Microwaves: Cooking Up Lab Improvements

When one of the most widely used methods in the analytical laboratory also tops the lists of least-loved jobs, there has to be room for improvement. And for many years, this has been the situation with the Kjeldahl method for nitrogen (or protein nitrogen) analysis. Now 105 years old, this mainstay technology of many chemists in food laboratories has proved its worth for several reasons. First, unlike more modern instrument-based methods, the Kjeldahl method can be used on large sample sizes

Mike Spear
Jan 22, 1989

When one of the most widely used methods in the analytical laboratory also tops the lists of least-loved jobs, there has to be room for improvement. And for many years, this has been the situation with the Kjeldahl method for nitrogen (or protein nitrogen) analysis.

Now 105 years old, this mainstay technology of many chemists in food laboratories has proved its worth for several reasons. First, unlike more modern instrument-based methods, the Kjeldahl method can be used on large sample sizes (grams at a time), which makes it ideal for inhomogeneous materials like foodstuffs. Second, the equipment needed is simple and cheap. And third, the actual quantitation of nitrogen content involves no more than a straightforward acid-base titration.

But it's the route to that titration step that to many older chemists conjures up the hell's kitchen images of flasks of fuming acids. The traditional procedure involves an acid digestion of...

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