On-line separations

The selectivity of ISEs used in flow systems can be boosted by incorporating an on-line separation unit (e.g. an ion-exchange colunm, a dialysis module or a gas-diffusion device) into the hydrodynamic system. Occasionally —particularly when an ion-exchange column is used—, the ancillary... 

Alegret et al. devised a pH ISFET based on a flow-through cell designed by themselves and an FI manifold including a gas-diffusion module for the on-line separation of gaseous analytes with acid-base properties. In this way, they obtained a linear determination range of 1 x 10 -1 x 10 M for ammonia and 7 x 10" -4 x 10 M for sulphur dioxide, with an RSD of 1% and 0.5%, respectively [153]. 

Figure 6.6 Mass spectrum of rare earth elements tREEs) measured by CE-ICP-MS with on line separation of analytes (50 nl solution volume) a) natural isotopic pattern, concentration of each REE - 800ngg b) in an irradiated tantalum target (). S. Becker and H. ]. Dietze, Int. /. Mass Spectrom. Ion Proc. 197, 1-35 (2000). Reproduced by permission of the Royal Society of Chemistry.)...

Flow systems are developed mainly for liquid samples and their complexity can range from simple to very complex manifolds to deal with ultratrace amounts of the target analyte in complex matrices, which often require on-line separation/preconcentration steps. As a wide variety of chemical manipulations can be carried out in an FI manifold, the scope of the FI applications is enormous. Not only liquid samples, but also both gas and solid samples, can be also introduced into the liquid flow manifold if special adaptations are made. Gas samples simply require impermeable tubing. Solids can be either introduced into the system and leached with the help of auxiliary energy e.g. ultrasound) or introduced as slurries. 

M. Zougagh, A. Garcia-de-Torres and J. M. Cano-Pavon, On-line separation and determination of trace amounts of manganese in biological samples by flow injection inductively coupled plasma atomic emission spectrometry. Anal. Lett., 36(6), 2003, 1115-1130. 

Am determination in urine with on-line separation and preconcentration using FI system ICP-MS 52... 

The largest number of automated extraction-chromatographic separations for actinides have used TRU-Resin, and many of these have coupled the column to ICP-MS as an on-line separation (see Table 9.3). TRU-Resin is impregnated with the neutral bifunctional organophosphorus complexant, octyl(phenyl)-A,A-diisobu-tylcarbamoylmethylphosphine oxide (CMPO) in tri-n-butyl phosphate (TBP).26 127 128 The organic stationary phase in this resin binds trivalent, tetravalent, and hexavalent actinide nitrato complexes from nitric acid solutions (see Figure 9.11). The extraction equilibria for representative species are shown in Equations 9.3-9.5, where the bar above a species indicates that it is immobilized on the resin.4... 

FIGURE 9.15 Design of a SI separation system for on-line separation of actinides for ICP-MS detection, where the SI system handles clean solutions and reagents outside the radioactivity containment glove box, while the injection valve and separation column downstream handle radioactive solutions. 

Figure 7.2.12 shows the principal set-up for this experiment. The column, containing the immobilized free radicals consists of an adapted PEEK tube, which fits into the flow probe below the detection cell. Figure 7.2.13 depicts a spectrum of d-n-butylphthalate recorded under the influence of a ( free-radical ) column filled with 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO), immobilized with an aminopropyl spacer on silica. The spectrum is taken from an on-line separation of a two-compound mixture. The line width is of the same order as... 

Isolde is known throughout the world as the on-line isotope separator at the 600 MeV synchrocyclotron at CERE, Geneva. Work has been going on there since 1967 on many topics includino nuclear physics, solid state, atomic physics, etc. There have been great improvements made over the years but it became clear that the physics output could only be increased if there were to be an expansion of the facility. It was decided to build a second on-line separator to be used alternately with the existing Isolde, thus doubling the potential. The new separator is under construction, called Isolde 3, and is scheduled for first operation next year. 

A He-jet coupled on-line mass separator, used in conjunction with a target chamber placed in the LAMPF main beam, offers an especially attractive approach for the study of nuclei far from stability. Such a facility would provide access to isotopes of a number of elements that cannot be efficiently extracted for study at any other type of on-line separator system, and the use of a long capillary transport line would allow the separator ion source to be located outside the accelerator beam-line shielding, greatly reducing the installation cost. The He-jet technique requires thin targets in order for the reaction products to escape, and to produce a sufficient yield of radioisotopes far from stability for detailed nuclear studies, a beam intensity comparable to that available at LAMPF is needed. 

A programme of detailed decay-spectroscopic investigations in the region "northwest of 146Gd" is pursued in collaboration with P. Kleinheinz et al. (KFA Jiilich). These experiments, which also use the on-line separator ISOCELE at Orsay and ISOLDE at CERN, cannot be covered in this brief report. It may suffice to mention here the studies of protons and gamma... 

A schematic plan view of the new on-line separator located on beam line C is given in figure 2. The beam from the accelerator enters the He-jet recoil chamber through a thin Ni window (2mg/cm2), bombards the target and is then stopped in a beam-stopper composed mainly of iron, lead and polystyrene in order to prevent from both neutron and y background. 

Bosch, O.C., Sanchez, R.F., Cano, P.J., Garcia de Torres, A. Automated on-line separation-preconcentration system for platinum determination by electrothermal atomic absorption spectrometry. Anal. Chlm. Acta 494, 97-103 (2003)... 

The activation method requires the use of high-puiity targets, in order to exclude the influence of other nuclear reactions. Chemical procedures may be applied to separate the reaction products and to identify their atomic number Z. If short-lived radionuclides are to be measured, fast separation methods are required, for instance on-line separation in a gas stream that passes a temperature gradient (thermochromatography). In the case of half-lives of the order of milliseconds or less, however, only physical methods are applicable, in particular separation by a sequence of electric and magnetic fields. Stable or long-lived products may be determined by use of mass spectrometry, provided sufficient masses are available. 

The methods used in the investigation of heavy-ion reactions are similar to those described in section 8.6. The high linear energy transfer (LET) and the relatively short range of heavy ions have to be taken into account. On-line separation of shortlived products is of special importance. 

Metal species such as rhodium and palladium spiked to sand or humic acids have been extracted as /3-diketonates and on-line separated and determined by HPLC. The solid phase interface used for this purpose was a LiChrosphere 100 RP-18 cartridge [107]. 

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