Abstract: A leak-tight noncontaminative joint connecting a section of titanium, tantalum, zirconium or stainless steel tubing with second section of titanium, tantalum, zirconium or stainless steel tubing of a larger diameter is formed by placing a compressible O-ring, a slidable, nontitanium, nontantalum, nonzirconium or nonstainless steel ferrule and a fixed, nontitanium, nontantalum, nonzirconium or nonstainless steel mechanical stop around the outer surface of the smaller tubing and inserting the smaller tubing into the larger tubing so as to compress the O-ring between the two sections, until the ferrule, which conformably engages the inner surface of the larger tubing, is driven firmly against the mechanical stop. In this arrangement the fluid being transported within the titanium, tantalum, zirconium or stainless steel tubings is unable to pass by the O-ring and thus does not contact either the nontitanium, nontantalum, nonzirconium or nonstainless steel ferrule or stop.