Laser‐induced breakdown spectroscopy (LIBS) is a new type of elemental analytical technology with the advantages of real‐time, online, and noncontact as well as enabling the simultaneous analysis of multiple elements. It has become a frontier analytical technique in spectral analysis. However, the issue of how to improve the accuracy of qualitative and quantitative analyses by extracting useful information from a large amount of complex LIBS data remains the main problem for the LIBS technique. Chemometrics is a chemical subdiscipline of multi‐interdisciplinary methods; it offers advantages in data processing, signal analysis, and pattern recognition. It can solve some complicated problems that are difficult for traditional chemical methods. In this paper, we reviewed the research progress of chemometrics methods in LIBS for spectral data preprocessing as well as for qualitative and quantitative analyses in the most recent 5 years (2012‐2016).

Chemometrics in laser‐induced breakdown spectroscopy

Calibration strategies for the direct determination of Ca, K, and Mg in commercial samples of powdered milk and solid dietary supplements using laser-induced breakdown spectroscopy (LIBS)

Described for the first time is the use of elemental analysis of diabetic toenails and machine learning techniques for the robust classification of type-2 diabetes. Aluminum, Cs, Ni, V and Zn concentrations in toenails were found to be significantly (p

Combining elemental analysis of toenails and machine learning techniques as a non-invasive diagnostic tool for the robust classification of type-2 diabetes

The steady advances in technology employed in smartphones, coupled with the high availability and the ease access to these devices, increased the interest in applying it to analytical purposes. The main goal is to develop simple, fast, and low‐cost analytical methods, generating immediate results. Different analytical strategies using smartphones have been proposed to identify or determine different analytes in a wide range of matrices. Some of them use the smartphone to capture the images, to process them, and to provide the analytical results. Others use this device just for image acquisition. In this context, this review aimed to relate previous works that used smartphones to acquire images for analytical purposes, with a special focus on PhotoMetrix application, which is a tool for chemical analysis. This application allows the decomposition of digital images acquired by smartphone cameras and to process them within the same device, allowing in situ chemical analysis.

PhotoMetrix and colorimetric image analysis using smartphones

An environment-friendly spot test method with digital imaging for the micro-titration of citric fruits

This study proposes classification models for the prediction of the quality parameters of cattle and sheep leathers In total, 375 leather samples were directly analyzed by laser-induced breakdown spectroscopy (LIBS) Exploratory analysis using principal component analysis (PCA) and classification models employing K-nearest neighbor (KNN), soft independent modeling of class analogy (SIMCA), and partial least squares – discriminant analysis (PLS-DA) were the chemometric tools used in the multivariate analysis The goal was to classify the leather samples according to their quality The calculated models have satisfactory results with correct prediction percentages ranging from 752 (for SIMCA) to 805 (for PLS-DA) for the calibration dataset and from 716 (for SIMCA) to 809 (for KNN) for the validation samples The proposed method can be used for preliminary leather quality inspection without chemical residues generation

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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 a new and simple method for Cr speciation and Cr(VI) determination in leather samples using digital images. The experiments were performed using a mobile phone and a free app called PhotoMetrix that was used to obtain and process data. The results obtained from PhotoMetrix were compared to reference methods using UV−Vis spectroscopy. A statistical evaluation between both proposed and the reference methods using two-sample t-test did not show a significant difference at a 95% confidence level. Bovine leather samples (4 samples) tanned with Cr salts and ovine leather samples (3 samples) tanned with vegetable tannin were analyzed. The proposed method presented limits of detection (LOD) and quantification (LOQ) of 0.6 and 2 mg/kg, respectively. In addition, the proposed method using PhotoMetrix and digital images can provide undergraduate students an opportunity to learn topics such as quantitative analyses, environmental chemistry, speciation chemistry, image processing and treatment of statistical data. The results demonstrated that the proposed method can be applied to routine analyses and in experimental analytical chemistry courses.

/pdf/chromium-speciation-in-leather-samples-an-experiment-using-2p8gyew3t7.pdf

Chromium speciation in leather samples: an experiment using digital images, mobile phone and environmental concepts

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).

Evaluation of the Chemical Composition of Synthetic Leather Using Spectroscopy Techniques.

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.

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

Ariane Maciel Neiva

Papers

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

Chromium speciation in leather samples: an experiment using digital images, mobile phone and environmental concepts

Evaluation of the Chemical Composition of Synthetic Leather Using Spectroscopy Techniques.

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