Enhancing LOD determination in gas chromatography: Validating the Hubaux-Vos method for gas concentration measurement.

The limit of detection (LOD) is a crucial measure in analytical methods, representing the smallest amount of a substance that can be distinguished from background noise. In the realm of gas chromatography (GC), however, determining LOD can be quite subjective, leading to significant variability among researchers. In this study, we validate the Hubaux-Vos method, an International Standards Organization(ISO)-approved approach for determining LOD in gas concentration measurements, using a GC equipped with a discharge ionization detector (DID) and a dynamic dilution system. We employ a gas mixture certified reference material (CRM) of CO, CH4, and CO2 at various concentrations to generate calibration curves for each gas. Subsequently, we estimate the LODs for each gas using the Hubaux-Vos method. Surprisingly, our findings indicate a notable difference between the LODs calculated using the Hubaux-Vos method and those confirmed through experiments. This highlights the importance of critically examining the theoretical foundations of LOD determination. We strongly recommend researchers to scrutinize the principles guiding LOD determination. The method proposed in this study offers an effective way to rigorously validate theoretical approaches for estimating LODs in gas concentration measurements using GC.

Adsorptive removal of gaseous methyl iodide by triethylenediamine (TEDA)-metal impregnated activated carbons under humid conditions.

Removal of gaseous radioactive iodine (131I and 129I) compounds from nuclear facilities is an important issue. Herein we assessed the adsorptive capacity of gaseous non-radioactive methyl iodide (CH3127I) as a simulant on two commercial TEDA-metal impregnated activated carbon(AC)s. The characterizations of the ACs were determined ICP-MS, XPS, and 77 K N2 isotherms. As a result, it was found that one AC has a small amount of TEDA but a well-developed porosity, and the other one was abundant with TEDA, but the porosity was relatively less developed. The methyl iodide removal performances were evaluated under 10 ppm and 400 ppm using breakthrough experiments under various relative humidities (RH). Desorption was also carried out using nitrogen after adsorption to investigate adsorption affinity. Methyl iodide adsorption capacity of TEDA-rich AC decreased significantly as RH increased at 10 ppm. Conversely, performance degradation was clearly observed from less TEDA-impregnated AC with well-developed porosity as RH increased at 400 ppm. It is demonstrated that the amount of physisorbed methyl iodide is decreased as RH increased. Although moisture decreases the adsorption amount, it enhances the adsorption affinity. Also, additional TEDA impregnation to ACs results in improving the performance under severe condition (RH90%, 400 ppm).

A Case of Isolated Adenomatous Polyp of Rectum in a Child: Tubulovillous adenoma / 대한소아소화기영양학회지

Isolated rectal adenomatous polyp without genetic background is rarely found in children. A 4-year and 5 month-old girl was admitted for intermittent bloody stools lasting 4 months. A 1.5x1.2 cm sized rectal polyp was found by air contrast barium enema. Endoscopic polypectomy was performed without complications. In histopathologic examination, it was found to be a tubulovillous adenoma. Typical radiologic, colonoscopic, and pathological pictures are presented.