Lithium quantitative elemental analysis

The quantitative analytical aspects of organolithium compounds are considered in two sections, dedicated to elemental analysis of lithium (Section in.A) and determination of the compounds as such (Section in.B). 

In addition to the emission due to the test element, radiation is also emitted by the flame itself. This background emission, together with turbulence in the flame, results in fluctuations of the signal and prevents the use of very sensitive detectors. The problem may be appreciably reduced by the introduction into the sample of a constant amount of a reference element and the use of a dual-channel flame photometer, which is capable of recording both the test and reference readings simultaneously. The ratio of the intensity of emission of the test element to that of the reference element should be unaffected by flame fluctuations and a calibration line using this ratio for different concentrations of the test element is the basis of the quantitative method. Lithium salts are frequently used as the reference element in the analysis of biological samples. 

The analytical measurement of elemental concentrations is important for the analysis of the major and minor constituents of pharmaceutical products. The use of atomic spectroscopy in this regard has been the subject of several reviews (2,3,35,36). Metals are major constituents of several pharmaceuticals such as dialysis solutions, lithium carbonate tablets, antacids, and multivitamin-mineral tablets. For these substances, spectroscopic analysis is an important tool. It is indispensable for the determination of trace-metal impurities in pharmaceutical products and the qualitative and quantitative analysis of metals, essential and toxic, in biological fluids and tissues (37). Beyond this, several drugs which do... 

The human eye is a useful detector for qualitative analysis but not for quantitative analysis. Replacing the human eye with a spectrometer and photon detector such as a PMT or CCD permits more accurate identification of the elements present because the exact wavelengths emitted by the sample can be determined. In addition, the use of a photon detector permits quantitative analysis of the sample. The wavelength of the radiation indicates what element is present, and the radiation intensity indicates how much of the element is present. Flame atomic emission spectrometry is particularly useful for the determination of the elements in the first two groups of the periodic table, including sodium, potassium, lithium, calcium, magnesium, strontium, and barium. The determination of these elements is often called for in medicine, agriculture, and animal science. Remember that the term spectrometry is used for quantitative analysis by the measurement of radiation intensity. 

Mateus et al. (2005) have recently developed a code for the quantitative analysis of light elements in thick samples by PIGE. The method avoids the use of standards in the analysis, using a formalism similar to the one used for PIXE analysis, where the excitation function of the nuclear reaction related to the y-ray emission is integrated along the depth of the sample. To check the validity of the code, these authors have presented results for the analysis of lithium, boron, fluorine and sodium in thick samples. The experimental values of the excitation functions of the reactions Li(p, p yj Li, °B(p, ay ) Be,... 

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