Accurate Water Testing

Republished with permission from Water Online: "The Perfect Solution for Simple, Fast, and Accurate Water Testing," September 1, 2016


Laboratory technicians are continually pressured to perform more analyses with greater accuracy and better data management. Quality assurance and control are paramount, and customers need results quickly.

MilliporeSigma* understands the challenges that laboratories face. Their team focuses on high-quality solutions to streamline processes and save costs while ensuring regulatory compliance.

Water Online spoke with MilliporeSigma to find out how spectrophotometers can help laboratories meet these ongoing challenges.


Laboratories that perform water testing typically use spectrophotometers for many of the analyses. What are the most important requirements lab managers are looking for in this tool?

Most users will look at cost, accuracy/ reliability, and ease of use as their primary criteria for selection. Accuracy and reliability are self-explanatory, but often the full ramifications of cost and ease of use go unexamined. When looking at cost, we always encourage customers to consider the full life-cycle cost. Lamp costs, service agreements, and the price of test kits should all be accounted for when comparing costs. Additionally, ease of use directly impacts man-hour costs for a lab. These are all criteria that should be closely examined.

How is the data from these instruments securely transmitted to other devices or to the laboratory information management system (LIMS)?

Test results can be stored securely on the instrument itself and exported via a USB stick or sent directly to a printer according to the user’s convenience. Some systems, such as the Spectroquant Prove instruments, were designed with an Ethernet port with LIMS integration currently in development. When communication with the major LIMS software packages is finalized, customers can implement that feature with a software update.

What parameters can be tested using these instruments?

These instruments are able to test numerous parameters using various test methods. Spectrophotometers may come pre-programmed with methods for tests ranging from absorbance to zinc, including methods for use in high-salinity environments. Beyond the pre-programmed methods though, some companies have applications’ labs dedicated to helping customers develop custom methods. If you have a challenging application, check to ensure your supplier will be able to assist you with developing a custom test method.

At both stand-alone and treatment-plant laboratories, the technicians are pressured to perform more analyses in a shorter time while maintaining precision and accuracy. Do any of these instruments include features to save time and maximize efficiency?

Helping laboratory technicians do their work more quickly and accurately is imperative for laboratory equipment suppliers. Supplying test kits and having pre-programmed test methods can simplify and speed up analyses. The Spectroquant Prove instruments were designed with speed and workflow efficiency as a top priority. The two core features for this are the cell test port and Live ID bar codes. The cell test port allows users to insert 16-mm round cells into the instrument directly without manipulating any lids or latches. The Live ID bar code on the cell test kits is automatically scanned when cells are inserted to select the correct method, test range, and calibrations. Between the two features, it is possible for the user to get results within seconds without having to touch the instrument.

How can data errors, including test-specific lot and expiry data, be avoided or reduced when conducting tests with a spectrophotometer?

In many cases it is up to the technician to manually track and record this information. MilliporeSigma has eliminated the potential for these types of data errors by eliminating the need for the end-user to keep track of the information manually. The Live ID bar code contains lot information and expiry data, which is logged when the test kit is inserted into the spectrophotometer. In the event a user tries to use a test kit that has expired, an alert will pop up to notify the user the test has expired, and they can choose to proceed or cancel the test.

Is there any way to eliminate fluctuation of results due to temperature variability?

The most common approach is the use of a split-beam or reference-beam design. This approach involves using a splitter to send the light beam in two directions. The first beam passes through the sample, while the second is sent to a second detector without passing through the sample. This separation allows the instrument to separate out the interferences and deliver results that are based solely on the absorbance of the sample analyte.

When choosing a spectrophotometer, are there options for more sensitive or complex analyses?

The most common method for increasing spectrophotometric sensitivity is to increase the path length that the light has to travel through the sample. Most spectrophotometers will allow users to run samples in cuvettes from 10 to 50 mm. The Spectroquant Prove 600 was specifically designed to allow users to use up to 100-mm cuvettes specifically for those applications where high sensitivity is required. MilliporeSigma is in the process of developing additional methods for 100-mm cells, or the end-user can create and calibrate their own methods using our test kit chemistries in 100-mm cells.

How can a spectrophotometer help laboratory technicians ensure the accurate documentation essential in the water industry?

There are a number of features to help ensure accurate documentation in the lab. The USB ports on the device can be used to attach bar-code scanners and/or full-size keyboards for sample ID input. Additionally, there is a software feature that can be activated requiring a sample ID be inputted before the device will run the test. All of these features allow labs to customize how they maintain sufficient documentation for sample analysis. Any and all data that is inputted by the lab technicians is permanently associated with the test and stays with the sample results when they are exported.

How can a spectrophotometer help to ensure secure and streamlined analytical quality assurance (AQA)?

Some spectrophotometers allow for programmed quality assurance checks. The Spectroquant instruments have multiple pre-programmed AQA checks built into the system. The AQA 1 test works in conjunction with PhotoCheck test kits to ensure the instrument is returning expected results. AQA 2 is a pre-programmed method to check the entire package of instruments, test kits, pipettes, and operator. Both checks have simple-to-follow instructions displayed on the screen and can be programmed for regular prompts to perform the checks at scheduled intervals.

Sometimes it’s necessary to develop a new test method in-house. How can that be accomplished?

Check with the instrument supplier to determine if a custom test method can be used or developed. User defined methods are absolutely possible with the Spectroquant Prove instruments. Tests can be defined using concentration, spectrum, or kinetic methods, and there are comprehensive step-by-step instructions in the user manual as well as prompts on the screen when the user selects “Add New Method” on the menu. Should customers have any problems in developing or programming their new method, they will always have access to our applications’ lab for support and guidance.


*The life science business of Merck KGaA, Darmstadt, Germany operates as MilliporeSigma in the U.S. and Canada.