Journal of Chemical Metrology Articles

A certified reference material (UME CRM 1309) of sucrose for carbon isotope ratio: d 13 C VPDB (‰) value was produced according to the requirements of the ISO Guide 34:2009. The certified value with uncertainty was determined as -26.78 ± 0.81 ‰ (at k=2) by Elemental Analyzer Isotope Ratio Mass Spectrometry (EA-IRMS) method. Production and the certification processes include material processing, homogeneity study, stability studies (short-term and long-term), characterization study, statistical data evaluation and assignment of the property value and uncertainty. The d 13 C VPDB certified value of sucrose was determined by an inter-laboratory comparison study among a network of seven competent laboratories.

An HPLC-UV method for the determination of thiosulfate in aqueous media was modified and validated in this study to quantify the amount of residual thiosulfate in omeprazole samples. Absorption of thiosulfate ion was monitored at 215 nm in alcoholic tetrabutylammonium hydroxide solution as a mobile phase, in which the pH was adjusted to 6.20 by using dilute hydrochloric acid. A method detection limit of 0.08 mg/L was achieved for thiosulfate ion in 1000 mg/L omeprazole solution. The precision, accuracy, and the expanded uncertainty of the method were 2.7 %, 92.4-102.6 %, and 2.2 % (at 95 % confidence level (k = 2) assuming 1.0 mg/L thiosulfate in the sample solution), respectively.