Determination of alcohol content in blood by headspace gas chromatography
Beijing Huasheng Spectrum Instrument Co., Ltd.
When using this method to analyze ethanol levels in the blood of a driver or victim involved in a traffic accident, it's essential to understand and pay attention to several key factors to ensure accurate and reliable results.
An internal standard method using tebutanol is required. This approach is more precise than general methods, as the selection of an appropriate internal standard plays a critical role in the accuracy of headspace chromatography analysis.
There are three common units used to express blood alcohol content:
- Mg/mL – Milligrams of ethanol per milliliter of blood
- Mg% – Milligrams of ethanol per 100 milliliters of blood
- % – Grams of ethanol per 100 milliliters of blood
In official reports, the last two units are typically used. For example, if the measured value is 1.10 mg/mL, it would be expressed as 110 mg% or 0.11%. These values are legally binding and serve as crucial evidence in determining whether a driver was under the influence of alcohol.
Physiological responses vary significantly depending on blood alcohol concentration. Understanding these levels helps assess the risk and severity of impairment during driving.
Blood Alcohol Concentration and Symptoms
| BAC (Mg%) | Symptoms |
|---|---|
| <50 | Almost asymptomatic, slight changes in judgment and response time. |
| 50–100 | Redness, euphoria, impaired coordination and eye sensitivity. May cause accidents among inexperienced drinkers. |
| 100–150 | Increased talkativeness, emotional instability, reduced reasoning, and motor control issues. Risk of dangerous driving behavior. |
| 150–250 | Uncoordinated movement, confusion, slurred speech, and loss of motor control. Not safe to drive. |
| 250–350 | Difficulty walking, confusion, dilated pupils, and early signs of unconsciousness. |
| 300–400 | Deep drowsiness, slowed breathing, decreased body temperature, and no response to stimuli—life-threatening condition. |
| 400–500 | Coma, respiratory failure, and potential death. |
It's important to note that individual tolerance varies. Some people may show signs of intoxication at 30 mg%, while others remain functional at 150 mg%. Drinking on an empty stomach leads to faster and more severe effects, whereas eating before drinking may slow the onset of symptoms. Most individuals with BAC levels between 200–350 mg% will experience significant intoxication.
To estimate blood alcohol content from other biological samples, scientists use proportional coefficients based on experimental data. These coefficients allow indirect estimation of BAC from urine, saliva, plasma, or other tissues. Here are some typical values:
- Blood: 1.00
- Brain: 1.17
- Urine: 1.35
- Liver: 0.91
- Saliva: 1.30
- Blood clots: 0.77
- Plasma: 1.16
- Serum: 1.12
Beijing Huasheng Spectrum Instrument Co., Ltd. specializes in manufacturing and selling professional gas chromatographs and related accessories, providing reliable tools for forensic and scientific testing applications.
Wuxi Ark Technology Electronic Co.,Ltd. , https://www.arkledcn.com