Person: Viñas López-Pelegrin, Pilar
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Fingerprinting of volatile organic compounds and discrimination of pear samples by gas chromatography-ion mobility spectrometry
The pear contains many volatile organic compounds that are responsible for its distinctive aroma, flavour and texture. The aim of this work was to develop, optimise and validate an analytical method for the determination of volatile compounds in pears using headspace gas chromatography coupled to ion mobility spectrometry. A total of 254 samples from four cultivars were analysed, and a partial least squares discriminant analysis model using 93 markers allowed differentiation between cultivars with 100 % accuracy and a Q2 of 0.878. Additionally, a total of 227 Ercoline pears collected at different stages of ripening were analysed. For the first time, a predictive model based on 75 markers was used to determine pear ripeness, achieving 100 % accuracy and a Q2 of 0.856. A total of 22 compounds were identified and quantified in the samples and key compounds were determined for each cultivar and ripening stage.
Metabolomics study of the formation of genotoxic molecules based on the fecal volatile metabolites profile using an in vivo animal model
Epidemiological studies have shown that haem iron from processed meat is a key element involved in the colon carcinogenesis. The haem iron induces lipid peroxidation in the colon lumen during digestion, enabling the formation of cytotoxic molecules derived from these reactions. The cytotoxic molecules generated are highly dependent on dietary factors such as lipid sources, calcium levels or the presence of antioxidants during digestion. Here, we investigated whether nitrite substitution by polyphenols as a food additive could modulate the in vivo luminal lipid peroxidation in the colon and consequently, reduce the formation of mucin-depleted foci in a chemical-induced colon cancer rat model. The addition of polyphenols to the cooked ham diet reduces the lipid peroxidation in the rats. A reduction in cytotoxic aldehydes in fecal water from animals fed with polyphenols as well as a decrease in the formation of mucin-depleted foci is observed. The antioxidant capacity derived from polyphenols modifies the luminal environment of the colon, allowing the identification of a specific molecular signature derived from the analysis of fecal volatile organic compounds. In this molecular signature is included the reduction in the abundance of (2E,4E)-2,4-hexadienal, a carcinogenic aldehyde derived from lipid peroxidation.
Fingerprinting of peach during the ripening process using an analytical platform with spectrometric and volatilome-based chromatographic techniques
In recent years, the quality of peaches has been related to their early harvest, so this work has focused on the characterization of the spectral fingerprint using Fourier transform near-infrared spectroscopy, and headspace gas chromatography (HS-GC) coupled to ion mobility spectrometry (IMS) and mass spectrometry (MS) based on their volatilome or volatile organic compound content, with the aim of identifying the optimum ripening point of peaches. A total of 344 samples of two different varieties at all ripening stages were analyzed. The principal component analysis (PCA) showed a clear tendency for samples at the same stage of ripening to form visible clusters. The groups identified by PCA were used to construct partial least-squares discriminant analysis models that allowed differentiation according to ripening and variety. The overall results were very promising, especially for the volatilomes measured by HS-GC−IMS and HS-GC−MS.
Evaluation of the potential use of protoporphyrins as biomarkers of anemic disease in human urine from inflammatory bowel disease patients
Protoporphyrins are organic compounds with cyclic structure that are synthesised by a wide variety of organisms. In humans, these compounds are detected in blood and urine, with significantly higher levels in blood. Their potential as biomarkers of anemia and other diseases is currently being investigated, as their levels change according to the biochemical processes associated with the disease. The most widely used biomarker of anemia is serum ferritin, but it is unreliable in patients with inflammatory bowel disease (IBD) because its levels can be altered by acute inflammation and/or infections. There is therefore a need to look for new markers to help diagnose anemia in IBD patients. This work develops and validates a method for the determination of three protoporphyrins in human urine: protoporphyrin IX (PPIX), protoporphyrin IX complex with Zn (ZnPPIX) and protoporphyrin IX complex with Fe (II) (FePPIX), the latter also known as heme. The aim is to evaluate their potential as biomarkers of anemic disease in patients diagnosed with IBD. The proposed analytical method is based on high performance liquid chromatography (HPLC) with dual detection based on photodiode array (PDA) and fluorescence (FD). Quantification of the analytes at very low concentrations is possible due to the efficient preconcentration provided by dispersive liquid-liquid microextraction (DLLME) and the sensitivity of the detection systems. The method was validated by evaluating linearity (25–1000 ng mL 1), matrix effect, sensitivity (limits of quantification were between 5 and 11 ng mL 1), selectivity, accuracy, carry-over, dilution integrity, stability and precision (< 12.1 %). Finally, statistical analyses applied to the sample quantification results showed these three markers, together with five clinical markers, were significantly different between anemic and non-anemic IBD patients.
Toward nitrite-free curing: evaluation of a new approach to distinguish real uncured meat from cured meat made with nitrite
After the International Agency for Research on Cancer (IARC) classified ingested nitrites and nitrates as “probably carcinogenic to humans” under conditions favoring endogenous nitrosation, several meat products labeled as “made without nitrite” were launched. In order to distinguish uncured products truly made without nitrite from cured products made with any nitrite source (vegetal or mineral), this article presents an approach to detect and quantify nitrite from different origins added to meat. The method consists on the determination of nitrous oxide as a target compound using headspace gas chromatography–mass spectrometry (HS-GC–MS). Nitrous oxide (N2O) is formed after two reduction steps: from nitrite to nitric oxide (NO) and then to N2O. The NO is bound to myoglobin (Mb) or metmyoglobin (Met-Mb), forming a complex, which is subsequently released using sulfuric acid, which also favors the reduction to N2O. The HS-GC–MS conditions were split ratio 1:10; injection temperature at 70 ºC; incubation temperature at 30 ºC and time 45 min; and injection volume 1 mL. As a result, a relationship was established between the concentration of nitrite in cooked ham samples and the area of the N2O peak generated, meaning that this method allows the quantification of added nitrite within a concentration range of 10 to 100 mg/kg.
Ultrasound assisted extraction approach to test the effect of elastic rubber nettings on the N-nitrosamines content of ham meat samples
Nitrosamines (NAs), which are catalogued as carcinogenic compounds, may be present in meat products due to the conversion of nitrites and as result of migration from elastic rubber nettings used. A method based on ultrasonic assisted extraction coupled with dispersive liquid–liquid microextraction as sample treatment and gas chromatography-mass spectrometry as separation and detection technique was proposed for the determination of twelve NAs in cooked ham samples. The method was validated by evaluating linearity (0.5–1000 ng g−1), matrix effect, sensitivity (detection limits were between 0.15 and 1.4 ng g−1) and precision, which was below 12%. Five NAs were found in the samples with levels ranging from not quantifiable to 40 ng g−1. The effect of the elastic rubber nettings on the nitrosamine content of meat was evaluated by comparing the levels found in products made with several plastics or thread in the presence of additives.
Bioaccumulation of mycotoxins in human forensic liver and animal liver samples using a green sample treatment
The investigation of the mycotoxin bioaccumulation in human and animals is of wide relevance due to the potential toxicity associated with these secondary metabolites. This study proposes an analytical methodology consisting of salting-out liquid–liquid extraction (SALLE) followed by dispersive liquid–liquid microextraction (DLLME) for the determination of 13 mycotoxins: aflatoxins (G1, G2, B1 and B2), enniatins (A, A1, B and B1), beauvericin, HT-2 and T-2 toxins, zearalenone and deoxynivalenol, in human and animal liver. A targeted analysis was performed by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), as well as the screening of derived metabolites by ultrahigh performance LC and high-resolution mass spectrometry (UHPLC-HRMS). The proposed method was in-home validated, and trueness was verified by apparent recovery studies with values between 94 and 110 %. Furthermore, suitable linearities were obtained by the proposed method for all the mycotoxins and detection and quantification limits allow the mycotoxin monitoring at the low levels expected in biological samples. Repeatability and intermediate precision were calculated at two concentration levels, obtaining values of relative standard deviation below 9.5 %. The proposed methodology allowed to study the bioaccumulation of mycotoxins in both human and animal liver, demonstrating the presence of emergent mycotoxins in all liver samples analyzed, specifically enniatins B, B1 and beauvericin were detected with concentrations up to 4.04 μg/kg.
Ion mobility spectrometry as an emerging tool for characterization of the volatile profile and identification of microbial growth in pomegranate juice
Headspace - gas chromatography (HS-GC) coupled to ion mobility spectrometry (IMS) is proposed as an alternative to plate counting to detect and quantify the microbial contamination in pomegranate juice. Thus, contaminated samples by the yeast Saccharomyces cerevisiae were monitored during 6 non-consecutive days over two weeks using two types of preservatives (a sorbate/benzoate mixture and a natural preservative from vegetable extracts). IMS is an emerging technique with high potential for volatile organic compounds (VOCs) monitoring because its high sensitivity and separation power of ions. The fingerprint of the samples allowed to establish difference in the volatile composition of contaminated and non-contaminated samples. Ethyl acetate, ethyl butyrate and limonene were characterized obtaining limits of detection and quantification below 0.029 and 0.097 μg/g, respectively. Furthermore, chemometric models were performed to detect contaminated pomegranate juice and to assess the concentration of yeast, obtaining a validation success of 100 and 90.91%, respectively.
Monitoring of hydroxylated polycyclic aromatic hydrocarbons in human tissues: targeted and untargeted approaches using liquid chromatography‐high resolution mass spectrometry
Hydroxylated polycyclic aromatic hydrocarbons are metabolites of persistent organic pollutants which are formed during the bioactivation process of biological matrices and whose toxicity is being studied. The aim of this work was the development of a novel analytical method for the determination of these metabolites in human tissues, known to have bioaccumulated their parent compounds. Samples were treated by salting‐out assisted liquid‐liquid extraction and the extracts were analyzed by ultra‐high performance liquid chromatography coupled to mass spectrometry with a hybrid quadrupole‐time‐of‐flight analyzer. The proposed method achieved limits of detection in the 0.15–9.0 ng/g range for the five target analytes (1‐hydroxynaphthalene, 1‐hydroxypyrene, 2‐hydroxynaphthalene, 7‐hydroxybenzo[a]pyrene, and 9‐hydroxyphenanthrene). The quantification was achieved by matrix‐matched calibration using 2,2´‐biphenol as internal standard. For all compounds, relative standard deviation, calculated for six successive analyses, was below 12.1%, demonstrating good precision for the developed method. None of the target compounds was detected in the 34 studied samples. Moreover, an untargeted approach was applied to study the presence of other metabolites in the samples, as well as their conjugated forms and related compounds. For this objective, a homemade mass spectrometry database covering 81 compounds was created and none of them was detected in the samples.
Monitorization of ibuprofen, diclofenac and triclosan and their photolytic transformation products
The presence of contaminants of emerging concern (CECs) in wastewater treatment plant (WWTP) effluents poses a significant risk to human health and the environment. The application of photolytic processes in remediation of WWTP effluents results in the formation of transformation products (TPs) with unknown environmental impact. Thus, the identification of TPs and the monitoring of their evolution during the remediation process is of great interest. This study presents a new analytical method for the determination of three CECs (ibuprofen, IBU; diclofenac, DCF; triclosan, TCS) and their respective TPs in water subjected to direct photolysis by ultraviolet A irradiation with light emitting diode lamps. The analytes were extracted using in situ ionic liquid dispersive liquid–liquid microextraction and analysed by liquid chromatography with high resolution mass spectrometry (LC-HRMS) for the identification of known and unknown TPs. The identification of TPs was conducted through two untargeted strategies: a suspect screening based on the utilization of a home-made database created from the TPs previously described, and a screening for novel TPs based on the spectral investigation of a deconvoluted and aligned list of peaks with suitable degradation trends. The proposed analytical strategy allowed up to 39 TPs being identified, with 10 of them being structurally proposed for the first time in this study. In addition, verification of the identified TPs was carried out by LC with triple quadrupole. Moreover, the three CECs and their TPs were monitored in four WWTP samples subjected to degradation trials and two TPs (DCF-TP296C and TCS-TP303C) were found.