Quantification of morphine, morphine 6-glucuronide, buprenorphine, and the enantiomers of methadone by enantioselective mass spectrometric chromatography in whole blood

Abstract

Deaths among drug addicts are frequently caused by intoxication with methadone and/or morphine. These drugs are often used in combination with other drugs, such as buprenorphine. In addition, methadone is generally used as a mixture of R- and S-enantiomers. To date, a method for separation and quantitation of these specific drugs has not been developed. The aim of this study was to develop a sensitive enantioselective method for quantitation of morphine, its active metabolite morphine 6-glucuronide, buprenorphine, and R- and S-methadone, in a single analytical run.
Whole blood samples were diluted with 0.5 mol/L ammonium carbonate buffer and extracted on a Bond Elut C18 solid-phase extraction column with an automatic solid-phase extraction system. Chromatographic separation was performed on a chiral alpha-1-acid glycoprotein column with an acetonitrile/ammonium acetate buffer (10 mmol/L, pH 7.0, 22:78 v/v) mobile phase. The whole blood concentrations of the drugs were quantified by mass spectrometry using their stable isotope-labeled compounds as internal standards.
The method was validated with respect to specificity, linearity, precision, limits of detection, and quantification and matrix effects. The precision (coefficient of variation) was below 15 %, and the accuracy was between 90 and 115 %.
This method will be useful for routine analyses in forensic laboratories where blood samples are frequently analyzed for drugs of abuse. In some cases, sudden death from methadone overdose is caused by the enantiomeric form of the methadone, which makes the enantiomer separation capability of this method important.

Full text

ORIGINAL ARTICLE
Quantification of morphine, morphine 6-glucuronide,
buprenorphine, and the enantiomers of methadone
by enantioselective mass spectrometric chromatography
in whole blood
Dorte J. Christoffersen
1
•Charlotte Brasch-Andersen
2
•Jørgen L. Thomsen
5
•
Martin Worm-Leonhard
1
•Per Damkier
3,4
•Kim Brøsen
4
Accepted: 11 March 2015
ÓSpringer Science+Business Media New York 2015
Abstract
Purpose Deaths among drug addicts are frequently
caused by intoxication with methadone and/or morphine.
These drugs are often used in combination with other
drugs, such as buprenorphine. In addition, methadone is
generally used as a mixture of R- and S-enantiomers. To
date, a method for separation and quantitation of these
specific drugs has not been developed. The aim of this
study was to develop a sensitive enantioselective method
for quantitation of morphine, its active metabolite mor-
phine 6-glucuronide, buprenorphine, and R- and S-metha-
done, in a single analytical run.
Methods Whole blood samples were diluted with
0.5 mol/L ammonium carbonate buffer and extracted on a
Bond Elut C18 solid-phase extraction column with an au-
tomatic solid-phase extraction system. Chromatographic
separation was performed on a chiral alpha-1-acid glyco-
protein column with an acetonitrile/ammonium acetate
buffer (10 mmol/L, pH 7.0, 22:78 v/v) mobile phase. The
whole blood concentrations of the drugs were quantified by
mass spectrometry using their stable isotope-labeled com-
pounds as internal standards.
Results The method was validated with respect to speci-
ficity, linearity, precision, limits of detection, and quan-
tification and matrix effects. The precision (coefficient of
variation) was below 15 %, and the accuracy was between
90 and 115 %.
Conclusions This method will be useful for routine ana-
lyses in forensic laboratories where blood samples are
frequently analyzed for drugs of abuse. In some cases,
sudden death from methadone overdose is caused by the
enantiomeric form of the methadone, which makes the
enantiomer separation capability of this method important.
Keywords Forensic analysis Enantiomeric separation 
MicrOTOF-Q Solid phase extraction Drugs of abuse
Introduction
Drug abuse and addiction are huge socioeconomic prob-
lems in many countries. The main cause of death among
drug addicts is intoxication with methadone and/or mor-
phine (Fig. 1), and these drugs are often used in combi-
nation with 3–4 other drugs, such as benzodiazepines or
alcohol [1].
Methadone, along with heroin/morphine, is one of the
most frequently detected drugs in Denmark, and is the
primary cause of death in post-mortem cases involving
drug addicts [6]. Methadone is a synthetic opiate used for
treating opioid dependency, and it is also used as an
analgesic in patients with severe or chronic pain. In Den-
mark, methadone is the most common drug of abuse among
patients in dependency treatment programs [1]. Methadone
&Dorte J. Christoffersen
dchristoffersen@health.sdu.dk
1
Department of Forensic Toxicology, Institute of Forensic
Medicine, Winsløwparken 17B, 5000 Odense C, Denmark
2
Department of Clinical Genetics, Odense University
Hospital, Sdr. Boulevard 29, 5000 Odense C, Denmark
3
Department of Clinical Biochemistry and Pharmacology,
Odense University Hospital, Sdr. Boulevard 29,
5000 Odense C, Denmark
4
Department of Clinical Pharmacology, University of
Southern Denmark, Winsløwparken 19, 5000 Odense C,
Denmark
5
Institute of Forensic Medicine, Winsløwparken 17B,
5000 Odense C, Denmark
123
Forensic Sci Med Pathol
DOI 10.1007/s12024-015-9673-9

is generally used as a racemic mixture of R- and S- enan-
tiomers, in which, the R-enantiomer is the primary active
component and is a more potent l-opioid receptor agonist
than S-methadone. The S-enantiomer of methadone in-
creases the QT interval, and this may be associated with
torsade de pointes tachycardia and sudden death [2].
Consequently, separation of the R- and S-enantiomers for
quantitation is of relevance.
Heroin (diacetylmorphine) is a prodrug of morphine. In
addition to its use as an illicit drug of abuse, heroin is
prescribed in dependency treatment programs in many
countries [3]. It is metabolized with a very short half-life of
between 2 and 5 min, but has a prolonged pharmacody-
namic effect of several hours. Heroin is rapidly hydrolyzed
to 6-acetyl-morphine, which is subsequently metabolized
to morphine by esterases present in the blood and liver [4].
Morphine is an opioid analgesic used for the treatment
of severe pain. It is the opioid of choice in palliative and
terminal care. Morphine is predominantly cleared from the
body by metabolism to inactive morphine-3-glucuronide
(M3G) and active morphine 6-glucuronide (M6G) [5]. The
metabolites of morphine can play important roles in the
interpretation of intoxication or death involving heroin or
morphine, mostly because M6G is pharmacologically ac-
tive. It has been suggested that these metabolites have a
slightly different, and even more pronounced, respiratory
depressant action than morphine. This occurs because the
metabolites bind to a different l-receptor subtype than
morphine, and have a more pronounced effect on the res-
piratory system. Despite the fact that the structures of
methadone and morphine differ, these drugs have clinically
comparable activity, and they are both used as drugs of
abuse by drug addicts in many countries and contribute to
socio-economic problems [6,7].
Buprenorphine is a semi-synthetic opioid, which is
25–50 times more potent than morphine and is used as an
alternative to methadone maintenance treatment for heroin
addiction [8].
A number of methods in the scientific literature describe
chromatographic separation of R- and S-methadone, and in
some cases, the relevant metabolites [4,6,9–14]. In ad-
dition, R- and S-methadone have been quantified in com-
bination with other drugs (e.g., buprenorphine,
norbuprenorphine, and cocaine) [4,8]. Further studies de-
scribe achiral analyses of morphine and its metabolites [5,
7,15–18]. Some other studies have developed methods for
Fig. 1 Structures of heroin, morphine, and methadone
Forensic Sci Med Pathol
123

different combinations of drugs of abuse, such as Rand
S-methadone with other drugs, or morphine and the
metabolites of morphine. However, to date, no methods
have been developed that specifically address the separa-
tion of methadone, morphine, and buprenorphine, the R-
and S-enantiomers of methadone, and the M6G metabolite
of morphine.
The aim of this study was to develop a method for
quantitation of R- and S-methadone, morphine, M6G, and
buprenorphine in whole blood samples collected from live
subjects and post-mortem. The focus was development of a
single extraction method for all the compounds of interest,
and a chromatographic system for separation and detection
of all the targets with acceptable recoveries and accuracies.
We report a liquid chromatography-mass spectrometry
method with automatic solid-phase extraction (SPE) that
accomplishes these goals.
Materials and methods
Study design
Standards for the method development were purchased and
prepared as described in the ‘‘Materials and standards’’ sec-
tion below. Post-mortem whole blood samples were obtained
from medicolegal autopsies at the Institute of Forensic Med-
icine, University of Southern Denmark (Odense, Denmark).
Whole blood samples were collected from live subjects who
were drug addicts and in maintenance therapy treatment at the
local drug treatment center in Odense. Blood samples for
quality control, calibration, and validation were collected
anonymously from live subjects. Samples were stabilized
with 100 mg of sodium fluoride in a 10 mL Vacutainer. The
blood was tested to ensure it was free of illicit and prescription
drugs before inclusion in the validation analyses. All post-
mortem samples were drawn from the femoral vein. The
samples were stored at -20 °C until required for analysis. The
post-mortem samples were collected in 10 mL containers
(without vacuum) containing sodium fluoride (1 % mass
fraction aqueous solution). The whole blood samples from
live drug addicts and post-mortem blood samples from de-
ceased drug addicts were used in method development to test
the applicability of the method for forensic use.
Materials and standards
R/S-Methadone hydrochloride (purity [98 %) was pur-
chased from Sigma-Aldrich (St. Louis, MO). Morphine
hydrochloride (purity 98.0–101.0 %) was purchased from
Unikem (Copenhagen, Denmark). M6G (purity [98.5 %)
was purchased from Lipomed AG (Arlesheim, Switzer-
land). Buprenorphine hydrochloride (purity 98.9 %) was
purchased from Meda Pharmaceuticals (Somerset, NJ).
Stable isotope-labeled standards of all the targets [R/S-
methadone-D
9
(purity 99.2 %), morphine-D
6
(purity
98.6 %), morphine-6ß-D-glucuronide-D
3
(purity 99.5 %),
and buprenorphine-D
4
(purity 98.8 %) were purchased
from Cerilliant Analytical Reference Standards (Round
Rock, Texas). All standards were used as received.
Stock solutions of R/S-methadone (50:50, v/v), mor-
phine, and buprenorphine were prepared in ethanol at 1.5,
3, and 5 mg/L of each enantiomer. A stock solution of
M6G was prepared in methanol:water (1:1, v/v; 5 mg/L).
Stock solutions of R/S-methadone-D
9
, morphine-D
6
, and
buprenorphine-D
4
were prepared in ethanol (5 mg/L). A
stock solution of morphine-6ß-D-glucuronide-D
3
was pre-
pared in methanol:water (1:1, v/v). Stock solution dilutions
were made with ethanol, except for M6G and its isotope-
labeled form, which were diluted with methanol:water (1:1,
v/v). Samples for external calibration of the MicrOTOF-Q
were prepared by adding diluted stock solutions to whole
blood.
The mobile phase constituents and buffers for extraction
were obtained as follows: ammonium bicarbonate (Sigma-
Aldrich); acetonitrile (VWR International, Radnor, PA),
methanol (pro analysis grade; Merck, Darmstadt, Ger-
many); 2-propanol (SupraSolv grade; Merck); aqueous
ammonia (25 % volume fraction; Merck); ethanol (puri-
ty [99.9 %.); sodium hydroxide; and acetic acid (glacial,
purity 100 %, pro analysis grade; Merck).
Instrumentation
The high-performance liquid chromatography system
consisted of a Series 1200 LC liquid chromatograph from
Agilent Technologies (Santa Clara, CA) equipped with a
vacuum degasser, a quaternary pump, an auto sampler, and
a thermostated column compartment. The mass selective
detector was a MicrOTOF-Q system from Bruker (Bil-
lerica, MA). The automatic extraction system was a Gilson
Aspec 271 SPE system (Gilson, Middleton, WI). The SPE
cartridge was an Agilent Bond Elut C18 column containing
200 mg of sorbent and with a volume of 3 mL. Chro-
matographic separation was performed with a chiral alpha-
1-acid glycoprotein analytical column (100 mm 94.0 mm
i.d., 5 lm) and an alpha-1-acid glycoprotein guard column
(10 mm 92.0 mm i.d., 5 lm) in series (both from
Advanced Separation Technologies, Whippany, NJ). The
mobile phase was acetonitrile/ammonium acetate buffer
(10 mmol/L, pH 7.0, 22:78 v/v). The flow rate was 0.6 mL/
min, the column temperature was 25 °C, and the injection
volume was 20 lL.
High-resolution mass spectrometry measurements were
performed with a Bruker Daltonics MicrOTOF-Q (Bruker).
This mass spectrometer is an orthogonal-accelerated
Forensic Sci Med Pathol
123

time-of-flight mass spectrometer equipped with an elec-
trospray ionization ion source. The acquisition parameters
for the system were as follows: ESI capillary voltage,
4500 V; nebulizing gas pressure, 15 MPa; drying gas flow
rate, 8L/min; and drying gas temperature, 200 °C. The
mass spectrometer was operated in positive ion mode from
50 to 1000 m/z.
Identification of the compounds of interest was based on
their masses within 0.02 Da, retention times within
±0.5 min, quality control samples within acceptance cri-
teria, internal calibration with whole blood, and internal
calibration with stable isotope-labeled compounds. The
masses and retention times of the targets are given in
Fig. 2. Data acquisition and data handling were carried out
with the MicrOTOF-Q software (Quant Analysis version
4.0 SP1 (Build 253), Bruker). The MicrOTOF-Q was tuned
before each run with a sodium formate cluster ions for
external calibration.
Calibration and sample preparation
A six-point calibration was conducted in duplicate using
whole blood samples spiked with isotope-labeled internal
standards of the target compounds. The calibration was re-
peated every month, or more frequently if the quality control
samples did not fulfill the requirements in relation to accu-
racy. The calibration curve was continuously evaluated by a
system check with solvent standards and quality control
samples in whole blood at two different concentration
levels. The solvent standard was used to perform a system
check to make sure that the chromatographic system was
operating under optimal conditions. Analyses of solvent
standards were performed at the beginning of an analysis
sequence and at the end of each run. The quality control
samples were analyzed at the beginning of every sequence
and in between samples to make sure the analyses were
within the requirements. The analysis sequence was ended
by another system check, which was compared with the first
check in the same run. The quality control samples had to
fulfill the acceptance criteria for the validation in relation to
accuracy. The calibration curve correlation and intercept
were also compared from calibration to calibration to make
sure that the calibration curve did not change over time.
The quality control samples contained a mixture of the
target compounds (R/S-methadone, morphine, M6G, and
buprenorphine) spiked at low (QC-LOW) and high con-
centration levels (QC-HIGH). These samples were ana-
lyzed before and after each run. The concentrations of the
compounds in the quality control samples are given in
Table 2. The results of the analysis or calibration were
accepted according to the validation criteria. Interference
from the blood matrix was determined from analysis of
blank samples obtained anonymously from healthy volun-
teers (whole blood).
The extraction of whole blood was performed according
to the following procedure. Solutions containing the
R-methadone S-methadone
R-methadone-D9S-methadone-D9
Buprenorphine
Buprenorphine-D4
Morphine
Morphine-D6
M6G
M6G-D3
Accurate mass 310.2170 Da
Accurate mass 319.2730 Da
Accurate mass 468.3108 Da
Accurate mass 472.3359 Da
Accurate mass 286.1438 Da
Accurate mass 292.1814 Da
Accurate mass 462.1759 Da
Accurate mass 465.1947 Da
Fig. 2 Chromatogram of all compounds with retention times and accurate masses in blank whole blood spiked with the target analytes
Forensic Sci Med Pathol
123

isotope labeled internal standards of morphine-D
6
, M6G-
D
3
,R/S-methadone-D
9
and buprenorphine-D
4
(10 lLofa
mixture of each isotope-labeled internal standard at the
relevant concentration) and 0.6 g of whole blood were
diluted with 1 mL of 0.5 mol/L ammonium carbonate
buffer (pH 8) and vortex-mixed briefly. The samples were
equilibrated for 10 min and then centrifuged for 10 min at
a relative centrifugal force of 34179g. Aliquots (1 mL) of
each solution were extracted with an automatic SPE sys-
tem. Before extraction, the Bond Elut C18 column was
conditioned with 2 mL of methanol, 2 mL of water, and
1 mL of ammonium carbonate buffer (0.5 mol/L, pH 8).
For extraction, 1 mL of the solution was loaded onto the
column. After application of the sample, the SPE column
was washed with 5 mL of ammonium carbonate buffer
(0.005 mol/L, pH 8). After 3 min of automatic drying of
the SPE column with nitrogen, the elution was carried out
with aqueous ammonia water in methanol (5 % volume
fraction; 2 91 mL). The eluate was evaporated to dryness
under a stream of nitrogen at 50 °C, and the residue was
reconstituted in 100 lL of the mobile phase.
Evaluation of the analytical method
Validation of the method included determination of the
specificity, linear range, intra- and interday precision, ac-
curacy, and sensitivity [limit of detection (LOD) and limit
of quantification (LOQ)]. Furthermore, a matrix effect
(suppression) study was performed [19]. The method was
validated using an in-house procedure in combination with
the procedure described by Polettini et al. [19]. The re-
covery was evaluated for all compounds of interest.
The method selectivity was used to determine if any
signals interfered with the signals of the targets or the
isotope-labeled internal standards at the specific retention
times and the actual masses of interest. Linearity was
evaluated by adding known concentrations of the four
target compounds and the four isotope-labeled internal
standards to blank whole blood samples at six concentra-
tion levels. All samples were prepared in duplicate. Sample
analyses were repeated on 4 different days and in duplicate
on each day. Calibration curves were prepared by plotting
the ratio of the peak area of the drug to the isotope-labeled
internal standard against the drug concentration. Linear
regression through all points, including the origin, and
application of a weighting of 1/xto the concentration, gave
correlation coefficients better than 0.99 in all cases.
Inter-run precision and accuracy were determined using
QC-LOW and QC-HIGH samples. Two concentration
levels of each of the compounds were tested in duplicate
daily for 15 days. The LOD was determined using three
times the standard error (SE) of the intercept, the LOQ was
determined using ten times the SE of the intercept. The
standard error is equal to the standard deviation divided by
the square root of the sample size (SE =SDHN).
The matrix effect was examined using aliquots of blank
whole blood, which were extracted and injected according
to the method described in the ‘‘Calibration and sample
preparation’’ section. The MicrOTOF-Q was outfitted with
a T-junction to allow for direct infusion of a constant
concentration of the targets, as described by Holm et al.
[10], into the eluent from the column. The infusion was
performed using a syringe pump. This continuous post-
column infusion produced a constant signal in the detector,
unless compounds that eluted from the column suppressed
or enhanced ionization [5,10,14] and led to decreased or
increased detector response, respectively. The infusion rate
was 3 lL/min. The concentrations of the infusion solutions
of morphine, M6G, R/S-methadone, and buprenorphine
were 0.09, 0.69, 0.23, and 0.14 mg/L, respectively.
Results
The compounds of interest were separated chromato-
graphically from each other during the liquid chromatog-
raphy run (see Fig. 2for retention time). Selectivity was
assured by using accurate mass selection in the MicrOTOF-
Q system with a 0.02 Da mass window and a retention time
window.
Chromatograms from a positive whole blood sample
from a living drug addict are shown in Fig. 3as overlays
with internal standard chromatograms. This blood sample
had the following concentrations: R-methadone, 0.15 mg/
L, S-methadone, 0.18 mg/L, morphine \LOQ, M6G \
LOQ, and buprenorphine \LOQ. Table 1shows the re-
sults from four patient samples, including whole blood
samples from drug addicts who were living and deceased.
We assumed the elution order of the R/S-enantiomers
would be similar to that described by Rodrigues-Rosas
et al. [12] because the analysis parameters were almost
identical, and because of the nature of the enantiomers.
Pure reference compounds of the enantiomers were either
not commercially available or very expensive, and there-
fore, were not used in this study.
In the present study, the mobile phase consisted of an
acetate buffer mixed with an organic phase. An earlier
study examined the difference between the use of formate
buffers and acetate buffers in a similar system and found no
difference at the applied buffer concentration of 10 mmol/
L[17].
The absolute recovery of the extraction was studied for
all compounds of interest and found to be higher than 90 %
for all compounds, except for M6G, which had recoveries
around approximately 30 % (data not shown). The
extraction was performed with the use of stable
Forensic Sci Med Pathol
123

isotope-labeled internal standards, which compensated for
the differences in extraction efficiency. Methods using
Bond Elut C18 columns for extraction of morphine glu-
curonides have already been published elsewhere [15,16].
Interference was evaluated by analysis of drug-free
samples obtained anonymously from healthy volunteers.
The samples were spiked with isotope-labeled internal
standards. No peaks appeared at the same masses or re-
tentions times as the compounds of interest. Linearity was
examined using a six-point calibration curve prepared from
whole blood samples in duplicate. The linear range is
shown in Table 2for the different targets of interest. The
correlation coefficients were all 0.999 with acceptable
residuals (\15 %) using 1/xweighting.
Accuracy and precision of the method for morphine,
M6G, R-andS-methadone, and buprenorphine were
evaluated from duplicate analyses of the QC-LOW and QC-
HIGH samples, which were repeated daily for 15 days. The
calculated average accuracy was 90 % for morphine, 110 %
for M6G, 106 % for R-methadone, 105 % for S-methadone,
and 95 % for buprenorphine. The results are summarized in
Table 2. The intra- and interday precision of the method
were determined as relative standard deviations. The results
were below 15 % for all targets. The results for the
validation parameters were considered acceptable.
The LOD was 0.007 mg/L for R- and S-methadone,
0.002 mg/L for morphine, 0.008 mg/L for M6G, and
0.004 mg/L for buprenorphine (Table 2). The LOQ was
0.02 mg/L for R- and S-methadone, 0.005 mg/L for mor-
phine, 0.03 mg/L for M6G, and 0.01 mg/L for buprenor-
phine. The working calibration range using the lowest
calibration point was 0.02 mg/L for morphine, 0.04 mg/L
for M6G, 0.05 mg/L for R- and S-methadone, and 0.04 mg/
L for buprenorphine. Results below these concentrations
were not included in for quantitation, but are reported as
\LOQ. Samples above the highest calibration point were
diluted and reanalyzed. The LOQs obtained for the whole
blood samples were below the toxic concentrations of the
compounds of interest, and in most of the cases, were also
below the therapeutic concentrations. Therefore, this
method could be used for routine analyses in forensic
toxicology.
Matrix effects may reduce or even eliminate the signal
of the substance of interest. Consequently, we tested for ion
suppression or enhancement in extracted blanks in the
matrix. These were injected into the system while mor-
phine, M6G, R/S-methadone, and buprenorphine in solu-
tion were infused at a constant rate through a T-junction at
the inlet of the MicrOTOF-Q. The results were compared
with those obtained for injection of the mobile phase [5,10,
R-methadone-D
9
R-methadone S-methadone
S-methadone-D
9
Time (min)
Fig. 3 Results from a positive whole blood sample from a living drug
addict, which contained R-methadone at 152.8 lg/L, S-methadone at
184.6 lg/L, morphine at \LOQ, and M6G at \LOQ. The figure
shows an overlay of two chromatograms—the internal standard
chromatogram and the sample chromatogram
Table 1 Application of the method to whole blood samples from four cases
Samples Morphine (mg/L) M6G (mg/L) R-methadone (mg/L) S-methadone (mg/L) Buprenorphine (mg/L)
Case 1 Dead drug addict 1.27 0.52 0.64 0.31 \LOQ
Case 2 Dead drug addict \LOQ \LOQ 0.62 0.52 \LOQ
Case 3 Living drug addict \LOQ \LOQ 0.16 0.19 \LOQ
Case 4 Living drug addict 0.25 2.65 0.26 0.17 \LOQ
Blood samples were collected from deceased drug addicts and living drug addicts. The results are the average of duplicate analyses
Forensic Sci Med Pathol
123

14]. Matrix-associated suppression was noted at around
7.5 min. However, this was an acceptable distance from the
compounds of interest, which had retention times of ap-
proximately 1.9, 9.5, 13.0, 13.7, and 16.6 min (see Fig. 4).
A degree of ion suppression was observed around the
retention time of M6G (1.8 min), with a suppression of
approximately 50 %. This suppression was acceptable be-
cause of the stability of the measurement, and the use of
isotope-labeled internal standards, which produced very
stable calibration and quality control determinations. Pre-
vious studies also indicated that use of isotopes as internal
standards was effective in minimizing the influence of
matrix effects [11,19]. The degree of ion suppression is
shown in Fig. 4as an example for trace levels of morphine.
All other compounds of interest were determined without
any ion suppression or enhancement at their retention time.
The ion suppression was mostly observed at the beginning
of the analysis or chromatogram, which was in accordance
with this observation.
The results of the validation studies in Table 2demon-
strated that the method had acceptable accuracies and
precision.
Discussion
The developed highly sensitive enantioselective mass
spectrometric method could be used to quantify combina-
tions of morphine, M6G, R- and S-methadone, and
buprenorphine in a single run. Such a method is useful
because of its applicability in forensic toxicology, where
the combination of these compounds is highly relevant.
The applicability of the method was shown using whole
blood samples from living and deceased drug addicts.
Previous studies have detailed methods for different drug
combinations or the enantioselective separation alone, but
none of these methods have been for the specific combi-
nation of drugs detailed above, or for sensitive enantiomer
2 4 6 8 10 12 14 16 18 Time [min]
-0.5
0.0
0.5
1.0
1.5
2.0
4
x10
Intens.
Morphine
Blank whole blood
Non-injection
Retention time
Fig. 4 Example of matrix
effect detection in a blank whole
sample containing traces of
morphine
Table 2 Validation parameters with inter- and intra-day variation and calibration data for morphine, M6G, R-methadone, S-methadone, and
buprenorphine in whole blood
Target LOW *QC3 HIGH *QC5 Calibration LOQ
Mean RSD (%) Accuracy (%) Mean RSD (%) Accuracy (%) Concentration (mg/L) Concentration (mg/L)
Between day variation (inter day)
Morphine 0.05 4 90 0.5 3 90 0.02–1.0 0.005
M6G 0.08 0 110 0.6 2 110 0.04–0.8 0.03
R-methadone 0.125 2 106 0.5 1 106 0.05–2.1 0.02
S-methadone 0.125 1 105 0.5 0 105 0.05–2.1 0.02
Buprenorphine 0.08 3 94 0.6 3 94 0.04–0.8 0.01
With-in day variation (intra day)
Morphine 0.05 6 90 0.5 7 90 0.02–1.0 0.005
M6G 0.08 15 110 0.6 13 110 0.04–0.8 0.03
R-methadone 0.125 5 106 0.5 7 106 0.05–2.1 0.02
S-methadone 0.125 8 105 0.5 11 105 0.05–2.1 0.02
Buprenorphine 0.08 11 94 0.6 8 94 0.04–0.8 0.01
Forensic Sci Med Pathol
123

separation. The developed method can be used extract
morphine, M6G, R- and S-methadone, and buprenorphine
from whole blood samples from live subjects and from
post-mortem blood of varying viscosity (Fig. 3). The
method is successful even with clotted and decomposed
blood, which is often a challenge in forensic toxicology.
The assay was able to quantify morphine over a range of
0.02–1.0 mg/L in whole blood, M6G over a range of
0.04–0.8 mg/L, R- and S-methadone over a range of
0.05–2.1 mg/L per enantiomer, and buprenorphine over a
range of 0.04–0.8 mg/L in a single run with high accuracy
and stability. Linearity of the calibration curve in whole
blood was in accordance with the acceptance criteria with a
correlation coefficient better than 0.99 for all compounds,
and the achieved linearity was stable over time.
The specific determination of the enantiomeric form of
methadone is interesting and important because sudden
death of drug addicts can occur in methadone maintenance
programs or in illicit use of methadone, and might be ex-
plained by side effects caused by the S-enantiomer. In one
study, analysis of a cohort of patients treated with metha-
done showed that cytochrome P450 2B6 could slow the
metabolism of S-methadone and increase the risk of sudden
death from cardiac arrhythmias caused by stereoselective
blocking of the hERG gene, which codes for a subunit of
the potassium ion channels that are involved in regulation
of cardiac muscle [2]. Therefore, discrimination between
R- and S-methadone might be of importance in interpre-
tation of forensic toxicology reports. An earlier study [9]
showed that the R/Sratio varied considerably from subject
to subject, therefore, measurements of the total amount of
methadone in plasma do not necessarily reflect the amount
of active opioid present. In this study, R-methadone con-
centrations were significantly higher than S-methadone
concentrations [9]. In the present study, we also observed
concentration differences between R- and S-methadone in
the few samples analyzed.
The metabolites of morphine might play an important
role in the interpretation of intoxication or death involving
heroin or morphine, mostly because M6G is pharmaco-
logically active. It has been suggested that this metabolite
have a slightly different, and even more pronounced, res-
piratory depressant action than morphine because it binds
to a different l-receptor subtype and produces a more
pronounced effect on the respiratory system [7,15]. In
addition, the ratio between metabolite and parent drug
could be used to determine if the morphine use has been
acute or chronic.
In forensic toxicology, where analysis or quantification
is performed on material from both live individuals and the
deceased, there are numerous potential interfering sub-
stances because of the nature of the biological matrix (i.e.,
whole blood). These interferences can include endogenous
matrix components, metabolites, and products of decom-
position (putrefaction and degradation). After death the
composition of body fluids can change, and so does fluid
distribution. Death leads to cell lysis, and endogenous and
exogenous bacteria cause putrefaction. Quantitative ana-
lysis of blood is affected by variable degrees of sedimen-
tation, coagulation, hemolysis, putrefaction, and
contamination with tissue fluids, and therefore, the sam-
pling site is of huge importance when sampling and in-
terpreting the results. Validation of a method for precise
quantification in post-mortem cases is a difficult process,
because degradation of the sample might have already af-
fected the drug concentration, and the samples may vary
considerably from case to case because of differences in
putrefaction or partial decomposition. Therefore, in post-
mortem cases, the results are only approximate even if the
method performance is good with reference to precision
and accuracy [19]. Robust methods for forensic analysis
are highly desirable, and the use of exact mass in mass
spectrometry provides the opportunity to select for com-
pounds of interest instead of having a complex chro-
matograph with many interferences. Matrix effects were
observed in the present method to some degree, and mostly
occurred for compounds with relatively short retention
times (e.g., M6G). The use of isotope-labeled internal
standard in the method helped prevent instability problems
because of matrix effects, and the method was stable with
acceptable accuracies for all compounds.
Development of a method for determining the concen-
trations of morphine and methadone and their metabolites
is of considerable importance. There is often an overlap
between concentrations in fatal and nonfatal intoxications
with morphine and methadone, which arises from numer-
ous factors, including tolerance, the time between exposure
and death, use of supportive care, loss of tolerance from a
period of opioid abstinence, state of health of the deceased,
and post-mortem redistribution and changes in concentra-
tion after death. Methadone has a slightly higher degree of
post-mortem redistribution than morphine In addition,
post-mortem drug concentrations can vary depending on
the sampling site, and in general, central sites have higher
concentrations than peripheral sites. Therefore, samples are
traditionally taken of femoral blood in forensic cases, and
this was selected as the sampling site for the present study.
In forensic toxicology, the concentrations of morphine
or other drugs are usually determined in whole blood
samples, rather than in plasma or serum samples, which are
used in clinical studies. To support the assumption that
whole blood samples are suitable for this type of analysis,
one study has shown that the plasma/whole blood distri-
bution of morphine is close to 1.0 [20].
Forensic Sci Med Pathol
123

Key points
1. A method for the quantification of morphine, morphine
6-glucuronide, R- and S-methadone was developed.
2. This method complies, is validated, and is acceptable
and suitable for use for routine purposes.
3. This method is applicable for forensic analysis of drugs
of abuse in whole blood from both living and deceased
individuals.
4. Enantiomeric separation with this method will be
useful for determining the cause of sudden death in
medico-legal autopsies where there is no other toxico-
logical explanation.
Acknowledgments The authors thank laboratory technician Helle
Terp for excellent technical assistance. The study was financially
supported by The Region of Southern Denmark, Grant Number
09/13450.
References
1. Simonsen KW, Normann PT, Ceder G, Vuori E, Thordardottir S,
Thelander G, et al. Fatal poisoning in drug addicts in the Nordic
countries in 2007. Forensic Sci Int. 2011;207(1–3):170–6.
2. Eap CB, Crettol S, Rougier JS, Schlapfer J, Sintra GL, Deglon JJ,
et al. Stereoselective block of hERG channel by (S)-methadone
and QT interval prolongation in CYP2B6 slow metabolizers. Clin
Pharmacol Ther. 2007;81(5):719–28.
3. Strang J, Metrebian N, Lintzeris N, Potts L, Carnwath T, Mayet
S, et al. Supervised injectable heroin or injectable methadone
versus optimised oral methadone as treatment for chronic heroin
addicts in England after persistent failure in orthodox treatment
(RIOTT): a randomised trial. Lancet. 2010;375(9729):1885–95.
4. Rook EJ, Hillebrand MJX, Rosing H, van Ree JM, Beijnen JH.
The quantitative analysis of heroin, methadone and their
metabolites and the simultaneous detection of cocaine, acetyl-
codeine and their metabolites in human plasma by high-perfor-
mance liquid chromatography coupled with tandem mass
spectrometry. J Chromatogr B. 2005;824(1–2):213–21.
5. Taylor K, Elliott S. A validated hybrid quadrupole linear ion-trap
LC-MS method for the analysis of morphine and morphine
glucuronides applied to opiate deaths. Forensic Sci Int. 2009;
187(1–3):34–41.
6. Jantos R, Skopp G. Postmortem blood and tissue concentrations
of R- and S-enantiomers of methadone and its metabolite EDDP.
Forensic Sci Int. 2013;226(1–3):254–60.
7. Al-Asmari AI, Anderson RA. Method for quantification of opi-
oids and their metabolites in autopsy blood by liquid chro-
matography-tandem mass spectrometry. J Anal Toxicol. 2007;
31(7):394–408.
8. Rodriguez-Rosas ME, Lofwall MR, Strain EC, Siluk D, Wainer
IW. Simultaneous determination of buprenorphine, norbuprenor-
phine and the enantiomers of methadone and its metabolite
(EDDP) in human plasma by liquid chromatography/mass
spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci.
2007;850(1–2):538–43.
9. Buchard A, Linnet K, Johansen SS, Munkholm J, Fregerslev M,
Morling N. Postmortem blood concentrations of R- and S-enan-
tiomers of methadone and EDDP in drug users: influence of co-
medication and p-glycoprotein genotype. J Forensic Sci.
2010;55(2):457–63.
10. Holm KM, Linnet K. Chiral analysis of methadone and its main
metabolite, EDDP, in postmortem brain and blood by automated
SPE and liquid chromatography-mass spectrometry. J Anal
Toxicol. 2012;36(7):487–96.
11. Johansen SS, Linnet K. Chiral analysis of methadone and its main
metabolite EDDP in postmortem blood by liquid chromatogra-
phy-mass spectrometry. J Anal Toxicol. 2008;32(7):499–504.
12. Rodriguez-Rosas ME, Medrano JG, Epstein DH, Moolchan ET,
Preston KL, Wainer IW. Determination of total and free con-
centrations of the enantiomers of methadone and its metabolite
(2-ethylidene-1,5-dimethyl-3,3-diphenyl-pyrrolidine) in human
plasma by enantioselective liquid chromatography with mass
spectrometric detection. J Chromatogr A. 2005;1073(1–2):
237–48.
13. Wang SC, Ho IK, Wu SL, Liu SC, Kuo HW, Lin KM, et al.
Development of a method to measure methadone enantiomers
and its metabolites without enantiomer standard compounds for
the plasma of methadone maintenance patients. Biomed Chro-
matogr. 2010;24(7):782–8.
14. Moody DE, Lin SN, Chang Y, Lamm L, Greenwald MK, Ahmed
MS. An enantiomer-selective liquid chromatography-tandem
mass spectrometry method for methadone and EDDP validated
for use in human plasma, urine, and liver microsomes. J Anal
Toxicol. 2008;32(3):208–19.
15. Bogusz MJ, Maier RD, Erkens M, Driessen S. Determination of
morphine and its 3- and 6-glucuronides, codeine, codeine-glu-
curonide and 6-monoacetylmorphine in body fluids by liquid
chromatography atmospheric pressure chemical ionization mass
spectrometry. J Chromatogr B Biomed Sci Appl. 1997;
703(1–2):115–27.
16. Dienes-Nagy A, Rivier L, Giroud C, Augsburger M, Mangin P.
Method for quantification of morphine and its 3- and 6- glu-
curonides, codeine, codeine glucuronide and 6-monoacetylmor-
phine in human blood by liquid chromatography-electrospray
mass spectrometry for routine analysis in forensic toxicology.
J Chromatogr A. 1999;854(1–2):109–18.
17. Kolmonen M, Leinonen A, Kuuranne T, Pelander A, Ojanpera I.
Hydrophilic interaction liquid chromatography and accurate mass
measurement for quantification and confirmation of morphine,
codeine and their glucuronide conjugates in human urine.
J Chromatogr B Analyt Technol Biomed Life Sci. 2010;878(29):
2959–66.
18. Whittington D, Kharasch ED. Determination of morphine and
morphine glucuronides in human plasma by 96-well plate solid-
phase extraction and liquid chromatography-electrospray ioniza-
tion mass spectrometry. J Chromatogr B Analyt Technol Biomed
Life Sci. 2003;796(1):95–103.
19. Peters FT. Method validation using LC-MS. In: Polettini A,
editor. Applications of LC-MS in toxicology. London: Pharma-
ceutical Press; 2006. p. 43–64.
20. Hand CW, Moore RA, Sear JW. Comparison of whole blood and
plasma morphine. J Anal Toxicol. 1988;12(4):234–5.
Forensic Sci Med Pathol
123