title: A novel approach to Lab-In-Syringe Head-Space Single-Drop Microextraction and on-drop sensing of ammonia.
abstract: A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, is proposed which utilizes a secondary inlet into the syringe void, used as a size-adaptable reaction chamber, via a channel passing through the syringe piston. This innovative approach allows straightforward automation of head-space single-drop microextraction, involving accurately controlled drop formation and handling, and the possibility of on-drop analyte quantification. The syringe was used in upside-down orientation and in-syringe magnetic stirring was carried out, which allowed homogenous mixing of solutions, promotion of head-space analyte enrichment, and efficient syringe cleaning. The superior performance of the newly developed system was illustrated with the development of a sensitive method for total ammonia determination in surface waters. It is based on head-space extraction of ammonia into a single drop of bromothymol blue indicator created inside the syringe at the orifice of the syringe piston channel and on-drop sensing of the color change via fiber optics. The slope of the linear relationship between absorbance and time was used as the analytical signal. Drop formation and performance of on-drop monitoring was further studied with rhodamine B solution to give a better understanding of the system's performance. A repeatability of 6% RSD at 10 μmol L(-1) NH3, a linear range of up to 25 μmol L(-1) NH3, and a limit of detection of 1.8 μmol L(-1) NH3 were achieved. Study of interferences proved the high robustness of the method towards humic acids, high sample salinity, and the presence of detergents, thus demonstrating the method superiority compared to the state-of-the-art gas-diffusion methods. A mean analyte recovery of 101.8% was found in analyzing spiked environmental water samples.
authors: Department of Analytical Chemistry, Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, Hradec Králové, 500 05, Czech Republic; School of Chemistry, The University of Melbourne, Parkville, Victoria, 3100, Australia.
authors: Ivana
authors: I
authors: Šrámková
authors: Department of Analytical Chemistry, Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, Hradec Králové, 500 05, Czech Republic; School of Chemistry, The University of Melbourne, Parkville, Victoria, 3100, Australia. Electronic address: Horstkob@faf.cuni.cz.
authors: Burkhard
authors: B
authors: Horstkotte
authors: Department of Analytical Chemistry, Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, Hradec Králové, 500 05, Czech Republic.
authors: Hana
authors: H
authors: Sklenářová
authors: Department of Analytical Chemistry, Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, Hradec Králové, 500 05, Czech Republic.
authors: Petr
authors: P
authors: Solich
authors: School of Chemistry, The University of Melbourne, Parkville, Victoria, 3100, Australia.
authors: Spas D
authors: SD
authors: Kolev
keywords: Ammonia; Automation of sample preparation; Bromothymol blue indicator; Head-space Single-Drop Microextraction; Kinetic on-drop sensing; Lab-In-Syringe