Isotopic Traceability (13C and 18O) of Greek Olive Oil

In recent years, isotopic analysis has been proven a valuable tool for the determination of the origin of various materials. In this article, we studied the ¹⁸O and ¹³C isotopic values of 210 olive oil samples that were originated from different regions in Greece in order to verify how these values are affected by the climate regime. We observed that the δ¹⁸O isotopic values range from 19.2 ‰ to 25.2 ‰ and the δ¹³C values range from −32.7 ‰ to −28.3 ‰. These differences between the olive oils’ isotopic values depended on the regional temperature, the meteoric water, and the distance from the sea. Furthermore, we studied the ¹³C isotopic values of biophenolic extracts, and we observed that they have same capability to differentiate the geographic origin. Finally, we compared the isotopic values of Greek olive oils with samples from Italy, and we concluded that there is a great dependence of oxygen isotopes on the climatic characteristics of the different geographical areas.     

Determination of Nitrogen and Oxygen Isotopes in Nitrates: A Minireview

Nitrogen and oxygen isotope ratios (δ¹⁵N and δ¹⁸O) in nitrates are important in hydrology, oceanography, atmospheric chemistry, and agriculture. This paper reviews current isotope ratio mass spectrometry methods for the determination of nitrogen and oxygen isotopes in nitrates that include graphite combustion, AgNO₃-ion exchange, Ba(NO₃)₂-acetone, two-step chemical conversion, bacterial approaches, and off-axis integral cavity output laser spectroscopy. This paper introduces the principles, processes, advantages, and disadvantages of these procedures. Future studies should focus on the determination of oxygen isotopes. The development of novel spectroscopic or other isotopic methodology may also be new research directions. In addition, in some nitrates, δ¹⁷O is more sensitive than traditional δ¹⁸O and further development for this isotope is of interest. In addition, the determination of δ¹⁷O may be used to more accurately evaluate δ¹⁸O.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

The Impact of Grape Varieties to Wine Isotopic Characterization

This paper highlights the results of a study regarding the impact of geo-climatic conditions, the influence of grape varieties, and harvest year on the isotopic characterization of a wine from a specific vineyard area, using stable isotope ratio analysis by continuous flow mass spectrometry CF-IRMS. This analytical technique has made a significant contribution on wine characterization, by proving the botanical and geographical origin of the wine raw material.

A great variability was observed to sap ¹⁸O and ²H isotopic ratios for different types of vine (Vitis vinifera plant) from the studied area, Dealu Mare-Valea Calugareasca, reflecting the significant influence of variety on isotopic features. On the other hand, the comparison of stable isotopic fingerprints for rainfall water and sap revealed a close approximation value for ¹⁸O isotopic ratio, and an insignificant variation coefficient of ¹³C isotopic ratio in wine varieties (about 2.85%).

The results of isotopic characterization for grape vine sap and original wines for different varieties existing in Dealu Mare-Valea Calugareasca vineyard indicates the relevance of meteorological and viticulture parameters like precipitation, date of vintage, and grape cultivar for wine authentication process.     

On the calibration of continuous,high‐precision δ18O and δ2H measurements using an off‐axis integrated cavity output spectrometer

The ¹⁸O and ²H of water vapor serve as powerful tracers of hydrological processes. The typical method for determining water vapor δ¹⁸O and δ²H involves cryogenic trapping and isotope ratio mass spectrometry. Even with recent technical advances, these methods cannot resolve vapor composition at high temporal resolutions. In recent years, a few groups have developed continuous laser absorption spectroscopy (LAS) approaches for measuring δ¹⁸O and δ²H which achieve accuracy levels similar to those of lab‐based mass spectrometry methods. Unfortunately, most LAS systems need cryogenic cooling and constant calibration to a reference gas, and have substantial power requirements, making them unsuitable for long‐term field deployment at remote field sites. A new method called Off‐Axis Integrated Cavity Output Spectroscopy (OA‐ICOS) has been developed which requires extremely low‐energy consumption and neither reference gas nor cryogenic cooling. In this report, we develop a relatively simple pumping system coupled to a dew point generator to calibrate an ICOS‐based instrument (Los Gatos Research Water Vapor Isotope Analyzer (WVIA) DLT‐100) under various pressures using liquid water with known isotopic signatures. Results show that the WVIA can be successfully calibrated using this customized system for different pressure settings, which ensure that this instrument can be combined with other gas‐sampling systems. The precisions of this instrument and the associated calibration method can reach ～0.08‰ for δ¹⁸O and ～0.4‰ for δ²H. Compared with conventional mass spectrometry and other LAS‐based methods, the OA‐ICOS technique provides a promising alternative tool for continuous water vapor isotopic measurements in field deployments. Copyright © 2009 John Wiley & Sons, Ltd.     

What can we learn from N2O isotope data? – Analytics,processes and modelling

The isotopic composition of nitrous oxide (N₂O) provides useful information for evaluating N₂O sources and budgets. Due to the co-occurrence of multiple N₂O transformation pathways, it is, however, challenging to use isotopic information to quantify the contribution of distinct processes across variable spatiotemporal scales. Here, we present an overview of recent progress in N₂O isotopic studies and provide suggestions for future research, mainly focusing on: analytical techniques; production and consumption processes; and interpretation and modelling approaches. Comparing isotope-ratio mass spectrometry (IRMS) with laser absorption spectroscopy (LAS), we conclude that IRMS is a precise technique for laboratory analysis of N₂O isotopes, while LAS is more suitable for in situ/inline studies and offers advantages for site-specific analyses. When reviewing the link between the N₂O isotopic composition and underlying mechanisms/processes, we find that, at the molecular scale, the specific enzymes and mechanisms involved determine isotopic fractionation effects. In contrast, at plot-to-global scales, mixing of N₂O derived from different processes and their isotopic variability must be considered. We also find that dual isotope plots are effective for semi-quantitative attribution of co-occurring N₂O production and reduction processes. More recently, process-based N₂O isotopic models have been developed for natural abundance and ¹⁵N-tracing studies, and have been shown to be effective, particularly for data with adequate temporal resolution. Despite the significant progress made over the last decade, there is still great need and potential for future work, including development of analytical techniques, reference materials and inter-laboratory comparisons, further exploration of N₂O formation and destruction mechanisms, more observations across scales, and design and validation of interpretation and modelling approaches. Synthesizing all these efforts, we are confident that the N₂O isotope community will continue to advance our understanding of N₂O transformation processes in all spheres of the Earth, and in turn to gain improved constraints on regional and global budgets.     

Broad-Range Detection of Water Vapor using Cavity Ring-down Spectrometer

Quantitative measurement of water vapor is essential in many fields including semiconduc-tor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy. The instrument is high-vacuum compatible, self-calibrated by using the free-spectral-range of the ring-down cavity made of low-thermal-expansion Invar. Using a single tunable diode laser working at 1.39 μm, detection of trace water vapor in vacuum and in high-purity helium gas, and also determination of humidity at ambient conditions, have been demonstrated. It indicates that the instrument can be used to detect the partial pressure of water vapor in a very broad range from 10^-7 Pa to 10³ Pa. Such an optical hygrometer can be potentially applied as a primary moisture standard to determine the vapor pressures of water (ice) at low temperatures.     

New synthesis of mullite. Structural evolution study by 17O, 27Al and 29Si MAS NMR spectroscopy

Mullite has been prepared from a new combination of precursors. An aluminum alkoxide, aluminium isopropoxide, and silicon tetrachloride, are hydrolysed in tetrahydrofuran solution by ¹⁷O enriched water. The resulting powder is chemically homogeneous, crystallizing into mullite at 980°C. The structural evolution has been studied by DTA, TGA, XRD and ¹⁷O, ²⁷Al and ²⁹Si MAS NMR spectroscopy.     

Isotopic evidence of allogenic groundwater recharge in the Northern Ordos Basin

Large amount of groundwater recharge runs in opposite direction to the scarce surface water resources in the Northern Ordos Basin, and there are two controversial viewpoints. Hydrogen and oxygen stable isotopes are employed to identify the groundwater origin. Results show that surface water and soil water are mainly recharged by groundwater instead of local precipitation. The groundwater is not recharged by local rainfall, but is inferred to have originated from the Tibetan Plateau, based on isotopic (D, ¹⁸O, ³He/⁴He), hydraulics, geophysical, and geological evidence. It is consistent with the viewpoint of external groundwater recharging in North China.     

Determination of 17O and 18O isotopic abundances in 238Pu materials by γ-ray spectrometry

A procedure has been developed for nondestructive determinations of ¹⁷O and ¹⁸O isotopic abundances in ²³⁸PuO₂ fuels produced for biomedical application. Close control of these isotopes is important because they increase the neutron emission rate caused by (α, n) reactions. γ-Rays accompanying these reactions are measured by a lithium-drifted germanium [Ge(Li)] detector and related to their respective isotopic abundances. Each determination has a detection limit approximating the lowest contents encountered in PuO₂ samples of 0.005% ¹⁷O and 0.001% ¹⁸O. The average deviations for each determination are estimated to be about ±25% at their detection levels, and less than ± 10% for abundances above 0.01%.     

Laser Ablation Molecular Isotopic Spectrometry: Strontium and its isotopes

The experimental details are reported of Laser Ablation Molecular Isotopic Spectrometry (LAMIS) and its application for performing optical isotopic analysis of solid strontium-containing samples in ambient atmospheric air at normal pressure. The LAMIS detection method is described for strontium isotopes from samples of various chemical and isotopic compositions. The results demonstrate spectrally resolved measurements of the three individual ⁸⁶Sr, ⁸⁷Sr, and ⁸⁸Sr isotopes that are quantified using multivariate calibration of spectra. The observed isotopic shifts are consistent with those calculated theoretically. The measured spectra of diatomic oxide and halides of strontium generated in laser ablation plasmas demonstrate the isotopic resolution and capability of LAMIS. In particular, emission spectra of SrO and SrF molecular radicals provided clean and well resolved spectral signatures for the naturally occurring strontium isotopes. A possibility is discussed of using LAMIS of strontium isotopes for radiogenic age determination.     

A new Chinese national reference material (GBW04481) for calcite oxygen and carbon isotopic microanalysis

Carbonate oxygen (O) and carbon (C) isotopes are widely used as proxies for tracing the processes and physicochemical conditions of many geological events and environmental changes in Earth Science. In particular, O and C isotopic variations at micrometer scales revealed by modern microbeam analytical techniques such as SIMS and NanoSIMS are robust archives for reconstructing palaeoenvironment and paleoclimate changes at annual and seasonal resolution or even higher temporal resolution. Widespread application of carbonate O and C isotopic microanalysis in Earth Sciences, however, has been restricted due to limitation of high-quality carbonate reference materials for O and C isotopic microanalysis. We introduce in this paper a new calcite reference material for calcite O and C isotopic microanalysis. This calcite is collected from a drill-core of the Oka carbonatite complex (Quebec, Canada). We demonstrated that the Oka calcite is fairly homogeneous in O and C isotopic compositions at micrometer scales based on homogeneity test by hundreds of SIMS O and C isotopic analyses. Precise determinations by using conventional gas-source IRMS yield the recommended value of δ¹⁸O_VPDB = −23.12 ± 0.15‰ (1SD) and δ¹³C_VPDB = −5.23 ± 0.06‰ (1SD) for the Oka calcite, which has been certified as the first class of Chinese national certified reference material (GBW04481) for O and C isotopic microanalysis.     

Simultaneous measurement of δH, δO,and δO in H2O using a commercial cavity ringdown spectrometer

We demonstrate that a commercial instrument that provides measurements of ¹⁸O/¹⁶O and D/H ratios in water samples can be modified to also provide measurements of ¹⁷O/¹⁶O. This additional capability and associated precision allows for the discernment between conventional mass-dependent processes, such as isotope exchange and evaporation and mass-independent processes that arise from non-equilibrium chemical and photochemical processes. We demonstrate this resolution by performing a series of experiments including evaporation and reservoir-mixing with ¹⁷O enriched water samples followed by evaporation. The ability to simultaneously measure ¹⁶O, ¹⁷O, and ¹⁸O abundances in water samples using the procedures described here should help to facilitate multi-isotopic studies of water (and other compounds) in astrochemical, geochemical, and biological studies.     

Comment on “Freezing Point Mixtures of H216O with H217O and Those of Aqueous CD3CH2OH and CH313CH2OH Solutions”

In a recent article, Kiyosawa [J. Solution Chem. 33, 323 (2004)] reports that the freezing points of isotopic mixtures of ordinary water and ¹⁷O enriched water show an unexpectedly large linear dependence on the concentration of H₂¹⁷O. Surprisingly, the constant of proportionality to the H₂¹⁷O concentration is nearly five times larger than that of H₂¹⁸O found in earlier studies by Kiyosawa [J. Solution Chem. 20, 583 (1991)]. We show that the H₂¹⁷O result is not consistent with other data or models. For example, a recent determination of the triple point temperature dependence on isotopic composition in naturally and artificially depleted waters [White et al. in Temperature, Its Measurement and Control in Science and Industry, Vol. 7, D. C. Ripple, Ed., AIP CP 684, 221–226 (2003)] is consistent with the H₂¹⁸O and D₂O results from Kiyosawa (1991) [White and Tew in Report of the 22nd Meeting of the Consultative Committee for Thermometry, Document CCT/03-21, BIPM, Severes, France, 2003] but is inconsistent with the H₂¹⁷O results from Kiyosawa (2004). Additionally, the results from Kiyosawa (1991) are close to what would be found in ideal solutions for those isotopic forms, whereas the H₂¹⁷O proportionality from Kiyosawa (2004) is about 10 times larger than similarly predicted. One possible explanation is that the original ¹⁷O enriched water sample contained a small amount of D₂O, and the sample, if available, should be subject to isotopic analysis to help resolve these inconsistencies.     

On the detection of both carbonyl and hydroxyl oxygens in amino acid derivatives: a O NMR reinvestigation

The hypothesis and the conclusions of previous ¹⁷O NMR studies on the detection of both oxygens of the carboxylic group of Boc-[¹⁷O]Tyr(2,6-diClBzl)-OH in DMSO-d₆ solution (Tetrahedron Lett.2000, 41, 8651) are reconsidered. The appearance of two discrete resonances at 340 and 175 ppm of this protected amino acid is not now attributed: (a) to the reduction of the intramolecular conformational exchange rate, due to the effect of intramolecular hydrogen bonding of the hydroxy part of the carboxyl with the carbonyl oxygen of the Boc-group, and (b) to the effect of solvent viscosity, suggested in the mentioned study. The cause of this phenomenon is now attributed to a strong hydrogen bonding of the polar proton acceptor solvent DMSO with the carboxy group, which effectively reduces the proton exchange rate, thus becoming slow on the ¹⁷O NMR time scale.     

Raman spectra and O NMR study effects of CaCl2 and MgCl2 on water structure

With various concentrations of CaCl₂ and MgCl₂ aqueous solution below 1.0 mol/l, Raman spectra of water in the OH stretch region of 2500-4000 cm⁻¹ and ¹⁷O NMR chemical shift of water are measured and the Raman spectra are deconvoluted. Both Raman spectra and ¹⁷O NMR of water show that the effect of Ca²⁺ on water structure is stronger than that of Mg²⁺. CaCl₂ and MgCl₂ destroy four hydrogen bonded water structure, but promote median water cluster size.     

17O NMR Investigation of Chemical Homogeneity in Hybrid Systems

¹⁷O NMR experiments using enriched water were performed to followthe hydrolysis-condensation process of dimethyldiethoxysilanetetraethoxysilane and a 1/1 mixture of dimethyldiethoxysilane andtetraethoxysilane (H₂O/OEt = 0.5; pH = 2). The spectrarecorded over several hours time period were simulated to followquantitatively the variations of residual water, hydroxyl groups(Si–¹⁷ H) and oxo bridges (Si–¹⁷ –Si). Presence of a resonance signal due oxo bridges between di- andtetrafunctional Si units clearly demonstrates that co-condensationreactions occur to a large extent between the two alkoxides, and that thesebonds are stable during the aging period.     

Radiochemical characterization of spring waters in Balaton Upland, Hungary, estimation of radiation dose to members of public

Hungary is rich in spring waters. A survey studying the naturally occurring alpha emitter radionuclides in 30 frequently visited and regularly consumed spring waters was conducted out in the Balaton Upland region of Hungary.²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po activity concentrations were determined by using alpha spectrometry after separation from matrix elements. Average concentration (mBq L^{− 1}) of ²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po in the spring waters is varied from 2.1 to 601, from < 1.1 to 65.4, from 3.9 to 741.9, from < 0.44 to 274.3 and from 2 to 15.2 respectively. In most cases radioactive disequilibrium was observed between uranium and radium isotopes. The doses for the analyzed samples of spring water are in the range 3.59–166.73 μSv y^{− 1} with an average 18.2 μSv y^{− 1} .This is well below the 100 μSv y^{− 1} reference level of the committed effective dose recommended by WHO. Only one water sample had a dose higher than 100 μSv y^{− 1}, mainly due to the contribution from radium (²²⁶Ra, ²²⁴Ra) and ²¹⁰Po isotopes. This study provides important information for consumers and authorities about their internal radiological exposure risk from spring water intake.     

Deconvolution of liquid scintillation alpha spectra of mixtures of uranium and radium isotopes

A method for the determination of uranium and radium isotopes in water samples is proposed. Liquid scintillation techniques were used for collecting alpha spectra, which were then analyzed by fitting the alpha peaks with overlapping Gaussians. The analysis can quantify the observed isotopes with accuracy depending on the activity of each isotope.In order to simulate the peaks with Gaussian normal distribution functions, the centroid of each peak as well as the full width at half maximum (FWHM) are required, as they depend on the quenching of the sample. For this purpose, samples with known activities of ²²⁶Ra and its decay products and also of the uranium isotopes ²³⁸U and ²³⁴U, at various quenching levels, were used to establish the correlation of the peaks’ shift with the quench effect. In addition, the correlation of the FWHM with the centroid of a peak was determined, using the same procedure.Following the above analysis technique, an average of 97 ± 2% of detection efficiency and a lower limit of detection of 8.2 mBq kg⁻¹ for alpha isotopes were achieved.     

Olive Oil Traceability Studies Using Inorganic and Isotopic Signatures: A Review

The olive oil industry is subject to significant fraudulent practices that can lead to serious economic implications and even affect consumer health. Therefore, many analytical strategies have been developed for olive oil’s geographic authentication, including multi-elemental and isotopic analyses. In the first part of this review, the range of multi-elemental concentrations recorded in olive oil from the main olive oil-producing countries is discussed. The compiled data from the literature indicates that the concentrations of elements are in comparable ranges overall. They can be classified into three categories, with (1) Rb and Pb well below 1 µg kg⁻¹; (2) elements such as As, B, Mn, Ni, and Sr ranging on average between 10 and 100 µg kg⁻¹; and (3) elements including Cr, Fe, and Ca ranging between 100 to 10,000 µg kg⁻¹. Various sample preparations, detection techniques, and statistical data treatments were reviewed and discussed. Results obtained through the selected analytical approaches have demonstrated a strong correlation between the multi-elemental composition of the oil and that of the soil in which the plant grew. The review next focused on the limits of olive oil authentication using the multi-elemental composition method. Finally, different methods based on isotopic signatures were compiled and critically assessed. Stable isotopes of light elements have provided acceptable segregation of oils from different origins for years already. More recently, the determination of stable isotopes of strontium has proven to be a reliable tool in determining the geographical origin of food products. The ratio ⁸⁷Sr/⁸⁶Sr is stable over time and directly related to soil geology; it merits further study and is likely to become part of the standard tool kit for olive oil origin determination, along with a combination of different isotopic approaches and multi-elemental composition.