Molecular imaging of paper cross sections by FT-IR spectroscopy and principal component analysis

The molecular imaging of paper cross sections containing the wet-strength additive poly(amidoamine)–epichlorohydrin (PAE) was effected by Fourier transform infrared (FT-IR) spectroscopic imaging. Thin cross sections of laboratory sheet samples were prepared and transferred onto CaF₂ substrates. A laboratory sheet sample without PAE acted as a reference. Principal component analysis (PCA) was applied to identify and to reveal the distribution of PAE across the section. Differences in the loading plots of the fourth and fifth principal components for the sheets with and without PAE were found in the region of the amide I, amide II, and amine bands within a variance of 0.4–0.8 %. The score images of the PCA reveal inhomogeneous distribution of PAE. Small areas of higher concentration of PAE occur across the cross section. The aim of this study was to demonstrate that FT-IR spectroscopic imaging provides spatially resolved quantitative information about the chemical composition of paper, which was successfully achieved.

HPLC Method for the Simultaneous Determination of the UV-Filters Butyl Methoxy Dibenzoylmethane and Octocrylene in the Presence of Their Photodegradants

Butyl methoxy dibenzoylmethane (BMDM) and octocrylene (OC), common UV-filters in sunscreen products are often used in combination. Together they provide broad spectrum photoprotection from exposure to both UVA- and UVB-light. These UV-filters may, however, undergo photodegradation and generate photodegradants, resulting in a potential loss of photoprotection. It is thus a concern that the photostability testing as described by the ICH Guideline Q1B is not a requirement for sunscreen products in Australia, Europe or the USA. UV-filter photodegradants have in addition been shown to be toxic, highlighting the importance of their separation from the parent UV-filters. An HPLC method was developed and validated to quantitatively determine a combination of these UV-filters in the presence of their photodegradants. Reverse-phase chromatography was employed, using a C18 column and an isocratic mobile phase consisting of methanol/water/acetic acid (89/10/1 v/v). Validation according to the ICH guidelines for linearity, accuracy, precision, sensitivity, specificity and robustness was confirmed. The developed and validated method was then successfully applied to the determination of BMDM and OC in an aqueous cream base, typically used in sunscreens, after photostability testing, according to the ICH Guideline Q1B. In addition, the diketo-enol ratio of BMDM in methanol-d ₄ was determined by NMR and the two major photodegradants were identified by FTMS and LC–MS.

     

HPLC Method for the Simultaneous Determination of the UV-Filters Butyl Methoxy Dibenzoylmethane and Octocrylene in the Presence of Their Photodegradants

Butyl methoxy dibenzoylmethane (BMDM) and octocrylene (OC), common UV-filters in sunscreen products are often used in combination. Together they provide broad spectrum photoprotection from exposure to both UVA- and UVB-light. These UV-filters may, however, undergo photodegradation and generate photodegradants, resulting in a potential loss of photoprotection. It is thus a concern that the photostability testing as described by the ICH Guideline Q1B is not a requirement for sunscreen products in Australia, Europe or the USA. UV-filter photodegradants have in addition been shown to be toxic, highlighting the importance of their separation from the parent UV-filters. An HPLC method was developed and validated to quantitatively determine a combination of these UV-filters in the presence of their photodegradants. Reverse-phase chromatography was employed, using a C18 column and an isocratic mobile phase consisting of methanol/water/acetic acid (89/10/1 v/v). Validation according to the ICH guidelines for linearity, accuracy, precision, sensitivity, specificity and robustness was confirmed. The developed and validated method was then successfully applied to the determination of BMDM and OC in an aqueous cream base, typically used in sunscreens, after photostability testing, according to the ICH Guideline Q1B. In addition, the diketo-enol ratio of BMDM in methanol-d ₄ was determined by NMR and the two major photodegradants were identified by FTMS and LC–MS.     

Optical spectroscopic methods for intraoperative diagnosis

Molecular analytical methods are increasingly needed for a quick and reliable analysis of tissue in an operating room to provide more information during operations. In this Trends article, we highlight the current state and the developments of optical spectroscopic methods as intra operative tools. The clinical problem and challenges are illustrated on the example of brain tumor surgery. While fluorescence microscopy is already used, vibrational spectroscopy techniques will complement the standard method for brain tissue diagnostics. New portable instruments are currently available and can be stationed in the operating room for quick evaluation of tissue. The promise and limitations of fluorescence and vibrational spectroscopy as intraoperative tools are surveyed in this report.     

Method development and inter-laboratory comparison about the determination of titanium from titanium dioxide nanoparticles in tissues by inductively coupled plasma mass spectrometry

Nanosized titanium dioxide (TiO₂) is one of the most interesting and valuable nanomaterials for the construction industry but also in health care applications, food, and consumer goods, e.g., cosmetics. Therefore, the properties associated with this material are described in detail. Despite its widespread use, the analytical determination and characterization of nanosized metal oxides is not as straightforward as the comparatively easy-to-detect metallic nanoparticles (e.g., silver or gold). This study presents the method development and the results of the determination of tissue titanium (Ti) levels after treatment of rats with the nanosized TiO₂. Total Ti levels were chosen to evaluate the presence and distribution of TiO₂ nanoparticles. A procedure consisting of incubation with a mixture of nitric acid (HNO₃) and hydrofluoric acid (HF), and heating was developed to digest tissues and TiO₂ nanomaterials in order to determine the total Ti content by inductively coupled plasma mass spectrometry (ICPMS). For the inter-laboratory comparison, altogether four laboratories analyzed the same samples upon digestion using the available ICPMS equipment. A major premise for any toxicokinetic study is the possibility to detect the chemical under investigation in biological samples (tissues). So, the study has to be performed with a dose high enough to allow for subsequent tissue level measurement of the chemical under investigation. On the other hand, dose of the chemical applied should not induce over toxicity in the animal as this may affect its absorption, distribution, metabolism, and excretion. To determine a non-toxic TiO₂ dosage, an acute toxicity study in rats was performed, and the organs obtained were evaluated for the presence of Ti by ICPMS. Despite the differences in methodology and independent of the sample preparation and the ICPMS equipment used, the results obtained for samples with Ti concentrations >4 μg Ti/g tissue agreed well.

A Rapid,Highly Sensitive and Selective Phosgene Sensor Based on 5,6-Pinenepyridine

The toxicity of phosgene (COCl₂) combined with its extensive use as a reactant and building block in the chemical industry make its fast and accurate detection a prerequisite. We have developed a carboxylic derivative of 5,6-pinenepyridine which is able to act as colorimetric and fluorimetric sensor for phosgene in air and solution. For the first time, the formation of a pyrido-[2,1-a]isoindolone was used for this purpose. In solution, the sensing reaction is extremely fast (under 5 s), selective and highly sensitive, with a limit of detection (LOD) of 9.7 nM/0.8 ppb. When fixed on a solid support, the sensor is able to detect the presence of gaseous phosgene down to concentrations of 0.1 ppm, one of the lowest values reported to date.     

Quantum critical behaviour in Ce3Pd20Si6?

The cage compound Ce₃Pd₂₀Si₆ has recently been shown to undergo two successive low-temperature phase transitions which are strongly affected by an applied magnetic field. Here we show that, as the lower, probably antiferromagnetic transition is suppressed to zero in a field slightly above 1 T, the electrical resistivity shows a non-Fermi-liquid-like linear-in-T   temperature dependence while it follows the usual Fermi liquid T²$T^2$ temperature dependence both at smaller and larger fields. This suggests that a field-induced quantum critical point exists in Ce₃Pd₂₀Si₆.     

SrIr9In18 – A Structurally Complex Intermetallic Compound with Sr@Ir4In12, Ir@In8 and Ir@In9 Building Units

Single crystals of SrIr₉In₁₈ were obtained by induction melting of the elements in a glassy carbon crucible followed by annealing at 1070 K. SrIr₉In₁₈ was structurally characterized by X-ray powder and single crystal diffraction: P4 m2, a = 811.21(5), c = 854.49(5) pm, wR₂ = 0.0511, 1223 F² values, and 46 variables. The structure is of a new type. The basic building units are Ir@In₈ (distorted square-prismatic, square anti-prismatic and bicapped trigonal prismatic coordination) and Ir@In₉ (distorted trigonal prismatic coordination) polyhedra, which condense to a three-dimensional network, which leaves large cavities for the strontium cations, which are coordinated to four iridium and twelve indium atoms. The [Ir₉In₁₈]^2– polyanionic network is stabilized through Ir–In (267–290 pm) and In–In (302–354 pm) bonding.     

SrIrIn6 – An Intergrowth of SrIrIn4 with Indium Slabs

The indium-rich intermetallic compound SrIrIn₆ was synthesized from the elements in a sealed tantalum ampoule at 1173 K, followed by slow cooling for crystal growth. SrIrIn₆ crystallizes with a new structure type which was characterized by X-ray powder and single crystal diffraction: Pmma, a = 852.34(2), b = 434.54(5), c = 1059.18(6) pm, wR₂ = 0.0178, 884 F² values, and 32 variables. The SrIrIn₆ structure shows two basic building units: (i) Ir@In₉ tricapped trigonal prisms (261–292 pm Ir–In) and (ii) distorted bcc In@In₈ cubes (301 to 329 pm In–In). The strontium cations fill cages within the complex three-dimensional [IrIn₆] network and have coordination number 13 (Sr@In₁₃) in form of a tricapped pentagonal prism. The SrIrIn₆ structure can be described as a simple intergrowth variant of SrIrIn₄ (LaCoAl₄ type) with indium slabs. The crystal chemical similarities with the structures of SrIrIn₄, SrIr₂In₈ and Eu₃Ir₂In₁₅ are discussed.