Emission spectroscopy analyzer

FIGURE 21.10 Schematic drawing of an emission spectroscopy analyzer, typically used to measure nitrogen concentrations. The output varies with the pressure within the ionization chamber, so the ne e valve and vacuum pump must carefully regulate that pressure. 

Multielemental Analysis Atomic emission spectroscopy is ideally suited for multi-elemental analysis because all analytes in a sample are excited simultaneously. A scanning monochromator can be programmed to move rapidly to an analyte s desired wavelength, pausing to record its emission intensity before moving to the next analyte s wavelength. Proceeding in this fashion, it is possible to analyze three or four analytes per minute. 

Commercial Hquid sodium alumiaates are normally analyzed for total alumiaa and for sodium oxide by titration with ethylene diaminetetraacetic acid [60-00-4] (EDTA) or hydrochloric acid. Further analysis iacludes the determiaation of soluble alumiaa, soluble siHca, total iasoluble material, sodium oxide content, and carbon dioxide. Aluminum and sodium can also be determiaed by emission spectroscopy. The total iasoluble material is determiaed by weighing the ignited residue after extraction of the soluble material with sodium hydroxide. The sodium oxide content is determiaed ia a flame photometer by comparison to proper standards. Carbon dioxide is usually determiaed by the amount evolved, as ia the Underwood method. 

Finished zinc and zinc aHoys are usuaHy analyzed for metals other than zinc by emission spectroscopy and the zinc determined by difference. ASTM method E 27 describes a technique using a dissolved sample and photographic detection. The internal standard is the zinc line at 267.0 nm. However, procedures using soHd samples are generaHy preferred and photoelectric detection often replaces optical detection. Samples are cast and machined on the surface where the arc is stmck. Up to 15 elements can be determined in a few minutes by modem automatic spectrometers. ASTM gives wet chemical methods for metals other than zinc (79). 

Commercially produced barium is analyzed for metallic impurities by means of emission spectroscopy. Carbon content can be deterrnined by combustion, and nitrogen by the Kjeldahl method. Total barium can best be deterrnined gravimetricaHy by precipitation as the sulfate. 

Commercially produced calcium metal is analyzed for metallic impurities by emission spectroscopy. Carbon content is determined by combustion, whereas nitrogen is measured by Kjeldahl determination. 

Alcohol sulfates and alcohol ether sulfates separated by HPLC on a styrene-divinylbenzene copolymer column with 4 1 (v/v) methanol and 0.05 M ammonium acetate aqueous solution as the mobile phase were analyzed by simultaneous inductively coupled argon plasma vacuum emission spectroscopy (IPC), monitoring the 180.7-nm sulfur line as a sulfur-specific detector [294]. This method was applied to the analysis of these surfactants in untreated wastewaters. 

Analytical electron microscopy (AEM) can use several signals from the specimen to analyze volumes of catalyst material about a thousand times smaller than conventional techniques. X-ray emission spectroscopy (XES) is the most quantitative mode of chemical analyse in the AEM and is now also useful as a high resolution elemental mapping technique. Electron energy loss spectroscopy (EELS) vftiile not as well developed for quantitative analysis gives additional chemical information in the fine structure of the elemental absorption edges. EELS avoids the problem of spurious x-rays generated from areas of the spectrum remote from the analysis area. 

Spectroscopy The science of analyzing the spectra of atoms and molecules. Emission spectroscopy deals with exciting atoms or molecules and measuring the wavelength of the emitted electromagnetic radiation. Absorption spectroscopy measures the wavelengths of absorbed radiation. 

Bismuth Molybdates. Bismuth molybdates are used as selective oxidation catalysts. Several phases containing Bi and/or Mo may be mixed together to obtain desired catalytic properties. While selected area electron diffraction patterns can identify individual crystalline particles, diffraction techniques usually require considerable time for developing film and analyzing patterns. X-ray emission spectroscopy in the AEM can identify individual phases containing two detectable elements within a few minutes while the operator is at the microscope. 

In short, emission spectroscopy is considered to be the most accurate, precise and reliable means of quantitative analysis of elements as on date. If proper skill, precautions and wisdom are applied together this method may be adopted safely and conveniently to analyze approximately seventy elements from the periodic table at a concentration as low as 1 ppm. 

Characterization of the modified plastocyanins was by Inductively Coupled Plasma Emission Spectroscopy to analyze for Ru and Cu (1 1 ratio), and by HNMR spectroscopy. In the HNMR characterization the C2H resonance of His59 at 8.2 ppm is seen to be lost due to paramagnetic line broadening effect of the attached Ru(III), Fig. 13 [50]. In a further test it is known that the His59 s of both native plastocyanins react with diethyl pyrocarbonate (DEPC) to give an JV-ethoxyhistidine derivative, (12), which absorbs strongly at 238 nm (e 2750M- cm-i), Fig. 14 [133]. 

In the inductively coupled plasma atomic emission spectroscopy (ICPAES) method (ASTM DD 5600), a sample of petroleum coke is ashed at 700°C (1292°F) and the ash is fused with lithium borate. The melt is dissolved in dilute hydrochloric acid, and the resulting solution is analyzed by inductively coupled plasma atomic emission spectroscopy using aqueous calibration standards. Because of the need to fuse the ash with lithium borate or other suitable salt, the fusibility of ash may need attention (ASTM D1857). 

An alternative approach is to analyze the samples using procedures or instrumentation that will give the maximum amount of data for each sample. For example, recent advances in atomic spectroscopy, i.e., inductively coupled argon plasma emission spectroscopy (ICP-AES), allow 20 to 30 elements to be detected simultaneously. 

Elemental composition A1 12.67%, N 19.73%, 0 67.60%. A1 may be analyzed by various instrumental techniques, including atomic absorption or emission spectroscopy, or colorimetry (see under Aluminum). The nitrate anion in aqueous phase may be measured by the NO3 ion selective electrode. 

The B2O3 content of borax may be determined by extraction into HCl solution followed by complexation with mannitol and titration with dUute NaOH. The Na20 content of horax may he measured by titration of an aqueous solution with dUute HCl. Boron and sodium metals in the acid extract of horax may be analyzed by atomic absorption or emission spectroscopy after appropriate dUution of the extract. In the solid phase B2O3 and Na20 may he measured nondestructively by x-ray techniques. 

Elemental composition Cs 78.94%, Cl 21.06%. An aqueous solution may be analyzed for the element Cs by atomic absorption or emission spectroscopy and chloride by ion chromatography, chloride ion-selective electrode, or by titration with a standard solution of sdver nitrate or mercuric nitrate. 

Iron metal can be analyzed by x-ray spectroscopy, flame- and furnace atomic absorption, and ICP atomic emission spectroscopy at trace concentration levels. Other instrumental techniques include ICP-mass spectrometry for extreme low detection level and neutron activation analysis. 

Elemental composition Li 31.85%, B 49.66%, H 18.50%. The compound is dissolved in water cautiously and the evolved hydrogen is measured by GC using a TCD. The aqueous solution is treated with nitric acid and the diluted nitric acid extract is analyzed for lithium by atomic absorption or emission spectroscopy (See Lithium). 

Elemental composition Li 18.78%, C 16.25%, 0 64.96%. It evolves CO2 with effervescence when treated with dilute acids, which turns limewater milky. Lithium may be analyzed in an aqueous solution by atomic absorption or emission spectroscopy and carbonate anion may be determined by ion chromatography. 

Praesodymium salts can be identified nondestructively by x-ray diffraction. The metal can be analyzed by atomic absorption or emission spectroscopy. The water insoluble oxide and other compounds may be digested with aqua regia, diluted, and analyzed by AA or ICP. 

Emission spectroscopy utilizes the characteristic line emission from atoms as their electrons drop from the excited to the ground state. The earliest version of emission spectroscopy as applied to chemistry was the flame test, where samples of elements placed in a Bunsen burner will change the flame to different colors (sodium turns the flame yellow calcium turns it red, copper turns it green). The modem version of emission spectroscopy for the chemistry laboratory is ICP-AES. In this technique rocks are dissolved in acid or vaporized with a laser, and the sample liquid or gas is mixed with argon gas and turned into a plasma (ionized gas) by a radio frequency generator. The excited atoms in the plasma emit characteristic energies that are measured either sequentially with a monochromator and photomultiplier tube, or simultaneously with a polychrometer. The technique can analyze 60 elements in minutes. 

An easy calibration strategy is possible in ICP-MS (in analogy to optical emission spectroscopy with an inductively coupled plasma source, ICP-OES) because aqueous standard solutions with well known analyte concentrations can be measured in a short time with good precision. Normally, internal standardization is applied in this calibration procedure, where an internal standard element of the same concentration is added to the standard solutions, the samples and the blank solution. The analytical procedure can then be optimized using the internal standard element. The internal standard element is commonly applied in ICP-MS and LA-ICP-MS to account for plasma instabilities, changes in sample transport, short and long term drifts of separation fields of the mass analyzer and other aspects which would lead to errors during mass spectrometric measurements. 

When preparing the cesium- and barium-saturated clays, the 1.0 M solutions used were decanted (after centrifuging) and analyzed semiquantitatively by emission spectroscopy. From those analyses, it appears that the following species were desorbed sodium, potassium, calcium, magnesium, and strontium. It further appeared that desorption of potassium was almost unique to cesium sorption whereas, desorption of the other species appeared to be common to both cesium and barium sorption. Small amounts of other elements such as nickel and copper were also detected by the analyses. However, to what extent the observed concentrations may represent desorption and to what extent they may represent the dissolution of sparingly soluble substances (particularly hydroxide species) is as yet-uncertain. The apparent concentrations of the desorbed species per gram of clay are given in Table III. 

The use of x-ray fluorescence was originally intended to obtain information about the major element matrix of coal ashes that were to be analyzed for trace elements by optical emission spectroscopy. Both low-temperature (<150°C) and high-temperature (450°C) coal ashes, prepared as described by Ruch et al. (I), were analyzed, and the method of Rose et al. (2) was adapted to determine the major and minor elements (Si, Ti, Al, Fe, Mg, Ca, K, and V). The instrumental parameters used for these elements are given in Table I. 

Approximate contents of 14 minor and trace elements in oils produced from three coals by the catalytic hydrogenation process of Gulf Research and Development Co. were determined by emission spectroscopy. The results were compared with corresponding data for the original coals and the solid residues from the process. The contents of ash, sulfur, vanadium, lead, and copper are near or below the limits specified for an oil to be fired directly in a gas turbine while sodium and probably calcium are too high. Titanium appears to be somewhat enriched in the oils analyzed relative to other elements, suggesting its presence in organo-metallic complexes. 

The ashes were analyzed by emission spectroscopy using a d.c. arc and a Jarrell-Ash Wadsworth spectrograph. A visual comparison of line intensities with standard rock samples established the approximate elemental concentrations. Based on experience, the true content of any element is most probably within the range 2 to 0.5X the stated value. 

Investigation of atomic spectra yields atomic energy levels. An important chemical application of atomic spectroscopy is in elemental analysis. Atomic absorption spectroscopy and emission spectroscopy are used for rapid, accurate quantitative analysis of most metals and some nonmetals, and have replaced the older, wet methods of analysis in many applications. One compares the intensity of a spectral line of the element being analyzed with a standard line of known intensity. In atomic absorption spectroscopy, a flame is used to vaporize the sample in emission spectroscopy, one passes a powerful electric discharge through the sample or uses a flame to produce the spectrum. Atomic spectroscopy is used clinically in the determination of Ca, Mg, K, Na, and Pb in blood samples. For details, see Robinson. 

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