The accuracy of zircon U–Pb dating by LA-ICPMS is limited by matrix effects related to differences in U–Pb fractionation between an unknown and the calibration standard. Zircon radiation dose has a strong influence on the ablation rate, which in turn affects the amount of U–Pb fractionation and subsequent age calculations. Presented in this study is a previously unrecognized source of uncertainty in LA-ICPMS U–Pb ages due to variations of atmospheric air absorbed onto the surfaces of samples. Laser properties such as fluence (J cm⁻²) will change the laser ablation rate, and therefore the degree of U–Pb fractionation, and this can change the amount of zircon matrix effect. To improve the accuracy of U–Pb dating by LA-ICPMS, a systematic error component related to radiation dose needs to be included, or alternatively a correction to U–Pb dates can be applied as a function of radiation dose relative to the primary calibration standard. This study proposes a method to calculate a correction factor for the zircon matrix effect by measurement of several zircon reference materials with varying radiation dosages.

U–Pb ages of several apatite reference materials, acquired by LA-ICP-MS over a 3.5 year period using the Otter Lake apatite as a primary standard, show systematic offsets (up to 3%) from reference ages obtained by isotope dilution mass spectrometry. The offsets are well outside known analytical errors from counting statistics, uncertainty in common Pb corrections or excess ²⁰⁶Pb in high-Th/U materials. The age offsets also do not correlate strongly with the concentrations of F, Cl, REE, Th and U, with accumulated radiation dose or with the depth of ablation pits. We suggest that the observed age offsets are related to elemental fractionation at the ablation site, but their direction and magnitude cannot at present be predicted from compositional differences in different apatite samples. Our results further suggest that Otter Lake apatite is too heterogeneous for use as a calibration standard. Two other apatite samples, OD306 (1596.7 ± 7.1 Ma) and the 401 apatite (530.3 ± 1.5 Ma) are introduced as potential U–Pb reference materials.

The flame spray technique was used to produce a nano-material with a customized composition. Liquid organic precursors of Si, Ca, Ti, Mg, Fe, and Al in a concentration similar to the matrix of the well-known NIST SRM 610 glass standard were mixed with a selection of rare earth elements (Ce, Gd, Ho, and Tb), precious metals (Ag, Au, Pd, Pt, Rh, and Ru) and Pb at concentrations of approx. 400–500 mg kg⁻¹. The liquid precursor mixture was sprayed and collected as nanopowder, compacted to pellets and analyzed by solution and laser-ablation inductively coupled plasma mass spectrometry. The bulk composition of the material was determined in several aliquots of the powder, either 25 mg or 50 mg. Electron microprobe analyses were carried out to further characterize the major element composition of the pressed nano-material. The pellet was ablated using different laser ablation systems with an aim of assessing the micro-scale homogeneity of the produced material. The manufactured material is homogeneous for major elements and REE's similar to the NIST glass (<5% RSD). However, the distribution of the PGE's showed some larger spatial variation in the order of <7.5%. In addition it is shown that contamination during production leads to heterogeneous distribution of Pb and Ag. Based on the results achieved for Ru, Rh, Pd, Au, Pt, Mg, Ti, and Fe, which are either absent or not available in sufficient concentration levels in NIST glass, it is demonstrated that flame spray synthesis allows production of suitable customized matrix-matched calibration materials for micro-analytical techniques.

A new reference material, STDGL3, for the calibration of in situ analyses of sulfide minerals by LA‐ICP‐MS has been developed and characterised. It represents a lithium‐borate‐based glass containing a mixture of Zn‐ and Fe‐sulfide concentrates doped with several chalcophile elements as well as Zr, Gd, Hf and Ta required for assessing common interferences on Ag, Au and Pt. STDGL3 has a wider range of elements and a better homogeneity compared with existing reference materials for LA‐ICP‐MS analysis of sulfides. Compositional variations for most elements are below 3% RSD, below 5% RSD for Ag, Au and Pt, and below 7% RSD for Se, when performing spot analyses with a 50 μm beam size. Its preparation recipe is reproducible allowing for multiple batches to be made. Use of STDGL3 significantly improves accuracy of sulfide mineral analysis by LA‐ICP‐MS when compared with use of other available reference materials. Performance of STDGL3 was evaluated using several different laser systems. No significant change was observed between 193 nm ArF excimer lasers with 5 and 20 ns pulse widths, but use of 213 and 248 nm lasers displays more systematic differences, especially when analysing galena. Correction coefficients are needed for some elements (Zn and Cd in particular) when analysing sulfide minerals using STDGL3 as a calibration reference material.

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