Solid sample analysis

Thermal ionization TI Ionization by heating Atomic ions Isotope ratio, Trace analysis Solid samples... 

The results of this study were divided into three areas stack gas analysis, solids sampling and analysis, and the mercury mass balance. 

Prior to analysis, solid samples are usually homogenized, dried or freeze-dried and ground with a mill to obtain particles with a diameter of less than 1 mm or 0.2 mm. Sometimes, surrogates are added before the extraction process. 

The most common approach to phosphorus determination is the assessment of phosphate in wet chemistry. Therefore, the majority of samples should be dissolved before analysis. Solid samples are decomposed by alkali or acid treatment silicate is dissolved by treatment with fluoric acid. Samples of biological material are reduced to ash using an appropriate laboratory oven or are digested with hot oxidative acids. A direct phosphate assessment is advised only in some water samples. The determination of total phosphoms is not used to identify soil fertility due to phosphorus content rather, water extracts are used of various pH and ionic strength. 

Eleetron energy-loss speetroseopy is used for obtaining speetroseopie data as a eonvenient substitute for optieal speetroseopy, and, taking advantage of diflferenees in seleetion rules, as an adjimet to optieal speetroseopy. In addition, eleetron speetroseopy has many applieations to ehemieal and stnietural analysis of samples in the gas phase, in the solid phase, and at the solid-gas interfaee. 

When working with a solid sample, it often is necessary to bring the analyte into solution by dissolving the sample in a suitable solvent. Any solid impurities that remain are removed by filtration before continuing with the analysis. 

Second, the majority of analytical techniques, particularly those used for a quantitative analysis, require that the analyte be in solution. Solid samples, or at least the analytes in a solid sample, must be brought into solution. 

Infrared spectroscopy is routinely used for the analysis of samples in the gas, liquid, and solid states. Sample cells are made from materials, such as NaCl and KBr, that are transparent to infrared radiation. Gases are analyzed using a cell with a pathlength of approximately 10 cm. Longer pathlengths are obtained by using mirrors to pass the beam of radiation through the sample several times. 

Preparing the Sample Flame and plasma sources are best suited for the analysis of samples in solution and liquid form. Although solids can be analyzed by direct insertion into the flame or plasma, they usually are first brought into solution by digestion or extraction. 

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). 

In some cases, it may be convenient to dissolve a solid and present it for analysis as a solution that can be nebulized and sprayed as an aerosol (mixed droplets and vapor) into the plasma flame. This aspect of analysis is partly covered in Part B (Chapter 16), which describes the introduction of solutions. There are vaporization techniques for solutions of solids other than nebulization, but since these require prior evaporation of the solvent, they are covered here. There are also many solid samples that need to be analyzed directly, and this chapter describes commonly used methods to do so. 

Direct atomic absorption spectrometry (AAS) analysis of increasing (e 0,10 g) mass of solid samples is the great practical interest since in a number of cases it allows to eliminate a long-time and labor consuming pretreatment dissolution procedure of materials and preconcentration of elements to be determined. Nevertheless at prevalent analytical practice iS iO based materials direct AAS are not practically used. 

In Laser Ionization Mass Spectrometry (LIMS, also LAMMA, LAMMS, and LIMA), a vacuum-compatible solid sample is irradiated with short pulses ("10 ns) of ultraviolet laser light. The laser pulse vaporizes a microvolume of material, and a fraction of the vaporized species are ionized and accelerated into a time-of-flight mass spectrometer which measures the signal intensity of the mass-separated ions. The instrument acquires a complete mass spectrum, typically covering the range 0— 250 atomic mass units (amu), with each laser pulse. A survey analysis of the material is performed in this way. The relative intensities of the signals can be converted to concentrations with the use of appropriate standards, and quantitative or semi-quantitative analyses are possible with the use of such standards. 

Auger electron spectroscopy (AES) is a technique used to identify the elemental composition, and in many cases, the chemical bonding of the atoms in the surface region of solid samples. It can be combined with ion-beam sputtering to remove material from the surface and to continue to monitor the composition and chemistry of the remaining surface as this surface moves into the sample. It uses an electron beam as a probe of the sample surface and its output is the energy distribution of the secondary electrons released by the probe beam from the sample, although only the Ai er electron component of the secondaries is used in the analysis. 

There are advantages to direct solid sampling. Sample preparation is less time consuming and less prone to contamination, and the analysis of microsamples is more straightforward. However, calibration may be more difficult than with solution samples, requiring standards that are matched more closely to the sample. Precision is typically 5% to 10% because of sample inhomogeneity and variations in the sample vaporization step. 

Rutherford back-scattering spectroscopy (RBS) is one of the most frequently used techniques for quantitative analysis of composition, thickness, and depth profiles of thin solid films or solid samples near the surface region. It has been in use since the nineteen-sixties and has since evolved into a major materials-characterization technique. The number and range of applications are enormous. Because of its quantitative feature, RBS often serves as a standard for other techniques. 

The sensitivity, accuracy, and precision of solid-sample analysis have been greatly improved by coupling LA with ICP-OES-MS. The ablated species are transported by means of a carrier gas (usually argon) into the plasma torch. Further atomization, excitation, and ionization of the ablated species in the stationary hot plasma result in a dramatic increase in the sensitivity of the detection of radiation (LA-ICP-OES) or of the detection of ions (LA-ICP-MS). 

As already remarked in Sect. 4.5.1 (Introduction), LA was primarily designed as a technique for direct sampling in the bulk analysis of solid samples. The main advantages of LA are the possibility of ablating all types of solid material (metals, isolators, glasses, crystals, minerals ceramics, etc.), no special requirements on the... 

A solid sample is bombarded with a stream of inert gas ions. Some of these ions are backscattered with some loss of energy after colliding with the surface atoms. Analysis of the scattered ion energies is done for identification of the surface atoms present. 

Comparative method. Sometimes, as in the analysis of a mineral, it may be impossible to prepare solid synthetic samples of the desired composition. It is then necessary to resort to standard samples of the material in question (mineral, ore, alloy, etc.) in which the content of the constituent sought has been determined by one or more supposedly accurate methods of analysis. This comparative method, involving secondary standards, is obviously not altogether satisfactory from the theoretical standpoint, but is nevertheless very useful in applied analysis. Standard samples can be obtained from various sources (see Section 4.5). 

Before analysis the representative solid sample is usually dried at 105-110 °C, or at some higher specified temperature if necessary, to constant weight. The results of the analysis are then reported on the dry basis, viz. on a material dried at a specified temperature. The loss in weight on drying may be determined, and the results may be reported, if desired on the original moist basis these... 

Ion chromatography has been successfully applied to the quantitative analysis of ions in many diverse types of industrial and environmental samples. The technique has also been valuable for microelemental analysis, e.g. for the determination of sulphur, chlorine, bromine, phosphorus and iodine as heteroatoms in solid samples. Combustion in a Schoniger oxygen flask (Section 3.31 )is a widely used method of degrading such samples, the products of combustion being absorbed in solution as anionic or cationic forms, and the solution then directly injected into the ion chromatograph. 

Solid samples are generally treated in one of two ways. If completely soluble, they can be dissolved directly and completely in a suitable solvent. Alternatively, if the samples contain insoluble materials that are of no interest, then they can be extracted with a selected solvent to obtain the relevant compounds in solution. The extract can be subsequently filtered or centrifuged to remove any unwanted substances that make up the sample matrix. The procedure will differ, depending on the amount of the substances present that are germane to the analysis. The preparation of samples for LC analysis from solid... 

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