The HotBlock TKN (total Kjeldahl nitrogen) digestion system from Environmental Express is preprogrammed to automate digestion protocols (EPA Method 351.2) for determining organic nitrogen. It can heat up to 450 degrees C (842 degrees F). The optional touch-screen controller can store up to eight programs, including TKN. Up to 20 steps can be set up automatically for each digestion procedure.

The controller is programmed to ramp the temperature of the block to 160 degrees C and hold that temperature for 60 minutes. It then automatically ramps to 380 degrees C over 60 minutes and holds that temperature for an additional 30 minutes.

“The TKN method requires a temperature of up to 380 degrees C,” says Joe Boyd, tech specialist with Environmental Express. “Most heating blocks don’t go that high. This one will achieve that temperature with the accuracy that’s required by the method.”

To withstand the high temperature and highly corrosive nature of the TKN procedure, the block, tube stand and cooling rack are constructed of 316 stainless steel.
“There is a second distillation step that may be required in the TKN method,” Boyd says. “Our glassware will fit directly into our SimpleDist System and do the distillation in the same glassware, so you eliminate a transfer step going from one set of glassware to the next.”

The system is available with 28- (22 1/2 inches wide by 16 inches high by 12 inches deep) or 54-well heating blocks (22 1/2 inches wide by 16 inches high by 14 1/2 inches deep).

HotBlock TKN can also be used for total phosphorus digestion and TKP (total Kjeldahl phosphorus) analysis. 800/343-5319; www.envexp.com.