Competency evaluation on electrolytic conductivity measurement in Indonesia by an unofficial bilateral comparison between RCChem-LIPI and NIMT

Accreditation and Quality Assurance - The Research Centre for Chemistry—Indonesian Institute of Sciences (RCChem-LIPI) organized an unofficial bilateral comparison on electrolytic...     

Comparative Analysis of Rhein Content in Cassia fistula Pod Extract by Thin-Layer Chromatographic-Densitometric and TLC Image Methods

JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid, and cost-effective thin-layer chromatography (TLC) image analysis was developed and validated to quantify rhein...     

Development of metrology for pH measurement in Thailand

It has not been long that metrology is well accepted as an important part in analytical chemistry since it helps the chemists to receive the best measurement and accurate results with traceability. The National Institute of Metrology Thailand (NIMT), which is a public agency under the supervision of the Ministry of Science and Technology, not only focuses on physical standards but also provides and maintains standards in chemical field. pH measurement is one of the most widely used in the laboratories including industries and medical area in Thailand. The chemical laboratory starts working on the project with the objective of disseminating an accurate result in routine pH measurement. In 2002, the laboratory provided a service in calibration of pH meter and organized the first local interlaboratory comparison program (NIMT–C-ILC-1: pH buffer) in pH measurement. There were three buffer solution samples in the range of acid, neutral, and base. A total of 44 laboratories participated in this program. The NIMT chemical laboratory also participated in the proficiency testing program that was conducted by PSB Corporation Testing Group in Singapore. In 2003, NIMT started research in preparation of secondary buffers by using highly accurate pH meters with glass electrode systems. The laboratory produced three secondary buffers, which were pH 4.01, 6.86, and 9.18 with uncertainty 0.020 pH at 25°C. The competence of the laboratory was shown by the measurement results of the pilot study (APMP.QM-P06), which was organized by the APMP electrochemical analysis working group (EAWG/TCQM) in 2005. The title of this study was “pH determination of two phosphate buffers by Harned cell method and glass electrode method”. NIMT aims to achieve for establishment of the primary method for pH measurement in the near future. Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA     

“Degrees of equivalence” for chemical measurement capabilities: primary pH

The key comparison (KC) studies of the Consultative Committee for Amount of Substance—Metrology in Chemistry help ensure the reliability of chemical and biochemical measurements relevant to international trade and environmental-, health-, and safety-related decision making. The traditional final evaluation of each measurement result reported by a KC participant is a “degree of equivalence” (DEq) that quantitatively specifies how consistent each individual result is relative to a reference value. Recognizing the impossibility of conducting separate KCs for all important analytes in all important sample matrices at all important analyte levels, emphasis is now shifting to documenting broadly applicable critical or “core” measurement competencies elicited through a series of studies. To better accomplish the necessary synthesis of results, data analysis and display tools must be developed for objectively and quantitatively combining individual DEqs. The information detailed in the 11 KCs of primary method pH measurements publically available as of 2013 provides an excellent “best case” prototype for such analysis. We here propose tools that enable documenting the expected primary pH measurement performance of individual participants between pH 1 and pH 11 and from 15 °C to 37 °C. These tools may prove useful for other areas where the uncertainty of measurement is a predictable function of the measured quantity, such as the stable gases. That results for relatively simple measurement processes can be combined using relatively simple analysis and display methods does not ensure that similarly meaningful summaries can be devised for less well understood and controlled systems, but it provides the incentive to attempt to do so.     

TLC-Densitometric Method for the Quantification of Crebanine in Stephania venosa (BI) Spreng

JPC – Journal of Planar Chromatography – Modern TLC -     

A polymer surface for antibody detection by using surface plasmon resonance via immobilized antigen

A polymer substrate based surface plasmon resonance (SPR) technique was developed for detection of specific monoclonal antibody 10B2 (MAb 10B2) against bacterium Acidovorax avenae subsp. citrulli (Aac). The monolayer of Aac antigen was physically immobilized on 95:5 polystryrene – copoly acrylic acid (95PSMA) for detection of antibody. The amount of antigen–antibody binding was found to depend on the surface density of immobilized Aac on the sensor surface and the antibody concentration. The detection limit was 5 μg/ml which was lower than the required concentration during the normal production of the antibody at 10–100 μg/ml. This suggests a possible use of surface for the antibody screening. Moreover, an application in antibody screening was explored by combination of surface plasmon resonance imaging (SPR imaging) and antibody detection assay on the 95PSMA surface. Two antigens of bovine serum albumin (BSA) and Aac were used as a model system for antibody screening. The result shows that both antibodies can be distinguished using the immobilized antigens on the 95PSMA surface based SPR imaging technique.