Determination Of Micro-or Trace Elements In Biological, Chinese Medicinal Herb And Water Samples By ICP-MS/OES

Inductively coupled plasma mass spectrometry (ICP-MS) is anelemental measurement technology developed in the 1980s. It has been 27years since the first milestone article was published in 1980. ICP-MS has nowbecome an acknowledged powerful technique for the measurement of traceelement and isotope, with a wide spectrum of applications. Its analyticalfeatures include high sensitivity, extremely low limit of detection (10^-15～10^-12),extremely wide linear dynamic range (10⁸～10⁹), simple lines, fewinterferences, rapid analysis, and capabilities for multi-element and isotoperatio determination. However, there are difficulties in determininghard-to-ionize elements, such as arsenic, selenium and mercury, by ICP-MS.There are many ways to improve the detection sensitivity in the analyticalatomic spectrometry, and one of the commonly used techniques is chemicalvapor generation (CVG). CVG is a process in which volatile or semi-volatileanalyte species can be generated from nonvolatile species, and swept intoatomic spectrometer for enhanced detection capability. In this work, CVG wascoupled with ICP-MS for the determination of mercury in water samples.Chemical reagents such as SnCI2, KBH₄, Vis photo-HCOOH, or UV photo-HCOOH were used as a reductant for the CVG. These CVG methods were compared in terms of sensitivity, limit of detection and anti-interferencecapability. They were also compared with conventional ICP-MS.Firstly, the working parameters of ICP-MS and the concentrations ofreagents for the CVGs were optimized. Under the optimized experimentalconditions, the calibration curves were constructed, and the sensitivity andlimits of detection calculated. It was found that the most sensitive method wasthe CVG-ICP-MS using KBH₄ as a reductant, with a sensitivity of 2.5×10⁵ Lμg^-1, indicating that the strongest reducing ability of KBH₄. The LODs of SnCl₂,Vis Photo-HCOOH, UV photo-HCOOH were 0.002, 0.001 and 0.003μg/L,respectively. However, the LOD of KBH₄ system was 0.01μg/L, probably dueto the large amount of hydrogen gas generated during the CVG processwhich causes the instability of the ICP. The most stable system isconventional ICP-MS method (i.e., without CVG), with the lowest sensitivitybut an LOD of 0.05μg/L close to that of the KBH₄ CVG method. Anyway, theintroduction of CVG method improved method LODs and anti-interferencecapability. Among the four CVG-ICP-MS methods investigated in this work,those using SnCl₂ or Vis photo-HCOOH as reductants were stabler than thoseusing KBH₄ or UV photo-HCOOH as reductants. The capability of photolyticdecomposition of HCOOH is stronger in the case of UV than the visible, so thebetter sensitivity. But the use of the coiled quartz pipe decreases the mercurysignal stability, so the LOD with the UV-CVG is not better than that with visiblephoto-CVG. It was also found in the experiment that the memory effect withthe KBH₄ or SnCl₂ system was more serious than that with the HCOOHsystem or conventional ICP-MS method. So, longer wash time would beneeded in the KBH₄ or SnCl₂ system. This may be caused by the design ofthe sample introduction system.In this work, the interference effect of Zn²⁺, Cu²⁺, Fe³⁺, Co²⁺, Ni²⁺ andPb²⁺ on the CVG-ICP-MS determination of mercury was also investigated. Itwas found that for all the CVGs there is no significant interference from thesecoexisting ions with concentrations as high as 1000μg L^-1. Under the optimized experimental conditions, the accuracy of the proposed methodswas validated by analysis of a certified reference water sample and twospiked water samples. Good agreement between the measured value and thecertified value was obtained by using KBH₄, SnCl₂ or HCOOH CVG. Therecovery of spiked water samples was between 98-107%. In conclusion, UVphoto-CVG-ICP-MS with HCOOH as a reductant is the best for its superiordetectability, green nature, and almost freedom of interference.With the rapid development of environment science and life science, theresearch of biological sample analysis by ICP-MS has been promoted greatly.The content of target elements in this kind of samples is usually low, and theamount of samples is often little. So, highly sensitive analytical method isneeded. Compared with other elemental analysis techniques, the advantageof ICP-MS is obvious. The giant panda is a national treasure of our country,but at present, most of them live in the mountain area of almost only Sichuanprovince, the some others live in Gansu and Shanxi provinces. Giant panda'sfood structure is exclusive, and their reproduction ability is poor. With theconstant enlargement of the human life area, the habitat of the giant panda isreduced, and they have to shrink back to the high area above sea level. Thecolony is smaller and smaller, and it is more and more difficult for giant pandato survive and multiply. The contents of trace elements in the giant panda arerelated to its reproducing closely, so the determination of trace elements of thegiant panda is extremely important. The formal reports about thedetermination methodology of trace elements in their bone samples have notbeen seen yet. ICP-MS was applied for the determination of micro-and traceelements in panda panda bone in this work.Micro-and trace elements in the rib sample of a giant panda dead ofsome unknown reasons were determined by ICP-MS. Two sample digestionmethods were tested, acid digestion and microwave digestion. Under theoptimized instrument conditions, the calibration curves of As, Cd, Hg and Pb were determined. The limits of detection of all the elements except As are low.This is mainly because of the use of HCIO₄ in the sample preparation, whichinfluences the determination of low content of As. The calibration method wasused to determine As, Cd, Hg and Pb in the rib sample of the giant panda,with the recoveries of these elements calculated. The relatively standarddeviation of 3 measurements is in the range of 1%-4%. The recovery of themicrowave digestion method is in the range of 94-105%, that of acid digestionmethod 83-114%. Ca, Na, Mg, Cu, Al and Fe were also determined byICP-OES. In order to verify the accuracy of the method further, we utilizedICP-OES to determine As in the samples and HG-AFS for As speciationanalysis. Good agreement between the measured values determined byICP-MS and ICP-OES was obtained. The experimental results showed therewas no significant difference between the two kinds of digestion methods.However, less time and reagent were needed in the microwave digestionmethod, so it is a greener digestion method. The method is simple, fast, andaccurate.To study the trace elements in the Chinese medicinal herb is animportant topic in modern medical research and life sciences. It providesscientific basis to pharmacology, toxicity and traditional Chinese medicinequality control. Because of the harm of heavy metals to human health, it isimpotant to accurately determine heavy metals in traditional Chinesemedicine. The composition of the traditional Chinese herbal medicine iscomplicated, and the content of trace elements is low, so the analyticalmethod for the determination of trace elements in the medicinal herb shouldbe sensitive and selective. More and more attention has been paid to ICP-MSmethod owing to its remarkable advantages. In this work, As, Cd, Hg and Pbin 27 medicinal herbs from four different provinces were accuratelydetermined by ICP-MS after microwave digestion. The cluster analysismethod was applied to analyze the analytical data in term of As, Cd, Hg and Pb contents. The result shows that the contents of these elements in theseherbs have significant difference. This work provides some basic data forquality control and producing area identification of ther medicinal herbs.