Mo. Rev. Stat. § 50.757: Purchasing agent, duties — bids rejected, when.

1. It shall be the duty of the county purchasing agent, if one is appointed, to purchase all supplies of whatever kind or nature necessary for the conduct of the business of the county in all its departments; and the county shall not be liable for any debts except upon the written order of such purchasing agent, who shall make purchases only from those offering the lowest price, quality considered, and the purchasing agent is not authorized to purchase supplies of higher quality or price than is reasonably required for the purpose to which they are to be applied.

2. The purchasing agent may reject any or all bids for the sale of articles and supplies for the use of the county.