ABSTRACT
Line scanning quantitative analysis method on silicate with small laser beam ( < 15 μm) was developed using laser ablation sector field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS). Differences on signal intensity and elemental fractionation induced by different laser sampling patterns were compared. While spot ablation with small laser beam, the elemental signal intensity decreased with time significantly, and the elemental fractionation was obvious. In contrast, the elemental signal intensity by line scanning was higher and more stable and line scanning was free of elemental fractionation. Therefore, identical ablation pattern and condition should be used for the standard and the unknown sample in LA-ICP-MS quantitative analysis. A single pulse experiment was carried out to investigate the washout time when coupled to two-volume ablation cell. The result indicated that the elemental intensity decayed to the background value needed 2-3 s. The optimal parameters on SF-ICP-MS were set to reduce the effect of signal overlapping. Homogeneous sample KL2-G and titanite grains with composition zoning were analyzed by this method. Accurate element contents and element ratios indicated that fast washout time and optimal instrument parameters made it feasible to perform line scanning quantitative analysis accurately. Comparing to traditional microanalysis, line scanning quantitative analysis could reduce the laser beam size (<15 μm) and improve the spatial resolution efficiently. The potential of the technique to unveil compositional complexities in greater detail would help to improve our understanding of geochemical processes in mineral scale.
ABSTRACT
The ablated aerosols of biological matrix sample were studied using 213 nm nanosecond laser ablation system.The stable signal intensity and high sensitivity were obtained when the laser energy was 25%, the spot size was 200 μm, the scan rate was 20 μm/s, the frequency was 20 Hz and the carrier gas was 700 mL He + 700 mL Ar.Relative fractionation index of 56 elements were investigated and 31P as the internal standard element was selected under the optimized laser ablation conditions.The results showed that particle size of the biological sample was 3 μm, which was larger compared with NIST 610 sample.Element fractionation in biological sample was smaller than in glass sample, and relative fractionation index of most elements attained 1.0 ± 0.1.Element fractionation mechanism of biological sample was discussed.The possible reason why the relative fractionation index in biological sample with large particle size did not significantly increase compared to the glass sample is that the 3-μm particles entered into ICP can be atomized.On the other hand, enrichment effect for large ablation particles was relatively small.Further study of the influence factors of fractionation effect indicated that, the fractionation effect had relations with laser ablation energy, laser frequency and scan rate, negatively relation with the oxide boiling point, and positively relation with oxide bond energy and ionization energy.
ABSTRACT
Laser ablation inductively coupled plasma mass spectrometry ( LA_ICP_MS ) was applied for the determination of doping element chromium( Cr) content and distribution in Cr∶ZnSe crystals. Several different Cr∶ZnSe crystals were prepared by diffusion method as reference material to solve the problem of accurate quantization. The homogeneity of Cr in these samples was characterized by LA_ICP_MS and the concentrations achieved by inductively coupled plasma atomic emission spectrometry ( ICP_AES ) . With signal pot and line scan sampling, the present method provided effective position and content distribution information of Cr in ZnSe crystals, achieved the in situ analysis. The correlation coefficient of Cr in calibration curve was 0. 9992 and the detection limit was 0. 08 mg/kg. It could provide effective means for the distribution statistics of doping element in different growth condition crystals.
ABSTRACT
Imaging of trace metal distribution in the cadmium ( Cd) hyperaccumulator Indian mustard by laser ablation inductively coupled plasma-mass spectrometry ( LA-ICP-MS ) was typically performed using spatial resolutions of 25 μm. Indian Mustard was submitted to 50 mol/L Cd for 14 days exposure and analysed using Nd:YAG laser (213 nm) . Intensities of 13 C, 34 S, 39 K, 44 Ca, 66 Zn, 111 Cd, 65 Cu and 31 P were measured by ICP-MS to study elemental distribution. Preferential Cd accumulation in vascular bundles was observed in stem tissue, whereas Cd was mainly localized to the mesophyll and vascular cells. The high relationship between Ca and Cd distribution indicated that the two elements had a very similar pathway. In vivo analytical method developed in this work was useful to study spatial element distribution across stem samples and had great potential for applications in other areas of plant pathology research.