Continuous system with microwave irradiation to obtain alkyl benzoates.

In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group (ROH) with benzoyl chloride (BC) is carried out in an on-line system with UV detection. All reaction conditions, as flow rate (FR), ROH/BC molar ratio, wavelength, temperature, microwave (MW) irradiation and reaction coil size (internal diameter and length) were optimized. 0.5mLmin(-1), 2.49 [BC]/[ROH], 230nm, 60 degrees C or medium power (225W) when MW irradiation was used and a reactor coil of 159muL (0.5mmx810mm) were the optimum conditions. The on-line system with microwave irradiation was more efficient than the one with a water bath heating. The developed system reduces analysis time consumption, reagent amounts and this system was used to evaluate the composition of commercial samples of alcohols polyethoxylated (surfactants).

Efecto de alcoholes lipofílicos en el reparto de surfactantes nonilfenol polietoxilados en sistemas aceite/microemulsión/agua / Effect of lipophilic alcohols in the partitioning of nonylphenol polyethoxylated surfactants in oil/microemulsion/water systems

El comportamiento de fases en un sistema surfactante-agua-aceite se afecta por las llamadas variables de formulación, por ejemplo, por la naturaleza de los componentes o su ambiente fisicoquímico. Una de estas variables es la presencia del tipo y concentración de alcohol en el sistema. Para estudiar este efecto se realizaron barridos de formulación variando el número de óxido de etileno (EON) del sistema, por medio de la mezcla de un surfactante lipofílico con otro hidrofílico con el fin de hallar el sistema de máxima solubilidad (Winsor III óptimo) e incorporar en este sistema los alcoholes a diferentes concentraciones para observar el cambio de transición. El reparto se determinó por cromatografía líquida de alta resolución (HPLC). La adición de alcoholes lineales lipofílicos a estos sistemas proporciona mayor polaridad a la fase oleica y por ende mayor fraccionamiento hacia la misma. Se encontró que si la cadena alquílica del co-surfactante está por encima de un número de átomos de carbono promedio del alcohol (ACAN, acrónimo del inglés “alcohol carbon atom number”) igual a 4,5 el 50 por ciento del fraccionamiento no se ve afectado por el incremento de la concentración ni por el tipo de alcohol lipofílico.

Phase behavior in surfactant-water-oil systems is affected by the so-called formulation variables, for example, thenature of the components or their physiochemical environment. One of these variables is the presence of the type and concentration of the alcohol in the systems. The formulation scan varying the ethylene oxide number (EON) of the system were carried out, by means of the mixture of a lypophilic surfactant with another hydrophylic with the purpose of finding the maximum solubility system (Winsor III optimum) and to incorporate in this system the different alcohols with different concentrations to observe the transition change. The partititon coefficient was determined by high performance liquid cromatografic (HPLC). The addition of lineal lipophilics alcohols to these systems provides more polarity to the oil phase in consequence more fractionation towards it same one. It was found that if the alkyl chain of the co-surfactant is above an ACAN (alcohol atom carbon number) equal to 4,5 the 50 percent of fractionation is not affected by the increment of the concentration neither for the type of alcohol.

Determination of aliphatic alcohols after on-line microwave-assisted derivatization by liquid chromatography-photodiode array detection.

In this study, high-performance liquid chromatography (HPLC) in conjunction with continuous derivatization for the determination of aliphatic and polyethoxylated alcohol is reported. Reaction of alcohol group with phenyl isocyanate or benzyl chloride reagents assisted with microwaves (MW) irradiation is carried out in an on-line system coupled to HPLC with photodiode array detection (PDA). Reactor was placed into a microwave oven at 450W. The flow rate, reagent amounts, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the system MW-HPLC-PDA provided high sensitivity, reduce the amount of reagents and analysis time. This proposed method can be used for the analysis of commercial alcohol polyethoxylated mixture.

Developing an on-line derivatization of FAs by microwave irradiation coupled to HPLC separation with UV detection.

The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water-microemulsion-oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet-violet (UV-Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV-Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW-HPLC-UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water-microemulsion-oil systems, to quantify the total acid fraction in each phase.