DXC 2009 – Preparation of Liquid Samples€¦ · DXC 2009 – Preparation of Liquid Samples 9 2009 DXC Liquid Preparation July-2009 Double Open Ended Cells 2 (tube below) Cell with

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DXC 2009 – Preparation of Liquid Samples

July-20092009 DXC Liquid Preparation1

Preparation of Liquid Samples

2009 Denver X-Ray Conference

Larry G. AriasProject Manager XRF Software / Manager XRF-US ApplicationsBruker AXS Inc. – Madison, [email protected]


Basic Preparation of Liquid Samples

Pour sample into plastic cellFit polymer film to end of cellInvert cellPunch vent hole to allow for expansion

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Considerations for liquid preparation

Selection of sample cellEasy to assembleFits sample holders for spectrometerAppropriate for spectrometer opticsAppropriate for type of sample

Selection of polymer filmDurability (from handling and exposure to x-rays)Resistant to chemical attack from sampleGood transmission of the energies to be measuredContaminates in the polymer film

Effective layer depth for all lines being measuredDon’t want intensities to change by volume of sample measured

Laboratory practicePreparing samplesHandling filmHandling cells

Mechanics of preparing samples


Select a Sample Cell That Fits the Sample Holder

Many sample holders have removable springs to keep samples stationary

Avoid using these springs wheneverpossibleContamination of holder by liquidExtraneous radiation from metal plate for higher energy lines

Centering rings or centering devices are available for all sample holders

Hold sample cell over cup opening without the need of a spring

Select a sample cell with inside diameter just larger than diameter of opening in cup

Helps prevent sagging of film

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Types of X-Ray Spectrometer Optics

Tube below optics(Inverted optics)• Ideal for liquids• Gravity works in our favor

because analyzed surface is facing down

Tube above optics(Normal optics)• Not ideal for liquids• Working against gravity because

analyze surface is facing up


Closed Cells (used with tube below)

Cell with large sleeveSleeve is used to hold film firmly in place

Cell with small clamping ring and optional collar

Collar is used to hold film loosely in placeSmall clamping ring clamps film firmly to cell

Good for:• Samples that flow well• Samples that are not volatile

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Closed Cells - Top View

Vent area on back of cellArea where cell is very thin to allow easy ventingPuncture with push-pin or other sharp object

Snap post™Cell has post which can be pushed in to vent cell“Snap post” is a trade mark of SPEX Certiprep

Most closed cells have a reservoir on top to catch expanding liquid


Double Open Ended Cells 1 (tube below)

Cell with large sleeve and capSleeve is used to hold film firmly in placeVented cap placed on cell after filling with sample

Good for:Samples that do not flow wellVolatile samples

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Double Open Ended Cells 2 (tube below)

Cell with small identical clamping ringsSmall clamping ring clamps film firmly to cellSecond clamping ring can be used to close cell with polymer film or micro-porous film on top side

Optional vented caps are available

Good for:Samples that do not flow wellVolatile samples


Micro X-Cells (tube below)

Available from SPEX CertiPrep®

Aperture of 6.3 mmFits standard 31 mm sample holderCan be fitted with standard 7 X 13 mm serum bottle closure

Allows pre-filling with inert gas for air sensitive samples

Collar to loosely hold film to cellCell with film snaps into hole of 31 mm bottom to firmly clamp film in placeClamping ring can be used to close top of cell with polymer film, micro-porous film, or serum bottle closure

Good for:Small amounts of sample

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SpectroMicroTM Cells (tube below)

Clamping ring to firmly clamp film to bottom of cellVented cap to close top of cell

Apertures of 6, 10, 15 and 20 mmFits standard 31 mm sample holderHas integrated funnel for easy sample loading

SpectroMicroTM is a trade mark of Chemplex Industires

Good for:Small amounts of sample


Special Cell Inserts for Tube Above Optics

Available from SPEX Certiprep®

Bubble-Free Cell InsertFits in standard 40 mm cellAir bubbles end up trapped in area shown by red circles in cut away view

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Films for Liquid Sample Cells

Liquid sample cells must be covered with a thin film which acts as the sample window

Film should be free from contaminates which are the same as any elements to be determined at low levels.Film must have reasonably high transmission of the X-ray energies to be measured.Film must contain the liquid without deterioration

Generally speakingChoice of film may be dictated by type of sample to analyzed

To avoid chemical attack which would weaken the film

Thicker films are more durable than thinner films Safer to use

Thicker films absorb more of the lower X-ray energies produced by the sample

Lower performance for low energy lines (low atomic number elements)


Contaminates in Films

Every film can have contaminatesThese contaminates become an issue when:

One of them is the same as an element being measuredAn emission line from the contaminate interferes with a line being measured

Contamination levels can be different between films with different lot numbersPurchase film in large quantities

More likely to be from the same Lot numberAll boxes of film will have the same level of contamination

If contaminates are an issueUse “Blank Subtraction”Make New Calibrations each time film is purchased

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Checking Films for Contaminates

Each time new film is received it should be tested for contaminates before using it• Film is not manufactured for XRF use• Film is typically not pre-tested by supplier• Manufacturer of film can change process at any time

Preferred method:• Allows accounting for system and sample contaminates

2-theta scan on a blank sample in a vacuum path(Example: Pressed cellulose, wax, etc)2-theta scan on same blank sample with a piece of film in front of itOverlay the two scans

Alternate method:• Does not account for system or sample contaminates

2-theta scan on a blank sample in helium atmosphere(Example: Distilled water, Base Oil, etc)View the scan


Contaminates in Polyester (Mylar®) Films

Ca and P are significantTraces of Sb and SiTypical supplier reports:

Ca, P, Sb, Fe, Zn

01

23

4

KC

ps

Ca

KA1

111.5 112 112.5 113 113.5 114. 3

° 2Th LiF200

00.

10.

20.

30.

40.

50.

60.

70.

80.

91

KC

ps

Sb L

A1

116 116.5 117 117.5 118 118.5

° 2Th LiF200

01

23

45

6

KC

ps

P K

A1

88 89 90 91

° 2Th PET

00.

10.

20.

30.

40.

50.

60.

7

KC

ps

Si K

A1

108 109 110

° 2Th PET

Mylar® is registered trademark of E.I. duPontde Nemours & Co. for its polyester film

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Contaminates in Polyimide (Kapton®) Films

Ca and P are fairly significantTypical supplier reports: Phosphate based surface coating

00.

10.

20.

30.

40.

50.

60.

70.

80.

91

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

KCps

P K

A1

88 89 90 91

° 2Th PET

00.

10.

20.

30.

40.

50.

60.

70.

80.

91

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

KCps

Ca K

A1

112 112.5 113 113.5 114

° 2Th LiF200


Contaminates in Polycarbonate Films

Traces of SiSupplier reports “Unknown”

0.2

0.3

0.4

0.5

0.6

0.7

KCps

Si K

A1

108 109 110

° 2Th PET

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Contaminates in EtnomTM Films

Traces of Si and PSupplier reports: Si, Ca, P, Zn, Sb

00.

10.

20.

30.

40.

50.

60.

81

23

KC

ps

Si K

A1

105 106 107 108 109 110 111 112 113

° 2Th PET

00.

010.

020.

040.

060.

080.

10.

20.

30.

4

KC

ps

P

KA

188 89 90 91

° 2Th PET


Contaminates in Polypropylene Films

Traces of S, Si and AlTypical supplier reports: Ca, P, Fe, Cu, Zr, Ti and Al

0.3

0.4

0.5

0.6

0.7

0.8

0.9

KCps

S K

A1

74.6 75 75.5 76 76.5 77

° 2Th PET

0.2

0.3

0.4

0.5

0.6

0.7

KCps

Si K

A1

108 108.5 109 109.5 110

° 2Th PET

0.06

0.08

0.1

0.2

0.3

0.4

KCps

Al K

A1

143 144 145 146

° 2Th PET

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Selection of Film for Transmission Properties

Thickness of Film is directly proportional to:Safety of use – less likely to break, leak, or sagEase of handlingAbsorption of lower energy X-rays (low atomic number elements)

Average atomic number of film is directly proportional to its absorption:

Films with Oxygen or Nitrogen have higher absorption then Carbon-Hydrogen films


X-ray Transmission by Films of Same Thickness

10

20

30

40

50

60

70

80

90

100

2 3 4 5 6 7 8 9 10 11 12

Wavelength in Angstroms

%-T

rans

mis

sion Polypropylene 6.0µ

Polycarbonate 6.0µEtnom-S 6.0µPolyimide 6.0µMylar 6.0µ

NaMgAlSiPSCl

BrRbZrMoRh

K-lines

L-lines

Etnom-STM is a Trade Mark of Chemplex IndustriesMylar® is registered trademark of E.I. duPont de Nemours & Co

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X-ray Transmission for Common Films

10

20

30

40

50

60

70

80

90

100

2 3 4 5 6 7 8 9 10 11 12

Wavelength in Angstroms

%-T

rans

mis

sion

Polypropylene 4.0µPolypropylene 6.0µPolypropylene 12.0µPolycarbonate 5.0µPolyimide 7.5µMylar 1.5µMylar 2.5µMylar 3.6µMylar 6.0µ

NaMgAlSiPSCl

BrRbZrMoRh

K-lines

L-lines

Etnom-STM is a Trade Mark of Chemplex IndustriesMylar® is registered trademark of E.I. duPont de Nemours & Co


Chemical Resistance of Films

Film suppliers have excellent detailed information on chemical resistance in their catalogs and on their web sites – Use this resource

Always test films before using themPrepare a sample and let sit for 30 – 60 minutes in same orientation the sample will be measuredCheck the film for wrinkles, sagging and leaks

YesYesYesEtnomTM

YesYesNoPolyimide ®

YesNoYesMylar®

NoNoYesPolycarbonate

NoYesYesPolypropylene

HydrocarbonsBasesAcids

General rules for chemical resistance of films

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Films are available in several physical forms

Continuous Rolls

Pre-cutCircles

Pre-CutSquares

Mounted on a Carrier Frame (1)

(1) Available from Chemplex Industries


Analyzed Layer and Infinite Thickness

No excitation of atoms in the upper part of the sample

Center part of the sample is excited but the emitted radiation is absorbed within the sample so it never reaches the detector

Fluoresced radiation that is actually measured comes from a layer near the sample surface

Called the Analyzed Layer

Thickness of Analyzed Layer is proportional to the energy of the line being measured

Thickness of Analyzed Layer is inversely proportional to average atomic number of sample

A sample is considered Infinitely Thick when its thickness is ≥ the Analyzed Layer depth

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Non-Infinitely Thick Samples

Samples are non-infinitely thick when:

sample thickness < analyzed layer

Intensities are no longer a function of just concentrations• Intensities vary by

o Concentration of analyte

o Thickness of sample

Analyzed Layer

Sample Thickness


Handling Non-Infinitely Thick Samples

Non-infinitely thick samples can be handled by

Measure a line with a lower energyLα instead of Kα

Mα instead of Lα

Use an Internal Standard technique

Use a Heavy Element Absorber technique

Weigh each sample into the cell to maintain a constant mass

Usually ± 0.1 gram

%

ISIIS

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Infinite thickness for K-lines (Oil & Water)

16.820.610.54As KA133As

13.516.59.887Ge KA132Ge

10.813.29.252Ga KA131Ga

8.710.88.639Zn KA130Zn

7.28.78.048Cu KA129Cu

5.76.97.478Ni KA128Ni

4.55.46.931Co KA127Co

3.64.26.404Fe KA126Fe

2.73.35.899Mn KA125Mn

2.12.55.415Cr KA124Cr

1.61.94.952V KA123V

1.21.44.511Ti KA122Ti

0.660.753.692Ca KA120Ca

0.480.543.314K KA119K

0.240.272.622Cl KA117Cl

Water SampleInfinite thickness

(mm)

Oil SampleInfinite thickness

(mm)

Energy(keV)

LineZEl

Most cells hold about 1 cm (10 mm) of liquid


Infinite thickness for L-lines (Oil & Water)

18.022.210.83Bi LA183Bi

16.520.410.55Pb LA182Pb

13.817.19.978Hg LA180Hg

10.813.29.175Ir LA177Ir

9.011.08.646Re LA175Re

8.19.98.397W LA174W

7.59.08.146Ta LA173Ta

6.68.17.899Hf LA172Hf

3.03.66.056Gd LA164Gd

1.21.44.464Ba LA156Ba

0.630.693.604Sb LA151Sb

0.540.603.444Sn LA150Sn

0.420.453.133Cd LA148Cd

0.360.392.984Ag LA147Ag

0.170.182.294Mo LA142Mo

Water SampleInfinite thickness

(mm)

Oil SampleInfinite thickness

(mm)

Energy(keV)

LineZEl

Most cells hold about 1 cm (10 mm) of liquid

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Preparation Hints

ASTM D7343-07 Standard Practice for Optimization, Sample Handling, Calibration, and Validation of X-ray Fluorescence Spectrometry Methods for Elemental Analysis of Petroleum Products and LubricantsProvides concise guidelines for

• Sample handling

• Sample preparation

• Sample stability

• Instrument validation

• Detailed sample preparation procedures

• Measurement of standards and samples

• Calibration

• Validation

Every technician dealing with the preparation of liquids should read and understand this Standard


Preparation Hints

Wear clean gloves, this will minimize contamination of sample cell and film by oils from hands

Ensure work surface is clean

Use clean lint free tissues on the work surface

Use sample cells with the smallest diameter opening that will cover the openings in the sample holders

Avoid touching the inside of sample cells

Handle film by edges and avoid touching the analyzed part of the film (portion to be X-rayed)

When placing a sample cell film side done on the work surface ensure it is on a clean lint free tissue

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Preparation Hints

When using closed cells punch vent hole immediately after attaching film.

Important for samples with high vapor pressure

Prevents bulging of film from pressure build up

Liquids that do not flow well can usually be heated in an oven at around 45ºC to improve their flow characteristics

After preparing samples allow the prepared cell to sit on a clean lint free tissue for about 30 seconds before placing into a sample holder

Put sample cell with film side down on tissue

Check tissue for signs of leakage when lifting sample


Preparation Hints

Ensure that the film on an assembled cell is free from any wrinkles• Discard and remake if not

Ensure that the film on an assembled cell is free from any dimples along the edges• Can displace sample• Can cause leaks• Discard and remake

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Preparation Hints

When using precut sheets of film try to keep film in contact with the separating paper to avoid static build up• The paper also serves as a clean

surface to place the assembled cell onto

Ensure sample cell is sitting properly in the sample holder

Flat against the bottomCentered on cup opening

Ensure that none of the film extends outside of the sample holder


Preparation of Closed Cell With Sleeve

Sample cellSleeve to clamp film to top of cellPieces fit together in only one orientation

Place sample cell on table with opening upPlace sample into cell to fill line• Usually about ½ to ⅔ full

Or weigh constant mass of sample into cell on a balance• Usually ± 0.1 gram

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Hold film over top of cell• Take care not to touch film in analyzed area

Seal film to cell using sleeve• Ensure sleeve is in correct orientation• Push sleeve down with steady even pressure• Do not distort the sleeve by squeezing too tightly

Ensure that• Sleeve does not rise above the body of cell• Film is tight and free from wrinkles



Invert cell on clean surface (film side down)Punch vent hold in top of cell

Place sample on clean tissue for about 30 seconds

Check tissue for dampness when lifting sample to load in sample holder

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Preparation of Closed Cell With Optional Collar & Clamping Ring

Sample cellOptional loosely fitting collar to pre-fix film to cellClamping Ring to fix film to cell

Place sample cell on table with opening upPlace sample into cell to fill line• Usually about ½ to ⅔ full





Pre-fix film to cell using the thin collar ring• This is an optional step

Seal film to cell using clamping ring• Push clamping ring down with steady even pressure• Do not distort the clamping ring by squeezing too

tightly

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tightly

Ensure that• Clamping ring does not rise above the body of cell• Film is tight and free from wrinkles

Alternate method using just the clamping ring:



Invert cell on clean surface (film side down)Punch vent hold in top of cell



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Preparation of Double Open Ended CellWith Sleeve and Vented Cap

Place sample cell on table in correct orientation(film side up) Hold film over top of cell• Take care not to touch film in analyzed area

Seal film to cell using sleeve• Ensure sleeve is in correct orientation• Push sleeve down with steady even pressure• Do not distort the sleeve by squeezing too tightly

Smaller diameter barrel is cellLarger diameter barrel is sleevePieces fit together in only one orientation


Preparation of Double Open Ended CellWith Sleeve and Cap

Place sample cell on table with opening up(film side down)Place sample into cell to fill line• Usually about ½ to ⅔ full


Ensure that• Sleeve does not rise above the body of cell• Film is tight and free from wrinkles

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Preparation of Double Open Ended CellWith Sleeve and Cap

Attach vented cap to top of cell




Preparation of Double Open Ended Cell With Clamp Rings and Vented Cap

Sample cellTwo identical clamping ringsOptional vented cap

Place sample cell on tableHold film over top of cell• Take care not to touch film in analyzed

area


tightly

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Ensure that• Clamping ring does not rise above the body of cell• Film is tight and free from wrinkles

Place sample cell on table with opening up(film side down)Place sample into cell to fill line• Usually about ½ to ⅔ full






Attach vented cap to top of cell

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Preparation of Double Open Ended Cell for Loose Powder using Micro-porous film

Fix film to cell as beforePlace cell on table with opening up(film side down)Place powder into cell

Hold micro-porous film over top of cell

Seal micro-porous film to cell using clamping ring• Push clamping ring down with steady even pressure• Do not distort the clamping ring by squeezing too tightly


Preparation of Double Open Ended Cell for Loose Powder using Micro-porous film

Micro-porous film might extend out quite far• Could get trapped between top and bottom of sample

holder• Could cause sample cell to not sit flat in sample holder

Trim excess from micro-porous film before placing into sample holder

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Preparation of Double Open Ended Cell With Samples That do not Flow Well

Fix film to cell as beforePlace cell on table with opening up(film side down)

Put sample into cell



Place piece of film on top of cell

Push excess film into cell

Hold cell firmly on clean flat surface and use rod to flatten the sample against the cell window• The rod should have a diameter of about 1-2 mm less

than the inside diameter of the cell

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Close cell with vented cap (optional step)

Check sample surface for defects

Close cell with film and make vent hole (optional step)


Preparation of Micro X-Cells

Sample cell (barrel) with 6.3 mm I.D.Collar to loosely hold film to cellCell with film snaps into hole of 31 mm base to firmly clamp film in placeClamping ring can be used to close top of cell with polymer or micro-porous film

Stand cell on table so small diameter end is facing upHold film over opening in cellLoosely fix film to cell using collar

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Place base on table (analyzed surface down)Snap cell into bass to seal film to base

Place base on table (analyzed surface down)Place film on top of baseSnap cell into bass to seal film to base

Alternate method without pre-fixing film



Orient assembled cell so opening is facing up

Place sample into cell

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Optional step• Seal top of cell with polymer film or micro-porous

film using the clamping ring

If top of cell was sealed with polymer film• Punch vent hole in film

NOTE: Serum bottle closure can be fitted to top of cell before adding liquid to allow injection of inert gas followed by injection of sample


Preparation using Bubble Free Insert

Place Bubble Free insert into closed liquid sample cell as shownPlace liquid sample in the cell to within 0.5 to 1.0 mm of top rimFix film to top of cell using clamping ring(push down with steady even pressure)Invert cell and “jiggle” to force air bubble through center hole of cell so it becomes trapped when cell is placed film side up

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Small Amounts of Liquids on Filter Papers

Commonly referred to as “Dried Spot”techniqueSmall amounts of liquid (20 – 50 µL) are put on a suitable filter then allowed to dryMultiple applications of a sample can be made to increase the concentration levelsEspecially useful for light element analysis

Can be measured in vacuumNo absorption by heliumCan be measured without filmNo absorption by polymer film

Filter papers from:• BREITLÄNDER• Hydrophobic Ring Filters• BR XRF42/25• BR XRF50/32


Na Calibration as Liquid versus on Filter Paper

Normal liquid calibration

Int. corrected

Cor

rect

ed In

tens

ity (K

Cps

)

Concentration (PPM)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

0.12

0 100 200 300

Std Dev = 3 ppmSens = 3.465 kCPS/%LLD = 8.5 ppm

50 µL of sample on filter paper

Int. corrected

Cor

rect

ed In

tens

ity (K

Cps

)

Concentration (PPM)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

0 100 200 300

Std Dev = 4 ppmSens = 33.047 kCPS/%LLD = 1.0 ppm

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Int. corrected

Cor

rect

ed In

tens

ity (K

Cps

)

Concentration (PPM)

00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.71.81.92.02.12.22.32.42.52.62.72.82.93.03.13.2

0 100 200

S Calibration as Liquid versus on Filter Paper

Normal liquid calibration

Std Dev = 0.4 ppmSens = 128.966 kCPS/%LLD = 0.5 ppm

50 µL of sample on filter paper

Int. corrected

Cor

rect

ed In

tens

ity (K

Cps

)

Concentration (PPM)

0

1

2

3

4

5

6

7

8

0 100 200

Std Dev = 0.6 ppmSens = 355.745 kCPS/%LLD = 0.2 ppm


Sources of Liquid Preparation Supplies

Chemplex Industries, Inc.2820 SW 42nd AvenuePalm City, FL 34990(800) 424-3675www.chemplex.com

Premier Lab Supply, Inc.2714 S.W. Edgarce StreetPort ST. Lucie, FL 34953(772) 873-1700www.premierlabsupply.com

Somar International, Inc.P.O Box 194759610 Prototype CtReno, NV 89511(775) [email protected]

SPEX CertiPrep203 Norcross AvenueMetuchen, NJ 08840(800) LAB-SPEX Ext 465www.spexcsp.com

Tech Ref Inc.2051 E. Cerritos Ave., Ste. FAnaheim, CA 92806 (800) 347-9593www.techrefinc.com

VHG Labs, Inc276 Abby RoadManchester, NH 03103(888) 622-7660www.vhglabs.com

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www.bruker-axs.com

Documents

DXC 2009 – Preparation of Liquid Samples€¦ · DXC 2009 – Preparation of Liquid Samples 9 2009 DXC Liquid Preparation July-2009 Double Open Ended Cells 2 (tube below) Cell with