Simultaneous quantitation of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma using solid-phase extraction and gas chromatography/mass spectrometry: Method validation and application to cardiovascular safety of therapeutic doses.

RATIONALE: Several opioid analgesics have been related to the prolongation of cardiac repolarization, a condition which can be fatal. In order to establish a correct estimation of the risk/benefit balance of therapeutic doses of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene, it was necessary to develop an analytical method to determinate plasma concentrations of these opioids. METHODS: Here we describe a method which incorporates strong alkaline treatment to obtain norpropoxyphene amide followed by a one-elution step solid-phase extraction, and without further derivatization. Separation and quantification were achieved by gas chromatography/electron ionization mass spectrometry (GC/EI-MS) in selected-ion monitoring mode. Quantification was performed with 500 µL of plasma by the addition of deuterated analogues as internal standards. RESULTS: The proposed method has been validated in the linearity range of 25-1000 ng/mL for all the analytes, with correlation coefficients higher than 0.990. The lower limit of quantification was 25 ng/mL. The intra- and inter-day precision, calculated in terms of relative standard deviation, were 2.0-12.0% and 6.0-15.0%, respectively. The accuracy, in terms of relative error, was within a ± 10% interval. The absolute recovery and extraction efficiency ranged from 81.0 to 111.0% and 81.0 to 105.0%, respectively. CONCLUSIONS: A GC/MS method for the rapid and simultaneous determination of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma was developed, optimized and validated. This procedure was shown to be sensitive and specific using small specimen amounts, suitable for application in routine analysis for forensic purposes and therapeutic monitoring. To our knowledge, this is the first full validation of the simultaneous determination of these opioids and their metabolites in plasma samples.

Nano-electromembrane extraction.

The present work has for the first time described nano-electromembrane extraction (nano-EME). In nano-EME, five basic drugs substances were extracted as model analytes from 200 µL acidified sample solution, through a supported liquid membrane (SLM) of 2-nitrophenyl octyl ether (NPOE), and into approximately 8 nL phosphate buffer (pH 2.7) as acceptor phase. The driving force for the extraction was an electrical potential sustained over the SLM. The acceptor phase was located inside a fused silica capillary, and this capillary was also used for the final analysis of the acceptor phase by capillary electrophoresis (CE). In that way the sample preparation performed by nano-EME was coupled directly with a CE separation. Separation performance of 42,000-193,000 theoretical plates could easily be obtained by this direct sample preparation and injection technique that both provided enrichment as well as extraction selectivity. Compared with conventional EME, the acceptor phase volume in nano-EME was down-scaled by a factor of more than 1000. This resulted in a very high enrichment capacity. With loperamide as an example, an enrichment factor exceeding 500 was obtained in only 5 min of extraction. This corresponded to 100-times enrichment per minute of nano-EME. Nano-EME was found to be a very soft extraction technique, and about 99.2-99.9% of the analytes remained in the sample volume of 200 µL. The SLM could be reused for more than 200 nano-EME extractions, and memory effects in the membrane were avoided by effective electro-assisted cleaning, where the electrical potential was actively used to clean the membrane.

Implementation of droplet-membrane-droplet liquid-phase microextraction under stagnant conditions for lab-on-a-chip applications.

In the current work, droplet-membrane-droplet liquid-phase microextraction (LPME) under totally stagnant conditions was presented for the first time. Subsequently, implementation of this concept on a microchip was demonstrated as a miniaturized, on-line sample preparation method. The performance level of the lab-on-a-chip system with integrated microextraction, capillary electrophoresis (CE) and laser-induced fluorescence (LIF) detection in a single miniaturized device was preliminarily investigated and characterized. Extractions under stagnant conditions were performed from 3.5 to 15 microL sample droplets, through a supported liquid membrane (SLM) sustained in the pores of a small piece of a flat polypropylene membrane, and into 3.5-15 microL of acceptor droplet. The basic model analytes pethidine, nortriptyline, methadone, haloperidol, and loperamide were extracted from alkaline sample droplets (pH 12), through 1-octanol as SLM, and into acidified acceptor droplets (pH 2) with recoveries ranging between 13 and 66% after 5 min of operation. For the acidic model analytes Bodipy FL C(5) and Oregon Green 488, the pH conditions were reversed, utilizing an acidic sample droplet and an alkaline acceptor droplet, and 1-octanol as SLM. As a result, recoveries for Bodipy FL C(5) and Oregon Green 488 from human urine were 15 and 25%, respectively.

[Selected psychoactive drugs--clinical problems and medical-legal aspects]. / Wybrane srodki odurzajace--problemy kliniczne i medyczno-sadowe.

The multifarious aspects of psychoactive drug use present a significant challenge to the contemporary analyst. During the first stage of the present experiment, the recovery from human serum and urine of some psychoactive drugs with acidic or basic properties was studied. The efficiency of this process was determined using solutions of drug standards added to serum or urine. Classic liquid-liquid extraction, as well as solid phase extraction methods were compared. The efficiency of recovery was checked using high-performance liquid chromatography (HPLC). The results of this study confirm the usefulness of RP-18 sorbent from Merck and the importance in terms of quantitative analysis of the technique selected for isolation of the xenobiotic from the biological material. The second stage of the experiment was aimed at qualitative determination of some narcotics using thin-layer chromatography (TLC). By stepwise comparison and elimination it was possible to develop an optimal system of chromatographic separation using laminar staining. The proposed system and the conditions for separation ofxenobiotics with six selected elution systems and laminar visualization confirm the feasibility of separating 22 psychoactive drugs. The practical use of the system is limited mainly to screening. Conditions for quantitative analysis of diazepam, tramadol, and pethidine in biological material (serum, urine) using high-performance liquid chromatography, as well as morphine in serum using an immunoenzyme assay have been developed. The procedures have been applied to analysis of narcotics and psychoactive drugs administered prior to anesthesia (morphine, diazepam, pethidine) or for suppression of post-operative pain (morphine, tramadol) in 31 patients of an intensive care unit. 10 ml of blood was drawn at fixed times: 30 minutes prior to surgery (S1), at start of surgery (S2), 60 minutes later (S3), 30 minutes after administration of analgesic (S4), and 60 minutes after administration of analgesic (S5). Urine samples were also collected: immediately after surgery (M1) and 90 minutes after administration of analgesic (M2).

[Separation and determination of morphine, pethidine and diazepam by high performance liquid chromatography].

Morphine, penthidine and diazepam in blood were determined by high performance liquid chromatography (HPLC). The HPLC system was consisted of 10 microns particle size C18 column and UV detector set at 254 nm. The mobile phase was V(CH3OH):V(25 mmol/L KH2PO4) = 90:10 with a flow rate of 1.0 mL/min. The average recoveries of morphine, penthidine and diazepam were 93.27%, 90.23% and 93.29% respectively. The linear range was between 0.05-50 mg/L. The detection limit was 0.05 mg/L and CV was less than 6%.

Clinical significance of methohexital, meperidine, and diazepam in breast milk.

Concentrations in breast milk of medications used during general anesthesia were measured to determine whether interruption of breast-feeding was indicated. Breast milk and maternal blood samples were obtained from nine women undergoing tubal sterilization under general anesthesia. Concentrations of methohexital, meperidine, diazepam, and nordiazepam were determined for each sample by gas chromatography. Methohexital levels declined rapidly after the first hour and were undetectable at 24 hours. Meperidine was present in both milk and blood during the recovery period but not at 24 hours. Infant-exposure indices for methohexital were less than 1% and ranged from 1.2% to 3.5% for meperidine. The maximum doses of methohexital and meperidine to an infant, in a 100 mL feeding 1 hour after induction of anesthesia were estimated to be 0.04 mg and 0.06 mg, respectively. Diazepam and nordiazepam were not detectable in any sample of milk or blood. The maximum possible infant-exposure index for diazepam would be 3%. The amounts of methohexital, meperidine and diazepam excreted into breast milk do not warrant interruption of breast-feeding.

Simultaneous determination of pethidine (meperidine), phenoperidine, and norpethidine (normeperidine), their common metabolite, by gas chromatography with selective nitrogen detection.

This article describes a selective gas chromatographic method for the resolution and quantification of phenoperidine and its two metabolites, pethidine (meperidine) and norpethidine (normeperidine). Drugs and SKF 525 A, the internal standard, are separated from plasma by solvent extraction under alkaline conditions. They are chromatographed on a 3% OV-17 Chromosorb Q glass column and detected with a nitrogen-phosphorous detector. Linearity is observed in the study range (5-200 ng/ml). No interference by endogenous substances is noted.