16 Moreover, the detector is calibrated with known quantities of the elements targeted for analysis, so that it can effectively match the signals obtained from the sample to its pre-calibrated signals to allow for effective quantitation. It generally uses either a photomultiplier tube-type mechanism or a charge coupled device (CCD).
This detector, after correlating the wavelengths of light to the identity of the elements, is used to determine the final sample composition. The configuration of the system into either an axial configuration 13 (where the plasma is viewed head-on) or radial configuration (where the plasma is viewed from the side) has additional effects on the ability to observe the target signals: although generally radial configurations show improved detection capabilities, 14 advances in axial configurations’ detection capabilities have recently been reported. To address this issue, the wavelengths corresponding to each element are separated, generally via an optical grating device, 12 so that each element can be individually detected.
Although each individual element absorbs and emits light at a characteristic wavelength, signals from multiple elements often overlap, leading to significant challenges in interpreting the results obtained. 11 Following successful aerosolization, interactions between the high energy plasma and the sample result in degradation of the sample to its individual elements, each of which has a characteristic optical signal that can be detected spectroscopically (see part d). Aerosolizing of the sample generally occurs through the use of a nebulizer, 10 and also needs a mechanism for sample transport from the injection port to the point of aerosolization. Interactions between the plasma matrix and the sample are critical for successful analysis, and obtaining those interactions requires the sample to be aerosolized. It is generated through the use of a high-power radio frequency signal 8 or through microwave irradiation, 9 which causes the gas to ionize to form electrons and other charged species within the plasma matrix.
This plasma is most commonly composed of argon, 5 although nitrogen gas 6 and mixed gas compositions 7 have also been reported.
0 kommentar(er)
