Applications Of Solution Nebulization And Laser Ablation ICP-MS In Geosciences

This work describes the applications of solution nebulization and laser ablation inductively coupled plasma mass spectrometry in geosciences. Solution Nebulization Inductively Coupled Plasma Mass Spectrometry (SN-ICPMS) is used widely nowadays. It was used to monitor the background of clean labs and helped to find the source of impurities in ultra pure water and ultra pure acids in this study. Parameter optimization of a POEMS III ICP-MS was discussed in this work. The author designed and manufactured an Acid Digestion Teflon Bomb (ADTB) in order to digest geological samples. International reference materials were analyzed with the ADTB with satisfactory results.Excimer Laser Ablation Inductively Coupled Plasma Mass Spectrometry (ELA-ICPMS) is a newly developed strategy for direct solid sample micro analysis and zircon dating. In this paper an extensive study has been done and optimum instrumental parameters were obtained. Analysis of USGS rock glass standards BCR-2G, BHVO-2G and BIR-1G and NIST synthetic silicate glasses NIST 610, NIST 612 and NIST 614 show both relative standard deviations and relative deviation of the obtained values from recommended values better than 10%. In-situ single-grain zircon U-Pb dating was carried out by the ELA-ICPMS technique.1 Analysis of trace Elements of geological samples by SN-ICPMSImpurities in ultra pure water and acids were analyzed by SN-ICPMS. With careful analysis of tap water, distilled water, deionized water and ultra pure water, the Ag impurity is found to be derived from polyethene bottle, which should be cleaned with care. Antimony (121 and 123 amu) and iodine (127 amu) of ultra pure HNO₃ is still significant after sub-boiling distillation. They were difficult to be consumed for their low boiling points. Significant antimony (121 amu and 123 amu) in ultra pure HF was probably attributed to the corrosion of the glass torch and spray chamber by hydrofluoric acid, because the intensities of these masses in the 5% hydrofluoric acid were only twice of the intensities in the 0.5% solution. Signal at 85 amu in ultra pure HClO₄ should be emphasized since no corresponding signal is found at 87 amu. Because Rb has two isotopes with natural abundance for ⁸⁵Rb and ⁸⁷Rb being 72.15% and 27.85%, respectively, isobaric or polyatomic interference must exist at 85 amu.The orthogonal method can be used to predict the optimum instrumental conditions and to guide the optimizing operations. This simplifies the ICP-MS optimization. In general, the final optimum parameter combination used in an analysis can be obtained with fine adjustments of the preferred parameters derived from the orthogonal experiment. This method can also be used to study the relationship between the parameter settings and the signal intensity deflection to improve the analysis of elements with a limited mass range. Significant results are listed as follows: (1) the Lens 2 and Lens 3 voltage levels should be similar; (2) the Lens 4 voltage level should be lower than the Lens 2 and Lens 3 voltage levels; (3) the collector voltage level should be higher than the Lens 4 voltage level and close tothe aperture voltage level; and (4) the pole bias voltage level should be lower than the aperture and extractor voltage levels. It is also suggested that (1) the sampling depth should be set at about 6 mm; (2) the auxiliary gas-flow rate should be close to 1.0 L/min and the RF power to 1350 W; (3) the collector voltage should be higher than -9 V (Level 3); (4) the aperture voltage should be around -72 V (Level 3); and (5) the aperture, pole bias and extractor voltages exhibit either a "v" or a 'Vshape, which corresponds to an increased or decreased sensitivity. Following rule can be applied to obtain different signal intensity deflection: the higher is the nebulizer gas-flow rate, the higher is the sensitivity of the light elements, and vice versa; higher Lens 3 and lower Lens 4 voltages leads to a higher signal intensity over a higher mass range. A combined lower pole bias and higher extractor voltages have a similar effect.The author made a specially designed Teflon bomb to digest geological samples in a mixture of 1.5 mL HNO3, 1.5 mL HC1 and 0.02 mL HC1O4. The obtained analysis conducted over a period 19 months for international rock reference materials show good agreement with recommended values.2) In situ micro analysis by ELA-ICPMSELA-ICPMS optimum conditions are studied. Main conclusions are the following: (Dthe carrier gas flow rate is set at 0.55 0.77 L/min; (2) compromised laser frequency is set at 10 Hz; Q) laser energy is set at maximum energy of Complexl02. The working gas of the laser cell should be refilled when the energy is below 150 mJ (10 Hz); <3> the compromise laser ablation spot size is 60 um. ? the integration intervals of laser ablation signal is 30 60 s normally. ? Si, Al, Ti, and Ca are usually selected as internal standard elements. Si is used to calibrate Li, Be, Na, P, V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Cs, and Ba. Al, Ti and Mg are used to calibrate La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Cr, Ga, Y, Zr, Hf, Ta, Pb, Th and U. Ca is used to calibrate Na, Mg, Al, Si, P, Sc, Ti, Co, Cu, Sr, Nb, and rare earth elements. Q) Time of Quadruopole Settling Time and Dwell Time are set at 10 ms and 0.6 ms, respectively. ? the Sweeps/reading is set at 2 with consideration of micro information of geological samples and stability of signals.Analysis of several USGS and NIST reference glasses with ELA-ICPMS for 19 months show that the ELA-ICPMS can provide results with precision and accuracy comparable to SN-ICPMS.3. Single grain zircon dating by ELA-ICPMSInstrumental conditions were obtained after U-Pb fractionation study with NIST, USGS standard glasses and Harvard standard zircon 91500. (1) laser frequency is set at 8 Hz; (2) spot size is set at 60 Um; (3) Quadrupole Settling Time and Dwell Time are set at 12 ms and 0.6 ms, respectively; (4) Sweeps/reading is set at 3. Other conditions are the same as ELA-ICPMS analysis of trace elements.The Harvard Univeristy standard zircon 91500 and ANU standard zircon TEM were analyzed under the above optimum conditions. TIMS reference results on 91500 are 238U/206Pb=5.5813, 207Pb/206Pb=0.07488, 2O7Pb/235U=1.8502, 206Pb/238U=0.1792, and U-Pb age=1065.4 ± 0.6 Ma. Corresponding results from this study are 5.600, 0.0752, 1.85 and 0.179, Tera-Wasserburg Concordia age 1064+12/-9.7Ma (MSWD=0.86), and Conventional Concordia age 1064 +14/-9.9 Ma (MSWD=0.82). For TEM, SHRIMP reference results are 238U/206Pb=14.67998, 207Pb/2O6Pb=0.05582, 207Pb/235U=0.52425,206Pb/238U=0.06812 and U-Pb age= 417 + 20 Ma. These compare to the results ofthe present study: 14.784, 0.055, 0.51 and 0.068, Tera-Wasserburg concordia age 423+52A48 Ma (MSWD=0.44) and conventional concordia age 421 ± 24 Ma (MSWD=0.48). Therefore our ELA-ICPMS results on both zircons show excellent agreement with TIMS and SHRIPM values.