Choosing environmental and food laboratories by the method and the sampling: why a soil testing lab result, and any soil laboratory testing or soil testing labs comparison, is decided by the sampling plan before the laboratory receives anything, what a food testing lab, food testing labs, food testing laboratories, a food testing laboratory, laboratory food testing, food lab testing, food safety testing labs and the food testing equipment behind them each have to state about the method and the limit, where nutritional analysis testing, a nutritional analysis lab and nutritional analysis labs generally differ from a pesticide testing laboratory in matrix and in accreditation, what endotoxin testing laboratories and forensic testing add in chain of custody and what forensic lab equipment and environmental testing equipment are bought for in house, why laboratory safety equipment belongs in the same procurement conversation, why indoor air quality testing los angeles and similar locality searches are really asking about accredited local capacity, and what a report has to contain before a decision rests on it

Getting a usable result

1. Design the sampling plan first. Number of increments, location, depth or point of collection, and how they are composited. For heterogeneous material this dominates the uncertainty and it is decided before anyone contacts a laboratory.
2. Preserve and transport to the method's requirement. Container type, temperature, preservative and holding time are specified by the method. Exceeding a holding time invalidates the result regardless of how well the analysis was run.
3. Name the method and check the scope. Different standards give different numbers for the same property. State the method and confirm it appears on the laboratory's published accreditation schedule.
4. Ask about matrix recovery. Detection limits assume a recovery from a matrix. Ask for recovery data on a matrix like yours rather than accepting a figure generated on a clean one.
5. Establish chain of custody where it matters. For forensic, regulatory and dispute related work the custody record is part of the evidence. Agree the documentation before the first sample is taken.
6. Specify the report contents. Method, sample description and condition on receipt, holding times, result with uncertainty, any deviations and a signature. Agree it in advance rather than discovering an omission when it is needed.

Sampling dominates the uncertainty

For heterogeneous matrices, the variation between samples taken metres apart routinely exceeds the analytical uncertainty by a large factor. Improving the analysis while sampling one point does not improve the answer.

Spend the effort on increments and compositing. It is cheaper than a better method and it changes the result more.

Accreditation is method by method

A laboratory is accredited for named methods on named matrices, published in a schedule. Reading it takes minutes and prevents a report that cannot be used for its purpose.

Where your method is outside the scope, the work may still be good and the report will say something different. Know which you are buying before the samples go.

Common questions

Why do results vary so much between samples?

Heterogeneity, almost always. Soil, food and environmental matrices vary over short distances, and a single grab sample can differ substantially from the average. A proper increment plan is the remedy.

Does holding time really invalidate a result?

For many analytes, yes, because they degrade or transform. Methods specify holding times for that reason, and exceeding one makes the number unusable for a regulatory purpose.

What should I check about a local laboratory?

That its accreditation schedule includes your method and matrix, what it subcontracts, and its turnaround to a signed report. Proximity matters mainly because it shortens holding time exposure.

Browse by service class

• Compare Gene synthesis on advertised prices