Freeze-drying: An alternative method for the analysis of volatile organic compounds in the headspace of urine samples using solid phase micro-extraction coupled to gas chromatography - mass spectrometry

© 2016 Aggio et al. Background: Volatile organic compounds (VOCs) can be intermediates of metabolic pathways and their levels in biological samples may provide a better understanding about diseases in addition to potential methods for diagnosis. Headspace analysis of VOCs in urine samples using solid phase micro extraction (SPME) coupled to gas chromatography - mass spectrometry (GC-MS) is one of the most used techniques. However, it generally produces a limited profile of VOCs if applied to fresh urine. Sample preparation methods, such as addition of salt, base or acid, have been developed to improve the headspace-SPME-GC-MS analysis of VOCs in urine samples. These methods result in a richer profile of VOCs, however, they may also add potential contaminants to the urine samples, result in increased variability introduced by manually processing the samples and promote degradation of metabolites due to extreme pH levels. Here, we evaluated if freeze-drying can be considered an alternative sample preparation method for headspace-SPME-GC-MS analysis of urine samples. Results: We collected urine from three volunteers and compared the performances of freeze-drying, addition of acid (HCl), addition of base (NaOH), addition of salt (NaCl), fresh urine and frozen urine when identifying and quantifying metabolites in 4 ml samples. Freeze-drying and addition of acid produced a significantly higher number of VOCs identified than any other method, with freeze-drying covering a slightly higher number of chemical classes, showing an improved repeatability and reducing siloxane impurities. Conclusion: In this work we compared the performance of sample preparation methods for the SPME-GC-MS analysis of urine samples. To the best of our knowledge, this is the first study evaluating the potential of freeze-dry as an alternative sample preparation method. Our results indicate that freeze-drying has potential to be used as an alternative method for the SPME-GC-MS analysis of urine samples. Additional studies using internal standard, synthetic urine and calibration curves will allow a more precise quantification of metabolites and additional comparisons between methods

The "Enhancement" of Cultural Heritage by AMS Dating: Ethical Questions and Practical Proposals

The looting of archaeological and ethnographic objects from emerging countries and areas of conflict has prospered due to the high prices that these objects can achieve on the art market. This commercial value now almost necessarily requires proof of authenticity by the object's age. To do so, absolute dating has been conducted since the end of the 1970s on terra cotta art objects using the thermoluminescence method, a practice that has since been condemned. It is only more recently, since the 2000s, that art dealers and collectors have begun to use the accelerator mass spectrometry (AMS) method to date different kinds of objects made of organic materials. Compared to conventional radiocarbon dating, the AMS technique requires only very small samples, thus depreciating neither the aesthetics nor commercial value of the object. As a result, the use of absolute dating has become widespread, accompanying the increase in looting of the cultural heritage of countries destabilized by political overthrows and armed conflicts, especially in the Near East and Africa. The present article condemns the practice of AMS dating of looted art objects and encourages the creation of a code of deontology for 14C dating laboratories in order to enhance an ethical approach in this sensitive field facing the current challenges

Investigation of Volatile Organic Compounds Emitted from Faeces for the Diagnosis of Giardiasis

Background: Giardiasis is a common intestinal infection caused by the flagellated intestinal protozoan Giardia duodenalis. Several methods are available for the laboratory diagnosis of Giardia, ranging from the microscopic identification of the parasite trophozoite and cyst stages, to immunodiagnosis and PCR. Giardia has unique metabolic pathways resulting from its lack of mitochondria, making it an ideal target for volatile organic compound (VOC) profiling. Aim: To characterise the VOC profile of stool infected with Giardia to detect differences from those found in samples of diarrhoea without Giardia or other infections. Method: Stool was obtained from patients with confirmed Giardia infection and controls with diarrhoea but no identifiable infection. Faecal headspace gas extraction and gas chromatography-mass spectrometry were used to extract and identify VOCs. Results: More than 100 VOCs were identified when control and Giardia groups were combined, of which 24 showed significant differences between the two groups (p Conclusion: There is a significant difference in the VOC profile of stool from subjects infected with Giardia spp, when compared with non-infected controls. These findings can be explained by the unique metabolism of Giardia.</i

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Additional file 6. Column degradation. This csv file contains the metabolites defined as product of GC column degradation. This file can be visualised using a text editor

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Additional file 4. AMDIS configuration. This ini file contains the settings of the AMDIS software used in this study. Please see the user manual provided with AMDIS to obtain all the necessary information to use this configuration file when analysing GC-MS samples with AMDIS

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Additional file 5. Metabolite found in urine samples. This csv file contains the metabolites found in the samples analysed in this study. This file can be visualised using a text editor

Radiocarbon Dating and the Protection of Cultural Heritage

International audienc