Henry P. Longerich

Inter-laboratory note. Laser ablation inductively coupled plasma mass spectrometric transient signal data acquisition and analyte concentration calculation

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) produces complex, time-dependent signals. These require significantly different treatment both during data acquisition and reduction from the more steady-state signals produced by solution sample introduction. This paper discusses, in detail, data acquisition and reduction considerations in LA-ICP-MS analysis. Optimum data acquisition parameters are suggested. Equations are derived for the calculation of sample concentrations and LOD when time-resolved data acquisition is employed, sensitivity calibration is obtained from reference materials with known analyte concentrations and naturally occurring internal standards are used to correct for the multiplicative correction factors of drift, matrix effects and the amount of material ablated and transported to the ICP.

ICP-MS — A powerful tool for high-precision trace-element analysis in Earth sciences: Evidence from analysis of selected U.S.G.S. reference samples

Abstract Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful analytical technique, with considerable application to geochemistry. In this paper, we demonstrate the power of ICP-MS as a tool in petrogenetic studies. Data for 28 elements in seven U.S.G.S. basalt and andesite reference samples (AGV- 1 , BCR- 1 , BHVO- 1 , BIR- 1 , DNC- 1 , W- 1 and W- 2 ) are presented. Accuracy and precision (standard deviation) for 26 of these elements is either excellent ( A detailed description of the ICP-MS technique we have developed is given. A simple HF-HNO 3 dissolution in screwtop Teflon® bombs was used for sample preparation. ICP-MS instrumental sensitivity was measured by external solutions, with surrogate calibration for 4 elements. Matrix correction was made by use of standard addition. Naturally occurring internal standards (Rb, Y, Ce and Pb) were used to correct for instrumental drift between sample and spiked-sample measurements. We report data for the elements: Li, Cs, Rb, Sr, Ba, Zr, Hf, Nb, Ta, Y, Sc, U, Th, Pb and all 14 of the REE. In addition, the procedure acquired data for Be, Mo, W, Tl and Bi. Many elements in this array are crucial for the evaluation of petrogenetic models and source tracing. Herein lies the real power of ICP-MS — one technique, one dissolution, small sample size, good limits of detection, good to excellent accuracy and good precision for many geochemically important elements.

Inductively coupled plasma-mass spectrometric analysis of geological samples: A critical evaluation based on case studies

Inductively coupled plasma-mass spectrometry (ICP-MS) is a relatively new and promising analytical technique, with the potential to be an excellent analytical tool in earth sciences. In this paper, we provide an overview of the use of ICP-MS in earth sciences, based on our experience with this technique over the last five years. This paper discusses a variety of calibration techniques, chemical separation and preparation procedures, followed by various data acquisition protocols to determine a variety of elements in samples ranging from mineral separates, Fe formations, to ultramafics. The procedures evaluated include methods for the determination of 33 trace elements using a modified standard addition procedure and its adaptation to mg quantities of mineral separates; a procedure for the determination of Y, all the rare-earth elements (REE), and Th using a Na2O2 sinter, with quantification using internal standards; and techniques for the determination of very low-level REE in ultramafic samples using ion-exchange concentration. To solve dissolution difficulties involved in Fe formation samples a procedure using oxalic acid to complex the Fe is demonstrated on the reference material IF-G. Precious-metal determination of all the Pt-group elements along with Re and Au is summarised. The application of ICP-MS to isotope ratios is discussed with reference to the determination of 147Sm144Nd and Pb-Th-U isotope ratios. From the results of these studies, it is clear that the future for ICP-MS in earth sciences is very promising.

Laser ablation and arc/spark solid sample introduction into inductively coupled plasma mass spectrometers

Sample introduction using laser ablation and arc and spark ablation is reviewed. Few references were found in the literature on the use of spark or arc ablation as a sample introduction technique into the ICP-MS and emphasis is therefore placed on the use of laser ablation sampling, particularly for Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection; however, many of the principles can also be applied to optical emission detection. The applications of the techniques are described, with particular emphasis on micro-sampling of geological materials.

Determination of partition coefficients for trace elements in high pressure-temperature experimental run products by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS)

Abstract This paper reports the first trace element partition coefficients measured on experimentally produced products (clinopyroxene, garnet, rutile, and glass) by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). A 266 nm (UV) laser microprobe was used to improve ablation characteristics and to achieve a fourfold reduction in ablation pit diameter compared to the previously used 1064 nm beam. Results are compared with PIXE analyses on the same experimental products, and literature values, where available, for similar systems, and include the first simultaneously measured partition coefficients for Zr, Nb, and Ta between rutile and glass. Advantages of the LAM technique include rapid results and simultaneous determination of a wide range of major and trace elements, thus ensuring sampling integrity through time-resolved analysis of the sampled material.

Determination of the precious metals in geological materials by inductively coupled plasma-mass spectrometry (ICP-MS) with nickel sulphide fire-assay collection and tellurium coprecipitation

Abstract A procedure has been developed for the routine determination of the precious metals (Ru, Rh, Pd, Os, Ir, Pt and Au) in geological materials using inductively coupled plasma-mass spectrometry (ICP-MS). The precious metals were isolated using a combination of the nickel sulphide fire-assay and Te coprecipitation procedures and quantified by ICP-MS using two internal standards to correct for matrix and drift effects; Cd for the light elements (Ru, Rh and Pd) and Tl for the heavy elements (Os, Ir, Pt and Au). Over 8 analytical runs, mean instrumental detection limits for a 15-g sample ranged from 0.07 ppb for Ir to 0.7 ppb for Au. Long-term mean reagent blank concentrations were Data from the analysis of Indian Ocean basalts demonstrate the ability of the procedure to make useful determinations at baseline levels in rocks for the full set of elements. Thus, the procedures described here extend the use of PGE geochemistry from mineral deposit studies to normal basaltic and mantle systems.

Application of a frequency quintupled Nd:YAG source (λ=213 nm) for laser ablation inductively coupled plasma mass spectrometric analysis of minerals

This paper reports the use a frequency quintupled Nd:YAG laser (λ=213 nm) for laser ablation of minerals for ICP-MS analysis. The fifth harmonic was produced by in-house modification to an existing frequency quadrupled Nd:YAG laser (λ=266 nm), using commercially available optical components. The maximum pulse energy of the 213 nm output is 7.5 mJ per pulse, based on an output of 350 mJ per pulse at 1064 nm. The pulse energy is controlled and attenuated by a wave plate and MgF2 polariser combination. The laser sampling system was coupled to an enhanced sensitivity ICP-MS system. Comparison of time resolved signals for extended analyses of several materials using 213 and 266 nm for ablation demonstrates that (1) 213 nm laser ablation greatly reduces the incidence of catastrophic ablation of strongly cleaved minerals in thin section, owing to higher absorption; (2) in each case, 213 nm laser ablation produces a longer, flatter, higher intensity signal than conventional 266 nm laser ablation, suggesting a larger volume of transportable particulate is produced; and (3) inter-element fractionation is reduced during analysis using the 213 nm laser ablation system. This study is the first reported use of frequency quintupled laser ablation microprobe (LAM)–ICP-MS.

The application of laser ablation microprobe−inductively coupled plasma−mass spectrometry (LAM-ICP-MS) to in situ (U)-Pb geochronology

Abstract The direct dating of single pitchblende and zircon grains is reported, using a laser ablation microprobe (LAM) which has been coupled to a commercial inductively coupled plasma-mass spectrometer (ICP-MS). The system has been designed for micro sampling minerals in petrographic sections. Major advantages of this technique, compared to other in situ dating techniques, are the: (1) separation of the sampling process from the excitation (dissociation and ionization) processes; (2) minimal complex and variable ion species in the mass analyzer; (3) ability to monitor and adjust the analysis characteristics during ablation; (4) ease of isolation and analysis of the isotopic data at all stages during an ablation sampling; (5) ability to date diverse materials; and (6) relatively low capital costs. Direct dating of uranium-rich phases such as pitchblende is rapid, precise and requires no chemical pretreatment. The ability to analyze small areas (diameters of 20–30 μm) facilitates studies on the timing of primary and secondary U mineralization. Micro sampling of an individual pitchblende grain from the complex Collins Bay uranium deposit in Saskatchewan, Canada, illustrates this new techniques potential and the equivalence of conventional and LAM-ICP-MS age determinations. Analysis of 100-μm-diameter late Archean zircons further demonstrates that LAM-ICP-MS has the potential to become a rival of competing techniques for regional reconnaissance and sediment provenance age studies. In addition, this technique is uniquely capable of providing simultaneous monitoring of chemical and isotopic homogeneity during analysis of accessory minerals used in UPb geochronology.

Analysis of biological reference materials, prepared by microwave dissolution, using inductively coupled plasma mass spectrometry

A procedure has been developed for the analysis of biological materials by inductively coupled plasma mass spectrometry (ICP-MS). Fast, efficient and complete sample digestion is achieved by a combined microwave-nitric acid/open beaker-nitric acid-hydrogen peroxide procedure. The ICP-MS analysis is performed with an on-line five-element internal standard to correct for matrix and instrumental drift effects. Results are presented for 24 elements in three biological reference materials (National Institute of Standards and Technology Standard Reference Materials 5277a Liver and 1566 Oyster and International Atomic Energy Agency Certified Reference Material H4 Animal Muscle). For all elements significantly above the detection limit and reagent blank concentrations, good agreement exists between ICP-MS and certified values.

ELEMENTAL COMPOSITION OF HUMAN MILK FROM MOTHERS OF PREMATURE AND FULL-TERM INFANTS DURING THE FIRST 3 MONTHS OF LACTATION

To examine longitudinal and gestational effects of mineral content in human milk, we analyzed human milk from lactating mothers of premature (PRT,n = 24, < 2000g birth weight, < 37 wk gestation) and fullterm (FT,n = 19, > 2500g, 39–41 wk gestation), living in Newfoundland, Canada. Samples were collected once a week for 8 wk with one final sample collected at 3 mo. Milk samples collected in acid-washed containers were wet ashed with concentrated HNO3, and barium, cadmium, calcium, cesium, cobalt, copper, cerium, lanthanum, magnesium, manganese, molybdenum, nickel, lead, rubidium, tin, strontium, and zinc were measured using inductively coupled plasma-mass spectrometry. Data were analyzed using standard multiple-regression procedures with correlated data analyses to take account of the relationship between successive weeks. Results indicated lower Ca and Pb in PRT milk. Calcium was the only nutritionally significant element to differ between groups. Molybdenum in both PRT and FT milk showed a definite decrease with time, suggesting that the Mo content in milk is homeostatically regulated. However, Ce, La, Ba, and Sn did not display any pattern indicative of biological regulation and potential human requirement.