Quality of Water and Glassware Washing

Defined Water Types

Each laboratory section defines the type of water necessary for each of its procedures as required by the test manufacturer or published guidelines. The current edition of the Clinical Laboratory Standards Institute (CLSI) Guideline GP40-A4-AMD defines the following grades of water: Clinical Laboratory Reagent Water (CLRW), suitable for most laboratory procedures; Special Reagent Water (SRW), defined by a laboratory for procedures that need different specifications than CLRW; Instrument Feed Water, specified by IVD manufacturers as suitable for use with their measurement systems; and Commercially Bottled Purified Water that may be suitable for certain laboratory procedures. CLRW is similar to the Type I reagent water defined in earlier editions of this guideline. CLRW is not required if the laboratory is able to document reliable results with an alternate grade of water.

The following specification for CLRW is adapted from this guideline and should be met at time of in-house production:

• Bacteria may inactivate reagents, contribute to total organic contamination, or alter optical properties of test solutions. Resistivity provides a non-specific measure of the ion content. Particulate matter includes organic carbon from biofilms and inorganic aggregates that can vary over time both in nature of the contamination and the effect on the laboratory use.

• The CLSI Guideline GP40-A4-AMD provides testing information for microbial content, and resistivity, as well as total organic carbon; earlier specifications for silicates have been removed. It gives instructions for the preparation of the various types of water. It also addresses the use of purchased water, the effects of storing water, and the monitoring of stored water.

• The quality (specifications) of the laboratory's water, whether prepared in-house or purchased, must be checked and documented at least annually. The frequency and extent of checking may vary, according to the quality of source water and specific laboratory needs. Corrective action must be documented if water does not meet acceptability criteria.

• For CLRW, minimum monitoring includes resistivity and microbiology cultures. Other criteria, such as pH, endotoxin/pyrogens, silicates, and organic contaminants are at the discretion of the laboratory; testing for these substances must be documented only if the laboratory finds that they adversely affect specific test methods.

• The laboratory must determine the level of testing necessary for other grades of water in use.

• Typically, "sterile (pharmaceutical) water" is not manufactured to meet the specifications of CLRW, and should not be used as its equivalent.

• For commercial instrument-reagent systems, the laboratory must use a specific type of water recommended by the manufacturer. Although routine commercial methods are typically designed to work with laboratory reagent grade water, higher-quality water systems exist and may be required for specific methods or if analytical imprecision or inaccuracy has been traced to the quality of in-lab water.

Water Quality Control – Annual

The technical staff of each area confirms water resistance with each use and troubleshoots the purification equipment if necessary (e.g., change filters, change cartridges, place a service call). In addition, resistivity is checked after maintenance performed by the Neu Ion or Millipore (current vendors) representative, or documented from the readout on NeuIon or Millipore Systems.

The quality (specifications) of the laboratory's water, whether prepared in-house or purchased, must be checked and documented at least annually. The frequency and extent of checking may vary, according to the quality of source water and specific laboratory needs. Corrective action must be documented if water does not meet acceptability criteria.

Reagent grade water (type I and II) is monitored for bacteria annually. The Clinical Manager or designated technical staff member performs the bacterial monitoring according to the instructions below. After the cultures are analyzed, results are reviewed by his/her designated supervisor and distributed to each section.

Each section may opt-out and perform individual microbial checks, and will be responsible for corrective actions and retaining all records.

Supplies:

• Millipore Heterotropic Plate Count (HPC) Sampler, Catalogue #MHPC10025

• Bausch & Lomb Binocular Sterioscope with Illuminator, Room 2A10

Procedure:

• Wear gloves when performing this procedure.

• Remove the sampler from its plastic bag and label the case with location and date of sampling.

• Allow water to flow for 20 seconds. Verify appropriate resistance by noting the illuminated light on the tanks or the Millipore print-out. Fill sample case to the upper (18ml) graduation.

• Insert the sampler firmly into the case containing the water sample, and carefully lay the unit with the membrane facing down onto a flat surface. Make certain the membrane is uniformly wetted; do not agitate. Allow 30 seconds for the sample to be drawn through the filter.

• Remove the paddle and, with a firm snap of the wrist, shake off the excess liquid. Empty the case and reinsert the paddle. Make sure the paddle is seated firmly in the case to form an air-tight seal.

• Incubate the sampler, grid side down, at 25-35°C for 72 hours.

• Record the temperature of the incubator each day.

• Examine the filter after incubation is complete. Remove the paddle from the case and examine the filter surface with the sterioscope. The appearance of microbial colonies will vary. Most colonies are glistening, and translucent or transparent. Colors vary from colorless to white, cream, yellow, or red.

• Count the colony forming units (CFU) on the filter. The number of colonies observed on the filter is the number recorded (as CFU/ml). If colonies are too numerous to count, record TNTC. If detected, growth is reported to the supervisor of the appropriate section on the day it is observed. The following information is from the CLSI Guidelines: 

Copies of the completed Bi-Yearly QC worksheet are distributed to each section.

Glassware Washing

Each section must document procedures for handling and cleaning glassware, where this is done. Documentation must include methods for testing for detergent removal.

• A simple procedure to check for detergent residue uses bromcresol purple (0.1 g bromcresol purple in 50 mL ethyl alcohol). Pipette a column of 5 cm distilled water into a representative, washed, glassware item. Add two drops bromcresol solution. A purple color reveals residual detergent. A yellow color indicates satisfactory rinsing.
  
  

• In order to detect detergent residues resulting from improper rinsing, a pH meter or pH paper qualiyt control (QC) method can be used: 

  a. Rinse a small clean beaker by filling and emptying 3 times with source water. 

  b. Fill a fourth time and measure pH using a pH meter or pH paper. Record the pH as source water pH.

  c. Take a piece of newly-cleaned glassware in order to test, fill about 10% full with source water. Use more water if necessary to get enough water to be able to sufficiently immerse the pH meter electrode or pH paper. 

  d. Agitate water in glassware to extract residues from all possible surfaces.

  e. Take pH reading with pH meter or paper and record as glassware pH

  f. Any significant increase in pH indicates alkaline detergent residue. A significant change is 0.2 or more pH units measuring to 0.1 pH units of sensitivity. A result of less than 0.2 pH unit change indicates properly rinsed glassware.
  
  

• Note regarding pH paper: detergents and surface active agents can interfere with some pH paper by causing a decrease of several pH units in reading. Please test any pH paper you intend to use with these detergents to determine if there is any interference before implementing pH paper method.

REFERENCES:

Clinical and Laboratory Standards Institute. Preparation and Testing of Reagent Water in the Clinical Laboratory; Approved Guideline. 4th ed. CLSI document GP40-A4-AMD. Clinical and Laboratory Standards Institute, Wayne, PA, 2012.

Stewart BM. The production of high-purity water in the clinical laboratory. Lab Med. 2003;31:605-611.

Silicate Testing

LP has evaluated its source water to determine if a high concentration of silicates is present. Results are within normal limits (< 0.05 ppm) and may be viewed by contacting the Clinical Manager.