ICP-OES Torch Melt - Possible Cause

I encounter an incident recently in our lab where the ICP torch in the 5100 OES instrument melted after only having the instrument on for ~90 min to do a quick Read of one pure known standard solution. The instrument and plasma turn on and extinguished okay without issue but the next day after opening the Torch chamber I seen the top of the torch had melted down to just above the RF coil. What was even more surprising is that the instrument hadn't registered any warning or errors from the torch melting.

After having an engineer call out he ruled out the following possible causes:

1. RF coil contact with torch

2. Insufficient coil / torch cooling - chiller unit operating correctly with no coolant flow obstruction.

3. Exhaust / extraction system

 

The engineer stated they had never seen this type of torch melt down pattern before so couldn't assign a definitive cause especially when the instrument software hadn't registered any errors and the instrument seemed to be operating within its parameters during their inspection. However he did notice that the seal on the OneNeb nebuliser in the spray chamber wasn't on correctly so small amount of Oxygen could have gotten into the torch and caused the plasma to burn hotter than normal or not cool down as quickly during the extinguishing sequence.

 

My own thoughts on this was since we clean the torch every week by soaking in aqua regia that over time the strong solution has been weakening the quartz torch but I can't find any information to support this.

 

Has anyone else experienced something similar to this in their ICP experience?

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  • Hello,

     

    It would really help if you could share some more information on the gas flows and instrument parameters (such as the RF power) being used.
    And could you also give some background on the sample types you're running and how you prepare them.
    Torch melts can occur if the wrong combination of conditions are used, or if there is a nebulizer blockage.
    For example, using high RF power and very low plasma gas flow can contribute to short torch life or a potential melt.
    A partial blockage of the nebulizer and/or the injector in the torch could also contribute to a torch melt due to overheating. Have you checked the nebulizer for any blockage?

     

    Cheers Eric

  • Hi Eric,

     

    No nebuliser blockage is registering. Currently I'm involved in method development work on the OES. The lab plans to use the instrument for analysis of biological samples, i.e. blood serum, for the presence of macro, meso & trace elements - Na, P, K, Ca, Mg, Fe, Zn. The samples wont be acid digested but instead its hoped to dilute out the physical matrix effect through development of a dilute and shoot method. The diluent solution used for the calibration standard and sample make-up will be a mixture of 1% HNO3 & 0.01% Triton X.

     

    However we are just at the initial stages of the development looking at wavelength selection and using the 'Timescan' & 'Read' functions to determine wavelength performance and optimise the emission intensity / analyte signal by altering the Measurement Conditions. We are only using known concentration standards from pure stocks ranging from 0.01 ppm to 0.5 ppm. The measurement conditions which were in use during the torch meltdown are given below.

     

    Coincidentally a similar instance has occurred again today whereby the torch has again melted but this time the melt is not as severe and seems to be only on one side as you can see from the pictures below. Having contacted Agilent technical services the agent advised that when the torch is cleaned by soaking in aqua regia, removed, rinsed and left to air dry that if placed lying down that the drying on the torch isn't uniform and can produce 'salt hot spots' which cause the torch to melt when in contact with the high temperature plasma. So they recommended drying the torch standing upright. However I'm not sure that this is the case I've experienced as we aren't running any high salt samples at the moment only pure standard solutions which take 3-4 only daily. Plus I've also worked with ICP-MS and never had any torch drying issues or melts.

     

    Any thoughts on likely causes are welcome.

     

     

     

  • Hello,
    I would like to reconfirm the gas flows.

     

    Plasma Flow: 8L/min

    Aux Flow: 0L/min

     

    Is this correct?

     

    Cheers

    Daniel

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