Determination of metal ions

Masina, M. R. Nkosi, P. A. Rasmussen, P. W. et al. Determination of Metal Ions in Pineapple Juice and Effluent of a Emit Canning Industry, /. Chem. Educ. 1989, 66, 342-343. 

The main idea of research is application of accessible, simple and express methods that don t need expensive reagent techniques for analysis of phanuaceutical products based on bischofite. The determination of metal ions such as Mg, Zn, Cu, Fe by complex-formation titrations using a widely applicable chelating agent, EDTA, have been studied as a function of pH, complexing agents and indicators. The analysis consists of four parts ... 

The polarographic determination of metal ions such as Al3 + which are readily hydrolysed can present problems in aqueous solution, but these can often be overcome by the use of non-aqueous solvents. Typical non-aqueous solvents, with appropriate supporting electrolytes shown in parentheses, include acetic acid (CH3C02Na), acetonitrile (LiC104), dimethylformamide (tetrabutyl-ammonium perchlorate), methanol (KCN or KOH), and pyridine (tetraethyl-ammonium perchlorate), In these media a platinum micro-electrode is employed in place of the dropping mercury electrode. 

Fluorimetry is generally used if there is no colorimetric method sufficiently sensitive or selective for the substance to be determined. In inorganic analysis the most frequent applications are for the determination of metal ions as fluorescent organic complexes. Many of the complexes of oxine fluoresce strongly aluminium, zinc, magnesium, and gallium are sometimes determined at low concentrations by this method. Aluminium forms fluorescent complexes with the dyestuff eriochrome blue black RC (pontachrome blue black R), whilst beryllium forms a fluorescent complex with quinizarin. 

Dieker et al.67 used a similar method but applied a dropping amalgam electrode (DAE) and followed amperometrically by means of pulse polarography the anodic dissolution wave of mercury in the presence of an excess of ligand by appropriate choices of pH and titrant they achieved selective determinations of metal ions at low concentrations. 

In the determination of metal ions in animal faeces, digestion with 12% perchloric and 56% nitric acids was in progress when an explosion occurred. This was attributed to one of the samples going to dryness on a sand tray heater. 

Several metal ions play a crucial role in biological processes, whereas some others are toxic. Alteration of the metal concentration in the body can often be correlated to disease states. The necessity for in vivo determination of metal ion concentration and distribution has prompted research to develop appropriate metal-responsive MRI contrast agents. 

The scope of CAR-CLS in analytical determinations has been expanded with one other type of CL reaction (luminol-based CL reactions are restricted to direct determinations of metal ions and some indirect ones). The so-called energy transfer CL is one interesting alternative, with a high analytical potential. As stated above, PO-CL systems based on the reaction between an oxalate ester and hydrogen peroxide in the presence of a suitable fluorophore (whether native or derivatized) and an alkaline catalyst are prominent examples of energy transfer CL. This technique has proved a powerful tool for the sensitive (and occasionally selective) determination of fluorophores its implementation via the CAR technique is discussed in detail later. 

The voltammetric determination of metal ions in the presence of particles are in principle able to differentiate without prefiltering the water sample between dissolved and labile species, i.e., the metal ions electrochemically available within the diffusion layer and (in addition to other non-labile complexes) those bound to particles and colloids (Gongalves et al., 1985, 1987). 

The potential applications of NIR OFCD determination of metal ions are numerous. The detection of metal contaminants can be accomplished in real-time by using a portable fiber optical metal sensor (OFMD). Metal probe applications developed in the laboratory can be directly transferred to portable environmental applications with minimal effort. The response time of the NIR probe is comparable to its visible counterparts and is much faster than the traditional methods of metal analysis such as atomic absorption spectroscopy, polarography, and ion chromatography. With the use of OFMD results can be monitored on-site resulting in a significant reduction in labor cost and analysis time. 

Dithizone is used for analytical extractions, for colorimetric determinations of metal ions, and for removing traces of metals from aqueous buffers. 

C. Yi, D. Huang, and M. Gratzl, Complexometric Determination of Metal Ions by Microscopic Diffusional Titration, Anal. Chem. 1996, 68,... 

The use of azo salts for the complexometric and colorimetric determination of metal ions has been well established. For silver(I), complexes from a wide range of reagents have been... 

A wide variety of methods has been used in studies of oligomerization reactions. The most important quantitative method is potentiometric measurement of pH as a function of the total metal concentration and of the concentration of the analytical excess of acid or base. Other quantitative methods which are often used are potentiometric determination of metal ion concentration, calorimetry, spectrophotometry, and ion exchange. These, together with a number of other techniques, have recently been discussed thoroughly by Baes (22). 

Hydroxyquinoline (oxine, 6), one of the earliest analytical reagents, also is one of the most widely studied N—O bidentates. Its early coordination chemistry was reviewed by Phillips.19 Its use as an in vivo agent in microbiological systems has been reviewed by Schulman and Dwyer.20 The extensive use of oxine and substituted forms, and closely related bidentates, for the analytical solvent extraction and colorimeteric determination of metal ions has been comprehensively reviewed.21 An unusual bridged bonding mode for oxine has been reported in which N monodentate and O... 

The technique of voltammetric stripping analysis is one of the most sensitive techniques available for the determination of metal ions in complex sample matrices. Traditionally such techniques have been undertaken at Hg electrodes, but in recent years, a large number of reports have focused on the use of SPCEs in this area. Reports prior to 2003 have been reviewed recently by the present authors [3]. 

The determination of metal ions using peptide-modified electrodes... 

Several metal ions are essential or beneficial to life while others, such as lead, cadmium or mercury, are highly detrimental. Many diseases have been associated in a way or another to altered metal ion concentrations in the body. Deficiencies can be as damaging as overloads. Copper deficiency has been associated to anemia while excess copper can lead to Wilson s disease (liver cirrhosis). Anemia may also be caused by a lack of iron and overload of this same metal ion is connected to thalassemia and siderosis [122]. In vivo determination of metal ion distribution is thus highly desirable and progresses have been made towards the design of MRI contrast agents sensitive to the concentration of metal ions. 

Determination of metal ions (Cr3+, Co2+, Cu2+) has been achieved using the metal-catalyzed luminol-peroxide system. The EOF delivery of the CL reagent (H202 pH 11.7) in the aqueous system can be achieved using a side channel (with luminol present in the separation buffer with a pH of 6.0) [168]. 

Schiff bases derived from an aminopyridine and an aromatic aldehyde find use in the spectrophotometric determination of metal ions. For example, iV,iV -bis(salicylidene)-2,3-pyridinediamine 23 has been used in the determination of copper(ll) ions. An advantage of Schiff bases derived from aminopyridines as analytical reagents lies in the simplicity of their preparative procedures <2000CCA81>. 

TABLE 3.1 Comparison of Polarographic Methods for Determination of Metal Ions... 

Sato K, Tanaka S. Determination of metal ions by flow injection analysis with peroxy-oxalate chemiluminescence detection. Microchem J 1996 53 93-8. 

In industry analysis for metals in lubricating oils, greases or fuels is important for checking characteristics on delivery or for testing the quality of used lubricants for the purpose of preventing maintenance. In the first case one talks of the determination of metal ions in oils among others, in the second of wear metals, such as Cd, Cr, Cu, Fe, Mn, Ni, Sb, Sn and Ti. Metals which may be present in lubricants or fuels, are Al, Ba, Ca, K, Li, Mg, Mo, Na, P, Pb, S, Si, V and Zn [74]. This analytical area is very important because considerable financial considerations are related to the use of the correct lubricants, to the possibility of harmful substances developing in fuel oils (S or V) and also to maintenance. 

Studies of reactions such as those discussed above rest upon analytical techniques for the determination of metal ions. Some specific techniques are given below for the measurement of total iron levels, nonhaem iron and for haem iron. 

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