App note-Blood Alcohol Content Analysis using Nitrogen Carrier Gas
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Updated date
11 January 19
Title
App note-Blood Alcohol Content Analysis using Nitrogen Carrier Gas
Keywords
Blood Alcohol Content Analysis using Nitrogen Carrier Gas, article
Product Range
Other
Language
UK English
Company Brand
Peak Scientific
Blood Alcohol Content Analysis using Nitrogen Carrier Gas
Extracted text
Your local gas generation partner
Blood Alcohol Content
Analysis using Nitrogen
Carrier Gas
www.peakscientific.com
Blood Alcohol
Content Analysis
Using Nitrogen
Carrier Gas
vial and capped. The internal solution
consisted of 0.03% (v/v) n-propanol/ 1M
ammonium sulfate/ 0.1 M sodium hydrosulfite.
NIST traceable aqueous ethanol solutions
from Cerilliant and Lipomed were used as
calibrators (10, 50, 80, 200, 300, 500 mg/dL)
and controls (20, 80, 400 mg/dL) respectively.
Ed Connor Dr. Sc., Peak Scientific
Experimental
Greg Dooley Ph.D, Colorado State University
Analyses were conducted using an Agilent
7890B GC with split/splitless inlet and dual
columns each connected to an FID detector.
Splitting of the samples onto the columns
was via an Agilent unpurged Capillary Flow
Technology splitter. The GC was coupled with
an Agilent 7697A headspace sampler. Vial
pressurization gas for all tests was provided
by a Peak Scientific Precision Nitrogen
Generator. Carrier gas was provided by either
helium cylinder or the Precision Nitrogen
Standard Generator. The HS-GC-FID system
operating condtitions are displayed in Table 1.
Alcohol
consumption can seriously affect the
ability of a driver to operate a vehicle and blood
alcohol content (BAC) directly correlates with
this impairment. A number of nations have
zero alcohol tolerance for motorists, but the
majority of countries worldwide have a limit
of between 50 and 80 mg alcohol per 100
ml blood, or 0.05-0.08%. Results are used
in court to provide quantitive levels of BAC,
which makes it one of the most commonly
practised analyses in forensic laboratories.
The large number of samples and requirement
for speed of sample processing mean that
analysis needs to be conducted quickly,
whilst giving reliable and accurate results.
For analysis of BAC, headspace GC with FID
detection is typically used. Headspace GC
allows the quantitative analysis of alcohol
directly from blood samples. Standard
headspace systems use nitrogen for vial
presurization, with helium typically used for
GC carrier gas. This application note looks at
the use of nitrogen for both vial pressurisation
and GC carrier gas. Nitrogen offers a costeffective, abundant alternative to helium for
carrier gas, whilst giving similar performance.
Here we compare analysis of real forensic blood
samples, taken from motorists suspected
of driving under the influence of alcohol,
analysed using nitrogen and helium carrier gas.
Sample Preparation
Using a Hamilton Microlab 600 Diluter, 200
µL of calibrators, controls, or blood samples
were aliquoted and dispensed with 2000 µL of
internal standard solution into a 10ml headspace
Headspace sampler
Vial pressurization gas
Oven Temperature
Loop Temperature
Transfer line
Transfer line temperature
Gas Chromatograph
Carrier gas
Detector
Columns
Split ratio
Agilent 7697A
Nitrogen
70
70
Deactivated fused silica, 0.53 mm id
90
Agilent 7890B
Helium
Nitrogen
FID
DB-ALC1 (30m x 320 um x 1.8 um), DBALC2 (30m x 320 um x 1.8 um)
10:1
GC Oven Start temperature
GC Oven program rate
GC oven final temperature
Method runtime
40°C (3 mins)
40°C min-1
120°C (1.2)
6.2 minutes
Table 1. HS-GC-FID Operating Conditions
The
software
was
Agilent
Acquisition
and
Enhanced
Data
used
for
analysis
MassHunter
GC/MS
MSD
ChemStation
Analysis
E.02.02.1431.
Results
Calibration curves produced with helium and
nitrogen carrier gas both gave very good linearity
with both curves having R2 values of 99.9999.
Results of analyses of real blood samples
(analysed in duplicate) run with both nitrogen
and helium carrier gas gave equivalent
results with no differences found in the
calculated ethanol concentrations (Table 2).
Sample 1A
Sample 1B
Sample 2A
Sample 2B
Sample 3A
Sample 3B
Sample 4A
Sample 4B
Sample 5A
Sample 5B
Amount of ethanol detected (%)
Nitrogen
Helium
0.05749
0.05702
0.05776
0.05689
0.01438
0.01421
0.01433
0.01417
0.23587
0.23476
0.23481
0.23323
0.02295
0.02254
0.02285
0.02255
0.05890
0.05866
0.05948
0.05867
Table 2: Blood alcohol analysis results from analysis conducted with
nitrogen and helium carrier gas.
Figure 1: Calibration curves for ethanol standards run using nitrogen
and helium carrier gas.
Blood
alcohol
levels
of
5
blood
samples
were
analysed.
Figures 2 and 3 show chromatograms
from the DB-ALC1 and DB-ALC2 columns,
respectively for the separation and elution
order of analytes for the multi-component
resolution mix when run using nitrogen and
helium carrier gas. Separation of potentially
interfering components, such as methanol and
2-propanol was achieved within 3 minutes when
using either carrier gas (Figure 2 & Figure 3).
Figure2: Results of resolution mixture run on DB-ALC1 column using
nitrogen and helium carrier gas.
Of the five blood samples tested, one was
over 0.2%, which would result in a driving
ban in almost every country worldwide. Two
samples were over 0.05% which would result
in a driving ban in a number of countries.
The other two samples were 0.014% and
0.023% which would be below the limit
in the majority of countries worldwide.
Conclusions
Results of BAC analysis show that there is no
difference in the linearity of the calibration
curve, or of the calculated ethanol content
of real blood samples regardless of whether
nitrogen or helium carrier gas was used.
As an abundant, inexpensive alternative to
helium, which is becoming increasingly more
costly, there is no reason why nitrogen cannot be
used for BAC analysis in place of helium. Since
nitrogen is often used for vial pressurisation
in headspace samplers, the use of a single
gas source for vial pressurisation, carrier gas
and FID make-up gas simplifies the lab’s gas
sourcing and would allow total gas supply from
gas generators if the precision nitrogen was
used in conjunction with the Precision hydrogen
and zero air generators for GC-FID analysis.
Ed
Connor Dr.Sc. is a GC Product Specialist, Peak
Scientific,
Inchinnan
Business
Park,
Scotland,
UK
. Prior to joining Peak in February of this year, Ed
completed his Dr.Sc. at ETH Zurich in Switzerland.
Figure 3: Results of resolution mixture run on DB-ALC2 column using
nitrogen and helium carrier gas.
Greg Dooley Ph.D is the Director of the Analytical Toxicology
Laboratory at Colorado State University. His research involves
the development of analytical methods utilizing state of
the art instrumentation to measure analytes of interest
for current forensic and analytical toxicology applications.