Problems in obtaining precise and accurate Sr isotope analysis from geological materials using laser ablation MC-ICPMS

This paper reviews the problems encountered in eleven studies of Sr isotope analysis using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) in the period 1995–2006. This technique has been shown to have great potential, but the accuracy and precision are limited by: (1) large instrumental mass discrimination, (2) laser-induced isotopic and elemental fractionations and (3) molecular interferences. The most important isobaric interferences are Kr and Rb, whereas Ca dimer/argides and doubly charged rare earth elements (REE) are limited to sample materials which contain substantial amounts of these elements. With modern laser (193 nm) and MC-ICPMS equipment, minerals with >500 ppm Sr content can be analysed with a precision of better than 100 ppm and a spatial resolution (spot size) of approximately 100 μm. The LA MC-ICPMS analysis of 87Sr/86Sr of both carbonate material and plagioclase is successful in all reported studies, although the higher 84Sr/86Sr ratios do suggest in some cases an influence of Ca dimer and/or argides. High Rb/Sr (>0.01) materials have been successfully analysed by carefully measuring the 85Rb/87Rb in standard material and by applying the standard-sample bracketing method for accurate Rb corrections. However, published LA-MC-ICPMS data on clinopyroxene, apatite and sphene records differences when compared with 87Sr/86Sr measured by thermal ionisation mass spectrometry (TIMS) and solution MC-ICPMS. This suggests that further studies are required to ensure that the most optimal correction methods are applied for all isobaric interferences

Combining isotopic signatures of n(87Sr)/n(86Sr) and light stable elements (C, N, O, S) with multi-elemental profiling for the authentication of provenance of European cereal samples

The aim of this work (from the FP6 project TRACE) was to develop methods based on the use of geochemical markers for the authentication of the geographical origin of cereal samples in Europe (cf. EC regulations 2081/92 and 1898/06). For the first time, the potential usefulness of combining n(87Sr)/n(86Sr) and δ13C, δ15N, δ18O and δ34S isotopic signatures, alone or with key element concentrations ([Na], [K], [Ca], [Cu] and [Rb], progressively identified out of 31 sets of results), was investigated through multiple step multivariate statistics for more than 500 cereal samples collected over 2 years from 17 sampling sites across Europe representing an extensive range of geographical and environmental characteristics. From the classification categories compared (north/south; proximity to the Atlantic Ocean/to the Mediterranean Sea/to else; bed rock geologies) the first two were the most efficient (particularly with the ten variables selected together). In some instances element concentrations made a greater impact than the isotopic tracers. Validation of models included external prediction tests on 20% of the data randomly selected and, rarely done, a study on the robustness of these multivariate data treatments to uncertainties on measurement results. With the models tested it was possible to individualise 15 of the sampling sites

Analisi della composizione di acque minerali europee

Le acque minerali in bottiglia sono spesso preferite dai consumatori perché ritenute più salubri e controllate. Tuttavia il contenuto di molti degli elementi minerali presenti non è specificato in etichetta né regolato dal punto di vista legislativo. Il lavoro, eseguito nel contesto del progetto europeo TRACE (VI Programma Quadro), presenta la composizione di 39 parametri (conducibilità elettrica, pH, durezza, alcalinità totale, ammonio, cloruri, fluoruri, nitrati, nitriti, solfati, Ca, K, Mg, Na, Al, B, Ba, Cd, Ce, Co, Cs, Cu, La, Li, Lu, Mn, Mo, Nd, Ni, Pb, Rb, Se, Sm, Sr, Tl, U, V, Yb, Zn) analizzati su 571 diverse acque minerali in bottiglia campionate sul mercato in 23 Paesi europei nell’arco di 2 anni. Più del 97% elle acque analizzate rispettava i limiti imposti dalla Direttiva Europea 2003/40/CE, solo 16 campioni non sono risultati conformi superando i limiti imposti per il Se (in 7 campioni), per i nitriti (4 campioni), per il Mn (3 campioni), per il Ni (2 campioni), per il Ba (1 campione), per i fluoruri (1 campione) o per i nitrati (1 campione)

Indagine compositiva su acque minerali italiane ed europee in bottiglia

Il lavoro, eseguito nel contesto del progetto europeo TRACE (VI Programma Quadro), presenta i dati relativi a 38 parametri chimico-analitici (conducibilità elettrica, pH, alcalinità totale, ammonio, cloruri, fluoruri, nitrati, nitriti, solfati, Ca, K, Mg, Na, Al, B, Ba, Cd, Ce, Co, Cs, Cu, La, Li, Lu, Mn, Mo, Nd, Ni, Pb, Rb, Se, Sm, Sr, Tl, U, V, Yb, Zn) misurati in 571 acque minerali in bottiglia campionate sul mercato in 23 Paesi europei nell’arco di 2 anni. Limitatamente alle 186 acque di origine italiana campionate, presenta inoltre la composizione relativa ad ulteriori 22 elementi minerali in traccia (Ag, As, Be, Cr, Dy, Er, Eu, Fe, Gd, Hg, Ho, Pr, Sb, Sc, Sn, Tb, Te, Th, Ti, Tm, Y e Zr). Più del 97% delle acque italiane rispettava i limiti imposti dalla Direttiva Europea 2003/40/CE: quattro superavano i limiti imposti per l’As e una quelli per i nitrit

Survey of the chemical composition of 571 European bottled mineral waters

As part of the European TRACE project (Tracing Food commodities in Europe, VI FP, Contract N. 006942), this paper provides a wide-ranging survey of the chemical composition of 571 mineral waters bottled and marketed in 23 European countries, and discusses 39 compositional parameters (specific electric conductivity, pH, hardness, total alkalinity, ammonia, chloride, fluoride, nitrate, nitrite, sulphate, Ca, K, Mg, Na, Al, B, Ba, Cd, Ce, Co, Cs, Cu, La, Li, Lu, Mn, Mo, Nd, Ni, Pb, Rb, Se, Sm, Sr, Tl, U, V, Yb, Zn) mainly referring to legal limits and nutritional implications. According to European legislation 58.1% of samples could be defined as ‘suitable for a low-sodium diet’ while 8.1% could be defined as ‘containing sodium’, 13.7% could be labelled as ‘containing magnesium’, 10.2% as ‘containing fluoride’, 4.9% as ‘containing chloride’, 13.5% as ‘containing sulphate’ and 17.5% as ‘containing calcium’. 2.8% of samples did not conform with European Community limits for at least one parameter (Se, NO2−, Mn, Ni, Ba, F and NO3−). About 9% of samples had boron, nitrate or nitrite levels above the legal limit existing in individual European countries

Sr isotope measurements in beef-analytical challenge and first results

The strontium isotope ratio (87Sr/86Sr) in beef, derived from 206 European cattle, has been measured. These cattle were located in 12 different European regions within France, Germany, Greece, Ireland, Italy, Spain and the UK. As animal protein is known to be a difficult material on which to conduct Sr isotope analysis, several investigations were undertaken to develop and improve the sample preparation procedure. For example, Sr isotope analysis was performed directly on freeze-dried meat and defatted dry mass from the same samples. It was found that enormous differences—sometimes exceeding the measurement uncertainty— could occur between the fractions and also within one sample even if treated in the same manner. These variations cannot be definitely allocated to one cause but are most likely due to inhomogeneities caused by physiological and biochemical processes in the animals as post mortem contamination during analytical processing could be excluded. For further Sr isotope measurements in meat, careful data handling is recommended, and for the authentic beef samples within this project, it was decided to use only freeze-dried material. It can be demonstrated, however, that Sr isotope measurements in beef proteins are a valuable tool for authentication of geographic origin. Although partly overlapping, some of the European sampling sites could be discriminated even by only using 87Sr/86Sr