Analysis of Heavy and Transition Metals

Polymethacrylate and polyvinyl resins play only a secondary role in the manufacture of cation exchangers. Presently, the only polymethacrylate-based cation exchanger is offered by Sykam (Gauting, Germany) under the trade name LCA K02. This column differs from its PS/DVB analogue (see Table 3-24) only in the particle size (5 pm) and exchange capacity (0.4 mequiv/g). With a tartaric acid eluent, this phase is preferred for the analysis of heavy and transition metals. 

The CMMS micromembrane suppressor also allows the application of concentration gradients in combination with conductivity detection that is indispensable for cation detection. A mixture of hydrochloric acid and 2,3-diaminopropionic acid suitable for chemical suppression is used as the eluent. The gradient technique, however, plays a secondary role in cation analysis, since it can only be applied for the analysis of alkali and alkaline-earth metals as well as a number of short-chain aliphatic amines. It is definitely not suitable for the analysis of heavy and transition metals, where different... 

S.2 Analysis of Heavy and Transition Metals by Direct Conductivity Detection... 

In most applications, the method of cation exchange with direct conductivity detection does not have the required specificity for the analysis of heavy and transition metals. Ionic matrix components which are often present in high excess are also detected. 

Fig. 8-12. Analysis of heavy and transition metals in industrial waste water. — Separator column IonPac CS5 eluent 0.05 mol/L oxalic acid + 0.095 mol/L LiOH flow rate 1 mL/min detection photometry at 520 nm after post-column reaction with PAR injection 50 pL waste water (1 50 diluted).

Finally, it should be pointed out that until now the application of ion chromatography to the analysis of heavy and transition metals such as iron, copper, nickel, and manganese in the ppb range in 50% sodium hydroxide solution [96, 97] was not possible. A concentration procedure developed by Kingston et al. [98] is used for the AAS analysis of heavy metals in sea water. It is based on the selective concentration of heavy metals on a macroporous iminodiacetic acid resin, where divalent cations are retained by chelation. Their affinity toward the stationary phase decreases in the order... 

A growing number of applications using post-column derivatization in combination with photometric detection opened the field of heavy and transition metal analysis for ion chromatography, thus providing a powerful extension to conventional atomic spectroscopy methods. 

In spite of strong competition from atomic spectrometric techniques, ion chromatography of heavy and transition metal cations is now well established as the relative cheapness, ease of automation, and online capability is particularly attractive in a wide variety of routine trace analysis. 

Anion exchangers such as the IonPac AS5 are also suited for the analysis of com-plexed transition metals and heavy metals, which opens another field of application for ion chromatography. Examples of respective chromatograms for the separation of metal-EDTA complexes as well as for metal-chloro complexes are displayed in Figs. 3-78 and 3-79. 

Ion chromatography gained general acceptance as fast and sensitive multielement detection method for the determination of alkali and alkaline earth metals, heavy and transition metals, actinides and lanthanides, as well as selected organic cations, allowing detection limits in the range of microgram per liter and analysis time of less than 20 min. 

Many laboratories have gathered extensive experience in the application of ion chromatography (IC) for the analysis of inorganic and organic anions. Small carboxylate anions. Groups lA and IIA cations, and heavy metal ions have been identified in tobacco and tobacco smoke by this method. Several of these applications have been presented as tobacco journal (250) and tobacco conference [TCRC (2951), TSRC(1273)] papers. At the 1999 TSRC, Perini (20A85) presented a method associated with IC called transition metal IC (TMIC). TMIC can be used for specific resolution and specia-tion of transition metal ions in tobacco and related matrices. Perini showed that TMIC could be used to detect and spe-ciate at least nineteen transition metal ion. 

The last two forms include up to 2% of the total metal content but they are considered as most important for plant nutrition. Until recently in agrochemical, nutrient and ecological investigations attention has been paid mostly to these two forms and analysis has been performed after extraction with water, buffer solutions or other weak extraction media. However the anthropogenic activity leads among other things to increase in soil pH. The result is slow transition from the silicate to the aluminium buffer region where heavy and toxic metals are released from the minerals. Therefore it is very useful to know more about the content of soils than the usual available quantities. 

The analysis of tetramethylammonium hydroxide (TMAH) solutions manufactured by SACHEM Inc. of Cleburne, Texas, includes the determination of trace elements. These elements cause less-than-optimum performance of integrated circuit boards manufactured by SACHEM s customers that use these solutions in their processes. Alkali and alkaline earth metals (e.g., Li, Na, K, Mg, Ca, and Ba) can reduce the oxide breakdown voltage of the devices. In addition, transition and heavy metal elements (e.g., Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, and Pb) can produce higher dark current. Doping elements (e.g., B, Al, Si, P, As, and Sn) can alter the operating characteristics of the devices. In SACHEM s quality control laboratory, ICP coupled to mass spectrometry is used to simultaneously analyze multiple trace elements in one sample in just 1 to 4 min. This ICP-MS instrument is a state-of-the-art instrument that can provide high throughput and low detection Emits at the parts per thousand level. Trace elemental determination at the parts per thousand level must be performed in a clean room so that trace elemental contamination from airborne particles can be minimized. 

It is the goal of this book to present in one place the key features, methods, tools, and techniques of physical inorganic chemistry, to provide examples where this chemistry has produced a major contribution to multidisciplinary efforts, and to point out the possibilities and opportunities for the future. Despite the enormous importance and use of the more standard methods and techniques, those are not included here because books and monographs have already been dedicated specifically to instrumental analysis and laboratory techniques. The 10 chapters in this book cover inorganic and bioinorganic spectroscopy (Solomon and Bell), Mossbauer spectroscopy (Miinck and Martinho), magnetochemical methods (Kogerler), cryoradiolysis (Denisov), absolute chiral structures (Riehl and Kaizaki), flash photolysis and studies of transients (Ferraudi), activation volumes (van Eldik and Hubbard), chemical kinetics (Bakac), heavy atom isotope effects (Roth), and computational studies in mechanistic transition metal chemistry (Harvey). 

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