Search

© The Royal Society of Chemistry 2017. In recent years, several studies have shown that concentrations of essential trace elements naturally present in breast tissues (e.g. Ca, Fe, Cu and Zn) may be significantly increased in breast cancer tissues. This is not surprising because essential elements are responsible for a great number of metabolic and biological processes. The essential trace elements may play some major functions in life: stabilizers, elements of structure, elements for hormonal function and cofactors in enzymes. In any case, the role of trace elements in breast cancer is complex, because it affects many types of molecules, cells and tissues. The combination of analytical and immunehistochemical assays is crucial for better understanding of the role of essential trace elements in promoting tumor growth and migration. Bioimaging analytical techniques with adequate spatial resolution are today of crucial interest to investigate the spatial distribution of trace elements and correlate them with histological aspects in breast tissues. In this vein, in this particular study the application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used for the first time to investigate the actual distribution of the essential trace bioelements (Ca, Fe, Cu and Zn) in breast cancer tissues, and its possible application for tumor diagnostic and prognostic purposes. As has been demonstrated in this study, the levels of Ca, Fe, Cu and Zn in the tumor area are significantly higher than the levels found in the non-tumor one, as well as, a heterogeneous distribution of the investigated metals.

Direct solid analysis of ultrathin layers is investigated using pulsed radiofrequency (rf) glow discharge (GD) time-of-flight mass spectrometry (TOFMS). In particular, previous studies have always integrated the detected ion signals in the afterglow region of the rf-GD pulse, which is known to be the most sensitive one. Nevertheless, the analytical capabilities of other pulse time regions have not been evaluated in detail. Therefore, in this work, we investigate the analyte prepeak region, which is the pulse region where the analyte ions peak after the initial sputtering process of each GD pulse, aiming at obtaining improved depth profile analysis with high depth resolution and with minimum polyatomic spectral interferences. To perform these studies, challenging ultrathin Si-Co bilayers deposited on a Si substrate were investigated. The thickness of the external Si layer was 30 nm for all the samples, whilst the internal Co layer thicknesses were 30, 10, 5, 2 and 1 nm, respectively. It should be remarked that the top layer and the substrate have the same matrix composition (Si>99.99%). Therefore, the selected samples are suitable to evaluate the response of the Si ion signal in the presence of an ultrathin Co layer as well as the possible oxygen contaminations or its reactions. Additionally, these samples have been evaluated using time-of-flight secondary ion mass spectrometry, and the results compare well to those obtained by our pulsed rf-GD time-of-flight mass spectrometry results. © Springer-Verlag 2011.

Depth profile analyses of ultra-thin layers and their interfaces are investigated, using an innovative Pulsed-radiofrequency Glow Discharge Time-of-Flight Mass Spectrometer (pulsed-rf-GD-TOFMS), to obtain information about the presence of minor elements and to evaluate segregation/diffusion processes at the interfaces. A series of ultra-thin Nb/Al1¿x Co x bilayers, deposited on Si wafers by dc-magnetron sputtering, is analyzed. An Al1¿x Co x layer is first deposited on the Si substrate with controlled constant thickness (t AlCo = 6 nm), and different stoichiometries (Co atomic concentration, x = 0, 0.015, 0.035, 0.045, 0.09, 0.35). Then, a Nb layer is deposited on top of the AlCo one, with a thickness t Nb = 50 nm that is also kept constant along the whole series. Qualitative depth profiles of those layered sandwich-type samples are determined using our pulsed-rf-GD-TOFMS setup, indicating segregation of Al and Co and diffusion of Co into the Si substrate, as a function of the Co atomic concentration in the AlCo internal layer. Additionally, a linear calibration curve was achieved plotting the Co atomic concentration versus the total integrated Co ion signal, allowing the Co quantification in ultra-thin layers (6 nm). Moreover, Secondary Ion Mass Spectrometry (SIMS) was used as a reference technique to validate the high analytical potential of pulsed-rf-GD-TOFMS for the analysis of ultra-thin layers and interfaces. The comparative analytical performance of both techniques is discussed.

En este trabajo se han preparado y analizado dos series de muestras formadas por un sustrato de Si sobre el que se han depositado bicapas Nb/Al en una de las series y Si/Co en la otra. La capa exterior en cada serie de muestras es de espesor fijo, 50 nm en el caso del Nb y 30 nm para el Si. La capa interna depositada sobre el sustrato tiene espesor variable desde 50 nm hasta 1 nm. Dichas muestras fueron analizadas mediante descarga luminiscente de radiofrecuencia pulsada con detección por espectrometría de masas de tiempo de vuelo para estudiar el potencial de esta técnica para el análisis de capas ultra-delgadas. Los resultados muestran que es posible analizar y resolver capas de espesores tan delgados como 1 nm. Los perfiles obtenidos por esta técnica se han comparado con los obtenidos mediante espectrometría de masas de iones secundarios.

Nanometer depth resolution is investigated using an innovative pulsed-radiofrequency glow discharge time-of-flight mass spectrometer (pulsed-rf-GD-TOFMS). A series of ultra-thin (in nanometers approximately) Al/Nb bilayers, deposited on Si wafers by dc-magnetron sputtering, is analyzed. An Al layer is first deposited on the Si substrate with controlled and different values of the layer thickness, t Al. Samples with t Al = 50, 20, 5, 2, and 1 nm have been prepared. Then, a Nb layer is deposited on top of the Al one, with a thickness t Nb = 50 nm that is kept constant along the whole series. Qualitative depth profiles of those layered sandwich-type samples are determined using our pulsed-rf-GD-TOFMS set-up, which demonstrated to be able to detect and measure ultra-thin layers (even of 1 nm). Moreover, Gaussian fitting of the internal Al layer depth profile is used here to obtain a calibration curve, allowing thickness estimation of such nanometer layers. In addition, the useful yield (estimation of the number of detected ions per sputtered atom) of the employed pulsed-rf-GD-TOFMS system is evaluated for Al at the selected operating conditions, which are optimized for the in-depth profile analysis with high depth resolution.