© 2009 PerkinElmer

Determination of the 14C content in biodiesel. A method improving the detection sensitivity by decolorizing the biogenic materials in biofuels

M. Stomp-Smit, J. ter Wiel, R. Edler

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LSC for 14C samples of biogenic origin

14C of biogenic origin

History

Available Methods

Sample Preparation for removal of Color

Measurements with Biodiesel

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LSC for 14C samples of biogenic origin

14C measurements of biogenic origin

a.) Historically mainly carbon dating

b.) Differentiation between fossil

alcohol and alcohol from

fermentation in wine and spirits

Interest in biogenic 14C increased

with the increased interest in the

reduction of the emissions of the

fossil greenhouse gas CO2

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Regulations

Important steps for 14C measurements of biogenic samples

a.) Kyoto protocol December 1997 (binding obligations on

participating countries to reduce the emission of greenhouse

gases in general)

b.) Farm Security and Rural Investment Act in 2002

c.) Directive 2003/30/EC of the European Parliament in 2003

(exact definition of minimum amounts of biogenic additives to

fuel)

d.) Federal Biobased Products Preferred Procurement Program

(FB4P). In 7 CFR 2902.7 ASTM 6866 is used to determine the

amount of biogenic 14C

e.) CEN/TR 15591/EN 15440 in 2006 describes the determination

of 14C in solid recycled fuel.

f.) DIN 51637 (2013?) determination of HVO in fuel

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Importance of routine measurements

Why are measurements so important

a.) Only one out of 10 samples passed the specifications that the United

States Department of Defense required for blends that contain 20%

biodiesel (C. M. Reddy et al.)

b.) Tax difference between fossil and biogenic fuel components in many

countries

C. M. Reddy, J. A. DeMello, C. A. Carmichael, E. E. Peacock, L. Xu, J. S. Arey; Determination of Biodiesel Blending Percentages Using Natural Abundance Radiocarbon Analysis: Testing the Accuracy of Retail Biodiesel Blends, Environ. Sci. Technol. 42, 2476 (2008).

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Methods for 14C determination in biogenic materials

Method Merit Drawback

Direct LSC Analysis

Minimal, fast sample preparation, good sensitivity, lower costs per evaluation, high

instrument availability, LSC is the most widely used method for 14C determination

Not in accordance with ASTM standard D6866-12 which discusses methods A, B

and C

Method A: CO2 & LSC Less sample preparation than in Method C, lower costs per evaluation, high instrument

availability worldwide

Small sample activity due to limited uptake capacity of Carbo-Sorb E, not

sensitive for lowest 14C concentrations

Method B: AMS/IRMS High sensitivity, precise High cost, mostly for cases in dispute or

less than 10% carbon by weight

Method C: Benzene Synthesis & LSC

High sensitivity, precise, high instrument availability worldwide

Slow sample preparation, small capacity, new benzene synthesizers hard to

acquire, benzene carcinogenic

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Direct Method for 14C determination in biogenic materials

The direct method for 14C determination is preferred

for liquid samples such as wine, alcohol and fuels

due to simplicity of this method.

The direct measurement of biodiesel based on

FAME was problematic so far, due to heavy color

quench in most biodiesel samples containing more

than 10%. Biodiesel. (R. Kristof, J. K. Logar)

R. Kristof, J. K. Logar; Quenching Parameter in the Measurement of Biodiesel by Liquid Scintillation Counting, LSC 2010, Advances in Liquid Scintillation Spectrometry, Proceedings of the 2010 International Liquid Scintillation Conference, Paris, France, 6-10 September 2010, P. Cassette (Editor), page 35 (2011).

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radioactive molecule

solvent molecule

fluor molecule

photomultiplier tube

The Basic Liquid Scintillation Process

b hn

Chemical Quench

Color Quench

Dipol-Dipol interaction Light 200 – 300 nm Molecule collisions

Light primary scintillator 340–400nm Light secondary sctintillator 400–470nm

Physical Quench

The Scintillation Process

Unfortunately chemical quench and colour Quench have different influence on the counting efficiency and correction cannot be done with a simple quench for chemical quench.

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Direct measurement of Biodiesel

For our investigations we used a Biodiesel sample

from Biovalue in Eemshaven, Netherlands. The

Biodiesel sample was produced from rapeseed

(brassica napus) which originated from all over the

world. All raw materials contained a strong yellow to

brown colour.

10% Biodiesel sample in 6 ml glass vial

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Direct measurement of Biodiesel

0

10

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30

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50

60

70

80

90

100

0 200 400 600 800 1000 1200

Effi

cie

ncy

(%

)

tSIE

Efficiency versus tSIE

C14 Quench Set

C14 yellow Dye

A pure biodiesel sample with a tSIE of 94 corrected with a chemical quench curve results in too high efficiencies and consequently in too low activities.

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Direct measurement of Biodiesel

For the comparison of calculated and theoretical DPM values we made the following assumptions:

1.) Biodiesel consists of 100% erucic acid

2.) Biodiesel density of 0.86 g/ml

3.) Modern carbon activity of 14 DPM/g carbon for biogenic material in 2010

O

HO

C22H42O2, molecular mass = 338.57 g/mol

Erucic acid, monounsaturated omega-9 fatty acid

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Purification of 10% biodiesel in heptane

Cycle1 CPM tSIE % Eff. % Lum.

Heptane 12,3 742 96,1 1

Fuel 36,1 746 96,1 1

10% Biodiesel

(yellow)

15,2 414 92,1 11

purified 14,1 680 95,9 1

Cycle2 CPM tSIE % Eff. % Lum.

Heptane 12,5 746 96,1 1

Fuel 37,1 741 96,1 0

10% Biodiesel

(yellow)

14,6 413 92,1 1

purified 13,4 678 96,0 0

Silicagel 60

1 cm

Initially we used a 10% biodiesel sample in heptane for ease of use. Measurements were done in Ultima Gold F with a Tri-Carb 2550TR/AB in 6 ml Pico glass vials, 3 ml sample, 3 ml Ultima Gold F in the open 14C window from 0 – 156 keV, counting time 60 minutes.

Aluminum oxide 90

Purification of 10% biodiesel in heptane

CPM tSIE %Eff. %Lum.

Original 16,1 438 92,7 1

Fraction 1 13,6 725 96,1 1

Fraction 2 15,4 690 95,9 1

Fraction 3 16,7 699 96,1 1

Fraction 4 16,3 700 96,1 1

Fraction 5 16,3 677 95,8 1

Fraction 6 16,4 713 96,1 1

10% biodiesel 1st, 2nd and 3rd fraction

Measurement of diluted biodiesel with Quantulus 1220

Sample µl yellow

dye

SQP CPM 14C

Eff.

1 0 940,0 8087,5 89,1

2 0 935,4 8027,3 88,5

3 50 864,7 7562,1 83,3

4 100 821,3 7052,2 77,7

5 150 779,0 6464,3 71,2

6 200 747,9 5769,2 63,6

7 300 711,6 4807,1 53,0

8 500 672,8 3403,4 37,5

9 700 641,0 2293,8 25,3

10 1000 603,9 1353,5 14,9

11 1500 574,5 788,4 8,7

12 2000 560,9 457,6 5,0

13 2500 535,8 303,2 3,3

y = -0,0004x2 + 0,7644x - 310,93R² = 0,9861

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800 900 1000

Effi

cie

ncy

(%

)

SQP

Quench Curve

Yellow dye solution in Ultima Gold F

Poly. (Yellow dye solution in Ultima Gold F)

Yellow dye: 20 mg dimethyl azobenzene in 100 ml Ultima Gold F All standards contained 9075 DPM +/- 1%

Accurate biodiesel measurements without removal of color require color correction

Measurement of diluted biodiesel with Quantulus 1220

Sample mg

biodiesel

SQP Ch 50

- 650

CPM -

blank

14C

Eff. %

dpm dpm/g

biodiesel

dpm/g

carbon

1 0 938 1.054

2 0 939 0.974

3 52.9 913 1.518 0.504 87.1 0.578 10.9 14.0

4 93.5 891 1.924 0.910 85.2 1.068 11.1 14.2

5 161.6 861 2.446 1.432 83.3 1.718 10.6 13.6

6 203.5 847 2.857 1.843 80.6 2.286 11.2 14.3

7 242.9 834 3.135 2.121 79.1 2.681 11.0 14.1

8 302.4 820 3.599 2.585 77.7 3.326 11.0 14.1

Measurement of different amounts of biodiesel in 10 ml Ultima Gold F in the open 14C window (channel 50 – 650)

Purification of undiluted biodiesel

CPM tSIE DPM Theory

Heptane 11,9 777 0 0

Original 20,2 94,7 20,4 23,5

Test 1,1 33,2 571 23,4 23,5

Test 1,2 32,5 557 22,6 23,5

Test 2,1 33,6 619 23,6 23,5

Test 2,2* 32,1 658 21,8 21,95

CPM tSIE DPM % Eff.

Heptane 8570 785 8970 95,5

Original 3657 94 4901 40,87

Test 1,1 8464 572 8990 94,3

Test 1,2 8480 566 9012 94,5

Test 2,1 8435 622 8923 94,1

Test 2,2* 8599 685 9064 95,8

Slightly different procedure:

50 g biodiesel were stirred with 3 g of aluminum oxide and 300 mg of charcoal for two hours at 50°C.

Two different column preparations:

Test 1: Only 10 g of aluminum oxide inside the glass column. Test 2: Column filled with 10 g of aluminum oxide and 2.5 g silica gel on top.

* The fraction Test 2,2 only contained 2 g of biodiesel, other samples contained 2.15 g biodiesel

Sensitivity for the measurement of undiluted biodiesel

m0

011

t

1

t

1R

VE

kkg

b

Bq/L

Sensitivity for colored biodiesel (120 min): 33.8 Bq/L

Sensitivity for colorless biodiesel (120 min): 14.4 Bq/L

Increasing the sample volume and optimizing the energy window allows sensitivities below 1 Bq/L in 120 minutes counting time on a Quantulus.

Purification of undiluted biodiesel

SQP (E) CPM

Channel

50-650

net CPM

channel 50-

650

Eff% DPM DPM

calculated

Blank (heptane) 839 0,597 75,7 0

1 g biodiesel 490 0,365 # ? ?

1 g purified 829 8,657 8,060 75,5 10,69 10,97

100 mg biodiesel 713 1,235 0,638 62,6 1,180 1,097

Measurements done in a Quantulus 1220 in 20 ml plastic vials using 10 ml Ultima Gold F

Problem background correction:

A major problem in colored samples is the determination of background. Colored samples require a quench dependent background correction.

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Summary

Normal chemical quench curve results

in accurate data.

Simple hydrocarbons can be used as

a background source.

High sensitivity

Colorless biodiesel

Untreated biodiesel samples require

color correction.

Quench dependent background

correction required.

Limited sensitivity

Colored biodiesel

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Finish

Thank you for your attention!!!

Ronald Edler

Specialist Radiometric Detection

Mobile: +49 (0) 172 638 5909

Email: ronald.edler@perkinelmer.com