Determination of morphine and oxymorphone in exhaled breath condensate samples: Application of microwave enhanced three–component deep eutectic solvent-based air–assisted liquid–liquid microextraction and derivatization prior to gas chromatography–mass spectrometry

Highlights

• A microwave enhanced microextraction/derivatization method was developed.

• A new ternary deep eutectic solvent was prepared and used as an extraction solvent.

• The method was used to extract morphine and oxymorphone in EBC samples.

• Greenness, cheapness, and high efficiency are advantages of the method.

Abstract

In this work, a microwave–enhanced air–assisted liquid–liquid microextraction method combined with gas chromatography–mass spectrometry has been developed for morphine and oxymorphone assessment in EBC samples. For this purpose, choline chloride-menthol-phenylacetic acid deep eutectic solvent (as an extraction solvent), butyl chloroformate (as a derivatization agent), and picoline (as a catalyst) are used. After performing predetermined extraction cycles in the microextraction method, the obtained cloudy solution is exposed to microwave irradiations to enhance extraction and derivatization efficiencies. The method provided low limits of detection (morphine 2.1 and oxymorphone 1.5 ng mL⁻¹) and quantification (morphine 7.2 and oxymorphone 5.2 ng mL⁻¹) in the EBC samples. The method had proper repeatability, accuracy, and stability expressed as relative standard deviations less than 5.1, 9, and 9%, respectively. The developed method was successfully used to determine morphine and oxymorphone concentrations in the EBC samples of addict patients.

Introduction

The drugs obtained from opium termed as opiate (belong to benzylisoquinoline group) are an important class of the drugs of abuse [1]. Opiates are alkaloid compounds naturally prepared from opium poppy plant (morphine (MP) and codeine), and synthetically (hydromorphone, oxymorphone (OM), and hydrocodone) or semi–synthetically (hydromorphone, oxycodone, and hydrocodone) [2]. These compounds have high patient acceptance in the United States, Asia and Europe [3], [4]. MP is used in patients as alleviate in severe pains after a surgical operation [5], [6] or in cancer. Despite therapeutic indications, abuse of opiates is an important health disaster in the worldwide. Some studies show that MP and OM can cause disruption in central nervous system and cardiovascular problems. To make suitable medical decisions and control of drug abuse, a precise monitoring is advised [7], [8]. Urine and blood are the widely used samples for medical and forensic purposes. However obtaining urine or blood is not easy and in some cases, is impossible. Therefore exhaled breath condensate (EBC) is a good candidate for usage in clinical studies due to its non–invasive nature, quick and safe collection procedure [9], [10]. The studies showed that EBC have a relatively complex matrix by containing different compounds like carbohydrates, proteins, lipids, surfactants, and volatile organic compounds in which the target compounds concentration is low [11]. As a result, a pretreatment step is desired to preconcentrate the analytes and/or remove the interferences [12]. In recent years, liquid–liquid extraction [13], solid phase extraction [14], and cloud point extraction [15] as the traditional pretreatment methods were mainly replaced by microextraction methods [16]. Solvent microextraction (SME) and solid phase microextraction are the well-known microextraction methods. SME methods are mostly divided to three types including single drop microextraction [17], hollow fiber-liquid phase microextraction [18], and dispersive liquid–liquid microextraction (DLLME) [19]. Among these methods, DLLME attracted more attentions due to its outstanding advantages like high extraction efficiency, easy to use, and short extraction time. In DLLME, analytes are extracted into the tiny droplets of a water–immiscible solvent (extraction solvent) dispersed into the sample solution by a water–miscible solvent (dispersive solvent). In classical DLLME, the extraction and dispersive solvents are organic solvents which are used in microliter and milliliter levels, respectively. The use of organic solvents is not favored in DLLME due to their toxicity. Many attempts were performed to improve or replace the classical DLLME with other green methods. In recent years, sonication, vortexing, or microwave irradiations were used as good choices to replace the dispersive solvent used in DLLME [20]. It is clear that additional devices like sonication bath, vortex, or microwave oven are needed in these cases. Also, sonication and microwave irradiations may decompose the analytes. Due to these disadvantages air–assisted liquid–liquid microextraction (AALLME) was introduced [21]. It is performed by placing a few microliters of an organic solvent at the bottom of the tube filled with sample solution and the solvent is dispersed into the solution by sucking the mixture into a glass syringe and pushing out to the tube repeatedly. Several benefits such as high extraction efficiency, easiness, rapidity, and low consumption of organic solvents were stated for AALLME. To replace organic solvents with less toxic alternatives, deep eutectic solvents (DESs) and ionic liquids (ILs) were used in AALLME. Usually, a mixture of two solid substances capable of forming hydrogen bonding with together are used to prepare a DES. In this case, melting point of the formed DES is lower than those of the individual substances. Synthesis of DESs is easy and fast and they are easily biodegradable. Due to these properties, DESs are considered as a replacement for IL and organic solvents [22].

The main goal of the present work was to develop a DES-based AALLME method for the efficient extraction of MP and OM from EBC samples prior to their analyses by gas chromatography–mass spectrometry (GC-MS). Since the analytes are phenolic compounds and form hydrogen bond with the stationary phase of GC columns, peak tailing can be occurred which affects detection limit of the method. Thus a derivatization step is performed simultaneously during sample preparation step. Up to now, no report has been published regarding simultaneous derivatization and extraction of MP and OM in EBC samples.