E-Cigarette Quality Control: Impurity and Nicotine Level Analysis in Electronic Cigarette Refill Liquids

Abstract

This work targets mainly the quality control of electronic cigarette liquids. It relies on an analytical control of a “32-product” sample made of several types of e-cigarette liquids taken from various supermarkets and tobacconist’s offices in Morocco. All along this study, we made sure to check both the conformity of the nicotine level indicated in the packaging of each product and the existence of any other components inside the product, especially toxic or unknown impurities. The method used for this study is known under the name of high-performance liquid chromatography. For statistical analysis, we used Student’s t-test for a single sample in order to analyze the relative differences between nicotine quantity reported in the product and the one measured during our experiment. Finally, we used linear regression test to determine the relationship between the nicotine level accuracy on the packaging and the level of toxic impurities in the products. The differences between the nicotine concentrations reported in the packages and the measured ones varied from −100% to +3.3%. The study showed that 31% of analyzed products have an accurate indication of the level of nicotine on the packaging. However, 47% of the studied products showed more than 20% difference between measure and packaging indication. In all analyzed samples, the level of impurities altered from 0 to 32.6%. Furthermore, the level of the nicotine breakdown products did not exceed 2% of the nicotine content in pretty much all of the samples. The actual nicotine content of electronic cigarette refill liquids is not always as precise as what is stated on the packaging; in addition to the level of impurities detected in several brands and that exceeds the European Pharmacopoeia standards, some may even present a risk of causing toxicological damage.

Simple HPLC method for rapid quantification of nicotine content in e-cigarettes liquids

“…The differences between actual and labeled nicotine content have been determined in several studies and presented as percent deviation of actual nicotine concentration from labeled concentration and are summarized in Table 4. The percentages of e-liquids in which the actual quantified nicotine concentrations that deviated by more than ±10% from the manufacturer labels were 10% [24], 18% [15], 52% [12], 56% [25], 63% [26], 65% [27], and 67% [9]. In this study, more than ±10% deviations were detected in 9 out of 11 e-liquids (82%) which are more than what stated in previous similar studies.…”

A review of nicotine‐containing electronic cigarettes—Trends in use, effects, contents, labelling accuracy and detection methods

“…There were two occasions where the label indicated that the e‐liquid contained nicotine (3 mg/ml) and when tested it did not, hence the 100% difference between labelled and measured nicotine. This could be due to no nicotine being present or the level of nicotine in the product was below the limit of detection or quantification 48 . In one case, there was a 103.3% difference between the labelled and quantified nicotine; however, this indicated that the quantified nicotine was more than double the labelled nicotine, neither of which were zero.…”

“…Therefore, it was determined that a nonparametric test was most appropriate to use here. Two previous studies that compared labelled and experimental nicotine concentrations in e‐liquids used a paired t test 46,48 . As the data in this study are not normally distributed, the nonparametric equivalent of a paired t test was used.…”

“…Several studies have shown differences in quality between brands but also alarmingly within the same brands. This means that any studies that have claimed to have found that the nicotine concentration was accurate and corresponded to the level indicated on the label may be false for an e‐liquid of the same brand belonging to a different batch 27,48 …”

“…These are tobacco minor alkaloids: nornicotine (NN), anatabine (AT), anabasine (AB) and myosmine (MS) and cause the formation of degradation products such as cotinine (CT), nicotine‐ N ′‐oxides (NO) and β‐nicotyrine (BN). These degradation compounds can also originate from inadequate handling and storage 30,48,53 …”