A. pH Meter Method
- Rinse a small clean beaker by filling and emptying 3 times with source water
- Fill a 4th time and measure pH using a pH meter. Record the pH as source water pH
- Using a piece of cleaned glassware you wish to test, fill about 10% full with source water (10ml into 100ml beaker). Use more water if necessary to get enough water to be able to sufficiently immerse the pH meter electrode in your measuring beaker
- Swish water in glassware to extract residues from all possible surfaces
- Take pH reading with pH meter and record as glassware pH
- Any significant increase in pH indicates possible alkaline detergent residue. A significant change is 0.2 or more pH units on a pH meter measuring to 0.1 pH units of sensitivity. A result of less than 0.2-pH units change indicates properly rinsed glassware
Note: If deionized water is used as the sample water, a slight amount of reagent grade, non-buffering salt (NaCl, CaCl2) should be added to the sample water to allow pH meter to function properly. If you want to avoid contaminating clean glassware, dump the glassware testing solution into a triple rinsed beaker and then add the non-buffering salt prior to measuring the pH with a meter.
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 adapting this procedure for use with pH paper.
You should test approximately 1% of large frequently washed quantities of glassware and 5% of smaller quantities of less frequently washed glassware, and you should rotate the types of glassware tested. Particularly try to test narrow necked volumetric flasks more frequently. Keep records of the test date, types of glassware tested and test results.
The above procedure A is effective for the following Alconox, Inc. detergent brands: ALCONOX®, LIQUI-NOX®, TERG-A-ZYME®, ALCOJET®, DET-O-JET® and DETERGENT 8®.
If you are testing for CITRANOX® or CITRAJET® detergent, please adapt the procedure to test for an acid residue and therefore determine if there is a significant lowering of 0.2 pH units as in step 6 an acid shift would indicate an acid residue.
B. pH Indicator Method for Alkaline Detergents
- Materials
- 0.04% Bromothymol Blue (Aldrich 31,875-2), or prepare in 250 ml reagent grade water with 16 ml of 0.01 N NaOH to 0.1 g Bromthymol blue (Aldrich cat no 11,441-3)
- Reagent grade water pH 5.5-7.5
- Select glassware to be evaluated for alkaline detergent residue, fill 1/2 full with reagent grade water
- Swish water around the glassware to extract any residues off the sides
- Add 2-3 drops of 0.04% Bromthymol Blue and observe the color
- A pale blue color is a failing reading indicative of an alkaline residue
- A blue/green color is indicative of a passing neutral pH
- A yellow color can also be passing if you water is in the pH 5.5-6.5 range
The above procedure B is effective for the following Alconox, Inc. detergent brands: ALCONOX®, LIQUI-NOX®, TERG-A-ZYME®, ALCOJET®, DET-O-JET® and DETERGENT 8®.
C. Detergent Test Kit Method for Neutral pH Anionic Detergents
If you are testing for ALCOTABS® detergent, please adapt the procedure to use a detergent test kit that is sensitive to anionic detergent residues. These kits are available from:
- Chemetrics Inc. water testing kit for anionic detergents, which is sensitive to 1/4 ppm. Contact Chemetrics, Inc. at 1-800-356-3072.
- LaMotte Chemical water testing kit for anionic detergents, which is sensitive to 1 ppm. Contact LaMotte Chemical at 301-778-3100.
- Hach Company water testing kit for anionic detergents, which is sensitive to 1 ppm. Contact Hach Company at 1-800-227-4224 or 303-669-3050.
Use the kits to test for detergent in rinse water that has passed through a pipette. If no detergent is detected with the kit, you can conclude that there is no interfering residue from the ALCOTABS®.
Thank you for your interest in Alconox, Inc. detergents.
Copyright 1997 - Alconox, Inc.
