RESUMO

Documents with handwritten portions are often susceptible to adulteration, forgery, and addition of entries, raising a problem of social concern. In this study, DESI ionization with imaging capabilities is applied to identify fraud in handwritten documents made using erasable pens of the chemical method of erasing (other than the usual physical methods). A fraud procedure was simulated in which an original entry made in white office paper was erased and replaced with a new one. The areas were directly analyzed using a DESI-MSI ion source coupled to a Q-Extractive mass spectrometer. Chemical images were obtained mapping the intensity of selected ions, spelling out each part of the fraud process as irrefutable evidence of its occurrence. Thus, the potential application of DESI-MSI in detecting fraud in suspect documents is demonstrated as a useful, simple, and fast alternative for the traditional techniques employed in these situations.

RESUMO

On-surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe2+ /H2 O2 ) and Fenton-like (Mn+ /H2 O2 ; Mn+  = Fe3+ , Co2+ , Cu2+ , Mn2+ ) systems was investigated by using paper spray ionization mass spectrometry (PS-MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS-MS analyzes). The results indicated the following order in the rates of such reactions: Fe2+ /H2 O2  â‰« H2 O2  â‰« Cu2+ /H2 O2  > Mn+ /H2 O2 (Mn+  = Fe3+ , Co2+ , Mn2+ ) ~ Mn+ (Mn+  = Fe2+ , Fe3+ , Co2+ , Cu2+ , Mn2 ). The superior capability of Fe2+ /H2 O2 in causing the degradation of sildenafil indicates that Fe2+ efficiently decomposes H2 O2 to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H2 O2 can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe3+ , Co2+ , Cu2+ , and Mn2+ . A unique oxidation by-product was detected in the reaction between Fe2+ /H2 O2 with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on-surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS-MS shows to be a convenient platform to promptly monitor on-surface oxidation reactions.

RESUMO

A qualitative multiresidue method that facilitates rapid monitoring of veterinary drugs in porcine muscle is described. The method comprises the application of an innovative extraction/clean-up procedure, namely liquid-liquid extraction with partition at very low temperature (LLE-FPVLT), and analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Besides the high selectivity, sensitivity and specificity, this high-throughput method proved to be quite general as 34 veterinary drugs (from six distinct classes: tetracyclines, sulfonamides, penicillins, quinolones, macrolides and benzimidazoles) could be successfully detected. The whole screening procedure was validated according to the directives from European Commission Decision 2002/657/EC and guidelines for the validation of screening methods. Acceptable values for the evaluation parameters were achieved for all analytes (except for ampicillin, clindamycin and erythromycin). Finally, these very promising results have strengthened the possibility of inclusion of such a methodology as an integral part of the National Residue Control Plan scope of the Ministry of Agriculture, Livestock and Food Supply of Brazil.

Assuntos

RESUMO

Rapid quantitative enantiomeric analysis of mannose, glucose, galactose, and ribose is achieved using electrospray ionization and cluster ion dissociation with data analysis by the kinetic method. Several modified amino acids (N-Ac-L-Phe, N-benzoyl-L-Phe, N-t-Boc-L-Phe, N-Ac-L-Pro, N-t-Boc-L-Pro, N-Fmoc-L-Pro, N-Ac-L-Tyr, O-Me-L-Tyr) and four transition divalent metal cations (Co2+, Cu2+, Ni2+, and Zn2+) were tested to select the best system for chiral recognition and quantitation of each sugar. Quantitative determinations of the enantiomeric compositions of sugar solutions were achieved using either multiple- or two-point calibration curves; differences between the actual and experimental values were <2% enantiomeric excess (ee).

Assuntos

RESUMO

Chloroform formation during the chlorination of simple organic molecules modeling humic substances, such as phenol and di- and trihydroxybenzenes, was studied by on-line membrane introduction mass spectrometry (MIMS). Under the reaction conditions employed, chloroform was rapidly formed from 1,3-dihydroxybenzene, 1, 4-dihydroxybenzene, phenol and 1,2,3-trihydroxybenzene with yields of 17, 13, 7 and 5%, respectively. With the exception of aniline, which afforded a 17% chloroform yield, non-phenolic compounds, such as nitrobenzene, chlorobenzene, toluene, benzene and cyclohexanol, furnished low yields. Mechanistic studies showed that phenol is chlorinated consecutively and produces initially chlorophenol. It is suggested that chloroform might be formed mainly from chlorinated 3, 5-cyclohexadienone-type intermediates. MIMS was also used to determine the reaction rates and to study the kinetics of the chlorination. A good Hammett linear correlation for an electrophilic substitution mechanism was found for the compounds C(6)H(5)X (X = NH(2), OH, CH(3), H, Cl and NO(2)).

Assuntos