Know the

«True» Sodium Content Consumers and regulatory agencies are pushing harder than ever for the accurate analysis of sodium in food products.

Because direct measurement methods have been cost-and time-prohibitive for testing labs – many food compa-nies have indirectly analyzed sodium through the analysis of chloride – but this can yield highly inaccurate results.

Here’s a fast and economical direct-testing meth od to accurately measure sodium con tent.



Analysis of Sodium in Foodstuffs by Thermometric Titration

Sodium has traditionally been indirectly tested using a Instruments and Accessories silver nitrate precipitation reaction: Equipment Required

859 Titrotherm

Titrant: Mixed 0.5 mol/L Al(NO ) =

AgNO + Cl

3 3

– → AgCl ↓ + NO –

0,5 mol/L and c(KNO ) = 1,1 mol/L.

3

3

3

Reagents Required

Complexation reagent: 300 g/L NH F.HF

4

The amount of sodium is typically calculated by assuming Waste neutralization solution: Saturated boric acid solution a 1:1 molar ration of chloride ions to sodium ions in the food. This is not necessarily the case when common so dium-containing food ingredients, such as sodium Experimental Results benzoate and monosodium glutamate, or chloride-con -

ICP

Titrotherm

taining ingredients such as potassium chloride, are pre -

Average

Average

sent in the food matrix – as well as sodium ions that may Sample I.D.

Sodium %

Sodium %

RSD

be present in the food itself.

Ketchup 1.3 1.3

0.008

Yellow Mustard

0.9

1.2

0.005

Common methods of testing the true amount of sodium Green Beans

0.2

0.3

0.011

directly have typically been atomic absorption spectros-Jamaican Jerk

Seasoned,

0.4

0.6

0.113

copy or inductively coupled plasma spectroscopy. Al though Potato Chips

specific to sodium for analysis, these techniques typically Mini Prezels

1.1

1.0

0.078

involve significant capital investments in equipment and infrastructure, costly ultra-pure reagents and lengthy sample preparation and system calibration.

Discussion of experimental results: Thermometric titration has been shown to be robust, Metrohm is excited to announce a method of direct ther-accurate and very precise. The results achieved with the mo metric titration of sodium in foodstuffs that is specific, 859 Titrotherm demonstrate that a titration using very rapid, robust and economical: simple and rapid sample preparation will allow the user to analyze sodium directly in a food sample.

Thermometric titration is a form of titration using either the heat of enthalpy produced by a chemical reaction to determine its endpoint. This method of titration is free from the electrochemical and solvent effects that are present in many types of titration making them difficult to adapt to some food matrices. To determine the amount of sodium the food is first masticated or homo -

genized to make a homogeneous mixture. The pre pared mixtures is then titrated with a standardized solution of aluminum containing a stoichiometric excess of potassium ions in the presence of ammonium hydrogen difluo-ride at ~pH 3 to give an exothermic reaction, forming td., Herisau

insoluble NaK AlF .

2

6

ohm L

Al3+ + Na+ + 2K+ + 6F– ↔ NaK AlF ↓

2

6

witzerland by Metr

The titrant is standardized against a solution prepared from anhydrous sodium sulfate.

, printed in S

www.metrohm.com

SW

fi cations

Subject to modi

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