Understanding Lab Numbers: Units, Detection Limits and Pass Criteria

01

Concentration is an amount relative to the sample

Milligrams per kilogram, written mg/kg, describes substance mass relative to sample mass. It is not the total amount in your jar.

These unit relationships help you compare mass concentrations:

The words by weight matter. Do not apply this ppm equivalence to every measurement carrying that abbreviation without checking its basis.

Why some conversions leave the number unchanged

Converting both parts of mg/kg by the same factor gives µg/g with the same numerical value. Changing only milligrams to micrograms while retaining kilograms multiplies the number by 1,000.

That is why 0.08 mg/kg equals 80 µg/kg, rather than 0.08 µg/kg.

02

Detection and reliable measurement are different

A method can distinguish a substance from background without measuring a tiny amount well enough to report a precise quantity.

• LOD — limit of detection: concerns distinguishing the substance from background.
• LOQ — limit of quantification: concerns measuring it with suitable performance.
• ND — not detected: usually indicates no detection, but still depends on a detection limit.
• Reporting limit: follows the laboratory's stated reporting rules, which may differ from these other thresholds.

Use the definitions on the actual report. If a row contains only ND, request the definition and limit rather than assigning a numerical meaning yourself.

03

Read a less-than result as a boundary

The following values are hypothetical notation examples. They are not measurements from products or shilajit safety limits.

A conversion preserves that boundary: <0.02 mg/kg = <20 µg/kg. It does not create an exact measurement of 20 µg/kg.

A tighter boundary does not prove a cleaner sample

Imagine report A says <0.01 mg/kg and report B says <0.05 mg/kg.

A could contain 0.009 mg/kg while B contains 0.001 mg/kg. Both reports would still be correct. A has the tighter reported boundary, but neither result provides the exact amounts required to rank the samples.

Do not award the lower measurement to the report with the smaller less-than number.

04

A reporting limit is not a safety requirement

One number describes the measurement and reporting process. Another may define the requirement against which the result is assessed. They can sit in neighbouring columns without doing the same job.

In a fictional case, <0.10 cannot establish compliance with a requirement of 0.05 in the same units. The reported range is too broad to settle that question. These numbers illustrate the logic; they are not safety thresholds for shilajit.

For any pass decision, find the actual requirement and the notes supporting it. The contaminant-testing guide explains why product category, substance and method also matter.

05

Calculate the amount in a portion carefully

Multiply concentration by the mass of the material, using matching units.

An illustrative calculation is:

2 µg/g × 0.25 g = 0.5 µg

The grams cancel, leaving the amount of the measured substance. This describes that portion only if the concentration applies to the same material. It is neither a serving recommendation nor an assessment of safe exposure.

Keep “dry basis” and “as received” labels attached to percentage results, too. They use different denominators. The fulvic acid guide works through the resulting differences without changing the actual amount of the measured component.