Ethanol is a volatile organic compound (VOC) that is commonly what is in the adult drinks we drink. In order to measure the concentration of ethanol in a person’s blood who accused of a DUI, a gas chromatograph (GC) equipped with a blood alcohol content (BAC) column can be used.
The BAC column is specially designed to separate and identify ethanol from other VOCs that may be present in the sample. The column is typically made of a stationary phase, such as a polymeric or silica material, that is coated with a specific chemical that selectively binds to ethanol. The sample is injected into the column and is then carried through the column by a carrier gas, such as helium or nitrogen.
As the sample passes through the column, the ethanol molecules are selectively retained on the column while other VOCs pass through more quickly. The retained ethanol molecules are then eluted, or removed, from the column using a higher temperature or a more polar solvent. The eluted ethanol is then detected by a flame ionization detector (FID) or other type of detector that can measure the concentration of ethanol in the sample.
However, in the process of separation, other VOCs can also be retained to some extent by the column and can co-elute with ethanol. These VOCs are called “co-eluters”. The co-eluters can interfere with the accurate measurement of ethanol concentration, and can also affect the overall selectivity of the column.
There are several factors that can contribute to co-elution of VOCs with ethanol in a GC-BAC column. One of the main factors is the chemical structure of the VOCs. VOCs that have a similar chemical structure to ethanol, such as methanol or isopropyl alcohol, are more likely to co-elute with ethanol. Additionally, VOCs that have a similar polarity to ethanol, such as acetone or acetic acid, are also more likely to co-elute.
Another factor that can contribute to co-elution is the operating conditions of the GC-BAC column. The temperature and flow rate of the carrier gas, as well as the elution solvent, can all affect the retention and elution of VOCs on the column. If the temperature or flow rate is too high, the VOCs may be eluted too quickly and may not be effectively separated from ethanol.
To minimize the co-elution of VOCs with ethanol in a GC-BAC column, several methods can be used. One of the most effective methods is to use a more selective column that has a higher selectivity for ethanol. This can be achieved by using a column that has a different stationary phase or by using a column that is coated with a different chemical that selectively binds to ethanol.
Another method that can be used is to optimize the operating conditions of the GC-BAC column. This can include adjusting the temperature and flow rate of the carrier gas, as well as the elution solvent. By carefully controlling these conditions, it is possible to achieve a better separation of ethanol from other VOCs.
In addition to these methods, the sample preparation also plays a critical role in minimizing co-elution. This includes properly storing the samples, avoiding cross-contamination, and reducing the sample volume.
In conclusion, co-elution of VOCs with ethanol in a GC-BAC column can be a problem that affects the accuracy of ethanol measurement. It takes extremely technically knowledgeable attorneys like us to spot science from science fiction.
Our Clients are entitled to a Bill of Rights which states:
- Our clients have the right to expect, we will be proactive in communication. You will hear it from us first. We will return all phone calls, texts and emails promptly.
- Our clients have the right to expect plain speaking, straight shooting. No B. S.
- Our clients have the right to expect us to do it right the first time, every time.
- Our clients have the right to expect us to be on time and professionally prepared for all court appearances, and all meetings.
- Our clients have the right to expect that they will be fully informed at all times.
This is our promise to you. Call today to get us on your side: (717) 657-3900.
