Accelerated Solvent ExtractionAccelerated Solvent ExtractionASEASE

ASEASE

►►Pressurized fluid extraction (PFE)Pressurized fluid extraction (PFE)►►Pressurized liquid extraction (PLE)Pressurized liquid extraction (PLE)►►Performed at elevated temperature Performed at elevated temperature

(50(50--200 200 ooCC) and pressure (1500) and pressure (1500--2000 2000 psipsi))

►►DionexDionex Corp. SFE Corp. SFE ASEASEOvercome limitations of SFE (matrix Overcome limitations of SFE (matrix dependent, organic modifier)dependent, organic modifier)

Solubility and Mass Transfer EffectSolubility and Mass Transfer Effect

High Temperature

Increases the capacity of solvent to solubilize analytes

Faster diffusion rateImproves mass transfer

Increases extraction rate

Disruption of Surface EquilibriaDisruption of Surface Equilibria

►TempDisrupts solute-matrix interactionsDecreases viscosityImproves penetration on matrixImproves extraction

►PressureSolvent remains liquefied above their boiling pointEnhances extraction within the matrix

PumpPump

NN22

SolventSolventPurge Purge valvevalve

OvenOven

Static Static valvevalve

Collecting vialCollecting vial

Extraction Extraction cellcell

Load sample Load sample

Fill cell with Fill cell with solventsolvent

Heated and Heated and pressurized cellpressurized cell

Hold sample at Hold sample at P and TP and T

Pump clean Pump clean solventsolvent

Purge with NPurge with N22

Extract for Extract for ready analysisready analysis

Temp. ~ 200 oCPressure ~ 500 – 3,000 psi

Schematic of ASE

ASE SystemASE System

ASE 100ASE 100ASE 200ASE 200

ASE 300ASE 300

ASE Saves Solvent, Time & MoneyASE Saves Solvent, Time & Money

$27$16$24$23$14

4 - 48 hr1 - 4 hr

30 min – 1 hr30 min – 2 hr12 – 18 min

200-500 mL50-100 mL100-300 mL

8-50 mL15-40 mL

SoxhletAutomated SoxhletSonicationSFEASE

Average cost Average cost per sampleper sample

Average Average extraction extraction time per time per samplesample

Average Average solvent used solvent used per sampleper sample

ASE Method DevelopmentASE Method Development

►►Pressure and temperaturePressure and temperature►►Static timeStatic time►►Number of static cyclesNumber of static cycles►►Flush volumeFlush volume

ApplicationApplication

►►Environmental, i.e., EPA SWEnvironmental, i.e., EPA SW--846846►►FoodFood►►PolymerPolymer►►PharmaceuticalPharmaceutical

Microwave Assisted ExtractionMicrowave Assisted Extraction

Microwave Assisted Acid Microwave Assisted Acid DigestionDigestion

MicrowaveMicrowave

►► Electromagnetic waveElectromagnetic wave►► λλ = 0.3 mm = 0.3 mm –– 1 mm1 mm►► νν = 100 GHz = 100 GHz –– 300 MHz300 MHz

►►Operate at 2.45 GHzOperate at 2.45 GHz

Microwave Generator Microwave Generator -- MagnetronMagnetron

Anode block inside a magnetron Anode block inside a magnetron

Side view of the magnetron Side view of the magnetron

Clockwise motion ofClockwise motion ofelectrons in the anode block electrons in the anode block

Cloud of electrons andCloud of electrons andthe induced current the induced current

Microwave chamber Microwave chamber

Convective vs. Microwave HeatingConvective vs. Microwave Heating

►►Convective HeatingConvective HeatingFlameFlameHot plateHot plateHeating mantlesHeating mantlesOvenOvenHeating blockHeating blockSample Sample independentindependent

►►Microwave heatingMicrowave heatingDirectly heatDirectly heatDipole rotationDipole rotationIonic conductionIonic conductionHeated above BP Heated above BP possiblepossibleSample dependentSample dependent►►Microwave absorbing Microwave absorbing

characteristiccharacteristic

Heating Using MicrowaveHeating Using Microwave

►►Ionic conductanceIonic conductanceElectrophoreticElectrophoretic migration of ions when an migration of ions when an electromagnetic field is appliedelectromagnetic field is applied

►►Dipole rotationDipole rotationRealignment of dipoles with the applied fieldRealignment of dipoles with the applied fieldAt 2.45 GHz, dipoles align ~5 billion times/secAt 2.45 GHz, dipoles align ~5 billion times/sec

HEAT

Microwave Oven (To heat food)

Interaction between water Interaction between water molecule and microwave molecule and microwave

WaterWater RotateRotate FrictionFriction HotHot

Microwave Microwave –– Sample PreparationSample Preparation

►►Electromagnetic radiation to Electromagnetic radiation to desorbdesorbanalytes from their matricesanalytes from their matrices

►►Microwave energy as a heating sourceMicrowave energy as a heating source►►Open vessel microwave heating systemOpen vessel microwave heating system

Like automated Like automated SoxhletSoxhlet►►Closed vessel microwave heating systemClosed vessel microwave heating system

Extracting Solvent MechanismExtracting Solvent Mechanism

►►Sample immersed in a single solvent or Sample immersed in a single solvent or mixture of solvents that strongly absorb mixture of solvents that strongly absorb microwave energymicrowave energy

►►Sample extracted with both high and low Sample extracted with both high and low dielectric losses in various proportionsdielectric losses in various proportions

►►Samples that have a high dielectric loss Samples that have a high dielectric loss extracted with a microwave transparent extracted with a microwave transparent solventsolvent

OpenOpen--VesselVessel MAEMAE

OpenOpen--VesselVessel MAEMAE

H. Budzinski, M. Letellier, P. Garrigues, and K. Le Menach, J. Chromatogr. A, 837 (1/2), 187-200 (1999)

•Atmospheric pressure microwave

•Focused microwave

•Microwave assisted soxhlet extraction

ClosedClosed--Vessel MAE SystemVessel MAE System

G. LeBlanc, LC-GC, 17 (6S), S30-S37 (1999)

Closed vessel microwave heating systemClosed vessel microwave heating system

►►Vessel; PTFE, quartzVessel; PTFE, quartz►►Outer body; PPOuter body; PP►►Temperature controlTemperature control►►Indirect heatingIndirect heating►►StirringStirring►►Solvent safety featuresSolvent safety features

MultiwaveMultiwave MAE systemMAE system

MultiwaveMultiwave 3000 3000

VesselVessel

Microwave transparent materials

G. LeBlanc, LC-GC, 17 (6S), S30-S37 (1999)

Reflux actionReflux action

R.C. Richter, D. Link, H.M. Kingston, Anal. Chem., 73 (1), 30A-37A (2001).

Solvent Boiling Point and Closed Solvent Boiling Point and Closed Vessel Temperature comparisonVessel Temperature comparison

164164160160194194140140162*162*151151

56.256.25252

81.681.639.839.864.764.768.768.7

AcetoneAcetoneAcetoneAcetone--cyclohexanecyclohexane 7:3 (7:3 (v/vv/v))AcetonitrileAcetonitrileMethyleneMethylene chloridechlorideHexaneHexaneMethanolMethanol

Closed Vessel Closed Vessel Temperature Temperature

((ooCC))

Boiling Point (Boiling Point (ooCC))SolventSolvent

*Using carbon black filled fluoropolymer heating insert

n-Hexane

Acetone

n-Hexane with insert

Tem

pera

ture

(o C

)

Time (min)

Indirect HeatingIndirect Heating

Microwave Microwave –– EPA MethodEPA Method

►►EPA SWEPA SW--846 846 Method 3015 (acid digestion of aqueous Method 3015 (acid digestion of aqueous sample)sample)Method 3051 (acid digestion of sediments, Method 3051 (acid digestion of sediments, sludgessludges and soils)and soils)Method 3052 (acid digestion of organic based Method 3052 (acid digestion of organic based matrices)matrices)Method 3546 (organic extraction)Method 3546 (organic extraction)

Method DevelopmentMethod Development

►►PretreatmentPretreatment►►Choice of solventChoice of solvent►►Solvent volumeSolvent volume►►TemperatureTemperature►►Extraction timeExtraction time►►Matrix characteristic and water contentMatrix characteristic and water content►►Additional cleanAdditional clean--upup

Comparison of Extraction Methods for Solid Sample Preparation

Moderate6 (batch)0.1-0.2AtmAmbient20-302-10Open vessel MAE

Moderate12 (batch)0.1-0.21500-2000 psi100-200302-5Closed vessel MAE

High24 (serial)6 (batch)

0.2-0.31500-2000 psi50-20010-451-30ASE

High44 (serial)0.5-1.02000-4000 psi50-15010-205-10SFE

Moderate6 (batch)1-4Atm40-10050-10010-20Automate Soxhlet

Very Low1 (serial)12-24Atm40-100200-50010-20Soxhlet

CostNumber of

samples

Time (hr)

PressureTemperature

(oC)

Solvent volume (mL)

Sample size (g)

Method

Sample Preparation for Sample Preparation for Metal AnalysisMetal Analysis

Metal DeterminationMetal DeterminationBulk Sample Preparation

Sieving/GrindingDividing bulk sample to obtain proper size sample

Dissolution or extraction of analyte

Concentration if too dilute for analytical system

Measurement by selected analytical procedureFAAS, GFAAS, ICP, ICP/MS, IC, XRF

Sample PreparationSample Preparation

►►Dissolution of the entire sample producing a Dissolution of the entire sample producing a clear solutionclear solution

Wet acid digestionWet acid digestion: dissolve by heating in a : dissolve by heating in a strong oxidizing acid solutionstrong oxidizing acid solutionDry Dry ashingashing: moist samples, destroy organic : moist samples, destroy organic mattersmattersExtractionExtraction: water samples, chelating agent, : water samples, chelating agent, complex of metalscomplex of metals

►►Prevention of sample contaminationPrevention of sample contamination

Wet Digestion MethodsWet Digestion Methods

►►Total matrix dissolutionTotal matrix dissolution►►All the metals are in the same formAll the metals are in the same form►►Destroy information about the species Destroy information about the species

originally presentoriginally presentAcid digestion Acid digestion –– Wet Wet ashingashingMicrowave digestionMicrowave digestion

Reagents used for digestionReagents used for digestion

Silicates and other rock samplesSilicates and other rock samplesHydrofluoric acidHydrofluoric acid

Metals, alloys, soils, particulates Metals, alloys, soils, particulates from air, refractory minerals, from air, refractory minerals, vegetable mattervegetable matter

Concentrated acid with added Concentrated acid with added oxidizing agent (Hoxidizing agent (H22OO22))

Less readily oxidized metals and Less readily oxidized metals and alloys, steels, metal oxidesalloys, steels, metal oxides

Concentrated acid (e.g., HNOConcentrated acid (e.g., HNO33))

Dry Dry ashedashed sample residues, easily sample residues, easily oxidized metals and alloys, saltsoxidized metals and alloys, salts

Dilute acidsDilute acids

Soluble saltsSoluble saltsWaterWater

Sample typeReagent

Acid DigestionAcid Digestion

5-10% HNO3H2O2 may be added

Watch glass

Solution becomes clear and light colored

Hot plate

Analyte may loss due to the retention of metals in the silica residues

Microwave DigestionMicrowave Digestion

►►Closed vessel microwave systemClosed vessel microwave system►►Polymer container (PTFE)Polymer container (PTFE)►►Eliminate airborne dust contaminationEliminate airborne dust contamination►►Reduce evaporation, less acid solutionReduce evaporation, less acid solution►►Eliminate volatile metal speciesEliminate volatile metal species►►Reproduce digestion conditionsReproduce digestion conditions►►Reduce operator attentionReduce operator attention

Dry Dry AshingAshing

►► For samples contain much organic matter which For samples contain much organic matter which are being analyzed for nonvolatile metals; are being analyzed for nonvolatile metals; nutritional elements in foodnutritional elements in food

►► Crucible; silica, porcelain, platinumCrucible; silica, porcelain, platinum►► Ignited in a muffle furnace (400Ignited in a muffle furnace (400--500 500 °°C)C)►► Loss due to volatilizationLoss due to volatilization►► Air borne dust contaminationAir borne dust contamination►► Irreversible sorption into the wall of the vesselIrreversible sorption into the wall of the vessel►► Additives: HAdditives: H22SOSO44, Mg(NO, Mg(NO33))22, Na, Na22COCO33, , MgOMgO

ExtractionExtraction►►A soluble form is of concernA soluble form is of concern►►Metal Metal chelateschelates, metal, metal--organic complexes, organic complexes,

ionion--pairingpairing►►LLE, SPE, SLMLLE, SPE, SLM►►Chelating agentsChelating agents

N

S S NH4+

NO

O

NH4+

NOH

N NN

S

N

Ammonium pyrrolidinedithiocarbamate

Cupferron

8-hydroxyquinoline

Dithizone (Diphenylthiocarbazone)

Extraction of Extraction of chelatedchelated metalmetal

Org.Aq.

HA HA

H+ + A-

M+

+MAMA

K1

K2

K3K4

K2 = [H+]aq[A-]aq

[HA]aq

K3 = [MAn]aq

[Mn+]aq[A-]naqK4 = [MAn]org

[MAn]aq

K1 = [HA]org

[HA]aq

D = Concentration of metal in organic phaseConcentration of metal in aqueous phase

OthersOthers►►Precipitation methodPrecipitation method►►Sample slurriesSample slurries

Distribution of fine particles in a liquidDistribution of fine particles in a liquid

►►Hydride generation methodHydride generation methodAs, Se As, Se →→ NaNa44BHBH

►►Colorimetric methodColorimetric methodOxidation state: color forming reagentOxidation state: color forming reagent

►►Metal speciationMetal speciationIdentification and determination of individual physicalIdentification and determination of individual physical--chemical forms chemical forms →→ total concentration in a sampletotal concentration in a sample

Metal SpeciationMetal Speciation

►►Range of chemical forms, solid and Range of chemical forms, solid and dissolved phasesdissolved phases

►►Hydrated ion, inorganic and organic Hydrated ion, inorganic and organic complexes, heterogeneous colloidal complexes, heterogeneous colloidal dispersions, dispersions, organometallicorganometallic

►►SorbedSorbed with particles or organic solidwith particles or organic solid►►Bound with mineralsBound with minerals►►Present in more than one valence statePresent in more than one valence state

Metal Speciation informationMetal Speciation information

►►Toxicity: effect on living organismToxicity: effect on living organism►►Mobility: transport of element to Mobility: transport of element to

environmentenvironment►►Bioavailability, bioaccumulation: influence of Bioavailability, bioaccumulation: influence of

species on animals and plants, susceptibilityspecies on animals and plants, susceptibility