protein precipitation

La fabricación de salsas orientales tiene como principal materia prima la soya, además de la utilización de otros aditivos orgánicos, diversos microorganismos y enzimas para las fermentaciones propias de la bioquímica del proceso. Ello genera elevada contaminación orgánica evidenciada en el alto valor promedio de demanda química de oxígeno (DQO) inicial de 1,746 mg/L, mientras que la normativa peruana exige
como máximo 1,000 mg/L de DQO en el vertimiento a la red de alcantarillado. El estudio se centró en métodos de oxidación avanzada
(tecnología de oxidación que genera radicales hidroxilo durante su proceso, sin producir sustancias contaminantes más peligrosas). Se aplicaron cuatro métodos distintos en los que se evalúa la remoción de contaminantes que permite alcanzar niveles de DQO por debajo de los valores máximos admisibles (VMA) de acuerdo a la normativa vigente del Ministerio de Vivienda, Construcción y Saneamiento del Perú.
Luego, se analiza la viabilidad económica, que en el presente estudio está expresada en los costos operativos (OPEX) por el gasto de productos químicos. En base a ella se determina el método más apropiado para proyectar una etapa de pilotaje en planta y confirmar dosis de reactivos químicos, tiempos de retención y variables de operación. En las pruebas de laboratorio se evidenció que la tecnología de tratamiento que mejor se ajusta a los criterios descritos líneas
arriba es la secuencia alcalinización – precipitación de proteínas – coagulación – floculación, seguida de la separación sólido – líquido que consta de clarificación, filtración y adsorción con carbón activado.

Autores: Huguez Ames, Tecsup/ Enrique Cáceres, Tecsup / María Reque, Stockholm Mining/ César Vásquez, Stockholm Mining

In an aqueous electrolyte solution, the potential of mean force for two macroions is affected not only by the size and charge of each electrolyte ion but also by the ion's polarizability. The mean force between two colloidal particles in a saline solution can be calculated by augmenting electrostatic interactions with salt-specific dispersion (van der Waals) interactions between small ions and between small ions and macroions. Results of Monte Carlo simulations are qualitatively consistent with specific-salt effects observed experimentally by numerous investigators, including those of Hofmeister for aqueous proteins over 100 years ago. In agreement with theoretical predictions of Ninham et al., our calculations show that the potential of mean force (and hence the phase behavior of colloidal or protein solution) is sensitive to the van der Waals interaction that depends on salt identity.

An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC-DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic aci...

A simple and sensitive liquid chromatography-tandem mass spectrometric method for quantification of loperamide in human plasma and saliva was developed and validated, and then successfully applied in pharmacokinetic clinical study to investigate and correlate bioavailability of Imodium (R) 2 mg quartet tablet dose in both human plasma and saliva. Loperamide with labeled internal standard was extracted from its biological matrix by methanol as protein direct precipitant in single extraction step. Adequate chromatographic separation for analytes from plasma and saliva matrices was achieved using ACE C18 (50mm x 2.1 mm, 5 mu m) column, eluted by water/methanol/formic acid (30:70:0.1%, v/v), delivered isocratically at constant flow rate of 0.75 ml/min. The method validation intends to investigate specificity, sensitivity, linearity, precision, accuracy, recovery, matrix effect and stability according to European guideline, and partial validation was applied on saliva, specificity, matri...

This study demonstrates the analysis of cimetidine in human plasma with HPLC using a simplified sample preparation by protein precipitation with perchloric acid. Plasma cimetidine concentration was determined by plotting peak height ratio of cimetidine to ranitidine (internal standard, IS) against cimetidine concentrations in plasma. The cimetidine and ranitidine peaks were completely separated and no interference from plasma was observed. The lower limit of quantification (LLOQ) of the method was established at 0.1 microg/mL with a precision of 4.3% and a relative error of 1.9%. The average analytical recovery was >90% over the range of cimetidine concentrations (0.1-15.0 microg/mL). The linearity of calibration curve was excellent (r(2) > 0.999). The within- and between-day precision and accuracy, expressed as the coefficients of variation and relative error, were found to be less than 5%. Compared with previously reported methods, the analytical technique for cimetidine determination in human plasma presented here demonstrates comparable accuracy and precision, an acceptable analysis time, shorter and simpler sample preparation, and a reduced need for complicated equipment. The method presented here is simple and rapid, and the precision and sensitivity are appropriate for the determination of cimetidine in plasma in pharmacokinetic studies.