Analysis of VOCs in Liquids through Vaporization in a Tubular Oven Monitored by Chemical Ionization Mass Spectrometry.

The analysis of chemical compounds present at trace levels in liquids is important not only for environmental measurements but also, for example, in the health sector. The reference technique for the analysis of Volatile Organic Compounds (VOCs) in liquids is GC, which is difficult to use with an aqueous matrix. In this work, we present an alternative technique to GC to analyze VOCs in water. A tubular oven is used to completely vaporize the liquid sample deposited on a gauze. The oven is heated in the presence of a dinitrogen flow, and the gas is analyzed at the exit of the oven by a chemical ionization mass spectrometer developed in our laboratory. It is a low magnetic field Fourier Transform Ion Cyclotron Resonance (FT-ICR) optimized for real-time analysis. The Proton Transfer Reaction (PTR) used during the Chemical Ionization event results in the selective ionization of the VOCs present in the gas phase. The optimization of the desorption conditions is described for the main operating parameters: temperature ramp, liquid quantity, and nitrogen flow. Their influence is studied using a 100 ppmv aqueous toluene solution. The analytical method is then tested on a mixture of seven VOCs.

Quantification of monoamine biomarkers in cerebrospinal fluid: Comparison of a UHPLC-MS/MS method with a UHPLC coupled to fluorescence detection method.

Inborn errors of monoamine neurotransmitter metabolism are rare genetic diseases classified as catecholamine and serotonin metabolism disorders or neurotransmitter transportopathies. To diagnose these orphan diseases, monoamine metabolites have been identified and validated as cerebrospinal fluid (CSF) biomarkers: 5-hydroxy-tryptophane, 5-hydroxy-indol-acetic acid, 3-ortho-methyl-DOPA, homovanillic acid, and 3-methoxy-4-hydroxyphenylglycol. The present work presents a UHPLC-MS/MS method developed for the quantification of these metabolites in CSF and compares it with a previously described UHPLC with fluorescence detection (UHPLC-FD) method. MS/MS detection was performed in positive electrospray ionization and multiple reaction monitoring mode. The UHPLC-MS/MS and UHPLC-FD methods were validated in terms of accuracy, linearity, precision and matrix effect. The lower limits of quantification (LLOQ) ranged between 0.5 and 10 nm and between 1 and 5 nm for the UHPLC-MS/MS method and the UHPLC-FD one, respectively. We verified the applicability of both methods by analyzing 30 CSF samples. The measured concentrations were comparable with the reference values described in the literature. The two methods allowed pathological samples to be distinguished from healthy ones for clinical diagnosis. UHPLC-MS/MS and UHPLC-FD methods exhibited very close LLOQs. As the UHPLC-MS/MS method is more selective, it allows faster analysis with a run time of 6 min per run vs. 10 min for the UHPLC-FD method.