Photographic Detection of Cadmium(II) and Zinc(II) Ions

Design and optimization of a single-use optical sensor based on a polymer inclusion membrane for zinc determination in drinks, food supplement and foot health care products

A single-use optical sensor was designed for Zn(II) determination based on the immobilisation of the colorimetric reagent 2-acetylpyridine benzoylhydrazone (2-APBH) in a polymer inclusion membrane (PIM) adhered on the surface of an inert rectangular strip of polyester (Mylar). Different components for the membrane preparation were tested and those resulting in membrane with good appearance, proper physical and optical properties and ease of preparation were selected. Factorial design 23 with three replicates of the central point was applied for the optimisation of the membrane composition. The optimal composition consisted of 2.5 g of poly(vinyl chloride) (PVC), 4 mL of tributyl phosphate (TBP) and 0.04 g of 2-APBH. The optode showed a linear dynamic range from 0.03 (detection limit) to 1 mg L-1 of Zn(II) ions with a response time of 30 min in aqueous solution at pH 6 and a relative standard deviation of 3.90% for 0.4 mg L-1 of Zn(II). The sensor exhibited good selectivity to Zn(II) over other commonly ions. It was successfully applied to the determination of Zn(II) in a water certified reference material, spiked tap water, vitamin-mineral drink, food supplement and foot health care products, as contribution to the concern about this heavy metal due to its significant role in many biological and physiological processes although toxicant at high doses.

Determination of Zn2+ and Cd2+ by glassy carbon electrode modified with Perilla frutescens activated carbon

A Perilla frutescens (L.) Britton activated carbon that had high specific surface area (HSAPFAC) was modified on the surface of the glassy carbon electrode (GCE) for preparing a HSAPFAC/GCE, and on this basis, a differential pulse voltammetry (DPV) method for the simultaneous determination of zinc and cadmium ions (Zn2+ and Cd2+) was developed by using HSAPFAC/GCE. The determination conditions such as the film thickness, deposition potential, deposition time, and electrolyte acidity were investigated. The amperometric determination was carried out in a NaAc–HAc buffer solution (0.1 mol L−1, pH 5.5) after enriching for 550 s at –1.3 V. The oxidation peaks appear at –1.160 V and –0.845 V for Zn2+ and Cd2+, respectively. The oxidation peak currents of Zn2+ and Cd2+ are proportional to their concentrations in the ranges of 0.5 ∼ 20 μg L−1 and 0.25 ∼ 10 μg L−1, with the detection limits of 0.15 μg L−1 and 0.01 μg L−1 (signal/noise (S/N) = 3). The proposed method was applied to the determination of Zn2+ and Cd2+ in tap water samples. The recoveries were 101.6%∼103.0% and 84.0%∼88.8%, respectively.

N2S2 pyridinophane-based fluorescent chemosensors for selective optical detection of Cd2+ in soils

A fluorescent sensor array for the quantitative determination of Cd²⁺ in soils based on two N₂S₂ pyridinophane chemosensors is presented.

A Fluorescent Sensor Array Based on Heteroatomic Macrocyclic Fluorophores for the Detection of Polluting Species in Natural Water Samples

The development of a novel all-solid-state optical sensor array based on heteroatomic macrocyclic fluorophores (diaza-crown ether, metallocorrole and pyridinophans) for the photographic analysis of liquid media, is presented. The sensitivity of the new optical system toward a number of different species (cations: Li⁺, K⁺, Na⁺, NH4+, Mg²⁺, Ca²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and anions: NO2-, NO3-, Cl⁻, Br⁻, HCO3-) was evaluated both in single selective sensor mode and in multisensory arrangement. The satisfactory PLS1 regression models between sensor array optical response and analyte concentration were obtained for Cd²⁺, Cu²⁺, Zn²⁺, and NO2- ions in all the range of tested concentrations. Among these species the highest attention was focused onto detection of cadmium and nitrite ions, for which the detection limits, DL, estimated by 3σ method were found 0.0013 mg/L and 0.21 mg/L respectively, and these values are lower than the corresponding WHO guideline values of 0.003 mg/L (Cd²⁺) and 2 mg/L (NO2-). The suitability of the developed sensors implemented with familiar devices for signal acquisition (Light Emitting Diode, LED, as light source and a digital camera as a signal detector), and chemometric methods for data treatment to perform fast and low-cost monitoring of species under interest, in real samples of environmental importance, is demonstrated.