• Universitat de València

Infrared spectra of samples often show the presence of interferences caused by gases and vapours present in the compartment in which the sample to be measured is introduced. Such interferences are detrimental to the quality of the measurement, especially when these ambient gases and/or vapours have absorption bands in the spectral region of interest. To avoid this contribution, the sample chamber is typically sealed and undergoes a purging process using dry air or nitrogen. However, there is still interest in correcting spectra by correction methods when i) purging of the chamber is not possible or does not work properly, ii) the sample chamber is opened and the operator underestimates the time needed to equilibrate the conditions inside the chamber or iii) the sampling device does not allow the chamber to be closed. Currently, there is some commercial software that compensates only for the vapour contribution of water vapour and CO2 in infrared spectra. Therefore, there is a need for a general compensation method for environmental gases and/or vapours in the field of infrared spectroscopy that allows all such interferences to be removed sequentially.

Researchers at the Universitat de València have developed a procedure for the compensation of environmental gases and/or vapours in infrared spectroscopy measurements, as well as the computer program associated with this procedure. The procedure of the invention makes it possible to obtain a corrected infrared spectrum of the sample under analysis in which the contribution of the gases and/or vapours present in the chamber in which the measurement is made is accurately, robustly and efficiently eliminated. The algorithm is based on the measurement of a spectrum containing the bands of the environmental gas or vapour to be removed followed by the automatic estimation of the spectral contribution of the interferences in the sample to be corrected. This contribution is then compensated by a simple spectral subtraction. Furthermore, the method is computationally very fast and can be universally applied for different types of solid, liquid or gaseous samples and measurement conditions.

The main application of the technology is in the chemical sector, as a method of correcting the contribution of ambient gases and/or vapours in the infrared spectra, which improves the selectivity and detection limits of the measurements.

The main advantages provided by the invention are:

• Ease of use, it is only necessary to obtain a spectrum of the vapour or gas to be corrected under the same measurement conditions as the spectra of the samples in order to select relative absorbance values.
• Speed, the computation is fast as the algorithm is simple.
• It is a universal method, it can be applied in many situations (different samples and equipment, different measurement conditions). Corrects for gases other than H2O and CO2.
• The method does not apply smoothing to the spectra, avoiding distortion of the infrared bands of the analytes of interest.
• Improved results obtained using commercially available software tools.

• Patent granted