Agilent Japan application scientist Kazuhiro et al. used prepFAST-S and 8900s ICP-QQQ of ESI Company of the United States to analyze ultrapure water and hydrogen peroxide in a fully automated standard addition method (MSA), achieving ppq to ppt levels of concentration The ability to detect trace elements (including B, Si, P, S and other non-metals).
The article particularly emphasizes the versatility of the method. Table 1 is an almost complete reproduction of the method parameters in the Agilent 8900s Electronic Grade Hydrogen Peroxide Application Note (5991-7701EN). It can be seen that such a “straightforward” method transfer reflects that the performance difference between each 8900s is very small. Even if analysts do not have much experience, they can still obtain satisfactory results by relying on automated sampling devices and mature method transfer. analysis results.
Correction: Ext2 voltage in Soft-O2 mode is -120V
Let’s compare these method parameters carefully. The Cool-NH3-soft of 8900s in this article is very similar to the Cool-NH3 of 8800s in the previous article, which shows that the method routes of the two modes are basically the same. But the Cool-NH3 of 8900s is different: the extraction lens 1 is set to a negative voltage (-150V) and the Q1 entrance lens is set to a positive voltage (-15V), both of which increase the ion transmittance.
Compared with the 8800s, the Cool-NH3 of the 8900s adopts a higher reaction gas flow rate to reduce the background first, so choosing to use the negative bias voltage of the lens to adjust the ion transmittance can counteract the adverse effect of the overall signal attenuation caused by the CRC drop background. In Figure 1, Ca chooses Cool-NH3-soft, while Fe chooses Cool-NH3. The essence is that high sensitivity is preferred under the premise that the background meets trace analysis. The side also shows that the determination of ultra-trace Ca needs to maintain a lower background than Fe.
The above situation also occurs in O2, and the difference with Soft-O2 is in the lens voltage. The voltage settings of the extraction lens 2 (Ext2) and the Omg deflection lens (OmgB) are biased so that elemental background is reduced for better detectability. In Figure 2, Soft-O2 is selected for the determination of As, and O2 is selected for the determination of P. This is still the standard for measuring the signal-to-background ratio, that is, under the premise of low background, select high sensitivity.
Summarize
In Agilent ICP-MS semiconductor methods, CRC has outstanding background reduction ability, but it needs to be used with caution. In addition, through the optimization of IGT conditions, if the lens adopts soft extraction (positive bias voltage changes the ion transmission transmittance), the background can also be reduced; while hard extraction (negative voltage) can improve the overall sensitivity. Based on the above situation, analysts need to comprehensively use techniques to reduce background and improve sensitivity, and adapt to different plasma conditions. Of course, “common semiconductor samples” can be practiced, experienced and accumulated experience under the guidance of the manufacturer’s engineers, but for “challenging samples”, learning to choose is the most “difficult” part of method development.