Determination of Barbiturates in Biological Specimens by Flat Membrane-Based Liquid-Phase Microextraction and Liquid Chromatography-Mass Spectrometry.

The wide abuse of barbiturates has aroused extensive public concern. Therefore, the determination of such drugs is becoming essential in therapeutic drug monitoring and forensic science. Herein, a simple, efficient, and inexpensive sample preparation technique, namely, flat membrane-based liquid-phase microextraction (FM-LPME) followed by liquid chromatography-mass spectrometry (LC-MS), was used to determine barbiturates in biological specimens. Factors that may influence the efficiency including organic extraction solvent, pH, and composition of donor and acceptor phases, extraction time, and salt addition to the sample (donor phase) were investigated and optimized. Under the optimized extraction conditions, the linear ranges of the proposed FM-LPME/LC-MS method (with correlation coefficient factors ≥ 0.99) were 7.5-750 ng mL-1 for whole blood, 5.0-500 ng mL-1 for urine, and 25-2500 ng g-1 for liver. Repeatability between 5.0 and 13.7% was obtained and the limit of detection (LOD) values ranged from 1.5 to 3.1 ng mL-1, from 0.6 to 3.6 ng mL-1, and from 5.2 to 10.0 ng g-1 for whole blood, urine, and liver samples, respectively. This method was successfully applied for the analysis of barbiturates in blood and liver from rats treated with these drugs, and excellent sample cleanup was achieved.

[Distribution of tramadol in acute poisoned rats].

OBJECTIVE: To develop a rapid and accurate gas chromatography method and investigate the distribution of tramadol in acute poisoned rats for information of samples selection and results evaluation in forensic identification. METHODS: After an oral administration of tramadol at 1140 mg/kg (5 x LD50), concentrations of tramadol in rats' biological fluids and tissues were determined by gas chromatography. RESULTS: The limit of detection of tramadol in blood and urine was 0.1 microg/mL and the limit of detection in liver was 0.1 microg/g. The intra-day precision and inter-day precision were within 3.1% and 5.5% respectively, and the recovery of tramadol in blood was more than 98%. The average levels of tramadol displayed in descending order of heart blood, liver, peripheral blood, urine, vitreous humor, kidney, lung, spleen, heart, brain respectively. CONCLUSION: The established method could meet the requirements for toxicological analysis, and the results of the study suggest that blood, urine, liver, lung and kidney are suitable samples for forensic toxicological analysis in tramadol poisoning cases.

Spectrophotometric determination of trimethylamine-nitrogen in cadaver tissues for the estimation of late postmortem interval: a pilot study.

To study the relationship between the late postmortem interval (PMI) and trimethylamine-nitrogen (TMA-N) in postmortem tissues of cadaver, TMA-N in muscles, livers and kidneys of rats was measured at different postmortem intervals (PMI) by using a modified spectrophotometric method. The results indicated that the detection sensitivity of TMA-N was 1 mg/L, and there was a good linear correlation between the value of absorbance (A value) and TMA-N at the concentration of 1-10 mg/L (R (2) = 0.9991). Although TMA variation in muscles was different from that in inner organs during the time since death, TMA-N changes in cadaver tissues was positively correlated with PMI. During 2 to 7 d since death, the best correlation between PMI and TMA-N concentration was found in muscles. With PMI as an independent variable, the cubic polynomial regression equation was y= -0.457x(3)+6.519x(2)-24.574x+27.207 (R (2)=0.969). During 3 to 8 days since death, PMI was best correlated with TMA-N concentration in inner organs. With PMI as the independent variable, the cubic polynomial regression equation was y=0.509x(3)-9.153x(2)+55.727x-95.819 (R (2)=0.953). It was concluded that TMA-N in tissues could be used as a new estimator for late PMI. The method used in this study offered advantages such as accuracy, sensitivity, little samples required and wide PMI estimation.

Spectrophotometric Determination of Trimethylamine-nitrogen in Cadaver Tissues for the Estimation of Late Postmortem Interval: A Pilot Study / 华中科技大学学报（医学）（英德文版）

To study the relationship between the late postmortem interval (PMI) and trimethylamine-nitrogen (TMA-N) in postmortem tissues of cadaver, TMA-N in muscles, livers and kidneys of rats was measured at different postmortem intervals (PMD by using a modified spectrophotometric method. The results indicated that the detection sensitivity of TMA-N was 1 mg/L, and there was a good linear correlation between the value of absorbance (A value) and TMA-N at the concentration of 1-10 mg/L (R2 =0.9991). Although TMA variation in muscles was different from that in inner organs during the time since death, TMA-N changes in cadaver tissues was positively correlated with PMI. During 2 to 7 d since death, the best correlation between PMI and TMA-N concentration was found in muscles.With PMI as an independent variable, the cubic polynomial regression equation was y= --0.457x3+6.519x2-24.574x+27.207 (R2=0.969). During 3 to 8 days since death, PMI was best correlated with TMA-N concentration in inner organs. With PMI as the independent variable, the cubic polynomial regression equation was y=0.509x3-9.153x2+55.727x-95.819 (R2=0.953). It was concluded that TMA-N in tissues could be used as a new estimator for late PMI. The method used in this study offered advantages such as accuracy, sensitivity, little samples required and wide PMI estimation.