Simultaneous Determination of Size and Position of Silver and Gold Nanoparticles in Onion Cells using Laser Ablation-ICP-MS.

Size distribution and mapping analyses of Ag and Au nanoparticles (NPs) have been made using an ICP-MS combined with laser ablation sampling technique (LA-ICP-MS). With the femtosecond laser (Ti:S laser) ablation system, the measured size distribution was modified to be smaller, whereas this disintegration could be reduced when the nanosecond laser (ArF Excimer laser) ablation was employed. This suggests that both the size and position of the NPs can be defined by the nanosecond LA-ICP-MS technique. More importantly, based on the peak-height analyses (PHA) of the measured signal intensity profiles, the present form of the analytes, whether particulate or ionic form, could be defined. This is very important to investigate the transport of the NPs within biological samples. To demonstrate the unique feature of the technique, imaging analyses of Ag and Au NPs, together with distribution analysis of the ionic form, were conducted on onion cells, prepared through dosing experiments of the Ag and Au NPs. There were clear differences in both the increasing rates of the numbers of NPs and the concentration range of the ionic form between the Ag and Au. The data obtained here demonstrate clearly that the LA-ICP-MS technique can become a major analytical tool to obtain both the size distribution and position of NPs from tissue samples.

iQuant2: Software for Rapid and Quantitative Imaging Using Laser Ablation-ICP Mass Spectrometry.

We report on the development of a software program named iQuant2 which creates visual images from two-dimensional signal intensity data obtained by a laser ablation-ICP-mass spectrometry (LA-ICPMS) technique. Time-resolved signal intensity profiles can be converted to position resolved signal intensity data based on the rastering rate (µm s-1) of the laser ablation. Background signal intensities obtained without laser ablation (gas blank) are used as the background, and all of the blank-subtracted intensity data can be used for the imaging analysis. With this software, deformation of the created image can be corrected visually on a PC screen. The line profile analysis between the user-selected points can be observed using the iQuant2 software. To accomplish this, data points on the profile line were automatically calculated based on the interpolation between the analysis points. The resulting imaging data can be exported and stored as JPEG, BMP or PNG formats for further processing. Moreover, a semi-quantitative analysis can be made based on the coupling of the external correction of the RSF (relative sensitivity factor) using NIST SRM610 with normalization of the corrected signal intensity data being 100%. The calculated abundance data for major elements are in reasonable agreement with the values obtained by electron probe micro analyzer (EPMA). With the software developed in this study, both the rapid imaging and semi-quantitative determinations can be made.

Quantitative Analysis of Major and Minor Elements in Lead-free Solder Chip by LA-ICP-MS.

A method was established for the quantitative analysis of the elements (Cu, Ag, Pb, and Sn) in solder samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), with Sn-based matrix matched standard solutions for defining the calibration curves. It was found that chloride-ion presented in commercially available Sn standard solution resulted in a precipitation of AgCl and caused the deterioration of the linearity of the calibration curve for Ag. Therefore, a laboratory-made chloride-free Sn solution was used to prepare Sn matrix matched standard solutions so as to ensure the stability of the elements including Ag. For the quantitative analysis of solder samples by LA-ICP-MS, the operating conditions of the LA instruments were set to obtain a fluence of over 12 J cm-2. This is mainly because of larger LA-induced elemental fractionations using a fluence of <10 J cm-2. The results for Ag, Cu, Pb, and Sn in a certified reference material (NMIJ CRM 8203-a) were close to, or in agreement with, the certified values, indicating that the present method was valid for the quantitative analysis of the elements in solder samples. In comparison to the certified values, relatively larger uncertainties were obtained for the analytical results by LA-ICP-MS, which could be attributed to the dependence on the homogeneity of the sample because the sample aliquots used for analysis were much smaller than those required for the traditional analytical procedures (i.e., sample quantity ratio of ca. 1:13000). Further improvement of the uncertainty might be obtained by using a larger sample quantity for the analysis by LA-ICP-MS so as to improve the representativeness of the sample.

A long-forgotten 'dinosaur' bone from a museum cabinet, uncovered to be a Japan's iconic extinct mammal, Paleoparadoxia (Desmostylia, Mammalia).

Here, we report a new 'discovery' of a desmostylian fossil in the geological collection at a national university in Japan. This fossil was unearthed over 60 years ago and donated to the university. Owing to the original hand-written note kept with the fossil in combination with interview investigation, we were able to reach two equally possible fossil sites in the town of Tsuchiyu Onsen, Fukushima. Through the interviews, we learned that the fossil was discovered during construction of a debris flow barrier and that it was recognized as a 'dinosaur' bone among the locals and displayed in the Village Hall before/until the town experienced a fire disaster in 1954. As scientific findings, the fossil was identified to be a right femur of Paleoparadoxia (Desmostylia), which shows well-preserved muscle scars on the surface. The age was estimated to be 15.9 Ma or younger in zircon-dating. This study shows an excellent case that historical and scientific significances could be extracted from long-forgotten uncatalogued specimens as long as the original information is retained with the specimens.