LC–APCI–MS Simultaneous Determination of Barbital, Amobarbital, Phenobarbital and Secobarbital in Human Plasma

New approach for barbiturates, phenytoin, methyprylon and glutethimide determination and fragmentation (UHPLC-MS/MS)

Barbiturates which are old pharmaceutical drugs are still widely used in medical treatment of epilepsy and for general anesthesia. To date, more than 2500 different barbituric acid analogs have been synthesized, and 50 of them were introduced into medical use over the last century. Due to their highly addictive properties, pharmaceuticals containing barbiturates are under strict control in many countries. However, by considering the worldwide problem with new psychoactive substances (NPS) the introduction of new designer barbiturate analogs into the dark market might serve a serious public health problem in the near future. For this reason there is an increasing need for application methods for barbiturates monitoring in biological samples. The UHPLC-QqQ-MS/MS method for determination of 15 barbiturates, phenytoin, methyprylon and glutethimide was developed and fully validated. The biological sample volume was reduced to only 50 µL. A simple LLE (pH 3 with ethyl acetate) was successfully applied. The lower LOQ was 10 ng/mL. The method enables differentiation of structural isomers: hexobarbital and cyclobarbital; as well as amobarbital and pentobarbital. Chromatographic separation was achieved with the use of the alkaline mobile phase (pH 9) and Acquity UPLC BEH C18 column. Furthermore, the novel fragmentation mechanism of barbiturates was proposed, which may have a great impact in identification of novel barbiturates analogs introduced to illegal marketplaces. The presented technique has a great potential to be applied in forensic, clinical and veterinary toxicological laboratories, as was evidenced by the positive results of international proficiency tests.

Nano-probe for determination of phenobarbital of green synthesized fluorescent carbon dots using Scrophularia striata

In this study, using a thirsty plant extract and a simple hydrothermal method, a nano-probe was introduced to detect the phenobarbital based on fluorescence. Functional groups, particle size, surface morphology, and types of elements were identified using analysis such as FTIR, TEM, SEM, EDX, respectively. The excitation at 355 nm and emission intensity at 446 nm for nano-probe, the nano-probe shows that various parameters such as pH, temperature, and time were investigated for optimization conditions. After optimizing the factors affecting the sensor's response, a linear range between 0 and 750 µM with a detection limit of 5 µM was obtained. Then, the effect of interfering with other materials was investigated and finally, the ability of this sensor to measure the phenobarbital in real samples has been studied.

Rapid quantification of phenobarbital and barbital in human whole blood by liquid-liquid extraction combined with DART-orbitrap-HRMS

PURPOSE

This study aims to develop and validate a rapid, simple, and efficient bioanalytical method for the simultaneous quantification of phenobarbital and barbital in human whole blood using liquid-liquid extraction combined with direct analysis in real time (DART) and high-resolution mass spectrometry (HRMS).

METHOD

Phenobarbital-d5 and aprobarbital were selected as internal standards (ISs) of phenobarbital and barbital, respectively. A mixed solvent of o-xylene and ethyl acetate at a ratio of 1:6 was used to extract analytes of interest and ISs from 100 μL of human whole blood samples. Phenobarbital and barbital were detected by DART-HRMS. The proposed method has been validated in accordance with United States Food and Drug Administration Guidelines for Bioanalytical Method Validation in terms of selectivity, linearity, accuracy, precision, matrix effect, recovery, stability, and dilution integrity.

RESULTS

The lower limits of quantification (LLOQs) of phenobarbital and barbital were both 10 ng/mL. The linearities were in the range of 10-1000 ng/mL (R² ≥ 0.99). The mean recovery values of phenobarbital and barbital were 99.7% and 88.1%, respectively. The interday and intraday precision values were less than 10.4%, and the interday and intraday accuracy values ranged from 87.6 to 106.7%. Furthermore, the validated method was applied to four cases of phenobarbital poisoning at the Shanghai Institute of Forensic Science.

CONCLUSION

The developed and fully validated method enabled the simultaneous quantification of phenobarbital and barbital in human whole blood and was successfully applied to authentic cases.

Quantitative Determination of Methohexital in Human Whole Blood by Liquid Chromatography Tandem Mass Spectrometry

A rapid, simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of methohexital in human whole blood was developed and validated. Ethyl acetate/n-hexane (9:1) was used as extraction solvent while aprobarbital was used as internal standard. Methohexital was recovered by liquid-liquid extraction from 100 μL of human whole blood. The mobile phase was water-acetonitrile, and an ACQUITY BEH C18 (2.1 × 100 mm, 1.7 μm) column was adopted. Negative electrospray ionization source and multiply reaction monitoring mode were applied. The transitions of m/z were 261.2/42.2 and 261.2/119.0 for methohexital. The limit of detection was 0.5 ng/mL, which was lower than the previous methods. Wide linear range (2-2,000 ng/mL) with a good correlation coefficient (r > 0.99) was also obtained. The intra- and inter- day precisions represented by relative standard deviation were <11.5%, and the recoveries were >79.67%. This analytical method involved small sample volume and had been proven to be rapid, easy, sensitive and specific. Therefore, it could be used for the clinical analysis of methohexital.