ESI(-)FT-ICR MS for the determination of best conditions for producing extract abundant in phenolic compounds from leaves of E. uniflora and FTIR-PCA as a sample screening method.

E. uniflora leaves are a rich source of phenolic compounds with biological activities, including myricitrin. In this study, the chemical profile of nine extracts prepared with leaves collected in three regions (mountain, beach, and mangrove) and at three different times of the day (8 am, 1 pm, and 6 pm) was evaluated from spectra originating from ultra-high resolution mass spectrometry (Fourier transform ion cyclotron resonance, FT-ICR) coupled to electrospray ionisation (ESI). The best time of the day and location for collecting the leaves of E. uniflora used as raw materials for producing extracts and the best ethanol concentration for obtaining an extract more abundant in compounds of interest were verified. Several flavonoids and phenolic acids were detected in their deprotonated form in the regions from m/z 200 to 1200. Myricitrin ([C21H20O12-H]-, m/ztheo 463.08820), its chloride adduct ([C21H20O12+Cl]-, m/ztheo 499.06488), other myricitrin derivatives, and some tannins were the main compounds detected. Considering obtaining an extract rich in phenolic compounds, including myricitrin, the best place and time of the day to collect E. uniflora leaves is in the beach region at 1 pm. In contrast, the best ethanol concentration for extract production is 70 wt%. Therefore, extraction at 96 wt% ethanol is better for obtaining an extract more abundant in phenolic acids, although 70 wt% ethanol also extracted these compounds. FTIR-PCA models were used to check for possible similarities in the data according to collection time of the day and location. These models demonstrated an excellent solution for sample screening.

Application of time domain nuclear magnetic resonance (TD-NMR) for study of the distillation curve of petroleum.

Crude oil distillates are a highly useful industrial product, mainly for energy generation. Unfortunately, they are rarely studied, mainly due to the low accessibility to products directly obtained from the distillation process, which is a laborious, expensive, and time-consuming operation. This work presents and discusses the use of time-domain nuclear magnetic resonance (TD-NMR) as a simple, affordable, and straightforward tool for the development of correlations supported on the transverse relaxation time (T2 ) and boiling temperature. The results point out a high convergence between TD-NMR experimental data and the ASTM D2892 method for distillates from light, medium, and heavy oils, with up to 52.20% of accumulated mass and boiling point temperature (Tb ) up to 400°C. Furthermore, an unprecedented relationship between T2 values and the accumulated mass of the distillates is first demonstrated. This new insight opens new perspectives for future prediction of accumulated mass for unknown crude oils, placing the TD-NMR relaxometry as an appeal spectroscopy approach with a potential to meaningfully contribute to the daily refining petrochemical industry field operations.

Noninvasive Diagnostic for COVID-19 from Saliva Biofluid via FTIR Spectroscopy and Multivariate Analysis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the worst global health crisis in living memory. The reverse transcription polymerase chain reaction (RT-qPCR) is considered the gold standard diagnostic method, but it exhibits limitations in the face of enormous demands. We evaluated a mid-infrared (MIR) data set of 237 saliva samples obtained from symptomatic patients (138 COVID-19 infections diagnosed via RT-qPCR). MIR spectra were evaluated via unsupervised random forest (URF) and classification models. Linear discriminant analysis (LDA) was applied following the genetic algorithm (GA-LDA), successive projection algorithm (SPA-LDA), partial least squares (PLS-DA), and a combination of dimension reduction and variable selection methods by particle swarm optimization (PSO-PLS-DA). Additionally, a consensus class was used. URF models can identify structures even in highly complex data. Individual models performed well, but the consensus class improved the validation performance to 85% accuracy, 93% sensitivity, 83% specificity, and a Matthew's correlation coefficient value of 0.69, with information at different spectral regions. Therefore, through this unsupervised and supervised framework methodology, it is possible to better highlight the spectral regions associated with positive samples, including lipid (∼1700 cm-1), protein (∼1400 cm-1), and nucleic acid (∼1200-950 cm-1) regions. This methodology presents an important tool for a fast, noninvasive diagnostic technique, reducing costs and allowing for risk reduction strategies.

Prediction of the distillation temperatures of crude oils using ¹H NMR and support vector regression with estimated confidence intervals.

This paper aims to estimate the temperature equivalent to 10% (T10%), 50% (T50%) and 90% (T90%) of distilled volume in crude oils using (1)H NMR and support vector regression (SVR). Confidence intervals for the predicted values were calculated using a boosting-type ensemble method in a procedure called ensemble support vector regression (eSVR). The estimated confidence intervals obtained by eSVR were compared with previously accepted calculations from partial least squares (PLS) models and a boosting-type ensemble applied in the PLS method (ePLS). By using the proposed boosting strategy, it was possible to identify outliers in the T10% property dataset. The eSVR procedure improved the accuracy of the distillation temperature predictions in relation to standard PLS, ePLS and SVR. For T10%, a root mean square error of prediction (RMSEP) of 11.6°C was obtained in comparison with 15.6°C for PLS, 15.1°C for ePLS and 28.4°C for SVR. The RMSEPs for T50% were 24.2°C, 23.4°C, 22.8°C and 14.4°C for PLS, ePLS, SVR and eSVR, respectively. For T90%, the values of RMSEP were 39.0°C, 39.9°C and 39.9°C for PLS, ePLS, SVR and eSVR, respectively. The confidence intervals calculated by the proposed boosting methodology presented acceptable values for the three properties analyzed; however, they were lower than those calculated by the standard methodology for PLS.

Petroleomics by electrospray ionization FT-ICR mass spectrometry coupled to partial least squares with variable selection methods: prediction of the total acid number of crude oils.

Negative-ion mode electrospray ionization, ESI(-), with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was coupled to a Partial Least Squares (PLS) regression and variable selection methods to estimate the total acid number (TAN) of Brazilian crude oil samples. Generally, ESI(-)-FT-ICR mass spectra present a power of resolution of ca. 500,000 and a mass accuracy less than 1 ppm, producing a data matrix containing over 5700 variables per sample. These variables correspond to heteroatom-containing species detected as deprotonated molecules, [M - H](-) ions, which are identified primarily as naphthenic acids, phenols and carbazole analog species. The TAN values for all samples ranged from 0.06 to 3.61 mg of KOH g(-1). To facilitate the spectral interpretation, three methods of variable selection were studied: variable importance in the projection (VIP), interval partial least squares (iPLS) and elimination of uninformative variables (UVE). The UVE method seems to be more appropriate for selecting important variables, reducing the dimension of the variables to 183 and producing a root mean square error of prediction of 0.32 mg of KOH g(-1). By reducing the size of the data, it was possible to relate the selected variables with their corresponding molecular formulas, thus identifying the main chemical species responsible for the TAN values.

LSD and 9,10-dihydro-LSD analyses in street drug blotter samples via easy ambient sonic-spray ionization mass spectrometry (EASI-MS).

Normally, the identification of the LSD drug is performed by forensic laboratories, using the Ehrlich spot test. However, this is a nonspecific analysis. Additionally, the Brazilian Federal Police has identified the presence of a new compound in seized blotters: 9,10-dihydro-LSD, an uncontrolled substance. In this work, easy ambient sonic-spray ionization mass spectrometry in the positive ion mode, EASI(+)-MS, was used to characterize LSD and 9,10-dihydro-LSD compositions directly from the surface of blotters. The presence of LSD in the seized blotter samples were also confirmed via high-performance liquid chromatography with ultraviolet detector. In a set of 41 blotters analyzed by EASI(+)-MS, 28 showed positive results for LSD, seven for 9,10-dihydro-LSD, and another six samples showed negative results for both LSD and 9,10-dihydro-LSD. The combination of thin layer chromatography with EASI-MS also demonstrated to be a relatively simple and powerful screening tool for forensic analysis of street drugs.

Studies on crude oil-water biphasic mixtures by low-field NMR.

Low-field (1) H NMR was used in this work for the analysis of mixtures involving crude oils and water. CPMG experiments were performed to determine the transverse relaxation time (T2 ) distribution curves, which were computed by the inverse Laplace transform of the echo decay data. The instrument's ability of quantifying water and petroleum in biphasic mixtures following different methodologies was tested. For mixtures between deionized water and petroleum, one achieved excellent results, with root mean squared error of cross-validation (RMSECV) of 0.8% for a regression between the water content (wt %) and the relative area of the water peak in the T2 distribution curve, or a standard deviation of 0.9% for the relationship between the water content and the relative water peak area, corrected by the relative hydrogen index of the crude. In the case of biphasic mixtures of Mn(2+) -doped water and crude oils, the best result of RMSECV = 1.6% was achieved by using the raw magnetization decay data for a partial least squares regression.

Fingerprinting of sildenafil citrate and tadalafil tablets in pharmaceutical formulations via X-ray fluorescence (XRF) spectrometry.

The production of counterfeited drugs is a criminal problem that carries serious risks to public health in the worldwide. In Brazil, Viagra and Cialis are the most counterfeit medicines, being used to inhibit the phosphodiesterase type 5 (PDE-5), treating thus, problems related to erectile dysfunction. X-ray fluorescence (XRF) is a suitable technique to control the quality of new pharmaceutical formulations and distinguish between authentic and counterfeit tablets. XRF has advantageous features like multielemental capability, good detectivity, high precision, short analysis times, and is nondestructive, which makes it suitable to be extended to a great variety of samples. In this work, the inorganic fingerprinting chemical of forty-one commercial samples (Viagra, Cialis, Lazar, Libiden, Maxfil, Plenovit, Potent 75, Rigix, V-50, Vimax and Pramil) and fifty-six counterfeit samples (Viagra and Cialis) were obtained from XRF data. XRF presented an excellent analytical methodology for semi-quantitative determination of active ingredient (in case of sildenafil citrate that presents S in its structure) and excipients such as calcium phosphate, titanium oxide and iron oxide (P, Ca, Ti and Fe). The matrix data were allied to chemometric methods (Principal Component Analysis and Hierarchical Cluster Analysis) to classify the tablets investigated between authentic and counterfeit, grouping the samples into of seven groups: A, B, C, D and E (counterfeit group) and F and G (authentic group).

Analyzing Brazilian vehicle documents for authenticity by easy ambient sonic-spray ionization mass spectrometry.

Using desorption/ionization techniques such as easy ambient sonic-spray ionization mass spectrometry (EASI-MS), it is possible to analyze documents of Brazilian vehicles for authenticity, providing a chemical profile directly from the surface of each document. A method for the detection of counterfeit documents is described, and the falsification procedure is elucidated. Forty authentic and counterfeit documents were analyzed by both positive and negative ion modes, EASI(±)-MS. EASI(+)-MS results identified the presence of (bis(2-ethylhexyl)phthalate plasticizer and of dihexadecyldimethylammonium biocide in both types of documents. For EASI(-)-MS results, the 4-octyloxybenzoic acid additive ([M + H](+): m/z 249) is present only in counterfeit documents. It was also found that counterfeit vehicle documents are produced via Laserjet printers. Desorption/ionization techniques, such as EASI-MS, offer therefore, an intelligent way to characterize the counterfeiting method.

NMR property calculations and experimental study of the 1,6-epoxycarvone and α-epoxypinene: a comparison of models.

This work aims at using theoretical calculations of shielding tensors (σ) through different methods [gauge-independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM)] and spin-spin coupling constants J using GIAO method to compare these methods and to corroborate the data obtained with the assignment of all of (1)H and (13)C NMR signals and the relative stereochemistry of the 1,6-epoxycarvone and the α-epoxypinene. All the (1)H and (13)C NMR signals were assigned unequivocally. The stereochemistry for the epoxides is trans and the B3LYP theory level with CSGT and IGAIM methods is the best choice to evaluate theoretical chemical shifts for compounds studied.

1H and 13C NMR spectral data of bioactive cage-like polycyclic compounds.

Bioactive cage-like polycyclic compounds have attracted the attention of several research groups because of their unique appearance and their biological activities. Their structures were established on the basis of (1)H NMR and (13)C NMR spectroscopic data. The (1)H and (13)C signal assignments and most homonuclear hydrogen coupling constants were assigned by use of techniques such as 1D (1)H and (13)C NMR and 2D gCOSY, non-edited gHSQC and gHMBC. The gNOESY experiments proved the endo-stereochemistry.

Stereochemistry of cyclopentane derivatives from (2,3)J(CH) dependence on dihedral angle (theta H--C--C--X).

The (2,3)J(CH) dependence on dihedral angle (theta H--C--C--X) for cyclopentane derivatives was investigated. We observed that the combined use of experimentally obtained (2,3)J(CH) values and the theoretically determined dihedral angles between the corresponding nuclei can be used to infer the relative stereochemistry of the ring substituents in cyclopentane derivatives. There is a good correlation between the magnitude of (3)J(CH) and the dihedral angle between the hydrogen and the coupled carbon (R2 = 0.88).