By Donal O’Sullivan, BSc. Reviewed by Michael Anderson, MBA.

Good chromatography consumables stock control means knowing what your laboratory uses, how quickly it is consumed, how long replenishment normally takes and when a repeat order needs to be placed. There is no universal reorder point or minimum stock quantity that suits every laboratory. Appropriate levels depend on factors such as consumption, demand variability, pack size, lead time, workflow criticality and whether a technically approved alternative is available. For laboratory managers, the objective is not to hold as much stock as possible. It is to maintain enough control over recurring consumables to reduce avoidable urgent ordering while preserving the technical requirements of each workflow.

 

Key Takeaways

• Base stock controls on actual laboratory demand. Historical usage is useful, but upcoming projects, batch schedules and changes in workload also matter.
• Use defined reorder triggers rather than memory. A trigger might be a quantity, number of unopened packs, review date or known future requirement.
• Consider lead time and pack size together with consumption. An item used slowly may still require early ordering if replenishment is difficult or the purchase unit is large.
• Apply stronger controls to workflow-critical items. Not every chromatography consumable needs the same stock buffer or review frequency.
• Approved alternatives can reduce supply vulnerability, but only where they have already been accepted for the intended use. Stock pressure does not establish technical equivalence.
• Review stock-control assumptions when usage or supply conditions change. A reorder point that worked six months ago may no longer suit the laboratory.

Why Chromatography Consumables Need Active Stock Control

Chromatography laboratories depend on many comparatively small products to keep established workflows operating.

These can include:

• autosampler vials, caps, septa and inserts;
• syringe filters and syringes;
• GC liners, ferrules, septa and microsyringes;
• HPLC and UHPLC columns;
• guard columns and cartridges;
• gas filters and traps;
• tubing, fittings and other recurring chromatography accessories.

For a broader overview of these product families, see The Complete Guide to Chromatography Consumables for UK Laboratories.

The operational difficulty is that these products do not all behave like stock items in the same way.

One consumable may be used every day. Another may be replaced only periodically but become critical when required. Some arrive quickly in standard pack sizes, while others may have longer or less predictable replenishment times.

This means that stock control should be based on the behaviour and importance of the individual requirement rather than a single rule applied across the chromatography laboratory.

Standardisation and Stock Control Are Different Decisions

Before a laboratory decides when to reorder, it should already understand what it is prepared to reorder.

That distinction matters.

Standardisation establishes the approved product, specification or permitted alternative for a workflow.

Stock control establishes how the laboratory monitors that requirement and triggers replenishment.

A stock-control system should therefore work from clearly defined product records rather than trying to solve technical selection at the point when stock is already low.

If the approved requirement is unclear, the priority is to resolve that technical or operational uncertainty before using quantity alone as a purchasing trigger.

This separation also helps prevent an urgent stock shortage from becoming an uncontrolled product-substitution decision.

Which Consumables Should Be Stock-Controlled?

The most useful starting point is to identify recurring chromatography products whose absence would interrupt routine work or create avoidable purchasing pressure.

Not every product needs the same level of control.

A practical classification is:

Stock-control priority	Typical characteristics	Appropriate approach
High	Frequently used, workflow-critical, difficult to substitute or longer to replenish	Monitor closely and define an explicit reorder trigger
Medium	Regular use, predictable consumption or an approved alternative exists	Periodic review with a defined replenishment point
Lower	Occasional use, low operational consequence or readily replenished	Simpler review may be sufficient

The classification should reflect the laboratory's actual workflow rather than the price of the item alone.

A low-cost vial, ferrule or filter can still be operationally important if its absence stops a routine method.

Conversely, keeping large quantities of every possible chromatography consumable may increase stock complexity and create unnecessary inventory.

Start With Usage, Not an Arbitrary Minimum Quantity

A useful stock-control decision starts with consumption.

For each recurring item, ask:

• How much is normally used over a representative period?
• Is usage reasonably stable or highly variable?
• Does one method, instrument or team account for most consumption?
• Are there predictable peaks in demand?
• Is additional work already scheduled?
• Has usage recently increased or decreased?

Historical purchasing data can help, but purchasing history and actual consumption are not always the same thing.

For example, a laboratory may have placed a large order because of a temporary project, bought several packs to obtain a convenient purchase quantity, or carried surplus stock forward from an earlier period.

The goal is therefore to understand the pattern of demand, not simply repeat the previous order automatically.

Include Lead Time in the Reorder Decision

Consumption tells you how quickly stock is being used. Lead time affects how early the replacement order needs to be placed.

A laboratory using one pack every month may have very different requirements depending on whether replenishment normally takes a few days or several weeks.

Useful questions include:

• How long does replenishment normally take?
• Has the lead time been stable?
• Does the supplier need to source the item specially?
• Is the product routinely available or intermittently constrained?
• Does the laboratory need to allow additional time for internal purchasing or receiving processes?

Lead time should be treated as an input rather than a guarantee.

Supplier availability can change, so a stock-control system should be reviewed when replenishment conditions materially change.

Pack Size Matters

Reorder decisions also need to reflect how the product is actually supplied.

If a vial type is purchased in packs of 100 but normal demand is 30 per month, the stock-control process should be based on the pack configuration rather than an abstract single-unit quantity.

Similarly, if a consumable is sold only in a larger pack, placing the order too early can create unnecessary surplus.

Useful stock records therefore distinguish between:

• individual units;
• opened packs;
• unopened packs;
• normal purchase quantity.

For many laboratories, unopened packs can be a particularly practical operational measure because they are easy to count during routine stock checks. However, physical stock counts should distinguish usable stock from quantities that are damaged, expired, quarantined, reserved for specific work or otherwise unavailable. Only stock that can actually be used for the intended workflow should be counted as available when assessing replenishment needs.

How to Set a Practical Reorder Trigger

A reorder trigger is the point at which the laboratory starts the replenishment process.

It does not have to be a complex mathematical calculation.

A useful trigger reflects enough of the following factors to suit the laboratory:

Stock-control input	Question to ask	Operational implication
Usage	How quickly is the item normally consumed?	Helps establish how long remaining stock may last
Demand variability	Does usage fluctuate significantly?	Variable demand may require more margin
Lead time	How long does replenishment normally take?	Longer replenishment may require an earlier trigger
Workflow criticality	What happens if the item is unavailable?	Critical items usually need tighter control
Pack size	How is the item purchased?	The trigger should reflect real purchasing units
Approved alternative	Is another technically approved option available?	May reduce exposure to a single supply route
Upcoming work	Is known demand about to increase?	Future workload may override historical averages

A laboratory might therefore decide to reorder when:

• stock reaches a defined quantity;
• the final two unopened packs are reached;
• stock falls below expected usage during the normal replenishment period;
• a scheduled project creates additional known demand;
• a supplier advises that lead time is increasing.

The correct trigger is the one that reflects the laboratory's actual operating conditions. The frequency of stock checks also needs to support that trigger. For example, a weekly stock review may be insufficient for a rapidly consumed item if stock could fall from above the reorder point to an inadequate level before the next check. Review frequency and reorder triggers should therefore be considered together, particularly for high-priority consumables.

Minimum Stock Is a Control, Not a Universal Number

A minimum stock level can be useful, but the term can be misleading if it is treated as a fixed quantity that works indefinitely.

The appropriate minimum depends on the product and workflow.

A laboratory should consider:

1. normal usage;
2. variability in usage;
3. normal replenishment time;
4. pack size;
5. workflow criticality;
6. known upcoming demand;
7. availability of an approved alternative.

A chromatography vial used daily across several instruments may justify a different buffer from a specialist column required occasionally for one method.

The same is true even within a single product family.

The purpose of minimum stock is to create a practical signal that replenishment should begin before the laboratory reaches an avoidable shortage.

When deciding whether another order is needed, laboratories should also consider quantities already on order and their expected delivery dates. Stock physically available today is not the same as stock expected to become available during the replenishment period. An outstanding order may remove the need for another purchase, but it should not be treated as available stock until received and accepted for use. Where delivery is uncertain or insufficient to cover expected demand, further replenishment action may still be necessary.

Approved Alternatives Can Reduce Supply Risk

An approved alternative can be useful when the normal product is temporarily unavailable.

However, an alternative should be treated as part of the stock-control process only where its suitability has already been assessed for the intended workflow.

A similar description, dimension or nominal specification does not by itself establish technical equivalence.

The stock record should therefore distinguish between:

• primary approved product;
• approved alternative for defined use;
• potential alternative requiring assessment.

The third category should not be treated as available stock simply because procurement can obtain it quickly.

This distinction is especially important when the consumable interacts directly with the analytical method, instrument or sample.

Stock Control for GC Consumables

GC consumables provide a useful example of why general stock control and technical replacement planning should remain separate.

A laboratory may need to maintain stocks of liners, ferrules, septa, syringes, gas filters or columns, but the decision about when the laboratory should hold or reorder stock is not necessarily the same as the technical decision about when a component should be replaced.

Laboratories needing detailed GC-specific replacement guidance should use the dedicated guide to GC consumables replacement planning for busy UK laboratories.

The same principle applies across chromatography: the stock-control system should support the technical workflow rather than redefine it.

Build a Practical Repeat-Order List

A repeat-order list does not need to become a complex inventory-management system.

For many laboratories, a controlled table can provide enough visibility to make recurring purchasing more consistent.

Useful fields may include:

Field	Purpose
Consumable	Identifies the recurring requirement
Approved product reference	Reduces ambiguity during repeat ordering
Purchase unit / pack size	Shows how the item is actually ordered
Typical usage	Provides context for replenishment
Reorder trigger	Defines when action should begin
Current or review quantity	Shows the stock position at the review point
Lead-time information	Supports ordering timing
Approved alternative status	Indicates whether a pre-assessed alternative exists
Owner	Identifies who reviews or initiates the repeat order

The list should contain enough information to support replenishment without attempting to reproduce every technical purchasing specification. It should also make clear who is responsible for checking whether an order has already been placed, confirming its expected delivery and following up when replenishment is delayed. This helps prevent duplicate orders and ensures that reaching a reorder trigger leads to an appropriate purchasing action rather than simply being recorded.

Common Stock-Control Mistakes

Waiting until the last pack is opened

This leaves little margin for supplier delay, internal purchasing time or unexpected demand.

Using the same minimum quantity for every item

Different consumables have different usage patterns, lead times and operational consequences.

Treating last year's demand as permanent

Workload changes. Stock controls should change with it.

Ignoring pack size

A reorder quantity should reflect how the item is actually supplied.

Treating an available substitute as an approved substitute

Availability is a commercial fact. Technical suitability is a separate decision.

Holding excess stock simply to avoid shortages

More stock is not automatically better control. Excess inventory can create complexity, tie up purchasing budget and leave quantities unused when requirements change.

Ignoring shelf life and storage requirements

Where chromatography consumables have manufacturer-specified expiry dates, storage conditions or limits after opening, these requirements should be considered when deciding how much stock to hold. Stock should be stored under the specified conditions, checked for continued suitability and rotated so that earlier-expiring usable stock is selected first. Large repeat orders can create avoidable waste if products cannot be used within their applicable shelf life.

Relying on one person's memory

Stock control becomes more robust when the reorder trigger and responsibility are visible to the wider team.

A Simple Seven-Step Stock-Control Workflow

1. Identify recurring chromatography consumables

Start with products repeatedly required for established workflows.

2. Confirm the approved requirement

Make sure the laboratory knows which product or specification can be reordered routinely.

3. Review actual usage

Use representative consumption data and consider known changes in future demand.

4. Check replenishment conditions

Record the normal purchase unit and consider realistic lead time.

5. Assign stock-control priority

Give tighter control to items whose absence would have the greatest operational impact.

6. Define the reorder trigger

Choose a practical trigger based on usage, lead time, pack size, criticality and any approved alternative.

7. Review the control when conditions change

Update the trigger when usage, projects, product availability or supplier lead times change materially.

This approach does not eliminate supply uncertainty, but it replaces reactive purchasing with a more deliberate replenishment process.

When Should Stock Controls Be Reviewed?

A reorder point should not become permanent simply because it worked once.

Useful review triggers include:

• sustained changes in consumption;
• new or completed projects;
• additional instruments or workflows;
• supplier lead-time changes;
• product discontinuation;
• repeated urgent orders;
• persistent excess stock;
• introduction of an approved alternative;
• changes to pack size or purchase configuration.

Routine review keeps stock-control settings aligned with the laboratory rather than with historical assumptions.

Frequently Asked Questions

How should laboratories decide when to reorder chromatography consumables?

Laboratories should set reorder triggers using actual consumption, expected demand, replenishment time, pack size and the operational importance of the consumable.

The trigger can be a quantity, number of unopened packs or scheduled review point. It should provide enough time to replenish the approved item before normal stock is exhausted without encouraging unnecessary overstocking.

What factors should be considered when setting minimum stock levels?

Minimum stock should reflect usage, demand variability, lead time, pack size, workflow criticality, known future demand and the availability of approved alternatives.

Quantities already on order and their expected delivery dates should also be considered when deciding whether further replenishment is required. Undelivered products should not be treated as available stock until they have been received and accepted for use.

Should every chromatography consumable have the same reorder point?

No. Reorder points should reflect the usage and supply characteristics of each recurring consumable.

Frequently used or workflow-critical items may require tighter controls, while occasional or easily replenished products may need simpler monitoring. Applying one quantity or review frequency to every consumable can result in either unnecessary surplus or inadequate stock.

How should approved alternatives be handled in a stock-control system?

An approved alternative should be recorded separately from the primary product and linked to the workflow for which its use has been accepted.

Stock availability alone should not determine whether another product is suitable. A potential alternative that has not completed the laboratory's required technical assessment should not be treated as an approved substitute simply because it can be purchased quickly.

How often should chromatography-consumables stock levels be reviewed?

Stock should be reviewed often enough for the laboratory to identify its reorder trigger before normal consumption reduces stock to an inadequate level.

The appropriate frequency depends on usage rate, variability, lead time and operational criticality. Review frequency and reorder triggers should therefore be considered together, with additional review when workload, supplier lead times, product availability or other relevant conditions change.

What information should a chromatography consumables repeat-order list contain?

A repeat-order list should identify the approved product, purchase unit, typical usage, reorder trigger and the person responsible for replenishment.

It should also make clear whether an order has already been placed, its expected delivery where known and who is responsible for following up delayed replenishment. Lead-time information and approved-alternative status can also be useful without replacing the technical records that determine product suitability.

Move From Reactive Ordering to Controlled Replenishment

Effective chromatography consumables stock control is not about maximising inventory.

It is about knowing which recurring items matter, understanding how they are used, recognising when replenishment needs to begin and maintaining clear controls around approved alternatives.

A simple repeat-order system can make routine purchasing more predictable while keeping technical decisions where they belong.

If your laboratory already has defined recurring chromatography requirements, you can set up a repeat-order discussion with LabFriend UK.

Read More

• The Complete Guide to Chromatography Consumables for UK Laboratories
• GC Consumables Replacement Planning for Busy UK Laboratories

Explore More

• Browse Chromatography Consumables
• Contact LabFriend UK About Recurring Consumables Requirements

 

 

Written by: Donal O’Sullivan, BSc, Co-Founder and Sales Director, LabFriend UK. Donal brings deep chemistry-led technical expertise across analytical chemistry, biochemistry, environmental monitoring, laboratory instrumentation, consumables and scientific product selection.

Reviewed by: Michael Anderson, MBA, Founder and Managing Director, LabFriend UK. Michael reviews LabFriend UK content for customer relevance, commercial accuracy, operational practicality and alignment with LabFriend UK’s laboratory supply model.