Labconco Open Combination (Macro) Kjeldahl Systems 21237 Series - Manual (Page 6)

Chapter 1: Introduction
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Performance
The Open Combination Kjeldahl Digestion and Distillation Systems have
been designed for use in the determination of nitrogen (or ammonia)
concentrations. By calculation nitrogen can be converted to protein values for
products such as plant tissues, meats and other food substances. Nitrogen
determinations with the Open Combination (Macro) Kjeldahl Systems can
accommodate sample sizes up to 5 grams due to the size of the
digestion/distillation flasks. However, higher levels of organic content within
a specific sample type will require smaller sample sizes due to the vigorous
digestion reaction. Detailed procedures developed by professional laboratory
organizations such as American Association of Analytical Chemists (AOAC)
and American Association of Cereal Chemists (AACC) should always be
consulted for step by step analytical procedures when operating this
equipment. For methodology precision and accuracy please consult the
specific published method for the type of sample or substance that will be
analyzed.
Component Identification
1. Electric Heaters. 600-watt heaters are used in both the lower digestion
and upper distillation rack of the unit. Infinite control switches regulate
each of the heaters. The curved heater elements are provided and allow
for the round base of the Kjeldahl Flasks, providing faster and more
evenly distributed heat. The heating element assembly on the digestion
rack can be moved closer to or away from the acid fume removal
manifold to accommodate different size Kjeldahl flasks. All heaters and
temperature controllers are wired to a common electrical box for
connection to a facility electrical service.
2. Lower Fume Removal Manifold. Located in back of the digestion
heater elements, this manifold is manufactured from chemical resistant
chlorinated polyvinyl chloride and fitted with heat resistant Teflon
®
nipples designed to prevent leakage of the hot sulfuric acid fumes created
during the digestion process. The nipple design, extends in to the flask
opening, and efficiently removes excess acids fumes during the digestion
process. The flasks are oriented at a 45 degree angle to the fume removal
manifold to promote the condensation and refluxing of the acid fumes
back down into the digestion flask. This refluxing process prevents the
samples from boiling dry during the 45+ minute digestion process.
Component features #3 or #4 are selected by the customer when the
product is ordered. The Kjeldahl units described in this manual
feature either the blower exhaust or water ejector exhaust system to
remove the digestion fumes through the fume manifold system.
® Teflon is a registered trademark of E. I. du Pont de Nemours and Company or its affiliates.