Inductively coupled plasma mass spectrometry (ICP-MS) is a new analytical and testing technology developed in 1980s. It is a new element/isotope analysis technology, which combines the high temperature (7000K) ionization characteristics of ICP with the advantages of sensitive and fast scanning of quadrupole mass spectrometer, and has a unique interface technology. Compared with various inorganic multi-element instrument analysis technologies at present, ICP-MS technology has the lowest detection limit, the widest dynamic linear range, high analysis precision, accuracy and speed. The linear dynamic range of concentration can reach 9 orders of magnitude, and the direct determination of 10- 12 to 10-6 can be realized. Therefore, ICP-MS is currently recognized as the most powerful analytical technology for trace and ultra-trace inorganic elements, which has been widely used in geology, environment, metallurgy, semiconductor, chemical industry, agriculture, food, biomedicine, nuclear industry, life science, material science and other fields. Especially for the determination of some challenging trace and ultra-trace elements, such as rare earth elements and platinum group elements in geological samples and titanium, thorium and uranium in environmental samples, ICP-MS method has advantages that other traditional analytical methods cannot meet. The main characteristics of ICP-MS are high sensitivity and low background. The detection limit of most elements is in the range of 0.000 x ~ 0.00 xng/ml, which is generally 2 ~ 3 orders of magnitude lower than that of ICP-AES, so trace and ultra-trace elements can be determined. Secondly, the mass spectrometry of elements is relatively simple and has little interference, and almost all elements on the periodic table can be determined. In addition, ICP-MS also has the ability of rapid isotope ratio determination. Different from other mass spectrometry technologies, ICP-MS technology does not need to seal the sample in the detection system and then vacuum, but simply introduces ICP under normal pressure, so it has the characteristics of convenient sample introduction and replacement, and is easy to be combined with other sampling technologies. For example, it can be combined with laser ablation, electrothermal evaporation, flow injection, liquid chromatography and other technologies to expand the application scope. These characteristics of ICP-MS make it very suitable for the analysis of trace and ultra-trace elements and the rapid analysis of some isotope ratios, so it has developed rapidly.
ICP-MS instruments have developed very rapidly. The early ICP-MS was mainly an ordinary quadrupole mass spectrometer (ICP-QMS). Subsequently, other types of plasma mass spectrometry techniques were introduced, such as high-resolution fan-shaped magnetic field plasma mass spectrometer (ICP-SFMS), multi-receiver plasma mass spectrometer (ICP-MCMS), time-of-flight plasma mass spectrometer (ICP-TOFMS), ion trap three-dimensional quadrupole plasma mass spectrometer (DQMS) and so on. When the sector magnetic field ICP MS is in high resolution mode, some polyatomic ion interference can be eliminated. In the low-resolution mode, it has the highest resolution and sensitivity, and the detection limit is generally 10 times or more lower than that of the quadrupole system. Multi-receiver sector magnetic field ICP-MS is a special instrument for isotope ratio analysis, and its isotope ratio analysis accuracy can reach 0.002%RSD. MC-ICPMS can not only measure the isotope ratio with the same accuracy as TIMS, but also analyze the isotopes of a wide range of elements in the periodic table, especially those that are difficult to analyze by TIMS.
The latest development of ICP-MS instrument structure mainly includes the following aspects:
Modification of (1) ion lens system
In the past, the ICP-MS ion focusing system basically adopted photon baffle or off-axis design, which effectively focused and transmitted analytical ions and excluded photons and neutral particles. Although the off-axis design is adopted locally, the trajectory of ion beam from plasma to interface, lens system and quadrupole mass spectrometer is the same direction, that is, horizontal direction. Since Varian introduced a new 90-degree reflective ion lens system in 2005, this design has made the focused transmission of analytical ions and the elimination of various interference components more efficient, thus reducing the background and improving the sensitivity. Therefore, in recent years, various instrument manufacturers have adopted similar right-angle reflection ion lens design in new instruments. For example, Thermo Fisher Scientific's latest iCAPQ ICP-MS is characterized by adopting a fast (right-angled positive ion deflection) lens technology-90 deflection ion optical path: the ions extracted from the interface are accelerated into the fast lens through the primary ion lens, so that the analyzed ions are effectively deflected 90 before entering the QCell and then pass through the fast lens, and other interference components are excluded from the system. The NexIONTM 300 introduced by PerkinElmer has a three-cone interface and a quadrupole ion deflector, and the ions to be analyzed deflect 90. Three-cone interface is to add a super truncated cone behind the sample cone and truncated cone. So that the vacuum pressure drop is more stable; Ion beam divergence is small; Prevent a large amount of matrix from entering mass spectrometry; And the sensitivity of low-quality components is improved.
(2) Mass spectrometry/mass spectrometry structure
Agilent 8800 triple quadrupole ICP-MS (ICP-QQ) is characterized by adding a quadrupole mass filter (Q 1), which is located in front of the conventional collision reaction tank and quadrupole mass filter (Q2), making it an MS/MS structure (also called cascade MS). In ICP-MS/ MS, Q 1, as a quality filter, only allows the target analytical quality to enter the unit and excludes all other qualities. This means that ions from plasma and sample matrix are blocked out of the cell, so even if the sample matrix changes, the cell conditions remain unchanged. Compared with conventional quadrupole ICP-MS(ICP-QMS), it improves the efficiency of eliminating interference in collision mode (using helium pool gas).
(3) Simultaneous determination of full spectrum by inductively coupled plasma mass spectrometry.
The SPECTROMS introduced by Germany's Spike Spectro Analytical Instrument Company is characterized by an ICP-MS mass spectrometer with a mass range of 6Li-238 U. The core technologies of this instrument are Mattauch-Herzog fan-shaped field mass analyzer and a unique detector with full mass spectrum synchronous capture capability. Mattauch-Herzog dual-focus fan-field mass spectrometer can focus all ions on the same focal plane at the same time, so all mass spectra can be captured by using a flat detector without scanning or peak skipping measurement. The new DCD detector is a linear array with a length of12cm and 4,800 channels. Each channel has two working modes of high and low gain, and an average of 20 channels detect an isotope. Therefore, the measurement time has nothing to do with the number of elements to be measured, and the analysis speed is fast; Real-time internal standard improves the accuracy and precision of analysis; It is more suitable for full mass spectrometry measurement of pulse signals and improves the accuracy of isotope ratio measurement.
Second, the scope of application and application examples
ICP-MS is a mature element and isotope analysis technology, which is widely used in the analysis of geological samples. At the same time, it also involves many industries such as environment, geology, metallurgy, clinical medicine, biology, food, semiconductors and materials.
(1) Determination of Rare Earth Elements in Uranium-bearing Materials by Inductively Coupled Plasma Fan-field Mass Spectrometry (ICP-SFMS)
Zolt Wall et al. (20 10) determined trace lanthanides in uranium-bearing materials by inductively coupled plasma fan-field mass spectrometry (ICP-SFMS). This method is novel and simple. Lanthanides were selectively extracted and separated by TRUTM resin chromatography, and then analyzed by ICP-SFMS. The detection limit of this method is less than pg/g (2 orders of magnitude higher than that of the method without chemical separation). The validity of this method is verified by the determination of reference materials. This method can be used to analyze the mass fraction of uranium in enriched uranium (yellow cake).
(2) NexION 300 inductively coupled plasma mass spectrometer
2065438+00 The stability, flexibility and performance of NexIONTM 300 introduced by Perkin Elmer Company are unprecedented in inductively coupled plasma mass spectrometer, which represents the first truly revolutionary industrial progress in recent years. NexION 300 system adopts patented Universal Cell Technology (TM) (UCT), which is the only system with three interference cancellation modes: standard, collision and reaction. These three modes enable scientists to choose the appropriate detection mode for their special applications when solving complex problems. NexION's standard model can be used for simple routine analysis. Collision mode is suitable for semi-quantitative analysis, environmental sample monitoring and unknown object analysis. By using patented DRCTM technology in reaction mode, the best detection limit can be obtained, even for elements and substrates that are particularly difficult to detect, such as those in semiconductor testing. NexION 300 ICP-MS can be combined with chromatography to analyze the forms of elements. The system can more accurately separate and detect the toxicity, bioavailability, metabolism and environmental migration of elements.
Three. sources of information
/Catalog/Family/ID/NexION
Zsolt varga, Robert Kathona, Zsolt steffen and others. Determination of rare earth elements in uranium? Determination of bearing materials by inductively coupled plasma mass spectrometry. Alanta, 80(5): 1744~ 1749