Environmental Services Program fact sheet
Division of Environmental Quality Director: Kyra Moore

Chemists use complex instruments to analyze samples. Sometimes the substance of concern is not present in high enough concentrations for the instrument to “see” or detect. If a substance was not detected by the laboratory’s instrument, it may be reported in one of two ways. You may see a “less than” or left pointing arrow (<) followed by a number in the results column. Alternatively, there may be a value with no arrow followed by an “ND” in the Qualifier column to the right of the number. 

In each of these cases, the number in the Result column for that parameter/analyte is the Method Detection Limit (MDL) for that substance.  So, for example, if the substance Trichloroethene (TCE) on the sample analysis report has “1.0”  in the Results column, “ND” in the Qualifier column, and “ug/L” in the Units column, it means the lab instruments did not detect any TCE in this sample at or above 1.0 ug/L. The MDLs sometimes differ because the instruments vary in sensitivity to each substance.

If a substance was detected in the sample, you will see a number in the Results column without a “less than” arrow beside it, and without an “ND” in the Qualifier column. These numbers require careful interpretation. In order to determine whether the chemical is present at a concentration that may be of concern, the number should be compared to a specific screening benchmark. The department staff evaluating your results will conduct these comparisons and provide more information for any chemicals detected above these benchmarks. 

What are the different reasons why a sample was collected?

The sample event type field indicates the reason the sample was collected.

  • Monitoring – This is established to collect information from a site on a routine basis to make sure the site in compliance with Missouri and Federal Laws.
  • Inspection – This is a review of the facility to insure they are meeting and support all compliance and enforcement regulations.
  • Complaint – This is from the result of a public call, email, letter or inquiry about a violation of the environmental law.
  • Emergency Response – This is from a result of an emergency from a spill or accident.
  • Bypass/SSO – A bypass is when partially treated wastewater is discharged from a permitted outfall, Sanitary Sewer Overflow occurs as an unpermitted discharge from the collection system.
  • Special Project – This would be something that is not typically done but for some reason a need is seen to sample.
  • Investigation - This is the result of a Hazardous Waste inquiry.

What types of samples were collected?

This provides further information on the nature of the material collected and analyzed.

  • Discharge  - Wastewater Treatment Plant, Industrial, Power Plants.
  • Drinking Water – Private Wells, Household taps.
  • Soil – Lake/Stream Sediment, Encores.
  • Sludge – Drum Sampling.
  • Stormwater – Construction Run- off, Drainage areas, CAFO’s.
  • Sediment – Lake, Stream.
  • Air – SUMMA Canisters,
  • Spill – Chemical, Oil, Fuel, Pure Products.
  • Organic – Drum Sampling, Pesticides, Herbicides, Pure Products.
  • Container – Drums, Tanks.
  • Surface Water – Lakes, Streams, Ponds, Springs, Leachate.
  • Groundwater – Caves, Springs, Monitoring wells.
  • Wipes – Chemical Substances.

What does analyses/ test type mean?

This is the type of test that was used.

What information is included in the parameter/ analyte field? 

This means the sample was tested to see if it contained the substances in this column

What do the symbols in the Result/ Unit column mean? 

The results are shown here. The results are compared to either a sample from an uncontaminated area (background sample) or a specific health-based standard before drawing conclusions. See Common Notations below.

  • Common Notations and unit definitions
    • < - A symbol for “less than.”  It means a substance could not be detected by laboratory instruments. The number following the symbol indicates the instrument’s lowest possible setting for the sample.
    • ug/kg - This means micrograms per kilogram. This measurement is generally used with soil samples. It is also often referred to as parts per billion (ppb).
    • mg/kg - This means milligrams per kilogram, which is also referred to as parts per million (ppm). This measurement is generally used with soil samples.
    • ug/L - The means micrograms per liter. This measurement is generally used with water samples. It is also referred to as parts per billion (ppb).
    • mg/L - This means milligrams per liter, which is also referred to as parts per million (ppm). This measurement is generally used with soil samples.
    • cfu/100ml - This means colony-forming unit per 100 microliters. This measurement is used with water samples.
    • NTU - This means nephelometric turbidity unit. This measurement is used with water samples.
    • Please use the contact email for unit definitions not listed.  

What do the data qualifier code numbers mean?

Data qualifier related to the value in the Result column.

  • 01 Improper collection method
  • 02 Improper preservation
  • 03 Exceeded holding time
  • 04 Analyzed by contract laboratory
  • 05 Estimated value, detected below PQL
  • 06 Estimated value, QC data outside limits
  • 07 Estimated value, analyte outside calibration range
  • 08 Analyte present in blank at > ½ reported value
  • 09 Sample was diluted during analysis
  • 10 Laboratory error
  • 11 Estimated value, matrix interference
  • 12 Insufficient quantity
  • 13 Estimated value, true result is >= reported value
  • 14 Estimated value, non-homogeneous sample
  • 15 No result - failed quality controls requirements
  • 16 Not analyzed - related analyte not detected
  • 17 Results in dry weight
  • 18 Sample pH is outside the acceptable range
  • 19 Estimated value
  • 20 Not analyzed - Instrument failure
  • 21 No result - spectral interference
  • 22 pH was performed at the laboratory
  • 23 Contract lab specific qualifier-see sample comment
  • 24 No result - matrix interference
  • 25 No Result: Excessive Chlorination
  • 26 No Result: Excessive Dechlorination
  • ND Not detected at reported value

What is MCL?

A Maximum Contaminant Level (MCL) is the amount of a substance that is allowed in public water under the Safe Drinking Water Act.

What does Method mean?

This number specifies the method used to perform each test.


This indicates which office should be contacted for questions about a specific sample. 

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

For more information