Sample materials

Chamber B is filled with partially degassed sample material at 0°C. Chamber A is filled with air at 37.8°C and at atmospheric pressure. 

For detection of defect dimensions defectometers were used made of examined sample material allowing to reveal defects of 0.25-1% x-rayed steel layer thickness in range of 100-500mm thickness at 11 MeV. 

Particularly in mass spectrometry, where discharges are used to enhance or produce ions from sample materials, mostly coronas, plasmas, and arcs are used. The gas pressure is normally atmospheric, and the electrodes are arranged to give nonuniform electric fields. Usually, coronas and plasmas are struck between electrodes that are not of similar shapes, complicating any description of the discharge because the resulting electric-field gradients are not uniform between the electrodes. 

Fundamentally, introduction of a gaseous sample is the easiest option for ICP/MS because all of the sample can be passed efficiently along the inlet tube and into the center of the flame. Unfortunately, gases are mainly confined to low-molecular-mass compounds, and many of the samples that need to be examined cannot be vaporized easily. Nevertheless, there are some key analyses that are carried out in this fashion the major one i.s the generation of volatile hydrides. Other methods for volatiles are discussed below. An important method of analysis uses lasers to vaporize nonvolatile samples such as bone or ceramics. With a laser, ablated (vaporized) sample material is swept into the plasma flame before it can condense out again. Similarly, electrically heated filaments or ovens are also used to volatilize solids, the vapor of which is then swept by argon makeup gas into the plasma torch. However, for convenience, the methods of introducing solid samples are discussed fully in Part C (Chapter 17). 

A schematic diagram showing the general construction of an arc or spark source. Actual construction details depend partly on whether samples need to be analyzed automatically. The sample material can be placed on the cathode or can even compose the whole of the cathode. If graphite is used, the sample needs to be pressed into the shape of a cathode after admixture with the carbon. 

In some inlet devices, the volatile sample materials are first separated from entrained hydrogen gas or air by condensing them in a coolant bath. Subsequently, when all of the volatile sample components have been condensed and the hydrogen or air has been swept away, the sample is reheated and sent to the plasma flame. 

Although Vickers and DPH microhardness tests should yield the same numerical results on a given material, such is not always the case. Much of the observed variance may be a function of differences ia the volume of sample material displaced by the macro and micro iadentations. 

Both frontal and displacement chromatographies suffer a significant disadvantage in that once a column has been used, part of the sample remains on the column. The column must be regenerated before reuse. In elution chromatography all of the sample material is usually removed from the column... 

Modtilus Measurements Another SCC test technique is the use of changes of modulus as a measure of the damping capacity of a metal. It is known that a sample of a given test material containing cracks will have a lower effec tive modulus than does a sample of identical material free of cracks. The technique provides a rapid and reliable evaluation of the susceptibility of a sample material to SCC in a specific environment. The so-called internal friction test concept can also be used to detect and probe nucleation and progress of cracking and the mechanisms controlling it. 

All the ealeulations for every analytieal line use its own AC-10 virtual unified sample material eontaining 10% of ehemieal element analyzed. In praetiee, instead of AC-10 speeimen, one ean use eertified sample material named Benehmark Referenee Material (BRM). One must know eomplete ehemieal eontent of BRM. Having measured analytieal line intensity of the speeimen, one ean determine the intensity from AC-10 by eorreetion system. Anyone eertified sample material ean be used as BRM for a few elements. Quantitative eomposition of BRM does not depend on the range of varying ehemieal elements eontent in samples analyzed substantially faeilitating a seleetion and ehange of these BRM. 

A very important analytical tool that is overlooked by many sourcetesting personnel is the microscope. Microscopic analysis of a particulate sample can tell a great deal about the type of material collected as well as its size distribution. This analysis is necessary if the sample was collected to aid in the selechon of a piece of control equipment. All of the efficiency curves for particulate control devices are based on fractional sizes. One would not try to remove a submicron-size aerosol with a cyclone collector, but unless a size analysis is made on the sampled material, one is merely guessing at the actual size range. Figure 32-8 is a photomicrograph of material collected during a source test. 

Figure 1 A schematic showing the various energy ioss processes for backscattering from a given depth in a sampie. Energy is iost by momentum transfer between the probe particie and the target particle, and as the probing particle traverses the sample material both before and after scattering.

Measurement of depth profiles is based on detection of the masses of interest during sputter removal of the sample material. Such experiments have several limitations ... 

Appearance potential methods all depend on detecting the threshold of ionization of a shallow core level and the fine structure near the threshold they differ only in the way in which detection is performed. In all of these methods the primary electron energy is ramped upward from near zero to whatever is appropriate for the sample material, while the primary current to the sample is kept constant. As the incident energy is increased, it passes through successive thresholds for ionization of core levels of atoms in the surface. An ionized core level, as discussed earlier, can recombine by emission either of a characteristic X-ray photon or of an Auger electron. 

Visit the student companion website at academic.cengage.com/chemistry/masterton to see sample materials of selected student supplements. You can purchase any Brooks/Cole product at your local college bookstore or at our preferred online store www.ichapters.com. 

Chromatography A technique for separating a sample material into constituent components and then measuring or identifying the compounds by other methods. As an example separation, especially of closely related compounds, is caused by allowing a solution or mixture to seep through an absorbent such as clay, gel, or paper. Result is that each compound becomes adsorbed in a separate, often colored layer. 

A special technique was developed for rare-earth samples in which rapid hydration and carbonation occurred. The rare-earth oxalates were found to be more stable than the oxides and were used as sample material. In the rare-earth processing procedures that include an oxalate precipitate, the oxalate can be used as sample material. The advantages are that no diluent is required, weighing is eliminated, and recovery of the rare earths is simplified. 

Post-column reaction is a common feature of many special types of analyses, the most well-known being the amino acid analyzer that uses ninhydrin with a post-column reactor to detect the separated amino acids. In general, derivatization and post-column reactor systems are techniques of last resort. In some applications they are unavoidable, but if possible, every effort should made to find a suitable detector for the actual sample materials before resorting to derivatization procedures. 

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