Nordic scientists test sodium detection methods

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Related tags: Spectroscopy

The Nordic Committee on Food Analysis (NMKL) has identified flame
atomic absorption spectrometry after microwave digestion as a
viable means of determining sodium content in foodstuffs.

A project group was established headed by Kåre Julshamn from the National Institute of Nutrition and Seafood Research (NIFES) in Norway in order to analyse the existing means of testing foodstuffs for salt content.

Nearly one third of food shoppers are making a special effort to cut down on salt, and are reading the food label for content, according to the UK's Food Standards Agency, because European consumers are increasingly aware that high levels of salt intake are believed to be linked to high blood pressure, leading to cardiovascular difficulties.

But at least 26 million people in the UK alone eat more than the recommended maximum daily intake. Approximately 75 per cent of salt consumed is from processed foods, 10-15 per cent added by consumers and 10-15 per cent is naturally present in food.

Limiting the intake of salt has therefore become a nutritional aim across Europe, with manufacturers obliged to reveal the salt contect of their products. In the Nordic countries previous projects conducted at Norwegian municipal food control laboratories on the salt content in foodrevealed that a number of different analytical methods were in use, and that it was difficult to compare the obtained results.

The Nordic Committee on Food Analysis (NMKL) therefore believed that a collaboratively validated method was needed.

Prior to the elaboration and collaborative study of the finalmethod, two preliminary studies were arranged. Theparticipants of these studies were the project members and theirlaboratories. In these preliminary studies the sodium contentwas determined in 30 sample solutions and four homogenised drysamples.

The laboratories used their own methods. Flame atomic emissionspectrometry, flame atomic absorption spectrometry, ionselective electrode for sodium and inductive coupled plasmaatom emission spectroscopy were all used.

According to the results, theanalysis techniques did not yield different results except for theion selective electrode, which had a higher determination limitthan the other methods.

NMKL​ decided that the NMKL method for sodium should be based on atomicabsorption spectrometry after microwave digestion. Ninelaboratories participated in the collaborative study of thesodium method. The method was tested on six foodstuffs:(broccoli, carrot, bread, saithe fillet, pork, and cheese) withsodium concentrations ranging from 1480-8260 mg/kg.

Thematerials were presented to the participants in the study as blindduplicates. The repeatability relative standard deviations (RSDr)for sodium varied between 1.9 per cent to 6.0 per cent.

The reproducibility relative standard deviations (RSDR) ranged from 4.2 per cent to 6.9 per cent.The HorRat values varied between 0.9 and 1.6. HorRat valuesless than 2 indicate that the method's performance is satisfactory.

Jens JørgenSloth from the Danish Institute for Food and Veterinary Research(DFVF), Riitta Kivikari from the University of Helsingfors, HeidaPálmadóttir, Icelandic Fisheries Laboratories, Frank Lundby,Matforsk AS from the Norwegian Food Research Institute and MartinRiebe from Swedish Nestle also participated in the study.

Related topics: Food Safety & Quality

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