Your Lab water quality, does it meet the minimum
specifications?
In recent trainings that I have
administered, cleaning procedures of glassware has always been an important
topic. The following information on
Reagent Water Quality and Labware Cleaning is from the Lab QA/QC papers from
I.D.E.M. This information is available on I.D.E.M website at http://www.in.gov/idem/water/compbr/oaps/manual/part5cc.pdf
(This document is a PDF format. You can
download adobe acrobat reader at, www.adobe.com,
to open these types of files.) Labware cleaning methods vary from plant to
plant. Whatever technique or detergent you choose must be followed with a thorough
rinse procedure. Your final rinse must be done with reagent water. This article
explains the procedures and makes it clear why this is an important
process.
Reagent
Water Quality
Reagent grade water used for chemical analysis is produced in the laboratory
using distillation, reverse osmosis or ion exchange and meets the following
specifications:
Resistivity, megohm-cm
at 25 degrees C = >1
Conductivity, Fmho/cm at 25 degrees C = <1
SiO2,
mg/L
= < 0.1
In addition, if the reagent grade
water is used for bacteriological analysis, it must meet the following
additional specifications:
pH
= 5.5 - 7.5 S.U.
Total organic
carbon = <
1.0 mg/L
Heavy metals, single
(Cd, Cr, Cu, Ni, Pb, and Zn) = < 0.05 mg/L
Heavy metals, total
= < 0.10 mg
Ammonia/organic
nitrogen = < 0.10 mg/L
Total chlorine
residual = < 0.01 mg/L
Only
freshly prepared reagent water is used for ammonia analysis to prevent
contamination from ammonia in the air.
Dilution water for BOD analyses is stored in light shielded glass
carboys stoppered with clean cotton plugs.
Reagent water for other laboratory tests is stored in tightly stoppered
glass containers or withdrawn fresh from the water purification unit. (Information
From the QA/QC Manual)
Labware
Cleaning
After each use, glassware and plastic ware is washed with
detergent, rinsed with tap water followed by a thorough rinse with reagent
water. After drying, it is stored in a
cabinet. There are appropriate glassware
cleaning procedures for specific tests, for example, glassware used for total
phosphorus analysis is washed in non-phosphate detergent, acid-washed after
each use and kept separate from other laboratory glassware. (The best choice would be using a detergent
that is both ammonia- and phosphate-free, thus eliminating having different
detergents for different procedures.)
Care must be taken to store BOD bottles dry to prevent the growth of
bacteria or algae in the bottle. The BOD
siphon tubing should be cleaned monthly with dilute bleach solution (25 mL
bleach / Liter of reagent water) inspected daily for growth and replaced or
cleaned more often if any growth is observed.
All containers used to store reagent water are inspected for growth or
other signs of contamination prior to withdrawing water from them. If growth or signs of contamination are
observed, the reagent water is discarded and the container cleaned with dilute
hydrochloric acid followed by rinsing with tap water and a thorough rinsing
with reagent water.” (Information from the QA/QC Manual)
Contributors
IWEA
(formerly IWPCA) Laboratory Committee Members
Rich Huyck –
Lynn Newvine – City of
Valerie Pelz – Sherry Labs
John Rigdon – United Water
Rose Whitehead – City of
Gil Dichter – IDEXX Corporation
Barbara McDowell –
Dr. Jon Roth – Micrology Labs
Our mission, as a group, is to be a useful resource
to all wastewater facilities throughout
The IWEA Lab Committee
November 2002
Wastewater Technician