An experimental procedure is presented that was developed by fifth-year
chemical engineering and industrial chemistry undergraduates at the
Federal University of Rio de Janeiro doing the discipline on Experimental
Organic Technology. The aim of this study was to apply the solvatochromic
effect of the dye Nile Blue chloride to the characterization of biodiesel/diesel
blends with different biodiesel content, using an alternative image
processing analysis method involving low-cost, simple, and rapid assays.
The effect of the solvatochromic dye Nile Blue chloride was monitored
using the software ImageJ, which is being used currently, yielding
rapid and effective responses. As an outcome, the students proposed
a procedure that had potential application to colorimetric determination
of biodiesel content in diesel oil. This gave students the opportunity
to put the knowledge acquired in the course into practice, by dealing
with issues concerning the fuels industry, making the learning process
more dynamic, engaging, and effective.
Biodiesel
content on biodiesel/diesel blends is obtained by determining
the band intensity of CO bond in the fatty acid methyl esters
(FAME) of the biodiesel by mid-infrared spectroscopy (reference method:
EN 14078, 2014). The potential for biodiesel/diesel blends to be adulterated
with vegetable oils constitutes a limitation of the reference method’s
capacity to accurately quantify the biodiesel content in these blends
since vegetable oils, composed primarily of triacylglycerols, also
contain the CO bond. This study employed normal-phase high-performance
liquid chromatography with a refractive index detector (NP-HPLC-RI)
to quantify the biodiesel in biodiesel/diesel blends and detect potential
adulterations of these blends with vegetable oils. Two calibration
curves (4 to 12% vol and 5 to 30% vol) were plotted for the biodiesel
quantification based on which 12 verification samples were analyzed
(samples prepared at different concentrations from the calibration
curves), as well as 20 samples of commercial diesel, acquired at gas
stations in the southeast region of Brazil. The NP-HPLC-RI method
presented good analytical performance in terms of linearity, limit
of detection (LOD), limit of quantification (LOQ), precision (repeatability),
accuracy (recovery), and robustness. Linearity was determined by the
coefficient of determination (R
2) for
concentrations of biodiesel and vegetable oil in diesel varying from
4 to 12% vol (R
2 = 0.9924 and R
2 = 0.9950, respectively) and from 5 to 30%
vol (R
2 = 0.9968 and R
2 = 0.9962, respectively). The LOD and LOQ for the quantification
of the biodiesel were 0.08 and 0.23% vol, while for the quantification
of soybean oil, these values were 0.07 and 0.21% vol, respectively.
The recovery values varied from 97.7 ± 1.8% to 107.1 ± 4.1%,
indicating good accuracy, and the method proved robust when the temperature
was changed from 40 to 35 °C. The paired sample t-test showed the nonexistence of significant differences between
the proposed and reference methods (with 95% confidence), indicating
the capacity of NP-HPLC-RI to detect and quantify biodiesel and vegetable
oil adulterants in samples of diesel both rapidly and effectively,
thereby demonstrating its importance for the quality control of this
fuel since the current methodology (EN 14078) used in several European
Union countries, as well as in Brazil and Argentina, cannot identify
this kind of adulteration and cannot accurately analyze the biodiesel
content in biodiesel/petrodiesel blends.
This work presents the results of the physical characterization of palygorskite and its adsorptive behaviour for three solvatochromic dyes (Nile blue chloride (NBC), methylene blue (MTB) and dithizone (DTZ)). Adsorption isotherms were used to determine the maximum adsorption of the solvatochromic dyes on the palygorskite. The characterization of palygorskite was carried out via mineralogical and chemical analysis with X-ray diffraction, X-ray fluorescence, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, surface-charge measurement (ζ-potential), thermogravimetric analysis, textural analysis and cation-exchange capacity analysis. The material consists of palygorskite and quartz and its chemistry is dominated by SiO2, MgO and Fe2O3. The specific surface area and cation-exchange capacity of the palygorskite are 142 m2 g–1 and 41 cmol(+) kg–1, respectively. The SEM and TEM analyses showed a fibrous structure with fibres 20–100 nm long. The thermogravimetric analysis showed three endothermic events at 57.3°C, 171.8°C and 439.6°C. The adsorption capacities of the palygorskite for NBC (basic pH), MTB (basic pH) and DTZ (neutral pH) were 0.082, 0.013 and 0.102 g g–1, respectively. The adsorptions of NBC and MTB were fitted with the Langmuir isotherm model and the adsorption of DTZ was fitted with the Sips model.
The
aim of this study was to compare two methods for determining
the fatty acid methyl ester content of biodiesel by applying high-performance
liquid chromatography (HPLC-UV) and the reference method based on
gas chromatography (GC). The samples of biodiesel were also analyzed
by 1H NMR. External standards were used for the quantification
of fatty acid methyl esters by HPLC-UV. The analytical curves of the
methyl oleate, methyl linoleate, and methyl linolenate standards showed
good linearity (coefficient of determination ≥ 0.995). Cochran’s
test was used to assess the homoscedasticity of the analytical curves.
The limits of detection and quantitation were found: 0.0018% mass
and 0.0054% mass for methyl oleate, 0.0002% mass and 0.0007% mass
for methyl linoleate, and 0.0001% mass and 0.0004% mass for methyl
linolenate. The accuracy of the HPLC-UV method was assessed by determining
recovery (%), which resulted on values between 81.7 ± 0.2 and
110.9 ± 0.1. Precision was assessed by determining repeatability
(%), which was found to be between 0.2 and 1.3. The proposed HPLC-UV
method proved efficient in determining the fatty acid methyl ester
content of biodiesel and the paired t-test showed
it to correlate well with the reference method (GC).
Gasoline and ethanol fuels have been adulterated with methanol in Brazil. Methanol is not permitted in concentrations greater than 0.5 vol% due its toxicity but its lower price stimulates the adulteration. A new approach for quantitative analysis of methanol in gasoline and ethanol fuels is reported employing high-performance liquid chromatography coupled with refractive index (RI) detector on C18 column (250 × 4.6 mm, 5 µm) using deionized water as mobile phase (0.6 mL min −1 ). The method showed good analytical performance in terms of linearity for methanol concentration ranging from 0.5 to 4.5 vol% (coefficient of determination (R 2 ) = 0.999) and from 4.0 to 12.0 vol% (R 2 = 0.998). The recoveries (accuracy) values ranged from 98.6 to 103.2%. The results indicated that the developed method is accurate and suitable for the determination of methanol in gasoline with ethanol and ethanol fuel as an alternative procedure to gas chromatography (GC)-based techniques.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.