| OH content | Measured hydroxyl (OH) content in ppm; test method; sample identification; report date. | Compare results only for the specified material grade and test method. Request a lot-specific measurement, commonly determined using infrared spectroscopy. | OH content varies by silica type and production route. There is no single universal OH limit for all tubing applications. |
| UV transmission | Transmission (%) at the application wavelength; tube wall thickness; measurement setup; material grade. | Compare measurements at the same wavelength and equivalent optical path length. For UV applications, specify the intended wavelength, such as 185 nm, 193 nm, or 254 nm, where relevant. | Transmission depends on wavelength, thickness, surface condition, and measurement geometry. A percentage without test conditions is not directly comparable. |
| Bubbles and inclusions | Inspection method; observed size and count; inspection area or length; applicable acceptance specification. | Ask for documented inspection results against the agreed drawing or specification. ISO 10110-3 provides a notation system for bubbles and inclusions in optical elements. | Acceptance depends on intended use and viewing or inspection conditions. Confirm how defects are counted and what tube region was inspected. |
| Traceability | Unique lot or batch number; material grade; production date; certificate of analysis; linked inspection and test records. | Check that the identifiers on the tubing, packaging, certificate, and test reports match, and that records can be retrieved for the delivered lot. | A general company certificate does not establish the properties of a specific shipment; request documentation tied to the actual lot. |
| Dimensions and tolerances | Outside diameter, inside diameter, wall thickness, length, straightness, and stated tolerances. | Compare measured values with the same drawing revision and tolerance definitions. Confirm the measurement method and sampling plan. | For tubing, wall thickness and concentricity can affect fit and optical path; evaluate them against the application requirements. |
| Surface and cleanliness | Surface condition; cleaning or packaging process; visible contamination inspection; handling and storage instructions. | Specify whether the inner surface, outer surface, or both must meet the requirement, and agree on inspection and packaging conditions. | Cleanliness requirements vary by use, especially for fluid-contact, vacuum, and optical applications. |
| Recommended comparison record: Use one row per supplier quotation and enter the actual measured value, test conditions, lot number, document reference, and pass/fail result against your own written specification. Do not rank suppliers using unmatched samples or undisclosed test conditions. |