Microscale laboratory has been widely used in General Chemistry mainly in Synthetic Chemistry (inorganic and organic chemistry). Analytical Chemistry approaches just concern to titrimetric determinations with acid-base indicators using 5 mL pipets as burets to teach semi quantitative analysis aspects. Teaching Analytical Chemistry requires to focus in quality aspects such as accuracy and precision. This latter is the most affected when microscale conditions are assayed: “to microtechniques, macroerrors”. However if good experimental practices are observed these errors can be controlled and minimized to yield an adequate and good experimental teaching experience.

In this work we show that results obtained with low cost equipment with locally materials are equivalent to those obtained in macroscale conventional conditions respect to precision parameters assayed. Volumetric titrations results are shown monitored by colored chemical indicators or instrumentally (micropotentiometry or conductimetry).

Microscale laboratory has been widely used in General Chemistry mainly in Synthetic Chemistry (inorganic and organic chemistry). Analytical Chemistry approaches just concern to titrimetric determinations with acid-base indicators using 5 mL pipets as burets to teach semi quantitative analysis aspects. Instrumental measurements play a very important role in teaching analytical methodologies. Chemical Instrumentation has been developed mainly for basic or applied research so it is difficult to access to such devices in teaching laboratories. In our laboratory we have developed low cost equipment with locally materials to performe potentiometric, conductimetric, electrochemical and photocolorimetric measurements to teach Instrumental Analytical Chemistry (1-4).

Two "home-made" microburets built with low cost materials are presented including integrated magnetic stirrer and support to show their use in titrimetric analysis with visual indication. Normalization of HCl 0.01 mol/L with previous normalized NaOH titrant solution yields an average end point volume of 0.5600 mL with a standard deviation of 0.05800 (1.03% relative std. dev.). Results obtained with 25 and 10 mL burets are compaired with 1 and 2 mL "home-made" microburets.  

In this work a low cost home-made micropotentiometric cell is built based on a W° pH microsensor and Cu|Cu(II)|H2O|| cuasireference microelectrode. A linear Nikolsy type response is obtained, E = 54.89 mV - 49.79 pH; r² = 0.9889. E=f(volume) and its corresponding pH=(volume) plots are shown for standard solutions.  

En este trabajo se presentan los resultados obtenidos en la fabricación de microburetas microelectrodos, microceldas, microagitadores, microconductímetros, micropolarógrafos y microfotocolorímetros, todos ellos fabricados con material de bajo costo para trabajar con volúmenes de 1 mL < V <5 mL. Se muestran las curvas de calibración respectivas (r²>0.99) para microbiosensores, fotocolorimetría y amperometría, y las curvas de valoración acidobase, redox, complejometricas, precipitación y conductimétricas con estándares y muestras. Los resultados han sido probados durante 4 años con estudiantes regulares, en cursos nacionales de microescala así como en el extranjero (Cuba, Uruguay, Chile) con resultados satisfactorios.

El siguiente trabajo se realiza en el contexto de la microescala química. Se muestran curvas de titulación micropotenciométrica pH =f(volumen NaOH 0.1063mol L ^-1 ) usando dos microsensores de pH, polianilina (PANI) y W/WO₃ contra un microlectrodo de referencia Cu/Cu⁺². Los datos de potencial son registrados con un sensor de voltaje y asistidos computacionalmente usando el software Data Studio (DS). El punto de equivalencia se obtiene aplicando la primera y segunda derivada con herramientas del DS.

Para validar los resultados obtenidos se comparan con curvas de titulación usando un sensor de pH en base de membrana de vidrio, las que son similares a las curvas de titulación micropotenciométricas obtenidas.

En este trabajo se proponen tres prototipos de Microfotocolorímetros de Mínima Instrumentación construidos con materiales de bajo costo y de alta precisión para la cuantificación de Ácido Acetilsalicílico en tabletas de Aspirina^®; además se presentan las gráficas de Ringbom para la determinación del intervalo de concentraciones de trabajo, las curvas ponderadas para demostrar la precisión y reproducibilidad de los datos obtenidos y los datos estadísticos para la comparación de los resultados obtenidos entre los tres prototipos de MIMC’s y los obtenidos con un espectrofotómetro convencional.

In this work a low cost home-made micropotentiometric cell is built based on a Ag microsensor and Cu^°|Cu(II)|H₂O|| cuasireference microelectrode both integrated directly to a microcell. No saline bridge is not necesary. Potentiometrically ending point volumes are obtained in the cuantification of chloride alone and in mixture with bromide and iodide as well.