Helping Forensic Labs Handle Greater Demand for Blood Alcohol Analysis

Around the world, the potential risks of drinking alcohol and driving a vehicle cause concern for public safety. In recent years, many countries have taken steps intended to either reduce the incidence of impaired driving or enable tighter enforcement of associated laws. As examples, raising the minimum legal drinking age is a common preventive measure and lowering the maximum allowable blood alcohol content (BAC) is often used to enable tighter enforcement.

Strict enforcement of a lower blood-alcohol level may increase public safety, but it also puts a greater burden on the forensic labs that perform BAC analysis. Measuring volatiles such as ethanol in complex biological fluids is a difficult process that doesn't lend itself to typical high-throughput testing methods. To reduce the likelihood of backlogs in testing—and delays in legal and insurance proceedings—labs need analytical tools that can improve throughput while maintaining accuracy and repeatability.

Ensuring accurate analysis

BAC analysis determines the amount of ethanol in a given volume of blood, noted as "weight by volume" and usually measured in milligrams per deciliter (mg/dl) or milligrams per milliliter (mg/ml). The BAC threshold for "driving under the influence" (DUI) varies from country to country, with zero being the lowest, 1.0 mg/ml the highest and 0.5 mg/ml the most typical.

Gas chromatography (GC) is usually the preferred measurement method, and accurate analysis of BAC via GC depends on a sample-introduction method that minimizes the possibility of inlet contamination. This is a key advantage of headspace sampling (HSS), which reduces the potential for errors that are common to other GC sample-preparation techniques. HSS does this by allowing introduction of volatile compounds directly into a GC or GC/mass spectrometry system.

Creating an integrated solution

Agilent was the first to offer an automated HSS system that used the proven combination of pressurized vials with a fixed-volume sample loop. Today, the Agilent G1888 network headspace sampler features an inert sample pathway and provides significant advantages in sensitivity, performance and lab productivity.

The network HSS works with the Agilent 6890N GC and ChemStation software to create a fully integrated system that performs sampling, separation, detection, data analysis and reporting. The GC provides reduced inlet and column maintenance, better quantitation, limited sample preparation and increased throughput. With an optional software add-on, ChemStation can completely control the network HSS, enabling greater integration and ensuring FDA 21 CFR Part 11 compliance for the entire HSS/GC system.

Demonstrating an improved method

The Agilent G1888 network headspace sampler increases user productivity via features such as a 70-sample tray and a screw-cap vial ideal for field sampling.

The Agilent application note "Static Headspace Blood Alcohol Analysis with the G1888 Network Headspace Sampler" describes use of the HSS/GC system for BAC testing. For their experiments, the authors equipped the system with dual columns designed specifically for BAC analysis. Dual-column systems produce a different elution order for ethanol and other metabolites—a capability that provides added confirmation of BAC level and a potential reduction in possible interferences or co-elutions with ethanol.

One of the system's key benefits is reduced carryover, which is enabled by the combined effects of an inert flow path, excellent thermal control and programmable vent purge operations. The system also improves throughput by achieving typical cycle times of less than five minutes, depending on the internal standards chosen for GC-based blood alcohol analysis.

The results presented in the note show that the network HSS can be a productive addition to any forensic lab. With the ongoing trend toward lower maximum allowable BAC and tighter enforcement of DUI regulations, equipment that can support higher throughput—while retaining accuracy and repeatability—will become increasingly valuable.

For more information

To learn more about Agilent solutions that can enhance your lab, please see the Forensics section of our website. For additional information about these and other Agilent life sciences products and resources, please visit the Life Sciences/Chemical Analysis main page.