Direct Determination of Ca, K and Mg in Cassava Flour Samples by Laser-Induced Breakdown Spectroscopy (LIBS)
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Direct Determination of Ca, K and Mg in Cassava Flour Samples by Laser-Induced Breakdown Spectroscopy (LIBS) Vinicius Câmara Costa 1 & Diego Victor de Babos 1 & Francisco Wendel Batista de Aquino 1 & Alex Virgílio 1 & Fábio Alan Carqueija Amorim 2 & Edenir Rodrigues Pereira-Filho 1
Received: 31 August 2017 / Accepted: 27 October 2017 # Springer Science+Business Media, LLC 2017
Abstract This study aims to develop a method for direct determination of Ca, K, and Mg in cassava flour samples by laser-induced breakdown spectroscopy (LIBS). LIBS instrumental parameters were evaluated using factorial design with a central point. The variables evaluated were delay time (0.0; 1.0 and 1.8 μs) and fluence (81; 2037 and 4074 Jcm−2): both were tested in three different values. The best results obtained were with a delay time of 1.8 μs and a fluence of 4074 Jcm−2. The proposed calibration model obtained using LIBS data presented a good correlation with reference values obtained by inductively coupled plasma atomic emission spectrometry (ICP OES). The predictive capabilities, based on the standard error of validation (SEV), were 117, 530 and 77 mg kg−1 for Ca, K, and Mg, respectively. The proposed LIBS method was applied to the analysis of 90 cassava flour samples, and the results showed concentrations of Ca, K, and Mg of 352–1845, 1285–3187, and 320–1242 mg kg−1, respectively. Keywords LIBS . Cassava flour . Direct determination . Univariate calibration . Normalization mode
Introduction Cassava flour represents one of the main nutrient sources in the diet of populations in developing countries, especially * Edenir Rodrigues Pereira-Filho [email protected] 1
Group of Applied Instrumental Analysis, Department of Chemistry, Federal University of São Carlos, São Carlos, São Paulo 13565-905, Brazil
2
Department of Exact and Technological Sciences, State University of Santa Cruz, State, Ilhéus, Bahia 45662-900, Brazil
those with low incomes (FAO 2015). It is a rich source of fiber, carbohydrates, vitamins, and minerals. The main essential elements available in cassava flour are Ca, K, and Mg (Da Silva et al. 2017). Several analytical techniques, such as flame atomic absorption spectrometry (FAAS) (Amorim et al. 2016; Amorim et al. 2017), inductively coupled plasma optical emission spectrometry (ICP OES) (Linhares and Nóbrega 2017), and inductively coupled plasma-mass spectrometry (ICP-MS) (Pinheiro et al. 2017), have been applied to determine the elemental concentration in food samples (Korn et al. 2008). In general, these techniques require a sample pre-treatment to convert the solid material to a homogeneous aqueous solution through the procedures of acid digestion (Ferreira et al. 2013; Korn et al. 2008). In addition, the sample is diluted promoting a loss in sensitivity and, depending on the analytical technique used for measurement, the analyte becomes undetectable. Systematic errors can also be introduced due to contamination or loss by volatilization, which affect the accuracy of the results (Bizzi et al. 2017). In contrast
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