Volatile reagents

For high-pressure plant, volatile reagents are preferred even for storage in case any chemical is inadvertently left in during subsequent operation. As with on-load protection, ammonia and hydrazine are used. With ammonia alone, a pH value of greater than about 10-5 is desirable, whilst with ammonia and hydrazine together, about 50 mg/kg of each, giving a pH value of about 10-0, is adequate. 

Vessels designed for microwave-assisted SPOS must fulfill several require-menfs because of fhe harsh conditions (i.e., high temperatures and pressures) usually associated with microwave heating. Open vessels are often impractical because of the possible loss of solvent and/or volatile reagents during the heating process. However, in cases where a volatile byproduct inhibits a reaction, their use may be superior over closed systems. A sealed vessel retains the solvents and reagents, but must be sturdily constructed to avoid the obvious safety implications due to the buildup of pressure. 

Another interface commonly used for connecting HPLC to a mass spectrometer is not a true in-line interface. It is a robotically controlled spotter plate system for collecting samples from the HPLC to be injected into the MALDI time-of-flight laser ionization mass spectrometer for analyzing proteins and large peptides. The effluent sample dropped in the plate well is mixed with an ionization matrix already present, solvent and volatile reagents are evaporated, and the plate is then placed into the injector target and blasted with a pulsed laser to volatilize and ionize sample into the atmosphere of the interface where it can be drawn into the mass spectrometer. 

It should be noted that dimethylsulphate and hydrazine are poisonous volatile reagents and should be stored and handled in a fume-hood. Disposal of dimethylsulphate into sodium hydroxide solution and hydrazine into 3M ferric chloride inactivates these compounds. 

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