Development of methods based on low-temperature partitioning (LTP) for monitoring cresols and chlorophenols in sewage sludge, soil, and water in column leaching.

Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system.

Determination of p-cresol levels in smoked meat products using QuEChERS method and gas chromatography-mass spectrometry.

p-Cresol is known as an environmental chemical contaminant that has toxic effects on humans. However, the presence of p-cresol in smoked foods has been seen as a flavor constituent. The present study had as objective to optimize and validate the QuEChERS method for the determination of p-cresol in beef hamburger, which was chosen as a representative matrix for six smoked meat products. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The method showed limit of quantification (LOQ) of 40 µg kg-1, linearity between 40 and 200 µg kg-1, recovery higher than 70% and relative standard deviation lower than 14%. The proposed method was applied to six different smoked foods and the p-cresol concentration ranged from 148 to 872 µg kg-1 and only the turkey breast pate showed a concentration lower than the LOQ. The descending order of p-cresol level in smoked samples was: sausage > shredded tuna > salami > turkey breast > hamburger > turkey breast pate. In three analyzed samples, the results showed that the p-cresol migrates from the surface to the food inner. Finally, the proposed method was simple and efficient to quantify high levels of this contaminant in smoked foods and it could be a useful tool for the monitoring food safety and quality.

Voltammetric Determination of Isopropylmethylphenols in Herbal Spices.

Thymol and carvacrol-the components of herbal spices-are known for their broad biological activity as antimicrobials and antioxidants. For this reason, it is important to develop new methods for their determination in plant material. A simple, rapid, and sensitive method for determination of total content of these analytes in herbal spices using differential pulse voltammetry (DPV) has been developed. The basis of the research is the oxidation process of isopropylmethylphenols on a platinum microelectrode in glacial acetic acid containing acetonitrile (20%, v/v) and 0.1 mol L-1 sodium perchlorate as the supporting electrolyte. Linear voltammetric responses for thymol and carvacrol were obtained in a wide concentration range from 0.39-1105 and 0.47-640 µg mL-1, with a low detection limit of 0.04 and 0.05 µg mL-1, respectively. The analysis was performed using the multiple standard addition method. The results of the voltammetric determination are in good agreement with the data of the standard chromatographic method. To the best of our knowledge, this is the first presentation of an electrochemical procedure to determine these compounds in these environmental and electrode materials.

Evaluation of Salivary Indoxyl Sulfate with Proteinuria for Predicting Graft Deterioration in Kidney Transplant Recipients.

Acute kidney injury (AKI) is a significant risk factor for developing chronic kidney disease and progression to end-stage renal disease in elderly patients. AKI is also a relatively common complication after kidney transplantation (KTx) associated with graft failure. Since the lifespan of a transplanted kidney is limited, the risk of the loss/deterioration of graft function (DoGF) should be estimated to apply the preventive treatment. The collection of saliva and urine is more convenient than collecting blood and can be performed at home. The study aimed to verify whether non-invasive biomarkers, determined in saliva and urine, may be useful in the prediction of DoGF in kidney transplant recipients (KTRs) (n = 92). Salivary and serum toxins (p-cresol sulfate, pCS; indoxyl sulfate, IS) concentrations were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Urinary proteins, hemoglobin, and glucose were measured using a semi-quantitative strip test. Salivary IS (odds ratio (OR) = 1.19), and proteinuria (OR = 3.69) were demonstrated as independent factors for the prediction of DoGF. Satisfactory discriminatory power (area under the receiver operating characteristic curve (AUC) = 0.71 ± 0.07) and calibration of the model were obtained. The model showed that categories of the increasing probability of the risk of DoGF are associated with the decreased risk of graft survival. The non-invasive diagnostic biomarkers are a useful screening tool to identify high-risk patients for DoGF.

Untargeted metabolomics and transcriptomics identified glutathione metabolism disturbance and PCS and TMAO as potential biomarkers for ER stress in lung.

Endoplasmic reticulum (ER) stress is a cellular state that results from the overload of unfolded/misfolded protein in the ER that, if not resolved properly, can lead to cell death. Both acute lung infections and chronic lung diseases have been found related to ER stress. Yet no study has been presented integrating metabolomic and transcriptomic data from total lung in interpreting the pathogenic state of ER stress. Total mouse lungs were used to perform LC-MS and RNA sequencing in relevance to ER stress. Untargeted metabolomics revealed 16 metabolites of aberrant levels with statistical significance while transcriptomics revealed 1593 genes abnormally expressed. Enrichment results demonstrated the injury ER stress inflicted upon lung through the alteration of multiple critical pathways involving energy expenditure, signal transduction, and redox homeostasis. Ultimately, we have presented p-cresol sulfate (PCS) and trimethylamine N-oxide (TMAO) as two potential ER stress biomarkers. Glutathione metabolism stood out in both omics as a notably altered pathway that believed to take important roles in maintaining the redox homeostasis in the cells critical for the development and relief of ER stress, in consistence with the existing reports.

p-Cresol in cheese: Is it a flavouring compound or chemical contaminant?

p-Cresol has been identified as a flavouring compound in cheeses; however, scientific studies have already identified p-cresol as a potential chemical contaminant in environmental matrices. Thus, the objective of this study was to evaluate four traditional methods for extracting p-cresol from cheese samples in order to validate the best method, and finally to apply it to five cheese samples with different origins, processing and ripeness times. The analyses were performed by gas chromatography-mass spectrometry after derivatisation of p-cresol with anhydride acetic and pyridine. Better results were achieved by the QuEChERS method, which showed recovery higher than 80%, relative standard deviation lower than 16%, limit of quantification of 5 µg kg-1 and linearity between 5 and 400 µg kg-1 with R2 0.99. p-Cresol was quantified in almost all of the samples analysed at different concentration levels, which were in an increasing order at µg kg-1: Cheddar (< LOQ), Parmesan (8 ± 0.7), Gorgonzola (103 ± 14), smoked Provolone (365 ± 28) and barbecue cheese (1001 ± 187). Although no maximum residue limit has been established for p-cresol in food, the results suggest that cheeses exposed to charcoal combustion notably increase the p-cresol levels and may represent a hazard to human health, especially in risk groups such as patients with chronic kidney disease who have serious problems with p-cresol.

Consumption of an Oil Palm Fruit Extract Promotes Large Bowel Health in Rats.

Oil palm fruit is widely used for edible oils, but the health benefits of other components are relatively unknown. We examined if consuming a polyphenol-rich extract of the fruit, from a vegetation by-product of oil processing, which also contains fibre, has gastro-intestinal benefits in rats on a Western-type diet (WD). The oil palm preparation (OPP) was added to food (OPP-F) or drinking water (OPP-D) to provide 50 mg of gallic acid equivalents (GAE)/d and compared to effects of high amylose maize starch (HAMS; 30%) in the diet or green tea extract (GT; 50 mg GAE/d) in drinking water over 4 wk. OPP treatments induced some significant effects (P < 0.05) compared to WD. OPP-D increased caecal digesta mass, caecal digesta concentrations of total SCFA, acetate and propionate (OPP-F increased caecal butyrate concentration), the numbers of mucus-producing goblet cells per colonic crypt, and caecal digesta abundance of some bacteria which may provide benefit to the host (Faecalibacterium prausnitzii, Akkermansia muciniphila and Ruminococcus gnavus). HAMS induced similar effects but with greater potency and had a broader impact on microbe populations, whereas GT had minimal impacts. These results suggest dietary OPP may benefit the large bowel.

Rat volatiles as an attractant source for the Asian tiger mosquito, Aedes albopictus.

Aedes albopictus is a vector of dengue, chikungunya, and dirofilariasis. Volatile compounds are crucial for mosquitoes to locate their hosts. This knowledge has allowed the identification of attractants derived from human odours for highly anthropophilic mosquito species. In this study, we used rats as a experimental model to identify potential attractants for host-seeking Ae. albopictus females. Porapak Q extracts from immature female rats were more attractive to Ae. albopictus females than those from mature and pregnant females, and males. Phenol, 4-methylphenol, 4-ethylphenol, and indole were identified compounds in male, immature, mature, and pregnant female extracts. There were quantitative differences in these compounds among the extracts that likely explain the discrepancy in their attractiveness. Ae. albopictus females were not attracted to the single compounds when was compared with the four-component blend. However, the binary blend of 4-methylphenol + 4-ethylphenol and the tertiary blend of 4-methylphenol + 4-ethylphenol + indole were as attractive as the four-component blend. In the field trials, BGS traps baited with the tertiary or quaternary blends caught more Ae. albopictus females and males than BGS traps without lures. This is the first laboratory and field study to identify compounds that mediate the attraction of Ae. albopictus to one of its hosts.

Applying mass spectrometry-based assays to explore gut microbial metabolism and associations with disease.

The workings of the gut microbiome have gained increasing interest in recent years through the mounting evidence that the microbiota plays an influential role in human health and disease. A principal focus of this research seeks to further understand the production of metabolic by-products produced by bacteria resident in the gut, and the subsequent interaction of these metabolites on host physiology and pathophysiology of disease. Gut bacterial metabolites of interest are predominately formed via metabolic breakdown of dietary compounds including choline and ʟ-carnitine (trimethylamine N-oxide), amino acids (phenol- and indole-containing uremic toxins) and non-digestible dietary fibers (short-chain fatty acids). Investigations have been accelerated through the application of mass spectrometry (MS)-based assays to quantitatively assess the concentration of these metabolites in laboratory- and animal-based experiments, as well as for direct circulating measurements in clinical research populations. This review seeks to explore the impact of these metabolites on disease, as well as to introduce the application of MS for those less accustomed to its use as a clinical tool, highlighting pertinent research related to its use for measurements of gut bacteria-mediated metabolites to further understand their associations with disease.

A promising "metastable" liquid crystal stationary phase for gas chromatography.

The liquid crystal state is an ordered physical state between a solid and a liquid. Previous research, in gas chromatography, proved that it provides a geometric selectivity, which allows the separation of geometric position isomers and cis-trans isomers that are difficult to separate on conventional gas chromatography stationary phases (polydimethyl siloxane derived and polyethylene glycol stationary phases). However, their use was generally very limited by the rather high temperature at which they must be operated, normally above the solid-liquid crystal transition temperature. In the present study we are interested in a new synthesized material, 1,4- bis (4-bromohexyloxy benzoate) phenyl (BHOBP). The first characterizations of BHOBP were carried out by thermogravimetric analysis, hot-stage optical microscopy and differential scanning calorimetry to control the thermal stability of the BHOBP as well as the nematic texture of the mesophase highlighted in a well-defined temperature range (120 °C-200 °C). When heated, the solid compound led to a stable liquid crystal state. Its cooling has revealed "a new metastable physical state, which is the supercooled liquid crystal phase". After these first characterizations, the new material was used as a stationary phase for gas chromatography. The BHOBP was deposited in a capillary column by the dynamic method. The inverse gas chromatography study of the column revealed a solid-stable nematic phase transition temperature, in agreement with the first characterization methods. The stable liquid crystal phase showed good resolutions in the analysis of some geometric isomers of low volatility as PAHs. The presence of the supercooled liquid crystal state in the chromatographic column has also been confirmed. This new metastable state is particularly interesting because it enlarged the scope of this material by improving the resolution of several mixtures. Thus, the separation of highly volatile mixtures of geometric isomers (e.g. cis and trans-decalin) was achieved only through this metastable mesophase confirming its unique selectivity. The metastable liquid crystal, used at 80 °C, has also exhibited an original behavior by its stability after several weeks of use at the same temperature, maintaining constant retention factors and selectivity.

Establishment of adsorption isotherms of m- and p-cresols in chromatographic process with aluminum terephthalate metal-organic framework as stationary phase.

Close boiling points pose great challenges to the separation of the isomers m-cresol and p-cresol. Metal-organic frameworks (MOFs) material with uniform pore structure, high specific surface area and good chemical stability is a potential adsorbent. In this study, m-cresol and p-cresol were separated by a chromatographic process with aluminum terephthalate metal-organic framework (MIL-53(Al)) as stationary phase and acetonitrile as mobile phase. In view of the unique "breathing" effect of MOFs materials, according to the kinetic process and thermodynamic equilibrium of adsorption and desorption, the hybrid adsorption isotherm equations were established, which can reflect the "breathing" effect by combining the Langmuir adsorption process of narrow pore and the multi-stage adsorption process of large pore. The parameters of adsorption isotherm were determined by inverse method and genetic algorithm, and the adaptability of the equilibrium dispersive chromatography model based on this adsorption isotherm to the single-component adsorption process and two-component competitive adsorption process was proved under different injection concentration, injection time and flow velocity conditions. The separation process of m-cresol and p-cresol was optimized by the chromatographic model and genetic algorithm. Under the optimized conditions, the separated m-cresol and p-cresol were obtained with the purity values of 96.26% and 93.23%, and the recovery values of 96.93% and 96.59%, respectively.

Determination of three cresol isomers in sewage sludge by solid-liquid extraction with low temperature purification and gas chromatography-mass spectrometry.

Cresols are chemical contaminants derivative from phenol which can be found in sewage sludge. However, little attention has been given to monitoring these compounds in environmental matrices in the literature. Thus, the objective of this study was to develop a simple method based on solid-liquid extraction with low temperature purification for determining three cresol isomers in sludge. The quantification of these compounds was performed by gas chromatography coupled to mass spectrometry with a previous derivatization step. After a detailed study, the cresol recovery was higher than 91%, with relative standard deviation lower than 12% and a limit of quantification of 20 µg kg-1. Linearity was achieved between 10 and 90 µg L-1 (R2 > 0.98) with the standard solutions prepared in matrix extracts due to the trouble caused by the matrix effect. The proposed method was applied with success for monitoring cresols in sewage sludge samples coming from six different wastewater treatment plants. All samples showed contamination by cresols, mainly p-cresol with values between 32.3 and 516.9 µg kg-1. The majority of the analyzed samples showed a total sum of the isomers higher than the maximum residue limit established by Brazilian legislation (160 µg kg-1).

Serum P-Cresyl Sulfate Is a Predictor of Central Arterial Stiffness in Patients on Maintenance Hemodialysis.

Arterial stiffness (AS) has an important impact on the outcomes of patients on hemodialysis (HD), and p-cresyl sulfate (PC) can mediate the process of vascular damage. We aimed to investigate the relationship between carotid-femoral pulse wave velocity (cfPWV) and the level of PCs in HD patients. Serum PCs were quantified using liquid chromatography mass spectrometry. Patients who were on standard HD for more than 3 months were enrolled and categorized according to the cfPWV into the high AS (>10 m/s) and control (≤10 m/s) groups. Forty-nine (41.5%) patients belonged to the high AS group and had a higher incidence of diabetes mellitus (DM) and increased systolic blood pressure, serum C-reactive protein, and PC levels but had lower creatinine, compared with those in the control group. In HD patients, the risk for developing high AS increased in the presence of DM (OR 4.147, 95% confidence interval (CI) 1.497-11.491) and high PCs (OR 1.067, 95% CI 1.002-1.136). Having DM (r = 0.446) and high PC level (r = 0.174) were positively associated with cfPWV. The most optimal cutoff value of PC for predicting AS was 18.99 mg/L (area under the curve 0.661, 95% CI 0.568-0.746). We concluded that DM and PCs were promising predictors of high AS in patients on maintenance HD.

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The intensity of male-male competition may affect chemical scent constituents in the dark ventral patch of male Iberian red deer.

During the mating season, Iberian red deer males (Cervus elaphus hispanicus) present a large visible dark ventral area in their abdomen. This characteristic dark-haired area is formed by the impregnation of the hair with sprayed urine and gland secretions and contains volatile compounds that can be used in intraspecific communication. Here, we used gas chromatography-mass spectrometry (GC-MS) to describe the lipophilic chemicals from the dark ventral patch of males from different populations with different levels of intrasexual competition. Amongst all the compounds found, m-cresol, benzoic acid, cholesterol and 4-hydroxy-benzenopropanoic acid were the most abundant. The proportions of these compounds varied with age as well as with the level of intra-sexual competition, independently of age. In particular, red deer males experiencing higher intra-sexual competition had lower proportions of aromatic compounds (especially m-cresol) but higher proportions of carboxylic acids on their dark bellies. Males in a high male-male competition situation, invest in volatile compounds that can reveal their age, dominance status and condition, and that, in addition, enhance this signal. On the contrary, males from low intra-sexual competition populations have chemical profiles more characteristic of young individuals. This research shows a first glance of how secretion of volatile compounds of male deer can be modulated due to the intensity of male-male competition in the population.

A comparative study of the volatile profile of wine vinegars with protected designation of origin by headspace stir bar sorptive extraction.

The characteristic volatile profile of the Spanish Vinagre de Jerez (VJ), Vinagre de Condado de Huelva (VC) and Vinagre de Montilla-Moriles (VMM) protected designation of origin (PDO) wine vinegars has been studied and compared for the first time by headspace stir bar sorptive extraction-gas chromatography-mass spectrometry (HSSE-GC-MS). The possible markers of each category and PDO were assessed. Acetates were the majority group in all vinegars, while ketones, C13-norisoprenoids and volatile phenols showed significant differences between the three PDOs. Analysis of variance (ANOVA), heatmap and partial least squares-discriminant analysis (PLS-DA) were performed. According to these results, 1-heptanol, methyl nonanoate, 2-methylbutanoic acid, 2,2,6-trimethyl-cyclohexanone, trans-2-decenal, eucalyptol and α-terpineol, were the most significant compounds for differentiating of VC, diacetyl and acetoin, ethyl 3-ethoxypropanoate, 2- and 3-heptanone, 2-methyl-1-hexadecanol, 1-octen-3-ol, p-Cresol and camphene for VMM; and ß-damascenone, 5-hydroxymethylfurfural, 3-heptanol, trans-2-hexen-1-ol and trans-2-hexen-1-yl acetate for VJ. Classification results showed that 100% of PDO samples were correctly classified, reaffirming the utility of the volatile profiles for classifying and authenticating wine vinegar PDOs.

Decoding microbial community intelligence through metagenomics for efficient wastewater treatment.

Activated sludge, a microbial ecosystem at industrial wastewater treatment plants, is an active collection of diverse gene pool that creates the intelligence required for coexistence at the cost of pollutants. This study has analyzed one such ecosystem from a site treating wastewater pooled from over 200 different industries. The metagenomics approach used could predict the degradative pathways of more than 30 dominating molecules commonly found in wastewater. Results were extended to design a bioremediation strategy using 4-methylphenol, 2-chlorobenzoate, and 4-chlorobenzoate as target compounds. Catabolic potential required to degrade four aromatic families, namely benzoate family, PAH family, phenol family, and PCB family, was mapped. Results demonstrated a network of diverse genera, where a few phylotypes were seen to contain diverse catabolic capacities and were seen to be present in multiple networks. The study highlights the importance of looking more closely at the microbial community of activated sludge to harness its latent potential. Conventionally treated as a black box, the activated biomass does not perform at its full potential. Metagenomics allows a clearer insight into the complex pathways operating at the site and the detailed documentation of genes allows the activated biomass to be used as a bioresource.

Identification of small molecule flavor compounds that contribute to the somatosensory attributes of bovine milk products.

Compounds that contribute to the somatosensory flavor profile of bovine fluid milk products were investigated. Sensory descriptive analysis defined five main attributes that consisted of "mouthcoating, astringent/drying, fatty texture, dairy mouthfeel, and tingling/irritation" sensations. Utilizing multi-dimensional LC sensory guided fractionation, compounds with these attributes were selected, purified and subsequently identified by LC/MS as orotic acid, pantothenic acid, hippuric acid, and p-cresol sulfate. Quantitative analysis of the four compounds across skim milk, low fat milk and whole milk indicated the concentrations were not significantly different; however, they were significantly lower in cream. Sensory recombination milk model analysis of each compound at endogenous concentrations of fluid milk indicated all compounds were sensory active. Furthermore, using a 2-AFC sensory test, skim milk spiked at two-fold higher concentrations of the 4 compounds had a significantly "creamier, fuller body" when compared with skim milk itself (α = 0.01).

Identification of 3-(trifluoromethyl)phenol as the malodorous compound in a pollution incident in the water supply in Catalonia (N.E. Spain).

A study of organic compounds that caused a serious taste and odor episode of water supply in two residential areas in Catalonia (N.E. Spain) was carried out. Sweet and paint/solvent odor were the main descriptors used by consumers. Some cases of sickness and nausea were also associated with drinking water consumption by the consumers. Closed-loop stripping analysis (CLSA) combined with sensory gas chromatography and gas chromatography mass spectrometry detection were used to study the problem. As a result, 3-(trifluoromethyl)phenol (CAS number 98-17-9) was for the first time identified as a responsible of an odor incident in drinking water. Concentration levels of this compound were up to 17,000 ng/L in groundwater and up to 600 ng/L in distributed water. Odor threshold in water for 3-(trifluoromethyl)phenol was determined as 13 ng/L (45 °C).

Development and validation of a sensitive liquid-chromatography tandem mass spectrometry assay for mycophenolic acid and metabolites in HepaRG cell culture: Characterization of metabolism interactions between p-cresol and mycophenolic acid.

Mycophenolic acid (MPA), a frequently used immunosuppressant, exhibits large inter-patient pharmacokinetic variability. This study (a) developed and validated a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for MPA and metabolites [MPA glucuronide (MPAG) and acyl-glucuronide (AcMPAG)] in the culture medium of HepaRG cells; and (b) characterized the metabolism interaction between MPA and p-cresol (a common uremic toxin) in this in vitro model as a potential mechanism of pharmacokinetic variability. Chromatographic separation was achieved with a C18 column (4.6 × 250 mm,5 µm) using a gradient elution with water and methanol (with 0.1% formic acid and 2 mm ammonium acetate). A dual ion source ionization mode with positive multiple reaction monitoring was utilized. Multiple reaction monitoring mass transitions (m/z) were: MPA (320.95 → 207.05), MPAG (514.10 → 303.20) and AcMPAG (514.10 → 207.05). MPA-d3 (323.95 → 210.15) and MPAG-d3 (517.00 → 306.10) were utilized as internal standards. The calibration curves were linear from 0.00467 to 3.2 µg/mL for MPA/MPAG and from 0.00467 to 0.1 µg/mL for AcMPAG. The assay was validated based on industry standards. p-Cresol inhibited MPA glucuronidation (IC50 ≈ 55 µm) and increased MPA concentration (up to >2-fold) at physiologically relevant substrate-inhibitor concentrations (n = 3). Our findings suggested that fluctuations in p-cresol concentrations might be in part responsible for the large pharmacokinetic variability observed for MPA in the clinic.