A simple method for routine measurement of organosulfur compounds in complex liquid and gaseous matrices.

The measurement of VOSCs in complex matrices is challenging due to their volatile and reactive nature. A straightforward method using headspace chromatography was developed for routine analyses of organosulfur compounds in a high saline liquid matrix with a pH of 8.4. Direct sample acidification with a 1M acetate buffer (pH 3.6) showed an increased response for methanethiol, ethanethiol, propanethiol, dimethyl sulfide, dimethyl disulfide and diethyl disulfide. A good quadratic fit (R2 <0.995) was obtained for each compound over a calibration range of 5 µM-S until 125 µM-S (µmol sulfur/L). Gas standards were measured using the same chromatographic conditions over a calibration range of 0.08 µM-S until 1.85 µM-S (R2 <0.999). Gas standards could also be used to calibrate the liquid phase with a response ratio of 105.2% for ET, 107% for DMS, 105.7% for PT, 108.9% for DMDS and 106% for DEDS. This alternative calibration strategy reduced the preparation time and does not rely on liquid standards, which were unstable over time. This method was used to determine Henry constants for the organosulfur compounds both in demineralized water and the high saline liquid matrix and to analyze samples from a bio electrochemical experiment that treated methanethiol. This new method allows for routine analysis of samples originating from natural gas desulfurization plants and can potentially also be used to analyze organosulfur compounds in other complex waste streams.

In†situ Biofilm Quantification in Bioelectrochemical Systems by using Optical Coherence Tomography.

Detailed studies of microbial growth in bioelectrochemical systems (BESs) are required for their suitable design and operation. Here, we report the use of optical coherence tomography (OCT) as a tool for in situ and noninvasive quantification of biofilm growth on electrodes (bioanodes). An experimental platform is designed and described in which transparent electrodes are used to allow real-time, 3D biofilm imaging. The accuracy and precision of the developed method is assessed by relating the OCT results to well-established standards for biofilm quantification (chemical oxygen demand (COD) and total N content) and show high correspondence to these standards. Biofilm thickness observed by OCT ranged between 3 and 90 µm for experimental durations ranging from 1 to 24 days. This translated to growth yields between 38 and 42 mgCODbiomass gCODacetate -1 at an anode potential of -0.35 V versus Ag/AgCl. Time-lapse observations of an experimental run performed in duplicate show high reproducibility in obtained microbial growth yield by the developed method. As such, we identify OCT as a powerful tool for conducting in-depth characterizations of microbial growth dynamics in BESs. Additionally, the presented platform allows concomitant application of this method with various optical and electrochemical techniques.