Determination of toxic metals in leather by wavelength dispersive X-ray fluorescence (WDXRF) and inductively coupled plasma optical emission spectrometry (ICP OES) with emphasis on chromium

The tanning industry is one of the largest environmental polluters due to high generation waste in all production processes, but the tanning is particularly worrisome due to the use of significant amounts of chromium. Cr is an element potentially toxic to both health and the environment, depending on the concentration and the oxidation state. Cr(VI) can come in contact with human skin when using leather goods, which can cause allergies and dermatitis, besides being carcinogenic. Considering that approximately 90% of the world production of leather is performed with Cr salts, the determination of this element in leather is necessary to avoid exposure to the risks that the element can provide. The main goal of this study was the development of an alternative analytical method for the determination of Cr in leathers (ovine and bovine leather tanned with Cr and vegetable tannin) using wavelength dispersive X-ray fluorescence (WDXRF) for direct solid analysis. Besides performing analysis of the chemical composition and determination of Al, As, Ba, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb, Sb, Sr, Ti, and Zn in leather by inductively coupled plasma optical emission spectrometry (ICP OES). Principal component analysis (PCA) was also used in the evaluation of the WDXRF and ICP OES data sets. WDXRF calibration models for Cr presented satisfactory figures of merit and the analysis of the leathers revealed an alarming concentration of total Cr in the samples reaching 21,353 mg kg^-1.

Evaluation of the Chemical Composition of Synthetic Leather Using Spectroscopy Techniques

Synthetic leather samples from Brazil and Paraguay were evaluated in this study using three spectroscopy techniques: inductively coupled plasma optical emission spectrometry (ICP-OES), laser-induced breakdown spectroscopy (LIBS), and wavelength dispersive X-ray fluorescence (WDXRF). The obtained information from each technique was separately inspected with principal component analysis (PCA). The concentrations of the elements determined in the synthetic leathers using ICP-OES decreased in the following order: Ca > Cr > Mg > Ba > Pb > Al > Fe > Zn > Sb > Ni with a concentration range below the limit of quantification (<LOQ, case of Ni) to 112 233 mg kg^-1 (case of Ca). Additionally, Cu, As, Sr, Ti, Cd, Mn, Co, and Ni were present in only few samples in a concentration range from <LOQ to 163 mg kg^-1. Principal component analysis was the tool used to evaluate the samples from their chemical content obtained quantitatively using ICP-OES and qualitatively using LIBS or WDXRF spectra. The results showed that the association of PCA with spectroscopic techniques was satisfactory for data inspection of synthetic leathers according to the chemical composition. Laser-induced breakdown spectroscopy and WDXRF were able to identify the presence of toxic elements like Cr (LIBS and WDXRF) and Pb (WDXRF).

Proposition of classification models for the direct evaluation of the quality of cattle and sheep leathers using laser-induced breakdown spectroscopy (LIBS) analysis

This study proposes classification models for the prediction of the quality parameters of cattle and sheep leathers.