Atomic emission analysis

Several methods have been used to determine the number and position of metal atoms affixed to the protein surface. The number of metal atoms is commonly determined by atomic absorption analysis [16] or by inductively coupled plasma (ICP) atomic emission analysis [15]. Under favorable circumstances, the metal ratios in modified derivatives can be determined by UV-vis... 

A plasma is a globally neutral environment formed by atoms in equilibrium between their neutral and ionised (1 to 2%) state and by electrons (1018/cm3). Plasmas are considered the fourth state of matter. Essentially, plasmas that are inductively coupled are used in atomic emission analysis. The colour of the plasma depends on the gas used to form it. 

In atomic emission analysis, one or several specific spectral lines are monitored for each analyte. It is technically difficult and requires a high performance instrument because emission of radiation does not only occur from the analyte but also from any additional material introduced in the high temperature thermal source (e.g. matrix, solution). Because emission can occur from either excited or ionised atoms, thousands of different spectral lines can be observed. Several of these lines are much more intense than those due to the analyte, which can be present at ultratrace levels. 

Serum containing Na+ gave a signal of 4.27 mV in an atomic emission analysis. Then 5.00 mL of 2.08 M NaCl were added to 95.0 mL of serum. This spiked serum gave a signal of 7.98 mV. Find the original concentration of Na+ in the serum. 

Many metals in seawater can be preconcentrated for analysis by coprecipitation with Ga(OH)3. A 200-p.L HC1 solution containing 50p,g of Ga3+ is added to 10.00 mL of the seawater. When the pH is brought to 9.1 with NaOH, a jellylike precipitate forms. After centrifugation to pack the precipitate, the water is removed and the gel is washed with water. Then the gel is dissolved in 50 p,L of 1 M HN03 and aspirated into an inductively coupled plasma for atomic emission analysis. The preconcentration factor is 10 mL/50 p,L = 200. The figure shows elemental concentrations in seawater as a function of depth near hydrothermal vents. 

Tin is usually determined as the total metal, but it may also be measured as specific organotin compounds. Flame atomic absorption analysis is the most widely used and straightforward method for determining tin furnace atomic absorption analysis is used for very low analyte levels and inductively coupled plasma atomic emission analysis is used for multianalyte analyses that include tin. 

Atomic absorption remained the technique of choice until relatively recently. However, with the introduction of plasma sources, atomic emission, in the form of inductively coupled plasma spectroscopy, has made a comeback. This development is now receiving historical attention, and was the subject of a symposium held in 1999. Papers discussed atomic emission analysis prior to 1950,206 the fact that emission techniques developed continuously, even in the period when absorption methods were dominant,207 and the development of the plasma sources on which the new techniques depend.208 Also discussed was the powerful hyphenated technique of ICP-MS,209 and the history of one of the leading manufacturers of atomic emission instruments.210... 

Since the hollow-cathode lamp spectra used in AAS are relatively simple, spectral bandwidths narrower than 0.1 nm are seldom if ever used. In atomic emission analysis, however, higher resolving power is often essential, particularly when the excitation source (e.g. the nitrous oxide—acetylene flame) is producing a complex spectrum. The instrument should, therefore, provide a wide range of slit settings and a convenient digital display of the wavelength in use for the operator. 

CsCl Suprapur from Merck was used for matrix modifier preparation for sodium determination by flame atomic emission analysis. 

The reference materials for the calibration of the spectrophotometer for flame atomic emission analysis were prepared from the sodium standard solution by its dilution with water and addition of the matrix modifier blank (CsCl 0.1% solution in water), 0.1, 0.2, 0.4, 0.6 and 1.0 ppm. A solution with sodium concentration of 0.5 ppm ( true value) was used as a test solution. 

All measurements were performed with the program GIRAF and with the previous ones without shutdown of the instrument at the same analytical conditions (according to Perkin-Elmer cookbook ) by the same analyst with the same reference materials applied as calibration and test solutions. The matrix modifier for lead determination by graphite furnace analysis was used separately from the reference materials, i.e. was not mixed with them. The matrix modifier for sodium determination by flame atomic emission analysis was introduced in all corresponding solutions (the blank and the reference materials for the calibration and test). Three replicates of all measurements were made. 

As an example, contrast the problems associated with the inductively coupled plasma atomic emission analysis of calcium carbonate with those for a real calcium-containing sample. In the former, the number of components is small and the variables likely to affect the results are reasonably few. Principal among the variables are the physical losses of analyte due to the evolution of carbon dioxide when the sample is dissolved in acid the effect of the anion of the acid and of the radio-frequency power on the intensity of the calcium emission line the position of the plasma with respect to the entrance slit to the spectrometer and the quality of the standard calcium solutions used for calibration. 

After a modified protein is prepared, the site of modification must be determined rigorously. It also is necessary to ensure that the structure of the protein has not been perturbed by the modification. Several methods have been used to determine the number and position of metal atoms affixed to the protein surface. The number of metal atoms is commonly determined by atomic absorption analysis (194) or by inductively coupled plasma (ICP) atomic emission analysis (23, 146). Under favorable circumstances, the metal ratios in modified derivatives can be determined by UV/ vis spectroscopy (23, 113). Another method for quantifying ruthenium attached to histidines is to compare the reactions of the native and modified proteins with diethyl pyrocarbonate (146), which is a histidine specific reagent. 

Cyclodimerizations of conjugated enynes 22a-22e in the presence of perfluoro-tagged Pd catalyst were reported by Saito et al. [Eq. (6)] [28]. Reactions of enynes 22a-22e were carried out in toluene/hexane/perfluorodecalin with 1 mol% of Pd2(dba)j as palladium source and 8 mol% of perfluoro-tagged phosphane 1 giving the desired products (23a-23e) in moderate to good yield (43-78%). Recovery of the perfluoro-tagged catalyst was possible up to four times. However, IPC atomic emission analysis of the fluorous phase indicated that the concentration of the palladium species decreased significantly. 

Argon, Ar 39.948 8 Noble gas used to fill tight bulbs and as a plasma medium in inductively coupled plasma atomic emission analysis of elemental pollutants... 

Degradation products from both antimony-halogen based and nitrogen-phosphorus based flame retardants were studied using X-ray diffraction and atomic emission analysis. Evidence of the retardation mechanisms in use against combustion was obtained for each system and in each case emission of volatile combustion inhibitors at the degradation temperature of the polymer matrix was the critical factor. 11 refs BELARUS BELORUSSIA... 

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