Francisco L. Thalita O.
Duarte a. Allan N. Dantas b. Gisele S.
Excited mercury complexes - ACS Publications - American Chemical
Lopes a. Sandro T. Gouveia a. Wladiana O. Flame atomic absorption spectrometry FAAS and inductively coupled plasma optical emission spectrometry ICP OES are widely used in academic institutions and laboratories for quality control to analyze inorganic elements in samples. However, these techniques have been observed to underperform in sample nebulization processes.
Most of the samples processed through nebulization system are discarded, producing large volumes of waste. The treatment of the waste was performed by the precipitation of elements using NH 4 2 CO 3.
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The precipitate produced from the treatment of residues can be reused as a potential sample in undergraduate qualitative analytical chemistry lab classes, providing students the opportunity to test a real sample. Although the quantity of residues produced by academic research laboratories is negligible when compared with those produced by industrial activities, universities cannot ignore their responsibility for the residues generated because the environmental issue is a global concern.
Moreover, this behavior toward the environmental issue appears to be contradictory to the development of environmental researches at universities. Research laboratories at universities produce several types of residues with specific characteristics depending on the studies developed by each laboratory. Thus, it is difficult to establish a standard treatment or disposal protocol for these wastes.
It is very important that each laboratory assume responsibility and propose strategies for the treatment of its own waste. Some studies 7 - 9 in the literature report the reuse of practical lessons wastes, but there is still necessary more procedures to treat wastes from labs, especially research labs. Flame atomic absorption spectrometry FAAS and inductively coupled plasma optical emission spectrometry ICP OES are spectrometric techniques typically employed in academic and industrial chemical laboratories for trace element analysis.
FAAS is a monoelemental, easy-to-implement and low-cost technique. The principle of FAAS is based on the measurement of electromagnetic radiation absorption from a radiation source by gaseous atoms in a fundamental state produced by a flame at temperatures of up to K. ICP OES is a multielemental technique through which it is possible to identify more than 70 elements in less than 2 min. The plasma is a partially ionized gas composed of electrons, ions and neutral particles that reaches temperatures between and K, sustained by energy from a radio-frequency source operating at 27 or 40 MHz.
Atoms and molecules are promoted to excited states by absorbing energy from the electrons and atoms of the excited argon gas. The excited species return to their fundamental states by emitting photons, which are measured by a detection system. Generally, in FAAS and ICP OES, samples are introduced in the form of solutions, which are transformed into aerosols through a nebulization process before they reach the atomizer of the spectrometer. The species found in this waste depend on the elements and samples routinely analyzed in the laboratory.
Over this period, the laboratory handled several types of samples water, food, plant, soil, paint, wax, etc. All solutions were prepared using ultrapure water resistivity of In qualitative studies, the reagents used were those available in the laboratory of Qualitative Analytical Chemistry for university graduates: 6.
The reducing solution of 0. A Micronal B pH meter and a combined glass electrode were used to measure the pH of the solutions. The sample was introduced into the ICP device using a cross-flow nebulizer with a double-pass spray chamber. A central tube torch with an internal diameter of 2. An atomic absorption spectrometer Varian Model SpectrAA Fast Sequential was used to carry out selenium determination by hydride generation.
The hydride was continuously produced with a Varian vapour generation accessory Model VGA , equipped with gas-liquid separator adapted to a FIA system. A high intensity selenium hollow cathode lamp Varian UltrAA operating at a lamp current of 15 mA was used as an excitation source.
All measurements were carried out at A spectral slit-width of 0. The final volume of the sample after heating was mL. This solution was neutralized with 3. The mixture was left to stand overnight and filtered. Qualitative analytical chemistry is a mandatory discipline for all courses in related science areas at university in Brazil. In addition to the area of chemistry, pharmacy, engineering, oceanography, zootechnology, geology, etc. In general, at the end of the experimental courses, students receive a sample and they may spend two lab class periods identifying the cation and the anion present in the sample, which is, in fact, an unknown salt but not an actual sample.
It would be interesting if students could have the opportunity to work with actual samples to approximate their experience to that of professionals.
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Role played by the N2(A3Σu+) metastable in stationary N2 and N2-O2 discharges - IOPscience
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