Solvent extraction chromatography

Separation and detection methods The common methods used to separate the Cr(III)/(VI) species are solvent extraction, chromatography and coprecipitation. In case of Cr(VI) from welding fumes trapped on a filter, a suitable leaching of the Cr(VI) from the sample matrix is needed, without reducing the Cr(VI) species. The most used detection methods for chromium are graphite furnace AAS, chemiluminescence, electrochemical methods, ICP-MS, thermal ionization isotope dilution mass spectrometry and spectrophotometry (Vercoutere and Cornelis 1995)- The separation of the two species is the most delicate part of the procedure. 

Chromatographic procedures applied to the identification of proteinaceous paint binders tend to be rather detailed consisting of multiple analytical steps ranging from solvent extractions, chromatography clean up, hydrolysis, derivatisation reactions, and measurement to data analysis. Knowledge of the error introduced at each step is necessary to minimise cumulative uncertainty. Reliable results are consequently obtained when laboratory and field blanks are carefully characterised. Additionally, due to the small amounts of analyte and the high sensitivity of the analysis, the instrument itself must be routinely calibrated with amino acid standards along with measurements of certified reference proteins. All of these factors must be taken into account because many times there is only one chance to take the measurement. 

Radiochemical purification of the induced activity in the presence of carrier involves chemical operations such as precipitation, distillation, solvent extraction, chromatography, and ion exchange. While the chemistry performed on the carrier and sample should be designed to isolate the material in a pure state, a useful operation frequently carried out is scavenging. Strongly adsorptive precipitates such as ferric hydroxide, lanthanum fluoride, and antimony sulfide may be formed in the solution. These precipitates, by coprecipitation, occlusion, and surface adsorption can be used to remove unwanted traces of activity. A scavenging agent should be chosen that wdll not carry down appreciable amounts of the carrier from solution. An alternative method is to add hold-back carriers for the unwanted traces of activity and precipitate the required element in their presence. 

C-Aromatic lycorine-type alkaloids have been discovered in the plants of the Amaryllidaceae family. Two new 2-oxo-pyrrolophenanthridinium alkaloids, zefbetaine (59) and zeflabetaine (60), together with several known Amaryllidaceae alkaloids, have been isolated from fresh mature seeds of Zephranthes flava by gradient solvent extraction, chromatography, and deri-vatization (108). Their structures were characterized by comprehensive spectroscopic methods, chemical transformations, and synthesis. They are listed in Fig. 9. 

Chemical purity. Chemical purity is the fraction of a radiopharmaceutical in the form of the desired chemical molecule whether all of it is radiolabeled or not. The presence of extraneous stable atoms may cause adverse reactions and is not desirable in a PET radiopharmaceutical. These impurities arise from the incomplete synthesis, addition of extraneous ingredients during the synthesis, and so on. Chemical methods such as the spectrophotometric method, ion exchange, solvent extractions, chromatography, etc. are applied to measure the level of these chemical impurities. Again, these tests can be performed a priori in many dry runs and thus the level of chemical impurities can be established, prior to human administration. 

Fermium readily forms complexes with a variety of organic ligands, e.g. j9-diketones [18], hydroxycarboxylic adds [4, 15, 20-22], organophosphorus esters [23-25], and alkylamines [26]. Lactic and a-hydroxyisobutyric adds have long been used as eluants for inner-series separation of trivalent actinides by cation-exchange chromatography. However, more recently, di-2-ethylhexyl-orthophosphoric acid [27] and Alamine 336 (a mixed n-octyl and n-decyl tertiary amine) [28] have been used for similar separations of Fm by solvent extraction chromatography. 

As with Md, the physical separation of the nobelium atoms from the target material can be made using the recoil-atom catcher technique. It is preferable to combine this with the gas jet technique since the atoms are deposited on the catcher foil in nearly a monolayer and can be easily rinsed off the surface with dilute acid without complete dissolution of the foil. Isolation of the No from other actinides produced in the bombardment and from any target material transferred to the foil can be readily made using schemes based on the separation of divalent ions from trivalent ones, e.g. selective elution by solvent extraction chromatography using HDEHP as the stationary organic phase and 0.05 n HCl... 

In over 600 experiments, Maly et al. subjected about 50 000 atoms of No to cation-exchange and co-precipitation studies [51]. These tracer experiments showed that nobelium exhibits a chemical behavior substantially different from the trivalent actinides but similar to the divalent alkaline-earth elements, Sr, Ba, and Ra. Thus, the divalent ion of nobelium is the most stable species in aqueous solution. Additional experiments, which used the technique of solvent extraction chromatography, were performed under a variety of oxidizing conditions and allowed an estimate of +1.45 V for °(No - No ) [53]. 

In further ion-exchange experiments using solvent extraction chromatography, Hulet and co-workers investigated the chloride complexation of element 104 and compared it to that of the actinides and Hf [80]. The anionic chloride complexes of 104 were compared to those of Hf, Cm, and Fm by testing their relative adsorbabilities onto a column containing a quaternary amine. The results showed that in 12 M HCl solutions the chloride complexation of element 104 was clearly stronger than those of the trivalent actinides and quite similar to that of Hf. 

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