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Plackett-Burman and Quarter fraction 2 5−2 factorial designs were applied to evaluate a spectrophotometric flow injection method in order to determine phenol in water by using 4-aminoantipyrine (4-aap) as derivatizing reagent. With a minimum number of experi- ments, the designs enabled the best conditions for phenol analysis: 80 cm and 180 cm reactors; flow-rates being: NH3 1.0 mL min −1 ; 4-aap 0.35 mL min −1 and K3(Fe(CN)6) 0.35 mL min −1 , (NH3) 0.064 mol L −1 , (4-aap) 9.84 × 10 −3 mol L −1 , (K3(Fe(CN)6)) 0.02 mol L −1 , and an injection volume of 200 µL. With the optimized method it was possible to increase the lineal range from 0.3 µg mL −1 to 30 µg mL −1 and also to quantify the maximum allowable phenol concentration in water in comparison with other standard and flow injection methods whose lineal range are from 0.5 µg mL −1 to 20 µg mL −1 and from 0.5 µg mL −1 to 16 µg mL −1 , respectively. The detection limit was of 0.13 µg mL −1 and the regression coefficient was of 0.9999, making possible a throughput of 36 determinations an hour with a minimum consume of reagent. With the proposed method, a distillation step was not necessary to remove sulfates but, when the sulfate:phenol ratio was higher than 83, the analytical signal for phenol increased 8%, but hypochlorite interfered with the signal when the hypochlorite:phenol ratio was higher than 1. Resumen. Se utilizaron disenos factoriales Plackett-Burman y frac- cionado 2 5−2 para evaluar un metodo espectrofotometrico de inyec- cion en flujo con el objetivo de determinar fenol en agua utilizando 4-aminoantipirina (4-aap) como reactivo derivatizante. Los disenos establecieron, con la menor cantidad de experimentos, las mejores condiciones para el analisis de fenol fueron: reactores de 80 cm y 180 cm; caudales para NH3 de 1.0 mL min −1 ; para 4-aap de 0.35 mL min −1 y para K3(Fe(CN)6) de 0.35 mL min −1 ; las concentraciones optimas fueron NH3 0.064 mol L −1 , 4-aap 9.84 × 10 −3 mol L −1 y K3(Fe(CN)6) 0.02 mol L −1 con un volumen de inyeccion de 200 µL. El metodo una vez optimizado permitio incrementar el intervalo lineal de 0.3 µg mL −1 a 30 µg mL −1 en comparacion con otros metodos estandar y de flujo continuo cuyos intervalos lineales son de 0.5 µg mL −1 a 20 µg mL −1 y de 0.5 µg mL −1 a 16 µg mL −1 , respectivamente. El limite de detec- cion fue 0.13 µg mL −1 y el coeficiente de regresion 0.9999, con una frecuencia de muestreo de 36 determinaciones por hora y un minimo consumo de reactivos. Con el metodo propuesto no fue necesario un paso de destilacion para remover sulfatos pero cuando la proporcion de sulfato:fenol fue mayor a 83 la senal analitica para fenol incremento 8%. El hipoclorito interfirio en la cuantificacion de fenoles cuando la proporcion hipoclorito:fenol fue mayor a 1. Palabras clave: Diseno factorial Plackett-Burman, fenol, 4-aminoan- tipirina, agua, inyeccion en flujo,espectrofotometria.

journal of the mexican chemical society

Plackett-Burman Factorial Design for the Optimization of a Spectrophotometric Flow Injection Method for Phenol Determination in Tap and Bottled Water Using 4-Aminoantipyrine