Instruments Central Unit

Nuclear Magnetic Resonance (NMR) Spectrometers

Our Centre possesses a Brucker ACP-200 and Brucker AVANCE-400 NMR facilities, equipped with automatic detectors 1H, 13 C and 31P; 200 MHz and 2H spectrophotometer.They also may detect 19F, and the 400MHz spectrometer, a whole range of atoms from 31P - 109Ag. The Advance-400 instrument is already equipped with a 5mm inverted detection probe and Z gradients, allowing to made both homo (RMN-1D) and heteronuclear (RMN-2D) experiments, and gradient-field experiments as well. Variable temperature unit enables to analyze liquid samples from -150 ºC to +125 ºC for thermodynamics or kinetics studies.

Applications

The NMR technique allows obtaining a spectrum or graphic diagram with a different signal for each type of atom in the solutions analyte. Thus the NMR spectrum of a substance for a specific element is unique, regarding the location of the signal (chemical shift) and its shape. It also allows correlating each atom signal with neighboring atoms due to spin magnetic interactions (spin-spin coupling). This technique makes NMR a unique research tool for the investigation of chemicals, because chemical shifts and spin-spin coupling depend on atomic structure and distinctive bonds between them, besides geometry or molecular conformation. Because the area under the integration curve is proportional to both the number of atoms and sample concentration, the NMR facility provides a simple and effective means of determining quantities of material in the sample either as a pure sample or a mixture.

Bidimensional techniques in an experiment allow to correlate atoms inside a substance, either by spin-coupling (chemical bonds) or dipoles (spatial interactions). Normally these experiments take more than two hours; the new NMR facilities including digital technology, however, do not take longer than 30 minutes. Variable temperature unit gives the possibility of conducting conformational studies in solutions and determining the equilibrium constant for a chemical reaction, and also to analyze in situ the kinetics of chemical reactions.

Infrared spectrophotometer

Our facility includes a Vector 22 model with Bruker Fourier-transformed proton frequencies (FT-MIR). It analyzes solid samples in KBr and Nujol pills or other solid devices and film liquid samples. It does not have gaseous samples accessories.

Applications

An infrared spectrometer displays short-wave bands at different wave-numbers for different types of chemical bonds in a chemical compound. This wave-number is directly proportional to the incident radiation energy within infrared range along with vibration-link energies.
An atomic bond may have several vibrational modes, depending on the type of movements of the vibrating atoms. This makes absorption bands within the infrared spectrum for an atomic bond being unique in terms of their wave-length and form. Because of their remarkable characteristics, this technique is used to study functional groups of substances obtained from chemical synthesis and extraction.

Moreover, it allows corroborating the purity of a substance by comparing its spectrum with a pattern. It is particularly useful to compare so-called “chemical fingerprints”, which corresponds to the region under less than 600 cm-1, because in favorable situations it is possible to measure the absorption signal of a substance quantified by means of a calibration curve.

Mass Spectrometry C-H-N-S Analyzer

CE Instruments EA 1108 model, set to perform the simultaneous determination of carbon, hydrogen, nitrogen and sulfur in less than 15 minutes. It can also change settings to determine only oxygen or sulfur in separated experiments.

Applications

Due to the use of catalysts it is possible to burn quantitatively, in flash or quick combustion, organic and organo-metallic samples, transforming thus all hydrogen into H2O, carbon into CO2 and sulfur into SO2. For this purpose a 2mg sample is weighed, wrapped in a tin plate and burned in a furnace at 1000 degrees. Shortly afterwards, tin oxidation process raises temperature up to 1800 degrees and the products of this reaction are treated with tungsten dioxide to oxidize 100% of the sample. Later, gases are passed through thin copper wires to obtain N2, CO2, H2O and SO2. Resulting gases are processed by column chromatography to separate them and also generate signals in a thermal conductivity detector (TCD), subsequently processed by computer. Standard substances such as acetanilide and sulfanilamide are used to create a calibration curve, and thus obtain directly mass percentage (% P/P) of the sample with an approximate error of no more than 0.3 %.

To publish the synthesis of a new substance or for characterization work a fundamental requirement is to report the mass percentage with the accuracy of this equipment.

Our the Instruments Central Unit and Research Laboratories invite you to check the new web service for admission of NMR samples.