An optical sensing film was fabricated for sensitive determination of zinc ion in aqueous solutions. The optical sensor was prepared by synthesized ionophore, 5-Br salophen, dioctyl sebacate (DOS) as a plasticizer, sodium tetraphenyl borate (NaTPB) as a lipophilic anionic additive in a poly(vinyl chloride) membrane. The optode response is based on the cation-exchange membrane and indicated a significant absorbance signal change on the exposure to Britton-Robinson buffer solution of pH 5.7 containing Zn2+ ion. The proposed sensor showed a linear range of 4.9 × 10-5-4.5 × 10-12 mol L-1 with a limit of detection of 3.9 × 10-12 mol L-1. Furthermore, satisfactory analytical sensing characteristics including selectivity, stability, and reproducibility for the determination of zinc ion were obtained. The response time of the sensing film was less than 5 min, depending on the concentration of Zn2+ ions. The proposed sensor was successfully applied for determination of zinc in tap water, river water, and sea water.

Homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) was investigated for the extraction of molybdenum from the water samples. Alizarin Red S and cetyl trimethylammonium bromide (CTAB) were used as a complexing ligand and ion-pairing reagent, respectively. The enriched analyte in the floated organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). In this work, low density organic solvent was used and no centrifugation was required in this procedure. A special extraction cell was designed to facilitate the collection of the low-density extraction solvent. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Under the optimum conditions, the method performance was studied in terms of linear dynamic range (0.5-200 µg L-1), linearity (r2 > 0.991), precision (repeatability < 10.0 %). Also, the limit of detection (LOD) of 0.1 µg L-1 was obtained for molybdenum. The proposed method has been successfully applied for the determination of the molybdenum in water samples.

In this study, a simple and efficient ultrasound-assisted emulsification microextraction (USAEME) method combined with gas chromatography (GC) was developed for the preconcentration and determination of oxadiazon in water and soil samples. In this method, fine droplets of toluene were formed and dispersed in the sample with the help of ultrasonic waves which accelerated the formation of a fine cloudy solution without using disperser solvents. Several factors influencing the extraction efficiency, such as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation time, were investigated and optimized. Using optimum extraction conditions a detection limit of 0.1 μg L-1 and a good linearity in a calibration range of 0.25-250 μg L-1 were achieved for the analyte in a river water sample. This proposed method was successfully applied to the analysis of oxadiazon in water and soil samples.