Hydride generation technique is required for trace concentration analysis of As, Sb, Bi, Hg, Ge, Se, and Te, these elements called hydride elements, these elements will be difficult to measure it in low ppb level by normal nebulization mode so, the best option to measure it in low ppb level is by hydride generation accessory.
The hydride generation accessory will attach with atomic spectroscopy instrument and will introduce the sample, acid and reducing agent such as sodium borohydride all together to the accessory, acid and reducing agent will react with sample, break down all bonds of hydride elements and release the hydride gases.
For laboratories that routinely quantify both hydride elements and non-hydride elements in samples there is too much losing time in switching between the two sample introduction systems.
Replacing the standard spray-chamber and nebulizer with a vapor generation accessory is time consuming and means first will measure non hydride elements then install VGA accessory and run hydride element.
Agilent Developed the Multimode Sample Introduction System (MSIS) which allows the sample introduction to measure in three modes, vapor generation mode, nebulization mode and Dual mode both vapor generation and nebulization modes at the same time (simultaneous).
MSIS accessory is compatible with Agilent ICP-OES and MP-AES.
Disadvantage of Vapor Generation accessory (VGA)
- Expensive compare with MSIS.
- Required suitable location in the bench beside the instrument, power socket and inert gas supply (Argon or Nitrogen).
- Losing time from switching between hydride and non-hydride elements analysis.
- After installation you need to adjust flow rate of samples and reagents.
- Long measuring and rinsing time.
- Different reagents may be required for different hydride elements.
The MSIS allows three modes of operation:
The following describes the MSIS operation modes for ICP-OES and MP-AES.
Conventional Nebulization mode
In this mode, the reductant tubing and the hydride sample tubing are blocked. As with normal ICP-OES operation, the sample aerosol is carried by argon gas as nebulizer gas into the plasma for analysis.
Vapor Generation mode
In this mode, the sample tubing to the nebulizer is blocked and the sample is pumped into the bottom of the spray-chamber. The reductant is pumped into the top of the spray-chamber and hydride generation occurs. The released hydride gaseous is carried by the argon gas from the nebulizer into the plasma for analysis.
Dual mode
In this mode, all tubing is left unblocked and both the sample aerosol and hydride gaseous are carried into the plasma by argon gas. This allows the simultaneous analysis of both hydride and non-hydride elements.
Advantages of Multi Sample Introduction System (MSIS)
- Cheap accessory like normal spray-chamber.
- The Fastest accessory for the simultaneous measurement of hydride and non-hydride elements in the same run.
- Not require suitable location in the bench, not require power or supply gas.
- In few seconds will install it, without any adjustment.
- Demonstrates excellent Detection limits and calibration linearity.
Detection limits
Improved detection limit of hydride elements to be measuring in low ppb level.
Chemistry effects
It is clear that in general, the optimum chemistry conditions for each hydride element gives the lowest detection limit.
Detection limits achieved for the same elements when analyzed together under two compromising chemistry conditions (50% HCl or 4% HCl and 1% L-Cysteine) are comparable to those achieved under optimum conditions. This shows that it is possible to achieve highly sensitive and accurate single and multi-element hydride analysis by using the MSIS with correct acid matrix selection.
Table 2 shows the detection limits achieved for non-hydride elements under the same two chemistry conditions, using an Agilent SVDV ICP-OES with the MSIS in Dual mode.
Excellent detection limits were achieved and the acid concentration was found to have little impact on the analysis of the non-hydride elements, as the MSIS detection limits were similar to those achieved using a standard sample introduction system for most elements.
This shows the ability of the MSIS to measure both hydride and non-hydride elements at the same time.
Linearity
All hydride elements showed excellent linearity up to 1000 μg/L on ICP-OES.
Conclusion
The MSIS method offers fast analysis time, high performance and simple, reliable operation.
The setup is ideal for screening large numbers of samples to meet the increasing demand for the routine determination of elements by vapor generation and standard nebulization at the same time.
The key findings of the study were
- Excellent accuracy and precision were achieved for all elements using the dual mode MSIS setup
- High sensitivity, excellent linearity and low detection limits were achieved, demonstrating the high analytical performance of the MSIS accessory even when operated in dual mode