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Analyzing different types of water samples on a regular basis presents several challenges for analysts. Depending on the type of lab (e.g., municipal or water bottling facilities), the number of samples to be analyzed can vary significantly. Every day such laboratories receive hundreds of samples that must go through pH, conductivity, and alkalinity testing, among others. If additional tests are requested on top of that workload, the lab team must carry out all of them as quickly as possible—while delivering reliable results.
Another possibility is that some water samples must be analyzed according to different international standards, as the final product may be shipped to different countries, as in the case of beverage production. Sample preparation can be quite tedious and error-prone when it must be carried out for hundreds of samples every day, especially when the sample size for various tests differs significantly.
A high number of samples already presents a challenge for laboratories. Once this number reaches the point where it is not possible for a single analyst to carry out all determinations of one type, slight differences in the results will appear as each lab member treats the sample slightly differently. More analysts working on the routine samples introduces more bias, and this can be plainly seen in the variability between results.
Due to the sheer number of samples to be analyzed on a daily basis, automation is the key in order to deal with all of these obstacles. The goal is to automate the routine application process as much as possible, including sample preparation as well as the combination of different techniques within one system to make the workload easier. Most drinking water samples must be analyzed for conductivity, pH, and alkalinity. Sample throughput is always a very important consideration for water quality laboratories. Therefore, analyses should be carried out in parallel to save time because of the high sample load.
In the setup shown above, multiple parameters like pH, alkalinity, and water hardness are able to be analyzed on a single workstation. This combination of analyses can be done on three workstations at the same time. The conductivity (shown in yellow) is still analyzed on a dedicated workstation to prevent any falsification by the electrolyte outflow of other electrodes when the conductivity values are very low.
Time savings with parallel determination
Based on the previous example, it is obvious that the described instrument setup can result in significant time savings. In fact, up to 64% of analysis time can be saved by automating and running determinations in parallel rather than in series.
This figure is based on the fully automated determination of conductivity, pH, alkalinity, and hardness for 63 samples. Running these four determinations on just one sample requires 12 minutes as shown below. When run in series, this results in more than 12.5 hours, while parallelization can reduce the time needed for these analyses to 4.5 hours (64% time savings).
| Analysis type | Duration |
|---|---|
| 1 sample | 12 minutes |
| Series: 63 samples | 12 hours 36 minutes |
| Parallel: 63 samples | 4 hours 31 minutes |
Whether due to the matrix or for other reasons, it is possible that not all of these parameters have to be determined for each sample. In such a case, a system with dedicated workstations for specific applications (such as the one shown below) might be a better choice for optimal lab flexibility.
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For example, the system shown here holds four dedicated workstations for the determination of conductivity, pH and alkalinity, water hardness, as well as chloride. In this way it is ensured that each sensor is handled and stored in the most suitable way. Additionally, influences from one analysis to another can be completely avoided. With this system setup, a sample is either prepared separately for each station, or it can be passed from one station to the other.
Reduce errors and increase analysis flexibility
The biggest advantage with this setup is that errors attributed to incorrectly mounted electrodes or buret tips can be easily avoided. Due to its flexible design, this system with dedicated stations can simply be modified to become one that runs the same analysis in parallel. This allows sample throughput to be increased in case of a peak request for certain kinds of water analysis.
Conclusion
No matter whether you are interested in determining several parameters or just one or two specific ones, an automated system such as OMNIS from Metrohm can be tailored to your needs and requirements. If these change after some time and more detailed ion analysis becomes necessary for example, then ion chromatography can be easily added to the existing system setup. Less sample volume is needed as it is no longer necessary to split it into several aliquots for measurement on different instruments.
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