The Benefits of DBS-GC–MS/MS in Barbiturate Detection

A team from the Academy of Forensic Science in Shanghai and China Pharmaceutical University has conducted a comparative analysis of three instrumental methods—gas chromatography–mass spectrometry (GC–MS), gas chromatography–tandem mass spectrometry (GC–MS/MS), and liquid chromatography–tandem mass spectrometry (LC–MS/MS)—alongside liquid-liquid extraction (LLE) and dried blood spot (DBS) in the pre-treatment stage for the quantitation and characterization of barbiturates (1).

illustration of a barbiturate molecule in detail, perfect for educational and medical purposes, set against a white background. | Image Credit: © ckybe - stock.adobe.com

Barbiturates are a class of depressant drug used to help aid sleep, prevent seizures, and relieve anxiety. They require precise detection methods as a correct dose can be difficult to calculate (2). Tolerance can develop very quickly meaning that an increased dose will be required to achieve the same effect each time (3). They are commonly used for the treatment of epilepsy, alongside combination drugs such as levetiracetam, dexmedetomidine, scopolamine, carbamazepine, diazepam, and promethazine (1).

The team assessed the merits of LC and GC in an analysis of this kind. Using LC–MS/MS to quantify barbiturates alongside their combination drugs can present a challenge because of the need for electrospray ionization (ESI). Barbiturates need to be detected in the negative ion mode, while their combination drugs require the positive ion mode for detection. Therefore the GC method was preferred over LC as it can operate in multiple reaction monitoring (MRM) mode without requiring polarity switching, enabling faster, more comprehensive compound analysis—a clear advantage when dealing with patients with acute barbiturate poisoning.

Acquiring the samples needed was another key element of this study. The team investigated DBS as a potential alternative to LLE. DBS is a very quick and minimally invasive way of collecting a sample for analysis, meaning there is lower reagent consumption, making it both environmentally friendly and cost-effective.

The team ultimately decided to utilize a DBS-GC–MS/MS method for the detection of barbiturates. GC–MS/MS offered a higher signal-to-noise ratio and greater sensitivity than GC–MS, making it the best option for the analysis (1). The method achieved high sensitivity, with limits of detection (LOD) and limits of quantification (LOQ) at 0.1 μg/mL and 0.2 μg/mL, respectively. It also offered linearity (R² > 0.9992), precision (< 15%), and trueness (< 15%) across most compounds, except for carbamazepine at 29.4%. Recovery rates for most barbiturates were good, but matrix effects were in evidence.

The team concluded that the DBS-GC–MS/MS method is particularly suited for both qualitative and quantitative barbiturate analysis, especially in poisoning cases involving multiple drug combinations. They suggest that there should be broader adoption of DBS in clinical and forensic laboratories as it has many advantages to offer.

References

(1) Zhi, Y.; Lu, J.; Zheng, Q.; et al. Evaluating the Detection of Barbiturates in Dried Blood Spots: A Comparative Analysis Using Gas Chromatography-Mass Spectrometry, Gas Chromatography-Tandem Mass Spectrometry, and Liquid Chromatography-Tandem Mass Spectrometry with Different Extraction Methods. J. Chromatogr. A 2024, 1737, 465434. DOI: 10.1016/j.chroma.2024.465434

(2) Barbiturate Misuse, WebMD. https://www.webmd.com/mental-health/addiction/barbiturate-abuse(accessed 2024-12-03).

(3) United States Drug Enforcement Administration, Barbiturates Drug Fact Sheet; https://www.dea.gov/sites/default/files/2023-02/Barbiturates%202022%20Drug%20Fact%20Sheet.pdf(accessed 2024-12-03).