Louisiana Administrative Code
Title 48 - PUBLIC HEALTH-GENERAL
Part V - Preventive Health Services
Subpart 28 - Drinking Water Laboratories
Chapter 80 - Certification of Laboratories Performing Drinking Water Analyses
Subchapter C - Criteria and Procedures for Chemical Testing and Analysis
Section V-8061 - General Laboratory Practices

A. Chemicals/Reagents. Chemicals and reagents used must meet the specifications in the referenced method. If not specified therein, then analytical reagent (AR) grade or American Chemical Society (ACS) grade chemicals or better shall be used for analyses in certified laboratories.

B. Reagent Water. The laboratory shall have a source of reagent water having a resistance value of at least 0.5 megohms-cm (conductivity less than 2.0 micromhos/cm) at 25°C. High quality water meeting such specifications may be purchased from commercial suppliers. Quality of reagent water is best maintained by sealing it from the atmosphere. Quality checks to meet specifications above shall be made and documented at planned intervals based on use. This planned interval should not exceed daily. Individual analytical methods may specify additional requirements for the reagent water to be used. Reagent water for organic analysis must be free from interferences for the analytes being measured. It may be necessary to treat water with activated carbon to eliminate all interferences. If individual methods specify additional requirements for the reagent water to be used, these must be followed.

C. Glassware Preparation. Specific requirements in the methods for the cleaning of glassware must be followed. If no specifications are listed, then glassware should be washed in a warm detergent solution and thoroughly rinsed first with tap water and then with reagent water. This cleaning procedure is sufficient for general analytical needs. It is advantageous to maintain separate sets of suitably prepared glassware for the nitrate, mercury, and lead analyses due to the potential for contamination from the laboratory environment. For a summary of glassware cleaning procedures, refer to Chapter IV of the USEPA Manual for the Certification of Laboratories Analyzing Drinking Water.

D. Distilled and deionized water shall have at a minimum, resistivity values between 0.5 to 2.0 megohms-cm (2.0 to 0.5 micromhos/cm.) at 25o C. Preferably, distilled and deionized water should have resistivity values greater than 1.0 megohms-cm (less than 1.0 micromhos/cm) at 25oC. When purchasing distilled or deionized water, laboratories should request a list of quality specifications for the water purchased. Containers of distilled or deionized water should be capped when not in use and should be capped immediately after each use.

E. All solutions shall be properly labeled with identification of the compound, concentration, solvent, date, and analyst who prepared the solution.

F. All chemicals, solutions, and standards, shall be dated upon receipt by the laboratory; and the date opened by the laboratory shall also be noted.

G. Compositing of samples for inorganic and organic analyses must be done in the laboratory. Samples shall only be composited if the laboratory detection limit is adequate for the number of samples being composited (up to a maximum of five) and the holding times will not be exceeded.