Method for organic fluorine determination in gasoline and its components using high-resolution continuum source flame molecular absorption spectrometry with gallium fluoride as a target molecule.

Organic fluorides can arise due to the usage of HF in technologies of gasoline production, therefore, it is necessary to identify contamination of gasoline or its components with organic fluorine. For this aim, simple and fast method is proposed. The method relies on sample dilution in xylene, followed by the solution aspiration to a high-resolution continuous source spectrometer for measurement of absorption of radiation by GaF molecule, arisen in air-acetylene flame. Gallium(III) acetylacetonate is carefully dissolved and introduced to all measured solutions at Ga concentration 5000 mg L-1. For standard addition calibration three types of samples solutions are prepared to contain: none, 50 mg L-1 and 100 mg L-1 of added fluorine. As fluorine standard 2, 2, 3, 3, 4, 4, 4-heptafluoro-1-pentanol is applied. The lowest possible flow rate of acetylene is recommended. The solution flow rate and the additional air flow rate should be adjusted to obtain not-disturbed baseline. The overlap of the GaF signal with residual signal of the OH molecule can be overcome using least square background correction. Five pixels are recommended for signal evaluation at the most sensitive 211.248 nm rotational "line". Using such conditions characteristic concentration was 3.2 mg L-1. Detection limit recalculated for initial sample was 4-10 mg L-1.•High-resolution continuum source flame molecular absorption spectrometry turned out to be an excellent tool for determination of pollution of gasoline with organic fluorine.•Due to application of GaF as a target molecule, it is possible to use a low-temperature and easy for operation air-acetylene flame.•The proposed method can be applied for analysis of alkylate, reformate, isomerizate, ethanol as well as commercial automotive and aviation gasoline.

Method development for determination of organic fluorine in gasoline and its components using high-resolution continuum source flame molecular absorption spectrometry with gallium fluoride as a target molecule.

High-resolution continuum source molecular absorption spectrometry (HR-CS MAS) has been developing fast for fluorine determination, but neither flame nor graphite furnace technique have ever been applied for the analysis of petroleum or its products. Hydrogen fluoride can be applied in technologies of gasoline components production, unfortunately, arising organic fluorides can contaminate final product. The aim of this work was development of fast and simple HR-CS MAS method, with an ordinary air-acetylene flame, for determination of organic F in gasoline and its components. Gallium fluoride as a target molecule was the imposing choice, because Ga undergoes atomization at relatively low temperature, and the GaF molecule is known to provide good sensitivity in F determination. Severe difficulties have arisen to get higher concentration of gallium (as Ga(III)acetylacetonate) in the measured (xylene) solution. Furthermore, depending on the flame character, the spectrum of the GaF molecule at the most sensitive 211.248 nm rotational "line"could have been disturbed by intensive noise (a case of too rich flame) or overlapped by the OH molecule spectrum (a case of too lean flame). The effects, as well as sensitivity of F determination, depended on the sample volatility and its dilution ratio. The difficulties have been overcome by adjusting the solution aspiration rate and the additional air flow rate to get not-disturbed baseline. The least square background correction (LSBC) with the OH molecule spectrum as the correction spectrum (the OH molecule spectrum intentionally generated for the first time) and the standard addition calibration have been also applied. Huge difference in sensitivity, up to one order of magnitude, depending on the F compound volatility and its chemical character was stated. A standard giving the best sensitivity (heptafluorobutanol) turned out to be the most suitable for calibration in analysis of real samples (satisfactory agreement with results of combustion ion chromatography). It was found that HF introduced into the solution of the investigated sample does not contribute to the increase of F signal. Using 5000 mg L-1 of Ga in a solution, the best characteristic concentration and detection limit are 3.2 mg L-1 and 0.93 mg L-1, respectively. The developed method enabled to identify high contamination of some gasoline components with organic F species, which constituted significant corrosion and environmental threat.

pH dependence of daunorubicin interactions with model DMPC:Cholesterol membranes.

Mixed monolayers composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC):Cholesterol 7:3 prepared by the Langmuir-Blodgett method were used as model membranes to investigate the influence of the anticancer drug daunorubicin (DNR) on the properties of the lipid membrane. The Langmuir monolayer experiments revealed that drug - membrane interactions are pH-dependent. The changes in monolayer organization at subphases of pH 7.4 containing daunorubicin visualized by Brewster Angle Microscopy showed that in the presence of the drug the typical morphology observed for phospholipid layers containing cholesterol was no longer seen. It supports the explanation of the mechanism of the drug incorporation into the layers in terms of the competition between DNR molecules and cholesterol in the layer. Increasing surface pressure with time and increasing value of limiting surface pressure with increasing drug concentration in the subphase confirmed incorporation of the drug into the membranes. The interactions between the lipid monolayer and the drug at pH 5.4 were of electrostatic nature between the negative part of the DMPC molecule and positively charged drug, while at pH 7.4 contribution of interactions of daunorubicin with cholesterol was observed. Large differences of the surface-pressure vs. time plots were observed at both pH values when the DMPC:Cholesterol monolayer was not well organized yet. The voltammograms recorded for DMPC:Cholesterol monolayers transferred from the air-water interface onto gold electrode confirmed the presence of the drug in the lipid layer. Based on the charge of the oxidation-reduction peaks corresponding to the redox processes of quinone-hydroquinone group in daunorubicin, the initial surface concentration of the drug in the membrane and the drug release profile to the solution were evaluated.