5110 SVDV SP7 Valve Question

There is an SP7 switching valve on our 5110 ICP-OES  The first set of triplicate aspirations of Std always ride really close to the precision limit of 2%RSD and then std#2 and Std3 are typical 0.5 or less.  (ISTD Method) All of these standards are in the PPM range and nowhere close to the LOD for the elements we are monitoring.  We could run the method 10x in one day and this happens every single time.   I am wondering if the sample loop is not getting flushed enough with standard on the first set of aspirations. Individual aspirations of the first std appear to climb from the first to the third aspiration but usually at about 2%+/-.5%  I even switched the order of the order of the stds and when I aspirate the highest concentration first it fails or comes close to failing and the standards that follow all drop to 0.5% RSD or below including the low std that used to be std1 in this case.

Does the sample loop need rinsed with sample longer or is it possible that the valve is having an issue?

Jack

  • Hi

    Is nebulizer is giving proper aerosol in spray chamber?

    Check may be nebulizer is partially blocked.

  • I don't believe the neb to be blocked because %RSD for all the stds and samples would be an issue then.  After the first std everything falls nicely to below 0.5% RSD or lower.  Only for the first std, regardless of concentration does this happen.  Like the valve is not rinsed or wetted properly.

  • You said that facing problem with only one standatd and that std is concentrsted, even after changing the order also so are there any possibility that you can dilute that std then run to see again problem or not.

    If still problem then increase rinse time then see.

  • You could try increasing the valve uptake delay and/or stabilization time.

    You could also manually fill the sample loop with rinse solution using the controls on the instrument 'Status' tab before beginning analysis to test if having the sample loop / valve wetted before analysis makes a difference 

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