sample Preparation July 02 th 05 th, 2006 Seggau-Castle / Styria AUSTRIA Graz University of Technology October

41 Trends in Sample Preparation 2006 July 2th 5th, 2006 Seggau-Castle / Austria 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; Graz University of Technology October