Preconcentration PHASED

A solid -phase preconcentration system was implemented. Several chemical and flow-related parameters potentially influencing the enrichment factor were studied, of which only three were revealed to be significant... 

Arslan Z. and Paulson A. J. (2002) Analysis of biogenic carbonates by inductively coupled plasma-mass spectroscopy (ICP-MS). Flow injection on-hne sohd-phase preconcentration for trace element determination in fish otohths. Anal. Bioanal. Chem. 372,116—7S5. 

M. Miro, W. Frenzel, V. Cerda, J.M. Estela, Determination of ultra traces of nitrite by solid-phase preconcentration using a novel flow-through spectrophotometric optrode, Anal. Chim. Acta 437 (2001) 55. 

In the analysis of natural waters Speer et al. (1986) discuss the influence of salt content on the reliability of results. Li et al. (1996) determined Co, Cu, Mn, Fe, V, Ti and Mn in waters after third phase preconcentration and reach detection limits of 0.02-0.6 p,g/cm (the reported recovery is 95-100%). Analysis of standard reference materials produced by national Research Council Canada SRLS-3 (river water) and NASS-3 (sea water) proved the reliable determination of V, Mn and Cu in river water and Mo in sea water. For the rest of the elements sensitivity was not good enough (Li et al., 1996). Very good accuracy has been obtained in the determination of Ca, Co, Cu, Fe, Mn and Zn (Ebdon et al., 1987). 

Li, X.J., Schramel, P., Wang, H.Z., Grill, P., Kettrup, A., 1996. Determination of trace metal ions Co, Cu, Mo, Mn, Fe, Ti, V in reference seawater samples by inductively coupled plasma emission spectrometry combined with third phase preconcentration. Fresenius Z. Anal. Chem. 356, 52-56. 

On the other hand, ID requires the interference free measurement of two isotopes for accurate quantification. In case of Pd, the necessity for matrix elimination is even more evident if ID-MS is used. The accurate determination of Pd in soil and road dust by ID-ICP-MS employing multi-stage sample pretreatment including microwave digestion, matrix elimination by cation exchange and solid phase preconcentration, has been described (Rudolph et al. 2006). 

Bonneil, E. and Waldron, K. C., On-line solid-phase preconcentration for sensitivity enhancement in capillary electrophoresis. J. Capill. Electrophor. Microchip TechnoL, 6, 61, 1999. 

Rodriguez, R., Pied, Y, Font, G., and Manes, J., Determination of urea-derived pesticides in fruits and vegetables by solid-phase preconcentration and capillary electrophoresis. Electrophoresis, 22, 2010, 2001. 

Liquid-liquid extraction (LLE) is among the oldest sample extraction and preconcentration techniques available in analytical chemistry. LLE is a method whereby two immiscible phases, generahy an organic solvent and an aqueous solution, are brought into contact in order to extract one or more analytes from one phase into the other. If the receiving phase has a smaller volume than the donor phase, preconcentration can be effected. The separation mechanism is, like SPE, based on partitioning. At equilibrium, the partition coefficient of analyte i (Ki) in a two-phase system is given by... 

In a related study, the ionization chemistry of 2,4,6-TCA was described for the atmospheric pressure gas phase ion source with an IMS. The ion of greatest intensity in positive polarity was a protonated monomer ion with reduced mobility values K of 1.58 cmWs minor amounts of a proton-bound dimer at K of 1.20 cmWs were reported. In negative polarity, two product ions were tentatively assigned identities as a trichlorophenoxide with K = 1.64 cm /Vs and chloride attachment adducts of a TCA Kg = 1.48 and 1.13 cmWs for MCE and M2CF, respectively. The limit of detection for 2,4,6-TCA dissolved in dichloromethane and deposited on a filter paper was 2.1 pg, or 1.7 ppm in the gas phase. Preconcentration and preseparation were recommended for actual wine samples. 

Another strategy to avoid packing beads in a microfluidic device is in situ polymerization of a porous monolithic stationary phase. Svec et al. [5] have formed monolithic columns in microfluidic chips by using methacrylate chemistry to form reversed phase or ion exchange stationary phases. Preconcentration was used to increase the concentration of GFP by a factor of 10. Another advantage to this technique lies in the ability to control the porosity of the monolith. The ability to control the porosity decreased the back pressure allowing for flow rates as high as 10 pl/min. 

FAAS >75 pgr Acid digestion/solid-phase preconcentration... 

Zhang, H. Stoeckli, M. Andren, P.E. Caprioli, R.M. Combining solid-phase preconcentration, capillary electrophoresis and off-line matrix-assisted laser desorption/ioniza-tion mass spectrometry intracerebral metabolic processing of peptide E in vivo. J. Mass Spectrom. 1999, 34 (4), 377-3S3. 

In addition, computers have increased the flexibility of analytical systems by allowing a number of operations mimicking those performed manually. Samples can be aspirated and mixed with a reagent their mixture driven to a photoreactor and an aliquot withdrawn, sent to a solid-phase preconcentration unit and eluted from it with a view to sequentially detecting the analytes by using several detectors that can be arranged serially at the same port or radially at different ports or even in a serial/radial mixed configuration. 

M. Mir6, W. Frenzel, V. Cerda, J.M. Estela, Determination of ultratraces of nitrite by solid-phase preconcentration using a novel flow-through spectrophotometric optrode. Anal. Chim. Acta 437 (2001) 55—65. M. Mir6, W. Frenzel, J.M. Estela, V. Cerda, A novel flow-through disk-based solid-phase extraction diffuse reflectance optrode. Application to preconcentration and determination of trace levels of nitrite. Analyst 126 (2001) 1740-1746. 

A technique for solid-phase preconcentration of contaminants dissolved in surface waters has been presented in Ref. [70]. The method is based on application of extraction... 

Disposable immunosensors for the determination of bacteria based on screen-printed platforms have been also reported in the literature. Afonso et al. (2013) fabricated a screen-printed carbon-based biosensor in combination with magnetic separation for the rapid detection of Salmonella in milk samples. Magnetic beads coated with anti-Salmonella antibodies (MBs-pSAb) and modified AuNPs coated with polyclonal anti-Salmonella antibody were used as the capture phase (preconcentrating step) and electrochemical labels, respectively. The modified magnetic beads were then captured onto the electrode surface by applying a magnetic field below the printed sensors and analysed electrochemically by DPV. 

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