The total analysis time was on average less than seven minutes, a huge time saving when compared with the traditional 'ashing' technique which can take over 24 hours
In May 2003, the UK Food Standards Agency (FSA) announced guidelines on maximum recommended salt intakes for children.
At the time, the Food Commission warned that with so much hidden salt in children's food, it would be hard for parents to achieve the targets without a significant reduction of salt in processed food.
The Food and Drink Federation (FDF, representing the food industry) announced that it would work with its industry members to reduce salt content in soups and sauces by 10%.
There have been mixed results in the successes of this over the last two years but one point is very clear; parents are more aware than ever before about the dangers of salt in food.
Market research has shown that parents more and more read the labels on processed food packaging and demand to know exactly what they are feeding their children.
It is the sodium in salt that leads to health problems, and the FSA recommends the salt intake for children ages 1-3 should be no more than 2g per day (that is 0.8g sodium per day).
All food manufacturers, not just of children's food, must label the sodium content, preferably expressed per 100g.
Metrohm UK can provide a simple analytical technique for sodium at a price all laboratories can afford, it says.
The determination of Na with the Na ISE represents a selective, rapid, accurate and favourably priced method (see Metrohm Application Bulletin 83/5).
The 6.0501.100 glass membrane ISE is recommended for samples with a difficult matrix such as food samples.
The Na ISE is connected to a Metrohm 781 pH/ion meter, the determinations are performed by establishing calibration curves or by carrying out standard or sample additions.
For the fully automatic standard addition users need only enter the concentration of the standard and the desired number of additions, the rest is taken care of by the pH/ion meter.
The working principle is simple: in aqueous solutions, cations are removed from the outer hydrated layer of the glass membrane and replaced by Na+ ions from the sample.
This creates a potential (that can be measured) at the boundary layer between the sample solution and the membrane that depends on the activity of sodium.
It is also necessary to add a total ionic strength adjustment buffer (Tisab) which fixes the ionic strength of the sample and buffers the pH values above 9, as measurements must be carried out in alkali conditions.
Difficult samples of complex matrices of vegetables, meat and fish have been recently sampled by Metrohm UK.
Reproducible results were obtained by sonicating a known weight of sample in 20ml of distilled water in a sonic bath for five minutes before adding Tisab and analysing.
The total analysis time was on average less than seven minutes, a huge time saving when compared with the traditional 'ashing' technique which can take over 24 hours.
Metrohm UK can provide a fast, simple and reasonably priced technique for sodium analysis in the food industry.
