Methods, PQLs, QA

Information regarding Analytical Methods and Practical Quantitation Limits (PQL's) for Inorganic Chemistry laboratory analyses, and the Laboratory's Quality Assurance Unit: 

Analytical Methods and PQL's - Inorganic Chemistry:

Biological and chemical analyses conducted by the Microbiology and Inorganic Chemistry Branch follow EPA-approved analytical methods. The sources of these methods include the USEPA, Standard Methods, and ASTM.

Each analytical procedure has a Practical Quantitation Limit (PQL), which is defined as "the lowest concentration that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions." PQLs are subjectively set at some multiple of typical Method Detection Limits (MDLs) for reagent water (generally 3 to 5 times the MDL). The PQL for a procedure may also be defined by: a reporting limit or minimum limit (ML) specified by the analytical method; sample volume and buret graduations; and/or minimum measurement values that are method-defined. The established PQL for a procedure serves as a reliable and routinely achievable reporting limit for a biological or chemical parameter. 

NCDENR DWR WSS Laboratory Practical Quantitation Limits Updated  2/8/2018

Note: Unless otherwise noted, PQL's and methods are for water samples only.

Quality Assurance Unit  (WSS Chemistry Laboratory):

The Quality Assurance (QA) unit is responsible for establishing, implementing and coordinating a comprehensive Quality Assurance/Quality Control (QA/QC) program for environmental sample analyses performed by the WSS Chemistry Laboratory. This includes the branches located in the Central Laboratory as well as the Asheville Regional Laboratory. 

Laboratory Quality Assurance Officer: Nick Jones

Telephone: 919-733-3908, extension 232


Goals of the Quality Assurance Unit:

The QA unit is dedicated to ensuring that environmental data operations are of a quality that meet or exceed requirements for informed decision making. This unit is responsible for providing information, guidance and expertise in quality control and regulatory compliance issues.

A well-conceived QA program provides a sound framework for the generation of laboratory data that is scientifically valid, representative and legally defensible. The validity and reliability of the data generated by the WSS Chemistry Laboratory are assured by adherence to rigorous QA/QC protocols. The fundamental elements of the WSS Chemistry Laboratory's QA program include Standard Operating Procedures (SOPs), quality control practices, performance testing samples, internal and external audits and an ethics policy.

Data Qualifier Codes :

Environmental laboratory data validation is accomplished through a series of checks and reviews that are intended to assure that reported results are of a verifiable and acceptable quality. When the accuracy of those results is uncertain (as indicated by deviations from established quality control limits), the laboratory must provide sufficient information to allow for independent interpretation of data validity and usability. This may include additional associated information about a sample that may not necessarily invalidate the data (e.g., reducing agents detected in a BOD sample), but must be taken into account during data assessment. This information is communicated to Departmental personnel on data reports by means of data qualifier codes.

Historically, these Remark Codes were mandated and defined by the Environmental Protection Agency’s Legacy STORET data management system. In March of 2001, the NC Division of Water Resources Chemistry Laboratory implemented a revised suite of data qualifiers. The following table provides a key to the data qualifier codes used for analytical results reported by the Water Sciences Section's chemistry laboratories located in Raleigh and Asheville. The reported value always precedes the data qualifier code. Contact the laboratory any time you have questions about data qualification and interpretation.