Lc-ms/ms method development for quantitation of nicotine in toenails as a biomaker for secondhand smoke and standard lipoprotein mimetic models
Authors:   , Li Xiyang 
Published: May 2022

Passive smoke or (secondhand smoke) is defined as when a non-smoker is unintentionally exposed to a smoking environment from cigarettes, cigars, or pipes. Passive smoke can result in adverse health effects leading to heart disease, asthma attacks, lung cancer, and other major diseases. Smoke from active smokers has been extensively investigated by a number of researchers. These studies have examined methods for the analysis of nicotine and its metabolites. In contrast, the development of methods to follow nicotine and its metabolites in those exposed to passive or secondhand smoke, is lacking. Here we present a method developed for the determination of nicotine in toenails. We will describe a method that involves the pretreatment of toenails, followed by a liquid-liquid extraction. The extract is then analyzed by reverse phase high performance liquid chromatography (HPLC) ��� ion trap mass spectrometry. Some of the figures of merit for this method include quantification of the nicotine concentration levandard curve linearity (R2 > 0.99), limit of detection (LOD = 0.005 ng/mg at m/z 163), and limit of quantitation (LOQ = 0.08 ng/mg), over the concentration range of 0.08 to 20 ng/mg. Toenail samples were individually collected for research purposes, including a non-smoker never exposed to secondhand smoke, non-smoker exposed to secondhand smoke, and an active smoker. The results indicted mean of nicotine content in non-exposed, exposed, and active smoker toenails samples are 0.103, 0.415, and 1.75 ng/mg respectively. This study also compared a solid phase extraction method. As a complex of globular proteins, lipoproteins, plays an essential role in the transport and metabolism of cholesterol. The level of several metabolites in blood are controlled by several mechanisms due to its profile. Development of common assays for lipoproteins have resulted in detection of abnormalities and can help physicians assess tissue injuries and disordering in early stages. Natural lipoprotein analysis related to cardiovascular disease is challenging even when utilizing modern analytical instrumentation. In this study, we developed mimetic lipoprotein models and characterize them using UV-Vis and fluorescence spectrophotometry to gain a better understanding of lipoproteins. An independent assay, the Amplex Red Cholesterol Assay, was also performed and used to support the mimetic lipoprotein model used in this study. Cardiovascular health is associated with different classes of lipoproteins and the composition of each component in lipoproteins. This study demonstrated that the carbon-carbon double bond of cholesterol (1668 cm-1) and the peptide backbone of tyrosine resonance are enhanced in deep ultraviolet resonance Raman (dUVRR) spectra (851, 1171, 1205, 1266, 1596, and 1615 cm-1). The excitation of wavelength 197 nm characterized features of mimetic lipoprotein models. Other measurements, such as circular dichroism (CD), UV-vis, and fluorescence spectroscopy provided spectroscopic information to identity and characterize the mimetic lipoprotein models.