Features and New Examples of Gas Chromatographic Separation of Thermally Unstable Analytes

The processes of thermal decomposition of analytes in gas chromatographic (GC) columns are classified and two new examples of them are considered in details. First of them is monomolecular decomposition of monoalkyl esters of benzene-1, 2-dicarboxylic (phthalic) acid (monoalkyl phthalates). This process has the analogy in chemical reactions in solutions and it may be responsible for the toxicity of phthalates. The second example is decomposition of non-substituted hydrazones of both aliphatic and aromatic carbonyl compounds. The analytes of the second sub-group present the first example of bimolecular (second order) decomposition in a GC column: two molecules of hydrazones form stable azines and hydrazine. Besides that this process presents the particular interest, because it is accompanied by secondary chemical reactions not in an injector, but within GC column, when a by-product of decomposition is involved into secondary interaction with other constituents of the samples. It was confirmed, that visual images of all these decomposition processes on the chromatograms are rather identical and coincide with the manifestations of interconversion of isomers or tautomers. The most often expressed features of chromatographic profiles in such cases are the presence of peaks of an initial analyte and a product of its decomposition or isomerization, connected with more or less expressed diffused “plateau” or “train” between them. The decomposition processes during sample preparation prior to chromatographic separation or in the heated injector of GC instrument are not accompanied by such features. Despite of the rather “exotic” character of the examples considered, the knowledge of them seems to be useful for better revealing the analogous situations in chromatographic practice. Thermal instability of analytes is the principal restriction of GC separation of reactive compounds and we cannot eliminate it for objective reasons. However, in some cases we can evaluate the temperature limits of chromatographic columns, which should not be exceeded during GC separation of instable compounds. The simplest (low boiling) homologs of thermally unstable compounds are often characterized by “normal” boiling point at atmospheric pressure (T b, °C) without decomposition, that means the possibility of their GC analysis unambiguously. Therefore, we can select such T b values as GC and/or GC–MS temperature limit (T lim) for other members of series of thermally unstable homologs. If GC separation is carried out not in isothermal, but in temperature programming conditions, so-called retention temperature (T R) of unstable analytes should not exceed the evaluated T lim value.

TIME, ENERGY EFFICIENCY IN THE PRODUCTION OF BIODIESEL, AND PRODUCTS DESTINATION IN A BIOREFINERY

This manuscript deals with the production of biodiesel from triglycerides (TG); soybean oil was the primary raw material. The transesterification reaction was used to convert triglycerides into monoalkyl esters. The catalytic mixture of methanol and potassium hydroxide (KOH) was used in the transesterification reaction. The anhydrous refining of biodiesel was used to reduce side reactions during the purification process. The treatment of glycerol by acidification with H3PO4 and its subsequent purification was a convenience process aiming to form the desired byproducts. The conversion of residual fatty acids to soaps through the saponification reaction or into esters through the esterification reaction with H2SO4 can be done by observing the market of those products. The monitoring of the transesterification reaction in real-time with laser spectroscopy allows the variation of the temperature during the reaction process without losing the reaction endpoint. The use of only one reaction vessel for the accomplishment of several unit operations aiming the reducing of the reaction time in the production process was well succeeded. The main resulting products are biodiesel, glycerol, fertilizer, and soaps. As expected the biodiesel can be used as a source of energy, the glycerol can be further refined but this process was not explored at this manuscript, the resulting salts can be used as fertilizers, and the soups can be sold and used as a soup.

Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite

We achieved the synthesis of important medronic acid monoalkyl esters via the dealkylation of mixed trimethyl monoalkyl esters of medronic acid. Two methods were developed for the purification of medronic acid monoesters: 1) small scale (10–20 mg) purification by using hydroxyapatite and 2) large scale (tested up to 140 mg) purification by high-performance countercurrent chromatography (HPCCC).

The Effects of Alkaline Catalysts in Used Frying Oil Biodiesel on the Diesel Engine Performances

The biodiesel, defined as monoalkyl esters from waste vegetable oils are being produced widely as a viable alternative diesel fuels due to its lower cost, largest producer and reduces the disposal problem. In this study, the effects of catalyst formulation on biodiesel yield are evaluated by using three different alkaline catalyst; sodium hydroxide (NaOH), potassium hydroxide (KOH) and sodium methoxide (NaOCH3) with methanol via transesterification process and are tested in a four cylinder Mitsubishi Pajero 2.5cc Intercooler Turbo Diesel Engine. The engine emissions and performance were recorded under partial load within the range of 1000 to 3500 rpm of the biodiesel (B100) fuels compared with the diesel fuel. The best yield percentage was obtained using NaOCH3 as catalyst whilst KOH is the most convenient and simpler in process. NaOH was found to be more superior than the other two catalysts in terms of lower cost production and low engine emission.

Application of Methylphosphonic Acid Monoalkyl Esters to the Extraction of Some Metals

The distribution between aqueous nitric acid and benzene was examined for methylphosphonic acid monoalkyl esters where the alkyl was a methyl, propyl, butyl, isobutyl, pentyl, 2-methylbutyl, cyclohexyl or 1,2,2-trimethylpropyl group. The extraction of complexes of these reagents with Ag, Co, Zn, Sc, Yb, Eu and Hf was also investigated. The esters do not dimerize in benzene. The pKa and KD values of the reagents and the corresponding extraction constants were determined. Derivatives containing five and more carbon atoms in the alkyl groups were found practically applicable to the extraction.