Solutions
for do it yourself water testing.
Home page.
|
Dissolved oxygen. 3 ways to measure dissolved oxygen. Chemical test kit. An example is the HI3810 Dissolved Oxygen test kit. See it at HI3810 kit. This kit has 5 chemical components and uses a modified Winkler method. The method is simple because the chemicals are pre-prepared and easy to dispense. The last step is a titration. The reagent is added with a graduated syringe until a desired colour change occurs. The value is read off and a simple calculation gives dissolved oxygen in ppm.. You can measure to the nearest 0.1 ppm between 0 and 10 ppm amd to an accuracy of 0.5 ppm between 0 and 5 ppm. The original kit costs around $132 for 110 tests but a replacement reagent kit costs around $89 for a further 100 tests. Photometer. A neat solution is to combine chemical methods with an instrument which will detect the colour in the final solution. An example of this type is the HI93732N Disolved oxygen photometer. See this meter at HI93732N D O photometer. Cost for this meter is around $574 and the reagent set is purchased separately at around $105 for 100 tests. The kit uses 3 reagents. Using this meter is straightforward. Place a sample of the original water in the meter to obtain a zero reference point. Then react the chemicals with the sample and place some of the final solution in the meter. The meter gives the actual dissolved oxygen value. This meter is portable so can be used away from the lab. Dissolved oxygen meter. This type of meter measures dissolved oxygen directly in water with an oxygen sensitive probe. An example of this is the HI9142. See it at HI9142 Dissolved Oxygen meter. Meters like this cost around $1100 and upwards. Only one calibration solution is required at around $30. The probe may need to be topped up with filling solution (supplied) and sometimes the very delicate membrane at the bottom of the probe needs to be replaced so there is a small maintenance cost. These meters can be taken anywhere. So which way to go? There is relatively little difference in the accuracy of each of the 3 methods. The D O meters offers a wider range over the kit and photometer, 0 - 20 ppm. The kit is less convenient to use under field conditions. The initial outlay for the kit is low but if you plan to do frequent testing then the cost per test using the photometer and meter will come down. If speed and ease of use is important then the D O Meter wins.
Chlorine (coming) |