International comparison of the determination of the mass fraction of cadmium, chromium, mercury and lead in polypropylene: the Comité Consultatif pour la Quantité de Matière pilot study CCQM-P106

The CCQM-P106 pilot study was organized by the inorganic working group of the Comité Consultatif pour la Quantité de Matière (CCQM) as a feasibility comparison to study the applicability of different analysis methods to the polypropylene sample and test the abilities of the participants for measuring the Cd, Cr, Hg and Pb in polypropylene. National Institute of Metrology P.R. China (NIM) acted as the coordinating laboratory of this pilot study. There were 21 laboratories that submitted the final results. The median values of the mass fraction of Cd, Cr, Hg and Pb were 36.12 mg kg^?1 (the median absolute deviation about the median (MADe) = 0.46 mg kg^?1), 252.5 mg kg^?1 (MADe = 3.4 mg kg^?1), 387.0 mg kg^?1 (MADe = 10.1 mg kg^?1) and 466.2 mg kg^?1 (MADe = 8.9 mg kg^?1), respectively. Isotope dilution mass spectrometry (IDMS), inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-optical emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS), instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) measurement methods were used, and microwave digestion was used by the most of the participants. In general, very good agreement of the results was observed. Moreover, compared to the results of other methods, the results of IDMS still showed less spread amongst laboratories and had a smaller uncertainty. In addition, the results of some analytes used by XRF and INAA also got satisfactory agreement with the median value.     

New reference material for analysis of elements in glutinous rice produced at the National Institute of Metrology (Thailand)

Reference materials play an important role for evaluating the accuracy of analytical results, and are essential parts of good laboratory practice. They represent a key tool for quality control of chemical analyses. In Thailand, the demand of food and environmental reference materials is constantly increasing, and the National Institute of Metrology (NIMT, Thailand) is responding to the urgent needs for affordable materials, which require collaborative efforts at the national level. This paper describes the preparation of a new glutinous rice reference material, along with homogeneity and stability studies and the analytical work carried out for the certification of the contents of inorganic elements. The incurred material was collected from an actual rice paddy field. Material preparation along with homogeneity and stability testing were carried out at the Environmental Research Training Centre (ERTC). The homogeneity study was designed to have three experimental conditions; (A) 10 bottles of candidate materials being analyzed each with 2 replicates, (B) 20 bottles with 2 replicates, (C) 10 bottles with 7 replicates, in order to study the suitable treatments for homogeneity testing in the reference material production. It was shown that a minimum number of 10 bottles with duplicate analyses are enough to demonstrate the homogeneity of candidate reference material. Certification of a candidate reference material in a single laboratory using reference method was confirmed with an interlaboratory comparison participated by a certain number of well recognized testing laboratories in Thailand. Further elaborative results will be discussed.     

International comparison of the determination of cadmium and lead in herb: the Comité Consultatif pour la Quantité de Matière (CCQM) pilot study CCQM-P97

A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of the 13 participants were 0.3186 mg kg⁻¹ (RSD = 11.3%) and 1.650 mg kg⁻¹ (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users. The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest metrological IDMS approach gave a better precision than other routine calibration methods.     

Impact of Periodically Generated Hydrodynamic Disturbances on the Condensation Efficiency of R134a Refrigerant in Pipe Mini-Channels

This article discusses an experimental analysis of the influence of periodically generated external hydrodynamic disturbances on the condensation process of the R134 refrigerant in circular pipe mini-channels. The investigations were carried out for horizontal single mini-channels with internal diameters in the range of d = 0.64–3.30 mm. It was established that within the range of frequencies under investigation (f = 0.2–5 Hz), i.e., the frequencies at which disturbances are generated, the disturbances exert an influence on the structure of the characteristic condensation areas in the mini-channel. The disturbances have an unfavorable impact on the reduction of the two-phase length of specific condensation and a reduction of the heat flux in this area. The heat removal intensity in the two-phase area has an impact on the efficiency of the operation of a compact condenser. The impact of more important parameters on this efficiency is discussed.