Abstract
Many studies have analyzed nicotine metabolites in blood and urine to determine the toxicity caused by smoking, and assess exposure to cigarettes. Recently, hair and nails have been used as alternative samples for the evaluation of smoking, as not only do they reflect long-term exposure but they are also stable and easy to collect. Liquid-liquid or solid-phase extraction has mainly been used to detect nicotine metabolites in biological samples; however, these have disadvantages, such as the use of toxic organic solvents and complex pretreatments. In this study, a modified QuEChERS method was proposed for the first time to prepare samples for the detection of nicotine metabolite cotinine (COT) and trans-3′-hydroxycotinine (3-HCOT) in hair and nails. High-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) was used to analyze traces of nicotine metabolites. The established method was validated for selectivity, linearity, lower limit of quantitation, accuracy, precision and recovery. In comparison with conventional liquid-liquid extraction (LLE), the proposed method was more robust, and resulted in higher recoveries with favorable analytical sensitivity. Using this method, clinical samples from 26 Korean infants were successfully analyzed. This method is expected to be applicable in the routine analysis of nicotine metabolites for environmental and biological exposure monitoring.
Highlights
Direct or indirect smoking is closely related to various diseases, such as cancer and respiratory and cardiovascular diseases
For hair and nail samples, which may be contaminated by external sources, a washing step was necessary for accurate analyte measurement
Acetonitrile, methanol and water were of liquid chromatography–mass spectrometry (LC–MS) grade and purchased from Fisher Scientific (Fair Lawn, NJ, USA)
Summary
Direct or indirect smoking is closely related to various diseases, such as cancer and respiratory and cardiovascular diseases. Nicotine is a natural alkaloid contained in the tobacco plant, and a major substance linked to cigarette addiction. Nicotine absorbed into the human body through cigarette smoking can be converted into multiple metabolites [1]. 70–80% of the absorbed nicotine is transformed to cotinine (COT) by the CYP450 system (mainly CYP2A6). This primary metabolite is further converted into trans-30 -hydroxycotinine (3-HCOT) [2], and both COT and 3-HCOT. Molecules 2020, 25, 1763 are major metabolites of nicotine. The half-life of nicotine is relatively short, at approximately 3–4 h
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