Development of an autonomous on-site dissolved inorganic carbon analyzer using conductometric detection.

BACKGROUND: The increase in anthropogenic CO2 concentrations in the Earth's atmosphere since the industrial revolution has resulted in an increased uptake of CO2 by the oceans, leading to ocean acidification. Dissolved Inorganic Carbon (DIC) is one of the key variables to characterize the seawater carbonate system. High quality DIC observations at a high spatial-temporal resolution is required to improve our understanding of the marine carbonate system. To meet the requirements, autonomous DIC analyzers are needed which offer a high sampling frequency, are cost-effective and have a low reagent and power consumption. RESULTS: We present the development and validation of a novel analyzer for autonomous measurements of DIC in seawater using conductometric detection. The analyzer employs a gas diffusion sequential injection approach in a "Tube In A Tube" configuration that facilitates diffusion of gaseous CO2 from an acidified sample through a gas permeable membrane into a stream of an alkaline solution. The change in conductivity in the alkaline medium is proportional to the DIC concentration of the sample and is measured using a detection cell constructed of 4 hollow brass electrodes. Physical and chemical optimizations of the analyzer yielded a sampling frequency of 4 samples h-1 using sub mL reagent volumes for each measurement. Temperature and salinity effects on DIC measurements were mathematically corrected to increase accuracy. Analytical precision of ±4.9 µmol kg-1 and ±9.7 µmol kg-1 were achieved from measurements of a DIC reference material in the laboratory and during a field deployment in the southwest Baltic Sea, respectively. SIGNIFICANCE: This study describes a simple, cost-effective, autonomous, on-site benchtop DIC analyzer capable of measuring DIC in seawater at a high temporal resolution as a step towards an underwater DIC sensor. The analyzer is able to measure a wide range of DIC concentrations in both fresh and marine waters. The achieved accuracy and precision offer an excellent opportunity to employ the analyzer for ocean acidification studies and CO2 leakage detection in the context of Carbon Capture and Storage operations.

A pattern-recognition-based clustering method for non-invasive diagnosis and classification of various gastric conditions.

Conventional endoscopic biopsy tests are not suitable for early detection of the acute onset and progression of peptic ulcer as well as various gastric complications. This also limits its suitability for widespread population-based screening and consequently, many people with complex gastric phenotypes remain undiagnosed. Here, we demonstrate a new non-invasive methodology for accurate diagnosis and classification of various gastric disorders exploiting a pattern-recognition-based cluster analysis of a breathomics dataset generated from a simple residual gas analyzer-mass spectrometry. The clustering approach recognizes unique breathograms and "breathprints" signatures that clearly reflect the specific gastric condition of an individual person. The method can selectively distinguish the breath of peptic ulcer and other gastric dysfunctions like dyspepsia, gastritis, and gastroesophageal reflux disease patients from the exhaled breath of healthy individuals with high diagnostic sensitivity and specificity. Moreover, the clustering method exhibited a reasonable power to selectively classify the early-stage and high-risk gastric conditions with/without ulceration, thus opening a new non-invasive analytical avenue for early detection, follow-up, and fast population-based robust screening strategy of gastric complications in the real-world clinical domain.

Spectroscopic investigation of hydrogen and triple-oxygen isotopes in atmospheric water vapor and precipitation during Indian monsoon season.

Water vapor, the most important greenhouse gas in the atmosphere, has four natural stable isotopologues (H216O, H217O, H218O and HD16O), and their isotopic compositions can be used as hydrological tracers. But the underlying processes and pattern-dynamics of the isotopic compositions of atmospheric water vapor and precipitation in response to various meteorological conditions during monsoon season in a tropical hot and humid region is poorly understood. Here, we present results of H and triple-O-isotopes of water in precipitation and atmospheric water vapor during monsoon season exploiting high-resolution integrated cavity output spectroscopy technique. We observed a distinct temporal variation of the isotopic compositions of water at different phases of the monsoon. The diurnal patterns of the isotopic variations were influenced by the local meteorological factors such as temperature, relative humidity and amount of precipitation. We also investigated the monsoonal dynamics of the second-order isotopic parameters, so-called d-excess and 17O-excess along with the influence of local meteorological factors on isotopic variations to improve our understanding of the underlying isotopic fractionation processes. Consequently, our results provide a unique isotopic-fingerprint dataset of rainwater and atmospheric water vapor for a tropical region and thus shed a new light on hydrological and meteorological processes in the atmosphere.

Exploring Triple-Isotopic Signatures of Water in Human Exhaled Breath, Gastric Fluid, and Drinking Water Using Integrated Cavity Output Spectroscopy.

Water, the major body fluid in humans, has four main naturally occurring isotopologues, H216O, H217O, H218O, and H2H16O (i.e., HD16O) with different masses. The underlying mechanisms of the isotope-specific water-metabolism in the human gastrointestinal (GI) tract and respiratory system are largely unknown and remained illusive for several decades. Here, a new strategy has been demonstrated that provides direct quantitative experimental evidence of triple-isotopic signatures of water-metabolism in the human body in response to the individual's water intake habit. The distribution of water isotopes has been monitored in drinking water (DW; δD = -36.59 ± 10.64‰ (SD), δ18O = -5.41 ± 1.47‰ (SD), and δ17O = -2.92 ± 0.79‰ (SD)), GI fluid (GF; δD = -35.91 ± 7.30‰ (SD), δ18O = -3.98 ± 1.29‰ (SD), and δ17O = -2.37 ± 0.57‰ (SD)), and human exhaled breath (EB; δD = -119.63 ± 7.27‰ (SD), δ18O = -13.69 ± 1.23‰ (SD), and δ17O = -8.77 ± 0.98‰ (SD)) using a laser-based off-axis integrated cavity output spectroscopy (OA-ICOS) technique. This study explored a new analytical method to disentangle the competing effects of isotopic fractionations of water during respiration in humans. In addition, our findings revealed that deuterium-enriched exhaled semiheavy water, i.e., HD16O is a new marker of the noninvasive assessment of the ulcer-causing H. pylori gastric pathogen. We also clearly showed that the water-metabolism-derived triple-isotopic compositions due to impaired water absorption in the GI tract can be used as unique tracers to track the onset of various GI dysfunctions. These findings are thus bringing a new analytical methodology to better understand the isotope-selective water-metabolism that will have enormous applications for clinical testing purposes.