11
Rtx
®
-BAC1:
30m, 0.32mm ID, 1.8µm (cat.# 18003)
Rtx
®
-BAC2:
30m, 0.32mm ID, 1.2µm (cat.# 18002)
Dual-column analysis using a two-hole ferrule. 1.0mL headspace sample of a blood alcohol mix
.
Oven temp.:
40°C isothermal
; Inj. temp.:
200°C
; Carrier gas:
He
; Sample equilibration temp.:
70°C
; Sample equilibration time:
15min.
;
Vial pressure:
30psi
;Vial pressurization time:
0.15min.
;Vial sampling time:
0.01min.
; Transfer line:
0.32mm ID FSHydroguard
™
tubing
;
Transfer line temp.:
200°C
; Injectionport sleeve:
2mm ID
; Split flow:
20mL/min.
Conc.
w/v
1. methanol
0.1%
2. acetaldehyde 0.2%
3. ethanol
0.2%
4. isopropanol
0.1%
5. acetone
0.01%
6.
n
-propanol
0.1%
Quantitation Technique for Blood
Alcohol Analysis (Internal Standard)
The internal standard technique uses one or
more designated compounds at known
concentrations spiked into the sample. The
response of the compounds of interest are
then compared to the results of the internal
standard. There are several advantages to
this technique. Multiple injections of the
standard are not necessary for concentra-
tion calculations; small changes in injection
volumes or detector response over time can
be determined.
Headspace Applications
Figure 12
Achieve baseline resolution of all blood alcohol components in less than 3minutes using the
Rtx
®
-BAC1 andRtx
®
-BAC2 columns and aPerkin-ElmerHS 40 headspace autosampler.
6
5
4
3
2
1
min. 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
min. 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
6
5
4
3
2
1
A balanced pressure sampling unit was used to transport the sample to theGC. This
type of samplingworks better with columns that require higher head pressure
(smaller ID) to improve flow efficiencies. 0.32mm ID analytical columnswere
chosen for this application because of their higher operating pressure. Optimal
column performance during headspace analysis depends onGC/headspace system
set up. Band broadening can occur if there is excess dead volume in the sample flow
path between the sample valve and the head of the column. Low volume inlet liners
or interfaces in the injection port should be used to reduce the amount of excess
volume at the exit end of the transfer line.A 2mm ID linerwas used in this analysis
to reduce dead volume andmaintain narrow peakwidths. High carrier gas flow rates
through the transfer line also can be used tomaintain narrow sample bandwidths and
speed up sample transfer to the column head.A flow of 40mL-per-minutewas used
to optimize the analysis on the Perkin-Elmer HS 40 system.
Simulated blood alcohol sampleswere prepared and analyzed using amodification
of a procedure published byChristmore et al.
2
n
-Propanol was used as the internal
standard andwas prepared at a concentration of 0.03g/dL in 1.0M ammonium
sulfate as a diluent. Fivemilliliters of diluent were added to 1mL of sample in a
20mL headspace vial (
Figure 12
).
BloodAlcoholAnalysis
Analysis time and resolution are two critical factorswhen developing aGC assay for
ethanol.Analysis time for each sample should be as short as possiblewhile still
maintaining baseline resolution for all analytes. Isothermal analysis is themethod of
choice because it eliminates the cool-down period between temperature-programmed
runs. Overall analysis time can be reduced in isothermal analysis by raising the oven
temperature or by increasing carrier gas flow rate. However, in attempting to shorten
the analysis time, either by increasing the flow rate or raising the temperature, many
traditional capillary column stationary phases fail to provide adequate resolution of
all the components commonly tested during blood alcohol analysis. Current advances
have aided in the design of two novel capillary column stationary phases tomeet all of
these requirements—the Rtx
®
-BAC1 and the Rtx
®
-BAC2 columns.
