Determination of cholecalciferol (vitamin D3) in selected foods by liquid chromatography: NMKL collaborative study

Results are presented from an NMKL (Nordic Committee on Food Analysis) collaborative study of a method for the determination of cholecalciferol (vitamin D3) in foods. The method is based on the addition of an internal standard (vitamin D2), followed by saponification and extraction with n-heptane. The fraction that contains vitamin D2/D3 is separated by preparative normal-phase liquid chromatography (LC), and the analytes are determined by reversed-phase LC with UV detection at 265 nm. The method was tested by 8 participating laboratories. In this study 6 different matrixes were analyzed for cholecalciferol content: milk, liquid infant formula (gruel), cooking oil, margarine, infant formula, and fish oil. The contents varied from 0.4 to 12 microg/100 g. Three matrixes (milk, gruel, and margarine) were fortified with vitamin D3. In the other matrixes, vitamin D3 was added at 3 different levels at the Swedish National Food Administration. The milk was analyzed as a blind duplicate, whereas the other matrixes were analyzed as split-level pairs. The recoveries from the samples with vitamin D3 added varied from 93 to 102%. The repeatability relative standard deviation (RSDr) values for accepted results varied between 2.2% (fish oil) and 7.4% (cooking oil), whereas the reproducibility relative standard deviation (RSD(R)) values varied between 6.8% (margarine) and 24% (cooking oil).     

Viktor Anatol’evich Akulichev (On his 70th birthday)

Acoustical Physics -     

Preface: Second Symposium on New Techniques forthe Treatment of Sparse Matrices for Industrial Problems

The Second Séminaire sur les Techniques Nouvelles de Traitement des Matrices Creuses pour les Problèmes Industriels (Second Symposium on New Techniques for the Treatment of Sparse Matrices for Industrial Problems) was held at the Universitédes Sciences et Technologies de Lille, April 28–29, 1997. It followed the first one in Grenoble in February 1995. The organizing committee consisted of C. Brezinski (Université Lille), L. Colombet (CEA Grenoble), J. David (CEA Saclay), S. Petiton (Universitée Lille), N. Revol (Université Lille), Y. Saad (DCS Minneapolis) and D. Trystram (IMAG Grenoble).The local organizing committee consisted of C. Brezinski, C. Le Calvez, S. Petitonand N. Revol, all from the University of Lille. Around 100 participants attended the congress. They came from various universities and industries, some of them from Belgium, Great Britain, Morocco and the USA. The congress consisted of 13 one hour invited talks and a round table on methods and software for industrial problems. We thank all speakers for giving very interesting talks, thus making the congress very lively. Various aspects of numerical computations with sparse matrices were treated: new algorithms, effective handling of very large sparse systems, parallel techniques, preconditioning, direct and iterative methods, etc. This issue contains the papers corresponding to five of these invited talks and we very much appreciated the additional effort of their authors. We would like to thank the Université des Sciences et Technologies de Lille,the Commissariat à l'Energie Atomique, the Conseil Général de la Région Nord - Pasde Calais, the Laboratoire d'Informatique Fondamentale de Lille and the Laboratoired' Analyse Numérique et d'Optimisation de l'Université des Sciences et Technologies de Lille whose financial and logistic support made possible the organization and the success of the congress. This revised version was published online in August 2006 with corrections to the Cover Date.