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The sector mass spectrometer functions using the combined mass selection of both an electrostatic field and a magnetic field. For this reason it is often called a double focusing mass spectrometer. A diagram of a basic double focusing mass analyzer is shown in figure 23. Consider an ion, mass (mi) and charge (z) (in electron charge units) entering the electric field (E) at velocity (v). The ion will describe an arc of radius (r1) and then enter the magnetic sector. The Sector Mass Spectrometer   The sector mass spectrometer functions using the combined mass selection of both an electrostatic field and a magnetic field. For this reason it is often called a double focusing mass spectrometer. A diagram of a basic

the boiling points of the sample solvent and those of the components of the sample.       An alternative procedure, "solute focusing method" has been shown to be more effective, but, unfortunately, requires more complicated and expensive equipment. The sample injector is designed to have two consecutive, independently heated and cooled zones at the beginning of the column. A diagram of the solute focusing system is shown in figure 9.     Figure 9. The Solute Focusing Method of Injection   Both zones are initially cooled and the sample is injected into the first zone. Sample splitting almost inevitably occurs and the carrier gas is allowed to remove the solvent and then the first zone is heated and the second zone kept cool. The solutes in the first zone pass through the zone at the higher temperature and accumulate at the beginning of the cooled second zone and are, thus, focused at the beginning of the column. When the focusing is complete the

Sampling by Solute Focusing Another method of sampling that avoids sample splitting is the 'solute focusing method' which is more effective, but requires more complicated and expensive equipment. The injector is designed so that there are two consecutive, independently heated and cooled zones located at the beginning of the column. A diagram of the solute focusing system is shown in figure 11. Figure 11 The Solute Focusing Method sampling   Initially the two zones are cooled

The success of this method depends on there being a significant difference between the boiling points of the solutes and any solvent in which they are dissolved. An alternative procedure, called the 'solute focusing method' is more effective, but requires more involved and expensive equipment. The injector is designed to have two consecutive, independently heated and cooled zones located at the front of the column. A diagram of the solute focusing system is shown in figure (5). The second zone is now heated, using an appropriate temperature program, and the separation developed in the normal manner. This technique is more flexible than the 'retention gap method' but the apparatus and the procedure

second skimmer cone. The space in front of the first cone, is evacuated by a high-vacuum pump. In the region between the first cone and the second skimmer-cone, the pressure is maintained by a mechanical pump at about 2 mbar and, as the sample expands into this region, a supersonic jet is formed.   This jet of gas and ions, flows through a slightly smaller orifice into the apex of the second cone. The emerging ions are extracted by negatively charged electrodes (-100 to -600 V) into the focusing region of the spectrometer, and then into the mass analyzer. The ICP ion source has a number of unique advantages; the samples are introduced at atmospheric pressure, the degree of ionization is relatively uniform for all elements, and singly charged ions are the principal ion product. In addition, sample dissociation is highly efficient and few, if any, molecular fragments of the original sample remain to pass into the mass spectrometer. As a result of the high ion concentration of

nbsp; The GC/MS analysis was performed on a Pye 204 GC in conjunction with VG double focusing magnetic sector mass spectrometer and a Finnigan INCOS 2300 data system. The transfer line was maintained at 350�C, the ion source at 300�C and the electron impact ionization took place at 70 eV. The total ion current of a potsherd extract is shown in figure 61. It is seen that an interesting selection of lipid materials has been extracted from the potsherd. according to the authors, the technique is now a routine procedure for ceramic materials found at the various archaeological site