Nearly two centuries alchemists did try to make Gold. Today  anybody knows that this was impossible with their methods.
 
Making process probes looks sometimes like alchemy, because  since rather  2 decades dozen of companies and engineers did create many probe designs using metals & alloys,  O-rings, seals, quartz glass, Sapphire and sometimes special solders.
Some things were reinvented again and again and much money was invested by advertising "old things", but

durability and lifetime of wetted partes are still critical issues for any optic equipment in process control.

 
There is a serious design and technology problem between the indispensable elastic force for sealing (without will be a leakage), the different thermal expansion coefficients of the parts made by different   materials and the optic-mechanical stability of  the optic probe setup, which is required by todays spectroscopic methods!
 
A

monolithic probe made of alumiumoxide (Sapphire and alumina ceramic)

did solve the problem in 1994.