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BACKGROUND When using inductively coupled plasma-mass spectrometry (ICP-MS) to analyze soil, the zirconium hydroxide, molybdenum oxide, and tin isotopes can cause serious interference on cadmium, which makes it difficult to accurately determine cadmium in soil samples. OBJECTIVES To develop a method for accurate determination of Cd in soil samples. METHODS ICP-MS/MS was used, and 111Cd without isobaric interference was selected as the analysis line. In MS/MS mode, the oxygen introduced into the collision reaction cell can be reacted with 111Zr16O1H+, 111Mo16O+, inducing electron transfer, dehydrogenation, oxygenation and other reactions to inhibit the overlapping interference of these polyatomic ions on 111Cd. RESULTS Oxygen flow was the key factor in this method. 0.45mL/min oxygen flow can reduce oxide interference to less than 0.005μg/L when zirconium concentration was lower than 2000μg/L and molybdenum concentration was below 1000μg/L. The method has been verified by the national reference materials. The relative error of the measured value and recognized value of the 11 national reference materials was within ±7%, and the relative standard deviation (n=12) of three soil reference materials was less than 5%. CONCLUSIONS Triple quadrupole ICP-MS oxygen reaction mode can eliminate Zr and Mo polyatomic ion interference on Cd, and this method can be used for the determination of trace Cd in soil samples.

Microwave Digestion-Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS/MS) was used to determine sulfur in crop samples, and a high sensitivity sulfur detection method in crop samples was provided. The measurement mode, interference elimination effect, linear range, detection limit and accuracy of the method were tested. The results show that the MS/MS oxygen mode can effectively eliminate the mass spectrum interference of sulfur, the method has high sensitivity, the detection limit of the method reaches 1.8 µg/g, and the sample with sulfur content below 2% can be directly analyzed by the method. The method was verified by national standard material, and the measured values were within the range of nominal value. It can be used as a new detection method for sulfur element analysis in crop samples.

The quality of regional geochemical survey samples is currently estimated indirectly by internal and external laboratory quality control. The method described here effectively improves the quality of geochemical samples. However, the improvement of the method is limited when the contents of the actual samples and external quality control samples have large differences. Since most elements are in accord with a normal distribution in a regional geochemical survey sample, a comparison was made between the real and standard normal distribution of the elements, which passed the normal distribution test and gave an estimate of the quality by using a comparison of the real and standard graph′s superposition using SPSS and Excel software. This method was directly applied to estimate the quality of analysis data for geochemical survey samples in Jiangxi province. The result of the normal distribution test indicated that the analysis data of the trace elements need a logarithmic conversion before the normal distribution can be studied. The quality evaluation method in this paper was not suitable for Ti, W and Cr etc in this area. The overlap ratios of 18 elements such as Co, Hg and Ga were more than 0.9. The overlap ratios of CaO and Na2O were less than 0.9. The results of the actual samples indicated that the detection limits need to be reduced in order to improve the analysis qualities of CaO and Na2O. It was a valuable attempt to directly evaluate the quality of analysis data for regional geochemical survey samples by using the method reported in this paper, which was a reference and supplement for the current methods of quality evaluation.

GaAs nanowires (NWs) are grown on GaAs (311)B substrates by gold assisted molecular beam epitaxy technology. Combined scanning and transmission electron microscopy analyses, the crystallographic orientations of NWs are studied. It is found that crystallographic orientations of NWs are closely related to their crystal structures: NWs of zinc blende structure grow along 〈001〉 directions and NWs of wurtzite structure grow along 〈0001〉 directions. The influence of impinging Ga flux on morphology and crystal structure of the NWs is also discussed. It is observed that NWs prefer to grow along zinc blende 〈001〉 directions at lower Ga flux, while NWs tend to grow along the wurtzite 〈0001〉 directions with only a small portion along the zinc blende ?001? direction at a higher Ga flux. The control of crystal structure and orientation of NWs can be achieved effectively by changing the Ga flux. [ABSTRACT FROM AUTHOR]

We investigated the quantum dots-templated growth of a (0001) GaN film on a c-plane sapphire substrate. The growth was carried out in a radio-frequency molecular beam epitaxy system. The enlargement and coalescence of grains on the GaN quantum dots template was observed in the atom force microscopy images, as well as the more ideal surface morphology of the GaN epitaxial film on the quantum dots template compared with the one on the AlN buffer. The Ga polarity was confirmed by the reflected high energy electron diffraction patterns and the Raman spectra. The significant strain relaxation in the quantum dots-templated GaN film was calculated based on the Raman spectra and the X-ray rocking curves. Meanwhile, the threading dislocation density in the quantum dots-templated film was estimated to be 7.1 × 107 cm-2, which was significantly suppressed compared with that of the AlN-buffered GaN film. The roomtemperature Hall measurement showed an electron mobility of up to 1860 cm2/V . s in the two-dimensional electron gas at the interface of the Al0.25Ga0.75N/GaN heterojunction. [ABSTRACT FROM AUTHOR]