Sparks, atomic spectroscopy

Chemical Analysis. The presence of siUcones in a sample can be ascertained quaUtatively by burning a small amount of the sample on the tip of a spatula. SiUcones bum with a characteristic sparkly flame and emit a white sooty smoke on combustion. A white ashen residue is often deposited as well. If this residue dissolves and becomes volatile when heated with hydrofluoric acid, it is most likely a siUceous residue (437). Quantitative measurement of total sihcon in a sample is often accompHshed indirectly, by converting the species to siUca or siUcate, followed by deterrnination of the heteropoly blue sihcomolybdate, which absorbs at 800 nm, using atomic spectroscopy or uv spectroscopy (438—443). Pyrolysis gc followed by mass spectroscopic detection of the pyrolysate is a particularly sensitive tool for identifying siUcones (442,443). This technique rehes on the pyrolytic conversion of siUcones to cycHcs, predominantly to [541-05-9] which is readily detected and quantified (eq. 37). 

Jones and Isaac 16 ) compared atomic absorption spectroscopy and spark emission spectroscopy for the determination of several elements in plant tissue. By comparing results statistically using a t-test, no significant differences were found for calcium, manganese, iron, copper, zinc, and aluminium, but significant differences were found for potassium and magnesium at the 0.01 % level. Breck162) made a similar comparison study for 15 elements. 

A technique that utilizes a solid sample for light emission is spark emission spectroscopy. In this technique, a high voltage is used to excite a solid sample held in an electrode cup in such a way that when a spark is created with a nearby electrode, atomization, excitation, and emission occur and the emitted light is measured. Detection of what lines are emitted allows for qualitative analysis of the solid material. Detection of the intensity of the lines allows for quantitative analysis. 

In the early days of atomic spectroscopy, dc and ac arcs and high-voltage sparks were popular for use in excitation of atomic emission. Such sources have almost entirely been replaced by the ICP. 

Atomic emission The emission of radiation by atoms that have been excited in a plasma, a flame, or an electric arc or spark. Atomic emission spectroscopy (AES) An analytical method based on atomic emission. 

This chapter deals with optical atomic, emission spectrometry (AES). Generally, the atomizers listed in Table 8-1 not only convert the component of samples to atoms or elementary ions but, in the process, excite a fraction of these species to higher electronic stales.. 4, the excited species rapidly relax back to lower states, ultraviolet and visible line spectra arise that are useful for qualitative ant quantitative elemental analysis. Plasma sources have become, the most important and most widely used sources for AES. These devices, including the popular inductively coupled plasma source, are discussedfirst in this chapter. Then, emission spectroscopy based on electric arc and electric spark atomization and excitation is described. Historically, arc and spark sources were quite important in emission spectrometry, and they still have important applications for the determination of some metallic elements. Finally several miscellaneous atomic emission source.s, including jlanies, glow discharges, and lasers are presented. 

Many analytical applications of atomic spectroscopy produce their spectra by arc or spark excitation techniques and these methods form the basis for much of the present practice in the field. The historical development in this area is most difficult to document since almost from the start, after observations of the spectrum from the sun, the attempt was to utilize high-energy sources. This led immediately to arc and spark methods. The present-day applications of the arc or spark are improvements of the early work with attempts to better stabilize and control excitation conditions within the arc or spark in an effort to improve analytical data derived from the spectra. These techniques will be discussed in Chapter 5, which deals with accessory equipment for arc and spark spectrochemical analysis. 

Atomic fluorescence is the most recent development in analytical atomic spectroscopy thus it has not had time to be evaluated as well as other techniques. Further developments in this field with respect to optimizing sources and sample cells, together with improvements in instrumental parameters and development of readily available commercial instrumentation, should lead to this technique serving in the area of analytical spectral methods to supplement the already well-established arc and spark emission, flame emission, and atomic absorption spectroscopy. 

This textbook is an outgrowth of the author s experience in teaching a course, primarily to graduate students in chemistry, that included the subject matter presented in this book. The increasing use and importance of atomic spectroscopy as an analytical tool are quite evident to anyone involved in elemental analysis. A number of books are available that may be considered treatises in the various fields that use atomic spectra for analytical purposes. These include areas such as arc-spark emission spectroscopy, flame emission spectroscopy, and atomic absorption spectroscopy. Other books are available that can be catalogued as methods books. Most of these books serve well the purpose for which they were written but are not well adapted to serve as basic textbooks in their fields. 

This book is intended to fill the aforementioned gap and to present the basic principles and instrumentation involved in analytical atomic spectroscopy. To meet this objective, the book includes an elementary treatment of the origin of atomic spectra, the instrumentation and accessory equipment used in atomic spectroscopy, and the principles involved in arc-spark emission, flame emission, atomic absorption, and atomic fluorescence. 

Giinther, D., Jackson, S.E., Longerich, H.P. (1999) Laser ablation and arc/spark sohd sample introduction into inductively coupled plasma mass spectrometers. Spectrochimica Acta Part B Atomic Spectroscopy, 54,381-409. 

There are several analytical techniques available for determination of minerals in nuts. For example there is atomic absorption. X-ray fluorescence, flame emission and arc/spark emission spectroscopy, spectrophotometry and specific ion electrodes. With inductively coupled plasma spectrometery (ICPS), it is possible to determine P, K, S, Ca, Mg, Na, Al, Zn, Mn, Fe, Co, Mo and B in plant materials. ICPS has the potential to determine all the nutritional elements (except nitrogen) with a polychromator sequentially scanning monochromator in the single digestion (Zarcinas et al. 1987). 

The focus of this section is the emission of ultraviolet and visible radiation following thermal or electrical excitation of atoms. Atomic emission spectroscopy has a long history. Qualitative applications based on the color of flames were used in the smelting of ores as early as 1550 and were more fully developed around 1830 with the observation of atomic spectra generated by flame emission and spark emission.Quantitative applications based on the atomic emission from electrical sparks were developed by Norman Lockyer (1836-1920) in the early 1870s, and quantitative applications based on flame emission were pioneered by IT. G. Lunde-gardh in 1930. Atomic emission based on emission from a plasma was introduced in 1964. 

The conventional method for quantitative analysis of galHum in aqueous media is atomic absorption spectroscopy (qv). High purity metallic galHum is characteri2ed by trace impurity analysis using spark source (15) or glow discharge mass spectrometry (qv) (16). 

Quantitative aluminum deterrninations in aluminum and aluminum base alloys is rarely done. The aluminum content is generally inferred as the balance after determining alloying additions and tramp elements. When aluminum is present as an alloying component in alternative alloy systems it is commonly deterrnined by some form of spectroscopy (qv) spark source emission, x-ray fluorescence, plasma emission (both inductively coupled and d-c plasmas), or atomic absorption using a nitrous oxide acetylene flame. 

The predorninant method for the analysis of alurninum-base alloys is spark source emission spectroscopy. SoHd metal samples are sparked direcdy, simultaneously eroding the metal surface, vaporizing the metal, and exciting the atomic vapor to emit light ia proportion to the amount of material present. Standard spark emission analytical techniques are described in ASTM ElOl, E607, E1251 and E716 (36). A wide variety of weU-characterized soHd reference materials are available from major aluminum producers for instmment caUbration. 

In addition to the spark emission methods, quantitative analysis directly on soHds can be accompHshed using x-ray fluorescence, or, after sample dissolution, accurate analyses can be made using plasma emission or atomic absorption spectroscopy (37). 

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