Application of a Rapid Sequential Inductively Coupled Plasma Optical Emission Spectrometric Method for the Analysis of Materials With Linerich Emission Spectra by Different Means of Sample Introduction D. MERTENa , J. A. C. BROEKAERT* a AND A. LE MARCHAND aUniversity of Dortmund, Department of Chemistry, D-44221 Dortmund, Germany aISA Jobin Yvon, 16–18 Rue du canal, F-91165 L ongjumeau Cedex, France Rapid sequential atomic emission spectrometry with the respect a proper line selection is required and rapid sequential spectrometry to a certain extent can oVer possibilities here.IMAGE system (ISA Jobin Yvon, Longjumeau, France) in combination with an inductively coupled plasma is described. This is the case when rapid sequential emission spectrometry in an ultra-rapid slew-scan mode is performed, as it is possible As analytical figures of merit the precision, limits of detection, spectral resolution and linear dynamic range are discussed in with the IMAGE system (ISA Jobin Yvon, Longjumeau, France). comparison with those of conventional sequential spectrometry.The IMAGE system is shown to allow a registration of the In the work presented, the application of a JY 24 spectrometer equipped with the IMAGE system for sequential emission spectrum in the wavelength range 165–750 nm in less than 2 min (compared with several hours when applying ICP atomic emission spectrometry to the analysis of samples with a linerich Zr matrix is described for diVerent means of conventional slew times and scanning at similarly high resolution) without any loss of spectral resolution.Thus, sample introduction. Results for the determination of Fe, Co, Mn and Ni in the presence of Zr as sample matrix for both spectral interferences can easily be detected, suitable lines for quantitative determinations can be selected and standard aqueous solutions and in work with slurries of ZrO2 ceramic powders are discussed. Figures of merit are compared with solutions used for calibration could even be adapted ‘on-line’ to the matrix of the sample to be analyzed.However, a those obtained by sequential ICP-OES with conventional spectrometry. Further, the possibilities for a direct survey deterioration in the detection limits by a factor of 3–10 has to be taken into account. Results are given for several means of analysis for ZrO2 powders by ICP-OES combined with laser ablation are discussed and compared with qualitative analysis sample introduction.It is shown for a solution of 2 mg l-1 Fe in the presence of a 5000-fold excess of Zr that the method making use of multi-channel detectors such as an SCD.1 can be used for accurate quantitative determinations at the minor and trace element concentration level in work with EXPERIMENTAL solutions and slurries. For laser ablation coupled to ICP-OES of briquetted ZrO2 ceramic powders, the potential for The equipment consists of a sequential ICP-OES instrument qualitative multi-element survey analysis from a large number (JY 24, ISA Jobin Yvon) utilizing a 0.64 m monochromator of laser impacts is shown.with a grating having 2400 grooves mm-1 and the IMAGE data acquisition system. The widths of the entrance and exit Keywords: Inductively coupled plasma; atomic emission slits are 30 and 20 mm, respectively. The IMAGE system spectrometry; laser ablation; slurry nebulization; fast scanning consists of high-speed electronics as well as a HDD (High acquisition; zirconium matrix Dynamic Detector, ISA Jobin Yvon) measurement system including powerful software for data acquisition and manipulation.In ICP-OES spectral interferences limit both the accuracy The instrumental parameters used for ICP-OES are given and the precision of trace analysis, especially for samples in Table 1. The emission spectra in the range from 165 to with matrices emitting linerich atomic emission spectra. Simultaneous spectrometers allow rapid analysis and high precision measurements when internal standardization is used.Table 1 Instrumental parameters However, the flexibility in line selection is very low and spectral interferences cannot easily be detected. Multi-channel detectors Sequential ICP-OES instrument, ICP-OES such as charge coupled devices (CCDs), charge injection devices JY 24 (ISA Jobin Yvon, Longjumeau, France) (CIDs) and segmental charge coupled devices (SCDs) make it Generator 800 W at 40.68 MHz possible to acquire parts of the emission spectrum of a sample Monochromator 0.64 m Czerny–Turner mounting simultaneously, but the covered wavelength range, the grating: 2400 grooves mm-1 obtainable spectral resolution and the dynamic range are Nebulizer for aqueous solutions Cross-flow (ISA Jobin Yvon) compromised. In contrast, conventional sequential spec- Nebulizer for slurries G.M.K.(Labtest, Ratingen, trometers oVer high flexibility and excellent detection limits. Germany) Peristaltic pump Perimax 12 (Spetec, Munich, Nevertheless, they are slow and, in particular, when with Germany) conventional sequential spectrometers the intensities of the Laser ablation system LSX-100 (FMS CETAC, spectral background are measured at arbitrary wavelengths Freudeuberg, Germany), and when the resolution of the spectrometer is low, spectral Nd–YAG (266 nm) interferences lead to systematic errors.For progress in this Journal of Analytical Atomic Spectrometry, December 1997, Vol. 12 (1387–1390) 1387750 nm are recorded in about 2 min. In a second step a which are recorded with the JY 24 spectrometer in the second order. wavelength calibration is carried out using several reference lines and the spectrum is converted digitally to make the In Fig. 1(b) the profile recorded for the Ni I 361.939 nm line in the first order is shown. The values for the full-width at individual intensity signals accessible for the software.The error in wavelength calibration is typically in the range half-maximum measured for these profiles, the physical linewidths and the resulting values for the spectral resolution are of only a few pm. Further, it is possible for narrow wavelength ranges to shift manually the measured peaks to the theoretical listed in Table 2. As can be seen from these results the spectral resolution in the second order is a factor of 2 better than in positions that are indicated by a database of atomic emission lines included in the software.the first order. These values also show that the spectral resolution of ICP-OES with the IMAGE approach is as good The linear dynamic range comprises six orders of magnitude. This is achieved by automatically adapting the photomultiplier as the resolution obtained with conventional sequential ICPOES instruments with medium resolution (7–11 pm).3 Thus, it voltage depending on the intensity of the signal. The scanning step for the grating used is 1.9 pm in the first order (305– can be concluded that no distortion in the peak shape as a result of detector hysteresis, which could influence the spectral 750 nm) and 0.95 pm in the second order (165–305 nm).The integration time per point is 0.5 ms. Grams/386 software resolution, is obtained. (Galactic Industries, Salem, USA) was used to process the data. Precision and limits of detection RESULTS AND DISCUSSION In Table 3 the detection limits obtained when using the IMAGE approach are compared with those obtained when Analytical Figures of Merit the same spectrometer is used in the conventional way of The achievable spectral resolution, the precision and the sequential analysis.It was found that the detection limits detection limits are important analytical figures of merit, which obtained with IMAGE (based on the standard deviations in well describe the spectrometric features of the equipment used the intensity of four replicates) are higher than those obtained in combination with the IMAGE system. This allows a comin the conventional mode of operation.This is understandable parison of the capabilities of the IMAGE approach with those from the fact that the relative standard deviations of the of conventional sequential spectrometers using integration intensity signals obtainable when using the same spectrometer times of a few hundred ms. in the conventional way are about 1% whereas those obtainable with the IMAGE system are much higher.However, the IMAGE system allows a registration of the emission spectrum Spectral resolution in the wavelength range 165–750 nm in less than 2 min, com- From the values of the full-width at half-maximum Dlexp of pared with a few hours with the conventional way of scanning recorded line profiles and tabulated physical widths Dlphys for using integration times per data step of 0.3 s with slew times atomic emission lines in ICP-OES, the instrumental resolution of 200 steps min-1, and without any loss of resolution.Dlinstr can be calculated.2 Dl2instr=Dl2exp-Dl2phys (1) Survey Analysis In Fig. 1(a) the profile recorded for the Fe II 239.562 nm line One of the major advantages of the IMAGE system is that is shown. The full-width at half-maximum (7.0 pm) is typical within 2 min the emission spectrum in the complete wavelength for atomic emission lines in the wavelength range 165–305 nm range 165–750 nm can be recorded with high resolution (about 7 pm in the second order and about 14 pm in the first order, Table 2) and with a high dynamic range (6 decades).Even for materials with linerich spectra, such as metals and advanced ceramic materials such as ZrO2-based ceramics, spectral interferences can easily be evaluated. This is of prime importance for the choice of suitable analytical lines for the analysis of these materials by atomic emission spectrometry. In Figs. 2 and 3 the spectra obtained with ICP-OES using diVerent methods for sample introduction of ZrO2 ceramics Table 2 Calculation of the spectral bandwidth Dlinstr2 Line/nm Dlphys/pm2 Dlexp/pm Dlinstr/pm Fe II 239.562 2.1 7.0 6.7 Ni I 361.939 2.7 14.6 14.4 Table 3 Detection limits (cL) and relative standard deviations (RSD) with the IMAGE approach as compared with conventional sequential spectrometry for the analysis of aqueous solutions by ICP-OES (four replicates) Conventional IMAGE RSD Line/nm cL/mg l-1 cL/mg l-1 (%) Fe II 238.204 6.3 38 1.3 Fe II 259.940 14 41 3.4 Co II 228.616 3.3 60 3.5 Mn II 257.610 4.3 16 13 Fig. 1 Profiles recorded for the lines Fe II 239.562 nm (a) and Ni I Mn II 259.373 15 22 16 361.939 nm (b) in ICP-OES using the JY 24 spectrometer in combi- Ni II 231.604 33 94 0.2 nation with the IMAGE system. 1388 Journal of Analytical Atomic Spectrometry, December 1997, Vol. 12Fig. 4 Calibration graph and its 90% confidence intervals for the Fe II 239.562 nm line in ICP-OES of aqueous solutions containing Fe Fig. 2 ICP atomic emission spectrum in the wavelength range 165– only by using the IMAGE approach. 750 nm, obtained for a ZrO2 powder by laser ablation (Powder 2, Cerasiv, Plochingen, Germany). Fig. 3 ICP atomic emission spectra for two ZrO2 powders (Cerasiv) obtained with slurry nebulization (Powder 2: with Y and Powder 3: without Y). are shown. In Fig. 2 the ICP emission spectrum for a ZrO2 powder, that was introduced into the ICP by means of laser ablation, is shown.The powder was pressed in a sample holder, the ablated amount of material was introduced into the ICP by means of a 0.8 l min-1 carrier gas flow and the emission spectrum was recorded. From this spectrum it can be seen that Fig. 5 ICP atomic emission spectra for a 10 g l-1 Zr solution with Zr has an extremely linerich emission spectrum with atomic and without 2 mg l-1 Fe in the vicinity of the Fe II 234.349 nm (a) spectral lines of largely varying intensities and that a qualitative and Fe II 239.562 nm (b) lines obtained with the IMAGE approach. analysis is possible.For the analysis of powders used for the production of advanced ceramics, slurry nebulization is commonly used. In excess of Zr. In particular, the influence of spectral interferences this technique the ceramic powder is suspended in water and on the accuracy of the trace determination can be evaluated. the slurry is directly aspirated and nebulized by a Babington On the basis of calibration graphs such as that for Fe II nebulizer.In Fig. 3 part of the emission spectrum in the vicinity 239.562 nm (Fig. 4), quantitative determinations can be carried of one of the most sensitive atomic emission lines of Y is out. The calibration graphs for spectral data acquisition with shown. It is obvious that by the use of the IMAGE system the the IMAGE approach were found to be linear up to 0.5 g l-1. information required for qualitative analyses as well as for Both the calibration and the analysis are based on four quantitative determinations can be obtained within a very replicates.The location of the background correction was set short time. For example, it can be concluded that from the manually to detect and overcome spectral interferences in the samples investigated only Powder 2 contains a significant linerich spectra. amount of Y, a point that is technologically relevant, as the In Fig. 5 the superimposed spectra for a solution of 10 g l-1 addition of oxides of Ca, Y or Mg is necessary for realizing a Zr and for a 10 g l-1 Zr solution containing additionally high temperature stability of ZrO2-based ceramics.The results 2 mg l-1 Fe (200 mg Fe per gram of Zr) in a spectral window in Fig. 3 thus demonstrate that a rapid identification of a given around the Fe II 234.349 nm line [Fig. 5(a)] and around the ZrO2 powder with respect to its Y content is possible with the Fe II 239.562 nm line [Fig. 5(b)] are shown. aid of the IMAGE approach. From the spectra it can be seen that the Fe II 234.349 nm line is strongly interfered with a Zr line, whereas for Fe II 239.562 nm no interferences are present. The influence of Quantitative Determinations spectral interferences on the accuracy of quantitative determinations is clearly shown by the recovery found for Fe in the With the aid of the approach described, quantitative determinations are simplified, since spectral interferences can presence of a Zr matrix as determined by a calibration with aqueous solutions containing Fe only.The results obtained for easily be detected and corrected for. This is shown by the determination of 2 mg l-1 Fe in the presence of a 5000-fold diVerent Fe lines are given in Table 4 where the interfered Journal of Analytical Atomic Spectrometry, December 1997, Vol. 12 1389Table 4 Quantitative determination of 2 mg l-1 Fe in the presence of within a short time and standard solutions for calibration can 10 g l-1 Zr be adapted eventually by automated dilutors (‘on-line’) to the matrix of the sample to be analyzed.With respect to the Line/nm Concentration/mg l-1 Interference recovery of Fe in the presence of an excess of Zr, it was shown Fe II 234.349 6.1±0.7 + that with the IMAGE system accurate quantitative determi- Fe II 239.562 2.0±0.4 - nations are possible as a result of the ease of selection of Fe II 238.204 2.4±0.5 - interference-free atomic emission lines.Further, it was shown Fe II 240.488 2.6±0.4 - that for diVerent types of sample introduction systems yielding steady-state signals, such as slurry nebulization and multiimpact laser ablation, data for a rapid survey, as required in Fe II 234.349 nm line is marked. Indeed, for the interfered Fe II 234.349 nm line the concentration found is much too high, qualitative analysis, can be collected. Thus, rapid sequential ICP atomic emission spectrometry is an interesting alternative whereas for the other lines used the concentrations found are in good agreement with the concentration of Fe provided in to multi-channel detectors.Nevertheless, the short integration time leads to a the solutions. deterioration of the precision as compared with conventional systems and, therefore, also to higher detection limits. CONCLUSIONS It has been shown that with rapid sequential spectrometry using the IMAGE approach the identification of spectral REFERENCES interferences for linerich ICP atomic emission spectra is easily 1 Rivier, C., and Mermet, J. M., Appl. Spectrosc., 1996, 50, 959. possible, which is of paramount importance for avoiding 2 Boumans, P. W. J. M., and Vrakking, J. J. A. M., Spectrochim. systematic errors. All line intensities within the wavelength Acta, Part B, 1986, 41, 1235. range 165–750 nm can be recorded within 2 min without any 3 Mermet, J. M., and Poussel, E., Appl. Spectrosc., 1995, 49, 12A. loss of resolution compared with conventional sequential ICPOES. Thus, the qualitative detection of metals and non-metals Paper 7/03388E is possible within a single spectrum and the choice of lines is ReceivedMay 16, 1997 not limited, due to the completely covered wavelength range. Accepted September 18, 1997 Accordingly, for qualitative analysis the data can be acquired 1390 Journal of Analytical Atomic Spectrometry, December 1997, Vol. 12