Purpose: We investigated validation and optimization of ultrasound-assisted dispersive liquidliquid microextraction (UADLLME) as a preparation method for detection of methadone in saliva samples. Methods: We used blank and methadone-containing saliva samples and also standard methadone solution. Sodium hydroxide and chloroform were added to samples and they were held in ultrasonic bath. Then preparations were centrifuged and extracted analyte was analyzed by gas chromatography-mass spectrometry (GC-MS). Accuracy was measured by Intra and between-day mean relative errors (RE). Precision was assessed by coefficient of variation (CV). Recovery, specificity, linearity and limits of detection and quantification were also determined. Optimization was conducted for ultrasound duration, pH and extraction phase volume. Efficiency of dispersive liquid-liquid microextraction (DLLME) and UADLLME were compared. Results: Intra and between-day accuracies (2.3 -7.5%), recovery (89.4-115.5%) and precision (5.2-11.3%) were all acceptable. Calibration curve was linear in the concentration range of 150 ng/mL-10 µL/mL with R2 >0.9995 and equation of y=86.901x-5342.5. Limits of detection and quantification were 50 and 150 ng/mL, respectively. Specificity was measured by comparing retention times of saliva samples (containing methadone metabolites and other commonly used drugs) during UADLLME/GC-MS analysis and no interference was observed. Recovery of UADLLME was 1.4 of DLLME. Solvent and sample volumes required for UADLLME were 1/200 and 1/20 of DLLME. The greatest efficiency obtained at pH of 10, with ultrasound treatment duration of 5 minutes and extraction phase volume of 1000 µL. Conclusion: Study found that UADLLME/GC-MS is a valid and efficient method for detection of methadone in oral fluid.
Background: Methamphetamine (meth) is recognized as a highly addictive psychostimulant. Currently, there are no available treatments for meth abuse, and no animal model of meth self-administration has been proposed to represent human meth selfadministration. Objectives: We aimed to develop a model to study meth self-administration through inhalation in rats. Methods: Rats were placed in an inhaler apparatus (designed specifically for this purpose) for 15 min per day over two weeks. There were two levers in the cage. Pressing the passive lever had no outcomes. Whereas, for each active lever pressing, an infusion pump delivered 50 µL of meth or distilled water within two seconds. Meth was evaporated on a hot plate adjacent to the rat cage. After loading the drug over the hot plate, the blower fan was run, and the vaporized drug was blown by the fan into the rat cage. Then, meth-induced conditioned place preference and locomotor activity were assessed following 14 days of meth inhalation. The serum concentration of meth was also determined by gas chromatography-mass spectrometry. Results: In this model, the self-administration of meth through inhalation significantly increased locomotor activity, conditioned place preference, and plasma level of meth. Conclusions: We can conclude that the self-administration of meth through inhalation is a novel and effective route of selfadministration. Our new protocol presents a promising tool for examining drug-seeking/taking behaviors and neural consequences in a noninvasive approach to reduce the stress of surgery and injection in laboratory animals and increase the validity of animal experiments.
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