Magnesium analysis detection limits

The chemiluminescence technique has been used to determine trivalent chromium in seawater. Chang et al. [187] showed Luminol techniques for determination of chromium (III) were hampered by a salt interference, mainly due to magnesium ions. Elimination of this interference is achieved by seawater dilution and utilising bromide ion chemiluminescence signal enhancement (Fig. 5.7). The chemiluminescence results were comparable with those obtained by a graphite furnace flameless atomic absorption analysis for the total chromium present in samples. The detection limit is 3.3 x 10 9 mol/1 (0.2 ppb) for seawater with a salinity of 35%, with 0.5 M bromide enhancement. 

Nygaard [752] has evaluated the application of the Spectraspan DC plasma emission spectrometer as an analysis tool for the determination of trace heavy metals in seawater. Sodium, calcium, and magnesium in seawater are shown to increase both the background and elemental line emission intensities. Optimum analytical emission lines and detection limits for seven elements are reported in Table 5.8. 

Poor sensitivity of EDS for elements of low atomic number (especially sodium and magnesium) and an inability to detect elements with atomic numbers less than 10. The software package derived by the authors can derive quantitative analysis from a spectrum taking into account the inherent insensitivity of EDS to those elements whose atomic numbers approach the detection limit. 

Due to numerous interelemental matrix effects, matrix matched standards including a blank are necessary for accurate quantitative analysis. The detection limits for XRF are not as low as other spectrometric methods and a noticeable drop-off in sensitivity is noted for light elements such as magnesium. 

Fluorescence detection has been applied almost exclusively to the analysis of biomolecules. Applications for cations have been reported, however, including one that used indirect fluorescence for the analysis of a mixture of five alkali and alkaline earth metals52 within 4 min, and another that employed complexing equilibria to detect calcium, magnesium, and zinc53, directly. Detection limits on the order of 10 5 M for cations have been reported. 

Barium is present at very low concentrations in most environmental samples. Thus, in spite of the availability of a detection limit of only a few ng ml 1 by flame AES, the element is rarely determined by flame methods AAS with electrothermal atomization or ICP-AES is more commonly used. A notable exception is in the determination of the element in barium-rich geological deposits.8 Another exception is in the analysis of formation waters from offshore oil wells.9 However, in this matrix, inter-element interferences are encountered from alkali and alkali-earth elements. These could be effectively eliminated by the addition of 5 g 1 1 magnesium and 3 g 1 1 sodium as a modifier.9... 

Detecting trace elements in qualitative analysis is delicate because the counting time at each point is generally low (approximately 1 second instead of 100 seconds in quantitative mode). The detection limit depends on the element and the matrix in an alumina matrix, for example, these limits arc approximately 100 ppm for the majority of elements and 1% for sodium and magnesium. 

Analysis of the final Am02 product is shown in Table VI. A1 and Mg were below the detectable limits for these elements. The product met specifications of >95% Am02 with less than 0.5% Pu and less than 1% of any other single contaminant. The results of the preliminary lab scale extraction chromatography tests are shown in Table VII. Again, in spite of some analytical problems, it is evident that americium was decontaminated from aluminum and magnesium. A 7M HNO3 wash step is assumed to account for the americium loss. 

Graphite furnace atomic absorption spectrometry (GFAAS) is an excellent method to provide sub-ng/mL minimum detection limits [110]. Continuing advancements such as Zeeman correction, and stabilized temperature platform furnaces, have made GFAAS an effective analytical method for magnesium determination. Depending on the sample matrix, pretreatment can vary from direct analysis of fluids, to wet mineralization, dry ash, acid extraction, and by using PPRs (e.g., Triton X-100). 

As has been shown by initial comparison tests with activation analysis techniques under the auspices of Eurisotop and BCR Study Groups, good results are obtained with aluminium-silicon alloys - free from magnesium or only containing less than 3000 pg/g of it - if reducing fusion in a stream of carrier gas is employed in the manner suggested by Kraft and Kahles (47) for the analysis of unalloyed aluminium, with the sole difference that the reaction temperature is increased to 1950°C. Like for unalloyed aluminium, the oxygen contents reported are near the detection limit, and only increase to values of a few pg/g at silicon contents of 7 % or more. 

Numerous tertiary amines that also contain carboxylic acid groups form remarkably stable chelates with many metal ions. Ethylenediamine tetra-acetic acid (EDTA) can be used for determination of 40 elements by direct titration using metal-ion indicators for endpoint detection. Direct titration procedures are limited to metal ions that react rapidly with EDTA. Back titration procedures are useful for the analysis of cations that form very stable EDTA complexes and for which a satisfactory indicator is not available. EDTA is also used for determining water hardness the total concentration of calcium and magnesium expressed in terms of the calcium carbonate equivalent. 

Atomic Absorption Spectrometry. Flame atomic absorption spectrometry was adopted as the second method of analysis and since low volumes of air were sampled, only a limited number of elements were detected in the collected particles (calcium, copper, iron, magnesium, and zinc). Aluminum, cadmium, chromium, cobalt, lead, manganese, and nickel were not detected in any of the samples. This resulted in a limited... 

Another more serious defect of the EDS technique concerns the inherent sensititivy of the measurements for light (low-Z) elements. Several factors prevent the efficient detection of elements within the first row of the Periodic Table and limit information from the second. Instrumentally, the efficiency of the Li-drifted Si detector, its resolution, and the transparency of the Be window commonly used between the former and the system vacuum all concern us here. Detection sensitivities may be as low as 10", thereby limiting MDM at a given S/N, whilst the resolution (typically 150— 200 eV) may make the analysis of, for example, magnesium (hco = 1253.6 eV) in the presence of aluminium (hcu = 1486.6 eV) difficult. The presence of the Be window presents a more immediate practical problem in that characteristic Z-rays softer than, say, Na Kct may be absorbed, and this certainly precludes the analysis of the majority of the first-row elements (Li to F). 

The stability but also the catalytic activity of nickel-based perovskite was improved with a low amount of magnesium or rhodium in the structure. The solubility of Mg in the perovsldte structure is limited phases such as NiO and MgO are evidenced by XRD when >0.1 in LaNii Mg >,03 [24]. High catalytic activity was reached at 700 °C, with LaNio.9Mgo.1O3 under severe reaction conditions 10 mg of catalysts, CH4/CO2 50/50 ml/min without dilution gas. The CH4 and CO2 conversion were respectively equal to 57 and 67% and maintained during 15 h on stream even if carbon deposition was detected by thermogravimetric analysis at the end of the reaction (27 wt%). 

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