Mass spectrometric fragmentation and photocatalytic transformation of nicotine and cotinine

Solar light photodegradation of nicotine in the presence of aged polystyrene microplastics

Limited information exists on the potential of aged microplastics to induce photodegradation of organic pollutants under sunlight irradiation. In this work, nicotine (NIC), a widespread emerging contaminant, was used as a model organic substrate to investigate this innovative degradation process. Polystyrene (PS) pellets were artificially aged and became rich in oxygenated moieties with their carbonyl index reaching 0.43 ± 0.04 after 4 d of aging. The degradation of NIC photosensitized by aged PS at different pH values was monitored for 6 h under simulated sunlight irradiation (650 W/m2). The maximum degradation rate was observed at pH = 11 (75 % NIC removal from a 10 mg L-1 solution containing 50 g L-1 aged PS pellets), suggesting that the unprotonated NIC is the most photoreactive form. Increasing the PS load from 50 to 200 g L-1 accelerated NIC degradation. The addition of 2.5 mg L-1 humic acids had a slight enhancement role (82 % NIC degradation), which confirms their effectiveness as photosensitizers. NIC photosensitization by aged PS was also studied in the presence of t-butanol (55 % NIC removal in solutions containing 100 mg L-1 t-butanol) and in anoxic conditions (NIC solution purged with N2; 95 % NIC removal), to gain insight into the respective roles of the potentially formed •OH and 1O2. The main photo-produced reactive species involved in NIC degradation likely were the triplet states of the PS beads (3PS*). Differently from most advanced oxidation processes, NIC's photodegradation by aged PS was not affected by increasing amount of chloride and we observed negligible differences between NIC degradation in ultra-pure water and seawater. The effectiveness of irradiated PS towards NIC photodegradation was also investigated in tap water and secondary wastewater. Overall, the possibility to decontaminate polluted water with waste-derived materials is interesting in the framework of circular economy.

Chemical analysis of electronic cigarette liquids (e-liquids) and direct nicotine quantitation using surface-assisted flowing atmospheric-pressure afterglow desorption/ionization mass spectrometry (SA-FAPA-MS)

Ambient desorption/ionization mass spectrometry (ADI-MS) has been widely used for direct analysis of real samples without sample preparation or separation. Studies on the quantification of low molecular weight compounds in complex matrices with ADI-MS remain scarce. In this paper, we report the application of surface-assisted flowing atmospheric-pressure afterglow mass spectrometry (SA-FAPA-MS) for fast qualitative screening of electronic cigarette liquid (e-liquids) ingredients and direct quantification of nicotine. The quantification approach is rapid, uses a deuterated D4-nicotine standard spike, and does not require a preceding chromatography step or other methods to remove the complex sample matrix. Selected e-liquids were directly applied on thin-layer chromatography (TLC) plate surfaces (normal phase (NP) silica, reversed phase (RP) modified silica, cyano (CN) modified silica, and dimethyl (RP2) modified silica) after dilution and internal standard spiking. The plates served purely as sample carriers and no analyte separation was performed. Promising qualitative results were obtained, demonstrating the ability to detect nicotine alkaloids using this approach and the ability to differentiate e-liquids based on their flavor variations. In addition, dimethyl- (RP2-) and cyano-modified (CN-) silica surfaces were selected for quantification based on performance results of previous studies. It was shown that results were in high accordance with high-performance liquid chromatography (HPLC) experiments with lowest deviations <3% on dimethyl surfaces. Additional quantitative experiments including a certified reference material achieved equally satisfying results with lowest deviations of -1.1% from the certified nicotine content. For nicotine, detection limits down to the fmol range (96 fmol on CN and 20 fmol on RP2) were obtained. A detailed comparison of glass surfaces with functionalized surfaces showed that the functionalized surfaces were superior in terms of sample application reproducibility, mass spectra quality, sensitivity, and information density. Thus, functionalized thin-layer surfaces are considered promising tools for both qualitative and quantitative ADI-MS analysis of complex samples.

In-situ-reduced synthesis of cyano group modified g-C3N4/CaCO3 composite with highly enhanced photocatalytic activity for nicotine elimination

Graphite carbon nitride has many excellent properties as a two-dimensional semiconductor material so that it has a wide application prospect in the field of photocatalysis. However, the traditional problems such as high recombination rate of photogenerated carriers limit its application. In this work, we introduce nitrogen deficiency into g-C₃N₄ to solve this problem a simple and safe in-situ reduction method. g-C₃N₄/CaCO₃ was obtained by a simple and safe one-step calcination method with industrial-grade micron particles CaCO₃. Cyano group modification was in-situ reduced during the thermal polymerization process, which would change the internal electronic structure of g-C₃N₄. The successful combination of g-C₃N₄ and CaCO₃ and the introduction of cyanide have been proved by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer. The formation of the cyano group, an electron-absorbing group, promotes the effective separation of photogenic electron hole pairs and inhibits the recombination of photogenic carriers. These advantages result in the generation of more •O₂^- and ¹O₂ in the catalytic system, which increases the photocatalytic efficiency of nicotine degradation by ten times. Furthermore, the degradation process of nicotine has been studied in this work to provide a basis for the degradation of nicotine organic pollutants in the air.

Investigation of micropollutants in household waste fractions processed by anaerobic digestion: target analysis, suspect- and non-target screening

Household waste represents a major source of energy, nutrients, and recyclable material. In order to exploit benefits and avoid hazards in the context of circular economy, the risk profile towards human and the environment should be assessed. Here, we investigated the presence of micropollutants by quantitative target analysis, suspect and non-target screening and evaluated changes in the chemical fingerprint upon anaerobic digestion. Extracts were analyzed by reversed phase liquid chromatography high-resolution mass spectrometry (LC-HRMS) and gas chromatography mass spectrometry (GC-MS). Thirty-one of 51 target micropollutants were detected in low ng/mL levels except for few detections at µg/mL levels. The micropollutants quantified in this study included the following: pharmaceuticals (salicylic acid, amitriptyline, carbamazepine); biocides (triclocarban, 2-phenylphenol); industrial compounds used in, e.g., paper industry (pentachlorphenol, PFOS, PFOA, bisphenol A); aromatics, polycyclic aromatics, and heteroaromatics, and their alkylated, hydroxylated, or carboxylated analogues. Fifty of 206 compounds from the suspect screening list were tentatively identified. These included phthalates, methylparaben, phenol, benzophenone, and pharmaceuticals, e.g., ibuprofen. Most compounds detected by GC-MS decreased more than twofold in peak height or remained unaffected by the anaerobic digestion, and very few increased more than twofold, e.g., p-cresol, menthol, and octadecanal. From the LC-HRMS non-target screening analysis, 250 chemical components were resolved using the multiway curve resolution technique PARAFAC2; of these, carbidopa was the only identified unknown.

Development and application of high resolution mass spectrometry analytical method to study and identify the photoinduced transformation products of environmental pollutants

Terpenes are among the major causes of pleasant or unpleasant odors close to active or inactive landfills. We studied R-limonene and p-cymene environmental degradation products using the heterogeneous photocatalysis mediated by titanium dioxide to explore the odor pollution. The aim of the study was the development of mass spectrometry based methods both hyphenated with GC and HPLC to identify and characterize transformation products (TPs) derived from photodegradation of R-limonene and p-cymene. With the GC-MS method we identified three TPs for R-limonene and two for p-cymene comparing the obtained mass spectra with those in the NIST library. While with HPLC-MS method, thanks to the use of the high resolution of MS tool, we recognized four and five TPs for R-limonene and p-cymene respectively. No p-cymene was detected as R-limonene transformation product. The methods developed were then applied to real environmental samples coming from landfills active (Lan1) or inactive (Lan2 and Lan3) located in northern Italy. R-limonene was detected in the active landfill (Lan1 at the concentration of 2.35 μg/mL) together with one of its TPs and one TP derived from p-cymene. p-Cymene was detected in the other two inactive landfills (Lan2 and Lan3 concentrations 0.025 and 0.15 μg/mL, respectively) together with one of its TP and two TPs coming from R-limonene photodegradation. The finding of TPs together with R-limonene and p-cymene both in active and inactive landfills point out the attention on the reduction of these molecules in the environment to reduce pollution and human risks.

Cotinine Hydroxylase CotA Initiates Biodegradation of Wastewater Micropollutant Cotinine in Nocardioides sp. Strain JQ2195

Cotinine is a stable toxic contaminant, produced as a by-product of smoking. It is of emerging concern due to its global distribution in aquatic environments. Microorganisms have the potential to degrade cotinine; however, the genetic mechanisms of this process are unknown. Nocardioides sp. strain JQ2195 is a pure-culture strain that has been reported to degrade cotinine at micropollutant concentrations. This strain utilizes cotinine as its sole carbon and nitrogen source. In this study, a 50-kb gene cluster (designated cot), involved in cotinine degradation, was predicted based on genomic and transcriptomic analyses. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3), which initiated cotinine catabolism, was identified and characterized. CotA from Shinella sp. strain HZN7 was heterologously expressed and purified and was shown to convert cotinine into 6-hydroxycotinine. H₂¹⁸O-labeling and electrospray ionization-mass spectrometry (ESI-MS) analysis confirmed that the hydroxyl group incorporated into 6-hydroxycotinine was derived from water. This study provides new molecular insights into the microbial metabolism of heterocyclic chemical pollutants. IMPORTANCE In the human body, cotinine is the major metabolite of nicotine, and 10 to 15% of generated cotinine is excreted in urine. Cotinine is a structural analogue of nicotine and is much more stable than nicotine. Increased tobacco consumption has led to high environmental concentrations of cotinine, which may have detrimental effects on aquatic ecosystems and human health. Nocardioides sp. strain JQ2195 is a unique cotinine-degrading bacterium. However, the underlying genetic and biochemical foundations of cotinine degradation are still unknown. In this study, a 50-kb gene cluster (designated cot) was identified by genomic and transcriptomic analyses as being involved in the degradation of cotinine. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3) catalyzed cotinine to 6-hydroxy-cotinine. This study provides new molecular insights into the microbial degradation and enzymatic transformation of cotinine.

Employing in vitro metabolism to guide design of F-labelled PET probes of novel α-synuclein binding bifunctional compounds

A challenge in the development of novel ¹⁸F-labelled positron emission tomography (PET) imaging probes is identification of metabolically stable sites to incorporate the ¹⁸F radioisotope. Metabolic loss of ¹⁸F from PET probes in vivo can lead to misleading biodistribution data as displaced ¹⁸F can accumulate in various tissues.In this study we report on in vitro hepatic microsomal metabolism of novel caffeine containing bifunctional compounds (C₈-6-I, C₈-6-N, C₈-6-C₈) that can prevent in vitro aggregation of α-synuclein, which is associated with the pathophysiology of Parkinson's disease. The metabolic profile obtained guided us to synthesize stable isotope ¹⁹F-labelled analogues in which the fluorine was introduced at the metabolically stable N7 of the caffeine moiety.An in vitro hepatic microsomal metabolism study of the ¹⁹F-labelled analogues resulted in similar metabolites to the unlabelled compounds and demonstrated that the fluorine was metabolically stable, suggesting that these analogues are appropriate PET imaging probes. This straightforward in vitro strategy is valuable for avoiding costly stability failures when designing radiolabelled compounds for PET imaging.

UV-254 degradation of nicotine in natural waters and leachates produced from cigarette butts and heat-not-burn tobacco products

Nicotine is an important emerging contaminant widely detected in water resources. The main nicotine sources are human excretions from users and leaching from discarded tobacco product waste, which represents the most commonly littered item in urban areas and coasts. In this study, the UV₂₅₄ photolytical fate of nicotine in natural water and leachates produced from conventional cigarettes (CCs) and the new generation heat-not-burn (HnBs) tobacco products is examined for the first time. The effect of UV₂₅₄ irradiation on nicotine depletion in ultrapure water was initially studied. The reaction was pseudo first-order with respect to nicotine concentration at low concentrations and shifted to lower order at higher concentrations, an effect associated to absorption saturation. Although nicotine removal was fast, only 9.5% of the total organic carbon was removed after irradiation due to the formation of by-products. The chemical structures of six photo-products were derived by means of liquid and gas chromatography coupled to mass spectrometry. The photodegradation kinetics was found to depend on pH and faster kinetics were recorded when the monoprotonated form of nicotine was dominant (pH = 5-8). The presence of humic acids was found to slightly delay kinetics as they competed with nicotine for lamp irradiance, whereas the presence of salt had no effect on the direct photolysis of nicotine. Direct photolysis studies were also performed using natural waters. Compared to ultra-pure water, photodegradation was found to proceed slightly slower in river water, in similar kinetics in seawater, and relatively faster in rain water. The later was assumed to be due to the lower pH compared to the rest of the natural water tested. Leachates from used HnBs and smoked CCs were also submitted to UV₂₅₄ irradiation and direct photolysis was found to proceed fast despite the high complexity of these matrices. Nonetheless, the total organic carbon in the system remained the same after irradiation due to the abundance of organics and photo-products formed. We take advantage of the present investigations and report the leaching behavior of nicotine from HnBs and CCs. Among others, we found that in HnBs ~70% of the total and bioavailable nicotine content remains in the tobacco sticks after operation and this percentage drops to 15% in CCs due to the reduction in mass after smoking. This finding demonstrated the importance of properly disposing tobacco product waste to prevent nicotine leaching in water bodies.

Liquid chromatography/mass spectrometry analytical determination of gabapentin transformation products by heterogeneous photocatalysis and environmental evaluation

RATIONALE

Gabapentin is a drug used to treat epilepsy and peripheral neuropathic pain. It is an analog of gamma-aminobutyric acid, and it is a selective blocker of voltage-gated calcium channels. The drug is excreted unmetabolized; it is stable in the environment and is classified as a persistent mobile organic contaminant. Because wastewater treatment plants (WWTPs) are not completely efficient, some bioactive molecules may be released unaltered into the environment. The aim of this study was to provide information about degradation pathways of gabapentin in water by studying its photoinduced transformation products (TPs) through laboratory simulation experiments. Gabapentin and its TPs were monitored in influent and effluent water samples from WWTPs in Germany and Italy.

METHODS

The laboratory simulation used heterogeneous photodegradation mediated by titanium dioxide (TiO₂ ). Chromatographic separation was achieved using a C18 reverse-phase column, and the structural identification of TPs was performed using high-resolution electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and multistage MSⁿ experiments.

RESULTS

Several TPs were observed during TiO₂ photodegradation. Nine new compounds were detected, and potential structures were assigned by studying the fragmentation pathways of the [M + H]⁺ ions of these TPs and gabapentin. Gabapentin and some of the newly identified TPs were found in environmental samples from WWTPs.

CONCLUSIONS

The developed high-performance liquid chromatography/high-resolution mass spectrometry method was used to identify TPs from gabapentin. It was then successfully applied to real environmental samples to monitor the TPs as potential environmental pollutants.

Tandem mass spectrometric analysis of novel caffeine scaffold-based bifunctional compounds for Parkinson's disease

RATIONALE

Novel bifunctional compounds composed of a caffeine scaffold attached to nicotine (C₈ -6-N), 1-aminoindan (C₈ -6-I), or caffeine (C₈ -6-C₈ ) were designed as therapeutics or diagnostics for Parkinson's disease (PD). In order to probe their pharmacological and toxicological profile, an appropriate analytical method is required. The goal of this study is to establish a tandem mass spectrometric fingerprint for the development of quantitative and qualitative methods that will aid future assessment of the in vitro and in vivo absorption, distribution, metabolism, excretion (ADME) and pharmacokinetic properties of these lead bifunctional compounds for PD.

METHODS

Accurate mass measurement was performed using a hybrid quadrupole orthogonal time-of-flight mass spectrometer while multistage MS/MS and MS³ analyses were conducted using a triple quadrupole linear ion trap mass spectrometer. Both instruments are equipped with an electrospray ionization (ESI) source and were operated in the positive ion mode. The source and compound parameters were optimized for all three tested bifunctional compounds.

RESULTS

The MS/MS analysis indicates that the fragmentation of C₈ -6-N and C₈ -6-I is driven by the dissociation of the nicotine and 1-aminoindan moieties, respectively, but not caffeine. A significant observation in the MS/MS fragmentation of C₈ -6-C₈ suggests that a previously reported loss of acetaldehyde during caffeine dissociation is instead a loss of CO₂ .

CONCLUSIONS

The collision-induced tandem mass spectrometry (CID-MS/MS) analysis of these novel bifunctional compounds revealed compound-specific diagnostic product ions and neutral losses for all three tested bifunctional compounds. The established MS/MS fingerprint will be applied to the future development of qualitative and quantitative methods.