Site Buyer and Master Planner

The Opportunity:

Avantor is seeking a Site Buyer and Master Planner for our St. Louis site. This role is fully onsite, Monday–Friday, 8 a.m.–5 p.m., with a bit of flexibility to connect smoothly with teams in other time zones.

The Site Buyer and Master Planner owns site-level purchasing and integrated planning activities to deliver customer service, inventory, and cost objectives. This role manages direct and indirect materials procurement, leads the monthly site S&OP cycle and weekly S&OE process, and represents the site in global supply chain planning forums.

QUALIFICATIONS (Education/Training, Experience and Certifications)

• Bachelor’s degree in Supply Chain, Logistics, Operations Management, Engineering, or related field.

• 3+ years of experience in procurement and supply chain planning in a manufacturing environment (chemical/process manufacturing preferred).

• Demonstrated experience leading cross-functional planning forums (S&OP/S&OE) and managing supplier/service performance.

• APICS/ASCM certification preferred (CPIM, CSCP) or equivalent.

KNOWLEDGE SKILLS AND ABILITIES (Those necessary to perform the job competently)

• Strong practical knowledge of procurement and end-to-end supply chain planning, including make-to-order environments and constraint-based execution.

• Working knowledge of S&OP/S&OE best practices, backlog management, and order prioritization governance.

• Strong analytical skills; proficient in Excel and ERP systems (Microsoft Dynamics GP and SAP preferred); able to build clear narratives from data.

• Effective meeting leadership and facilitation skills; ability to drive decisions, manage actions, and communicate clearly across functions.

• Strong stakeholder management and presentation skills; comfortable representing the site in regional/global forums.

• Ability to work under pressure, manage multiple priorities, and deliver results with a high level of accuracy and accountability.

Major Job Duties & Responsibilities

• Procurement & Purchasing Operations

  • Determine raw material order quantities and timing by analyzing on-hand, on-order, lead times, and historical demand/consumption.

  • Generate and manage purchase orders/agreements: review requisitions, issue POs, run PO reports, confirm deliveries, expedite as needed, and manage open PO exceptions/backorders.

  • Communicate purchase requirements and documentation needs (e.g., CoA/CoC) to suppliers; ensure alignment to schedule requirements.

  • Manage sourcing, planning, and purchasing of indirect materials and PPE required for manufacturing, maintenance, QC/QA, and housekeeping.

  • Resolve goods-inwards/receiving issues tied to POs, deliveries, and inventory discrepancies; coordinate with Receiving/Warehouse and suppliers.

  • Manage pricing alignment per governance and coordinate discrepancies with Finance/Commercial.

  • Drive supplier nonconformance follow-up: initiate complaints for out-of-spec materials and coordinate returns/refunds with suppliers, Shipping & Receiving, and Accounts Payable.

  • Participate in regular supplier operational reviews; address service issues and drive corrective actions, including identifying alternate sources when appropriate.

  • Coordinate inbound/outbound transport needs related to materials, including import/export shipments and freight forwarder arrangements (as applicable).

  • Liaise with global Sales and Customer Service to communicate open PO status, constraints, and recovery actions that may impact customer commitments.

• Integrated Planning (S&OE, S&OP)

  • Lead the monthly site S&OP process: consolidate demand (direct and interplant), review supply/capacity constraints, develop scenarios, and drive cross-functional decisions and actions.

  • Lead weekly site S&OE: manage backlog priorities, constraint resolution, recovery plans, and escalation decisions for the 0–4 week horizon.

  • Represent the site in global S&OP/S&OE forums: submit required data on time, present site status/constraints, and communicate risks and mitigation plans.

  • Partner with global demand planning and network plants to align demand forecasts (direct and interplant); reconcile forecast vs. orders and highlight deviations.

  • Collaborate in daily/weekly cross-functional site management forums to ensure stakeholders are aligned to priorities and prepared to support commitments.

  • Support inventory planning with Finance: maintain invent