This paper critically reviews the state-of-the-art of isotope amount ratio measurements by solution-based multi-collector inductively coupled plasma mass spectrometry (MC ICP-MS) and presents guidelines for corresponding data reduction strategies and uncertainty assessments based on the example of n(87Sr)/n(86Sr) isotope ratios. This ratio shows variation attributable to natural radiogenic processes and mass-dependent fractionation. The applied calibration strategies can display these differences. In addition, a proper statement of uncertainty of measurement, including all relevant influence quantities, is a metrological prerequisite. A detailed instructive procedure for the calculation of combined uncertainties is presented for Sr isotope amount ratios using three different strategies of correction for instrumental isotopic fractionation (IIF): traditional internal correction, standard-sample bracketing, and a combination of both, using Zr as internal standard. Uncertainties are quantified by means of a Kragten spreadsheet approach, including the consideration of correlations between individual input parameters to the model equation. The resulting uncertainties are compared with uncertainties obtained from the partial derivatives approach and Monte Carlo propagation of distributions. We obtain relative expanded uncertainties (Urel; k = 2) of n(87Sr)/n(86Sr) of < 0.03 %, when normalization values are not propagated. A comprehensive propagation, including certified values and the internal normalization ratio in nature, increases relative expanded uncertainties by about factor two and the correction for IIF becomes the major contributor.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-015-9003-9) contains supplementary material, which is available to authorized users.

Transgenerational isotopic marking has been recognised as an efficient tool for mass marking of high numbers of fish larvae by injecting female spawners with enriched isotope solutions. So far, mainly enriched stable barium isotopes have been applied for this purpose. Here, we present an alternative approach for individual-specific transgenerational marking using strontium 86 Sr/ 84 Sr double spikes. Four isotonic double-spike solutions with different molar fractions of 86 Sr and 84 Sr and different total Sr concentrations were administered to four female spawners of common carp, Cyprinus carpio, L., by intraperitoneal injection, and one additional female spawner was injected a blank isotonic solution as control. Otoliths (lapilli) were sampled from juvenile offspring and analysed for their Sr isotopic composition by laser ablation-multi collector-inductively coupled plasma-mass spectrometry. Central otolith regions of the progeny of female carps treated with concentrations of at least 0.45 mg 84 Sr kg À1 bodyweight and 2.28 mg 86 Sr kg À1 bodyweight showed a significant shift of the absolute 88 Sr/ 86 Sr and 88 Sr/ 84 Sr isotope ratios from the natural baseline. Isotope pattern deconvolution was successfully applied for the identification of the originally injected 86 Sr/ 84 Sr molar fraction ratios of the individual double spikes. Enriched stable Sr isotope double spikes represent an important alternative to enriched stable Ba isotopes for transgenerational marking, especially in freshwater systems.

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ICP-MS is based on the formation of (preferentially monovalent positively) charged atomic ions in an inductively coupled Ar plasma at almost 10 000 K. The ions formed are transferred from the plasma source at ambient pressure into a mass separator operated at high vacuum via a set of cones. The ions are separated according to their mass/charge ratio in the mass separator (quadrupole, magnetic sector field or time-of-flight mass separator). In most cases, the ions are detected using a secondary electron multiplier; in some set-ups (also) a Faraday cup can be used. Single-collector (scanning mass spectrometer usually used for quantitative elemental analysis) or multicollector (static operation of mass spectrometer for precise isotope ratio analysis) configurations can be found (Figures 12.1 and 12.2).

Several reagents were tested as possible future pre-treatments to hydrogen peroxide bleaching of discoloured paper with the goal of minimizing the degrading effect of hydrogen peroxide on cellulose. Two historic rag papers were used as testing substrate, one with high, the other with low levels of iron ion content. The two papers underwent the following test protocol: all samples were rinsed in deionized water for ten minutes. Samples were then divided to undergo seven different bleaching pre-treatments: (1) deacidification with calcium hydroxide solution at pH 9; (2) deacidification with magnesium hydrogen carbonate solution at pH 7.5; (3) hydrochloric acid (HCl, 0.1 M, pH 1) followed by deacidification with calcium hydroxide; (4) calcium phytate (1.75 mmol/L, pH 5.3) followed by deacidification with calcium hydroxide; (5) magnesium phytate (pH 6.5) followed by deacidification with magnesium hydrogen carbonate solution; (6) and (7) the chelating agent diethylene-triamine-pentaacetic acid (DTPA, 0.005 mol/L, pH 3) followed by deacidification either with calcium hydroxide or magnesium hydrogen carbonate. All samples were immersed in 3% hydrogen peroxide baths (pH 9, adjusted with calcium hydroxide). They were dynamically aged in a customized setup in a stack (20°C-80°C, three hour intervals, six weeks). The samples underwent analyses before treatment, after bleaching and after accelerated ageing. The molecular weight and carbonyl group content of the cellulose were determined with fluorescence labelling in combination with gel permeation chromatography (GPC-MALLS). Brightness reversion of the papers was determined by colourimetry. The iron content level was determined by inductively coupled plasma-mass spectrometry (ICP-MS) before and after treatment. The paper with low iron ion content did not benefit measurably from the pre-treatments, whereas the paper with high iron content benefited from some of the pre-treatments, as determined after accelerated aging. The least increase in carbonyl group content after accelerated ageing was achieved with calcium phytate (4); followed by magnesium phytate (5); and DTPA with magnesium hydrogen carbonate deacidification (7). The highest carbonyl group increase was caused by the calcium hydroxide pre-treatment (1). The Mw was best with the phytate-treated samples (4 and 5), followed by DTPA with magnesium hydrogen carbonate deacidification (7) and hydrochloric acid (3); the calcium-hydroxide deacidified sample showed the greatest Mw loss (1). All of tested iron removal and complexation treatments (3-7) diminished brightness reversion. DTPA (6 and 7) and hydrochloric acid (3) diminished the iron ion content of the high-iron-content paper by 30%. In sum, the tests 3-7 showed distinct benefits over deacidification alone (1 and 2) and may become viable as pre-treatment agents before hydrogen peroxide bleaching after further testing on object materials.