摘要:

IntroductionThe accurate determination of environmentally (i.e., non-occupationally) and occupationally relevant trace and ultra-trace elements in human body fluids is an important prerequisite for the assessment of the present internal exposure of an individual, for prevention and control of pollution and for the diagnosis and treatment of adverse health effects. Up to now, the normal background levels of some relevant elements have still not been well known and further investigations are thus urgently needed, including the development of suitable analytical procedures and their application in the context of field studies in order to evaluate background levels for these elements in human body fluids.Up to date atomic absorption spectrometry (AAS) in the electrothermal (ET) or hydride generation (HG) mode is the most common analytical method for routine monitoring of environmentally or occupationally relevant metals in body fluids such as blood, serum and urine and in tissues. More and more inductively coupled plasma mass spectrometry (ICP-MS) is gaining popularity due to its multi-element capability, high sensitivity and wide dynamic range.1–5Detection limits obtained by ICP-MS can be up to three orders of magnitude better than those which are achievable by appropriate ET-AAS techniques.6,7Thus, ICP-MS even enables the determination of elements in body fluids which are not accessible to ET-AAS. Well known examples for this are the determination of U, Th, Mo, Pt, Pd, Ag, Au, Ti and Si in human blood, serum and urine.4,8,9However, ICP-MS suffers from several types of spectral and non-spectral interferences, which is the principal limitation of this method.10,11These interferences are especially serious in the analysis of complex matrices, such as human body fluids, containing high amounts of organic and inorganic matrix components. Using conventional quadrupole (Q‐)ICP‐MS instruments, an accurate determination of spectrally interfered elements is thus often impossible without extensive sample pretreatment including separation and preconcentration techniques. Many of these spectral interferences can today be overcome by sector-field (SF) ICP‐MS, which can be operated either in the low or in a higher resolution mode.1,2,7,12–14Whether an interfering signal can be separated from an analyte signal depends on the instrumental resolution, the mass difference between the analyte and interfering ion and the ratio of their intensities.1The performances of commercial SF-ICP-MS instruments are similar with respect to their maximum resolution of about 10 000.This mass resolution is, in practice, sufficient to separate the analyte ions listed inTable 1from many of the common spectral interferences by polyatomic and double-charged ions. However, the separation of isobaric overlaps is generally not possible because it requires a higher resolution, which cannot be obtained by today's commercial SF-ICP-MS instruments. Besides the capability of resolving the analyte signal from spectral interferences, further advantages of the SF-ICP-MS instruments over conventional Q-ICP-MS are the extremely low instrumental background of <0.2 ions s−1and their high transmission, which result in distinctly lower detection limits, typically ranging in the pg l−1range for non-interfered isotopes [in the low resolution (LR) mode].1,13,14Detection power of SF-ICP-MS is for most of the environmentally and occupationally relevant elements distinctly better than those achieved even by new generation Q‐ICP‐MS instruments.Relevant spectral interferences and required minimum resolution (m/Δm) for the determination of Al, V, Cr, Fe, Ni, Co, Cu and Zn in body fluidsIsotopeInterferenceRequired resolution27Al+12C14N1H+91951V+35Cl16O+257351V+37Cl14N+203759Co+42Ar16O1H+163052Cr+40Ar12C+237452Cr+35Cl16O1H+167252Cr+36Ar16O+236752Cr+38Ar14N+205452Cr+35Cl17O+189253Cr+37Cl16O+262653Cr+32S16O1H+181656Fe+40Ar16O+250158Fe+58Ni+27 99759Co+43Ca16O+287859Co+36Ar23Na+244458Ni+42Ca16O+286158Ni+58Fe+27 99760Ni+44Ca16O+305763Cu+40Ar23Na+279263Cu+31P16O16O+185265Cu+40Ar25Mg+317965Cu+31P17O17O+162264Zn+32S32S+426464Zn+32S16O16O+195364Zn+48Ca16O+349466Zn+132Ba2+249066Zn+32S17017O+164467Zn+134Ba2+266668Zn+136Ba22477Recently, so‐called Dynamic Reaction Cell (DRC) technology has been developed to overcome spectral interferences using quadrupole instruments. This reaction cell is placed between the ion lens and the analyzer of a conventional Q‐ICP‐MS. It has been demonstrated15,16that chemical reaction with reaction gases such as NH3inside the dynamic reaction cell reduces or even eliminates a number of common spectral interferences in Q‐ICP‐MS. The DRC technology is advantageous for spectrally interfered elements, such as Cr, Fe, Mn, Ni and V, but for other, non-interfered elements, such as Pt, Cd, Pb and Tl, this technology has no advantages over the standard Q‐ICP‐MS mode.15Detection limits given for diluted HNO3(1 + 10 v/v) range around 1 ng kg−1.16In complex matrices detection limits are expected to be distinctly higher due to the required sample dilution and additional spectral interferences originating from matrix elements. Another important tool to reduce some specific interferences and to improve sensitivity by up to a factor of 10 is the use of a shielded torch.17A device which shields the plasma torch from the induction coil reduces the secondary discharges in the interface region and enhances ion transmission. This technology can be applied in quadrupole as well as in sector field instruments.The purpose of this study was to evaluate the capabilities of SF-ICP-MS for the quasi-simultaneous routine determination of spectrally and non-spectrally interfered elements of occupational and environmental interest in human body fluids. The features of SF-ICP-MS will be compared with those of conventional AAS techniques. Recommendations for the choice of the appropriate analytical technique are given.

ISSN:0267-9477    

DOI:10.1039/a909056h

出版商:RSC    

年代:1999

数据来源: RSC