Metal ions detection

For a complex-forming metal ion detectable by its own metal electrode, e.g. in the titration of Cu2+ with EDTA by means of a Cu electeode and a double junction calomel electrode, p/ curves are obtained of a nature comparable to those in Fig. 2.20 and with a Cu range of about 20 (cf., stability constant... 

Heavy metal ions detection with porphyrin in sol-gel is possible, too56. The porphyrin, used for detection of heavy metal ions (Hg2+, Pb2+, Cd2+), was 5,10,15,20-tetra(4-N-methylpyridil)porphyrin (TMPyP) preferred to other porphyrins because it was not leaked out of the matrix. The study of metallation of the porphyrin immobilized in sol-gel emphasized the formation of 1 1 complex for each ion with a constant of complexation depending on the nature of the ions. The strongest effects were observed for mercury due to the specific interaction of this metal with the porphyrin. 

Delmarre D., Meallet R., Bied-Charreton C., Pansu R., Heavy metal ions detection in solution, in sol-eel and with grafted porphyrin monolayers, J. Photochem. Photobiol. A 1999 124 23-28. 

In addition to metal ions, detection of halides such as fluoride is important, as the latter is often present in nerve gases and nuclear weapons manufacture. Our group utilized the unique reactivities of F with Si to specifically sense for fluoride ions [30]. PArE 35 was constructed with a masked precursor to a flu-... 

An alternative and often facile route to appropriately functionalised ICPs, that avoids the synthetic problems outlined in (ii) above, is the use of sulfonated species containing the desired molecular recognition/receptor site as the dopant anion for the conducting polymer chains. For example, calixarene-containing polypyrroles [34] and polyanilines [35] for selective metal ion detection have recently been prepared via the use of sulfonated calixarenes as dopant anions. We have similarly found that the incorporation of metal complexing agents such as sulfonated 8-hydroxyquinoline as dopants in polypyrroles provides a simple route to metal ion-selective ICPs [36]. 

Hartkopf, A., Delumyea, R. Use of the luminol reaction for metal ion detection in liquid-chromatography. And. Lett 7, 79 (1974)... 

To overcome the problem of detection in CE, many workers have used inductively coupled plasma-mass spectrometry (ICP-MS) as the method of detection. " Electrochemical detection in CE includes conductivity, amperometry, and potentiometry detection. The detection limit of amperometric detectors has been reported to be up to 10 M. A special design of the conductivity cell has been described by many workers. The pulsed-amperometric and cyclic voltametry waveforms, as well as multi step waveforms, have been used as detection systems for various pollutants. Potentiometric detection in CE was first introduced in 1991 and was further developed by various workers.8-Hydroxyquino-line-5-sulfonic acid and lumogallion exhibit fluorescent properties and, hence, have been used for metal ion detection in CE by fluorescence detectors.Over-... 

In order to enhance or modify the chemical selectivity of an SERS substrate, it is possible to chemically derivatize the metal surface. For example, covalent bonding of a hydrocarbon to a silver island film should selectively adsorb nonpolar analytes from an aqueous solution. The general approach is shown schematically in Figure 13.24 for the case of metal ions detected by a surface-bound complexing agent (47). Field enhancement is provided by the substrate, while adsorption selectivity results from the chemistry of the derivatized... 

Procedure 7.1.b Designing Experiments to Investigate the Use of HQS as a Fluorimetric Reagent for Metal Ion Detection... 

The metal complexes of Eriochrome Black T are generally red, as is H2ln . Thus, for metal ion detection, it is necessary to adjust the pH to 7 or above so that the blue form of the species, HIn , predominates in the absence of a metal ion. Until the equivalence point in a titration, the indicator complexes the excess metal ion so that the solution is red. With the first slight excess of EDTA, the solution turns blue as a consequence of the reaction... 

In similar experiments, Lin et al. [82] covalently attached glucose oxidase (GOx) to the exposed CNT end in a NEA and demonstrated that a hnear amper-ometric response can be obtained from 0.08 to 30 mM of glucose. Both the linear range and detection limit surpass other studies. The same group also demonstrated that the inlaid CNF NEA can be used for heavy metal ion detection. Trace Cd(II) and Pb(II) were deposited onto a bismuth-coated CNF NEA and then measured with stripping voltammetry. The detection limit was as low as 0.04 p.g/L (40 ppt) [83,84]. 

Metal ions. Chitosan is known to complex metal ions. The chelating ability of chitosan is superior compared to other known biopolymers [30]. This property is widely investigated for its use as sensors or filtration materials in heavy metal ion detection or separation [17, 20a, 31]. The binding of chitosan with metal ions is thought to provide donor atoms that may improve the antimicrobial activity of the material however, studies on this area are quite limited [32]. 

Selective behavior monitors specific toxicity and employs enzyme inhibition tests and reporter genes tests. Examples, are use of cholinesterase for organophosphates and urease for heavy metal ions detection and also transgenic microorganism for specific analyte assessment. 

Metal Ions Detection Using DNA-Modified Gold Nanoparticles, 424... 

Bargossi, C. Fiorini. M.C. Montalti. M. Prodi. L. Zaccheroni, N. Recent developments in transition metal ion detection by luminescent chemosensors. Coord. Chem. Rev. 2000. 208. 17-32. 

While detection of cations via porphyrin-ba.sed materials has been explored less than anion sensing, the ability of a porphyrin to coordinate different metals and the unique spectral signatures that result form the basis for metal ion detection. Use of free-base porphyrins in polymer matrices has allowed for the detection of heavy metal ions by Ache et Immobilization of 5,10,15,20-tetrakis(4-N-methylpyridyOporphyrin on Nafion membranes pennitted detection of cadmium and mercury in solution with detection limits of 5 X 10 M and 2 x 10 M, respectively over a 20-minute measuring period. The method is subject to interferences from other metal ions, but the researchers were able to detect several ions simultaneously using pattern-recognition techniques such as principal component analysis. Sol-gel films doped with 5,l0,l5,20-tetra(p-sulfonatophenyDporphyrin have also been used by Ache and coworkers for the fluorimetric determination of mercury in solution, with a detection limit of approximately 7 X 10... 

Scheme 5.1 Fc functionalized macrocyUcs for metal ion detection, crown ethers 1 [2], cryptands 2 [3,4], closed aza-oxa crown 2 [2], cylams 4 [3], open aza-oxa 5 [3]...

Figure 6.1 Metal ion detection at monolayer interface, a the direct electrochemical method with HS-CA-Gly-Gly-His detects Cu2+ in the sub-ppt limit [12]. b Ion gated channel method based on Fe(CN)63-/4- at a glutathione monolayer interface with a detection limit of about 1 mM La3+ [16-18]...

Scheme 6.1 Third generation TTF crown of metal ion detection...

Table 1 Comparison of metal ion detection limits with different chemiluminescence systems. All ions have detection limits of lOnmoll" or lower. Ions in bold type have detection limits of lOnmoll" or lower. Only first-row transition-metal species are considered...

Metal ion Detection limit (ng) Metal ion Detection limit (ng)... 

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