Direct determination of MCPD fatty acid esters and glycidyl fatty acid esters in vegetable oils by LC-TOFMS

Article abstract of DOI:10.1007/s11746-010-1732-5

Analysis of MCPD esters and glycidyl esters in vegetable oils using the indirect method proposed by the DGF gave inconsistent results when salting out conditions were varied. Subsequent investigation showed that the method was destroying and reforming MCPD during the analysis. An LC time of flight MS method was developed for direct analysis of both MCPD esters and glycidyl esters in vegetable oils. The results of the LC-TOFMS method were compared with the DGF method. The DGF method consistently gave results that were greater than the LC-TOFMS method. The levels of MCPD esters and glycidyl esters found in a variety of vegetable oils are reported. MCPD monoesters were not found in any oil samples. MCPD diesters were found only in samples containing palm oil, and were not present in all palm oil samples. Glycidyl esters were found in a wide variety of oils. Some processing conditions that influence the concentration of MCPD esters and glycidyl esters are discussed.

Full text of DOI:10.1007/s11746-010-1732-5

J Am Oil Chem Soc (2011) 88:1–14
DOI 10.1007/s11746-010-1732-5
ORIGINAL PAPER
Direct Determination of MCPD Fatty Acid Esters and Glycidyl
Fatty Acid Esters in Vegetable Oils by LC–TOFMS
•
Troy D. Haines Kevin J. Adlaf Robert M. Pierceall
•
•
•
Inmok Lee Padmesh Venkitasubramanian
•
Mark W. Collison
Received: 19 May 2010 / Revised: 9 November 2010 / Accepted: 18 November 2010 / Published online: 9 December 2010
Ó The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Analysis of MCPD esters and glycidyl esters in
vegetable oils using the indirect method proposed by the
DGF gave inconsistent results when salting out conditions
were varied. Subsequent investigation showed that the
method was destroying and reforming MCPD during the
analysis. An LC time of flight MS method was developed
for direct analysis of both MCPD esters and glycidyl esters
in vegetable oils. The results of the LC–TOFMS method
were compared with the DGF method. The DGF method
consistently gave results that were greater than the LC–
TOFMS method. The levels of MCPD esters and glycidyl
esters found in a variety of vegetable oils are reported.
MCPD monoesters were not found in any oil samples.
MCPD diesters were found only in samples containing
palm oil, and were not present in all palm oil samples.
Glycidyl esters were found in a wide variety of oils. Some
processing conditions that influence the concentration of
MCPD esters and glycidyl esters are discussed.
Introduction
Edible oils are subjected to processing to improve quality,
stability, and safety. Although, processing edible oils
removes a very large portion of impurities from the oil,
improved analytical methods have occasionally discovered
compounds not previously known to be present in oil.
Monochloropropanediol (MCPD) and MCPD esters
were known to form from glycerol released from triacyl-
glycerols treated with hydrochloric acid at least as early as
1980 [1–3]. Treatment of triacylglycerols and phospho-
lipids with aqueous hydrochloric acid was shown to cause
formation of monochloropropanediol [4].
MCPD was identified in technical grade monostearate
in a report by the British Food Standards Agency [5]. The
monostearate was hypothesized to have been made by
hydrolysis of oil with hydrochloric acid. This report also
indicated that 3-MCPD was unstable above pH 6.0.
According to a recent report from the International
Life Sciences Institute, ILSI [6], ‘‘3-MCPD esters are
formed at high temperatures during the refining of edible
fats and oils, mainly during the deodorization step. The
proposed mechanism for the formation of 3-MCPD esters
involves the formation of a cyclic acyloxonium ion from
triacylglycerol, followed by reaction with chloride ions
and formation of 3-MCPD esters. The main factors for
the formation of 3-MCPD esters are the presence of
chloride ions, glycerol, tri-, di- or monoacylglycerides, as
well as temperature and time. In particular, increasing
amounts of mono- and diacylglycerides in the oil show
a linear correlation with the increased formation of
3-MCPD esters.’’
Keywords Monochloropropanediol Á MCPD Á Glycidol Á
Glycidyl esters Á LC–TOFMS Á Vegetable oil
Abbreviation
MCPD monochloropropanediol
T. D. Haines Á K. J. Adlaf Á R. M. Pierceall Á I. Lee Á
P. Venkitasubramanian Á M. W. Collison (&)
Research Division, Archer Daniels Midland Company,
James R. Randall Research Center, 1001N. Brush College Road,
Decatur, IL 62521, USA
The formation of MCPD from glycerol has been
described as proceeding via a protonated 2,3-epoxy-1-
propanol (glycidol) intermediate, with catalysis by a
e-mail: Mark.Collison@adm.com
123

2
J Am Oil Chem Soc (2011) 88:1–14
carboxylic acid such as a free fatty acid [7]. In the absence
of catalyst, no glycerol was converted to MCPD.
´
Zelinkova et al. [8] surveyed 25 virgin and refined
It is clear to us that a direct analysis method, free from
the artifacts caused by transesterification chemistry, is
needed. The method presented here was developed to allow
determination of MCPD fatty acid esters (MCPDE) and
glycidyl fatty acid esters (GE) in vegetable oils without
derivatization reactions or harsh chemical treatment that
might produce MCPD not originally present in the sample.
To meet this need, a method using HPLC–time of flight
mass spectrometry (LC–TOFMS) was developed that
required no harsh chemicals prior to analysis and that had
adequate detection limits for MCPDE and GE in the samples.
vegetable oils for MCPD. They used a direct extraction
procedure without harsh chemical treatment for determi-
nation of free MCPD and found very low levels. After
extraction and drying, the residue was derivatized with
phenylboronic acid and 3-MCPD phenylboronate esters
´
were analyzed according to the procedure of Divinova
et al. [9]. They used a harsh acid methanolysis procedure
for determination of bound MCPD, using concentrated
sulfuric acid in methanol at 40 °C for 16 h and found high
levels of bound MCPD in all samples.
Weißhaar [10] showed that the acid methanolysis pro-
´
cedure of Zelinkova et al. [8] produced incorrectly high
Experimental Procedures
MCPD values when chloride was added and showed that a
base catalyzed methanolysis procedure using sodium
methoxide in methanol produced much lower results. This
paper also showed that recovery of the internal standard
with this procedure averaged about 63%. This procedure
has subsequently been widely accepted as the method of
choice for MCPD analysis in vegetable oils and has been
incorporated into a method by the Deutsche Gesellschaft
fu¨r Fettwissenschaft (DGF; German society for fat sci-
ence) [11]. That method uses transesterification with
sodium methoxide followed by acidification with acetic
acid and partitioning into hexane with highly concentrated
sodium chloride solution (200 g/L) to determine ‘‘total
content of ester-bound 3-MCPD and glycidol’’ and uses a
second determination where the sample is first reacted
with sulfuric acid in propanol to destroy any glycidol
present in the sample, followed by the reaction with
sodium methoxide. The difference between these two
analyses is used as an indirect measure of glycidol content
of the sample. This method will be referred to as the DGF
Method.
Reagents
HPLC-grade methanol and high resolution GC-grade
methylene chloride were purchased from Fisher Scientific
(Pittsburgh, PA, USA). HPLC-grade acetonitrile was from
EMD Chemicals, Inc. (Gibbstown, NJ, USA). ACS
Reagent-grade sodium acetate was from Sigma-Aldrich
(St. Louis, MO, USA).
Mixed Distilled Fatty Acids
A mixture of distilled fatty acids (Archer Daniels Midland
Company, Decatur, IL, USA) was used in several synthe-
ses. The composition of the mixture is shown in Table 1.
Standards
3-MCPD monopalmitate, 3-MCPD monostearate, 3-MCPD
dipalmitate were purchased from Toronto Research
Chemicals, Inc (North York, ON, Canada).
Glycidyl stearate was purchased from TCI America
(Portland, OR, USA). Glycidyl linolenate, glycidyl linole-
ate, glycidyl oleate and glycidyl palmitate were purchased
from Wako Pure Chemical Industries (Tokyo, Japan).
Deuterated 3-MCPD diolein was prepared by reacting
30.7 g oleic acid (99%? , Nu Chek Prep, Inc., Elysian,
MN) with 5.07 g deuterated 3-MCPD ( -3-chloro-1,2-
propane-d5-diol, 98 atom %D, C/D/N Isotopes Inc, Pointe-
Both the acid and the base procedures use harsh chem-
icals which may alter MCPD concentration. Acid catalyzes
the formation of MCPD from chloride and, even though
sulfuric acid is used, chloride in the samples could result in
synthesis of MCPD during the treatments, as shown by
Weißhaar [10]. The procedure Weißhaar proposes using
sodium methoxide also has problems in that base catalyzed
reactions can degrade MCPD, as it is reported not to be
stable above pH 6.0 [5].
Table 1 Composition of mixed distilled fatty acids
The DGF Method employs two analyses before and after
an acid treatment that can destroy glycidol. It is assumed
that the analysis without acid treatment measures the total
of only glycidol plus MCPD and that the difference
between the analyses is due exclusively to glycidol.
We will present data that shows MCPD is destroyed
during the DGF method and that it is subsequently
re-synthesized during the extraction step of the procedure.
Fatty acid
Weight (%)
Linoleic
Oleic
48
38
7
Linolenic
Palmitic
Stearic
3.2
1.1
123

J Am Oil Chem Soc (2011) 88:1–14
3
Claire, Quebec, Canada) using 3.1 g Novozym 435 enzyme
(Novozymes, Vagsvaerd, Denmark) at 45 °C, under 5 Torr
vacuum, with vigorous agitation (450 rpm) for 70 h. There
was 25% excess oleic acid on a molar basis. After cooling
to room temperature, 150 mL hexane was added to the
reaction mixture and it was filtered through #40 filter paper
(Whatman Inc., Florham Park, NJ) to remove the enzyme.
The filtrate was transferred to a 500-mL separatory funnel,
18 mL of 95 g/L NaOH solution was added and the mix-
ture was shaken for 3 min for neutralization. After removal
of the lower soap phase, the upper phase was washed
several times with 100 mL warm water until the pH of the
wash water became neutral. Hexane was evaporated in a
rotary evaporator and then by mechanical vacuum pump to
completely remove residual hexane and moisture. After
hexane removal, 20.6 g product was recovered. The fin-
ished material had less than 0.1% free fatty acid by titration
and contained [95% deuterated 3-MCPD diesters of oleic
acid.
Table 2 Mixed MCPD diesters from distilled mixed fatty acids
Diester forms
Total diester (%)
OL LO
LL
38.5
24.3
15.3
7.1
OO
LLn LnL
OLn LnO
PL LP
PO OP
SL LS
SO OS
LnLn
5.6
3.2
2.6
1.1
0.88
0.52
0.47
0.16
0.11
0.074
0.013
PLn LnP
SLn LnS
PP
PS SP
SS
P palmitic acid, S stearic acid, O oleic acid, L linoleic acid, Ln lin-
olenic acid
A similar procedure was used to make the diesters of
oleic acid. 3-MCPD from Sigma-Aldrich (98%, St. Louis,
MO, USA) was used. The reaction time was 65 h, 14.5 g
finished material was recovered after hexane removal, and
it contained 0.86% free fatty acids.
product were recovered. The finished material had 2.7%
free fatty acid, by titration.
A similar procedure was used to synthesize 3-MCPD
monoesters of oleic acid. Pure oleic acid from Nu Chek
Prep was used, the reaction time was 45 min. The reaction
formed a heavy emulsion that was difficult to break. One
gram of finished product was recovered and it contained
9.6% free fatty acid.
A similar procedure was used to make the diesters of
linoleic acid. Linoleic acid (99%? , Nu Chek Prep, Inc.,
Elysian, MN) esterified faster than oleic acid, the reaction
time was 40 h, 17.6 g finished material was recovered after
hexane removal, and it contained 0.25% free fatty acid.
A similar procedure was used to produce MCPD diesters
of Mixed Distilled Fatty Acids. Mixed Distilled Fatty
Acids (ADM; Table 1) were used for the synthesis, the
reaction time was 64 h, 21.7 g finished material was
recovered after hexane removal, and it contained 0.1% free
fatty acid. Composition of the MCPD diesters of mixed
fatty acids expected from the reaction is shown in Table 2
MCPD monoesters of mixed distilled fatty acids were
synthesized by mixing 28.2 g mixed distilled fatty acids
and 14.5 g 3-MCPD (25% excess fatty acids on molar
basis) with Novozym 435 enzyme at 50 °C, under 5 Torr
vacuum, with vigorous agitation (450 rpm) for 2 h. After
cooling to room temperature, 150 mL hexane was added to
the reaction mixture and it was filtered through #40 filter
paper to remove the enzyme granules. The filtrate was
transferred to a 500-mL separatory funnel, 18 mL of 95 g/L
NaOH solution was added and the mixture was shaken for
3 min for neutralization. After removal of the lower soap
phase, the upper phase was washed several times with
100 mL warm water until the pH of the wash water became
neutral. Small portions of methanol were used to break
emulsions. Hexane and moisture were evaporated in a
rotary evaporator and then by mechanical vacuum pump to
insure complete removal. After hexane removal, 11 g of
Glycidyl esters of fatty acids were produced enzymati-
cally by two slightly different procedures and by a chem-
ical procedure.
Glycidyl esters of mixed distilled fatty acids were syn-
thesized from glycidol and free fatty acids as follows.
70.5 g mixed distilled fatty acids (25% excess fatty acids on
molar basis) and 14.8 g glycidol (96%, Sigma, St. Louis,
MO) were reacted with 7 g Novozym 435 at 46 °C with
vigorous agitation (450 rpm) for 14 h. Because of the vol-
˚
atility of glycidol, molecular sieves (3 A, MT-3A48HMS,
Shanghai Hengye Chemical, Shanghai, China) were used
instead of vacuum to remove the moisture formed during
the esterification. The reaction mixture was filtered through
Reeve Angel 230 filter paper (Whatman Inc., Florham Park,
NJ). The filtrate was mixed with 200 mL hexane and
washed with 200 mL warm water to remove residual
glycidol. The hexane phase was recovered. Hexane and
moisture were removed by rotary evaporation followed by
mechanical vacuum to insure complete removal. The fin-
ished material contained 23.5% free fatty acid.
Glycidyl esters were also synthesized using fatty acid
methyl esters of palmitic and oleic acids. First, 10 g of
methyl palmitate or methyl oleate (99%? , Nu Chek Prep,
123

4
J Am Oil Chem Soc (2011) 88:1–14
Inc., Elysian, MN) was mixed with 13.7 g glycidol (Sigma-
Aldrich, St. Louis, MO) and 1 g Novozyme 435. The
reaction mixture was then heated to 70 °C using an oil bath
and the reaction was driven to completion by sparging with
nitrogen to remove methanol formed during the reaction.
The reaction was stopped after 24 h. The reaction mixture
was diluted with ethyl acetate and filtered to remove the
immobilized enzyme. The solvent and excess glycidol were
removed in vacuo to give colorless oil that solidified upon
cooling (13 g). Five grams of this crude product mixture
were dissolved in hexanes and applied to a 200-mL column
of silica gel 60–200 mesh equilibrated with hexanes. The
column was washed with hexanes to elute unreacted
methyl esters. Glycidyl esters were eluted using a gradient
of 0–20% ethyl acetate in hexanes. The product, either
glycidyl palmitate or glycidyl oleate, eluted in the 5–10%
ethyl acetate fractions. Fractions containing the product
were pooled and concentrated in vacuo to give a white
solid (*2 g).
The glycidyl ester of fully deuterated palmitic acid was
synthesized by the following 2-step chemical procedure.
Synthesis of Allyl Palmitate-d31. A 100-mL round bot-
tom flask equipped with a magnetic stir bar and reflux
condenser was charged with palmitic acid-d31 (1 g,
3.47 mmol), allyl alcohol (0.5 mL, 6.95 mmol), toluene
(10 mL) and Amberlyst 15 (0.5 g). The reaction mixture
was stirred and heated to 110 °C in an oil bath and refluxed
for 24 h. The progress of the reaction was monitored by
TLC and 1H NMR. 1H NMR of the crude reaction mixture
showed the presence of an allyl ester. The reaction mixture
was diluted with hexanes (20 mL) and filtered to remove
Amberlyst 15. The reaction mixture was washed with water
(2 9 20 mL) and saturated sodium chloride (1 9 20 mL).
The solvent was dried over anhydrous Na2SO4 and con-
centrated in vacuo to give a colorless oil that solidified on
cooling. This was taken as such to the next step.
column (60–200 mesh, 100-mL bed volume) using gradient
elution (0–20% v/v) ethyl acetate in hexanes. The fractions
containing the glycidyl esters were pooled and concen-
trated to give a colorless oil (0.8 g) that solidified on
cooling.
Chemical Interesterification and GC–MS Analysis
of MCPD
The method of Weißhaar [10] and the DGF [11] for total
MCPD plus glycidol was used for the determination of
MCPD using chemical interesterification. Briefly, about
100 mg of sample was weighed into a screw-capped test
tube, and dissolved in 0.5 mL of MTBE : ethyl acetate 8:2,
100 lL of internal standard solution (solution of 3-MCPD-
d5, ca. 20 mg/mL in MTBE) and 1 mL of NaOCH3-solu-
tion (0.5 mol/L in methanol) was added, the tube was
closed tightly and allowed to stand 10 min at room tem-
perature. After 10 min, 3 mL isohexane, 0.100 mL glacial
acetic acid and 3 mL salt solution were added. Normally,
the salt solution was 200 g/L NaCl but other salt solutions
were used in certain studies, as indicated in the text. The
sample was shaken to mix, allowed to separate and the
upper organic layer was removed with a pipette and dis-
carded. The aqueous layer was extracted with a new por-
tion of 3 mL isohexane, the upper layer was again removed
and discarded. To the aqueous phase, 0.500 mL derivati-
zation reagent (2.5 g phenylboronic acid dissolved in
19 mL acetone and 1 mL water) was added. The tube was
closed and heated at 80 °C for 20 min. After cooling to
room temperature, the cyclic phenylboronate derivative of
3-MCPD was extracted by shaking with 3 mL hexane. The
hexane layer was separated and analyzed by GC–MS.
LC–TOFMS Conditions
Synthesis of Glycidyl (D31) Palmitate. A 100-mL round
bottom flask equipped with a magnetic stirring bar was
charged with allyl palmitate (1 g, 3.05 mmol) and dichlo-
romethane (15 mL). The reaction mixture was cooled in an
ice bath for 5–10 min and meta-chloroperbenzoic acid
(1.5 g, 6.1 mmol) was added in small amounts. After the
addition was complete, the reaction mixture was stirred and
allowed to warm slowly to room temperature over a 24-h
period. The progress of the reaction was monitored by TLC
and 1H NMR. After the reaction was complete, the reaction
mixture was diluted with hexanes (20 mL). The reaction
mixture was washed with aqueous sodium bisulfite [2%
(w/w), 20 mL] and aqueous sodium bicarbonate (10% w/w,
2 9 20 mL), water (1 9 20 mL) and aqueous saturated
sodium chloride (1 9 20 mL). The organic layer was dried
over anhydrous Na2SO4 and concentrated in vacuo to give
a colorless oil (1 g). The oil was purified on a silica gel
The TOFMS analysis was adapted from the diglyceride
analysis procedure of Callender et al. [12]. An Agilent
1200 Series Rapid Resolution gradient LC system con-
nected to an Agilent 6210 Time-of Flight Mass Spec-
trometer (TOFMS), upgraded to 4 GHz for high resolution
data acquisition and equipped with MassHunter software
was used for analysis of MCPDE and GE. HPLC separa-
tion was by non-aqueous reversed phase HPLC on a Phe-
˚
nomenex Luna C18 column, 100 A pore size, 50 9 3 mm,
3 lm. HPLC mobile phases were made up with sodium
acetate to provide sample ionization. A 0.26 mM metha-
nol–sodium acetate solution (MSA) was prepared by add-
ing 21.3 mg sodium acetate to one liter of methanol. HPLC
mobile phase A was prepared by mixing 100 mL MSA,
800 mL methanol and 100 mL acetonitrile. HPLC mobile
phase B was prepared by mixing 100 mL MSA, 800 mL
methylene chloride, and 100 mL acetonitrile. Initially
123

J Am Oil Chem Soc (2011) 88:1–14
5
Determination of Free Glycidol in Vegetable Oil
Samples
100%A was held for 5 min after injection, followed by a
linear gradient to 65%B over 10 min. A 100%B wash for
4 min was used to elute low polarity compounds (primarily
triglycerides), the column was returned to 100%A and
equilibrated for 5 min.
Free glycidol was determined by head space GC–MS using
a Shimadzu GC 2010 gas chromatograph with a QP2010
mass spectrometer (Shimadzu Scientific Instruments,
Columbia, MD, USA). Approximately 10 g of oil was
accurately weighed into a 20-mL head space vial and
incubated 30 min at 95 °C. Two mL of head space was
injected using a static headspace injector with the syringe
set to 100 °C. Just after injection, pressure on the column
was rapidly increased from initial conditions of
60–300 kPa and held for 0.5 min, then ramped back to
60 kPa. The GC column was a Zebron ZB Wax column
(Phenomenex, Torrance, CA, USA) 30 m long, 0.25 mm
internal diameter, 0.25 lm film thickness. The initial
temperature was 75 °C, held for 1 min, the temperature was
ramped at 7.5–150 °C/min, then ramped at 25–260 °C/min
and held for 2 min. Glycidol was detected by the retention
time using single ion monitoring at 44.05 m/z. The detec-
tion limit was 0.2 mg/kg (ppm).
An internal standard stock solution was prepared by
weighing approximately 20 mg of the deuterated 3-MCPD
diolein and 2 mg deuterated glycidyl palmitate into a
10-mL volumetric flask and diluting to volume with HPLC
mobile phase B. The approximate concentration was
2000 mg/L deuterated 3-MCPD diolein and 200 mg/L
deuterated glycidyl palmitate.
A sample dilution solution was prepared by transferring
0.100 mL of the internal standard stock solution into a
100-mL volumetric flask and diluting to volume with
HPLC mobile phase B. The approximate concentration was
2 mg/L deuterated 3-MCPD diolein and 0.2 mg/L deuter-
ated glycidyl palmitate. The injection volume was 5 lL,
the HPLC flow rate was 0.25 mL/min
The Agilent 6210 TOFMS was set for high resolution
(4 GHz) data collection. Electrospray ionization (ESI) was
used. The ionization voltage (Vcap) was 3500 V, the gas
temperature was 300 °C, the drying gas flow was 5 L/min,
the nebulizer pressure was 50 psi. TOFMS mass range was
set to 300–700 m/z, polarity was positive, centroid mass
spectra were collected in high resolution mode (4 GHz) at
a rate of 1.41 spectra/s.
Results and Discussion
Effect of Changing Salt Type on the Results
from the DGF Method
Please note that the DGF procedure used in all samples is
the ‘‘total’’ procedure that is claimed to measure MCPD
plus glycidol. No acid treatments to destroy glycidol were
used in any of the studies of the DGF procedure.
Sample Preparation
In a 12 9 32 mm HPLC sample vial, one drop of oil
(20–25 mg) was accurately weighed and 975 lL sample
dilution solution was added using a positive displacement
pipette and mixed thoroughly.
During use of the DGF method, we found problems with
recovery of the internal standard. We tested the method
with salts other than sodium chloride in the extraction step
to see what effect this was having on the procedure.
Table 4 shows the results of an experiment using an
MCPD standard. The standard containing MCPD and
MCPD-d5 internal standard was taken through the DGF
process in the absence of vegetable oil. The DGF method
was performed as written using 200 g/L sodium chloride in
the extraction, and was also performed substituting either
saturated sodium sulfate or 200 g/L sodium bromide in the
extraction. The standard and internal standard peaks lost
about two thirds of their intensity when the process was
performed with sodium chloride present compared to the
analysis of the standards without prior transesterification.
When sodium sulfate was used instead of sodium chloride,
there was an additional reduction of 90% or more in the
GC–MS peak area. When sodium bromide was substituted
for sodium chloride, brominated derivatives [monob-
romopropanediol (MBPD)] were produced from both the
MCPD standard and the MCPD-d5 internal standard.
TOFMS Detection of Analytes
Selected ion monitoring (SIM) centered on the exact mass
to 10-5 Da of the m/z of the sodiated adduct of the analyte
was used in the TOFMS detection. A narrow extraction
window was used to eliminate the background found in
some samples that interfered with detection of low levels of
certain MCPD diesters, particularly dilinoleyl MCPD and
linoleyl-oleyl-MCPD. This improved the signal to noise
ratio of these analytes and lowered the limit of detection.
On the Agilent TOFMS this was done by setting the left
and right m/z to 50 ppm in the mass extraction setup
( 0.033 Da).
The list of analytes, their formulas and the exact masses
of the sodiated adducts that were used for TOFMS detec-
tion by selected ion monitoring (SIM) are shown in
Table 3. Standards were analyzed for all listed analytes.
123

6
J Am Oil Chem Soc (2011) 88:1–14
Table 3 Analytes, formulas
and exact mass of sodiated
adducts for TOFMS detection
by selective ion monitoring
(SIM)
Compound
Formula
C19H36O3
m/z [M ? Na]?
Palmitic acid glycidyl ester
335.25567
363.28697
361.27132
359.25567
357.24002
366.45024
371.23234
399.26364
397.24799
395.23234
393.21669
635.47766
609.46201
661.49331
633.46201
659.47766
637.49331
663.50896
657.46201
661.49331
665.52461
653.43071
657.46201
655.44636
631.44636
659.47766
666.52469
Stearic acid glycidyl ester
C
C
C
C
21H40O3
21H38O3
21H36O3
21H34O3
Oleic acid glycidyl ester
Linoleic acid glycidyl ester
Linolenic acid glycidyl ester
Palmitic acid-d31 glycidyl ester internal standard
Palmitic acid MCPD monoester
Stearic acid MCPD monoester
C19H5D31O3
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
19H37ClO3
21H41ClO3
21H39ClO3
21H37ClO3
21H35ClO3
37H69ClO4
35H67ClO4
39H71ClO4
37H67ClO4
39H69ClO4
37H71ClO4
39H73ClO4
39H67ClO4
39H71ClO4
39H75ClO4
39H63ClO4
39H67ClO4
39H65ClO4
37H65ClO4
39H69ClO4
Oleic acid MCPD monoester
Linoleic acid MCPD monoester
Linolenic acid MCPD monoester
Palmitic acid–Oleic acid–MCPD diester
Di-palmitic acid MCPD Diester
Di-oleic acid MCPD diester
Palmitic acid–linoleic acid MCPD diester
Oleic acid–linoleic acid MCPD diester
Palmitic acid–stearic acid MCPD diester
Oleic acid–stearic acid MCPD diester
Di-linoleic acid MCPD diester
Linoleic acid–stearic acid MCPD diester
Di-stearic acid MCPD diester
Di-linolenic acid MCPD diester
Oleic acid–linolenic acid MCPD diester
Linoleic acid–linolenic acid MCPD diester
Palmitic acid–linolenic acid MCPD diester
Stearic acid–linolenic acid MCPD diester
MCPD-d5 di-oleic acid ester internal standard
C39H66D5ClO4
Table 4 MCPD standard plus
internal standard, processed by
the DGF method
GC–MS area counts of phenylboronate derivatives
Sample ID
MCPD-d5
MCPD
MBPD-d5
MBPD
48,118
ISTD ? Std (untreated)
ISTD ? Std ? NaCl
ISTD ? Std ? Na2SO4
ISTD ? Std ? NaBr
155,261
53,713
4,864
170,186
59,346
5,302
5,711
6,161
41,079
MBPD monobromopropanediol
Figure 1 shows the overlaid GC–MS total ion current
chromatograms from treated samples shown in Table 4.
Note the extreme decrease of the MCPD and MCPD-d5
peaks in samples where chloride was not added and the
appearance of the brominated forms.
samples are substantially reduced or eliminated in the
absence of sodium chloride.
Table 6 shows the effect of substituting sodium bromide
for sodium chloride in the analysis of vegetable oils. Once
again, the internal standard, MCPD-d5 and the MCPD
produced in the DGF procedure is either mostly or com-
pletely lost when sodium chloride is not present. When
sodium bromide is used, MBPD-d5 is found in the samples,
proving that it was formed by conversion of the MCPD-d5
internal standard from the chlorinated to the brominated
form. In this experiment, MCPD was found only in samples
that were incubated with chloride, only MBPD was found
in samples processed in the presence of bromide.
Table 5 shows the effect of substituting sodium sulfate
for sodium chloride in the analysis of vegetable oil sam-
ples. The MCPD-d5 internal standard was added to the
samples, MCPD values are those produced from the oils by
the DGF analytical procedure. The data clearly shows that
in the absence of sodium chloride, the MCPD-d5 internal
standard is either completely or nearly completely
destroyed by the DGF procedure. MCPD values in the oil
123

J Am Oil Chem Soc (2011) 88:1–14
7
Fig. 1 GC–MS TIC
chromatograms of DGF
procedure samples processed
with different salts present.
a DGF method using NaBr;
b DGF procedure with NaCl;
c DGF procedure with Na2SO4.
Peaks 1 MCPD-d5; 2 MCPD;
3 MBPD-d5; 4 MBPD
Table 5 Comparison of sodium
chloride and sodium sulfate in
the DGF method for vegetable
oil samples
MCPD-d5 GC–MS area
MCPD GC–MS area
Sodium chloride Sodium sulfate Sodium chloride Sodium sulfate
Palm stearine
RBD soy
2,743,461
2,873,546
3,042,333
2,915,739
1,764,198
1,418,326
1,385,577
ND
1,316,656
296,788
1,248,188
1,313,061
264,339
2,882,576
118,680
103,383
3,809,021
ND
142,956
304,444
276,105
ND
356,407
ND
Palm/soy blend
RBD soy
ND
RB palm olein
RBD palm olein
Palm kernel stearine
ND
ND
71,307
ND
ND
ND
Hydrogenated palm kernel olein 1,316,460
ND
25,000
208,429
ND
Crude palm oil
ISTD blank
2,481,477
1,704,685
1,304,732
ND
268,083
143,892
Check standard
1,052,039
90,996
ND not detected
Table 6 The effect of
3-MCPD-d5
3-MBPD-d5
3-MCPD
3-MBPD
substituting sodium bromide for
sodium chloride in the DGF
analysis of vegetable oil
Soy/palm blend #1 NaCl
Soy/palm blend #1 NaBr
Soy/palm blend #2 NaCl
Soy/palm blend #2 NaBr
Soy/palm blend #3 NaCl
Soy/palm blend #3 NaBr
Soy/palm blend #4 NaCl
Soy/palm blend #4 NaBr
RBD palm NaCl
653,696
ND
ND
ND
ND
613,122
ND
ND
ND
597,555
ND
1,450,981
ND
ND
586,702
ND
1,306,095
ND
630,800
ND
1,590,794
ND
588,550
ND
1,307,056
ND
684,877
ND
1,367,516
ND
617,797
ND
1,066,853
ND
663,686
ND
330,123
ND
RBD palm NaBr
616,085
ND
326,312
ND
RBD soy NaCl
662,067
ND
373,531
ND
RBD soy NaBr
619,409
341,145
ND not detected
Together, these experiments demonstrate that the DGF
procedure is not measuring MCPD in vegetable oil.
Instead MCPD, if present, is actually converted to an
activated intermediate that can subsequently react with
chloride to re-form MCPD. There is no evidence that
MCPD is the only compound capable of this activation
and subsequent reaction. In fact, when this work was
started, the presence of glycidyl esters, which also
convert to MCPD in the subsequent reaction, were not
mentioned. There are likely to be a wide variety of other
compounds that can undergo similar activation by the
harsh chemicals used in this procedure, which can sub-
sequently react with the sodium chloride used in the
DGF procedure to form MCPD, leading to incorrect and
artificially high predicted levels of MCPD using this
procedure.
123

8
J Am Oil Chem Soc (2011) 88:1–14
Direct Determination of MCPD Fatty Acid Esters
and Glycidyl Fatty Acid Esters Via LC–TOFMS
glycidyl ester of fully deuterated palmitic acid was used as
internal standard for analysis of all glycidyl esters.
Figure 3 shows the overlaid SIM chromatograms for the
MCPD monoesters of palmitic, stearic, oleic, linoleic and
linolenic acid. The method limit of detection is approxi-
mately 15 lg/kg for each of the oleic, linoleic and linolenic
monoesters and is about 60 lg/kg for the palmitic and
stearic monoester standards. The glycidyl ester of fully
deuterated palmitic acid was used as internal standard for
analysis of all MCPD monoesters.
Given the problems found with the DGF procedure, we
decided to attempt to develop a method for direct deter-
mination of MCPD esters and glycidol esters in vegetable
oil.
Early attempts to determine MCPD mono- and diesters
by LC–MS showed that MCPD diesters would not ionize
sufficiently using conventional electrospray ionization
(ESI) or atmospheric pressure chemical ionization (APCI)
techniques to provide adequate analysis. Addition of
sodium to the HPLC mobile phase, using the method of
Callender et al. [12] allowed efficient ESI and detection of
the sodiated adducts.
Overlaid SIM chromatograms for MCPD diesters are
shown in Figs. 4 and 5. The method limit of detection for
MCPD diesters ranged from 4 to 10 lg/kg for diesters
containing at least one polyunsaturated fatty acid to 25 lg/
kg for diesters containing only saturated or monounsatu-
rated fatty acids. The di-oleic acid ester of MCPD-d5 was
used as the internal standard for analysis of all MCPD
diesters.
Attempts to run MS–MS techniques on sodiated
adducts of GE and MCPDE resulted in no useful prog-
eny from the parent sodiated ions. Time of flight mass
spectroscopy allowed highly sensitive detection of the
compounds of interest using single ion monitoring (SIM),
and the limit of detection could be improved by nar-
rowing the detection window to eliminate background
interferences.
Figure 6 shows a typical standard curve for glycidyl
stearate. Calibrations were linear for about 2 orders of
magnitude for all analytes and became non-linear at higher
concentrations, as is typical for LC–MS procedures.
Table 7 shows the limits of detection of the various
analytes in vegetable oil prepared as described in the
method (*40-fold dilution). A sample of RBD vegetable
oil that was below the limit of detection for all analytes was
spiked with increasing amounts of standards until a peak
Figure 2 shows overlaid SIM chromatograms for the
glycidyl esters of palmitic, stearic, oleic, linoleic and lin-
olenic acid. The method limit of detection is approximately
3 lg/kg for each of the glycidyl ester standards. The
Fig. 2 Overlaid SIM
chromatograms of glycidyl fatty
acid ester standards. 1 444 lg/
kg glycidyl linolenate, 2 478
lg/kg glycidyl linoleate,
3 568 lg/kg glycidyl oleate,
4 571 lg/kg glycidyl palmitate,
5 485 lg/kg glycidyl stearate
123

J Am Oil Chem Soc (2011) 88:1–14
9
Fig. 3 Overlaid SIM
chromatograms of MCPD
monoester standards.
1 1,516 lg/kg MCPD
monolinolenate, 2 1,0396 lg/kg
MCPD monolinoleate,
3 1,2730 lg/kg MCPD
monooleate, 4 5,693 lg/kg
MCPD monopalmitate,
5 2,338 lg/kg MCPD
monostearate
Fig. 4 Overlaid SIM
chromatograms of high
concentration MCPD diester
standards prepared from mixed
distilled fatty acids. 1 2,022 lg/
kg MCPD linoleic–linolenic
diester, 2 6,935 lg/kg MCPD
linoleic–linoleic diester,
3 1,0931 lg/kg MCPD oleic–
linoleic diester, 4 7,180 lg/kg
MCPD palmitic–palmitic
diester, 5 4,347 lg/kg MCPD
oleic–oleic diester
approximately 3 times the height of the noise could be
detected.
The content of glycidyl esters and MCPD esters found in
various oils purchased from local supermarket or from
commercial suppliers are shown in Table 8. Note that
MCPD monoesters were not found. While we have seen
MCPD monoesters occasionally in samples produced by
laboratory experiments, MCPD monoesters have not been
For all classes of compounds, analysis of repeated
preparation of samples on multiple days generally resulted
in relative standard deviations of 5–10% at analyte con-
centrations of 1–5 ppm.
123

10
J Am Oil Chem Soc (2011) 88:1–14
Fig. 5 Overlaid SIM
chromatograms of low
concentration MCPD diester
standards prepared from mixed
distilled fatty acids. 1 147 lg/kg
MCPD linolenic–linolenic
diester, 2 924 lg/kg MCPD
palmitic–linoleic diester,
3 732 lg/kg MCPD palmitic–
oleic diester, 4 251 lg/kg
MCPD oleic–stearic diester
Fig. 6 Standard curve for
glycidyl stearate showing
linearity over 2 orders of
magnitude
detected in any commercial deodorized oil sample. MCPD
diesters were found only in commercial oil samples con-
taining palm oil, no detectable MCPD esters were found in
other samples of commercial vegetable oil products. Lab-
oratory experiments have occasionally produced MCPD
diesters in other types of oils.
of glycidyl esters found in the oil, as shown in Fig. 7. The
concentration of total glycidol esters found in the oil is
lower than 5 mg/kg when diglyceride content of the oil is
lower than 2%, and it may be high when the diglyceride
ester content is higher than 6%, The correlation coefficient
between diglyceride content and glycidyl ester concentra-
tion was about 50% indicating that high diglyceride content
makes oils more susceptible to glycidyl ester formation, but
does not guarantee that an oil will contain glycidyl esters.
Glycidyl esters were frequently found in a wide variety
of refined vegetable oils. There was a correlation between
the diglyceride ester content of the oil and the concentration
123

J Am Oil Chem Soc (2011) 88:1–14
11
MCPD measured by the DGF method was always 1–2 mg/kg
higher than would be predicted by the LC–TOFMS analysis.
The same samples were subjected to a proprietary treatment
process that removed all MCPD esters and glycidyl fatty acid
esters when measured by LC–TOFMS. Those samples still
always showed positive results by the DGF method.
Table 7 Limit of detection for analytes in RBD palm oil
Compound
Estimateda detection
limit (mg/kg)
Lauric acid glycidyl ester
0.10
0.29
0.10
0.07
0.10
0.11
0.09
1.69
0.18
0.21
1.20
0.16
0.40
0.46
0.19
0.29
0.29
Myristic acid glycidyl ester
Palmitic acid glycidyl ester
Stearic acid glycidyl ester
Several experiments were conducted to determine con-
ditions that might prevent or remove MCPD esters and
glycidyl esters. Table 10 shows the results of an attempt to
eliminate glycidyl esters by acid treatments under rela-
tively mild conditions. A refined bleached deodorized corn
oil sample that was free from glycidyl esters and MCPD
esters as measured by the LC–TOFMS method prior to the
experiment was spiked with about 20 mg/kg glycidyl
stearate and was subjected to acid washing with 2 min of
high shear mixing followed by 60 min of gentle mixing at
70 °C. The samples were washed with water until the wash
had a neutral pH and were then assayed for glycidyl esters
and MCPD esters. The samples were not deodorized after
the treatment. Glycidyl esters were not destroyed by the
acid treatments. Treatment with hydrochloric acid resulted
in the formation of MCPD diesters without significant loss
of glycidyl esters. MCPD monoesters were not found.
ADM has developed a proprietary process to remove
MCPD esters and glycidyl esters from vegetable oils. The
last row of Table 10 shows the effect of this treatment on
the HCL washed samples. Amounts of glycidyl esters and
MCPD esters decreased to below the limit of detection of
the LC–TOFMS assay by the procedure.
Oleic acid glycidyl ester
Linoleic acid glycidyl ester
Linolenic acid glycidyl ester
Lauric acid MCPD monoester
Myristic acid MCPD monoester
Palmitic acid MCPD monoester
Stearic acid MCPD monoester
Oleic acid MCPD monoester
Linoleic acid MCPD monoester
Linolenic acid MCPD monoester
Palmitic acid–oleic acid–MCPD diester
Di-palmitic acid MCPD diester
Di-oleic acid MCPD diester
Palmitic acid–linoleic acid MCPD diester 0.19
Oleic acid–linoleic acid MCPD diester
Palmitic acid–stearic acid MCPD diester
Oleic acid–stearic acid MCPD diester
Di-linoleic acid MCPD diester
0.39
0.19
0.19
1.40
Linoleic acid–stearic acid MCPD diester
Co-elutes with
di-oleic MCPD diester
Di-stearic acid MCPD diester
0.19
0.1
Di-linolenic acid MCPD diester
Oleic acid–linolenic acid MCPD diester
Table 11 shows the effects of treating with various ab-
sorbents prior to deodorization on the MCPD ester and
glycidyl ester content of palm oil. Refined bleached palm
oil was treated with adsorbents as indicated and samples
were deodorized at 260 °C for 30 min with 3 Torr vacuum
and 3% steam sparge, conditions which are typical for
commercial refining of palm oil. The refined bleached palm
oil used in the experiment was free of detectable MCPD
esters and glycidyl esters prior to the experiment. The
results show that none of the adsorbents used prior to
deodorization were effective in reducing glycidyl ester
formation. Acidic alumina and acid washed carbon that had
been processed with hydrochloric acid resulted in the for-
mation of large amounts of MCPD esters in the samples
without reduction in the content of glycidyl esters.
Co-elutes with di-linoleic
MCPD diester
Linoleic acid–linolenic acid MCPD diester 0.39
Palmitic acid–linolenic acid MCPD diester 0.19
Stearic acid–linolenic acid MCPD diester Co-elutes with oleic-linoleic
MCPD Diester
a
Samples of vegetable oil that were below the limit of detection for all
analytes were spiked with increasing amounts of standards until a peak
above the limit of detection could be seen
This correlation suggests that diglycerides may be the pre-
cursors of glycidyl esters in processed vegetable oils.
An example of a direct comparison of the DGF method
results with those from direct LC–TOFMS analysis of
MCPD esters and glycidyl esters is shown in Table 9.
Samples of RBD palm oil and a commercial blend of
several vegetable oils were analyzed by the LC–TOFMS
method and by the DGF method. These samples were also
analyzed for free glycidol using headspace GC–MS and for
Challenges with the LC–TOFMS Method
There are a number of challenges to getting consistent
results with this LC–MS method. The sodium in the mobile
phase has detrimental effects on the MS system. The
instrument becomes dirty quickly from the sodium in the
mobile phase and from the vegetable oil and requires a
quick cleaning every day prior to use. More extensive
´
free MCPD using the method of Zelinkova et al. [8] (LOD
free MCPD 0.5 mg/kg; LOD free glycidol 0.2 mg/kg). Free
MCPD and free glycidol were not detected in any samples.
In samples which contained glycidyl esters or MCPD
esters measured by the LC–TOFMS method, the amount of
123

12
J Am Oil Chem Soc (2011) 88:1–14
Table 8 MCPD and glycidyl esters in commercial vegetable oils
Sample ID
Total MCPD Monoesters
(mg/kg) (DL = 1)
Total MCPD Diesters
(mg/kg) (DL = 0.5)
MCPD Equiv.
(mg/kg)
Total Glycidyl Esters
(mg/kg) (DL = 0.2)
Glycidol Equiv.
(mg/kg)
Corn oil K
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
4.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.8
0.0
1.2
0.8
1.3
0.0
0.0
0.0
0.0
1.5
1.1
0.3
ND
ND
0.6
2.6
3.7
1.3
1.3
3.4
1.5
15.5
0.4
0.5
15.6
33.7
ND
ND
0.4
0.3
0.1
0.0
0.0
0.2
0.7
1.0
0.3
0.3
0.9
0.4
4.2
0.1
0.1
4.2
9.1
0.0
0.0
Corn oil C
Corn oil M
Canola oil W
Canola oil K
Soy oil C
Soy oil K
Sesame oil S
Sesame oil I
Walnut oil T
Palm shortening S
Palm shortening blend G
Palm shortening P
Palm canola blend M
Palm shortening R
Palm olein (Japan)
Rice bran oil (Japan)
Cocoa butter light
Cocoa butter dark
ND
5.8
3.7
6.2
ND
ND
ND
ND
ND not detected
be shutdown for inspection and cleaning. We run a check
standard containing every analyte shown in Table 3 before
the first sample of the day is analyzed and at least once
every 10 samples to ensure adequate performance.
Conclusions
The LC–TOFMS method using sodium in the mobile phase
looks very promising as an approach for direct analysis of
MCPD esters and glycidyl esters in vegetable oil. The
ability to use the high resolution of the TOFMS to elimi-
nate interferences improves the sensitivity of the analysis
to the range that is acceptable for this determination.
The chemical method currently proposed by the DGF
does not agree well with the results from the LC–TOFMS
analysis. We believe the harsh chemicals of the DGF
procedure produces MCPD from precursors other than
MCPD and glycidol. Those artifacts are produced in a
consistent enough manner to make the DGF procedure look
fairly reproducible. The evidence that the compounds of
interest are destroyed and reformed during the chemical
reactions and the fact that all glycerides go through an
activated intermediate in the transesterification process
makes the results of this method questionable. Reactions
capable of transesterifying oils should be avoided in anal-
ysis of MCPD and glycidyl esters.
Fig. 7 Correlation of diglyceride content of vegetable oils and
glycidyl ester content by LC–TOFMS
cleaning is required at least weekly after heavy use. Certain
parts in the ESI source corrode quickly and require fre-
quent replacement. In the instrument we used, the ESI
nebulizer needle is made of stainless steel. In normal use, a
nebulizer needle would probably last a year or more. Using
this method, they corroded very quickly and needed to be
replaced weekly with heavy use. Close attention to internal
standard areas and frequent checking of standards are
needed to be certain that loss of intensity has not occurred.
At the first sign of lowered intensity, the instrument must
123

J Am Oil Chem Soc (2011) 88:1–14
13
Table 9 Comparison of DGF method results with LC–TOFMS results
Sample ID
DGF method Total MCPD equivalents Total MCPD diesters by LC– Total Glycidyl Esters By LC–
predicted by LC–TOFMS TOFMS (mg/kg) (DL = 0.5) TOFMS (mg/kg) (DL = 0.2)
RBD palm oil
7.74
6.2
6.1
18.6
ND
RBD palm oil treated to remove GE 2.85
and MCPDE
\0.2
ND
Commercial oil blend
3.64
1.83
2.7
ND
ND
9.9
Commercial oil blend treated to
remove GE and MCPDE
\0.2
ND
esters have no effect on the glycidyl ester content of the
samples. Glycidyl esters are widely present in oils which
do not contain MCPD esters.
Table 10 Effect of acid washing under mild conditions on MCPD
esters and glycidyl esters
Sample: RBD corn oil with
*20 mg/kg added
glycidyl stearate
Glycidyl
esters
(mg/kg)
3-MCPD
diesters
(mg/kg)
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
Control—no acid wash
Acetic acid wash
24.4
23.1
20.1
ND
ND
ND
40.8
ND
Hydrochloric acid wash
HCL washed sample taken
through GE-MCPDE removal process
References
Conditions of acid treatment: 0.1 v/wt% acid, 2 min shear mix,
60 min stir mix, 70 °C, washed with water until neutral
´ˇ
1. Velısek J et al (1979) Formation of volatile chlorohydrins from
glycerol (triacetin, tributyrin) and hydrochloric acid. Lebensm-
Wiss U-Technol 12:234–236
´
2. Davıdek J et al (1980) Glycerol chlorohydrins and their esters
as products of the hydrolysis of tripalmitin, tristearin and tri-
Table 11 Effect of acidic adsorbents on MCPD ester and glycidyl
ester content in deodorized vegetable oils
olein with hydrochloric acid.
171:14–17
Z Lebensm Unters Forsch
Sample of RB palm oil free of MCPD esters
and glycidyl esters prior to the experiment
Glycidyl
esters
(mg/kg)
MCPD
diesters
(mg/kg)
´ˇ
3. Velısek J et al (1980) New chlorine-containing organic com-
pounds in protein hydrolysates. J Agric Food Chem 28:1142–
1144
Control (no treatment)
18.8
35.1
16.9
21.4
22.2
ND
4. Collier P et al (1991) Mechanism of formation of chloropropanols
present in protein hydrolysates. J Amer Oil Chem Soc 68(10):
785–790
5. Reese P (2005) Report no. FD 04/12, FSA Project no. C03017,
18, 19; the origin and formation of 3-mcpd in foods and food
ingredients
6. ILSI Europe Report Series: 3-MCPD esters in food products.
Summary report of a workshop held in February 2009 in Inter-
national Life Sciences Institute, Brussels, Belgium
7. Tesser R, Santacesaria E, Di Serio M, Di Nuzzi G, Fiandra V
(2007) Kinetics of glycerol chlorination with hydrochloric acid: a
new route to alpha, gamma-dichlorohydrin. Ind Eng Chem Res
46:6456–6465
10% Magnesol XL, 110 °C, 30 min
10% Silica gel, 110 °C, 30 min
10% acidic aluminaa, 110 °C, 30 min
10% acid washed carbona, 110 °C, 30 min
a
ND
ND
73.2
215.6
Manufacturers confirmed that the acid washing was done with HCL
MCPD esters can form from contact with hydrochloric
acid under mild conditions. MCPD esters can also form
after contact with hydrochloric acid washed absorbents
during normal vegetable oil processing.
´
´
´ˇ
ˇ
8. Zelinkova Z, Svejkovska B, Velısek J, Dolezal M (2006) Fatty
acid esters of 3-chloropropane-1,2-diol in edible oils. Food Addit
Contam 23(12):1290–1298
Results of experiments where either acid or acidic
absorbents were in contact with the oil reveal that MCPD
ester formation and glycidyl ester formation occur by dif-
ferent mechanisms. These results, plus the fact that only
MCPD diesters are seen in refined oils, confirm that glyc-
idyl esters are not likely to be precursors of MCPD esters in
vegetable oils. It appears that glycidyl esters and MCPD
esters arise by independent mechanisms. Glycidyl ester
formation is somewhat correlated to the diglyceride content
of the oils. Conditions which favor formation of MCPD
´
´
ˇ
´ˇ
9. Divinova V, Svejkovska B, Dolezal M, Velısek J (2004) Deter-
mination of free and bound 3-chloropropane-1,2-diol by gas
chromatography with mass spectrometric detection using deu-
terated 3-chloropropane-1, 2-diol as internal standard. Czech J
Food Sciences 22:182–189
10. Weißhaar R (2008) Determination of total 3-chloropropane-
1,2-diol (3-MCPD) in edible oils by cleavage of MCPD esters
with sodium methoxide. Eur J Lipid Sci Technol 110:183–
186
11. Deutsche Gesellschaft fu¨r Fettwissenschaft:DGF Standard
Method C III 18 (2009) Determination of ester-bound 3-chloro-
propane-1, 2-diol (3-MCPD esters) and 3-MCPD forming
123

14
J Am Oil Chem Soc (2011) 88:1–14
substances in fats and oils by means of GC–MS. Deutsche Ein-
heitsmethoden zur Untersuchung von Fetten, Fettprodukten,
Tensiden und verwandten Stoffen. Wissenschaftliche Ver-
lagsgesellschaft, Stuttgart (Germany)
12. Callender HL, Forrester JS, Ivanova P, Preininger A, Milne S,
Brown HA (2007) Quantification of diacylglycerol species from
cellular extracts by electrospray ionization mass spectrometry
using a linear regression algorithm. Anal Chem 79:263–272
123