High Precision Titrimetry, Ion Chromatography and ICP-Optical Emission Spectrometry for the Estimation of Inhomogeneities in Aqueous Calibration Solutions for Metrological Purposes

Abstract

The homogeneity of samples intended for metrological intercomparison studies must be granted without ambiguity. This holds equally true for aqueous solutions for which the determination of betweenbottle variations requires measurement techniques with extremely high precision. Therefore measurement series were designed for automated analysis techniques such as titrimetry, optical emission spectrometry and ion chromatography which offer very high precision of results. Between-bottle relative standard deviations (RSD) of at best 0.008% were obtained with titrimetry. With optical emission spectrometry and ion chromatography, between-bottle RSD's of 0.02% and 0.05% were obtained. The contributions from these measurements were included in a conservative approach to the uncertainty budgets of the gravimetrical reference values for the analytes in the samples.

Ion Analysis at the Highest Stage ? The Metrological Approach by National Metrological Institutes

“…humidity during 120 days. No significant evaporation was observed when the bottles were welded into mylar bags [7]. The final mass fractions of the analyte in the sample solutions shipped were in the range of 0.988 g kg À1 up to 1.020 g kg À1 with respect to the corresponding ion.…”

“…The solutions were homogenised in an FEP-coated mixing tank by tumbling them for 12 hours, and the solutions were filled into 250 mL PP bottles using a closed loop system to minimise evaporation and contamination. An intensive between-bottle inhomogeneity study was performed in every case [7]. The stability of the packed samples in terms of evaporation was investigated by exposing the closed bottles to air at a temperature of 295 K and 50% rel.…”

Metrological evaluation of the certification of primary reference materials characterized by high-precision constant-current coulometry for the reliability of the titration analyses

“…The homogeneity studies for the three candidate CRMs were developed using the one-way ANOVA analysis based on the ISO Guide 35 [12] and considering other recommendations [13,14,35,36]. Table 1 presents the results of the homogeneity studies carried out on the candidate CRMs of KHP, KCl, and dichromate.…”

Building-up a Double Accredited CRM Production Laboratory in an Industrial Environment: A Description

“…This was demonstrated when this equipment was used for the preparation of samples for interlaboratory comparisons at the highest metrological stage. [12] Last but not least, the standard solution is bottled under clean room conditions avoiding any contamination during the transfer process of the liquid. The bottles containing the CRM are then properly labelled, sealed into multilayered non-transmissible bags and stored under controlled conditions.…”