The question is, could the 5800 detect the desired detection limit? The approximate calculated detection limits are higher then then the lowest calibration standard of 0.3 ppb but are strong depending on sample matrix, sample introduction and detection mode. So assuming that the desired detection limit is far below the lowest standard then it's not likely that the detection limits could be achieved. A possibility is to use the MSIS as sample intro for the As and Hg to achieve lower detection limits. Please reach out to the Agilent sales person in you country for information about possible buy back or MSIS capabilities.
A lot goes into low ppb analysis. You need to make sure your reagents are pure enough for this, no matter what instrument you run on. "Running into your blank", is a common issue and is magnified on an ICPMS. ICPOES customers that move to ICPMS have this issue as they are used to a level of purity and cleanliness not good enough for the sensitivity of an ICPMS. Glass volumetrics can be a source of contamination. Using metal free 50mL Class A centrifuge tubes for making standards and samples prevents contamination of trying to clean a glass volumetric flask. The glass pipettes or the plastic tips for adjustable micropipettes can be a source of contamination. Make sure you are using >18.2MOhm water. On the conditions tab you can start a time scan and monitor these wavelengths. Put the probe in just the water and let it stabilize intensities. Pull the probe out of the water for a few seconds to introduce an air bubble. When that reaches the spray chamber (you will see the mist go away for a brief time) check if the intensity drops significantly. If so, your water could be a source of contamination. Check the purity level of your acids, you may need to go to a higher purity. To test the acids, make a 1% acid and a 5% acid solution of one acid. If the 5% gives around 5 times more (some intensity could be background or from the water so close to 5x) of intensity than 1% solution, the acid is an issue. Do this for all acids/reagents you add to make sure there is no contamination. That 1% and 5% are very close in intensity.
Make sure you have the polyboost on in the software as oxygen absorbs light below 200nm, and the lower the wavelength the greater the absorbance. The elements you list above are all "hard" elements meaning their recommended analysis wavelength is below 250nm and hard to excite (or ionize for ICPMS). These wavelengths require more energy to excite the atom. Increasing the RF power to 1.4kW and optimizing SBR (Signal to Background Ratio) for those elements will help you run these low standards. To optimize, adjust the nebulizer flow. This flow serves 2 purposes, it creates your sample mist, and it provides pressure to puncture the sample into the back of the plasma. Too low of flow/pressure and the sample will pass around the plasma and not get into the hot part of the plasma ball. Too high of flow/pressure and the sample does not have enough resonance time in the plasma to get good excitation. Again on the optimize tab you can take single spectrum reads using a 1ppm standard. Start with 0.6L/min. Note the signal and background for each of your 4 wavelengths of interest. Divide signal intensity by background intensity to give SBR. Increase flow by 0.05L/min (next step would be 0.65) do the same (Excel spreadsheets help for this). You will note that both the signal and background intensities will change. We may lose signal intensity, but the background will drop faster so the ratio gets better. For example, As signal in a 1ppm may read 5000 with 1000 background intensity at 0.6L/min. Going to 0.7L/min the signal may drop to 4800 but the background may drop to 500. SBR in that example would improve from 5 to 9.6. A 4% drop in signal gave almost double the SBR. This is not real world, what you will be seeing on these are SBR around 1.5 to 2.5 so an increase from 1.5 to 1.8 is a 20% increase in SBR, if your signal drops less that 20% to get that ratio this is an improvement.
Some of these will not be possible with standard nebulization. ICPOES is not sensitive enough to run a standard at 0.6ppb of Lead. Of those you listed, Cd is the only one that should be easy to reach if I'm reading it correctly and you need to read 5ppb of Cd.
Another option is to run an ultrasonic nebulizer. USN, trace level ICP-OES, Agilent Ultrasonic Nebulizer | Agilent These give about a 10x improvement in signal. Again, you need to make sure your blank is clean as it will increase those intensities also if there is contamination in a reagent. These USN take a long time to wash out high concentrations. They are designed to give low detection limits in clean samples. If you are running higher dissolved solids, you will have long rinse times for those minerals in high concentration.
One thing of note with your list, Hg requires HCl at 2% or above to help rinse it out. So your rinse needs to have both nitric and hydrochloric acids.
We are glad this was helpful! We are sorry this was not helpful. If you still need assistance please create a community post or contact support. To help us improve, please provide any additional feedback.
For full details of how we will treat your information, please view our privacy policy.
