A New Automated Method and Sample Data Flow for Analysis of Volatile Nitrosamines in Human Urine

Volatile nitrosamines (VNAs) are a group of compounds classified as probable (group 2A) and possible (group 2B) carcinogens in humans. Along with certain foods and contaminated drinking water, VNAs are detected at high levels in tobacco products and in both mainstream and side-stream smoke. Our laboratory monitors six urinary VNAs—N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPIP), N-nitrosopyrrolidine (NPYR), and N-nitrosomorpholine (NMOR)—using isotope dilution GC-MS/ MS (QQQ) for large population studies such as the National Health and Nutrition Examination Survey (NHANES). In this paper, we report for the first time a new automated sample preparation method to more efficiently quantitate these VNAs. Automation is done using Hamilton STARTM and Caliper StaccatoTM workstations. This new automated method reduces sample preparation time from 4 hours to 2.5 hours while maintaining precision (inter-run CV < 10%) and accuracy (85% - 111%). More importantly this method increases sample throughput while maintaining a low limit of detection (<10 pg/mL) for all analytes. A streamlined sample data flow was created in parallel to the automated method, in which samples can be tracked from receiving to final LIMs output with minimal human intervention, further minimizing human error in the sample preparation process. This new automated method and the sample data flow are currently applied in bio-monitoring of VNAs in the US non-institutionalized population NHANES 2013-2014 cycle.

Constraints and Opportunities for Detecting Land Surface Phenology in Drylands

Land surface phenology(LSP)enables global-scale tracking of ecosystem processes,but its utility is limited in drylands due to low vegetation cover and resulting low annual amplitudes of vegetation indices(VIs).Due to the importance of drylands for biodiversity,food security,and the carbon cycle,it is necessary to understand the limitations in measuring dryland dynamics.Here,using simulated data and multitemporal unmanned aerial vehicle(UAV)imagery of a desert shrubland,we explore the feasibility of detecting LSP with respect to fractional vegetation cover,plant functional types,VI uncertainty,and two different detection algorithms.Using simulated data,we found that plants with distinct VI signals,such as deciduous shrubs,can require up to 60%fractional cover to consistently detect LSP.Evergreen plants,with lower seasonal VI amplitude,require considerably higher cover and can have undetectable phenology even with 100%vegetation cover.Our evaluation of two algorithms showed that neither performed the best in all cases.Even with adequate cover,biases in phenological metrics can still exceed 20 days and can never be 100%accurate due to VI uncertainty from shadows,sensor view angle,and atmospheric interference.We showed how high-resolution UAV imagery enables LSP studies in drylands and highlighted important scale effects driven by within-canopy VI variation.With high-resolution imagery,the open canopies of drylands are beneficial as they allow for straightforward identification of individual plants,enabling the tracking of phenology at the individual level.Drylands thus have the potential to become an exemplary environment for future LSP research.

Interactions of extracellular DNA with aromatized biochar and protection against degradation by DNaseⅠ

With increasing environmental application,biochar(BC)will inevitably interact with and impact environmental behaviors of widely distributed extracellular DNA(eDNA),which however still remains to be studied.Herein,the adsorption/desorption and the degradation by nucleases of eDNA on three aromatized BCs pyrolyzed at 700℃were firstly investigated.The results show that the eDNA was irreversibly adsorbed by aromatized BCs and the pseudo-second-order and Freundlich models accurately described the adsorption process.Increasing solution ionic strength or decreasing pH below 5.0 significantly increased the eDNA adsorption on BCs.However,increasing pH from 5.0 to 10.0 faintly decreased eDNA adsorption.Electrostatic interaction,Ca ion bridge interaction,andπ-πinteraction between eDNA and BC could dominate the eDNA adsorption,while ligand exchange and hydrophobic interactions were minor contributors.The presence of BCs provided a certain protection to eDNA against degradation by DNase I.BC-bound eDNA could be partly degraded by nuclease,while BC-bound nuclease completely lost its degradability.These findings are of fundamental significance for the potential application of biochar in eDNA dissemination management and evaluating the environmental fate of eDNA.