Fabiano Barbieri Gonzaga

Laser Induced Breakdown Spectroscopy

This review describes the fundamentals, instrumentation, applications and future trends of an analytical technique that is in its early stages of consolidation and is establishing its definitive niches among modern spectrometric techniques. The technique has been named Laser Induced Breakdown Spectroscopy (LIBS) and its main characteristic stands in the use of short laser pulses as the energy source to vaporize samples and excite the emission of electromagnetic radiation from its elements and/or molecular fragments. The emitted radiation is analyzed by high resolution optics and the intensities are recorded, usually by fast triggered solid state detectors. Together, these devices allow producing and registering a wide ranging emission spectrum of the short-lived phenomenon induced by the laser pulse. The spectrum contains qualitative and quantitative information which can be correlated with sample identity or can be used to determine the amount of its constituents. This review is divided in four parts. First, the relevant historical and theoretical concepts associated with LIBS are presented; then the main practical aspects of the several experimental and instrumental approaches employed for implementation of the technique are critically described; the applications related in the literature, including those making use of chemometrics, are classified and exemplified with relevant and recently published work. Finally, an attempt to portray an overall evaluation and future perspectives of the technique are presented.

A low cost short wave near infrared spectrophotometer: Application for determination of quality parameters of diesel fuel

A low cost absorption spectrophotometer for the short wave near infrared spectral region (850-1050 nm) is described. The spectrophotometer is basically composed of a conventional dichroic lamp, a long-pass filter, a sample cell and a Czerny-Turner type polychromator coupled to a 1024 pixel non-cooled photodiode array. A preliminary evaluation of the spectrophotometer showed good repeatability of the first derivative of the spectra at a constant room temperature and the possibility of assigning some spectral regions to different C-H stretching third overtones. Finally, the spectrophotometer was successfully applied for the analysis of diesel samples and the determination of some of their quality parameters using partial least squares calibration models. The values found for the root mean square error of prediction using external validation were 0.5 for the cetane index and from 2.5 to 5.0 degrees C for the temperatures achieved during distillation when obtaining 10, 50, 85, and 90% (v/v) of the distilled sample, respectively.

Near-Infrared Spectropolarimetry Based on Acousto-Optical Tunable Filters

A new approach to near-infrared (NIR) spectropolarimetry is described, in which the properties of a noncollinear acousto-optical tunable filter (AOTF) made of an anisotropic crystal of TeO2 is employed to produce a novel instrument that precludes or reduces significantly the use of mechanical parts and simplifies the acquisition of optical rotation spectra of absorbing species in the NIR region. In essence, the instrument is based on the measurement of the relative beam intensities produced when a 45 degrees plane polarized beam of radiation passes through a sample cell and is directed to the entrance window of the AOTF. Because of the crystal anisotropy, two planar and orthogonally polarized beams will leave the AOTF, angularly split from the nondiffracted beam, after the acousto-optical interaction has occurred. If an optically nonactive sample is present in the cell, equal intensities for both diffracted beams should be observed. On the other hand, the presence of an optically active sample will cause the polarization plane to rotate and a consequent difference in the intensities of the AOTF diffracted beams will be registered as a function of the optical activity of the sample. The instrument has been evaluated with aqueous solutions of sucrose, glucose, and fructose and for three forms of camphor (d, l, dl).

Evaluation study of an ion selective field effect transistor electrode for measuring quality parameters of fuel ethanol

An ion selective field effect transistor (ISFET) electrode was evaluated for measuring pH and acid number (AN) of fuel ethanol and compared to two glass electrodes with different reference filling solutions: KCl aqueous solution (glass-KCl electrode) and LiCl ethanolic solution (glass-LiCl electrode). pH was determined at different measurement times and AN was determined using automatic potentiometric titration. For pH, the glass-KCl electrode showed the best precision and stability, with an average repeatability about four times better when compared to the ISFET electrode for the measurement time of 30 s (as indicated in the ASTM D6423 standard). For AN, the glass-KCl and glass-LiCl electrodes showed similar repeatabilities, which were about three times better than that of the ISFET electrode. In addition, the results from a recovery study demonstrated better accuracy of the glass-LiCl electrode, with a recovery value of 100.1%.

Developments of Environmental Certified Reference Material from the Brazilian Metrology Institute to Support National Traceability

This paper aims to present the developments performed by the Brazilian Metrology Institute NMI-Inmetro, considering the environmental demand. Inmetro addresses great part of its activities to the study of the traceability transference based on production and dissemination of certified reference material CRM of different areas in chemistry. It will be presented results from certification of the following reference materials developed: BTEX and PAH in solution, besides automotive emission gas mixtures and bioethanol. So, the achievements made are the growth in developing CRM, in order to support the needs of the national industry and to disseminate traceability among the society.

Report of the key comparison APMP.QM-K19. APMP comparison on pH measurement of borate buffer

The APMP.QM-K19 was organised by TCQM of APMP to test the abilities of the national metrology institutes in the APMP region to measure a pH value of a borate buffer. This APMP comparison on pH measurement was proposed by the National Metrology Institute of Japan (NMIJ) and the National Institute of Metrology (Thailand) (NIMT) at the APMP-TCQM meeting held 26?27 November 2012. After approval by TCQM, the comparison has been conducted by NMIJ and NIMT. The comparison is a key comparison following CCQM-K19 and CCQM-K19.1. The comparison material was a borate buffer of pH around 9.2 and the measurement temperatures were 15 ?C, 25 ?C and 37 ?C. This is the second APMP key comparison on pH measurement and the fourth APMP comparison on pH measurement following APMP.QM-P06 (two phosphate buffers) in 2004, APMP.QM-P09 (a phthalate buffer) in 2006 and APMP.QM-K9/APMP.QM-P16 (a phosphate buffer) in 2010?2011. The results can be used further by any participant to support its CMC claim at least for a borate buffer. That claim will concern the pH method employed by the participant during this comparison and will cover the used temperature(s) or the full temperature range between 15?C and 37 ?C for the participant which measured pH values at the three temperatures. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Avaliação de laboratórios brasileiros na determinação de alguns parâmetros de qualidade de biocombustíveis

This work shows the results of a Proficiency Testing performed by a partnership between INMETRO and ANP. The performance of 49 Brazilian laboratories (using the z-score statistical test) in determining 10 quality parameters of ethanol fuel and biodiesel was evaluated. The certified reference values were provided by INMETRO, allowing a more rigorous assessment of the laboratories. For hydrous ethanol, the acidity parameter showed the lowest number of laboratories with satisfactory results (48%), while 85% of the laboratories presented satisfactory results for ethanol content. For biodiesel, the percentage of laboratories with satisfactory results ranged from 46% (kinematic viscosity) to 92% (acid number).