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

Low volume sampling device for mass spectrometry analysis of gas formation in nickel-metalhydride (NiMH) batteries

\u3cp\u3eRechargeable nickel-metalhydride (NiMH) batteries have major advantages with respect to environmental friendliness and energy density compared to other battery systems. Research on thermodynamics and reaction kinetics is required to study the behaviour of these batteries, especially under severe operating conditions such as overcharging and (over)discharging. During these processes several reactions take place resulting in the formation of oxygen and hydrogen gas. Hence, the recombination processes should be well controlled to guarantee that the partial oxygen and hydrogen pressure inside the battery are kept low. Mass spectrometry is one of the analytical techniques capable of measuring the composition of gases released inside the battery during the charge and discharge processes. However, the sample gas needs to be withdrawn from the battery during the experiment. The gas consumption must be kept to a minimum otherwise the equilibrium inside the battery will be disturbed. A bench-top quadrupole mass spectrometer with a standard capillary by-pass inlet cannot be used for this purpose as its gas consumption is in the 1-10 ml/min range. In this paper, a new gas inlet device is presented that reduces gas consumption to a value <50 μl/h. The use of a capillary by-pass splitter and a discontinuous sampling procedure allow mass spectrometry to be used as a gas analysis tool in many applications in which small amounts of sample gas are involved. Experiments with standard AA-size NiMH batteries show that hydrogen release dominates during (over)charging at increased charging rates. Beside mass spectrometry, evolved gases are also analysed using Raman spectroscopy. Although some differences are observed, the results of similar experiments show a good agreement.\u3c/p\u3

In situ Raman analysis of gas formation in NiMH batteries

\u3cp\u3eIn this paper Raman spectrometry is introduced in the field of sealed battery research for in situ gas-phase analysis and for long-term measurements. For this purpose, a new method was successfully applied in order to model battery behavior without interfering with operation. It is shown that oxygen, hydrogen, and nitrogen are responsible for the pressure increase that occurs during overcharging. The relative contribution of the different gases depends on the current imposed on the battery as well as the operating temperature. Reproducible and stable signals could be obtained even under severe conditions such as high pressure and elevated temperature. Oxygen and hydrogen are produced in side reactions taking place during battery operation. However, as nitrogen is unlikely to be a reacting gas inside the battery, the change in its partial pressure can be attributed to electrode expansion and a change in the electrolyte volume.\u3c/p\u3

Distribution of aluminum phthalocyanine disulfonate in an oral squamous cell carcinoma model. In vivo fluorescence imaging compared with ex vivo analytical methods

Photosensitizer-induced fluorescence is studied as a technique for the detection of cancer, Therefore we investigated the ability of a photosensitizer, aluminum phthalocyanine disulfonate (AlPcS2), to localize in tumor tissue. In vivo endoscopic fluorescence imaging, fluorescence microscopy, conventional spectrofluorometry and high performance liquid chromatography combined with diode laser-induced fluorescence (HPLC-Dio-LIF) were used, Squamous cell carcinomas were induced with 4-nitro-quinoline-1-oxide (4NQO) in the mucosa of the palate of the rat, In vivo fluorescence images, taken after injection of 1.5 mu mol/kg AlPcS2 intravenously, showed that 4NQO-treated palates had higher fluorescence signals than normal palates, Areas displaying locally high amounts of AlPcS2 fluorescence (hot spots) were present only in 4NQO-treated rats 2-8 h but had disappeared 24 h after injection, However, HPLC-Dio-LIF showed that the relative AlPcS2 content was highest at 24/48 h in biopsies taken in the areas of the hot spots, Fluorescence microscopy revealed that AlPcS2 was present only between 2 and 8 h in the epithelial layer, while in biopsies the connective tissue contained large quantities of AlPcS2 at 24/48 h, In vivo fluorescence imaging appears to show mainly fluorescence from the epithelial layer and the ex vivo analytical techniques mainly show the connective tissue fluorescence. Care should be taken when interpreting data using one technique only

Modification of PEDOT:PSS as hole injection layer in polymer LEDs

\u3cp\u3ePoly(3,4-ethylenedioxythiophene):poly(styrenesulphonic acid) (PEDOT:PSS) is commonly used as an anode in polymer light-emitting diodes (PLED). We have studied the effect of the pH and Na\u3csup\u3e+\u3c/sup\u3e ion concentration of the aqueous PEDOT:PSS dispersion on the bulk and surface properties of spincoated films by various techniques, including UV-vis-NIR optical absorbance spectrometry, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoemission Spectroscopy (UPS). A pH increase by addition of NaOH modifies the PEDOT : PSS properties in a similar way as electrochemical dedoping: the IR absorbance decreases, the Raman peaks shift, sharpen and increase in intensity, and the work function decreases. Consequently, a barrier for hole injection is introduced for several classes of light-emitting polymers. We argue that the mechanism of the pH-effect is different from electrochemical dedoping, and originates from a change in the relative stability of polarons and bipolarons on the doped thiophene. The changes in the electronic properties of PEDOT:PSS point to the determining role of the counter-ion in the stabilisation of oxidised thiophene units. Polymer LEDs comprising Na\u3csup\u3e+\u3c/sup\u3e-rich, proton poor PEDOT:PSS can show lower lifetime and efficiency than the corresponding Na\u3csup\u3e+\u3c/sup\u3e-free, proton-rich devices. For light emitting polymers which suffer from the addition of sodium to the hole injecting PEDOT:PSS, the decreased lifetime hints at hole injection as limiting factor in the degradation of these PLEDs.\u3c/p\u3