Protein precipitation is another simple pretreatment technique. The protein content of human body fluids and tissues is considerable, from about 6% by weight in plasma to greater than 50% by weight in liver and other organs. Numerous reagents have been developed to precipitate protein; two that are commonly used in drug analysis are trichloroacetic acid (10-15% in water) and tungstic acid (10% sodium tungstate in water and used in conjunction with 3n sulfuric acid). Once proteins have been precipitated, separation of aqueous and solid protein must occur by filtration or centrifugation.
The tale began in 1939, when the wealthy Jewish industrialist and art collector David Friedmann was forced to flee and the Nazis pillaged the vast collection he left behind. Many of the works ended up in the hands of Hildebrand Gurlitt, a notorious German art dealer who traded in what the Nazis called “degenerate art” — works deemed inferior because they were un-German, Jewish or Communist or, as is the case with impressionist and other modernist works, did not employ traditionally realistic forms — but were pleased to sell to help fund their war machine.