What’s New in the Food Analysis Toolkit?

With increasing pressures to turn around results as speedily, accurately and easily as possible, developing an analytical solution that can deliver on all of these is clearly on most company’s wish list. In areas, such as food analysis where detection of contaminants may be imperative to prevent dangers to consumers, speed and reliability is key. Direct Analysis in Real Time (DART) is emerging as a popular choice for sample ionization in such circumstances, being both versatile and fast.

We spoke to Tim Jenkins (TJ), Director of Food & Environmental Global Markets at Waters Corporation, about their coupling of DART to the QDa mass detector with a software solution aimed to enhance compound identification.

KS: Can you explain how DART ionizes samples?

TJ: DART is a desorption based atmospheric pressure chemical ionization technique. It is a rapid technique which operates under ambient conditions making it simple to quickly analyze a broad range of sample types including solid and liquid based food ingredients and products.

A stream of heated gas (typically helium or nitrogen) is exposed to an electrical discharge which generates a stream of reagent ions. These are directed at a target containing the sample which is located between the DART interface and the inlet to the mass spectrometer. The reagent gas stream hits the sample and liberates ions from the surface which are then drawn into the mass spectrometer for analysis.

A number of sample holder and automation options are available for the system which ensures that multiple samples can be analyzed quickly and efficiently.

KS: How does the data from Waters’ DART QDa compare to traditional MS techniques?

TJ: The QDa mass detector employs a single quadrupole mass analyzer and so produces conventional mass spectra associated with quadrupole-based mass spectrometers. The DART ionization technique is a soft ionization technique, which means that it produces simple spectra that are relatively straightforward to interpret and easier to characterize and use for compound identification.

QDa mass detector technology makes the system very easy to use and gives analysts without a lot of experience with mass spectrometry, the ability to generate their own mass spectra for each sample. The QDa calibrates itself and minimizes the need for user intervention during setup and operation thereby making it simple to obtain high-quality mass spectral data.

KS: What features make Waters’ DART QDa so suitable for food analysis?

TJ: There are several features that make DART QDa a valuable solution for food testing. The first is that DART QDa is capable of analyzing a wide range of molecules and is therefore highly-suited to the analysis of food-related samples where a wide range of chemistries are encountered.

Secondly, the measurement is obtained rapidly and directly with no requirement for chromatographic separation or extensive sample preparation. This is a very simple technique to operate especially as part of the system with the QDa mass detector.

The DART QDa system’s simple operation and its small footprint facilitates deployment both inside and outside of the traditional lab environment. That in turn means the technique has the potential to be used as a rapid screening tool or to support fast decision-making at critical points of the supply chain or manufacturing process.

One of the greatest advantages of the DART QDa system is its speed, creating a database of measurements from a large number of samples from diverse sources such as different suppliers, regions, processes, storage environments etc. These large mass-spectra-based, fingerprint databases can be used with appropriate software to answer a host of questions associated with food integrity like whether a sample is authentic in terms of its identity, origin or claimed production method. Has anything been added or substituted in the product? Is it good or bad quality? Is it labeled correctly?

KS: How does the software help scientists make decisions quicker?

TJ: Software plays a key role in the successful deployment of the DART QDa system. At the outset, it is important to consider the reason for the analysis. Is it to confirm the identity of a substance based on the presence of certain specific mass peaks in the spectrum? Or is it to check for authenticity or adulteration by looking for the presence or absence of peaks that are characteristic of the authentic substance and/or indicative of known adulterants? Such experiments are rapidly carried out with the DART QDa and decisions can be made immediately about a sample based on the mass spectrum obtained. An example is the screening of different samples of cinnamon, a popular spice that is commonly adulterated.

Where the mass spectral fingerprint of authentic substances or the identity of potential adulterants is known, it is relatively straightforward to answer certain questions by directly interrogating the acquired mass spectra. However, it is not always that simple!

Often in food testing the questions that must be answered and level of data required to address them demands a more sophisticated approach. Waters has developed LiveID software which, in combination with the DART QDa system, can drive the application of direct mass spectrometry to new levels of performance, meeting an ever broader range of food testing challenges.

When using DART QDa with LiveID, samples verified as authentic are used to generate mass spectra. The mass spectra obtained from the DART QDa are very information-rich in terms of providing a molecular profile, or fingerprint, of the chemical components within a sample. These spectra are imported directly into the LiveID software where data analysis tools build and validate a statistical model of the samples under examination. Validated models can then be used with test samples to generate real-time classifications based on their similarity or difference as compared to the samples in the model. Output is a simple yes/no answer enabling immediate decision making.

LiveID software offers a workflow-driven process with a modern, visually attractive, web-based interface which is very easy to learn and use even for those with little, or no, mass spectrometry expertise. With LiveID software the analyst does not need to interpret mass spectral information - the modelling software handles the data analysis. This means that it is especially powerful for classifying samples without the direct need to identify specific components within the spectra. All that is required is the sample metadata (e.g. origin, age, supplier, quality, etc.) upon which the classifications in the model are built.

KS: Do you envisage that the Waters’ DART QDa will be used as a rapid analysis tool alongside conventional MS techniques or as a standalone system? 

TJ: We see scenarios for DART QDa both as a standalone system and in supporting existing LC/MS and GC/MS technologies. Just as I mentioned when discussing software, it comes back to an understanding of the question and the consequences of the decision made based on the measurement.

The speed and simplicity of the technique make it well-suited as a rapid screening or “triage” technique. In this way it can monitor large numbers of samples for a known contaminant or adulterant and be deployed outside of a core testing lab in a more decentralized way, perhaps supporting monitoring of a large, even global, supply chain. Samples deemed authentic based on their test results could continue through the supply chain with minimal delay while samples deemed inauthentic may be rejected or require further confirmatory testing perhaps by LC/MS in a central, more specialist analytical laboratory.

So, we do see a role supporting existing analytical approaches in which the speed and simplicity of DART QDa enables the rapid screening of a greater number of samples across a wider environment than would otherwise be possible using a centralized lab running LC and/or GC mass spectrometry methods. This allows the customer to focus resources - equipment and time - more efficiently on suspected positive samples which saves money and, potentially, increases the number of samples that can be tested because of the availability of a fast screening technology.

There is also great interest in the use of DART QDa with LiveID as a standalone technology. At launch we have targeted food applications in areas where rapid, real-time fingerprinting is essential and where sample preparation is not necessary or desirable. Here the ability to build and validate models for real-time classification of samples delivers unique value and has potential to transform many aspects of food testing such as determining origin and authenticity and assessing quality and safety.

By their nature, Waters customers are creative and innovative. We are keen to see how they use our direct mass spectrometry platforms like the DART QDa to create value for their organizations in the future. We are confident that direct mass spectrometry will play a key role in supporting an authentic, safe, sustainable and nutritious global food supply.

You can learn more about the Waters DART QDa with LiveID system here.

Tim Jenkins was speaking to Dr Karen Steward, Science Writer for Technology Networks.