Control Multielement

Rossbach M, Ostapczuk P, Emons H (1998) Microhomogeneity of candidate reference materials Comparison of solid sampling Zeeman-AAS with INAA. Fresenius J Anal Chem 360 380-383. Rossbach M, Stoeppler M (1987) Use of CRMs as mutual calibration materials and control of synthetic multielement standards as used in INAA. J Radioanal Nud Chem Artides 113 217-223. Sargent M (1995) Development and application of a protocol for quality assurance of trace analysis. Anal Proc 32 71-76. 

Prange et al. [809,810] carried out multielement determinations of the stated dissolved heavy metals in Baltic seawater by total reflection X-ray fluorescence (TXRF) spectrometry. The metals were separated by chelation adsorption of the metal complexes on lipophilised silica-gel carrier and subsequent elution of the chelates by a chloroform/methanol mixture. Trace element loss or contamination could be controlled because of the relatively simple sample preparation. Aliquots of the eluate were then dispersed in highly polished quartz sample carriers and evaporated to thin films for spectrometric measurements. Recoveries (see Table 5.10), detection limits, and reproducibilities of the method for several metals were satisfactory. 

Harrison PR, Rahn KA, Dams R, et al. 1971. Areawide trace metal concentrations measured by multielement neutron activation analysis. Journal of the Air Pollution Control Association 21 563-570. 

The use of ICP-MS for the analysis of foods has been reviewed recently [270]. Food analysis can provide information on potentially toxic elements, nutrient elements, or geographical origin of the food. The application of ICP-MS to experimental nutrition has recently been reviewed [271]. The importance of quality control for multielement analysis of complex sample matrices like foods by ICP-MS was shown [272]. 

The temperature within our oven was controlled by a multielement air heater and proportional energy input control. Fluctuations were within =t0.5oC. and the samples were mounted on a rotating rack. To accelerate the aging, very thin specimens were used. In fact, the first goal... 

It should be also pointed out that the robustness of electrothermal atomization enables one to avoid the use of high dilution factors. The sensitivity of ET-AAS to a high percentage of dissolved salts, major elements and/or acids is relatively controllable. Manipulation can be also reduced. Calibration is therefore possible at concentrations where contamination phenomena can be better mastered. Multielement atomic spectrometers have additional advantages of saving time and resources by quantifying simultaneously Cd and Pb. 

Accordingly, it would be desirable for the alkaline solubilization sampling atomic spectrometric procedures to be accepted both as a routine quality control technique and/or as a screening approach in different processes involving foodstuffs. In this respect, the reduced sample manipulation, the low turnaround time and the relative low cost are primary merits. While single-element determinations using methods such as AAS will continue to play an important role in this Feld, multielement and multiisotope measurements will play an ever more important role in food science in the years to come. 

Summary. Ion beam techniques such as KBS are a good analytical tool for studying interface phenomena due to their multielement capability and the possibility of working on whole rock sections. Interesting information on the sorption mechanisms can be obtained from these studies the colloid surface coverage is low (less than one monolayer) the retention mechanisms are partly controlled by the electric charges developed at the surfaces (colloid, mineral) the colloid detachment rate is very low indicating an irreversible character with... 

Plasma emission spectrometry, especially ICP- and DCP-sources, has a fixed place in modern trace element analysis. In spite of the relatively small number of relevant elements detectable by these techniques for the biomedical and environmental fields of application, plasma emission spectrometry can deliver a lot of possibly important information. The main advantages are the multielement character of the technique (sequentially or simultaneously), nearly chemical interference free measurements, control of physical interferences, a relatively high level of accuracy and precision, high specificity, fast multielement determinations (especially in case of a simultaneous device), low sample consumption and in general a wide range of detectable elements (Table 13). 

Metals and alloys as well as the raw materials from which they are made are analyzed primarily by spectroscopic methods. The iron and steel as well as the aluminum industries rely on spectroscopic analysis in all steps of their processes. Many of the analyses are needed in a very short time thus these industries make wide use of multielement direct reading spectrometers to provide needed analytical data. It is important to control the composition of the molten metals before further processing and the direct reading spectrometers can supply routine analytical information in less than 2 min, something impossible with photographic recording or with chemical wet methods. Some control laboratories have direct readers capable of simultaneously determining 30 elements. 

Methods of quality control (QC) of convenience reagents vary according to type. Simple solutions are controlled by analysis and for standard solutions an accuracy of 0.1% is required wherever attainable. Multielement metal standards are prepared from high-purity starting materials that have been well analyzed, and are tested by a multielement method to ensure that no extraneous contamination has occurred. Prepared reagent mixtures for specific applications and test kits are subject to both QC analysis of the individual components and then, after preparation, have to meet performance criteria. 

The optical detection systems used in MIPs are the same as those used for other atomic spectrometers and can be either single or multichannel. Fourier transform-based spectrometers have also been used. Conventional optical systems are best designed if the plasma is viewed from the exit of the discharge tube, as is possible with the TMqio type cavity, rather than through the walls of the discharge tube, which become etched. The commercially available AED uses a computer-controlled silicon photodiode array detector which has multielement detection capability over segments of spectra. In recent years, MIP sources have also been investigated as ion sources for mass spectrometry. 

A second category of instrument is the simultaneous WD-XRF analyzer. This instrument is designed with a specified number (usually in the range 8-20) of individual fixed spectrometer channels , each optimized for the determination of a designated element. Multielement analysis is vmdertaken very rapidly by acquiring data simultaneously from all channels. Such instruments offer, therefore, high analytical productivity of benefit in production and quality control laboratories that are required to analyze the same sample-type on a routine basis. 

The catalyst preparation process is highly specific to generate a catalyst for a specific reaction and also with specific selectivity. A large body of literature describes such procedures/recipes. Control of the nature (crystal type, size) of the active species on the atomic level is considered to be an important factor. Thus, atoms of a given metal can exhibit different behavior since these have different properties (energy levels) at different locations in the crystallite. The multielement catalysts widely used in current practice are much more complicated since atoms of the different metals that... 

The XRF method is nondestructive, an important feature when the sample is available in limited amounts or when it is valuable or even irreplaceable, as in the case with works of art, antiques, rocks from the moon, or forensic samples. The nondestructive nature of XRF coupled with the fact that sample preparation may not be required means that direct multielement analysis can be performed in situ. Portable HH XRF analyzers are used in the field by geologists to study soil and minerals, to sort metal scrap, glass, and plastics at recycling centers, for quality control in steel plants, and to check incoming lots of material before unloading a ship or a truck (Figure 8.54). 

An example for the continuous use of a certified reference material (NIST SRM 1633 Fly Ash) as standard in the multielement comparator INAA is reported by Blackman and Bishop (2007). They have analyzed 32,000 samples in 1,750 irradiations over 29 years, looking for 35 elements. A standard clay co-analyzed as a control sample 311 times showed a 1 % coefficient of variance for several elements. 

The multielement character of AA implies that trace elements do not have to be individually separated it is sufficient to separate them into several groups or just remove the interfering components. Thus, chemical separation schemes are relatively simple and extremely high decontamination factors are not attained. When the recoveries are well controlled, separations need not necessarily be quantitative, although high yields are always desirable. For the determination of short-lived nuclides, fast separation procedures are of major concern. ... 

---