Proton Induced X-Ray Emission Spectrometry

ICP-AES=inductively coupled plasma-atomic emission spectrometry Mg(N03)3=magnesium nitrate MIBK=methylisobutyl ketone MS=mass spectrometry PIXE=proton-induced X-ray emission spectrometry XRF=X-ray fluorescence analysis WM-AES=wavelength-modulated atomic emission spectrometry... 

Simonoff M, Llabador Y, Hamon C, et al. 1984. Extraction procedure for the determination of trace chromium in plasma by proton-induced X-ray emission spectrometry. Anal Chem 56 454-457. 

Many nuclear techniques have been introduced into the field of analytical chemistry. This chapter focu on radioanalytical methods with tlie exc j on of radiotracers, used to correct for separation yield in analytical procedures, and the radioreagent technique, based on quantitative and stoichiometric reaction of an elmnent of interest. Instrumental methods such as radioactivation analysis and proton-induced X-ray emission spectrometry are also powerful nuclear analytical techniques, but they also must fall outside the scope of this short treatment. Then, the modem trends in radio-analytical methods are described, which feature autonomous analytical methods with a novel combination of chemical procedures and radioisotope techniques. 

To measure Pb concentrations in small particles such as aerosols, or to study the variation in Pb concentrations within sohds such as mineral grains, there is a range in available techniques such as micro-beam XRF (including synchrotron methods), proton induced X-ray emission spectrometry (PIXE), secondary ionization mass spectrometry (SIMS), and laser ablation ICP-MS (LA-ICP-MS). These methods have been used for high spatial resolution even in 3-D, as well as for rapid analyses of biological or geological structures growing incrementally [39-43] or small, specihc phases [44]. 

S.A.E. Johansson Proton-induced X-ray emission spectrometry - state of the art. Fresenius Z. Anal. Chem. 324, 635 (1986)... 

The determination of cesium in minerals can be accompHshed by x-ray fluorescence spectrometry or for low ranges associated with geochemical exploration, by atomic absorption, using comparative standards. For low levels of cesium in medical research, the proton induced x-ray emission technique has been developed (40). 

There are two principal sources of reliable partitioning data for any trace element glassy volcanic rocks and high temperature experiments. For the reasons outlined above, both sources rely on analytical techniques with high spatial resolution. Typically these are microbeam techniques, such as electron-microprobe (EMPA), laser ablation ICP-MS, ion-microprobe secondary ion mass spectrometry (SIMS) or proton-induced X-ray emission (PIXE). 

Principles and Characteristics Particle-induced X-ray emission spectrometry (PIXE) is a high-energy ion beam analysis technique, which is often considered as a complement to XRF. PIXE analysis is typically carried out with a proton beam (proton-induced X-ray emission) and requires nuclear physics facilities such as a Van der Graaff accelerator, or otherwise a small electrostatic particle accelerator. As the highest sensitivity is obtained at rather low proton energies (2-4 MeV), recently, small and relatively inexpensive tandem accelerators have been developed for PIXE applications, which are commercially available. Compact cyclotrons are also often used. 

XRD, X-ray diffraction XRF, X-ray fluorescence AAS, atomic absorption spectrometry ICP-AES, inductively coupled plasma-atomic emission spectrometry ICP-MS, Inductively coupled plasma/mass spectroscopy IC, ion chromatography EPMA, electron probe microanalysis SEM, scanning electron microscope ESEM, environmental scanning electron microscope HRTEM, high-resolution transmission electron microscopy LAMMA, laser microprobe mass analysis XPS, X-ray photo-electron spectroscopy RLMP, Raman laser microprobe analysis SHRIMP, sensitive high resolution ion microprobe. PIXE, proton-induced X-ray emission FTIR, Fourier transform infrared. 

GPC (total radioactive strontium) = beta gas proportional counter Bq = Becquerel dpm = disintegrations per minute EDTA = ethylenediamine tetraacetic acid GFAAS (total strontium) = graphite furnace atomic absorption spectroscopy ICP-AES (total strontium) = inductively coupled plasma atomic emission spectroscopy ICP-MS (isotopic strontium composition) = inductively coupled plasma-mass spectrometry LSC (isotopic quanitification of 89Srand 90Sr) = liquid scintillation counting pCi = pico curies (10-12 curies) PIXE (total strontium) = proton induced x-ray emission TMAH = tetramethylammonium hydroxide TNA (total strontium) = thermal neutron activation and radiometric measurement TRXF (total strontium) = total-reflection x-ray fluorescence... 

Bearse, R.C., Close, D.A., Malanify, J.J., and Umbarger, C.J. (1974). Elemental analysis of whole blood using proton-induced X-ray emission. Anal. Chem., 4 , 499-503 Berman, E. (1980) Toxic metals and their analysis, Heyden, London, Philadelphia, Rheine Brown, A.A., and Taylor, A. (1984) Determination of copper and zinc in serum and urine by use of slotted quartz tube and flame atomic absorption spectrometry. Analyst, 109. 1455-1459... 

Although no sharp lines can be drawn between nuclear and non-nuclear techniques (see De Goeij and Bode, 1997 for a review), the principle of the nuclear technique says that the analytical information on element and concentration originates from the nucleus and not from the atom. As such, chemical binding, chemical compound or matrix composition has no essential influence on the accuracy of the results (Bode and Wolterbeek, 1990 De Goeij and Bode, 1997). It should be noted here that although techniques such as particle/proton induced X-ray emission (PIXE) and X-ray fluorescence spectrometry (XRF) are basically derived from the behaviour of inner orbital electrons rather than the nucleus itself, they are often counted as a nuclear technique, primarily because inner orbital electrons do not predominate in the characteristics of the atom s chemical behaviour (but see also De Goeij and Bode, 1997 for NMR and Mdssbauer techniques). 

Inductively coupled plasma-mass spectrometry (CE/ICP-MS) Proton-induced X-ray emission (PIXE)... 

Direct determination of solids may be performed by, e.g.. X-ray fluorescence spectrometry, or by arc or spailr emission spectrometry in case of powders. For special applications many surface techniques are available such as proton-induced X-ray emission (PIXE) and laser microprobe emission spectrometry (LMA). In the case of determination of trace elements on clinical material, however, most of these direct methods have detection limits that are too high to be useful. Moreover, as some of these methods are cormected to an accelerator or electron microscope, usage is somewhat limited for routine determination. 

Several different methods have been utilized for measuring iron in these biological samples. However, spectrophotometry is the most widely used because it does not require unusual equipment and is readily amenable to automation. Atomic absorption spectrometry is effectively used for tissue and urine analyses [33-35], but unreliable results are obtained with serum due to sensitivity limitations as well as matrix and hemoglobin interferences [35]. Other methods utilizing inductively coupled plasma emission spectroscopy [36], coulometry [37], proton induced X-ray emission [38], neutron activation analysis [39], radiative energy attenuation [40], and radiometry with Fe [41] have been described but, with the exception of coulometry, have not become standard procedures in the clinical chemistry laboratory, inasmuch as sophisticated and expensive instrumentation is required in some instances. However, some of them, e.g., neutron activation, may be the method of choice for definitive accurate analysis. 

A variety of analytic techniques currently are used to provide chemical characterizations of archaeological materials. These techniques which include instrumental neutron activation analysis (INAA), X-ray fluorescence (XRF), proton induced X-ray emission (PIXE), X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma-atomic emission )ectroscopy (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-... 

Figure 1.13 Selected analytical techniques used for metallomics studies. ICP-OES, inductively coupled plasma optical emission spectroscopy, ICP-MS, inductively coupled plasma mass spectrometry LA-ICP-MS, laser ablation ICP-MS XRF, X-ray fluorescence spectroscopy PIXE, proton induced X-ray emission NAA, neutron activation analysis SIMS, secondary ion mass spectroscopy GE, gel electrophoresis LC, liquid chromatography GC, gas chromatography MS, mass spectrometry, which includes MALDI-TOF-MS, matrix-assisted laser desorption/ ionization time of flight mass spectrometry and ESI-MS, electron spray ionization mass spectrometry NMR, nuclear magnetic resonance PX, protein crystallography XAS, X-ray absorption spectroscopy NS, neutron scattering.

Figure 1 Energy dispersed X-ray spectra from the same sample excited by 20 keV electrons (top) and 2.5 MeV protons (bottom). The enhancement of the detection limit for the trace elements caused by the absence of primary Bremsstrahlung in the PIXE spectrum can be seen clearly. Reproduced with permission of Wiley from Johansson SAE, Campbell JL and Malmqvist KG (1995) Particle-Induced X-ray Emission Spectrometry. New York Wiley.

Microprobe techniques, and their detection limits (given in mgkg ), that have been applied to Al localization include energy dispersive (electron probe) X-ray microanalysis (20), wavelength-dispersive X-ray microanalysis, electron energy loss spectrometry (500), proton probe nuclear microscopy (10), resonance ionization mass spectrometry (3), secondary ion mass spectrometry (1), laser microprobe mass spectrometry (1) and micropartide-induced X-ray emission (Yokel 2000). 

As examples of Ti measurements, the application of ICP-atomic emission spectrometry to the analysis of bone [14], of proton nuclear activation (PNA) to serum [8], and of particle-induced X-ray emission (PIXE) to lung tissue [15] are described in Sec. 4.2. The authors of these studies report measurements at the level of 0.2-0.5 p.g/g in bone, 10 xg/g in lung, and 90 p.g/liter in serum. However, it must be stressed that there is insufficient comparative data to coimnent on the accuracy of these results. Further, these were all multielement investigations and sampling procedures were not specific to Ti. 

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