Exhibit 10.42

Nicholas M. Mitchell
Via E-mail
September22, 2026
Dear Nick,
Re: LETTER OF APPOINTMENT
We have pleasure in confirming the terms and conditions under you will continue to be employed in the position of Chief Operating Officer at Renergen Limited (or any successor corporation thereto) (the Company). This LOA and the Conditions (each, as defined below) shall supersede and replace, effective as of the date hereof (Effective Date), any and all prior or contemporaneous agreements between the parties with regard to the subject matter contained herein.
Background:
Renergen is a wholly-owned subsidiary of ASP Isotopes Inc., a Delaware corporation (“ASPI”), whose principal asset is its 94.5% equity ownership in Tetra4 Proprietary Limited (“Tetra4”). Tetra4 holds an onshore petroleum production right and engages in the production and liquefaction of natural gas and the exploration and development of helium resources at the Virginia Gas Plant located in Free State Province, South Africa. ASPI has formed Noble Africa LLC, a Delaware limited liability company and wholly-owned subsidiary of the Company (“Noble Africa”), for the purpose of serving as an intermediate holding company for the Company’s shares in Renergen.
On June 25, 2026, ASPI entered into an Agreement and Plan of Merger (the “Merger Agreement”), by and among ENDRA Life Sciences Inc., a Delaware corporation (“Pubco”), Noble Africa, Renergen and Kruger Merger Sub LLC, a Delaware limited liability company and a direct, wholly-owned subsidiary of ENDRA (“Merger Sub”), pursuant to which Merger Sub will merge with and into Noble Africa (the “Merger”), with Noble Africa surviving the Merger as a direct wholly-owned subsidiary of Pubco. Prior to the effective time of the Merger, ASPI will contribute all of its equity interest in Renergen to Noble Africa in exchange for 55,500,000 of Noble Africa’s Class B Units. Following the Merger, Pubco is expected to be renamed “4K Resources Inc.” and its common stock is expected to be listed on Nasdaq. Consummation of the Merger is subject to certain closing conditions, including the approval by the shareholders of ENDRA, receipt of a written consent of the U.S. Internal Development Finance Corporation and other matters.
You understand that a new employment agreement with Pubco (or a subsidiary of Pubco) may be prepared in connection with the closing of the Merger.