SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
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P32 <br />
METHOD FOR CARBON MONOXIDE DETERMINATION IN BLOOD USING GAS <br />
CHROMATOGRAPHY WITH METHANE AS AN INTERNAL STANDARD <br />
H.Samkova*, J.Pivnicka, M.Spackova <br />
Institute <strong>of</strong> <strong>Forensic</strong> Medicine <strong>of</strong> St. Anne's University Hospital Brno, Czech Republic. <br />
A gas chromatographic procedure for determination <strong>of</strong> carboxy haemoglobin in blood with a thermal <br />
conductivity detector is commonly used. Processing <strong>of</strong> blood samples for the measurement <strong>of</strong> liberated <br />
carbon monoxide and obtaining reproducible results, especially in cases <strong>of</strong> postmortem blood samples, is <br />
performed using a method with methane as an internal standard. An apparatus for postmortem blood <br />
sample preparation for CO liberation and subsequent GC determination is presented together with a <br />
description <strong>of</strong>the method that includes schematic drawings. A core part <strong>of</strong>the device is a simple reaction <br />
tube partly filled with saturated NaCI solution. Blood, diluted 1: 1 with distilled water, is added into the <br />
tube. Then the tube is closed and deaerated through a rubber septum. Through the same septum, a <br />
ferricyanide reagent and a gas mixture <strong>of</strong> H2 and CH 4 (10:1) are added. The addition <strong>of</strong> reagents and gas <br />
phase is performed in a system <strong>of</strong> communicating vessels. Methane serves as an internal standard. The <br />
reaction mixture is shaken and an aliquot part <strong>of</strong> the gas phase is injected into the gas chromatograph <br />
(chromatographic column packed with molecular sieve 5A, isothermal conditions 80'C , TCD, carrier gas: <br />
hydrogen). A blood sample saturated with carbon monoxide up to 100% is processed in the same way. <br />
Total concentration <strong>of</strong> bonded CO in the sample is calculated from peak areas <strong>of</strong> analysed sample and 100 <br />
% saturated one. <br />
Aco<br />
ACH4<br />
%CO = ( **--*--.- )samPle X ( ---.---.- )100% X 100 %<br />
ACH4<br />
Aco<br />
The calibration curve was obtained on the basis <strong>of</strong> measurements <strong>of</strong> intermixture fully saturated blood<br />
sample and negative one in required ratios.<br />
The method was validated with following parameters:<br />
COHb calibration in the range <strong>of</strong> 0 - 100% <br />
Y= 0,0031x + 0,0045 <br />
R2=0,9973 <br />
LOD 0,44 % COHb <br />
LOQ = 1,47 % COHb <br />
The method is applicable even in cases <strong>of</strong> decomposed blood. Replicate injection <strong>of</strong> the homogenous gas<br />
phase into the gas chromatograph may be performed. The precision <strong>of</strong> the determination expressed as<br />
coefficient <strong>of</strong>variation deteriorates in cases <strong>of</strong>lower concentration <strong>of</strong>COHb.<br />
Keywords: blood sample preparation, carbon monoxide, internal standard<br />
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