Different matrixes and tighter regulations driving triple quad MS demand - Thermo

The Thermo Scientific iCAP TQ ICP-MS was developed in parallel with the single quadrupole ICP-MS unveiled last year at Pittcon.

Shona McSheehy Ducos, ICP-MS product manager at Thermo Fisher, said the triple quadrupole is essentially the big brother of the single quadrupole and has been developed for improved interference removal and lower limits of detection.

Triple vs single quadrupole​

“A signal quadrupole system has two quadrupoles so a collision reaction cell and an analysing quadrupole,”​ she told FoodQualityNews.

“But in a triple quadrupole the first and third quadrupole are used as mass filters and the second one is the collision reaction cell. With any quadrupole system, we are using collision reaction processes in the cell to essentially get rid of interferences.​

“The uniqueness of the triple quad is with that first mass filter we are essentially isolating the analyte that we want to look at. ​

“We will also isolate any interference which is at the same mass as that analyte, but then in the collision reaction cell we are selectively removing that interference or separating the interference by either doing a mass shift of the analyte or a mass shift of the interference. ​

“So we are moving it to a different place in the mass spectrum. That difference between the reactions of the interference and the analyte is a fundamental requirement for triple quadrupole ICP-MS to work. ​

“So when we do this mass shift reaction, basically what we are going to do with the third quadrupole is then isolate that product line that we have just created in the collision reaction cell for interference free analysis.” ​

It is a more sophisticated system than a single quadrupole ICP-MS, said McSheehy.

“We’ve built it on the same platform so it has all the features and simplicity of that system. We’ve got a quick neck sample introduction system with automatic gas coupling when you insert the torch and self-aligning injector. ​

“Those are the areas that the customer is going to interact with on a daily basis so it is very important that they are able to take it apart and put it together and get access quickly.”  ​

Trend towards triple quad for food analysis​

For trace elemental analysis and in the food industry ICP-MS is still a growing technique, said McSheehy.

“The main market is single quadrupole ICP-MS at the moment but we do see a trend to triple quad or systems that can deliver improved interference removal as regulations are getting lower or we are looking at different types of matrixes and seeing challenges with those with a single quadrupole system,” ​she said. ​

“There is a trend to move towards triple quadrupole ICP-MS which is why we wanted to develop it to be as routine as possible so that labs traditionally working with single quadrupole can easily adopt this technology​.

“It has the flexibility of working in single and triple quadrupole mode so even if someone was working in a lab that is only using single quadrupole ICP-MS they can transfer their methods and SOPs onto this system and use it as a single quad and only use the triple quad when they really require it. ​

“Or it could be an application where they need mixed modes of analysis so if a lab is doing a suite of 20 or 30 analytes they may be doing 25 in single quad mode and the other five in triple quad mode.” ​

Software help and robustness of technique​

McSheehy said software is the other development.

“We’ve created a method development system called ReactionFinder and essentially this is a concept which takes all of the complexity out of triple quadrupole ICP-MS,” ​she said.

“All the user needs to do is add the analytes they want to measure in their method and ReactionFinder will chose the optimal measurement mode for that particular analyte so it is going to choose all the parameters such as the Q1 and Q3 mass and also the collision reaction cell gas.​

“If there is a reactive mode, so if we are doing a mass shift, it will chose the optimum product ion. ​

“There is an underlying database called ReactionEditor which has the matrix of all the different combinations of what is possible with a triple quad but it chooses the optimal measurement mode for the customer. The customer doesn’t need to think about that so if they are not familiar with triple quadrupole IC-MS then that is not a barrier for them adopting this technology in their lab.”​

McSheehy said a big factor for trace elemental analysis is productivity and robustness of the technique including auto dilution, automation and unattended operation.

“People are wanting to analyse more and more samples in a certain timeframe and to have that almost in an unattended analysis as well. A lot of the developments have been on the front end so the level of automation and the peripherals we connect with the system,”​ she said.

“We are already working with different auto-samplers and now we developing auto dilution over the past couple of years. Auto dilution is essentially a very powerful technique that will allow customers to queue their samples up on an auto sampler and let it run unattended. ​

“Auto dilution will also dilute prescriptively so if you have a set of food samples that you take directly from the microwave you can put them in the auto sampler and the auto dilution unit will dilute it tenfold so it eliminates that manual interaction. ​

“You can set up calibrations, it can also auto dilute intelligently if it is a sample that is over range, so beyond the calibration, or if a sample is very high in matrix. So if it is an unknown sample and it is exceptionally high compared to other samples it may cause some internal standard suppression, the auto dilution system and software will recognise that and auto dilute the sample and run it again.” ​