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Trace amounts of copper decrease significantly the oxidative stability of biodiesel while antioxidants, mostly tert -butylhydroquinone (TBHQ), are commonly introduced to the biofuel to guarantee induction period values within regulatory limits. Hence, a simple method to monitor the most used antioxidant and the most deleterious contaminant in biodiesel can give a fast response on its quality. In this context, this work presents a simple, efficient, low cost and sensitive method for the simultaneous and direct determination of copper and the antioxidant TBHQ in biodiesel. The biodiesel samples were diluted in 90% (v/v) ethanol and 10% (v/v) water containing 0.1 mol L−1 HCl (final concentration) as the supporting electrolyte generating a homogeneous mixture in which Cu(II) and TBHQ were directly detected using the square wave voltammetry (SWV) on a gold working electrode. The presence of biodiesel in the selected electrolyte facilitated the separation of analyte peaks facilitating the treatment of data and quantification. The linear responses for the simultaneous determination were in the range between 5 and 100 μg L−1 and 4.2–81.5 mg L−1 for copper and TBHQ (R > 0.997), respectively. High precision (RSD = 4.0% and 3.9%, n = 20) and limit of detection (LOD) values of 0.31 μg L−1 and 1.0 mg L−1 (0.030 μg g−1 and 0.102 mg g−1 in biodiesel) for Cu(II) and TBHQ, respectively, were obtained. Recovery values between 97% and 104% for both copper and TBHQ were obtained. Image 1 • Rapid method for simultaneous determination of copper and the antioxidant TBHQ in biodiesel. • Biodiesel aliquot 100-fold diluted in hydroethanolic electrolyte with 0.1 mol L−1 HCl in the cell. • The presence of biodiesel facilitated the separation of the voltammetric peaks of analytes. • LOD values of 0.030 μg g−1 and 0.102 mg g−1 in biodiesel for Cu(II) and TBHQ, respectively. • Fast protocol to identify metallic contaminants and attest the required presence of TBHQ. [ABSTRACT FROM AUTHOR]

Abstract The corrosive character of Moringa oleifera Lam biodiesel was evaluated through static immersion tests with different carbon steels (CS1015 and CS4140) in absence and presence of the antioxidant tert-butylhydroquinone (TBHQ), at room temperature in the absence of light for 84 days. Biodiesel parameters, including oxidation stability (induction period, IP), total acid number (TAN) and iron concentration released from carbon steel, were monitored. The produced biodiesel presented an IP value of 4.9 h, which was increased to 6.2 h after the addition of 500 mg kg−1 TBHQ. After 84 days of immersion, IP values decreased in the first 21 days due to the contact with the metallic coupon, while TBHQ retarded this process. TAN value increased in 20% but the values were below the recommended limits (<0.5 mg g−1 KOH according to EN14214). Iron was detected in the biodiesels exposed to CS1015 (8 μg g−1), while in the presence of TBHQ this value decreased to 5 μg g−1, indicating corrosion inhibition by TBHQ. Iron was not detected in the biodiesels exposed to CS4140, which indicated that this material was more compatible with biodiesel. Notably, the oxidation stability of Moringa biodiesel was not affected (IP > 3 h) by the high Fe content. Highlights • Static immersion corrosion test to simulate storage conditions of Moringa biodiesel. • Carbon steels of varied composition were evaluated and metal release measured. • Oxidation stability of biodiesel decreased as corrosion started. • The antioxidant TBHQ retarded the corrosion as iron release decreased. • Addition of TBHQ is required to extend storage stability of Moringa biodiesel. [ABSTRACT FROM AUTHOR]

This work reports the use of eucalyptus pulp as an adsorbent for metal removal from biodiesel. Fatty acid methyl esters produced from sunflower oil (SfMB) and recycled used cooking oil (RMB), which contained Fe, Mn, and Cu, were treated through filtration on a column filled with the cellulosic adsorbent, and washed with deionized water for comparison. The treatment with cellulose material resulted in the removal of 13–81%, 35–84%, and 40–74% of Fe, Mn, and Cu in biodiesels, while the water washing removed 4–40%, 10–47%, and 4–19%, respectively. In addition to the higher efficiency, the use of cellulose is a more environmentally friendly process than the purification with water, once the latter results in a considerable volume of effluent requiring treatment prior to disposal, besides the high consumption of water. Moreover, the regeneration of the cellulosic adsorbent is demonstrated. [ABSTRACT FROM AUTHOR]

This work demonstrates the potential use of tetrahydrocurcuminoids (THCs) as natural antioxidants to enhance the oxidation stability of biodiesels. Fatty acid methyl esters produced from cottonseed and residual cooking oils were doped with three different THCs, curcumin and synthetic antioxidants for comparison. The THC derivative with a phenol group in meta -position of the linking chain and a neighboring methoxy group provided higher oxidation stability (induction period values) in both biodiesels in comparison with other THCs and curcumin. Moreover, this THC derivative presented better efficiency than butylated hydroxytoluene in one of the studied biodiesels. This result is in agreement with antioxidant activity data for the three TCHs and curcumin reported in the literature. Additionally, THCs are colorless (instead of curcumin) which increases the market acceptance of such additives for biodiesel. [ABSTRACT FROM AUTHOR]

Abstract: This communication reports the development of an algorithm for correction of specific gravity of biodiesels. The specific gravity of cottonseed oil biodiesels (for example) was measured at different temperatures and the algorithm was proposed for correction of this parameter depending on temperature, which highly influences loading and discharging of biodiesel. The obtained algorithm differs from that reported in EN 14214 and suggests that individual algorithms should be obtained for biodiesels produced from different oil sources. [Copyright &y& Elsevier]

Highlights: [•] Biodiesels with low oxidation stability (OS) were blended with soybean biodiesel. [•] Residual cooking oil and cottonseed oil biodiesels had their OS improved. [•] Sunflower oil biodiesel had its OS improved by blending with colza oil biodiesel. [•] Binaries mixtures meet ASTM D6751 and EN 14214 requirements of OS values. [Copyright &y& Elsevier]

Abstract: We report the first amperometric method for the simultaneous determination of butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ) in biodiesel using batch-injection analysis (BIA) coupled to pulsed-amperometry. A sequence of potential pulses was selected in order to detect TBHQ and BHA separately in a single injection step at a glassy-carbon electrode. Samples were diluted in 50% v/v hydroethanolic solution with 0.1molL−1 HClO4 (supporting electrolyte) before injection using an electronic pipette. The method is highly precise (RSD<1%, n=10), fast (170 injections h−1), accurate (recovery between 100 and 110%), presents low detection limits (73 and 75nmolL−1 BHA and TBHQ, respectively), and can be easily adapted for on-site determinations. [Copyright &y& Elsevier]

Abstract: This work reports the preparation and characterization of methylic and ethylic biodiesel from cottonseed oil. Biodiesel was prepared by a transesterification process involving the reaction of the oil with methanol or ethanol using KOH as catalyst. The conversion of triglycerides to the corresponding methyl and ethyl ester was 91.5 and 88.5 (wt%). All the physical–chemical properties of the obtained biodiesels met the minimum or maximum limits of the EN 14214 except oxidation stability. The addition of the synthetic antioxidant tert-butylhydroquinone at the concentration of 300mgkg−1 was sufficient to obtain acceptable oxidation stability values (>6h). Thermogravimetric analysis was also performed and similar profiles were verified for both ethylic and methylic biodiesels. Therefore, this work demonstrates the feasibility of using the ethanolic route to produce cottonseed oil biodiesel. [Copyright &y& Elsevier]