Determination of boron content and isotopic composition in gypsum by inductively coupled plasma optical emission spectroscopy and positive thermal ionization mass spectrometry using phase transformation

Curcumin nanoparticle doped starch thin film as a green colorimetric sensor for detection of boron

A tapioca starch film doped with curcumin nanoparticles was successfully fabricated and applied as a novel green colorimetric sensor for detection of boron in wastewater. Curcumin nanoparticles (curn, 30-90 nm) extracted from turmeric powder were used as a green probe, while tapioca starch was used as a natural support substrate. A yellow thin film (51 μm thick) fabricated on a used plastic spoon turned red-brown after immersion in boron solution (pH 9) for 15 min with excellent selectivity. The film costs only 0.0007 USD, while the cost of the sensor (curn-film on new plastic spoon) was 0.004 USD. After use the film could be completely washed from the plastic, it being biodegradable, while the used plastic spoon could be re-used to fabricate a new sensor at least 10 times. The good 1.52%RSD precision was obtained across three lots fabricated. When the curn-film was used in conjunction with digital image colorimetry (DIC), a simple and rapid quantification of boron was achieved. The green color layer in reflected light image of the red-brown product (I_G) provided the highest sensitivity (64 ± 1 a.u. L mg^-1) and the lowest detection limit of 0.052 ± 0.001 mg L^-1. The intra-day testing (9 films) had 2.41 to 4.34%RSD, while the inter-day testing had 2.29 to 5.66%RSD (15 films, 5 days). Accuracy in terms of relative error for control samples (0.40 mg L^-1) was +3.63%. Wastewater samples from Para-rubber wood processing plant were quantified by curn-film and DIC, giving 4248 ± 391 mg L^-1 boron concentration with no significant difference to ICP determination at 95% confidence level. The sensors after storage in a desiccator for a year gave readings changed by only +3.5% and -2.1% relative to freshly prepared sensors.