Union Trust Co. of Maryland acted as manager and agent of syndication last week for a $9 million Eurodollar loan agreement with Salinas y Rocha, S.A., a Mexican retail chain.

The bank also participated as a lender along with First Union National Bank, North Carolina; Bank of Hawaii; Midlantic National Bank, New Jersey; and Banco Di Roma, Chicago. Union Trust drafted the loan, prepared an information memorandum and sought out other lenders.

As agent, Union Trust will maintain contact between the borrower and lenders during the life of the loan, administer the loan and provide financial information. This is Union Trust's first entry into the syndicated lending market.

On Tuesday, Interamericana de Alumina C.A. will sign at $60 million loan agreement with the Export-Import Bank. The loan will go toward completion of an alumina producing plant in Ciudad Guayana, Venezuela, and will be used to purchase equipment and services from the United States. The plant, located on the Orinoco River, will make use of existing and developing power sources in the multistage processing of bauxite into alumina.

Recent agreements by international lending and financial institutions based in Washington include: World Bank

The International Development Association, the World Bank's affiliate for concessionary lending, has granted a credit of 8.7 million in special drawing rights ($11.5 million) to the government of Madagascar for an agricultural credit project. The project will provide seasonal, medium-term and long-term credit for the maintenance, regeneration and establishment of coffee, vanilla, sugar cane, cocoa and other plantations.

A credit of 13.3 million in special drawing rights ($17.5 million) to the government of Guinea for a livestock development project. The project is designed to increase the productivity of the country's cattle herd, increase national meat and milk production, improve nutrition and raise the standard of living of cattle-herding families. Export-Import Bank

Eximbank has approved a multi-project arrangement for the Development Bank of the Philippines to support up to $100 million in U.S. exports for Philippine projects during the next 12 months. The arrangement may be used to support U.S. sales to either public or private-sector Philippine purchasers for projects other than aircraft or power.

Financing totaling $111.4 million to Comision Federal de Electricidad, the Mexican government agency that supplies most of Mexico's electric power, for the purchase of 14 gas turbine electric generators from Westinghouse, General Electric, United Technologies and Brown Boveri, for a total U.S. cost of $131 million. Inter-American Development Bank

A $100,000 loan to help the Behrhorst Clinic Foundation stimulate integrated community development and build rural sanitation systems in Guatemala. The project will benefit an estimated 10,000 persons in 27 Indian communities in the Guatemalan altiplano who derive their livelihood mainly from subsistence farming.

An additional $200,000 in nonreimbursable technical cooperation to promote mutual aid and partially finance technical cooperation activities among the Bank's Latin American member countries.