NMKL, Nordic Committee on Food Analysis, wishes you all a lovely summer!!

New methods:

Cholecalciferol (vitamin D₃) and Ergocalciferol (vitamin D₂). Determination by HPLC in foodstuffs.  No. 167, 2000 (Click on the title to read more)

Nitrite and Nitrate. Nitrite and/or nitrate in foodstuffs by ion chromatography.  No. 165, 2000 (Click on the title to read more)

Oxalic acid, Determination in foods. No. 63, 2. Ed. , 2000 (Click to on the title read more)

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Cholecalciferol (vitamin D₃) and Ergocalciferol (vitamin D₂). Determination by HPLC in foodstuffs.

(NMKL No. 167, 2000)

A method performance study of the method used at the National Food Administration, Sweden, for determination of vitamin D, was carried out in autumn 1997. Laboratories in Sweden, Norway, Denmark, Finland and Switzerland participated in the study. Relatively few laboratories analyse vitamin D, therefore only 8 laboratories participated in this study, which is somewhat less than recommended by IUPAC.

The method is applicable to the determination of vitamin D in both natural, as well as enriched, foodstuffs. Six matrices (milk, gruel, gruel powder, margarine, cocking oil and fish oil) were used in the study, whereof three matrices were fortified with vitamin D₃ and three matrices had been supplemented with varying levels before shipment to the laboratories.

The principle of the method is based on the extraction of vitamin D3 using n-heptane, following the addition of an internal standard, (vitamin D2) and basic hydrolysis. If vitamin D₂ is to be determined, vitamin D₃ is added. It is assumed that the internal standard does not naturally occur in the sample. The fraction that contains vitamin D3/D2 is separated by prepa­rative straight phase liquid chromatography (Silica). After evaporation and solubilising in aceto­nitrile/methanol, the vitamin D3 or D2 is quantitatively determined by reversed phase liquid chromatography (C-18).

The challenge in the method lies in the preparative work. Interference can occur at several points. If the fraction is not eluted correctly or a column with unsatisfactory resolution is used, it will influence the chromatogram for  quantitative determination.   

Anders Staffas

NMKL  thanks  Anders Staffas and the National Food Administration, Sweden, for this important work and the extensive  resources used in the elaboration and collaborative validation of the method.

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Nitrite and Nitrate. Nitrite and/or nitrate in foodstuffs by ion chromatography.

(No. 165, 2000)  

As early as the Annual Meeting in 1989, it was decided to propose measurement of nitrite and nitrate in meat products, using HPLC, as a new topic. A method performance study was performed in 1993. Ten laboratories participated, arranged by Ingmar Berntsson at the National Food Administration, Sweden. Unfortunately, the study showed that this method could not be approved, the statistical estimate for the reproducibility of the method at the concentrations in common being too high. CEN (the European Standardisation organisation) were also looking for a suitable method for the determination of nitrite and nitrate. Leonardo Merino, National Food Administration, Sweden, was appointed as a NMKL referee in 1997. A “French method”, a former European Pre-standard, was optimalised and validated, both internally and collaboratively, by Leonardo Merino and Ulla Edberg. Two studies of the method were performed in accordance with the IUPAC rules.  Since CEN also had an interest in the method, the study was international, with seventeen laboratories participating from Europe. The results of this method performance study were satisfactory and a method for the determination of nitrite and nitrate could eventually be approved.

The method describes an ion chromatographic procedure for the determination of residual nitrite and nitrate contents in different foodstuffs. The limits of detection for nitrite and nitrate ions are 1 and 10 mg/kg respectively.

The principle for the method uses the extraction of nitrite and nitrate from the test sample, in hot water. The aqueous solution is treated with acetonitrile to remove any interfering substances. The nitrite and nitrate contents of the solutions are then determined by ion chromatography and UV detection at 205 nm.

NMKL  thanks  Leonardo Merino, Ulla Edberg and the National Food Administration, Sweden, for validating the method internally and collaboratively.

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Oxalic acid, Determination in foods.

(NMKL No. 63, 2. Ed., 2000)

Revisions from the previous edition, (1967), are mainly editorial. The method has been  upgraded, normality has been converted to molarity, and effort has been made to make the text more reader-friendly. The method includes determination of total amount of oxalic acid, water-soluble oxalic acid and acetic acid-soluble oxalic acid in foods. The method is not validated collaboratively within NMKL.

The test sample is extracted with hydrochloric acid, respectively water or acetic acid. The extract is purified by precipitation with tungstenate-phosphoric acid reagent, and oxalic acid is precipitated in the filtrate with calcium chloride. The precipitate is dissolved in sulphuric acid, and the liberated oxalic acid is determined by titration with potassium permanganate.

NMKL Secretary General, Hilde Skår Norli at the National Veterinary Institute, Norway, carried out  the revision of this method.

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NMKL Referees appointed since Sept. 99 (previous Annual Meeting)

NMKL’s most important function is to propose, collaboratively validate and publish methods in food analysis. A referee with competence in the appropriate field is appointed for each topic. The following referees have been appointed for the period of 1999/2000, in the following topics:

NMKL thanks the referees appointed in 99/00, and their institutions,  for undertaking the important task of elaborating and validating NMKL methods.

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NMKL’s 54th Annual Meeting, at Bornholm, August 26 – 29, 2000 (click here for programme)

The Danish National Committee of NMKL has invited members of NMKL and cooperative organisations to Hotel Fredensborg, Rønne, on Bornholm, Denmark, for NMKL’s 54^th Annual Meeting.

All topics on the working programme are to be discussed at the Annual Meeting. The activities are organised into four-subcommittees chaired by:

Sub committee 1 – executive
Chairperson: Dir. Ole Bjørn Jensen, Scanpharm, Denmark

Sub committee 2 – microbiology
Chairperson: Dr. Per Norberg, National Food Administration, Sweden

Sub committee 3 – chemistry
Chairperson: Prof. Kåre Julshamn, Institute of Nutrition, Directorate of Fisheries, Norway

Sub committee 4; Sensory
Chairperson: Dr. Halina Agerhem; Swedish Meats AB, Sweden

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A new edition of AOAC INTERNATIONAL’s
method collection is available

This month, AOAC INTERNATIONAL is issuing the 17^th edition of
Official Methods of Analysis of AOAC INTERNATIONAL. The new edition contains 2700 validated methods, whereof more than 200 are new and modified methods. All the methods has been thoroughly reviewed and revised by General Referees of AOAC INTERNATIONAL under the guidance of Dr. William Horwitz, who is also the editor of this collection.

The compiled collection is available on CD-rom and in print.

For further information see AOAC’s homepage: http://www.aoac.org or contact AOAC on Fax: +1-301-924-7087 or Tel: +1-300-924-7077.

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Do you want to learn more about genetically modified foods?

See the program for the seminar to be held August 25 on Bornholm, and register.

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New secretaries in NMKL’s national committees during this year:

Inge Meyland, Danish Veterinary and Food Administration, who succeeds Lene Bønnelycke Hansen as secretary for the Danish committee of NMKL.

Gunilla Everitt, National Food Administration, Sweden, takes over from Annica Jannson as the secretary for the Swedish committee. Annica has been secretary for the Swedish committee for more than 16 years and will be deeply missed, not only by the Swedes, but also by all the NMKL’ers who have had the pleasure of knowing her.

NMKL gives thanks to Lene and Annica for their efforts. Inge and Gunilla, who are already involved in NMKL, are both warmly welcomed.

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NMKL method no 71, 2000: ”Salmonella. Detection in Foods” is now also available in Finnish.

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