A discrete analyzer is an automated chemical analyzer in which the instrument performs tests on samples that are kept in discrete cuvettes in contrast to a continuous flow analyzer that uses a peristaltic pump for a continuous stream of reagents. Discrete analyzers initially made their appearance in the clinical market, but are now widely used for the automation of manually run wet chemistry testing across a myriad of labs, including environmental (water, soil, plant extracts and fertilizers), food and feed, beverage (wine and beer), chemical and quality control.
In addition to accurate and reproducible testing, the goal of discrete analyzers is to offer a reliable and convenient walkaway solution to increase overall lab productivity. A walk-away experience is determined by the number of available positions for samples, method dilutors, reagents and QCs (plus calibrator stock solutions) in line with the loaded on-board methods. This has a direct impact on the way a laboratory manages its processes and procedures when working with a discrete analyzer, as it is important to select the size of analyzer based on the real working routine of the laboratory.
Key Considerations When Selecting a Discrete Analyzer
While this list is not comprehensive, it does provide key considerations for lab managers who may be in the market for a new discrete analyzer, whether it’s your first or tenth. Before making a final decision, consider the following discrete analyzer characteristics and how each suits your laboratory environment.
Consideration #1: Number of tests per hour (sample throughput)
Together with number of reagent positions, sample load capacity—or the number of sample positions—is an especially important consideration because it is what truly defines the scope of the unit. Before you decide on a unit, be sure to conduct an analysis of your laboratory’s sample needs. Purchasing a unit that processes 200 tests/hour with 5 racks for continuous loading (126 position) will not be helpful if the lab is actually processing 600 tests/hour utilizing two independent carousels hosting 20 racks of 10 positions each.
Additionally, the type of samples must be taken into consideration. If your lab has special chemistries, be on the lookout for a discrete analyzer that supports different sample prep modules for different chemistries. For example, the SmartChem series has a sample prep module for the determination of NOx by cadmium reduction, as well as pH, conductivity and redox modules.
Consideration #2: Type of cuvettes—single use versus reuseable
With discrete analyzers, you have your choice of single-use disposable or reusable cuvettes. Produced in large quantities, the cost of single-use disposable cuvettes is minimal (just cents) compared with their reusable quartz counterparts. They can also be time-intensive due to the washing and cleaning that must occur between measurements.
According to Roberto Marcos Perchin, Business Development Manager at KPM Analytics, reuseable/non-disposable cuvettes ensure a true unattended walkaway experience for the complete test run. If you are considering a system that utilizes reusable cuvettes, it is important to look for one with a dedicated washing station built into the device. This feature ensures the cuvettes are washed after each measurement, and that their cleanliness is tested optically to eliminate compromised sample measurement. There is also a sustainability advantage to reusable cuvettes.
Consideration #3: Level of automation (reliable software)
The level of automation and software workflow—which play an important role in ease-of-use and walkaway freedom—are critical considerations in the purchase of a discrete analyzer. As a full walkaway solution, lab managers should look for a testing workflow that is easy to learn, can be left unattended and improves throughput, system uptime and staff productivity.
All software must meet regulatory requirements, including advanced user administration, audit trail, traceability and date and time stamped raw data.1
Other features to consider include:
- Automated calibration using single stock standard
- Automated startup and shutdown
- Auto dilution of over-range samples
- Automated spike and recovery
- Automated standard addition for complex sample matrices1
Additionally, while its only optional, many users prefer a discrete analyzer that has a built-in barcode reader for reagents and samples, as well as bi-directional LIMS connectivity.
Consideration #4: Reagent selection (ready to use)
Ready-to-use reagents and enzymatic reagent kits are important in food and beverage, wine, beer, fruit juices, and environmental analysis. This ready-to-go solution simplifies the preparation of your analysis and facilitates the use and storage of reagents. It also secures your analyses with reagents adapted to your application and your instrument. Be sure to check how many and the diversity of the offered ready-to-use reagents and the regulatory methods they follow. Many manufacturers offer guarantees stability, reproducibility and traceability with their ready-to-use reagents.
If sustainability is a priority, consider a discrete analyzer that completes microliter reactions, reducing reagent use and waste generation and improving cost efficiency and environmental footprint.
Additionally, if you opt for a unit with a built-in barcode reader, this level of automation will enable easy reagent inventorying and liquid level sensing.
References
1. Thermo Fisher Scientific. Discrete analyzer selection guide. https://assets.thermofisher.com/TFS-Assets/CMD/brochures/sn-73985-dia-selection-guide-sn73985-en.pdf