Novel Approach to Sample Preconcentration by Solvent Evaporation in Flow Analysis

Abstract

A preconcentration module operated in flow mode and integrated with a sequential injection system with spectrophotometric detection was developed. Using the system, preconcentration was performed in continuous mode and was based on a membraneless evaporation process under diminished pressure. The parameters of the proposed system were optimized and the system was tested on the example of the spectrophotometric determination of Cr(III). The preconcentration effectiveness was determined using the signal enhancement factor. In the optimized conditions for Cr(III), it was possible to obtain the signal enhancement factors of around 10 (SD: 0.9, n = 4) and determine Cr(III) with precision and intermediate precision of 8.4 and 5.1% (CV), respectively. Depending on the initial sample volume, signal enhancement factor values of about 20 were achieved. Applicability of the developed preconcentration system was verified in combination with the capillary electrophoresis method with spectrophotometric detection on the example of determination of Zn in certified reference materials of drinking water and wastewater. Taking into account the enhancement factor of 10, a detection limit of 0.025 mg L−1 was obtained for Zn determination. Zn was determined with precision less than 6% (CV) and the results were consistent with the certified values.

Comprehensive Assessment of Flow and Other Analytical Methods Dedicated to the Determination of Zinc in Water

“…Instrumental operation conditions and materials of the SIA-CE/DAD, SP, DPASV, FIA-DAD, FIA-SF, FIA-ICP/MS methods were exactly described in [ 14 , 17 , 18 , 19 , 20 , 21 ]. The evaluation of the FAAS and ICP/OES methods was performed in our laboratory on the basis of the procedures dedicated to the determination of zinc in natural water [ 15 , 16 ] under the following instrumental conditions: FAAS spectrometer PinAAcle 900 AA (Perkin Elmer, Inc, Shelton, CT, USA) equipped with hollow cathode lamp (Beijing Vacuum Electronics Research Institute, Beijing, China) with operating current 9.0 mA, wavelength 213.86 nm, slit/width of 2.7/1.8 nm, sample aspiration rate 5.0 mL/min and acetylene and air flow 2.5 and 10.0 L/min, respectively; ICP/OES spectrometer Optima 2100 DV (Perkin Elmer, Inc, USA) working with 1300 W plasma power and with plasma, auxiliary and nebulizing gas flows of 15.0, 0.2 and 0.80 L/min, peaks for wavelength 206,200 nm in axial plasma view mode were measured for sample flow rate 1.50 mL/min.…”

“…Eight spectrometric and electrochemical analytical methods were selected for the study, differing from each other in terms of the sample preparation procedure and the type of detection system [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. In four methods, the samples were processed and delivered to the detecting unit using dedicated flow systems [ 14 , 19 , 20 , 21 ]. Flow techniques, thanks to their natural properties, obviously favor the GAC rules, including increasing work safety, reducing the consumption of reagents and waste production, as well as allowing easy adaptation of green sample processing modules and energy-saving measuring instruments [ 22 , 23 ].…”

A Perspective of the Comprehensive and Objective Assessment of Analytical Methods Including the Greenness and Functionality Criteria: Application to the Determination of Zinc in Aqueous Samples

“…The subject of the assessment were arbitrarily selected methods for determining zinc in water: spectrophotometric with diode array detection (DAD), fluorimetric, differential pulse voltametric, stripping potentiometric, flame atomic absorption spectrometric (FAAS), inductively coupled plasma optical emission spectrometric (ICP-OES), inductively coupled plasma mas spectrometric (ICP-MS) and electrophoretic. These methods included procedures used routinely at the Department of Analytical Chemistry of the Jagiellonian University, as well as published in scientific literature ( Compañó et al, 1996 ; Azubel et al, 1999 ; Tarley et al, 2009 ; Lagerström et al, 2013 ; Lu et al, 2017 ; Paluch et al, 2020 ) Some of them were realized in the flow mode (fluorimetric, DAD, ICP-MS and electrophoretic).…”

Recent (2018–2020) development in capillary electrophoresis

“…Analyte cleanup and preconcentration designs not relying on electrophoresis and chromatography have been reported as well. For example, a membraneless evaporation process with diminished pressure was proposed by Paluch et al, allowing for sample preconcentration in a continuous mode [29]. This novel system could be used for preconcentration with different starting sample volumes, which was employed to determine the content of Zn in both drinking and waste water using CE-UV with an LOD of 0.025 mg/L.…”