Headspace gas chromatographic determination of ethanol: the use of factorial design to study effects of blood storage and headspace conditions on ethanol stability and acetaldehyde formation in whole blood and plasma

Our headspace gas chromatographic flame ionization detection (HS-GC-FID) method for ethanol determination showed slightly, but consistently, low ethanol concentrations in whole blood (blood) in proficiency testing programs (QC-samples). Ethanol and acetaldehyde were determined using HS-GC-FID with capillary columns, headspace equilibration temperature (HS-T degrees ) of 70 degrees C and 20 min equilibration time (HS-EqT). Full factorial designs were used to study the variables HS-T degrees (50 degrees -70 degrees C), HS-EqT (15-25 min), ethanol concentration (0.20-1.20 g/kg) and storage at room temperature (0-6 days) with three sample-sets; plasma, hemolyzed blood and non-hemolyzed blood. A decrease in the ethanol concentration in blood was seen as a nearly equivalent increase in the acetaldehyde concentration. This effect was not observed in plasma, indicating chemical oxidation of ethanol to acetaldehyde in the presence of red blood cells. The variables showed different magnitude of effects in hemolyzed and non-hemolyzed blood. A decrease in ethanol concentration was seen even after a few days of storage and also when changing the HS-T degrees from 50 to 70 degrees C. The formation of acetaldehyde was dependent on all the variables and combinations of these (interactions) and HS-T degrees was involved in all the significant interaction effects. Favorable instrumental conditions were found to be HS-T degrees of 50 degrees C and HS-EqT of 15-25 min. The ethanol concentrations obtained for the range 0.04-2.5 g/kg after analyzing authentic forensic blood samples with a HS-T degrees of 50 degrees C were statistically significantly higher than at 70 degrees C (+0.0154 g/kg, p < 0.0001, n = 180). In conclusion, chemical oxidation of ethanol to acetaldehyde in the presence of red blood cells has been shown to contribute to lowered ethanol concentrations in blood samples. Storage conditions before analysis and the headspace equilibration temperature during analysis were important for the determination of blood ethanol concentrations.     

腐败血液中自生醇现象及法医学应用研究

目的 检测分析腐败血液中乙醇、甲醇等物质的生成过程,为正确判断案发时人血液中醇类物质的实际浓度提供实验依据.方法 以正常健康人血液制作腐败样本,分别模拟人死亡后正常人血液和糖尿病人高糖血液的腐败过程,借助顶空气相色谱仪测定两种血液腐败后醇/醛类物质的生成情况并对比含量差异.结果 相同实验条件下,高糖血液较正常健康血液更...     

Medicolegal studies on alcohol detected in dead bodies — alcohol levels in skeletal muscle

An experiment was carried out on rats to determine whether or not a skeletal muscle sample was suitable for the determination of ethanol concentration in a carcass. Gas chromatography was used to estimate the ethanol and n-propanol concentrations in the femoral muscle and intracardial blood. The ethanol concentration of each sample was corrected according to the moisture ratio of circulating blood, viz., 78.5%.The ethanol concentration ratio of blood to muscle was 1.03 two hours after ethanol administration. When the carcasses of rats pre-treated with ethanol were stored at 15 °C and 25 °C, respectively, the ethanol concentrations in muscle and blood increased with time. At all times the concentration was higher in blood than in muscle, and also higher in samples collected from the carcass stored at 25 °C than at 15 °C.When the control carcass was stored in the same manner, the postmortem production of ethanol was noticed in both blood and muscle. As in the experimental rats, the control rats exhibited a higher blood ethanol than muscle ethanol level. Again, the ethanol concentration was higher in samples collected from the carcass stored at 25 °C than at 15 °C. The ratio of ethanol to n-propanol was less than 20:1 in blood and less than 10.1 in muscle.These results suggest that skeletal muscle may be a suitable tissue for the postmortem detection of ethanol.     

Testing Antemortem Blood for Ethanol Concentration from a Blood Kit in a Refrigerator Fire

The stability of ethanol in antemortem blood stored under various conditions has been widely studied. Antemortem blood samples stored at refrigerated temperature, at room temperature, and at elevated temperatures tend to decrease in ethanol concentration with storage. It appears that the stability of ethanol in blood exposed to temperatures greater than 38°C has not been evaluated. The case presented here involves comparison of breath test results with subsequent analysis of blood drawn at the time of breath testing. However, the blood tubes were in a refrigerator fire followed by refrigerated storage for 5 months prior to analysis by headspace gas chromatography. The subject’s breath was tested twice using an Intoxilyzer 8000. The subject’s blood was tested in duplicate using an Agilent headspace gas chromatograph. The measured breath ethanol concentration was 0.103 g/210 L and 0.092 g/210 L. The measured blood ethanol concentration was 0.0932 g/dL for both samples analyzed. Although the mean blood test result was slightly lower than the mean breath test result, the mean breath test result was within the estimated uncertainty of the mean blood test result. Even under the extreme conditions of the blood kit being in a refrigerator fire, the measured blood ethanol content agreed well with the paired breath ethanol test.     

乙醇对家兔脑基底动脉零应力状态影响关系的研究

目的探讨乙醇对家免脑基底动脉零应力状态的影响。方法通过酒精灌胃的方法建立家兔血液乙醇浓度梯度的动物模型,测定各组家兔局部脑微区的血流灌注量;并通过测量血管张开角的方法测定各组家兔脑基底动脉的零压力状态。结果家兔灌酒后局部脑微区血流量值明显增大,至30min后,各组家兔脑血流量基本恒定;血液乙醇浓度持续增高,灌胃后1.5~2h,血液乙醇浓度达到峰值。灌酒后局部脑微区血流量值和血液乙醇浓度与灌酒量存在正相关关系。各组家兔酒精灌2h后基底动脉张开角均明显降低,各组之间差异存在统计学意义(P<0.05),且随灌胃量的增大基底动脉张开角降低越大。结论家兔基底动脉零应力状态随血液酒精浓度的增加而降低。     

The rate and kinetic order of ethanol elimination

The rate and kinetic order of ethanol elimination was evaluated in human volunteers. Part I of the study involved dosing individuals with alcoholic beverages on two separate occasions. Breathalyzer tests were performed at 15-min intervals for a period of 5 h. Attention was focused on values obtained after peak blood ethanol levels had been reached. The second part of the study included having samples drawn from alcoholics at predetermined intervals during recovery from alcoholic intoxication. Blood ethanol concentration data was analyzed for kinetic order and a comparison of ethanol elimination rates of alcoholics and non-alcoholics was made. The predicative capability of estimating a BAC from both the zero and first order theories was also investigated.It was concluded that ethanol elimination is a zero order process. For subjects classified as non-drinkers (consume less than 6 ounces of ethanol/month), the mean ethanol elimination rate as determined in the study was 12 ± 4 mg/h. For subjects classified as social drinkers (consume more than 6 ounces but less than 30 ounces of ethanol/month), the mean ethanol elimination rate was 15 ± 4 mg%/h, and for alcoholics, the mean ethanol elimination rate was 30 ± 9 mg%/h. These results indicate that the rate of ethanol elimination increases with drinking experience.     

Ethanol stability in unpreserved refrigerated antemortem blood

Ethanol stability in preserved antemortem blood has been widely studied since it is a common practice in cases involving suspected impaired driving to collect antemortem blood in evacuated blood tubes containing sodium fluoride. In some situations, antemortem blood is submitted to a forensic laboratory for ethanol analysis in evacuated blood tubes that contain only an anticoagulant. There has been limited research on ethanol stability in antemortem blood stored without a preservative. On two occasions, antemortem blood was collected from five ethanol-free individuals into 6-ml Vacutainer® tubes containing only 10.8 mg potassium EDTA. The blood tubes were spiked with ethanol to approximately either 0.08 or 0.15 g/dl. Dual-FID headspace gas chromatography was used to analyze 58 blood tubes, 29 from each session, for ethanol 1 day after sample collection and again after 1 year of refrigerated storage (~4°C). Statistically significant decreases in ethanol were detected at the 0.05 level of significance. Mean decreases in ethanol after 1 year of storage for the 0.08 and 0.15 g/dl samples were 0.013 and 0.010 g/dl, respectively. The mean ethanol decrease across all tubes was 0.012 g/dl. The range of decreases for the 58 blood tubes was 0.003–0.018 g/dl. The mean ethanol decreases measured in this unpreserved antemortem blood are comparable in magnitude to those previously observed in antemortem blood containing sodium fluoride after 1 year of refrigerated storage. Ethanol did not increase in the antemortem blood samples despite the absence of sodium fluoride.     

Postmortem production of ethanol in different tissues under controlled experimental conditions

The aim of this study was to follow the postmortem ethanol production phenomenon under controlled experimental conditions (temperature, time interval) in different tissues. Specimens of blood, liver, skeletal muscle and kidney were taken from 30 corpses and no chemical preservatives were used in the specimens collected. Ethanol concentrations were detected by gas chromatography. All specimens stored at -20 degrees C and 4 degrees C did not show any change in ethanol concentration in an eight-day time interval. At 20 degrees C and 30 degrees C, all tissues, except blood, showed statistically significant ethanol production over the time interval tested. However, blood sample kept at 30 degrees C, showed statistically significant increase in ethanol production on the 2nd and 4th day comparing to the controls. Thus, we can state that postmortem ethanol production occurs in different tissues, and is increased at higher temperatures and, in general, it is in accordance with the course of time.     

Ethanol production by Candida albicans in postmortem human blood samples: effects of blood glucose level and dilution

We present two cases in which the ethanol concentration in blood samples taken after death continued to increase in the absence of any remarkable increase in n-propanol concentration. Species of bacteria and yeasts, including Candida albicans were isolated from these samples. We then examined whether C. albicans, the most common yeast in the general environment, was able to produce ethanol in human blood stored at room temperature. Ethanol production increased as the glucose concentration increased, indicating that C. albicans produced ethanol from the glucose. Our results also suggested that C. albicans produced ethanol more easily in blood diluted by intravenous infusions that included glucose than in undiluted blood. These findings are useful for the evaluation of postmortem ethanol production in subjects whose blood has been diluted by infusions with glucose. Furthermore, there was no quantitative relationship between the amount of n-propanol detected and the amount of ethanol production: n-propanol appears to be an unreliable index of putrefaction and postmortem ethanol production by C. albicans. It is possible for the blood ethanol level to be high and n-propanol not to be detected, even if the subject has not been drinking alcohol. We reconfirmed the necessity of immediately adding sodium fluoride to samples for ethanol analysis to prevent postmortem ethanol production.     

Blood, bone marrow and eye fluid ethanol concentrations in putrefied rabbits

The effect of putrefaction on postmortem blood, bone marrow and eye fluid ethanol levels was evaluated in rabbits. Control and dosed animals were sacrificed and stored at either room temperature (approx. 19 degrees C) or cold temperature (approx. 3.5 degrees C) for as long as 28 days. Control animals stored at room temperature showed ethanol levels in the bone marrow that peaked at 7 days after sacrifice, followed by decreases to a nondetectable level at 21 days. Overall decreases were demonstrated in bone marrow of dosed rabbits stored at room temperature for all postmortem intervals. The control animals stored at low temperature showed no ethanol in the bone marrow and blood until 21 days after sacrifice. Dosed rabbits stored at low temperature showed no significant changes in blood and marrow ethanol until 21 days after sacrifice.     

Differences between multisite postmortem ethanol concentrations as related to agonal events

In a study of postmortem ethanol concentrations, blood was withdrawn from the right atrium, ascending aorta, and inferior vena cava. These samples, vitreous humor, and gastric fluid were analyzed in 307 autopsies, where a minimum blood ethanol concentration of 0.05% weight/volume (w/v) was present. Premortem, agonal, and postmortem events were reviewed in an attempt to account for differences in blood ethanol concentrations between sites. The agonal aspiration of vomitus having at least 0.80% w/v ethanol appears to be associated with an increase in aortic ethanol concentrations. We conclude that valid interpretation of postmortem ethanol concentrations must take into consideration the possible entry of ethanol into the pulmonary venous circulation via the respiratory system.     

Comparative study of ethanol levels in blood versus bone marrow,vitreous humor,bile and urine

Post-mortem ethanol levels in blood were compared to corresponding levels in rib bone marrow, vitreous humor, urine and bile. In forensic toxicology, a good correlation between blood and a tissue or body fluid is needed to estimate a blood alcohol concentration when blood is unavailable or contaminated. In this study, direct injection and headspace gas-chromatographic techniques were employed to quantitate the ethanol concentrations. Comparable findings by these two techniques showed a reproducibility of results. When the determined bone marrow ethanol levels were corrected for the lipid fraction, a consistent correlation could be established between ethanol levels in blood and bone marrow. The relationship (linearity and ratio range) between ethanol levels in blood and corrected levels in bone marrow was better than that between blood and vitreous humor, bile or urine. This study showed that blood ethanol levels can be predicted by extrapolating the corrected rib bone marrow ethanol level.     

腐败血液中乙醇的顶空气相色谱分析

目的分析血液腐败后产生的乙醇及其他物质并探讨腐败血液中乙醇的检测及计算方法。方法以正常人空白血液制作腐败血样,采用1,4-二氧六环为内标物,通过顶空气相色谱进行定性及定量分析。结果血中乙醇在0.0625～1mg/mL范围内线性关系良好（r^2=0.9996）,各质量浓度组的变异系数（CV%）〈2%,血中乙醇的最低检出限为1μg/mL（S/N≥3）。腐败血样所产生乙醇与正丙醇的比例大致为25：1。结论检验方法简便、准确。为法医毒化检验相关工作提供了依据。     

An unusual case of post-mortem redistribution of ethanol

We report an unusual case of post-mortem redistribution of ethanol in a woman diver who died by drowning in seawater. The ethanol concentrations were right heart blood 0.60 g/l, left heart blood 2.08 g/l, femoral venous blood 0.63 g/l, gastric contents 5.87 g/l, bile 0.83 g/l. The mechanisms of post-mortem redistribution of ethanol described in the literature, that is, early redistribution from the stomach or the lung parenchyma in the case of inhalation of gastric contents, are inadequate to account for the degree of variation observed between the measurements. We believe that this difference in concentration is explained by the presence of seawater in the pulmonary alveoli at the time of death.     

Interpreting results of ethanol analysis in postmortem specimens: a review of the literature

We searched the scientific literature for articles dealing with postmortem aspects of ethanol and problems associated with making a correct interpretation of the results. A person's blood-alcohol concentration (BAC) and state of inebriation at the time of death is not always easy to establish owing to various postmortem artifacts. The possibility of alcohol being produced in the body after death, e.g. via microbial contamination and fermentation is a recurring issue in routine casework. If ethanol remains unabsorbed in the stomach at the time of death, this raises the possibility of continued local diffusion into surrounding tissues and central blood after death. Skull trauma often renders a person unconscious for several hours before death, during which time the BAC continues to decrease owing to metabolism in the liver. Under these circumstances blood from an intracerebral or subdural clot is a useful specimen for determination of ethanol. Bodies recovered from water are particular problematic to deal with owing to possible dilution of body fluids, decomposition, and enhanced risk of microbial synthesis of ethanol. The relationship between blood and urine-ethanol concentrations has been extensively investigated in autopsy specimens and the urine/blood concentration ratio might give a clue about the stage of alcohol absorption and distribution at the time of death. Owing to extensive abdominal trauma in aviation disasters (e.g. rupture of the viscera), interpretation of BAC in autopsy specimens from the pilot and crew is highly contentious and great care is needed to reach valid conclusions. Vitreous humor is strongly recommended as a body fluid for determination of ethanol in postmortem toxicology to help establish whether the deceased had consumed ethanol before death. Less common autopsy specimens submitted for analysis include bile, bone marrow, brain, testicle, muscle tissue, liver, synovial and cerebrospinal fluids. Some investigators recommend measuring the water content of autopsy blood and if necessary correcting the concentration of ethanol to a mean value of 80% w/w, which corresponds to fresh whole blood. Alcoholics often die at home with zero or low BAC and nothing more remarkable at autopsy than a fatty liver. Increasing evidence suggests that such deaths might be caused by a pronounced ketoacidosis. Recent research has focused on developing various biochemical tests or markers of postmortem synthesis of ethanol. These include the urinary metabolites of serotonin and non-oxidative metabolites of ethanol, such as ethyl glucuronide, phosphatidylethanol and fatty acid ethyl esters. This literature review will hopefully be a good starting point for those who are contemplating a fresh investigation into some aspect of postmortem alcohol analysis and toxicology.     

Stability of diazepam in blood samples at different storage conditions and in the presence of alcohol

Diazepam is one of the mostly used benzodiazepines and it is frequently analyzed in different biological samples, especially blood samples. The diazepam stability in the sample matrices is an important factor regarding reliable data obtaining. The storage is the main factor determining the stability of diazepam in blood samples and it is the object of the study presented. Remaining diazepam amount in spiked whole blood and plasma samples were tested at different storage temperatures, in the absence or presence of sodium fluoride as stabilizer as well as the influence of ethanol on diazepam stability was evaluated. The results of the study indicated that the temperature is the main storage factor affecting diazepam stability. In the fluoride stabilized blood samples the amount of diazepam decreases up to 85% of initial level when stored at -20° C for the period of testing (12 weeks). The presence of low (0.5 g/L) or high (3g/L) ethanol concentrations influences the stability of diazepam at -20 °C. In whole blood samples, the combination of sodium fluoride and ethanol decreases additionally (15-25%) the concentration of the analyte. Freeze-thaw experiments of whole blood samples show about 5-9% decrease in diazepam concentration after the first cycle. The freeze-thaw experiments on plasma samples, containing ethanol and/or fluoride show insignificant decreases of analyte concentration. Further experiments on benzodiazepines stability at different storage conditions or in combination of different factors should be undertaken in forensic toxicology to ensure the data quality, their reliability and reproducibility.     

The effect of ibuprofen on ethanol concentration and elimination rate.

Pursuant to a recent driving under the influence (DUI) case, a medical study of six subjects was cited reporting that ibuprofen causes a decrease in the maximum rate of elimination of ethanol. Such a drug interaction is of significant forensic science interest and warrants further examination. This study investigates the effect of ibuprofen on ethanol elimination rate and ethanol concentration in nineteen volunteers. Volunteer subjects were randomly assigned to two groups administered either a placebo followed by ethanol or ibuprofen followed by ethanol. Subjects served as their own control. Blood ethanol concentrations were monitored every 30 to 60 min for up to 4 h with Intoximeter 3000 instruments. A blood sample was drawn at the final Intoximeter test and analyzed for ethanol and ibuprofen by gas chromatography and mass spectrometry, respectively. The mean elimination rate (+/- SD) as calculated using Widmark's elimination factor was 0.018 +/- 0.006 g/dL for ethanol and 0.017 +/- 0.007 g/dL/h for ethanol with ibuprofen. Mean ethanol concentrations (g/dL +/- SD) were: 0.095 +/- 0.026 (ethanol) and 0.095 +/- 0.033 (ethanol and ibuprofen) at 30 min; 0.077 +/- 0.026 (ethanol) and 0.075 +/- 0.031 (ethanol and ibuprofen) at 150 min; and 0.089 +/- 0.025 (ethanol) and 0.087 +/- 0.030 (ethanol and ibuprofen) overall. There was no statistically significant affect of ibuprofen on either the peak blood ethanol concentration or the ethanol elimination rate (p less than or equal to 0.001). These results reveal no evidence of a significant ethanol-ibuprofen interaction.     

Evaluation of breath alcohol instruments II. In vivo experiments with Alcolmeter Pocket Model

The precision and accuracy of an Alcolmeter Pocket Model breath alcohol instrument have been investigated in experiments with human subjects under controlled conditions. The instrument response was zero in all tests with breath samples from alcohol-free subjects. The standard deviations of ethanol determinations in breath were ±0.0722 mg/ml during ethanol absorption and ±0.0416 mg/ml during ethanol elimination. The standard deviation during the elimination phase increased with ethanol concentration in the sample, being ±0.0416 mg/ml on average at a mean concentration of 0.420 mg/ml, corresponding to a coefficient of variation of 9.9%.The blood alcohol estimates using the Alcolmeter were somewhat too high during active absorption of ethanol, and too low during elimination, when a constant blood-breath alcohol ratio of 2100:1 was used to calibrate the instrument. During the elimination phase of ethanol kinetics and at a mean blood alcohol concentration of 0.50 mg/ml, the mean Alcolmeter result was 0.456 ± 0.169 mg/ml with 95% confidence, i.e. varying between 0.287 and 0.625 mg/ml 95 times out of 100 tests at this critical blood alcohol level.     

The unreliability of using a urine ethanol concentration to predict a blood ethanol concentration

Of approximately 5,000 forensic cases with a positive ethanol result, over 1,000 were available in which both blood and urine were present for comparison of ethanol content. Data were examined for calculation of the urine to blood ethanol concentration ratio, with the intent of evaluating the validity of predicting a blood ethanol level given a urine ethanol level. The overall urine to blood ethanol concentration ratio was 1.57:1 with a range of 0.7 to 21.0:1. The extremely wide range of values implies that a large degree of error would be introduced if a mean ratio was used when predicting a blood ethanol level from a urine ethanol level.     

The influence of physical properties and lipid content of bile on the human blood/bile ethanol ratio

The relationship between ethanol levels in blood and bile was determined in human postmortem specimens. The influences of several physical properties--surface tension, specific gravity and viscosity--and bile lipid content on the blood/bile ethanol ratio were evaluated. A gas chromatographic direct injection technique was employed to determine the ethanol concentrations in postmortem blood and bile specimens. A positive correlation was established between the levels in the two fluids. No correlation could be found between the blood/bile ethanol ratios and the aforementioned physical properties of bile. Correction of the observed bile ethanol for lipid content had an insignificant effect on the ratio. The average blood/bile ethanol ratio was 1.03 +/- 0.29 (range: 0.32-2.91). The wide range observed makes it undesirable to use bile ethanol concentrations to predict specific blood ethanol concentrations. However, under certain conditions, bile ethanol levels may be used to estimate blood concentrations within a range of values.