Mineral oils in vegetable oils: tools for the analysis of

Mineral oils in vegetable oils: tools for the analysis of the saturated and the

aromatic hydrocarbons

Koni Grob

Kantonales Labor Zürich

10

15

Crude Arabian light

Kerosene

Distillation

Short introduction into mineral oil depicted by GC

Heating oil, Diesel oil

10

15

20

25


main components:

branched and cyclicMOSH

15-25 % MOAH

Terminology

- MOSH: mineral oil saturated hydrocarbons (paraffins and naphthenes)- MOAH: mineral oil aromatic hydrocarbons

Vaselinee.g. for cosmetics, pharmaceuticals

15

20

25

25

30

High boiling fraction;„white oil“: only MOSH;

extracted and hydrogenated


Wax (candle)

18

20

25 30

35

Crystallized fractionAlmost exclusively

n-alkanes


46 ºC 15 º/min 340 ºC

Diesel oil

Shell

BP

Total

21

28

35

29

27

2036

1711

Lubricating oil(motor oil)

Residue fromcrystallization

High boiling point (to avoid evaporation)

high viscosity(lubrication)

� high molecular mass

Must remain liquid also at low temperature

� removal of n-alkanes


20

25

30P

rista

ne

Ph

yta

ne

20

25

30

Prista

ne

Ph

yta

ne

1718

Hydraulic oil (building machinery)

Chain oil for motor saw


Environmental

contributionsDiesel exhaust

Soot 1

Soot 2

Tar road pavement

40

28

34

20

28

1718

25

30

30

40

50

46 ºC 15 º/min 340 ºC

16

25

18

25

1822

20

27

46 ºC 15 º/min 340 ºC

Aerosol from road tunnel

40

Exhaust from hot

diesel engine

lubricating oil

incompletely

burned fuel

residue fromdistillation

mainly

lubricating oil

Soot from

chimney

Exhaust from cold

diesel engine

Aerosol from

road tunnel

20

30

40

50

28

35

27

20

40

22

29

22

18

23

34

46 ºC 15 º/min 340 ºC

25

Lip stick 145 %

Lip stick 260 %

Vaseline100 %

Vaseline body lotion 36 %

Body lotion8 %

Hand crème1.1 %

Oints and salves

46 ºC 15 º/min 340 ºC

3036

31 37

40

20

28

40

20

38

40

Almond oil cream3.4 %

Nipple cream0.03 %

Vulnerary balsam40 %

Mastoid salve31 %

Vulnerary balsam17 %

2923 2923

85 mg/kg 60 mg/kg

15 mg/kg 360 mg/kg

A B

C D

Mineral oil in human body fat Abdominal fat from Cesarean sections (Bregenz und Innsbruck)

N. Concin et al., Food and Chemical Toxicology, 46 (2008) 544-552

Extremes in distribution

Extremes in concentrations

Toxicological evaluation

2923 2923

85 mg/kg 60 mg/kg

15 mg/kg 360 mg/kg

A B

C D

Mineral oil in human body fat Abdominal fat from Cesarean sections (Bregenz und Innsbruck)


average person contains~ 1 g mineral oil,

high levels: 10 g

no animal is as contaminated as humans

Samples 24

46 ºC 15 º/min 340 ºC

after 7 days42 mg/kg

after 14 days8 mg/kg

29

17

21

34

25

maximum determined: 1300 mg/kg fat!

Human milk


Hopanes as markers for mineral originengine (lubricating) oil, LC-GC-MS

Paraffins

Hopanes

80 °C 320 °C25 °/min 230 °C 8 °/min

Paraffins, m/z 81Hopanes, m/z 191

T. Populin, M. Biedermann, K. Grob, S. Moret, L. Conte. Food Addit. Contam. 21 (2004) 893-904


Hopanes in human milk� proof for mineral origin

80 °C 320 °C25 °/min 230 °C 8 °/min

Hopane segment

Hopanes

ParaffinsT

m

29αβ 30αβ

31αβS

35αβS


Toxicological evaluation WHO/JECFA

http://whqlibdoc.who.int/trs/WHO_TRS_913.pdf

• Relevant end points: accumulation in certain organs, reaction toforeign body (inflammation), increased weight of organs

• strong dependence by molecular mass

– viscosity (correlations? not measurable for contaminants)

– average molecular mass

– carbon number at 5 % distillation point (C-number at 5 % lowest molecular mass)


JECFA criteria for evaluating MOSH

27.5

36

20

5 % lowest

C23.5

average molecular mass

ADI of 10 mg/kg bw:

- average molecular mass 480-500 Da (C34)

- carbon number at 5 % distillation point: C25

�� typical lubricant oilsdo not comply

typical motor oil



mineralparaffins

28

26

72 °C (eluent evaporation)

temperature program 25 °C/min

350 °C

21

1729 31272523

C25natural

n-alkanes

terpenes

C34

JECFA-limits shouldeven be higher


MOSH accumulated by humans

Legal limit to be derived from JECFA

• ADI of oils with 5 % dist. point ≥C25 and average

molecular mass ≥480 Da: 0.01 mg/kg bw

• conventional assumptions for calculating limits

– 60 kg bw � 60 x 0.01 mg/d = tolerable dose 0.6 mg/d

– presence in 1 kg food

• most food are contaminated

• many sources

�0.6 mg/kg food

• many foods exceed this limit

• limit never written


...and the MOAH?

• JECFA-definition: „mixtures of highly refined paraffinic and naphthenic liquid hydrocarbons… “

• accepted in foods: „white“ oils

– extracted

– hydrogenated

– <1 % MOAH

• most mineral oils in food contain 15-35 % MOAH

• 97-99 % alkylated

– enormous number of isomers

– underestimated when analyzing the non-alkylated PAH

• no toxicological evaluation available


Principals for the methods of analysis

• FID as detector

– only detector with equal response for all hydrocarbons (calibration!)

• analysis by GC

– distinction from natural paraffins

– characterization of mineral oil

• broad humps of unresolved components

� MOSH and MOAH must be isolated from all other components

• interference of olefins (terpenes, squalene and

isomerizazion products, carotenes)

– MOSH: maximized selectivity of silica gel or increasing retention by bromination or epoxidation

Tool box for MOSH and MOAH analysis

• manual method for MOSH (� attachment)– silica gel column

– 50 ul injection (on-column or CSR splitless)

– epoxidation of interfering olefins

• on-line HPLC-GC or HPLC-HPLC-GC-FID for MOSH– standard method

– removal of plant n-alkanes by activated aluminum oxide

– reduced detection limit: enrichment by double-bed off-line LC

• on-line HPLC-GC for MOAH– direct analysis

– epoxidation of interfering olefins

– enrichment by off-line LC

• characterizing MOAH by GCxGC– by ring type or ring number

Withoutbromination

Internalstandards With

bromination

Manual method for MOSH analysis

Mitt.

Lebensm

. H

yg.

92 (

2001

) 231-2

49

Removal of

interfering olefinsbromination (method 2001)

used frying oil

Withbromination

Withoutbromination

Removal of olefinsbromination

Acids from oil refining

Internalstandards


Paraffin fraction

Subsequent fraction

Silica gel from the bottle

Mineral paraffins

Isomerizedsqualene

Squalene+ isomers

C14

C16

C40

C14

Insufficient preseparation: mineral paraffins would beoverestimated!

Refined olive oil

from canned fish


Paraffin fraction

Subsequent fraction

Mineral paraffins

Position of isomerized squalene

isomerized squalene

Silica gel heatedto 300 °C/12 h

Isomerized squalenetransferred to nextfraction or not eluted

Squaleneand mostisomersretained


Refined olive oil

from canned fish

Paraffin fraction

Subsequent fraction

Mineral paraffins (60 mg/kg)

still noisomerized squalene

- Silica gel heatedto 300 °C/12 h

- Epoxidation(� attachment)

Isomerized squaleneeliminated


Refined olive oil

from canned fish

on-line HPLC-HPLC-GC-FID

LC-LC-GC method for MOSH

• Direct injection of the (diluted) oil

• Isolation of the hydrocarbons from the fat/oil by first column

– Injection of 20 mg oil provides adequate sensitivity

– 2 mm i.d. column to match flow rate with transfer rate to GC

– 25 cm length to provide capacity for retaining oil (used to about 40%)

– Backflush with MTBE to remove bulk of oil after each run

• Fine separation on second column (olefins)

– Highly active silica � large internal surface area

• Transfer by partially concurrent eluent evaporation

– on-column or Y- interface

Dilution of the oil

Isolation of hydrocarbonson silica gel

Fine separation(removal of olefins) on

silica gel

GC-FID

Backflush with MTBE

Transfer to GC by retention gap technique


Details � attachment

Thermo Electron, 2004

Mineral paraffins

Mineral paraffins24

23

25

2729

31

33

35

24

23

25 27 29

31

33

GC overloaded by plant n-alkanes

Incomplete separation of overloaded plant n-alkanes hindersdetermination of uppercontour line of the hump

Two (different) olive pomace oils

Insufficient sensitivity. Injecting more samplewould overload plant n-alkanes

� Removal of plant n-alkanes

Removal of long-chain n-alkanes by activated aluminium oxide

MOSH?

MOSH?

Retention of long-chain n-alkanes

by activated aluminum oxide


Luboil

C24

C27

C30

C20

4 8 12 16 20Retention time (min)

C28

Isoalkanes(lubricating oil)

• 10 cm x 2 mm i.d. HPLC column filled with

aluminium oxide activated at 400 °C

• hexane (ca. 60 % n-hexane),

purified over aluminium oxide

• 300 µl/min

• Evaporative light scattering detection (ELSD)

n-alkanes• No significant retention for

isoalkanes (motor/lubricating oil)

• No significant retention for n-C20

• Rapidly increasing retention of longer chain n-alkanes

Unknown retention mechanism

Luboil

C24

C27

C30

C20

4 8 12 16 20Retention time (min)

C28

Isoalkanes(lubricating oil)

n-alkanes

Well fits our interests:- plant n-alkanes usually >C23;- dominant plant n-alkanes: C27-C33- most fuel oil n-alkanes <C20

Fraction to beanalyzed by GC

Retention of long-chain n-alkanes

by activated aluminum oxide


Influence of the mobile phase

Isooctane

Cyclohexane

C32

C30

C34

C32

C30

C28

C24

Luboil

C28

C24

Luboil

C34

C28

C24

Luboil

Luboil

n-Pentane

n-Hexane

C32

C30

Complete collapse

� useful for rinsingthe column


suitable for

preseparation

Performance for jute batching oil

15

20

23

20

15

25

MOSH fraction

Subsequentfraction

Aromatics furtherretained

Increased retention for n-alkanesas from C15

complete retention above C23

also for certain isoalkanes

Elution up to C25

higher molecular mass n-alkanesfurther retained


22 34

18

Loss of high molecular mass isoalkanes

Mineral paraffins in a body lotion

no loss

loss18 %


Concept for use in on-line LC-LC-GC

• Isolation of the paraffins by silicagel

– no alox: backflush with strong eluent would deactivate alox

• Aluminium oxide for second column

• Removal of retained n-alkanesby isooctane

• 10 cm x 2 mm aluminiumoxide column (ca. 300 mg)

– fraction volume remains at 300 µl

– flow rate suiting LC-GC transfer (300 µl/min) suits 2 mm i.d. column

Diluting the oil

Isolation of hydrocarbonson silica gel

Removal of plant n-alkanes by

aluminium oxide

GC-FID

Backflush with

dichloromethane

Rinsing withiso-octane


Flow system

Pump 1(hexane)

Autosampler

Waste

Injection

Valve 2

Silic

a g

el c

olu

mn

Waste

Waste

Valve 1

Transfervalve

Alu

min

ium

oxid

e

Waste

to GC(transfer lineto on-column

injector)

Purge oftransfer line

Pump 2 (isooctane)

100 µL injection

loop

Backflushloop (1 mL)

MTBE(pressurizedreservoir)

Resistance


J.

Agric.

Food C

hem

. 57 (

20

09)

8711-8

72

1

x1 x1

27

25

31

33

27

2533

31

23

29

SiO2 SiO2

Oil 1 Oil 2

29

Application to olive pomace (sansa) oils

x6x4

Alox 400 °C Alox 400 °C

SiO2 SiO2


reducedattenuation!

Application to corn oil25

27

29

23

29

31

25

23

27

SiO2

Alox 400 °C

x8x8

3 mg/kg


Lower detection limit: off-line enrichment

• detection limit <0.3 mg/kg oil

• e.g. for determining environmental contribution

• presupposes

– larger aliquot of fat/oil

– removal of plant n-alkanes

• required packed beds are too large for on-line LC-GC� off-line preseparation

� attachment

Alu

min

um

oxid

eS

ilica g

elRetention of fat

(triglycerides)

Retention of unsaturated hydrocarbons

Retention of long chain n-alkanes

Enrichment to decrease detection limit

25 °/min 350 °C

27

29 31

23C

ala

ren

e

25 °/min 350 °C 25 °/min 350 °C25 °/min 350 °C65 °C65 °C

On-line Si-Si-GC

Off-line Si-Al +on-line Si-Al-GC

Off-line Si-Al +on-line Si-Al-GCattenuated

65 °C65 °C

24

25

2324

25

3127

On-line Si-Al-GC

20

22

12

13

Example: sunflower oil


1.4 mg/kg

Determination of the mineral oil aromatic

hydrocarbons (MOAH)

• HPLC preseparation on highly retentive silica gel

– Lichrospher Si 60 (25 cm x 2 mm i.d.)

• hexane purified over activated silica gel

– MOSH fraction

• rapid gradient to 30 % dichloromethane � MOAH

– start: highly alkylated benzenes

– end: non-alkylated perylene

• verification standards monitor accurate cuts

Determination of the sum of the MOAH

Interference of olefins: selective epoxidation

• Olefins eluted in MOAH fraction: squalene + isomerization products, sterenes, carotenes, terpenes

• broad fraction: no chance of separation

• derivatization of olefins increases LC retention time

• reaction should not affect MOAH

– bromination is not selective (MOAH largely react also)

– epoxidation most selective

• most sensitive: thiophenes


Concept of epoxidation

• reaction faster with olefins than with (most) MOAH

• faster than with fatty acids

� peracid added at ~10 % of consumption by fatty acids

– reaction with fatty acids eliminates peracid

– fatty acids added if not present

– cooling enhances selectivity

• nevertheless: 15-30 % lossof MOAH


0

20

40

60

80

100

0 50 100 150 200

Amount mCPBA (mg)

Pre

sen

ce r

ela

ted

to

in

itia

l

co

ncen

trati

on

(%

)

Fluorene, phenanthrene, chrysene

MOAH

Dibenzothiophene

SterenesSqualene

50 °C 20 °/min 350 °C50 °C 20 °/min 350 °C

6B

BP

TBB

9B

Sq

ua

lene

Ste

renes

Ca

rote

no

ids

Sq

ua

lene

Mineralaromatics

Ste

renes

No epoxidation

25 mg mCPBA/300 mg oil

100 mg mCPBA/300 mg oil

Margarine Rapeseed oil

100 mg/kg

15 mg/kg

no epoxidation

25 mg peracid

100 mg peracid

MOAH

Sample enrichment for MOAH

• lower concentration than MOSH: enrichment frequently necessary

• elimination of lipids

• MOAH must pass into fraction

• 12 g silica gel to retain 1 g of oil or fat

• 20 % dichloromethane/hexane

• enrichment by factor 50


Safflower oil Rapeseed oil

by epoxidation anddirect HPLC-GC-FID

after enrichment

50 °C 20 °/min 350 °C 50 °C 20 °/min 350 °C

MOSH

Wa

x es

ters

5.5 mg kg-1

2.5 mg kg-1

30 mg kg-1

55 mg kg-1

1214 16

3 mg kg-1

6B

BP TBB9B

1 mg kg-1

0.2 mg kg-1

MOSH

MOAH

MOAH

epoxidized, direct

enriched

after epoxidation; no enrichment

21

2325 31

Sq

uale

ne

Sq

uale

ne

direct analysis

MOAH enriched and epoxidized

50 °C 20 °/min 350 °C

4 mg kg-1

55 mg kg-1

320 mg kg-1

21 mg kg-1

12 1416

3 mg kg-1

1 mg kg-1

6B

BP

TBB

9B

0.2 mg kg-1

Refined olive oil Olive pomace oil

MOSH

MOAH

MOAH

21 mg/kg320 mg/kg

55 mg/kg

4 mg/kg

direct

epoxidized, direct

epoxidized, enriched

Characterization of MOAH

• MOAH are alkylated to 95 to >99 % � extremely complex mixture

– PAH from pyrolysis are little alkylated

– analysis not by individual components � group type

– no calibration by MS or spectroscopic detectors � FID


Na

ph

tha

len

e

C1

-Na

ph

tha

len

es

Naphthalenes 8.2 % of thebatching oil

Dibenzothiophenes 3.1 %

Jute batching oil;

preseparation by NPLC

(amino silica), LC-GC

(M. Biedermann, 1991)

LC-solvent evaporator-LC-(GC)

LC column 1 LC-column 2Solvent evaporator

(SE)

UV detector

GC system

FID

- Reduction of the fraction volume

- Exchange of the eluent

Va

cu

um

Sabrina Moret, K. Grob, and L.S. Conte, J. Chromatogr. 750 (1996) 361-368


Linseed oilcontaminated from

jute bag

LC-SE-LC-UV


Analysis by GCxGC

60 °C 360 °C5 °/min

30

25

20

15

1st dimension GC

2n

d d

ime

nsio

n G

C (

s)

0

1

2

3

4

60 °C 360 °C5 °/min

1st dimension GC

3035

45

40

25

20

Crude fraction for lubricating oilBatching oil

GC-FID (no modulation)

GCxGC-FID(modulated)

30252015

403520 25 30

Paraffins

Aromatics


Separation by ring number

B

Phe + An

BT

DBT

BDBT

N

ChryBPy

Flu + Py

Fluo

Benzenes

2-Rings

3-Rings

4-Rings

5-Rings

2n

d d

imen

sio

n G

C (

s)

1

2

3

4

1st dimension GC

TAS

80 °C 305 °C

5 °/min


Lubricating oil

DAE extender oil

Extender oil from handle

Tar from wood furnace

5-Rings

4-Rings

3-Rings

2-Rings

Benzenes

Per

BP

6B TBB

9B

5-Rings

4-Rings

3-Rings

2-Rings

Benzenes

5-Rings

4-Rings

3-Rings

2-Rings

Benzenes

5-Rings

4-Rings

3-Rings

2-Rings

Benzenes

Per

Per Per


Quantitative estimation by integration of grid of 2nd dimension chromatograms

BP

6B TBB

9B

5-Rings4-Rings

3-Rings

2-Rings

Benzenes

1st dimention GC retention times (min) 1 2 3 4

2nd dimension GC (s)

20

25

30

35

40

45

50

55

512 3

4

1

2

34

1

1

23

51 2 3 4

51 2 3 4

2

3 4

1

20 25 30 35 40 45 50 55

Per

Squalene

Sterenes

Contaminated crude Ukrainian sunflower oil


exam

ple

BP

6B TBB

9B

5-Rings4-Rings

3-Rings

2-Rings

Benzenes

1st dimention GC retention times (min) 1 2 3 4

2nd dimension GC (s)

20

25

30

35

40

45

50

55

512 3

4

1

2

34

1

1

23

51 2 3 4

51 2 3 4

2

3 4

1

20 25 30 35 40 45 50 55

Per

Squalene

Sterenes

Contaminated crude Ukrainian sunflower oil


exam

ple

Time 1 ring 2 rings 3 rings 4 rings 5 rings

(min) (% referring to aromatics)

25 0.5 0.2 0.1 0.0 0.0

30 1.6 0.8 0.9 0.0 0.0

35 4.9 4.5 4.2 1.4 0.0

40 8.7 9.0 12.1 5.8 0.3

45 5.3 7.0 9.5 7.4 1.3

50 2.6 2.7 3.1 2.9 1.0

55 0.5 0.4 0.4 0.6 0.3

Sum 24.0 24.7 30.3 18.1 2.8

Benzenes

Naphthalenes + Benzothiophenes

Fluorenes

3-Ring compounds

4-Ring compounds

MOAH

1

2

3

2nd

dim

ensio

n G

C (

s)

1st dimension GC

90 °C 280 °C5 °/min

Benzenes

2-Ring compounds

3-Ring compounds

4-Ring compounds

Per

6B BP

TBB

9B

Per

Mineral oil for printing newspaper

Crude oil (jutebatching oil)

Oil for printing inks

partly hydrogenated


4-Rings

other 3-RingsFluorenes

2-Rings

Benzenes

4-Rings

other 3-RingsFluorenes

2-Rings

Benzenes

ISIS

IS

ISISIS

IS

IS

IS

ISBatching oil

Newspaper

MOAH

Attachments

Method proposed during EU workshop 2008

in Zürich

• 6 ml glass tube

• 2 g silica gel activated 400 °C/overnight (dry packing)

• 250 mg fat or oil loaded onto column

– option: epoxidation for better removal of olefins

• 3 ml of eluate

• 50 µl injection

• GC-FID


Silica gel versus aluminum oxide- does not retained n-alkanes- has a higher capacity to retain oil� doubled sample concentration

Techniques for large volume injection

• On-column– classical retention gap technique: 50 µl

– with vapor exit: 100-1000 µl

• PTV (programmed temperature vaporizing)– splitless: 30 µl

– solvent splitting: up to 500 µl

• Conventional splitless injection– concurrent solvent recondensation: 50 µl

– with vapor exit: 250 µl


1. On-column or PTV injector

2. Deactivated uncoated precolumn…

8 m x 0.32 mm i.d. or

5 m x 0.53 mm ID

3. …coupled to separation column by press-fit

4. Oven temperature closely below pressure-corrected solvent boiling point

estimated maximum: standard boiling point + 1 °/10 kPa

5. Oven program started at end of solvent evaporation (end of solvent peak), some 2-4 min after injection

6. Injection rate 5 µl/s

Rules for 50 µl on-column injection


Rules for LV-CSR splitless injection

• Uncoated precolumn

– 8 m x 0.32 mm i.d. or

– 5 m x 0.53 mm i.d.

• Injector liner with 1 cm plug deactivated glass wool

– slightly above column entrance

– column entrance near bottom of vaporizing chamber

• Injector temperature suitable for solutes (370 °C)

• Column temperature closely below the pressure-corrected solvent boiling point estimated as b.p. + 1 °/10 kPa

• Fast injection with short needle

• Temperature program started after end of solvent evaporation (end of solvent peak)

• Duration of splitless period: 3-4 min

– warming up of evaporation site

Con

cu

rre

nt

so

lven

t re

con

den

sa

tio

nla

rge

sam

ple

vo

lum

esplit

less

inje

ctio

n.

P.

Ma

gn

i an

d T

. P

orz

ano

. J.

Sep.

Sci. 1

7 (

20

03

) 1

491

-149

8

La

rge

vo

lum

e s

plit

less

inje

ctio

n w

ith

con

cu

rren

t so

lven

t re

cond

en

sa

tion

: keep

ing t

he

sa

mp

le in

pla

ce

in

th

e h

ot

va

po

rizin

g c

ha

mber.

M.

Bie

de

rman

n,

A.

Fis

ca

lini an

d K

. G

rob

. J.

Sep

. S

ci. 2

7 (

20

04

) 1

157

-1165


Epoxidation to enhance retention of olefins

1. Precisely weigh ca. 250 mg fat or oil into 4.5 ml vial with screw cap

2. add 1-1.5 ml chloroform

3. add 1 µl IS solution/10 mg sample (e.g. 25 µl/250 mg)

4. add ∼ 50 mg 3-chloroperbenzoic acid

5. close vial and shake; all should be dissolved (add more chloroform otherwise)

6. reaction: 30 min at RT

7. wash with 1-1.5 ml 10 % sodium sulfite; discard upper phase

8. wash with 1-1.5 ml 10 % sodium bicarbonate; discard upper phase

9. wash with 1-1.5 ml water; discard upper phase

10. transfer chloroform phase to 1.5 ml vial and remove chloroform by flow of nitrogen

11. add 250 µl hexane and transfer to column…


Peak area: option 1, integration

20

29

23

1. Integration of all peaks• straight baseline

• baseline from blank chromatogram

2. Integration of peaks on top of the hump

3. Mineral oil = difference

integrated range


Option 2: approximation by triangle(s)

20

29

23

Baseline from a blank chromatogram

1. Measure area of hump forcalibration in mm2

F= (b*h)/2

2. Do the same for the sample;use the same attenuation!

3. n-Alkanes considered byadding to the triangle

b

h


Method

• 20 % oil in hexane: 300 mg/1.5 ml autosampler vial

• 100 µl injection

• LC: 300 µl/min hexane– purified through aluminium oxide, redistilled

• Column 1: 25 cm x 2 mm i.d. Spherisorb Si 5 µm

• Column 2: 25 cm x 2 mm i.d. Lichrospher Si 60 5 µm

• Backflush of column 1 with 1 ml MTBE after 3 min (4 min)

• GC oven during transfer: 60 °C (7.5 min)

• Carrier gas inlet pressure: 50 kPa (hydrogen)– during transfer: 25 kPa

• Solvent vapor exit closed: 4.4 min

• Temperature program rate, 25 °C/min to 360 °C


Lower detection limit: off-line enrichment

• e.g. for determining environmental contribution

• requires

– more fat/oil

– removal of plant n-alkanes

• 7 g activated silica gel

– capacity for 1 g fat

• 20 g activated aluminium oxide

– retention of 2 mg n-alkanes

• 25 ml fraction with hexane

• analyzed by on-line LC-GC

• detection limit <0.5 mg/kg

Alu

min

um

oxid

eS

ilica g

elRetention of fat

(triglycerides)

Retention of unsaturated hydrocarbons

Retention of long chain n-alkanes



Blank

Motor oil

100 % CH Cl2 2

100 % hexane

Backflush, 500 µL min -1

300 µL min -1

Fra

ctio

n o

f th

e M

OS

H

Fra

ctio

n o

f th

e M

OA

H

HPLC

Saturates (MOSH)

Aromatics (MOAH)

30 % CH C2 2l

Per

12

1416

6B

BP9P

TBB

Cho

Per

GC-FID

Reconditioning, 500 µL min -1

J.

Agric.

Food C

hem

. 57 (

20

09)

8711-8

72

1

References• Coupled LC-GC: Capacity of Silica Gel (HP)LC Columns for Retaining Fat. Grob, I. Kälin, and A. Artho. J. High Resol.

Chromatogr. 14 (1991) 373-376.• LC-GC analysis of the aromatics in a mineral oil: batching oil for jute bags. K. Grob, M. Biedermann, A. Caramaschi, and B.

Pacciarelli. J. High Resol. Chromatogr. 14 (1991) 33-39.• On-line HPLC (LC)-solvent evaporation (SE)-LC-capillary GC-FID for the analysis of mineral oil polyaromatic hydrocarbons in

fatty foods. S. Moret, K. Grob, and L.S. Conte. J. Chromatogr. 750 (1996) 361-368.• Mineral Oil Polyaromatic Hydrocarbons in Foods, e.g. from Jute Bags, by on-line LC-Solvent Evaporation (SE)-LC-GC-FID. S.

Moret, K. Grob, and L.S. Conte. Z. Lebensm. Unters. Forsch. 204 (1997) 241-246.• Determination of mineral paraffins in feeds and foodstuffs by bromination and preseparation on aluminium oxide: method and

results of a ring test. Ch. Wagner, H.-P. Neukom, V. Galetti and K. Grob. Mitt. Lebensm. Hyg. 92 (2001) 231-249.• Mineral paraffins in vegetable oils and refinery by-products for animal feeds. Ch. Wagner, H.-P. Neukom, K. Grob S. Moret, T.

Populin, and L. S. ConteMitt. Lebensm. Hyg. 92 (2001), 499-514.

• Food contamination by C20-C50 mineral paraffins from the atmosphere. H.-P. Neukom, K. Grob, M. Biedermann, A. Noti. Atmospheric Environment 36 (2002) 4839-4847.

• Occurrence of C15-C45 mineral paraffins in olives and olive oils. S. Moret, T. Populin, L. S. Conte, K. Grob and H.-P. Neukom. Food Additives and Contaminants 20 (2003) 417-426.

• Exposure of babies to C15-C45 mineral paraffins from human milk and breast salves. A. Noti, K. Grob, M. Biedermann, U. Deiss, B. J. Brüschweiler. Regulatory Toxicology and Pharmacology 38 (2003) 317-325.

• Mineral oil paraffins in human body fat and milk. N. Concin, G. Hofstetter, B. Plattner, C. Tomovski, K. Fiselier, K. Gerritzen, S. Fessler, G. Windbichler, A. Zeimet, H. Ulmer, H. Siegl, K. Rieger, H. Concin, K. Grob. Food and Chemical Toxicology, 46 (2008) 544-552.

• Contamination of grape seed oil with mineral oil paraffins. D. Fiorini, K. Fiselier, M. Biedermann, R. Ballini, E. Coni, and K. Grob. J. Agric. Food Chem. 58 (2008) 11245-11250.

• Activated aluminum oxide selectively retaining long chain n-alkanes. Part I, description of the retention properties. K. Fiselier, D. Fiorini, K. Grob. Analytica Chimica Acta 634 (2009) 96–101.

• Activated aluminum oxide selectively retaining long chain n-alkanes. Part II, integration into an on-line HPLC-LC-GC-FID method to remove plant paraffins for the determination of mineral paraffins in foods and environmental samples. K. Fiselier, D. Fiorini, K. Grob. Analytica Chimica Acta 634 (2009) 102–109.

• How "white" was the mineral oil in the contaminated Ukrainian sunflower oils? M. Biedermann, K. Grob. Eur. J. Lipid Sci. Technol. 111 (2009) 313–319

• Determination of mineral oil paraffins in foods by on-line HPLC–GC–FID: lowered detection limit; contamination of sunflower seeds and oils. K. Fiselier, K. Grob. Eur. Food Res. Technol. 229 (2009) 679–688

• Aromatic hydrocarbons of mineral oil origin in foods: method for determining the total concentration and first results. M. Biedermann and K. Grob. J. Agric. Food Chem. 57 (2009) 8711-8721

• Comprehensive two-dimensional GC after HPLC preseparation for the characterization of aromatic hydrocarbons of mineral oil origin in contaminated sunflower oil. M. Biedermann and K. Grob. J. Separation Science (in press)

• Is recycled newspaper suitable for food contact materials? Technical grade mineral oils from printing inks. M. Biedermann, K. Grob. Eur. Food Res. Technol. (submitted)

Documents

Mineral oils in vegetable oils: tools for the analysis of