The storage capability of Tedlar® bags for gaseous compounds was assessed using on-line proton-transfer-reaction mass spectrometry (PTR-MS). Sample bags were filled with a mixture of volatile organic compounds (VOCs) at known quantities in the ppbv range. The test gas included alcohol, nitrile, aldehyde, ketone, terpene and aromatic compounds. PTR-MS enabled frequent bag-direct measurements of compound abundances over a 70 h storage period. Concentrations of all compounds decreased with bag storage time, with compound-specific decay rates. The most rapid decline in concentration levels was seen for water vapour in the bag, i.e. sample humidity. Such a decrease is particularly relevant for breath-gas samples, where water vapour content is high. Compound losses were attributed to a combination of adsorption to and diffusion through the bag walls. Storage property observations suggest that sample analyses made within 10 h of sampling offer adequate sample authenticity replication. Based on observations, an appropriate bag-cleaning procedure was established and assessed. Results indicated that acceptable bag cleanliness for breath-gas sampling is achievable.

We report on the implementation of proton transfer reaction-mass spectrometry (PTR-MS) technology for on-line monitoring of volatile organic compounds (VOCs) in the off-gas of bioreactors. The main part of the work was focused on the development of an interface between the bioreactor and an analyzer suitable for continuous sampling of VOCs emanating from the bioprocess. The permanently heated sampling line with an inert surface avoids condensation and interaction of volatiles during transfer to the PTR-MS. The interface is equipped with a sterile sinter filter unit directly connected to the bioreactor headspace, a condensate trap, and a series of valves allowing for dilution of the headspace gas, in-process calibration, and multiport operation. To assess the aptitude of the entire system, a case study was conducted comprising three identical cultivations with a recombinant E. coli strain, and the volatiles produced in the course of the experiments were monitored with the PTR-MS. The high reproducibility of the measurements proved that the established sampling interface allows for reproducible transfer of volatiles from the headspace to the PTR-MS analyzer. The set of volatile compounds monitored comprises metabolites of different pathways with diverse functions in cell physiology but also volatiles from the process matrix. The trends of individual compounds showed diverse patterns. The recorded signal levels covered a dynamic range of more than five orders of magnitude. It was possible to assign specific volatile compounds to distinctive events in the bioprocess. The presented results clearly show that PTR-MS was successfully implemented as a powerful bioprocess-monitoring tool and that access to volatiles emitted by the cells opens promising perspectives in terms of advanced process control.

We report on the search for low molecular weight molecules-possibly accumulated in the bloodstream and body-in the exhaled breath of uremic patients with kidney malfunction. We performed non-invasive analysis of the breath gas of 96 patients shortly before and several times after kidney transplantation using proton-transfer-reaction mass spectrometry (PTR-MS), a very sensitive technique for detecting trace amounts of volatile organic compounds. A total of 642 individual breath analyses which included at least 41 different chemical components were carried out. Correlation analysis revealed one particular breath component with a molecular mass of 114 u (unified atomic mass units) that clearly correlated with blood serum creatinine, which is the currently accepted marker for assessing the function of the kidney. In particular, daily urine production showed good correlation with the identified breath marker. An independent set of seven samples taken from three patients at the onset of dialysis and three controls with normal kidney function confirmed a significant difference in concentration between patients and controls for a compound with a molecular mass of 114.1035 u using high mass resolving proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS). A chemical composition of C7H14O was derived for the respective component. Fragmentation experiments on the same samples using proton-transfer-reaction triple-quadrupole tandem mass spectrometry (PTR-QqQ-MS) suggested that this breath marker is a C7-ketone or a branched C7-aldehyde. Non-invasive real-time monitoring of the kidney function via this breath marker could be a possible future procedure in the clinical setting.

No abstract

Mass spectrometry has been frequently applied to monitor the O₂ and CO₂ content in the off-gas of animal cell culture fermentations. In contrast to classical mass spectrometry the proton transfer reaction mass spectrometry (PTR-MS) provides additional information of volatile organic compounds by application of a soft ionization technology. Hence, the spectra show less fragments and can more accurately assigned to particular compounds. In order to discriminate between compounds of non-metabolic and metabolic origin cell free experiments and fed-batch cultivations with a recombinant CHO cell line were conducted. As a result, in total eight volatiles showing high relevance to individual cultivation or cultivation conditions could be identified. Among the detected compounds methanethiol, with a mass-to-charge ratio of 49, qualifies as a key candidate in process monitoring due to its strong connectivity to lactate formation. Moreover, the versatile and complex data sets acquired by PTR MS provide a valuable resource for statistical modeling to predict non direct measurable parameters. Hence, partial least square regression was applied to the complete spectra of volatiles measured and important cell culture parameters such as viable cell density estimated (R²  = 0.86). As a whole, the results of this study clearly show that PTR-MS provides a powerful tool to improve bioprocess-monitoring for mammalian cell culture. Thus, specific volatiles emitted by cells and measured online by the PTR-MS and complex variables gained through statistical modeling will contribute to a deeper process understanding in the future and open promising perspectives to bioprocess control.

Re´sume´-Suivi en temps re´el des concentrations de gaz traceurs dans un extrait de gaz de synthe`seUn spectrome`tre de masse par re´action de transfert de protons (PTR-MS, Proton Transfer Reaction -Mass Spectrometer) a e´te´utilise´pour l'analyse de gaz de synthe`se dans un proce´deí ndustriel Fischer-Tropsch. Un PTR-MS peut de´tecter une grande varie´te´de compose´s organiques et inorganiques volatils en temps re´el et avec une sensibilite´e´leve´e. Associe´a`un multiplexeur, il permet un suivi en ligne (en temps re´el) des contaminants a`l'e´tat de traces a`diffe´rents stades d'un proce´de´Fischer-Tropsch. Plusieurs compose´s volatils, tels que HCN, H 2 S, RSH, des carbonyles, des acides, des alcools et autres, ont e´te´mesure´s dans du gaz de synthe`se. Cet article de´crit la configuration pour le suivi du gaz de synthe`se en utilisant le PTR-MS et re´sume le re´sultat de ce projet de preuve de concept.Abstract -Real-Time Monitoring of Trace Gas Concentrations in Syngas -A Proton Transfer Reaction Mass Spectrometer (PTR-MS) was used for the analysis of syngas in an industrial Fischer-Tropsch process. A PTR-MS can detect a variety of volatile organic and inorganic compounds in real-time and with high sensitivity. Together with a multiplexer, this allows for online (real-time) monitoring of the trace contaminations at different stages of a Fischer-Tropsch process. Several volatile compounds, such as HCN, H 2 S, RSH, carbonyls, acids, alcohols and others have been measured in syngas. This paper describes the setup to monitor syngas using PTR-MS and summarizes the result of this proof-of-principle project.

A clinical study was conducted on the application of photodynamic therapy on tumours in the head and neck region to assess the value of this new modality for superficial cancer (Tis-T2). Patients with recurrent laryngeal papillomatosis were included in a photodynamic treatment pilot study. 2 mg/kg body weight of haematoporphyrin-derivative (Photosan-3) was administered 48 hours prior to laser irradiation intravenously. The patients rooms were advised to avoid daylight for two to three weeks. Tumours of the facial skin were irradiated homogeneously by means of an optical bench. Directly after laser application we observed an extensive extravasation of the tumour tissue, whereas the surrounding normal tissue showed mild erythema. A dry crust formed subsequently, which disappeared within two weeks associated with re-epithelisation. Mucous membrane tumours showed fibrin layers in the tumour area 24 hours after laser application with selective tumour necrosis. These lesions also epithelised completely within three weeks. Scarring never occurred. Laryngeal tumours as well as laryngeal papillomas were treated by a cylindrical light applicator system and the patients admitted to intensive care unit for 24 hours after laryngoscopy because of risk of laryngeal oedema. 94 patients with tumours of the head and neck with different histological origins were treated photodynamically, as well as 21 patients with laryngeal papillomatosis. Two months after photodynamic laser treatment, controlled biopsies of the former tumour area were performed. 5 patients had a relapse during a maximum follow-up of 4.5 years. This signified a histologically confirmed full response rate of 95%, accompanied by good plastic and functional results.(ABSTRACT TRUNCATED AT 250 WORDS)

Shock wave lithotripsy of salivary gland stones has become more and more efficient in the treatment of sialolithiasis during the last years. We use two different methods in our hospital: Extracorporeal shock wave lithotripsy (ESWL) and endoscopically intracorporeal lithotripsy (EISL). The results of both therapies are compatible; 60-70% could be successfully treated. The indication is different due to the localisation of the salivary gland stone. Stones that are located in the glandula or very proximal in the duct should be fragmented by extracorporeal lithotripsy. Stones located in the duct and multiple intraductal stones should be treated by the intracorporeal method. Clinical experiments showed that some salivary stones do not fragment easily. The reason is still unknown. We examined the ability of fragmentation in relation to the physicochemical analysis of the stone. The stones were examined by infrared spectroscopy. This study revealed that pure carbonate apatite stones are more difficult to destroy than stones containing some protein.