A new heated capillary photoionization (CPI) ion source design was developed to photoionize analytes inside a transfer capillary between a gas chromatograph (GC) and a mass spectrometer (MS). The CPI setup included a wide, oval-shaped vacuum-ultraviolet (VUV) transparent magnesium fluoride (MgF2) window to maximize photoionization efficiency and thus sensitivity. The source contained a nitrogen housing around the ionization chamber inlet to avoid undesirable hydrolysis and oxidation reactions with ambient air and to maximize the proportion of formed molecular radical cations of analytes. The feasibility of the ion source was studied by analyzing 18 endogenous steroids in urine as their trimethylsilyl (TMS) derivatives with gas chromatography-tandem mass spectrometry (GC-MS/MS). The method was validated and applied to human urine samples. To our best knowledge, this is the first time that a capillary photoionization ion source has been applied for quantitative analysis of biological samples. The GC-CPI-MS/MS method showed good chromatographic resolution (peak half-widths between 3.1 to 5.3 s), acceptable linearity (coefficient of determination between 0.981 to 0.996), and repeatability (relative standard deviation (RSD%) between 5 to 18%). Limits of detection (LOD) were between 2 to 100 pg mL(-1) and limits of quantitation (LOQ) were between 0.05 to 2 ng mL(-1). In total, 15 steroids were quantified either as a free steroid or glucuronide conjugate from the urine of volunteers. The new CPI source design showed excellent sensitivity for analysis of steroids in complex biological samples. (C) 2019 Elsevier B.V. All rights reserved.

Proteomic and genomic techniques have reached full maturity and are providing unforeseen details for the comprehensive understanding of disease pathologies at a fraction of previous costs. However, for kidney diseases, many gaps in such information remain to inhibit major advances in the prevention, treatment and diagnostics of these devastating diseases, which have enormous global impact. The discovery of ubiquitous extracellular vesicles (EV) in all bodily fluids is rapidly increasing the fundamental knowledge of disease mechanisms and the ways in which cells communicate with distant locations in processes of cancer spread, immunological regulation, barrier functions and general modulation of cellular activity. In this review, we describe some of the most prominent research streams and findings utilizing urinary extracellular vesicles as highly versatile and dynamic tools with their extraordinary protein and small regulatory RNA species. While being a highly promising approach, the relatively young field of EV research suffers from a lack of adherence to strict standardization and carefully scrutinized methods for obtaining fully reproducible results. With the appropriate guidelines and standardization achieved, urine is foreseen as forming a unique, robust and easy route for determining accurate and personalized disease signatures and as providing highly useful early biomarkers of the disease pathology of the kidney and beyond.