Lithium metaborate fusion

The loss of platinum from the crucible is less during a lithium metaborate fusion than with a sodium carbonate fusion. 

Are there any alternative chemicals which can be used to eliminate hazards (e.g., the use of lithium metaborate fusion rather than hydrofluoric acid as a dissolution procedure) The protocol should include details of any required checks on the control measures to be adopted, and their frequency (e.g., cleaning of protective clothing, washing down of fume cupboards). 

The <0.063 mm fraction of till was analyzed by aqua regia and lithium metaborate fusion-nitric acid digestions ICP/ES and MS. 

Van Loon, J. C., and Parlssis, C. M., Scheme of silicate analysis based on the lithium metaborate fusion followed by atomic absorption spectrophotometry. The Analyst, 1969, 1057-1062. 

The total content of sediment base cations (Ca2+, Mg2+, K+, and Na+), as determined by lithium metaborate fusion (16), decreased down-core in both basins from 190 38 mequiv/100 g in the 0-2-cm interval to 160 32 mequiv/100 g in the 12-14-cm interval (Figure 7a). For any depth interval the difference between the basins was less than 5%, and the analysis of sediments for total base cations was not precise enough to confirm the differences between basins detected by other analyses. In contrast, the analyses... 

E. Lithium metaborate fusion attack for silicon determination in rock, soil or sediment... 

In the M procedure, the sample is fused with sodium carbonate, the cooled fusion mixture dissolved in HCl, filtered, diluted to volume, and stored in plastic screw-cap bottle. Two procedures are reported by the H procedures. One uses a lithium metaborate fusion followed by HNO3 dissolution. No filtration is indicated (this procedure is used only when silicon is to be determined). In the other H procedure, the sample is treated with HF, evaporated completely, and the residue taken up with HCIO4. 

Although acid attack is a classical means of dissolving silicate samples, the use of lithium metaborate fusion is a new departure, originating in the work of Ingamells [182] who showed that a clear aqueous solution could be easily and quickly prepared from silicates. Fluxes decompose most substances at the high temperature required for their use (500-1000 °C) and the high concentration of... 

The chemical compositions of the ancient Egyptian Blue samples (reported in the following section) were determined by atomic absorption spectrophotometry using the hydrofluoric acid digestion method together with the lithium metaborate fusion method for the silica determination (9). Some 20-30 mg of powder drilled from the objects was used for these analyses. Additionally, the arsenic concentrations were determined by x-ray fluorescence spectrometry. The precision of the analytical data was 1-2% for the major elements (>10% concentration) and deteriorated to 5-20% for the trace elements (<0.1% concentrations). However, due to the inhomogeneity of the material, variations in elemental concentrations (i.e., major, minor, and trace) of 10-15% can be expected within a single object. 

Verbeek, A.A., Mitchell, M.C. Ure, A.M. (1982) The analysis of small samples of rocks and soils by atomic absorption and emission spectroscopy after lithium metaborate fusion/nitric acid dissolution procedure. Analytica Chimica Acta 135, 215-228. 

The Benefits of the X Series 2 ICP-MS for the Analysis of Geological Samples Prepared Using the Lithium Metaborate Fusion Method, Thermo Scientific Application Note—40790, 2007, http //www.thermo.com/eThermo/CMA/PDFs/Articles/articles-File 2375.pdf. 

The commercial ores, beryl and bertrandite, are usually decomposed by fusion using sodium carbonate. The melt is dissolved in a mixture of sulfuric and hydrofluoric acids and the solution is evaporated to strong fumes to drive off siUcon tetrafluoride, diluted, then analy2ed by atomic absorption or plasma emission spectrometry. If sodium or siUcon are also to be determined, the ore may be fused with a mixture of lithium metaborate and lithium tetraborate, and the melt dissolved in nitric and hydrofluoric acids (17). 

Fusions with (a) sodium carbonate or fusion mixture, (b) borax and lithium metaborate, (c) alkali bifluorides, and (d) alkali hydrogensulphates (slight attack in the last case above 700 °C, which is diminished by the addition of ammonium sulphate). 

Substances which are insoluble or only partially soluble in acids are brought into solution by fusion with the appropriate reagent. The most commonly used fusion reagents, or fluxes as they are called, are anhydrous sodium carbonate, either alone or, less frequently, mixed with potassium nitrate or sodium peroxide potassium pyrosulphate, or sodium pyrosulphate sodium peroxide sodium hydroxide or potassium hydroxide. Anhydrous lithium metaborate has found favour as a flux, especially for materials containing silica 12 when the resulting fused mass is dissolved in dilute acids, no separation of silica takes place as it does when a sodium carbonate melt is similarly treated. Other advantages claimed for lithium metaborate are the following. 

Fusions with lithium metaborate are usually quicker (15 minutes will often suffice), and can be performed at a lower temperature than with other fluxes. 

For the preparation of samples for X-ray fluorescence spectroscopy, lithium metaborate is the preferred flux because lithium does not give rise to interfering X-ray emissions. The fusion may be carried out in platinum crucibles or in crucibles made from specially prepared graphite these graphite crucibles can also be used for the vacuum fusion of metal samples for the analysis of occluded gases. 

Fusions with lithium metaborate, 112 with sodium carbonate, 113 with sodium hydroxide, 113... 

Lithium metaborate (LiB02) fusion for glass, rocks, and soils. 

Most fusions use lithium tetraborate (Li2B407, m.p. 930°C), lithium metaborate (LiB02, m.p. 845°C), or a mixture of the two. A nonwetting agent such as KT can be added to prevent the flux from sticking to the crucible. For example, 0.2 g of cement might be fused with 2 g of Li2B407 and 30 mg of KI. 

Typically, these will be alloys, rocks, fertilisers, ceramics, etc. These materials are taken into solution using suitable aqueous/acid media, according to solubility hot water, dilute acid, acid mixtures, concentrated acids, prolonged acid digestion using hydrofluoric acid if necessary, alkali fusion (e.g. using lithium metaborate), Teflon bomb dissolution. Fusion and bomb methods are usually reserved for complex siliceous materials, traditionally reluctant to yield to solubilisation. 

Consider the case of determining alkaline and alkaline-earth concentrations. The catalyst samples where the matrix is alumina or a zeolite are reduced to a powder and dissolved in hydrochloric acid solution either by direct attack by high purity acids or after fusion with lithium metaborate. The choice of acids used to attack the samples depends both on their composition (alumina or aluminium silicate) and on the active elements present. Success of the method in forming a solution depends partly on the information available on the composition of the sample. If the presence of certain elements is not known, it may be necessary to test several methods prior to obtaining a satisfactory dissolution. 

The calibration is established from solutions prepared by diluting a solution of I 000 mg/1 of the element to be determined. When sample solutions are prepared using the fusion method, the reference solutions used for this analysis contain the same quantity of lithium metaborate as the sample solution. The origin of the calibration curve is determined by a blank test solution prepared in the same way as the standards, but without the element to be determined. 

Two additional hydrofluoric acid methods have been reported (1,2), and are similar to that described above. The method of Hughes et al. has also been the subject of two comparative studies relevant to the analysis of ceramics (2,31). Techniques that retain silicon have been discussed (1,2) and involve either fusion with lithium metaborate [or sodium carbonate (2)] or high pressure dissolution in a PTFE bomb. An alternative high pressure method, developed by Price and Whiteside (32), was evaluated in the course of this investigation but was found to be unreliable for stained glass of medieval composition in many experiments dissolution was incomplete. Attempts to modify the procedure by varying the prescribed dissolution parameters produced insufficiently consistent results although superior conditions were established (Table I). 

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used for the determination of most major and trace elements. The samples are fused in a Claisse semi-automatic fusion device in Pt-Au crucibles with lithium metaborate (4). The fusion product is dissolved in diluted HNO and brought to volume. For trace elements determination the sample is decomposed by HF, HNOg and HCIO. Scandium serves as an internal standard and is added to all samples and solutions. The instrument (product of Jobin Yvon, France)is calibrated using multi-element synthetic standards. The aqueous solutions are nebulized and injected into the heart of a plasma fire ball. A computerized multi-channel vacuum spectrometer has been programmed for multi-element analysis. 

Claisse Fusion Device. The detailed procedure is described by Botto (10). This isan automated device which simultaneously fuses six samples. In this procedure, the finely powdered sample was mixed with ten times its weight of lithium metaborate in a platinum crucible and heated at 950°C for 15 minutes. The melt was dissolved in either dilute HC1 or HNO and the elements of interest were then determined by AAS or ICPES. Phosphorus was determined from the same solution by a separate molybdenum blue colorimetric procedure. 

Claisse Fluxer Analysis - Lithium tetraborate or metaborate fusion for the dissolution of rocks has been in use for many years. The Claisse Fluxer fusion device simply makes this fusion automated. We have used the method in the past for the fusion of coal and fly ashes (10,13). Oil shales can be dissolved by this method without pre-ashing. Once the solution is prepared, it may be analyzed for the most part by ICPES or by AAS. Analysis of U.S.G.S. Devonian Ohio shale SDO-1 by fusion followed by AAS or ICPES measurements is illustrated in Table III. 

Whole ash analyses were performed using flameless atomic absorption spectrophotometric techniques. The lithium metaborate—nitric acid fusion techniques was used in the preparation of the sample for analysis of Ca, Mg, Na and K. Hydrofluoric—nitric acid dissolution was employed in the preparation of the samples for measurement of Fe, Mn, Cu, Pb, Zn and Cd. 

Some substances, such as silicates and oxides, are not always destroyed by the direct action of acid and heat. In these situations an alternative approach is required. Fusion involves the addition of a 10-fold excess of a suitable reagent (e.g. lithium metaborate or tetraborate) to a finely ground sample. The mixture is placed in a metal crucible, e.g. Pt, and then heated in a muffle furnace at 900-1000 °C. After heating (from several minutes to several hours) a clear melt should result, indicating completeness of the decomposition. After cooling, the melt is dissolved in HF (Table 27.3). This process can lead to a higher risk of contamination. 

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