Inductively coupled plasma mass spectrometry (ICP-MS) is the technique of choice for multielemental determinations across a wide range of industries and applications. Almost all modern ICP-MS systems use a quadrupole mass spectrometer (QMS), combined with a collision/reaction cell (CRC) to control interferences.
ICP-QMS with CRC works well in collision mode - for example in the Agilent 7700 Series ICP/MS. The 7700 uses helium (He) cell gas and kinetic energy discrimination (KED) to filter out polyatomic interferences, providing accurate determination of most commonly-measured analytes, even in complex and variable matrices.
However, in reaction mode, ICP-QMS has a major weakness because the reaction processes in the CRC depend on the ions that enter the cell, and these ions usually vary from sample to sample. This means that reaction mode has previously been successful only for simple, known, and consistent sample matrices, such as the high-purity process chemicals used in the semiconductor industry.
And even in these simple, consistent matrices, an unexpected contaminant or high level of another analyte often leads to errors. Until now
Agilent 8800 ICP Triple Quad redefines interference removal in reaction mode
The new Agilent 8800 ICP Triple Quad (ICP-QQQ) has a unique configuration with an additional quadrupole placed before the reaction cell. The first quadruple selects the ions that enter and react in the cell, eliminating the variability and uncertainty associated with single-quad reaction mode, and delivering unmatched performance and flexibility for interference removal. The 8800 ICP-QQQ uniquely provides CRC operation with controlled reaction chemistry. Watching video http://www.youtube.com/watch?v=b9BfKcxmltI
Unique triple quad configuration preselects ions to control cell processes
The first quadrupole (Q1) of the Agilent 8800 ICP-QQQ can be set to operate either as a simple ion guide or as a bandpass filter, providing the familiarity of operating modes commonly used on single-quad ICP-MS (no gas mode, collision mode, reaction mode). Compared with ICP-QMS, the Agilent 8800 provides very high sensitivity and low random background, so detection limits are significantly improved.
Predefined operating conditions and application templates provide simple turnkey operation for a range of applications. However, for research and problem-solving, the Agilent 8800 also provides a range of powerful new acquisition modes, based on the unique ability to select the ions that enter the cell and react:
Precursor (or parent) ion scan - Q2 is set to target ion mass, while Q1 scans to select the precursor ions that enter the cell and react
- Product ion scan - Q1 is set to allow only the target precursor ion mass to enter the cell, while Q2 scans to measure the product ions formed in the cell
- MS/MS mode - Q1 and Q2 are both set to the target analyte mass. Q1 controls the ions that enter the cell to react, while Q2 rejects all ions except the analyte mass
- Mass-shift mode - Q1 is set to the analyte mass (for example 75As), controlling the ions that enter the cell to react. Q2 is set to the mass of the target reaction product ion (for example 91AsO).
- Cluster ion analysis - Mass shift analysis based on a highly reactive cell gas such as NH3, which forms cluster ions with the analytes. Creation and measurement of the target analyte cluster ion is independent of other analytes, as all potential overlapping ions are rejected using Q1.
Numerous performance benefits
The ability of the Agilent 8800 ICP Triple Quad to control the ions that enter the collision cell fundamentally changes the way reaction chemistry is performed with ICP-MS. The Agilent 8800 provides consistent reaction processes in complex and variable samples, and offers much more selective interference removal than is possible with ICP-QMS.
These features dramatically improve performance across a wide range of applications in material science, semiconductor manufacturing, clinical and life-science, and any advanced research application where problematic interferences hamper measurements with single-quadrupole ICP-MS.
The Agilent 8800 removes the limitations of reaction mode on single-quad ICP-MS, and uniquely provides:
- Selection of the ions that enter the collision cell, which controls the reaction processes in the cell to deliver reliable and consistent results in variable or complex samples.
- The combination of mass-shift mode with rejection of nontarget analytes, which cannot be done with ICP-QMS because the KED and/or bandpass settings must be set to transmit the cell-formed product ions from the collision cell to the quadrupole.
- Resolution of cluster ions that appear at the same mass but are formed from different analytes. For example in the spectrum , 48TiNH+ is overlapped by 63Cu when measured by ICP-QMS. Also, 48TiNH(NH3)3 cannot be separated from 63Cu(NH3)3 or 64ZnNH2(NH3)2, as these cluster ions also appear at mass 114, where they are also overlapped by 114Cd and 114Sn. With the Agilent 8800 ICP Triple Quad, 63Cu, 64Zn, 114Cd, and 114Sn are all rejected using Q1, allowing the Ti cluster ions to be determined free from any overlap.
Built on a proven and reliable platform
The Agilent 8800 ICP Triple Quad is unique in its configuration and performance, yet it shares many hardware components and its software platform with the market-leading Agilent 7700 Series single-quad ICP-MS. From the high-performance solid-state radio-frequency (RF) generator to the dual-mode electron multiplier with nine orders dynamic range, the 8800 utilizes technology that has been field-proven in the 7700 Series.
The 7700 Series remains the benchmark for high-performance, cost-effective ICP-QMS, delivering unmatched interference removal in He mode. The 7700 is now joined by the innovative Agilent 8800, offering unsurpassed flexibility and a range of unique and powerful modes of operation to deliver unparalleled reaction mode performance for difficult applications.
A Triple quadrupole ICP-MS system has been developed, and the principles of operation and
advantages of the proposed system with an additional quadrupole before the cell are explained.
• As an example, Ti detection which is exposed to Cu, Zn interferences were studied using O2 cellgas and the advantages of the new system were explained by comparing the experimental results of MS/MS mode and Single Quad mode.
• Ti detection as a trace impurity in sulfuric acid was studied using O2 cell gas. By adding He gas to the cell gas, sulfur-based interferences were dramatically reduced.
• As another example, Rh detection in Pb matrix which is exposed to doubly charged Pb
interference was studied using NH3 as the cell gas.
• Single Quad mode which is a compatible operation mode with the conventional cell-based ICP-MS system is explained. Its advantages (superior sensitivity for heavy mass elements) over MS/MS mode was studied and a caution which requires attention (sudden BEC increase) was explained.
Takeo Kuwabara, Noriyuki Yamada, Jun Kitamoto, Hironori Yamada and Takashi Kondo, Agilent Technologies. Inc., 9-1 Takakura-cho, Hachioji-shi, Tokyo, JAPAN