External loops are supplied with unattached fittings so the tube can be completely bottomed in the injector port before the ferrule is swaged on. This allows for different port depths. The depth of the tubing holes may vary slightly from port to port and from valve to valve. It is good practice to label loops so that they will be replaced in the same orientation and the same valve. PEEK loops do not require this precaution because the ferrule can slide and reposition itself along the tube when the fitting is reinserted into a port. Size designations are nominal. Sizes vary from nominal values usually less than 15%. Accuracy and precision in partial filling require that no more than half the loop volume be loaded. Precision in complete filling requires that at least two loop volumes be loaded.

PEEK Sample Loops
      Unlike metals, plastics are viscoelastic and therefore the yield strengths are not well defined. Many factors may affect the burst pressure of PEEK tubing.

Stainless Steel and Titanium Sample Loops
      Metal sample loops are supplied with unswaged fittings so they can be completely bottomed in the injector port before the ferrule is swaged on. Size designations of the metal loops are nominal. Actual volumes can differ due to the tolerances of the tubing. Precise volumes may be injected by the “partial-filling” method if you are using a dual-mode injector.

Note: Loops for the 7725 and 7125 injectors are NOT interchangeable.