The Environmental Protection Agency's Great Lakes National Program Office intends to award a sole source purchase order to Sea-Bird Electronics, Inc. for specialized instruments, including a micro-TSG, submersible ultraviolet nitrate analyzer, and ACS spectrophotometer, for continuous surface water sampling on the research vessel Lake Guardian. Sea-Bird is the only commercial supplier of the submersible ultraviolet nitrate analyzer, and the other instruments are the only options compatible with the existing flow-through system aboard the vessel. Interested parties must provide evidence of their capability to fulfill the requirement by July 28, 2026. Responses must be submitted in writing to the Contract Officer. No budget amount or performance location beyond the Great Lakes is specified.