Hydrocarbons present in saturated fractions of crude oils can be assessed by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as ionizing reagents in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). In this work, five paraffin standards of different average molar mass distributions (Mw) were easily ionized by APCI(+)FT-ICR MS using isooctane as the reagent gas. Data of Mw, carbon number and double bond equivalent (DBE) distributions corresponding to linear and cyclic hydrocarbons (HCs) were compared to results obtained from analysis of high temperature gas chromatography with a flame ionization detector (HTGC-FID), comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. APCI(+)FT-ICR MS data showed good agreement with those of analytical techniques. Furthermore, the ability of APCI(+) to assess n-paraffin, even in blends with polyaromatic hydrocarbon molecules such as coronene (Mw = 301 Da) at concentrations from 2.5 to 25 µg mL-1, was demonstrated. The typical MS paraffin profile (containing repeating mass units of 14 Da) was clearly confirmed, being totally suppressed when a concentration of 25 µg mL-1 of coronene was used. This phenomenon was also evidenced in one of two saturated fractions produced using saturates, aromatics and polar (SAP) compound fractionation methodology.

Corrosion processes were evaluated for AISI 316 and AISI 1020 steels by scanning electron microscopy (SEM), atomic force microscopy (AFM) and light microscopy. Coupons were immersed in four crude oil samples with different total acid numbers (TANs) for 48 days at room temperature. The steels were also exposed to three blends (B1-B3), produced by quaternary mixtures of the oils, with lower TANs than their respective original oils. SEM micrographs showed pitting-type corrosion in most cases. AFM imaging showed drastic changes in the peak-to-peak values, topographic profiles and phase images of the AISI 1020 coupons exposed to all oils and blend B3 as compared to the unexposed steel. Defects were produced on the surface of almost all the samples exposed to naphthenic corrosion. Exposure to the oil blends reduced the extent of the naphthenic corrosion on the coupons, especially blends B1 and B2. The oil mixtures (blends) reduced corrosion.

Microscopic techniques were combined to study the influence of corrosion rate on the morphologic behavior of AISI 1020 steel specimens submitted to thermal degradation of a typical acid crude oil (total acid number (TAN) = 2.1390 mg KOH g-1 and total sulfur (S) = 0.7778 wt.%). The techniques used were light microscopy (LM), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX), atomic force microscopy (AFM) as well as Raman spectroscopy. Assays were performed in six different degradation time (t = 6, 12, 24, 36, 48 and 72 h) at 320 ºC. After the exposure of the specimens to petroleum, a reduction above 37% in the TAN after t = 72 h was observed, with a maximum corrosion rate during the first periods of degradation (t = 6 and 12 h). Correlating the TAN and corrosion rate data with the microscopic data, the images of LM, AFM, and SEM/EDX showed that after 6 h of exposure to petroleum, a passivation film was formed on the surface of the steel. This film consisted of two layers, an external one, formed of FeS, and an internal one, composed of iron oxides and oxyhydroxides. However, after 48 h of thermal degradation, this morphology was altered to a single layer of FeS coating the steel surface.

Guaco Mikania glomerata Spreng. and M. laevigata Sch. Bip. ex Baker, Asteraceae, has antimicrobial activity and may be helpful in reducing the incidence of oral diseases. This double-blinded randomized clinical trial aimed to evaluate the efficacy of guaco mouthwashes on the disinfection of toothbrushes used by preschool children, tested positive for mutans streptococci (MS), as well as the quantification of its coumarin contents by high performance liquid chromatography. Ethanol extracts were obtained by percolation. The mouthwashes were prepared with 2.5% g/mL M. glomerata and M. laevigata ethanol extracts, standardized for their coumarin content (% mg/mg). Antimicrobial effect of the mouthwashes and extracts were assessed in vitro against Streptococcus mutans (ATCC 25175TM), using 2.4 to 500 µg/mL to calculate the minimum inhibitory concentration (MIC). For the in vivo study, 24 patients were randomly assigned to a 4-stage changeover system with a one-week interval between each stage. All solutions were used in all stages by a different group of children. After brushing without toothpaste, toothbrushes (n=96) were sprayed with water and solutions of M. glomerata (2.5%), M. laevigata (2.5%) and chlorhexidine (0.12%). Microbiological analysis was carried out after 4 h and 30 days, respectively. MIC values were 400, 125 and 14 µg/mL, respectively, for both crude ethanol extracts, mouthwashes of M. glomerata and M. laevigata. Statistical analysis showed that all solutions decreased contamination of toothbrushes by mutans streptococci (chlorhexidine 50.7±17.7%; M. glomerata 37.3±23.7% and M. laevigata 28.7±25.1% of inhibition). Treatment with chlorhexidine and M. glomerata were statistically similar (p>0.05). M. glomerata mouthwash could be useful in herbal strategy programs against mutans streptococci and the marker coumarin may be not related to the activity observed.