Diego P. Rocha

Coordenação de metais a antibióticos como uma estratégia de combate à resistência bacteriana

Antibiotic resistance has been growing at an alarming rate and consequently the arsenal of effective antibiotics against Gram-negative and Gram-positive bacteria has dropped dramatically. In this sense there is a strong need to produce new substances that not only have good spectrum of activity, but having new mechanisms of action. In this regard, this paper emphasizes the coordination of metals to antibiotics as a strategy for reversing antibiotic resistance and production of new drugs, with a special focus on quinolones, fluoroquinolones, sulfonamides and tetracyclines.

Portable electrochemical system using screen-printed electrodes for monitoring corrosion inhibitors

This work presents a portable electrochemical system for the continuous monitoring of corrosion inhibitors in a wide range of matrices including ethanol, seawater and mineral oil following simple dilution of the samples. Proof-of-concept is demonstrated for the sensing of 2,5-dimercapto-1,3,5-thiadiazole (DMCT), an important corrosion inhibitor. Disposable screen-printed graphitic electrodes (SPGEs) associated with a portable batch-injection cell are proposed for the amperometric determination of DMCT following sample dilution with electrolyte (95% v/v ethanol + 5% v/v 0.1molL-1 H2SO4 solution). This electrolyte was compatible with all samples and the organic-resistant SPGE could be used continuously for more than 200 injections (100µL injected at 193µLs-1) free from effects of adsorption of DMCT, which have a great affinity for metallic surfaces, and dissolution of the other reported SPGE inks which has hampered prior research efforts. Fast (180h-1) and precise responses (RSD < 3% n = 10) with a detection limit of 0.3µmolL-1 was obtained. The accuracy of the proposed method was attested through recovery tests (93-106%) and the reasonable agreement of results of DMCT concentrations in samples analyzed by both proposed and spectrophotometric (comparative) methods.

A flow injection procedure using Layered Double Hydroxide for on line pre-concentration of fluoride

This work showed a flow system designed with solenoid valves for preconcentration of fluoride using SPADNS method in water samples. The analyte was preconcentrated in a mini-column coated with Layered Double Hydroxides (LDH) used as adsorbent. Then, the fluoride ions were eluted with 0.5molL-1 sodium hydroxide and determined by spectrophotometry. The variables that affect the system such adsorbent mass, type of eluent, solutions flow rate, reagent concentration and pH effect were critically evaluated. Under optimized conditions, the detection limit, coefficient of variation, linear range and preconcentration factor were estimated at 15µgL-1 (99.7% confidence level), 0.8% (500µgL-1, n = 10), 50-500µgL-1 and 10, respectively. The accuracy of the method was evaluated by analysis of ALPHA APS 1076 (Simulated Rain Water) certified material, the values were not significantly different at a 95% level of confidence. The method was applied for fluoride determination in water samples and the levels found were below the maximum values established by Brazilian environmental and health legislations.

Forensics in hand: new trends in forensic devices (2013-2017)

Forensic chemistry is the application of analytical chemistry to forensic analysis and is today one of the hot topics in the scientific literature as it can provide valuable information regarding crimes that have been committed and assist in their resolution. The literature in the field of forensic chemistry has been exponentially growing and covers several different subjects. This review discusses works published between 2013 and 2017 regarding portable or potentially portable devices (such as electrochemical sensors), field tests and intelligent devices that can be used in different areas of forensic chemistry and covers the following subjects: explosives, gunshot residues (GSR), liquid fuels, illicit drugs, beverages, alternative biological fluids and agrochemicals.