Iranian Journal of Chemistry and Chemical Engineering
Volume:24 Issue: 1, Jan-Feb 2005

Low molecular weight organic acids are most predominant in apple juice among these components fumaric acid was not exceed more than 5 ppm. It was thought that the HPLC is the best method of the determination of organic acids in the apple juice. In this study, chromatographic separation of organic acids of apple juice was obtained by preparing a sample and by applying them to acid phase for extraction and various organic acids content of apple juice, fumaric acid, oxalic acid, tartaric acid and shikimic acids were commented as qualitative and quantitative, too. The organic acids, of which the chromatographic separations were examined, were the acids of fumaric acid, oxalic acid, tartaric acid, ascorbic acid, lactic acid, malic acid, succinic acid and shikimic acid. For this separation, the suitable value are determined by regulating the pH of mobile phase with phosphoric acid in range of pKa ±1.5 (This is the space in which the capacity factors are effectively changed). The concentration of juice was distilled to 11.2 Brix and same pH was applied to cartridge by adjusting with the phosphate buffer at 8.00, and the cartridge was washed with the same buffer and the phase was combined with the first eluant. A suitable distilled percentage of samples were injected and injection volume were determined. In this study, the cartridges of Supelco C18 and Waters C18 were used, datas obtained by both types of cartridges were compared. In this study, the methods of external calibration and added method of standards were applied and slopes were compared.

At many circumstances، in heat exchange processes several exchangers were used with different cost laws due to their pressure ratings، materials of construction and exchange3r types. In such circumstances traditional methods of pinch technology can not be led to minimum total annual cost may cause some other disadvantages like more complexity or higher maintenance. In this research work a new approach based on decomposition has been used to achieve the cost-effective networks with multiple cost laws. The cost laws multiplicity can has several reasons. The most common cases are; mixed pressure ratings، mixed types and mixed materials of construction however many other factors such as purchasing exchangers from different vendors or purchasing exchangers in different times can also cause multiplicity cost laws. The present paper demonstrates application of two decomposition methodologies (Total decomposition and Partial decomposition) for a few sample conditions with typical cost laws. The outcomes of this study indicate effectiveness and potentiality of the methods.

Vapor-liquid equilibrium in NH3-CO2-H2O system at high pressures has been studied. The UNIQUAC-NRF model for this system was extended by using the Goppert 4 maurer reported datas. Since the system contains molecules and ionic species the binary interaction parameters considered, where those are of molecule-molecule, molecule-ion and ion-ion types. These interaction parameters are taken as constant values in UNIQUAC-NRF, which are not accurate. In this work the mentioned parameters have been considered as function of temperature in quadratic form. By applying an optimization mathematical program to the UNIQUAC-NRF model and experimental data reported by Goppert and Maurer the model parameters were obtained in term of temperature. The results of this model with the new parameters show good agreement with experimental data.

Crystallization of Aluminum fluoride at atmospheric pressure has been considered. Structure, size and shape of crystals formed during the crystallization process have been investigated. By applying the direct analysis method for the existed aluminum in solution, the aluminum fluoride nucleation process has been detected as a concentration valley at the outset of crystallization process. The linear rate of growth of aluminum fluoride crystals has been measured by taking SEM micrographs from crystals during crystallization process. The rate of crystal growth in longitudinal direction is about 10-9 m/s and nearly six times more than the rate of crystal growth in side direction. It is indicated that the aluminum fluoride nucleation process is repeated after completion of growth of initial crystals.

Many modern analytical methods deal with the trace-level determination of compounds of interest in highly complex environmental samples by means of chromatographic techniques. The introduction of a “clean” sample into an analytical instrument can make analyses easier and prolongs the equipment life. The use of solid-phase extraction (SPE) has grown and is a fertile technique of sample preparation as it provides better results than those produced by liquid-liquid extraction (LLE). The application of SPE can give selectivity of extraction providing a purified and concentrated extract. Through this study, optimization of trace enrichment and sample clean-up method via the use of bonded silica cartridges is discussed. SPE using bonded silica has been optimized with respect of sample pH, sample concentration, elution solvent strength, sample volume, and elution volume. In this investigation a variety of non-polar sorbent cartridges were also screened. During this study, the octadecyl bonded silica cartridge (C18) has proven successful in simplifying sample preparation. The present approach proved that 2,4-D could be retained on C18 based on specific interaction. Further study employed methanol to extract the analyte from spiked water and gave a clean sample for high pressure liquid chromatography equipped with ultra violet detection system. The optimized method was validated with three different pools of spiked samples and showed good reproducibility over six consecutive days as well as six within-day experiments.

Two different growth media, namely complex and defined media, were used to examine establishment of steady-state conditions in phosphate-limited culture system of Saccharomyces cerevisiae CEN. PK113 - 5D strain. Using the defined growth medium, it was possible to obtain steady state condition in the continuous culture. The effect of phosphate concentration on the growth of S. cerevisiae in phosphate-limited chemostat was studied at dilution rates between 0.08-0.45 h–1. The cells growth followed Monod kinetics only over low dilution rates (0.08-0.22 h–1) in which the saturation constant (KS) and maximum growth rate (μm) were determined as 10 µM and 0.25 h–1, respectively. By increasing the dilution rates above 0.22 h–1, a significant change in the growth pattern was occurred, possibly due to intracellular accumulation of phosphate and/or extracellular accumulation of ethanol and also increased fermentative activity of the yeast cells. Phosphate transport of the yeast cells via plasma membrane transporters was kinetically characterized in a phosphate-limited chemostat culture. The rate of phosphate transport was measured using 32[P]-labeled orthophosphate in the concentration range of 0.4-2000 µM. High-affinity phosphate transport kinetics was observed over the entire range of dilution rates tested in this study. The corresponding Km values for phosphate were found to be in the range of 1.7 to 36 µM. Dilution rate of 0.22 h–1 showed biphasic pattern for phosphate uptake kinetics while the estimated Km values for this behavior were 1.7 and 284 µM.

In this article the methodology proposed by Li and Wang for mixed qualitative and quantitative modeling and simulation of temporal behavior of processing unit is reexamined and extended to more complex case. The main issue of their approach considers the multivariate statistics of principal component analysis (PCA), along with clustered fuzzy digraphs and reasoning. The PCA and fuzzy clustering provide tools to categorize the quantitative dynamic trends, describing the temporal behavior of joint human-process interactions qualitatively, and through the proposed neuro-fuzzy reasoning the system responses can be obtained when the system is exposed to uncertain disturbances. First, the method is applied to a continuous stirred tank reactor – CSTR and then to a distillation column to demonstrate the accuracy level and capability of the approach to handle more complex processes

A rapid isocratic method of high performance liquid chromatography system (HPLC) with a glassy carbon working electrode of electrochemical detector is set up for quantitative detection of trace amount of nitrite ion (NO2¯) in aqueous protein containing cell lysate, cell media, plasma, serum, urine and other body fluids. The solid extraction reversed phase cartridges (Sep-pak) are used for deproteinizing and purification of the samples. Nitrite ion is the only stable end product of autoxidation of nitric oxide (NO); which is a highly reactive paramagnetic molecule produced via the enzymatic conversion of L-arginine to L-citroline. The enzyme involved in this process is the inducible nitric oxide synthase (iNOS), the main isoform of the enzymes in macrophage and macrophage like cell lines such as Raw-264, J774, and Ic-21. Nitrite ion (NO2¯) in nanomolar concentration range is measured by the ECD detector with an amperometric cell, applied voltage of + 800 mV and Ag-AgCl as the reference electrode. Elusion buffer is 8 mM ammonium chloride containing 25% methanol, flow rate of 1 ml/min and column temperature set at 20° C. The reproducibility of sample preparation and analysis had a coefficient of variance (c.v.) less than 10 % in the cell lysates and cell media of the Tib-186 cell lines. Therefore, this will be a reliable analytical method for the nitrite ion analysis under various conditions of cytokines, LPS, irradiation, or other chemical applications for evaluation of the probable over expression of the inducible nitric oxide synthase (iNOS) gene in these type of cells.