Lithium analytical technique

D. Fry, Lithium-analytical techniques, Ther. Drug. Monit., 3 217-223(1981). 

Lithium Borates. Lithium metaborate [13453-69-5], LLBO2 2H20, is prepared from reaction of lithium hydroxide and boric acid. It is used as the fluxing agent for the matrix for x-ray fluorescence analytical techniques and in specialty glasses and enamels. The anhydrous salt melts at 847°C. 

Early workers had to strnggle with serious lithium fractionation effects during mass spectrometric analysis. Today most workers use the multicollector sector ICP-MS technique first described by Tomascak et al. (1999). Improvements of the analytical techniques in recent years have lead to an accuracy better than 0.3%o. Unfortunately, there are no internationally accepted Li isotope values for rocks or waters. James and Palmer (2000) have determined nine international rock standards ranging from basalt to shale relative to the so-called NIST L-S VEC standard. 

The introduction of atomic absorption spectroscopy has resulted in major advances in the rapid analysis of many elements. Initially, atomic absorption was applied only to aqueous systems or to materials that could be readily solubilized. There are methods to analyze major elements in such complex materials as silicates and vitreous siliceous coal ashes (1-5). More recently, lithium metaborate has been reported to be a good fluxing agent (6) and has also been used in conjunction with atomic absorption analysis in silicate analysis (7). This paper describes a lithium tetraborate-atomic absorption analytical technique which is being used to analyze coal ash. 

The determination of the nitrogen content in different cereal grains represents a nice example 66,67). The flour of the grain was mixed with 10% of lithium fluoride. The relative integrals Fn and Ff obtained are now plotted against the nitrogen content CN determined by classical analytical techniques (Fig. 11). The bent slope of the curve can be easily explained even with a crude picture. The integral F is proportional to the intensity of the photoelectron beam / ... 

Based on various approaches, analytical techniques, calculations and available samples, the average lithium concentration in Magnox RPV steel is considered to be < 1 ng g and estimated as 0.4 0.2 ng g (IB)... 

The use of flame photometry as a quantitative tool can be traced to work by Kirchhoff and Bunsen in the early 1860sJ Its modern history begins, however, in the 1940s, when instruments became available that successfully addressed the problems of reproducible sample introduction and detection. Flame photometry soon developed into a reliable analytical technique for the determination of several cations of pharmaceutical interest, notably sodium, potassium, and lithium. The technique is useful in the analysis of bulk drugs, dosage forms, and clinical samples such as blood and urine. 

The availability of high flux thermal neutron irradiation facilities and high resolution intrinsic Ge and lithium drifted germanium (Ge(Li)) or silicon (Si(Li)) detectors has made neutron activation a very attractive tool for determining trace elemental composition of petroleum and petroleum products. This analytical technique is generally referred to as instrumental neutron activation analysis (INAA) to distinguish it from neutron activation followed by radiochemical separations. INAA can be used as a multi-elemental method with high sensitivity for many trace elements (Table 3.IV), and it has been applied to various petroleum materials in recent years (45-55). In some instances as many as 30 trace elements have been identified and measured in crude oils by this technique (56, 57). 

Accurate measurements of the concentrations of trace elements on atmospheric particulates are difiicult enough to make in polluted urban atmospheres but even more so in clean marine or polar atmospheres because of the minute quantities of material that can be collected in a reasonable time. For these measurements, one needs a sensitive analytical technique that is free from interference by other elements present. Recently, the use of lithium-drifted germanium [Ge(Li)] y-ray detectors in neutron activation analysis has greatly improved analytical sensitivities and accuracies for such studies (J). 

After the first qualitative studies of lithium-, sodium-, calcium-, and silver-halides and other inorganic salts with complex anions had revealed the types of ion occurring in FD mass spectra and the high sensitivity of the method for metal cations had been demonstrated the principal question arose whether quantitative data could be obtained. If so, it was essential in the use of FDMS as an analytical technique for metals to evaluate the sensitivity, precision and accuracy for these determinations. Since pilot tests showed an extraordinary sensitivity for cesium the first approach to the quantitive determination of metals by FD was started with this alkali metal. 

In view of the influence of a complex matrix on the FD determination, e.g. in physiological fluids and tissues, and the importance of the use of lithium in medicine a further step was to exploit the utility of FDMS in combination w th signal accumulation and stable isotope dilution (internal standard) in this field. Lithium salts are used in the chemotherapy of manic-depressive psychoses . The transport phenomena of lithium through cell membranes and the mode of therapeutic action in elevated lithium levels are areas of biomedical research which are of special interest for the therapy of certain affective disorders. Concerning the accurate determination of very small lithium concentrations in the range of the normal physiological level, there is a special need for a reliable analytical technique, in particular, if only microliters of the sample are available. 

PIGE is a rapid, non-destructive technique that is employed in the analysis of light elements such as lithium (10-100 ppm limit of detection), boron (500-1000 ppm limit of detection), and fluorine (1-10 ppm limit of detection), which are often difficult to determine by other analytical means. Because the technique is based upon specific nuclear reactions, the sensitivity of PIGE varies greatly from isotope to isotope, and this non-uniformity of sensitivity has limited its widespread use as a complementary technique to micro-PIXE. 

The introduction of high-resolution, high-efficiency /-ray detectors composed of lithium-drifted germanium crystals has revolutionised /-measurement techniques. Thus, /-spectrometry allows the rapid measurement of relatively low-activity samples without complex analytical preparations. A technique described by Michel et al. [25] uses Ge(Li) /-ray detectors for the simultaneous measurements of 228radium and 226radium in natural waters. This method simplifies the analytical procedures and reduces the labour while improving the precision, accuracy, and detection limits. 

Flame photometry is the name given to the technique that measures the intensity of the light emitted by analyte atoms in a flame. It is the oldest of all the atomic techniques. It is not highly applicable because of the low temperature of the flame. Only a handful of elements can be measured with this technique, including sodium, potassium, lithium, calcium, strontium, and barium. The technique was formerly used... 

LA-ICP-MS was used for in situ determination of ultratrace elements in quartz. The analytical protocol included the following elements Al, Ba, Be, Cr, Ee, Ge, K, Li, Mg, Mn, Pb, Rb, Sr, Th, Ti and U . Apphcation of the LA technique to heterogeneous samples usually requires preparing a homogeneous glass by fusing with lithium borate . A difficulty encountered with multi-element LA-ICP-MS analysis is the absence of standards... 

Siliceous materials—Si, Al, Fe, Ti, Ca, Mg, Na, K, Mn, Ni, Ba, Ag, Au, Ca, Cr, Cu, Ga, In, Mo, Sb and Zn—may be analyzed by a lithium tetraborate fusionr-acid dissolution technique using atomic absorption spectroscopy. Mercury, tin, and lead volatilize by this technique, and gold and silver in concentrations above 0.5 wt% cannot be held in solution. Coal ash is preconcentrated prior to analysis, and there is possible silica interference. Analytical results, where possible, are compared statistically with other reported values. 

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