Journal of Chemical Metrology Articles

In 2004, the National Metrology Institute of South Africa, NMISA (then the National Metrology Laboratory of the CSIR, South Africa) was requested by forensic testing laboratories to coordinate a proficiency testing scheme for the determination of ethanol in blood. This led to an annual proficiency testing scheme where the test materials used are aqueous ethanol certified reference materials prepared and certified by NMISA. This article describes the development of the scheme and the progress made by the regular participants in the scheme over twelve years. The ethanol concentrations of the test samples were between 0.01 g/ 100 g and 0.6 g/ 100 g. The measurement uncertainty and the expected method performance were conveniently estimated from the data collected over the years.

Proficiency testing of laboratories in Turkey to compare and evaluate their performances on analysis of fatty acids in sunflower oil was performed. Analysis of the quality control test material allows the laboratory to compare the analytical results with other laboratories.In order to increase the quality of chemical analysis and awareness of metrology, TÜBİTAK UME have been organizing Proficiency Testing Schemes in the field of determination of fatty acids in sunflower oil since 2005. In this study, an overview of the proficiency test for the determination of fatty acids in sunflower oil in Turkey is presented.

A new, selective, sensitive and accurate method for determination of molybdenum by adsorptive catalytic stripping voltammetry was described. The method is based on catalytic reduction of adsorbed Mo(VI)-ARS complex onto the lead film electrode in the presence of chlorate used as oxidizing agent. The instrumental and solution parameters affecting the peak current were optimized. The calibration graph is linear between 2.65-20.00 µg/L Mo(VI) and limit of detection is estimated as 0.79 µg/L. The proposed method was applied to drinking water samples with satisfactorily recovery results and the uncertainty calculation of the method was performed.

Nowadays, genetically modified (GM) plants are widely used in several commercial products. Corn, cotton, soybean and canola are the most widely consumed foods globally and their derived products have reached the global markets. Specifically, corn has the greatest diversity of approved GM events globally (a total of 130 varieties approved in one or more countries). It is one of the most widely used food and feed ingredient, highly integrated into food and feed supply chains. Since GMOs carry environmental risks and human health related risks, it is required that the food and their ingredients that either contain GMOs or derived from GMOs should be labelled. In this study, we investigated the taxon-specific cauliflower mosaic virus 35S promoter region (CaMV) and Agrobacterium tumefaciens nonpalin synthase terminator (tNOS) gene in addition to the control gene of High Mobility Group (HMG). Corn-containing foods were obtained from grocery stores in Turkey. DNA extraction was performed by modified CTAB DNA extraction method for all samples and genomic DNA were extracted. The DNA extracts were screened by qPCR and it was shown that genetically modified DNA sequences of tNOS and CaMV were not present in the samples investigated. For the security of society, randomized screens should be carried out by scientist in random bases.

A simple, rapid, sensitive, robust, stability-indicating HPLC analytical protocol was developed and validated for the analysis of Ibuprofen, Pseudoephedrine Hydrochloride, and Chlorpheniramine Maleate in syrup formulation. The samples were assayed by the Waters HPLC instrument using a GL Sciences Inertsil ODS4 column (250 mm length × 4.6 mm width; 5 μm particle size) under timed gradient conditions. The flow rate of the mobile phase was 1.2 mL/min and the eluent was monitored at 214 nm. The method was validated by determining precision, linearity and range, specificity, accuracy and recovery, and robustness. The developed chromatographic method proved to be simple, precise, accurate, robust and reproducible. Moreover, the samples showed stability at room temperature over a period of 55 h. Thus, this method would be employed for routine simultaneous quantification of Ibuprofen, Pseudoephedrine Hydrochloride, and Chlorpheniramine Maleate in Syrup formulation.

In this study, leaf proportional water content, chlorophyll a and b, total chlorophyll, carotenoid, proline, total amino acid, ascorbic acid, glucose, fructose and sulphydryl group (SH) were determined in both Viscum album ssp. album and its hosts. Physiological alterations in soft-core fruits such as Ankara pear, Braeburn apple and hawtorn when infected with Viscum album ssp. album were investigated. While proportional water content of V. a. ssp. album was found higher than all fruit trees with or without V. album (control), its chlorophyll a content was lower than only control and two hosts (Braeburn apple and Ankara pear). Chlorophyll b content, on the other hand, was similar in all experimental groups for Ankara pear and hawthron whereas, in Braeburn apple, it was significantly higher in control. As for the total chlorophyll and carotenoid contents of V.a. ssp. album, in Breaburn and Ankara pear, they were found less than the controls and hosts whilst in hawthorn, the values were variable. Although proline content of V. a. ssp. album was higher compared to their controls and hosts, total amino acid, reduced and total ascorbic acid, glucose, fructose and sulphydryl acid in V. a. ssp. album were determined to be lower than all uninfected fruits (control).

In this study, an ID-GC-TOF-MS method was developed and validated for polycyclic aromatic hydrocarbons (PAHs) by spiking solutions onto thermal desorption tubes using calibration solution loading ring (CSLR) apparatus and sweeping them by the aid of air stream. Once the method was developed and validated, the effect of other compounds found in biogas and biomethane was investigated by the same methodology used in method development by using a gravimetrically prepared biogas mixture consisting of 45% methane, 40% carbon dioxide and 15% nitrogen. There are standard reference methods for measurements of PAHs in air but there was no available standard method for PAHs in biogas and biomethane yet. This study provides a basis for the future studies to develop a standard method. Data obtained through this study showed that present method is not affected by the compounds found in biogas that are not present in other matrices such as ambient air.

TÜBİTAK UME, the national metrology institute of Turkey has become involved in the development of reference materials since 2000, when the first proficiency test was organized for the field laboratories. After 2009, TÜBİTAK UME has established a clean chemistry laboratory for reference measurements and state-of-the-art reference material processing and storage facilities in collaboration with EC-JRC, European Commission Joint Research Center, Belgium which is one of the world’s leading developer and producer of reference materials. Accelerated with these studies, TÜBİTAK UME scientists focused on reference material production, certification and development of reference measurement techniques, giving first priority to environmental monitoring, food safety and clinical measurements. Simultaneously, the necessary procedures and documentation have been prepared and integrated to the quality management system of the institute to produce and certify reference materials according to the ISO Guide 34 (General Requirements for the Competence of Reference Material Producers). ISO Guide 34 transformed to the standard ISO 17034:2016 which requires the reference material producer to assess each of its production and testing systems, assigns an uncertainty value to all reference materials classified as “Certified Reference Material-CRM” and demonstrates traceability of measurements to SI units wherever possible. In 2016, TÜBİTAK UME has become the first reference material producer in Turkey accredited according to the ISO Guide 34. A total of 18 certified reference materials whose certifications have been completed since 2013 were included in its accreditation scope.