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  • Development of a polydimethylsiloxane-thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples.

Development of a polydimethylsiloxane-thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples.

The Science of the total environment (2014-08-13)
M C Prieto-Blanco, N Jornet-Martínez, Y Moliner-Martínez, C Molins-Legua, R Herráez-Hernández, J Verdú Andrés, P Campins-Falcó
ABSTRACT

This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery composite sensor for direct monitoring of ammonium in environmental water samples. The sensor is based on a PDMS support that contains the Berthelot's reaction reagents. To prepare the PDMS-thymol/nitroprusside composite discs, thymol and nitroprusside have been encapsulated in the PDMS matrix, forming a reagent release support which significantly simplifies the analytical measurements, since it avoids the need to prepare derivatizing reagents and sample handling is reduced to the sampling step. When, the PDMS-thymol/nitroprusside composite was introduced in water samples spontaneous release of the chromophore and catalyst was produced, and the derivatization reaction took place to form the indothymol blue. Thus, qualitative analysis of NH4(+) could be carried out by visual inspection, but also, it can be quantified by measuring the absorbance at 690 nm. These portable devices provided good sensitivity (LOD<0.4 mg L(-1)) and reproducibility (RSD <10%) for the rapid detection of ammonium. The PDMS-NH4(+) sensor has been successfully applied to determine ammonium in water samples and in the aqueous extracts of particulate matter PM10 samples. Moreover, the reliability of the method for qualitative analysis has been demonstrated. Finally, the advantages of the PDMS-NH4(+) sensor have been examined by comparing some analytical and complementary characteristics with the properties of well-established ammonium determination methods.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium nitroferricyanide(III) dihydrate, ACS reagent, ≥99%
Sigma-Aldrich
Silicone oil, viscosity 60,000 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 100 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 350 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 50 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 20 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 500 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 100,000 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 1,000 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 10 cSt (25 °C)
Sigma-Aldrich
Silicone oil, viscosity 10,000 cSt (25 °C)
Sigma-Aldrich
Silicone oil, for oil baths (from −50°C to +200°C)
Silicone oil, for melting point and boiling point apparatuses
Sigma-Aldrich
Thymol, FCC, FG
Sigma-Aldrich
Silicone oil, viscosity 30,000 cSt (25 °C)
Thymol, European Pharmacopoeia (EP) Reference Standard
Supelco
Thymol, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Thymol, meets analytical specification of Ph. Eur., BP, NF, 99-101%
Sigma-Aldrich
Sodium nitroprusside dihydrate, puriss. p.a., ACS reagent, reag. Ph. Eur., ≥99%
Sigma-Aldrich
Thymol, ≥98.5%
Sigma-Aldrich
Silicone oil, viscosity 5 cSt (25 °C)
Supelco
Thymol, analytical standard
Supelco
Sodium Nitroprusside, Pharmaceutical Secondary Standard; Certified Reference Material
Silicone oil, European Pharmacopoeia (EP) Reference Standard