Determination of Iron, Copper, Zinc, Aluminum, and Chromium in Biodiesel by Flame Atomic Absorption Spectrometry Using a Microemulsion Preparation Method

Abstract

This work proposes a flame atomic absorption spectrometry (FAAS) method for Fe, Cu, Zn, Al, and Cr determination in biodiesel using water in oil (w/o) microemulsion (ME) as a sample preparation method. A less toxic solvent (n-propanol), instead of those used in the standard method (ABNT NBR 15556), the absence of surfactant, and calibration using inorganic reference standards were investigated. A ternary phase diagram of biodiesel as oil, water, nitric acid, and n-propanol showed a single-phase ME region. The composition of ME adopted for analysis was 1.7 g of biodiesel and 1.1 mL of 1.4 mol L–1 HNO3, completed with n-propanol to 10 mL volume. Linear calibration graphs with R > 0.99 were obtained using ME prepared with oleic acid and inorganic standards. Analytes were stable for at least 3 days both in sample and in metallic standards MEs. The limits of detection obtained were 0.3, 0.1, 0.07, 1.7, and 1.0 mg kg–1 for Fe, Cu, Zn, Al, and Cr, respectively. These limits of detection were lower than those obtained by the reference method of dilution with organic solvent, due to lower fluctuation in the measurements. Recovery test values (93–105%) indicated absence of matrix effects. In order to assess the method accuracy, several real samples were analyzed by the proposed method, by the standard method, and also by acid digestion, without significant differences between results when applying the student’s t test. Relative standard deviations lower than 5% were obtained for standard and samples MEs. Therefore, combination of w/o ME with the FAAS technique and calibration with inorganic standards proved to be an accurate, simple, fast, and practical strategy, with greater analyte stability and appropriate sensitivity, so that the proposed method is suitable for biodiesel routine analysis.

Highly Efficient and RecyclableShewanella xiamenensis-Grafted Graphene Oxide/Poly(vinyl alcohol) Biofilm Catalysts for Increased Cr(VI) Reduction

“…The stability of S. xiamenensis grafted onto GO/PVA biofilms was evaluated according to the total biomass grafted onto the biofilms measured by the bicinchoninic acid (BCA) method . Additionally, we used a flame atomic absorption spectroscopy (Bio-Rad, US) instrument to measure the concentrations of Cr­(VI) and the diphenylcarbazide spectrophotometric method to measure Cr­(T). , …”

“…30 Additionally, we used a flame atomic absorption spectroscopy (Bio-Rad, US) instrument to measure the concentrations of Cr(VI) and the diphenylcarbazide spectrophotometric method to measure Cr(T). 31,32 Data Analysis. Data were analyzed and displayed using the Origin 8.0, Microsoft Excel 2010, and SPSS 20.0 software.…”

An Indole-Based Fluorescent Chemosensor for Detecting Zn2+ in Aqueous Media and Zebrafish

“…Various analytical methods, like electrochemical methods, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and atomic absorption spectrometry (AAS), have been applied for determining zinc ions [ 13 , 14 ]. However, they require complicated sample preparation, expensive instruments and time-consuming procedures [ 15 ].…”

Sensitive Aptamer SERS and RRS Assays for Trace Oxytetracycline Based on the Catalytic Amplification of CuNCs

“…To obtain CuNCs with good stability, and a suitability for experimental use, surface ligands can be added for protection during preparation, which can control the stability and rate of nanocrystalline nucleation. In combination with different methods to improve the stability of CuNCs, more synthesis processes and methods have been experimented with, such as water-in-oil (w/o) micro emulsion strategies [ 5 ] and the Brust-Schiffrin method [ 6 ], among others. It is reported that CuNCs have a great potential in optical sensing [ 7 ], environmental monitoring [ 8 ], and medical-related applications [ 9 , 10 ].…”