Abstract
A simple potentiometric sensor is described for accurate, precise, and rapid determination of sulfite additives in beverages. The sensor is based on the use of cobalt phthalocyanine as a recognition material, dispersed in a plasticized poly(vinyl chloride) matrix membrane. o-Nitrophenyl octyl ether (o-NPOE) as a membrane solvent and tri-dodecylmethyl- ammonium chloride (TDMAC) as ion discriminators are used as membrane additives. Under the optimized conditions, sulfite ion is accurately and precisely measured under batch and flow injection modes of analysis. The sensor exhibits fast and linear response for 1.0 × 10−2–1.0 × 10−6 M (800–0.08 µg/mL) and 1.0 × 10−1–5.0 × 10−5 M (8000–4 µg/mL) sulfite with Nernstian slopes of −27.4 ± 0.3 and −23.7 ± 0.6 mV/concentration decade under static and hydrodynamic modes of operation, respectively. Results in good agreement with the standard iodometric method are obtained.Validation of the assay method is examined in details including precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty and good performance characteristics of the method are obtained. The sensor response is stable over the pH range of 5 to 7 without any significant interference from most common anions. The advantages offered by the proposed sensor (i.e., wide range of assay, high accuracy and precision, low detection limit, reasonable selectivity, long term response stability, fast response, and long life span and absence of any sample pretreatment steps) suggest its use in the quality control/quality assurance routine tests in beverages industries, toxicological laboratories and by inspection authorities.
Highlights
Sulfite ions have been widely used for centuries as preservative for food, beverages, and pharmaceutical products [1,2]
Cobalt phthalocyanine was completely insoluble in aqueous solutions but readily dissolves in dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and dioxane solvents, displaying absorption spectrum in the visible region with two maxima
Of 13 showed good25,dissolution properties and long-term color stability of cobalt phthalocyanine. 3The absorption spectrum of Co (II)-phthalocyanine in DMSO solution displayed two absorption peaks at of cobalt phthalocyanine in tetrahydrofuran and dioxane were unstable because the absorbance at these showed good and 666 nm dissolution (Figure 1). properties and long-term color stability of cobalt phthalocyanine
Summary
Sulfite ions have been widely used for centuries as preservative for food, beverages, and pharmaceutical products [1,2]. The Food and Drug Administration, USFDA, has established 10 ppm as the threshold for declaration of sulfite in the labeling of food, non-alcoholic beverages, and wine products [4,5]. The development of a sensitive, selective, fast, and cost effective method for the determination of sulfite is very important and highly demanded for food quality control and quality assurance. Spectrofluorimetric methods for the determination of sulfite include the use of tetra-substituted amino aluminum phthalocyanine [9] rhodamine B hydrazide [10], and N-(9-acridinyl) maleimide (NAM) [11].
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