Linear retention index approach applied to liquid chromatography coupled to triple quadrupole mass spectrometry to determine oxygen heterocyclic compounds at trace level in finished cosmetics

Exploring Negative Chemical Ionization of Per- and Polyfluoroalkyl Substances via a Liquid Electron Ionization LC-MS Interface

Per- and polyfluoroalkyl substances (PFASs) are a class of aliphatic manufactured compounds comprising fluoro-chemicals with varied functional groups and stable carbon-fluorine bonds. They are defined as "forever chemicals" due to their persistent and bioaccumulative character. These substances have been detected in various environmental samples, including water, air, soil, and human blood, posing significant health hazards. High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) is typically employed for the analysis of PFASs. Negative chemical ionization (NCI) is generally coupled to gas chromatography (GC) and offers high selectivity and sensitivity for compounds containing electronegative atoms, such as PFASs. The liquid electron ionization (LEI) interface is an efficient mechanism developed to robustly couple a liquid flow rate from an LC system to an EI or a CI source. This interface has been successfully utilized for pesticide determination in UHPLC-LEI-CI in negative ion mode (NCI). This work aims to evaluate different parameters involved in the ionization of PFASs analyzed in LC-LEI-NCI and subsequently develop a method for their detection in real samples. The parameters considered for this study include (i) a comparison of different CI reagent gases (methane, isobutane, and argon); (ii) the use of acetonitrile as both the chromatographic solvent and CI reagent gas; (iii) the presence of water and formic acid as chromatographic mobile phase components; and (iv) the mobile phase flow rate. The optimal combination of these parameters led to promising results. Tentative fragmentation pathways of PFASs in NCI mode are proposed based on the dissociative electron capture mechanism.

Multi-class analysis of 100 drug residues in cosmetics using high-performance liquid chromatography-quadrupole time-of-flight high-resolution mass spectrometry

Cosmetics are an important aspect of the lives of many people. With an increasing demand for cosmetics, consumers pay more attention to their efficacy and composition. To improve their efficacy, prohibited substances, such as hormones, glucocorticoids, antibiotics, antifungals and antihistamines, may be added to cosmetics. We developed a rapid method for the multi-class analysis of drug residues in toner and lotion cosmetic samples using high-performance liquid chromatography coupled with quadrupole time-of-flight high-resolution mass spectrometry (HPLC-Q-TOF-HRMS). The primary variables in the extraction and purification steps were studied to minimize the interference of the sample matrix. The non-information-dependent sequential window acquisition of all theoretical fragment ion spectra (SWATH®) mode was used to improve the data acquisition efficiency. The secondary product ion peak areas were used for quantification to obtain a satisfactory matrix effects. The validation experiments confirmed that the developed method exhibited good linearity (5-200 ng/L) with correlation coefficients (R) ≥ 0.9902. Our developed method was then successfully applied to 92 real cosmetic samples. The calibration curve established by this method can be used for retrospective quantitative analysis over long durations without re-calibration. This method is efficient and suitable for screening and controlling multi-class prohibited substances in the cosmetics industry to reduce potential risks.

Facilitating structural elucidation of small environmental solutes in RPLC-HRMS by retention index prediction

Implementing effective environmental management strategies requires a comprehensive understanding of the chemical composition of environmental pollutants, particularly in complex mixtures. Utilizing innovative analytical techniques, such as high-resolution mass spectrometry and predictive retention index models, can provide valuable insights into the molecular structures of environmental contaminants. Liquid Chromatography-High-Resolution Mass Spectrometry is a powerful tool for the identification of isomeric structures in complex samples. However, there are some limitations that can prevent accurate isomeric structure identification, particularly in cases where the isomers have similar mass and fragmentation patterns. Liquid chromatographic retention, determined by the size, shape, and polarity of the analyte and its interactions with the stationary phase, contains valuable 3D structural information that is vastly underutilized. Therefore, a predictive retention index model is developed which is transferrable to LC-HRMS systems and can assist in the structural elucidation of unknowns. The approach is currently restricted to carbon, hydrogen, and oxygen-based molecules <500 g mol-1. The methodology facilitates the acceptance of accurate structural formulas and the exclusion of erroneous hypothetical structural representations by leveraging retention time estimations, thereby providing a permissible tolerance range for a given elemental composition and experimental retention time. This approach serves as a proof of concept for the development of a Quantitative Structure-Retention Relationship model using a generic gradient LC approach. The use of a widely used reversed-phase (U)HPLC column and a relatively large set of training (101) and test compounds (14) demonstrates the feasibility and potential applicability of this approach for predicting the retention behaviour of compounds in complex mixtures. By providing a standard operating procedure, this approach can be easily replicated and applied to various analytical challenges, further supporting its potential for broader implementation.

Hidden threat lurking in extensive hand hygiene during the Covid-19 pandemic: investigation of sensitizing molecules in gel products by hyphenated chromatography techniques

During the Covid-19 pandemic, health agencies worldwide have recommended frequent handwashing and sanitizing. A variety of hand gel products were made available on the market, often with fragrances added to curtail the strong smell of alcohol. Commonly used Citrus fragrances contain volatile aroma constituents and non-volatile oxygen heterocyclic compounds (OHCs), consisting mostly of polymethoxyflavones, coumarins, and furocoumarins. The latter have long been investigated for their phototoxic properties, and their safety as cosmetic product ingredients has been debated recurrently. To this concern, twelve commercial Citrus-scented products were investigated in this study. An extraction method was optimized for thirty-seven OHC compounds, obtaining absolute mean recovery values in the 73.5-116% range with only few milliliters of solvent consumption. Analysis by ultra-high-pressure liquid chromatography with tandem mass spectrometry detection evidenced that three samples did not conform to the labeling requirements for fragrance allergens (coumarin) laid down by the European Union Regulation on Cosmetic Products. The total furocoumarin (FC) content of the samples investigated was in the 0.003-3.7ppm range, with some noteworthy exceptions. Specifically, in two samples, the total FCs were quantified as 89 and 219 ppm, thus exceeding the safe limits recommended up to a factor of 15. Finally, the consistency of the volatile fingerprint attained by gas chromatography allowed drawing conclusions on the authenticity of the Citrus fragrances labeled, and several products did not conform to the information reported on the label concerning the presence of essential oils. Besides the issue of product authenticity, analytical tools and regulatory actions for widespread testing of hand hygiene products are urgent, to protect consumers' health and safety.

Analysis of Prohibited and Restricted Ingredients in Cosmetics

The general public uses cosmetics daily. Cosmetic products contain substances (ingredients) with various functions, from skincare to enhancing appearance, as well as ingredients that preserve the cosmetic products. Some cosmetic ingredients are prohibited or restricted in certain geographical regions, such as the European Union and the United States of America, due to their potential to cause adverse effects such as cancer, birth defects, and/or developmental and reproductive disorders. However, the ingredients may be used in other regions, and, hence, the monitoring of the cosmetic ingredients actually used is important to ensure the safety of cosmetic products. This review provides an overview of recent analytical methods that have been developed for detecting certain ingredients that are restricted or prohibited by the U.S. Food and Drug Administration (FDA) and/or EU legislation on cosmetic products.

Characterization and determination of Benvitimod, an unknown risk substance in cosmetics, using nuclear magnetic resonance spectroscopy and HPLC-MS/MS

Ultra-high performance liquid chromatography-tandem high-resolution mass spectrometry, combined with preparative chromatography and nuclear magnetic resonance spectroscopy, a new method for identifying unknown risk substances structure in cosmetics has been established. Moreover, HPLC-MS/MS was developed for the determination of benvitimod in cosmetics. The sample was collected in Ultra-high performance liquid chromatography-tandem high-resolution mass spectrometry, the molecular formula of the unknown was obtained as C₁₇ H₁₈ O₂ . After preparative chromatography enrichment and purification, the enriched compound was scanned by nuclear magnetic resonance spectroscopy, and the chemical structure of the unknown was confirmed as benvitimod. Subsequently, the separation was determined in multiple reaction monitoring mode. The results showed that the linearity of benvitimod was good in the range of 1∼100 μg/L with the correlation coefficient r² >0.999; the limit of detection and quantification were 0.02 mg/kg and 0.067 mg/kg; the precision and stability were good; the average recoveries were 104.2%, 108.2% and 108.7% for low, medium and high spiked concentrations. Forty batches of cosmetics were screened, of which two batches were detected with illegal addition of benvitimod at 2.48 g/kg and 3.13 g/kg. The method effectively solved the loopholes in regulation and provided a research basis for the qualitative identification of structurally unknown compounds in cosmetics. This article is protected by copyright. All rights reserved.

Supercritical fluid chromatography-tandem mass spectrometry of oxygen heterocyclic compounds in Citrus essential oils

Oxygen heterocyclic compounds are secondary metabolites mainly present in the non-volatile fraction of cold-pressed Citrus essential oils. Under this denomination are included coumarins, furocoumarins, and polymethoxyflavones. These compounds possess numerous beneficial properties for human health, but the ingestion of large amounts of coumarins is often related to toxic effects, whereas the phototoxicity caused by furocoumarins and UVA exposure has been well known for a long time. This research has been aimed at the validation of an analytical approach, based on supercritical fluid chromatography coupled to tandem mass spectrometry, for the analysis of OHCs in Citrus essential oils. Among eight columns tested, packed with different stationary phases, the pentafluorophenyl allowed the best baseline separation in 8 min and by using less than 10% of methanol. Calibration curves of twenty-eight standards (coumarins, furocoumarins, polymethoxyflavones) were constructed on spiked lemon distilled essential oil and the method was validated according to the EURACHEM guidelines, by calculating linearity, limit of detection (LoD), limit of quantification (LoQ), accuracy, intra-day, and inter-day precision. Specifically, recoveries were in the 80.0-118.6% range, regression coefficients were between 0.9904 and 0.9998, the LoDs were in the 0.0004-0.0470 mg kg^-1 range, the LoQs were in the 0.0014-0.1536 mg kg^-1 range, and coefficients of variation were between 0.3 and 2.6% (intra-day) and 1.1 and 7.4% (inter-day). The quantitative profiles of thirteen cold-pressed Citrus essential oils were determined.

The online coupling of liquid chromatography to Fourier transform infrared spectroscopy using a solute-deposition interface: A proof of concept

Hyphenated techniques combining chromatographic and spectroscopic methods are the gold standard to effectively handle the emerging challenges in the analysis of unknown chemical components in mixtures, and in this regard the coupling of liquid chromatography to Fourier transform infrared spectroscopy (LC-FTIR) is no exception. While earlier attempts to couple LC to IR spectroscopy relied almost entirely on offline techniques, clear motivations for implementing online LC-FTIR instrumentation emerged from the need for shorter analysis time, a higher degree of automation and sample throughput, better reproducibility, and reduced contamination. Most recent designs of LC-FTIR concepts have aimed to combine the advantages of both approaches by means of a solvent-elimination interface. The hyphenated instrumentation and method presented in this research are based on a pneumatically assisted LC-FTIR interface, relying on a small-scale self-regulating spray dryer to attain desolvation of the LC eluent stream while retaining the spatial and temporal resolution of the dissolved substrates. Focused deposition of the dried analytes occurs onto a ZnSe disc for continuous transmission mid-IR analysis at a resolution of 4 cm^-1. The optimization of the LC-FTIR technique is discussed in terms of interface parameters, limits of detection, and limits of quantification for a pair of furanocoumarin isomers differing in the position (linear or angular type) of the furan ring fused to coumarin. Finally, confident discrimination between the two closely related molecules was attained by matching the experimental FTIR spectra in a dedicated library. The quality match factors obtained were higher than 99% for both molecules. The limit of identification (LOI) was determined experimentally as the minimum amount of substance yielding a library-searchable IR spectrum (affording a quality match factor higher than 90%). Specifically, LOI of 0.6 μg and 1.25 μg was determined for psoralen and angelicin, respectively.

Dietary Intake of Coumarins and Furocoumarins through Citrus Beverages: A Detailed Estimation by a HPLC-MS/MS Method Combined with the Linear Retention Index System

Official regulations concerning the maximum number of substances in food are introduced as a consequence of possible adverse effects, after oral administration. In this regard, analytical methods are necessary in order to determine specific targets. Among oxygen heterocyclic compounds (OHCs, that are furocoumarins, coumarins and polymethoxyflavones), only coumarin is subject to restriction by the Regulation (EC) No 1334/2008 of the European Parliament. Furocoumarins are known for their phototoxicity and other side effects due to their dietary intake; however, an official limit about the maximum content of these compounds in food is still missing. The lack of information about the real amount of these compounds in food is responsible for the conflicting opinions about the introduction of an official limit. The HPLC-MS/MS method here proposed, in combination with the linear retention index system, represents an innovative analytical strategy for the characterization of OHCs in citrus beverages. Several types of drinks were analysed in order to quantify 35 OHCs in total. This method is suitable for the quality control of OHCs in food and the obtained results may be considered as informative data useful for the regulatory authorities in the emission of new opinions and for a potential new regulation in this field.