A Rapid Method for Measurement of Nickel and Chromium at Trace Level in Aqueous Samples
Muhammad Salman,1 Umer Shafique,2* Waheed–uz–Zaman,1 Rabia Rehman,1 Amna Yousaf,1 Faiza Azhar,1 and Jesús M. Anzano3
1 Institute of Chemistry, University of the Punjab, New Campus, Lahore–54590, Pakistan
2 Center for Undergraduate Studies, University of the Punjab, New Campus, Lahore–54590, Pakistan
3 Analithical Chemising, University of Zaragoza, Spain. umer0101@hotmail.com; umer@hons.pu.edu.pk
]]> Received February 18, 2011.
Abstract
A rapid, simple and portable technique to measure Ni(II) and Cr(VI) at trace level in aqueous samples has been proposed. Colored spots were developed by interacting micro–liter drops of metal solutions with suitable reagents on TLC plates. Soon after, TLC having spots was scanned to import the image into the computer. Color densities of spots were calculated with the help of homemade software. Simple regression was practiced on calibration between standards' concentrations and their color densities. For both metals, correlation coefficients were approaching to one, which pointed out a good correlation between color densities and corresponding analyte concentrations. Real samples from electroplating unit were analyzed with the present and conventional spectrophotometric method (employed as reference), and the results were compared to evaluate the pertinence of the proposed technique in the real analysis.
Key words: Chromium, densitometry, image scanning, nickel, spot test quantification.
Resumen
Se ha propuesto una técnica rápida, sencilla y portátil para medir Ni(II) y Cr(VI) a nivel de trazas en muestras acuosas. Puntos de color de los metales se han desarrollado mediante la interacción de microlitros con reactivos adecuados en las placas de cromatografía de capa fina, TLC. Posteriormente se escanea el cromatograma para importar la imagen al ordenador. Se calcularon densidades de color de los puntos con la ayuda de un software realizado en nuestro laboratorio. Una sencilla regresión se utilizó para correlacionar las concentraciones de los estándares y las densidades de color medidas. Para ambos metales, los coeficientes de correlación se acercaban a uno, lo que indicaba una buena correlación entre la densidad del color y las correspondientes concentraciones de analito. Muestras reales provenientes de procesos electroquímicos se analizaron con este método y con el método espectrofotométrico convencional, y se compararon los resultados para evaluar su aplicación en el análisis de muestras reales.
Palabras clave: Cromo, densitometría, escaner, níquel; prueba de cuantification de puntos.
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