Electrode-analytical properties of polyvinylchloride membranes based on triple metal-polymeric complexes

Abstract

The influence of the nature of the electrode-active substances (EAS), the composition of the external and internal solutions on the formation of the analytical signal of polyvinylchloride (PVC) membranes based on associates and triple metal-polymeric complexes (TMPC) was established. Dehumidification of synthesized membranes increases with the content of polyvinylpyrrolidone (PVP). The value of the swelling degree is more than two times greater for membranes, which contain as EAS TMPC, relative to membranes based on associates. The value of water absorption of membranes is determined by the nature of EAS. They formed a series of increasing of the swelling degree such as associate < background membrane < TMPC. Swelling of the background membrane is explained by the physical sorption of water molecules on the surface of plasticized membrane. Hydration of PVP macromolecules varies with the introduction of metal ions, macromolecules unit undergoes a conformational transition. PVP macromolecules form tunnels or cavities where complex particles distributed and additional water accumulated through the second coordination layer. Constructed sensors based on TMPC have slope of electrode function equal to 25 mV/pC. Linear dependence of potential on the polymer concentration is observed in the range of 5–7 pC units. Sensors based on associates have slope of the electrode function of 20–25 mV/pC that can be varied depending on the nature of the EAS. Working range is 4–8 pC. Response time of sensor is less than 1 min. The optimal time for conditioning of the synthesized PVC membrane is 24 hours. Potentiometric sensors have been developed for the determination of residual amounts of low molecular PVP which is a food additive E 1201 commonly used for thickening, stabilizing and clarifying of food products. The content of PVP was determined in real objects (apple juice, beer, red wine and cognac) with using the polyvinylpyrrolidone sensors (Sr < 0.08). The advantages of the proposed technique of direct potentiometric determination of food additives E-1201 are following: the low limit of detection (1·10‒8 M), rapidity (2–5 min) and the absence of complex stages of sample preparation. Developed potentiometric sensors can be used in laboratories for food control, in particular, alcoholic and soft drinks, the content of the food additive such as E-1201.

Keywords

• triple metal-polymeric complex
• polyvinylpyrrolidone
• apple juice
• beer
• wine
• brandy