ABSTRACT
An optical assay for the rapid determination and chemical speciation of Fe2+/Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ â¼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within â¼5 min, an acceptable limit of detection (0.1 µg mL-1) and linear dynamic range (1 - 100 µg mL-1) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2. The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+/Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.
ABSTRACT
The present article reports the application of hexamethylsilazane (HMDS) modified filter paper for ultrasensitive detection of Hg(2+), Co(2+) and Zn(2+). By chemical vapor deposition of HMDS, a highly hydrophilic filter paper was fabricated to a low wetting (hydrophobic) substrate. The water contact angle (θ) of modified paper was â¼128°, whereas scanning electron and atomic force microscopy confirmed the surface modification. Using chromogenic reagents, a one-step assay for aforementioned ions was demonstrated onto pristine as well as hydrophobic paper. The assay was completed in less than 10 min and the end-result was in form of a color change that could be easily read by the naked eye. The limit of detection on modified paper was 0.5 ppb, which was 5-order of magnitude superior to that observed on pristine paper. The proposed method was successfully applied for semi-quantitative determination of Hg(2+) ions in real wastewater samples.
ABSTRACT
The antibacterial and antioxidant properties of 30 selected honey samples produced in Saudi Arabia have been studied. The inhibitory action of the total phenolic content of the honey samples has been tested against Staphylococcus aureus, Micrococcus luteus and Escherichia coli. The MIC values of the ten selected honey samples against S. aureus, M. luteus and E. coli were in the range 0.5 ± 0.2 - 3.6 ± 0.3; 0.45 ± 0.05 - 5.0 ± 0.6 and 0.6 ± 0.2 - 4.4 ± 0.4 mg mL(- 1). The antioxidant activities of the ethyl acetate extracts based on their anti-radical power using the 1,1-diphenyl-2-picrylhydrazyl scavenging assay and their ferric reducing antioxidant power were in the ranges 50.78 ± 1.4% to 99.52 ± 0.2% and 0.85 ± 0.13 to 1.167 ± 0.13 mg/ml, respectively. The total phenolic content was in the range 84.97 ± 0.57 to 317.39 ± 0.76 mg/100 g.
