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. 2020 Jul 6;25(13):3076.
doi: 10.3390/molecules25133076.

A New Validated Potentiometric Method for Sulfite Assay in Beverages Using Cobalt(II) Phthalocyanine as a Sensory Recognition Element

Saad S M Hassan  1 , Ayman H Kamel  1 , Abd El-Galil E Amr  2   3 , Hisham S M Abd-Rabboh  4 , Mohamed A Al-Omar  2 , Elsayed A Elsayed  5   6
Affiliations

A New Validated Potentiometric Method for Sulfite Assay in Beverages Using Cobalt(II) Phthalocyanine as a Sensory Recognition Element

Saad S M Hassan et al. Molecules. .

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.

Keywords: beverages; flow injection analysis; method validation; potentiometry; sulfite measurements; sulfite sensor.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Absorption spectra of sulfite calibrants in the range of 2 × 10−4 to 1 × 10−3 M after the addition of 1 mL of 0.1 mg/mL CoPC in DMSO.
Figure 2
Figure 2
Ligation of sulfite ion to Co(II)-phthalocyanine complex.
Figure 3
Figure 3
Calibration plot of sulfite ion using [CoPC/TDMA+/o-NPOE] PVC membrane-based sulfite sensor in a mixture of 10−2 M acetate buffer of pH 5 and 10−3 M NaCl as a background solution.
Figure 4
Figure 4
Effect of pH on the potentiometric response of [CoPC/TDMA+/o-NPOE] PVC membrane based sulfite sensor using 10−3 M sulfite solution.
Figure 5
Figure 5
Potentiometric FIA chart for sulfite calibrants using [CoPC/TDMA+/o-NPOE] PVC membrane.
Figure 6
Figure 6
Flow-injection setup: (1) NaCl-acetate buffer reservoir, (2) peristaltic pump, (3) injection valve, (4) cell assembly, (5) double junction reference electrode, (6) high (Z) box, (7) typical flow-transient plot.
See this image and copyright information in PMC

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