Simultaneous Determination of Impurity Elements in N-Methyl-2- Pyrrolidone (NMP) with Direct Injection Inductively Coupled Plasma Optical Emission Spectrometry.

An analytical method for simultaneous determination of 12 impurity elements including Mo, Cr, Zn, Pb, Ni, Mn, Fe, Cu, Ca, Al, Na and K in N-methyl-2-pyrrolidone (NMP) was established with inductively coupled plasma optical emission spectrometry (ICP-OES). The NMP without decomposing was acidized with nitric acid and analyzed directly, avoiding the risk of error introducing during sample pretreatment. The load of plasma on organic solvent was decreased by optimizing the plasma parameters and ensuring the stability of plasma. The optimized and adopted nebulizer gas flow rate was 0.4 L·min-1 and RF power was 800W. The whole signals during the sample atomization or ionization have been obtained with axially viewed ICP-OES which increases the sensitivity and decrease the detection limits. The interferences of spectral lines and background were eliminated by selecting analysis spectral lines, removing the carbon by adding oxygen and background correction method. Furthermore, standard addition method was employed to overcome the matrix effect, counteracting the ionization interference of high concerned organic matrix to easily ionizable elements. The results showed that the correlation coefficients of the calibration curve were in the range of 0.999 5～1.000 0, the detection limits were in the range of 3.8～106.4 ng·g-1, and the recoveries were in the range of 92.0%～108.0%. The relative standard deviation (RSD, n=11) were larger than 4.8% of the analytes. The method is simple without complex sample pretreatment. It is a fast analysis method with high accuracy which can satisfy completely the requirements of control analysis in mass production. This method can be applied to determine impurity elements in NMP products.

[Determination of Impurity Elements in Rosin with Inductively Coupled Plasma Mass Spectrometry].

An analytical method for the content determining of impurity elements in rosin was established. After being dissolved and diluted in ethanol, the rosin was analyzed directly with inductively coupled plasma mass spectrometry (ICP-MS). Some experiment conditions were optimized, such as the RF power, carrier gas flow, sample amount, and increase the temperature of plasma center channel, to improve the ionization efficiency. Proper oxygen concentration was added in plasma to make sure organic carbon been complete burned, resulting in carbon deposits eliminate and signal stable. Though equipment turn and isotopes selection can effectively eliminate interferences caused by oxide and doubly charged ions mass spectrums. A large amount of isobars and polyatomic ion interference were avoided. The collision reaction cell (CRC) technology was used to further eliminate the mass spectra interference, with He collision model and H2 reaction model, respectively. The results showed that detection limits of different impurity elements were within the range from 0.002 to 0.035 µg·g-1, and the recoveries of real added sample were between the range from 94.00% to 106.00%, and relative standard deviation is less than 3.34%. This method enables to detect rosin dissolved in ethanol directly and needs no special sample preparation equipment. This simple, fast and accurate approach provides us a new analysis method for the quality valuation of impurity elements in rosin.

[Study on the Detection of Trace Sulphur in Diesel with Inductively Coupled Plasma Optical Emission Spectroscopy].

The method to detect trace sulphur content in diesel with inductively coupled plasma optical emission spectrometry (ICP-OES) was established. Kerosene sample was directly diluted, and then trace sulphur content in the solution was analyzed directly with ICP-OES. High concentrations of organic solvents with high saturation vapor pressure can cause the increasing of the loading of plasma, which would interfere the determination. In order to keep the working stability of equipment, operating parameters, such as RF power, loading gas velocity, were being optimized. First, the axially-viewed technology was adopted to increase the sensitivity of determination. Second, the analysis spectral lines of sulfur are located in ultraviolet area; therefore the Ar was adopted as protective air, and increase Ar clean time to keep the pure of sight source. Third, the condensation and deposition of high concentrations of carbon could be avoided effectively by introducing O2 to plasma. Some detailed processes were used to further keep the stability of determinate signals such as: using element Y as internal standard to correct matrix effectives and compensate the errors caused by the spectral line shift, some automatic software were used to correct signal background. The results showed that the detection limits was 0.2 µg·L-1, the relative standard deviation (RSD) was in range of 1.6%~2.1%, and the recovery of the methods was in range of 97.4%~101.8%. The method has the following advantages: simple sample pretreatment, fast analyzing speed, low detection limitation, high precision and accuracy, as well as wide linear dynamic range. It can be used for rapid analysis of trace sulfur in diesel.

[Determination of Trace Impurity Elements in Food Grade Chitosan with Inductively Coupled Plasma Mass Spectrometry].

A method of inductively coupled plasma mass spectrometry (ICP-MS) was established to determinate trace impurity elements in chitosan. After dissolving in 3% citric acid and low concentration of HCl, the elements including Be, B, Na, Mg, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sn, Sb, Hg and Pb in chitosan were measured with ICP-MS directly. The addition of low concentration of HCl could effectively improve the stability of all elements, especially Hg and Sn. Dynamic reaction cell (DRC) was used to correct the interference of chlorine ion and other mass spectral interference. The matrix matching and the internal standard elements mixed solution (Sc, Y, In and Bi) had compensated the difference of sample transfer efficiency and evaporation rate of organic solvent. Under the optimum condition, the standard curve of each element exhibits linear correlation coefficient was not less than 0.999 7. The detection limit of the 20 elements was in the range of 0.6～19.0 ng·L-1 while the recovery of standard addition was 89.50%～109.00% with RSD 1.17%～4.05%. The practical sample analysis results showed that the content of impurities in food grade chitosan is very low. And the heavy metal content is extremely low and safe to eat. This method is very simple, sensitive and accurate for the determination of 20 impurity elements in the food grade chitosan.

[Determination of Heavy Metal Elements in Diatomite Filter Aid by Inductively Coupled Plasma Mass Spectrometry].

This study established a method for determining Be, Cr, Ni, As, Cd, Sb, Sn, Tl, Hg and Pb, total 10 heavy metals in diatomite filter aid. The diatomite filter aid was digested by using the mixture acid of HNO3 + HF+ H3PO4 in microwave system, 10 heavy metals elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). The interferences of mass spectrometry caused by the high silicon substrate were optimized, first the equipment parameters and isotopes of test metals were selected to eliminate these interferences, the methane was selected as reactant gas, and the mass spectral interferences were eliminated by dynamic reaction cell (DRC). Li, Sc, Y, In and Bi were selected as the internal standard elements to correct the interferences caused by matrix and the drift of sensitivity. The results show that the detection limits for analyte is in the range of 3.29-15.68 ng · L⁻¹, relative standard deviations (RSD) is less than 4.62%, and the recovery is in the range of 90.71%-107.22%. The current method has some advantages such as, high sensitivity, accurate, and precision, which can be used in diatomite filter aid quality control and safety estimations.

[Analysis of Trace Inorganic Elements in Castor Oil by Inductively Coupled Plasma Mass Spectrometry].

A method for the determination of Na, Mg, Si, P, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Hg and Pb in castor oil after direct dilution with ethanol by inductively coupled plasma mass spectrometry (ICP-MS) was established. The sample was diluted by ethanol before ICP-MS determination. The condensation and deposition of high concentrations of carbon in mass cone interface and ion lens, which will decrease the sensitivity of element analysis, were avoided effectively by introducing O2 to plasma. The mass spectral interferences were eliminated by octopole reaction system (ORS). The matrix effects were calibrated to using Sc, Ge, Rh and Ir as internal standard elements. Au standard solution, which could form amalgam alloy with Hg, was dropped to eliminate the memory effect of Hg. The results show that the correlation coefficient for analyte is no less than 0.999 5, the detection limits is in the range of 0.06 - 20.1 ng x L(-1), the recovery is in the range of 990.4% - 110.2%, and the RSD is less than 4.8%. This method was very fast, simple and accurate to simultaneously analyze multi-elements in castor oil.

[Determination of Si and P in MnZn ferrites by inductively coupled plasma mass spectrometry].

An inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of Si and P in MnZn ferrites. The sample was digested by HNO3 + HCl with microwave digestion followed by dilution with ultrapure water then the above two elements in the solution were analyzed directly by ICP-MS. The analytical elements were by introducing the helium gas into the octopole reaction system (ORS) to eliminate the polyatomic interferences caused by the high salty matrixes. The matrix effects and the instrument drift could be commendably calibrated with Y as internal standard element. The working parameters of the instrument were optimized. The NIST SRM 362 and NIST SRM 364 were used as standard reference materials. The results showed a good agreement between the certified values and the experimental results for three analytes. The detection limits for Si and P is 0.91 and 0.27 microg x L(-1).

[Study on the determination of 14 inorganic elements in coffee by inductively coupled plasma mass spectrometry].

Samples of coffee were digested by microwave digestion, and inorganic elements amounts of Na, Mg, P, Ca, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Mo and Pb in sample solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS). HNO3 + H2O2 was used to achieve the complete decomposition of the organic matrix in a closed-vessel microwave oven. The working parameters of the instrument were optimized. The results showed that the relative standard deviation (RSD) was less than 3.84% for all the elements, and the recovery was found to be 92.00% -106.52% by adding standard recovery experiment. This method was simple, sensitive and precise and can perform simultaneous multi-elements determination of coffee, which could satisfy the sample examination request and provide scientific rationale for determining inorganic elements of coffee.

[Study on the determination of trace elements in bitter almond by inductively coupled plasma mass spectrometry].

Samples of bitter almond were digested by microwave digestion, and trace elements amounts of B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, Cd, Ba and Pb in sample solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS). HNO3 + H2O2 was used to achieve the complete decomposition of the organic matrix in a closed-vessel microwave oven. The working parameters of the instrument were optimized. The result showed that the relative standard deviation (RSD) was less than 4.79% for all the elements, and the recovery was 90.00%-109.30% by adding standard recovery experiment. This method was simple, sensitive and precise and can perform simultaneo multi-elements determination for bitter almond, which could satisfy the sample examination request and provide scientific rationale for determining inorganic elements in bitter almond.

[Direct determination of heavy metal elements in sweeteners by inductively coupled plasma mass spectrometry].

An analysis method of microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS) with octopole reaction system (ORS) was established for the determination of 10 heavy metal elements including Cr, Co, Ni, Cu, As, Cd, Sn, Sb, Hg and Pb in sweetener. Samples were decomposed by HNO3 and H2O2 followed by dilution with ultrapure water then the above 10 heavy metal elements in the solution were analyzed directly by ICP-MS. The use of ORS can eliminate the interference of polyatomic ions dramatically. 45Sc, 89Y, 115In and 209Bi as internal standard elements were used to compensate matrix effect and signal drift. The optimum conditions for the determination was tested and discussed. Under the optimal conditions, the detection limits of the 10 elements were in the range of 0.003-0.038 MICROg x L(-1), the recovery of the samples was in the range of 93.0%-106.6% and the relative standard deviation (RSD) < or = 3.4%, which showed that the method was very precise. The technique was applied for the quality control and safety evaluation of sweetener.

[Determination of impurity elements in high-purity aluminium using inductively coupled plasma-mass spectrometry after matrix extraction and separation].

To establish the method for the determination of 7 trace impurity elements including Co, Ni, Cu, Mo, Cd, Pb and Bi in high-purity aluminium by inductively coupled plasma-mass spectrometry (ICP-MS), the impurity elements were extracted from the aluminium matrix in the form of chelates with ammonium pyrrolidine dithiocarbamate (APDC) into methyl isobutylketone (MIBK). The instrument parameters, and conditions of separation and interference of matrix were discussed in detail. The optimal detection conditions were determined. The detection limits range from 0. 011 to 0. 052 microg x L(-1) depending on the elements, recoveries of samples are in the range of 92. 2%-103. 0%, and the precision is RSD<2. 3%. This method is accurate, quick and convenient. It is used in the determination of impurity elements in high-purity aluminium with satisfactory results.

[Determination of trace impurities in high purity titanium dioxide by high resolution inductively coupled plasma mass spectrometry].

An analytical method using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) for the rapid simultaneous determination of twenty six elements (Be, Na, Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Cd, Sn, Sb, Ba, Ce, Nd, Sm, Pt, Pb and Bi) in high purity titanium dioxide was described. Samples were decomposed by (NH4)2SO4 and H2SO4. Most of the spectral interferences could be avoided by measuring in the high-resolution mode. The matrix effects due to the presence of excess sulfuric acid and Ti were evaluated. The optimum conditions for the determination were tested and discussed. The standard addition method was employed for quantitative analysis. The detection limits are 0.004-0.63 microg x g(-1), the recovery ratio is 87.6%-106.4%, and the RSD is less than 3.5%. The method is accurate, quick and convenient. It has been applied to the determination of trace impurities in high purity titanium dioxide with satisfactory results.

[The matrix effects of organic acid compounds in ICP-MS].

The matrix effects arising from oxalic acid, lactic acid, tartaric acid and citric acid in inductively coupled plasma mass spectrometry (ICP-MS) were investigated. It has been proved that the sensitivity of analytes can be significantly enhanced by adding small amounts of organic acid compounds with adjusted nebulizer gas flow-rate, especially for the elements with ionization potential between 9 and 11 eV. The tartaric acid has higher enhancement effect on the signal intensity of the hard-to-ionize elements than oxalic acid, lactic acid and citric acid. The mechanism of the enhancement was investigated. The method has been used to determine Be, Zn, As, Se, Sb and Hg in water standard reference materials (SRM). The analytical results are very close to the certified values.

Using ensemble SVM to identify human GPCRs N-linked glycosylation sites based on the general form of Chou's PseAAC.

As the most frequent drug target, G-protein coupled receptors (GPCRs) are a large family of seven transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways. Glycosylation is one of the most complex post-translational modifications (PTMs) of proteins in eukaryotic cells. It plays important roles in a variety of cellular functions, including protein folding, protein trafficking and localization, cell-cell interactions and epitope recognition. Therefore, investigating the exact position of glycosylation site in GPCR sequence can provide useful clues for drug design and other biotechnology applications. Experimental identification of glycosylation sites is expensive and laborious. Hence, there is a significant interest in the development of computational methods for reliable prediction of glycosylation sites from amino acid sequences. In this article, we presented an effective method to recognize the sites of human GPCRs by combining amino acid hydrophobicity with ensemble support vector machine. The prediction accuracy, sensitivity, specificity, Matthews correlation coefficient and area under the curve values were 94.4, 89.7, 98.9%, 0.895 and 0.989, respectively. The establishment of such a fast and accurate prediction method will speed up the pace of identifying proper GPCRs functional sites to facilitate drug discovery.