HPLC, capsaicinoids concentrations and SHU

High Pressure Liquid Chromatography (HPLC) is the current method of choice for measuring capsaicinoids concentrations in chile peppers. The result is measured in parts per million (PPM). To convert from PPM to Scoville Heat Units (SHU) multiply the PPM by 15. This conversion is a rough approximation since different capsaicinoids have different effective SHU effects.  For further reasons as to why this would be a rough approximation see the page on Scoville Heat Units.

HPLC is now often given as standing for High Performance Liquid Chromatography - an obvious PR move since the original name was an exact technical description. 

In general chromatography is a method of separating complex chemical mixtures into their constituent chemical compounds.  The original method was to fill a tube with fine clays and allow compounds dissolved in a solvent to percolate through.  Travel time through the column would be different for each compound depending on various factors including the compound's solubility in the solute and its chemical weight.  The above method was called: open column chromatography.  Other competing methods of the time (1970s) were:

HPLC development started in the mid 1970s and has been refined and developed ever since and has eliminated all of the other liquid phase methods.  Basically a closed pressurized tube was substituted for the open tube and many other refinements were made.  Further, cheap computing power has been a huge boost to its adoption.