Peter Kusch

Analysis of residual styrene monomer and other volatile organic compounds in expanded polystyrene by headspace solid‐phase microextraction followed by gas chromatography and gas chromatography/mass spectrometry

A method for determination of residual styrene monomer and other volatile organic compounds in expanded polystyrene (EPS) was developed using HS SPME and gas chromatography with FID. The extraction products were identified by GC/MS. Good reproducibility of the measurements with RSD values between 3.2–3.6% was achieved by extraction using a 75 μm Carboxen-Polydimethylsiloxane fiber at 60°C with 15 min sample sonication. The contents of residual styrene monomer in two samples of EPS were 153.2 and 65.7 mg/kg, respectively. Other compounds identified in EPS were pentane, benzene, toluene, ethylbenzene, isomers of xylene, n-propylbenzene, 1,2,4-trimethylbenzene, o-methylstyrene, benzaldehyde, benzyl alcohol, and acetophenone.

In Vitro and In Vivo Antimalarial Activity Assays of Seeds from Balanites aegyptiaca: Compounds of the Extract Show Growth Inhibition and Activity against Plasmodial Aminopeptidase.

Balanites aegyptiaca (Balanitaceae) is a widely grown desert plant with multiuse potential. In the present paper, a crude extract from B. aegyptiaca seeds equivalent to a ratio of 1 : 2000 seeds to the extract was screened for antiplasmodial activity. The determined IC50 value for the chloroquine-susceptible Plasmodium falciparum NF54 strain was 68.26 μg/μL ± 3.5. Analysis of the extract by gas chromatography-mass spectrometry detected 6-phenyl-2(H)-1,2,4-triazin-5-one oxime, an inhibitor of the parasitic M18 Aspartyl Aminopeptidase as one of the compounds which is responsible for the in vitro antiplasmodial activity. The crude plant extract had a K i of 2.35 μg/μL and showed a dose-dependent response. After depletion of the compound, a significantly lower inhibition was determined with a K i of 4.8 μg/μL. Moreover, two phenolic compounds, that is, 2,6-di-tert-butyl-phenol and 2,4-di-tert-butyl-phenol, with determined IC50 values of 50.29 μM ± 3 and 47.82 μM ± 2.5, respectively, were detected. These compounds may contribute to the in vitro antimalarial activity due to their antioxidative properties. In an in vivo experiment, treatment of BALB/c mice with the aqueous Balanite extract did not lead to eradication of the parasites, although a reduced parasitemia at day 12 p.i. was observed.

Pyrolysis-Gas Chromatography/Mass Spectrometry of Polymeric Materials

Examples of application of pyrolysis-gas chromatography-mass spectrometry technique for identification of different polymeric materials are demonstrated.

Completing the hypusine pathway in Plasmodium

In searching for new targets for antimalarials we investigated the biosynthesis of hypusine present in eukaryotic initiation factor‐5A (eIF‐5A) in Plasmodium. Here, we describe the cloning and expression of deoxyhypusine hydroxylase (DOHH), which completes the modification of eIF‐5A through hydroxylation of deoxyhypusine. The dohh cDNA sequence revealed an ORF of 1236 bp encoding a protein of 412 amino acids with a calculated molecular mass of 46.45 kDa and an isoelectric point of 4.96. Interestingly, DOHH from Plasmodium has a FASTA SCORE of only 27 compared with its human ortholog and contains several matches similar to E‐Z‐type HEAT‐like repeat proteins (IPR004155 (InterPro), PF03130 (Pfam), SM00567 (SMART) present in the phycocyanin lyase subunits of cyanobacteria. Purified DOHH protein displayed hydroxylase activity in a novel in vitro DOHH assay, but phycocyanin lyase activity was absent. dohh is present as a single‐copy gene and is transcribed in the asexual blood stages of the parasite. A signal peptide at the N‐terminus might direct the protein to a different cellular compartment. During evolution, Plasmodium falciparum acquired an apicoplast that lost its photosynthetic function. It is possible that plasmodial DOHH arose from an E/F‐type phycobilin lyase that gained a new role in hydroxylation.

Application of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and scanning electron microscopy (SEM) in failure analysis for the identification of organic compounds in chemical, rubber, and automotive industry

Abstract For failure analysis, there often is a lack of information about the component itself, such as chemical composition, temperature resistance, possible contaminants, or mechanical properties. The damage range usually is limited and not always homogeneous. Very often, only small amounts of samples are available, which may be important for recognizing the cause of damage. Traditional analytical techniques used for characterization of high molecular weight organic compounds, such as thermal analysis and Fourier transform infrared spectroscopy (FTIR), have limitations or are not sufficiently sensitive to demonstrate the change of the structure and the resulting dysfunction of used materials. The analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has extended the range of possible tools for the characterization of synthetic polymers/copolymers or rubbers in failure analysis in various industrial fields of application, predominantly in the automotive industry. In this report, we describe applications of analytical Py-GC/MS and scanning electron microscopy in failure analysis of chemical materials such as motor vehicle brake fluids, varnishes, and rubber materials of car tires. Failure cases demanding identification of polymers/copolymers in paint on the surface of a rubber membrane from the pressure vessel of an automotive integral accumulator and identification of the composition of sludge on the surface of the compressor wall from car air conditioner are reported. Furthermore, the identification of scaling of a valve block unit from a failed medical oxygen resuscitation apparatus is demonstrated. The obtained analytical results demonstrate clearly the benefit for troubleshooting and remedial action of the technological process.

Identification and Application of Corrosion Inhibiting Long- Chain Primary Alkyl Amines in Water Treatment in the Power Industry

Gas chromatography with flame-ionization detection (FID) and gas chromatography-mass spectrometry (GC/MS) with electron impact ionization (EI) and chemical ionization (PCI and NCI) were successfully used for separation and identification of commercially available longchain primary alkyl amines. The investigated compounds were used as corrosion inhibiting and antifouling agents in a water-steam circuit of energy systems in the power industry. Solidphase extraction (SPE) with octadecyl bonded silica (C18) sorbents followed by gas chromatography were used for quantification of the investigated Primene JM-T™ alkyl amines in boiler water, condensate and superheated steam samples from the power plant. Amine formulations from Kotamina group favor formation of protective layers on internal surfaces and keep them free from corrosion and scale. Alkyl amines contained in those formulations both render the environment alkaline and limit the corrosion impact of ionic and gaseous impurities by formation of protective layers. Moreover, alkyl amines limit scaling on heating surfaces of boilers and in turbine, ensuring failure-free operation. Application of alkyl amine formulation enhances heat exchange during boiling and condensation processes. Alkyl amines with branched structure are more thermally stable than linear alkyl amines, exhibit better adsorption and effectiveness of surface shielding. As a result, application of thermostable long-chain branched alkyl amines increases the efficiency of anti-corrosive protection. Moreover, the concentration of ammonia content in water and in steam was also considerably decreased.

Identification of Polymeric Residues in Recycled Aluminium by Analytical Pyrolysis-Gas Chromatography-Mass Spectrometry

A method for the identification of polymeric residues in recycled aluminium by using analytical pyrolysis at 700°C hyphenated to gas chromatography-mass spectrometry (Py-GC/MS) was presented for the first time. The polymeric residues in recycled aluminium were identified as a mixture of polyethylene, polystyrene, and phenolic resin. The described method could be useful for the aluminium industry as a part of the quality control of the recycled aluminium production.

Mass Spectrometry: Pyrolysis

Pyrolysis mass spectrometry (PyMS) is a sensitive analytical technique in which samples are subjected to rapid thermal degradation (pyrolysis) before the derivative ions are separated in a mass spectrometer. The technique is particularly suitable for the analysis of otherwise nonvolatile compounds in complex samples. The masses of pyrolyzate are expressed as a pyrolysis mass spectrum. This can be interpreted and used to characterize the structures of the parent molecules in the sample, or used in an uninterpreted manner to provide a diagnostic fingerprint that can easily distinguish between related complex samples, such as different microbial strains. The article describes the development of pyrolysis mass spectrometry and its history, the state of the art, instrumentation and applications for the identification of high molecular organic compounds by using of multivariate analysis and supervised learning methods.

Chemical Structures of Thermal Stable Long-Chain n-Alkyl Amines Used in Corrosion Inhibiting Formulations in Water-Steam and Heating Water Systems in the Power Industry

Gas chromatography with flame-ionization detection (FID) and gas chromatography-mass spectrometry (GC/MS) has been used for structure elucidation of long-chain primary n-alkyl amines after derivatization with trifluoroacetic anhydride (TFAA). Electron impact ionization- (EI) and positive chemical ionization- (PCI) mass spectra of trifluoroacetylated derivatives of the identified nalkyl amines are presented. The corrosion inhibiting n-alkyl amines were applied in the investigation of a new anticorrosive and antifouling formulation for water-steam circuit of energy systems in the power industry. The presented results are part of an EU-funded international collaboration with partners from research institutes and industry from Poland, Lithuania, Romania, France and Germany (EUREKA project BOILTREAT E!2426).