Elsevier

Journal of Chromatography A

Volume 1289, 10 May 2013, Pages 13-18
Journal of Chromatography A

“Dilute & Shoot” approach for rapid determination of trace amounts of nicotine in zero-level e-liquids by reversed phase liquid chromatography and hydrophilic interactions liquid chromatography coupled with tandem mass spectrometry-electrospray ionization

https://doi.org/10.1016/j.chroma.2013.02.078Get rights and content

Abstract

Two analytical procedures are proposed where HILIC and RPLC techniques are coupled with tandem mass spectrometry detection for rapid determination of trace amounts of nicotine in zero-level liquids for electronic cigarettes. Samples are prepared on the basis of the approach “dilute & shoot” which makes this important step quick and not complicated. The chromatographic separation was carried out on a Zorbax XDB column (RPLC method) and Ascentis Si column (HILIC mode). Within-run precisions (CVs) measured at three concentration levels were as follows: 0.73%, 0.98% and 1.44% for RPLC method and 1.39%, 1.44% and 0.57% (HILIC mode). Between-run CVs were as follows: 1.94%, 1.02% and 1.22% for RPLC mode and 1.49%, 1.20% and 1.22% for HILIC mode. The detection limits of RPLC and HILIC modes were 4.08 and 3.90 ng/mL respectively. The proposed procedures are rapid, not complicated, sensitive and are suitable for fast determination of trace amounts of nicotine in zero-level liquids for electronic cigarettes.

Highlights

► Determination of trace amount of nicotine in zero-level e-liquids. ► Two chromatographic methods based on RPLC and HILIC. ► First research on nicotine content in e-liquids denoted as 0 mg. ► Over forty analyzed samples from different producers.

Introduction

Tobacco leaves are rich with closely related alkaloids like: nicotine, anabasine, anatabine, nornicotine, nicotyrine, myosmine, 2,3′-dipyridyl and cotinine [1]. The most popular and well known alkaloid is nicotine due to its potential as one of the most addictive substances. From the pharmaceutical point of view nicotine plays an important role as the agent responsible for numerous behavioural and physiological effects [2], [3], [4], [5]. There are many ways to consume the tobacco and receive nicotine. Nicotine products can be divided into those that produce smoke like cigarettes, pipes or cigars and to those that do not produce smoke for instance gums and inhalers [3].

Recently, manufacturers mainly located in China have been producing electronic cigarettes and equipment for them. Such devices are powered by batteries and produce vapour from liquid containing nicotine and mixture of glycols (mainly polypropylene glycol as solvent) [6]. The cartridges are filled with liquids that contain different amount of nicotine and flavours. Sometimes colourants are used to encourage potential customers. The content of specific flavours (fruits, mint, branded cigarettes taste) can simulate the real sensations of cigarette smoking [6], [7]. Some cartridges and liquids may contain nicotine at trace amount level [8].

There are some known analytical procedures for the determination of nicotine and its derivatives in various types of samples. Up to now UV detection has been frequently applied for the determination of nicotine [9], [10], [11], [12], [13], [14], [15]. Information found in recent publications indicate that the most popular ones are based on the application of high and ultra performance liquid chromatography (HPLC and UPLC), coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) [4], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25] due to sensitivity, confidence and versatility. Gas chromatography coupled with flame ionization detection [1], MS and MS/MS [24], [26], [27], [28], [29], [30], [31], [32], time-of-flight MS [33], [34], electron capture detector (ECD) [35], nitrogen chemiluminescence detection [36] or nitrogen–phosphorous detection (NPD) [37] is used as well for determination of nicotine concentration. Moreover, developed methods with the use of capillary electrophoresis coupled with UV detection [38], [39], MS [40] and electrochemiluminescence detector [41] have been reported for the determination of nicotine. Detection by UV is not as sensitive as MS/MS detection and further analysis and evaluation of nicotine content in zero-level liquids have to be done.

The aim of the project was to develop a rapid, simple and sensitive methods for the determination and quantification of nicotine in zero-level liquids for electronic cigarettes by reversed phase liquid chromatography (RPLC) and by hydrophilic interactions liquid chromatography (HILIC) coupled with tandem mass spectrometry-electrospray ionization in multiple reaction monitoring (MRM) mode. Sample preparation is based on the approach “dilute & shoot” due to simple and stable composition of the matrix. Two proposed analytical methods allow determining the concentration of nicotine at trace amount in zero-level liquids in less than 4 min per single analysis run.

Section snippets

Chemicals

Standards of racemic nicotine, acetaminophen (internal standard for the RPLC mode of separation), pyridoxine hydrochloride (vitamin B6; internal standard for the HILIC mode of separation) and ammonium formate were purchased from Sigma–Aldrich (St. Louis, USA). Acetonitrile HPLC gradient (ACN) and methanol HPLC gradient (MeOH) were purchased from Merck KGaA (Darmstadt, Germany). Formic acid (FA) and ethanol were purchased from POCH (Gliwice, Poland). Propylene glycol and glycerol were purchased

Linearity, LOD, LOQ and matrix influence

Calibration curves were constructed using the internal standard method. Seven calibration solutions were made from standard solutions of nicotine as described in Section 2.3. Each calibration solution contained a specific amount of IS (100 ng/mL of acetaminophen for RPLC mode and 200 ng/mL of pyridoxine for HILIC mode). Each solution was analyzed three times. The values of limits of detection (LODs) were calculated by multiplying the constant term in the equation of the calibration curve by 3.3

Conclusions

Current trends allow smokers to use tobacco substitutes containing nicotine in various forms including the latest fashion: electronic cigarettes. There is a lot of controversy about the use and safety of electronic cigarettes and some countries (Australia, Hong Kong, Brazil) prohibit their sale. Other countries such as Poland, Belgium, and Germany have not introduced so far legal restrictions on the e-cigarettes. This means that the nicotine content in liquids for filing e-cigarettes is not

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