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 inventory outlooks and working-capital plans consistent with the approved S&OP plan; identify excess/obsolete risks and actions.
    
  • Run the quarterly PFEP (Plan for Every Part) process to set and maintain the site stocking strategy for direct materials and packaging (criticality, lead times, MOQ/cadence, shelf-life/storage, and ordering parameters such as min/max and reorder points).
    
  • Partner with Operations, Quality, Warehouse/Logistics, and Finance to review PFEP outputs, implement approved parameter changes, maintain master data, and maintain documentation and an action log.
    
  • Support NPIs by establishing sourcing readiness, planning assumptions, and lead times and communicating impacts to stakeholders.
    

• Process, Metrics & Continuous Improvement
  • Check and resolve ongoing issues in processes or systems using standard work expectations; implement tactical and operational goals set by the manager.
    
  • Implement process changes, operational metrics, and standards within the role's scope; deliver agreed metrics using Avantor Business Systems (ABS) tools.
    
  • Collaborate with Quality Assurance to convert or generate procedures into the current standard format (as assigned).
    

Disclaimer:
The above statements are intended to describe the general nature and level of work being performed by employees assigned to this classification. They are not intended to be construed as an exhaustive list of all responsibilities, duties and skills required of employees assigned to this position. Avantor is proud to be an equal opportunity employer.

Why Avantor?

Dare to go further in your career. Join our global team of 14,000+ associates whose passion for discovery and determination to overcome challenges relentlessly advances life-changing science.


The work we do changes people's lives for the better. It brings new patient treatments and therapies to market, giving a cancer survivor the chance to walk his daughter down the aisle. It enables medical devices that help a little boy hear his mom's voice for the first time. Outcomes such as these create unlimited opportunities for you to contribute your talents, learn new skills and grow your career at Avantor.


We are committed to helping you on this journey through our diverse, equitable and inclusive culture which includes learning experiences to support your career growth and success. At Avantor, dare to go further and see how the impact of your contributions set science in motion to create a better world. Apply today!

EEO Statement:

We are an Equal Employment/Affirmative Action employer and VEVRAA Federal Contractor. We do not discriminate in hiring on the basis of sex, gender identity, sexual orientation, race, color, religious creed, national origin, physical or mental disability, protected Veteran status, or any other characteristic protected by federal, state/province, or local law.

If you need a reasonable accommodation for any part of the employment process, please contact us by email at View email address on click.appcast.io and let us know the nature of your request and your contact information. Requests for accommodation will be considered on a case-by-case basis. Please note that only inquiries concerning a request for reasonable accommodation will be responded to from this email address.

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