Multielement determination

Itoh, A., Hamanaka, T., Rong, W., Ikeda, K., Sawatari, H., Chiba, K., and Haraguchi, H., Multielement determination of rare earth elements in geochemical samples by liquid chromatography/inductively coupled plasma mass spectrometry, Anal. Sci., 15, 17, 1999. 

Activation analysis is based on a principle different from that of other analytical techniques, and is subject to other types of systematic error. Although other analytical techniques can compete with NAA in terms of sensitivity, selectivity, and multi-element capability, its potential for blank-free, matrix-independent multielement determination makes it an excellent reference technique. NAA has been used for validation of XRF and TXRF. 

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. 

This analytical method, based on TXRF, enables a large number of trace elements to be determined simultaneously. The range is suitable for different areas of the sea. The motivation to use TXRF resulted mainly from the characteristic features of the method its high detection power, its universal calibration curve, which eliminates the need for matrix-dependent standard samples or standard-addition procedures, the simple preparation of the sample films, and of course the possibility of multielement determination. 

A. A. Momen, G. A. Zachariadis, A. N. Anthemidis and J. A. Stratis, Use of fractional factorial design for optimisation of digestion procedures followed by multielement determination of essential and non-essential elements in nuts using ICP-OES technique, Talanta, 71(1), 2007, 443 51. 

E. M. Seco-Gesto, A. Moreda-Pineiro, A. Bermejo-Barrera and P. Bermejo-Barrera, Multielement determination in raft mussels by fast microwave-assisted acid leaching and inductively coupled plasma-optical emission spectrometry, Talanta, 72(3), 2007, 1178-1185. 

C. Pena-Farfal, A. Moreda-Pineiro, A. Bermejo-Barrera, P. Bermejo-Barrera, H. Pinochet-Cancino and I. De-Gregori-Henriquez, Ultrasound bath-assisted enzymatic hydrolysis procedures as sample pretreatment for multielement determination in mussels by inductively coupled plasma atomic emission spectrometry, Anal. Chem., 76(13), 2004, 3541-3547. 

Depth profile of elements in seawater near hydrothermal vents. [From T. Akagi and H. Haraguchi, Simultaneous Multielement Determination of Trace Metals Using W mL of Seawater by Inductively Coupled Plasma Atomic Emission Spectrometry with Gallium Coprecipitation and Microsampling Technique Anal. Chem. 1990, 62.81.]... 

Multielement determination (sequential or simultaneous) faster analysis time minimal chemical interaction detection limits and sensitivity fall in between that of flame and graphite furnace measurements. 

Multielement determination sensitivity and detection limits exceptionally good (over 100 times greater than furnace techniques for some metals) isotopes also may be measured also has the capability to determine nonmetals (at a much lower sensitivity) broad linear-working range high cost. 

Because of its versatility and productivity, ICP-OES is one of the most useful techniques in instrumental element analysis. The multielement determination capacity of this technique enables it to deal with the basic workload in many routine laboratories. Complete information on all aspects relating to ICP-OES can be found in a few monographs.20-22... 

ICP-MS is an attractive technique for multielement determinations. In addition, it allows isotope ratio measurements31 and isotope dilution analysis30 to be carried out. The concepts related to these approaches are, however, beyond the scope of this chapter the reader will find full details in the literature.3031... 

Another factor which influences the speed in performing an analysis is calibration of the instrument. Calibration is especially time-consuming in cases where different elements are run on every analysis but even in cases where the same elements are determined time after time, the frequency of instrument calibration required to maintain a desired level of accuracy is an important consideration. Since manual data collection is not feasible in multielement determinations, the ideal system would undoubtedly be computerized. The computer would handle all data collection steps, the construction of calibration curves by mathematical curve-fitting methods, and the calculation of concentrations from these curves. 

The evolution of detection systems suitable for multielement determinations has proceeded along two basic lines of development as indicated in Figure 1. One line of development is based upon dispersive systems. Dispersive systems are all multichannel devices which may be further classified as temporal or spatial devices. In the temporal approach, the measurement of intensities in different resolution elements is separated in time. The spatial approach uses detectors which are separated in space. 

Because different elements have different spectrochemical properties, optimum analytical conditions may vary from element to element (69,70). Since all elements are determined simultaneously with an image detector spectrometer, compromise analytical conditions must be employed. Brost, et al. (71 ) have described a response parameter which can be used to determine the optimum compromise analytical conditions. Because the optimum compromise analytical conditions for a given determination depend on the expected analytical concentrations of the elements present in the sample, meaningful multielement detection limits cannot be reported without reference to a particular sample type. The many reported multielement detection limits which appear in the literature simply indicate the detection limits obtained under a particular arbitrary set of conditions, and do not necessarily represent the detection limits obtainable under optimum analytical conditions for a particular sample type. Thus the detection limits achieved in an actual multielement determination are more often likely to be compromise-limited rather than instrument-limited. 

Simultaneous Multielement Determinations by Atomic Absorption and Atomic Emission with a Computerized Echelle Spectrometer/Imaging Detector System... 

Comparisons of results. Experiments were carried out to evaluate effects of compromise conditions on sensitivities of the elements in the two groups discussed earlier. Near optimum conditions were established for each element determined individually, and the sensitivity of that element under the optimum conditions is compared with the sensitivity obtained with compromise conditions used for multielement determinations. Results are presented in Table X for these comparisons. 

The ICP-MS has several analytical attractions including very low detection limits [parts per billion to parts per trillion (ppb to ppt) levels], a large linear dynamic range, relatively simple spectra, excellent stability, multielement determination capability, and ability to measure isotopic abundances. Disadvantages are mainly due to the formation of polyatomic interferences from the plasma gas, entrained gases, and matrix elements such as Cl [16]. 

H. Matsuura, A. Hokura, F. Katsuki, A. Itoh, Multielement determination and specia-tion of major-to-trace elements in black tea leaves by ICP-AES and ICP-MS with the aid of size exclusion chromatography, Anal. Sci., 17 (2001), 391-398. 

EUTRON ACTIVATION ANALYSIS IS A VERY SENSITIVE TECHNIQUE for trace element determinations in various samples. If there are no elements that mutually interfere, the purely instrumental version of this method is often chosen for its established advantages such as accuracy, speed, sensitivity, simultaneous multielement determination, and sample preservation (1). For these reasons, instrumental neutron activation analysis (INAA) was applied to samples taken from a series of metal-working residues excavated at Tel Dan, Israel, from 1985 to 1986. 

Inductively coupled plasma-atomic emission spectrometry was investigated for simultaneous multielement determinations in human urine. Emission intensities of constant, added amounts of internal reference elements were used to compensate for variations in nebulization efficiency. Spectral background and stray-light contributions were measured, and their effects were eliminated with a minicomputer-con-trolled background correction scheme. Analyte concentrations were determined by the method of additions and by reference to analytical calibration curves. Internal reference and background correction techniques provided significant improvements in accuracy. However, with the simple sample preparation procedure that was used, lack of sufficient detecting power prevented quantitative determination of normal levels of many trace elements in urine. 

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