Untested Analytes Must Stay Untested in the Conclusion

Overview

No — a negative result on a specific analytical panel cannot validly support claims that substances not listed on that panel are absent. If a report shows “not detected” or below-reporting-limit results only for named targets, you must limit conclusions to those exact targets and their defined detection thresholds. Broad statements such as “clean,” “pure,” or “contaminant-free” go beyond the evidence unless every possible contaminant was explicitly included and validated for the tested matrix.

Why this matters: analytical testing is target-driven. Labs run methods that detect particular analytes at specified limits under defined conditions. A negative finding speaks to those targets and the test method’s performance, not to unknown or unlisted substances .

How to map a panel result into a defensible conclusion

1) Read the panel list and report language exactly

2) Use exact target names in your conclusion

3) Avoid categorical words that imply universal absence

Panel-to-conclusion mapping exercise (example templates)

Why naming exact targets matters

What to look for in the lab documentation

A concise evidence-reading checklist

Method explanation and the required caveat

When you still want broader assurance

Bottom line: Translate reports into precise, target-named statements that mirror what was tested and at what limits. Anything beyond that—blanket declarations of purity or freedom from unlisted contaminants—rests on assumptions, not the panel’s evidence.

• Identify each named analyte or analyte class on the report (for example, “lead (Pb), cadmium (Cd), mercury (Hg)” or a list of specified pesticides).
• Note the reported limits: the report should state a reporting limit, limit of detection (LoD), or limit of quantification (LoQ) for each analyte. A “not detected” result means the substance was below that stated analytical limit, not necessarily zero concentration .
• When describing results, repeat the exact target names used by the laboratory. Say, for example, “lead (Pb) < X µg/g; cadmium (Cd) < Y µg/g,” rather than “heavy metals absent.” If the lab lists a class (e.g., “GC–MS screen for volatile organics”), use the same class label and, if provided, the library/target list that the method covers .
• Do not use words such as “clean,” “pure,” “contaminant-free,” or “safe” unless the laboratory expressly validated the method to demonstrate absence across the full range of conceivable contaminants for that specific sample type — and you have primary documentation. Most panels are limited in scope and cannot support universal claims .
• If the panel lists: “Lead (Pb), Cadmium (Cd), Mercury (Hg)” with reporting limits:
• Supported conclusion: “Lead (Pb) < [reporting limit]; Cadmium (Cd) < [reporting limit]; Mercury (Hg) < [reporting limit].”
• Not supported: “No heavy metals present” or “Contains no contaminants.”
• If the panel lists: “GC–MS targeted screen for pesticides A, B, C, …, Z”:
• Supported conclusion: “Pesticides A, B, C … Z were not detected above the stated reporting limits for this GC–MS targeted screen.” If the method provides a target list, name it verbatim .
• Not supported: “No pesticides present” unless the target list explicitly covers every pesticide of concern — which is rare.
• If the panel lists: “GC–MS/LC–MS screening for contamination” with no explicit target list:
• Supported conclusion: “The reported GC–MS/LC–MS screening did not detect the laboratory’s specified targets above reporting limits.” You must quote the report’s defined target list or state that the method used an internal target library.
• Not supported: “All contaminants were screened” or “All unknown substances would have been found.”
• Analytical sensitivity, selectivity, and matrix effects vary by analyte and by sample matrix. A method capable of detecting one metal at low ppb may not detect an organic contaminant at the same concentration. Naming the exact targets keeps the evidence and its limits transparent .
• Target list: a definitive list of analytes or compounds covered by the method.
• Reporting limits: LoD/LoQ or reporting limits for each analyte.
• Method description: a brief statement of the technique (e.g., GC–MS, LC–MS/MS, ICP-MS) and any qualifiers about matrix-specific limitations.
• Scope and disclaimers: statements that clarify what the test does not cover and any known blind spots .
• Does the report list each analyte by its exact name and provide reporting limits? If yes, you can state non-detections for those exact analytes.
• Does the lab provide or reference a target library or method validation for that matrix? If yes, cite it verbatim when summarizing.
• Does the conclusion you intend to make use broader language than what the panel and limits justify? If yes, narrow your wording to the exact named targets and limits.
• Explaining how a panel is built — target selection, instrumentation, reporting limits — helps readers judge what the results can and cannot support. This methodological description is provided only to clarify the evidentiary scope of a given test and not to imply accreditation, validation for every possible matrix, or suitability for any health or safety conclusion without separate, current primary evidence. A laboratory’s “not detected” applies to listed targets at listed limits and does not by itself demonstrate absence of untested substances .
• If a broader claim is important (for example, “no pesticides of any class”), you need a documented testing program that explicitly lists all relevant analytes and demonstrates validated limits appropriate to the sample matrix. Otherwise, the only defensible public statement is limited to the exact analyte names and reporting limits shown on the report .