[Determination of Carbaryl in Rice by Using FT Far-IR and THz-TDS Techniques].

Determination of carbaryl in rice by using Fourier transform far-infrared (FT- Far-IR) and terahertz time-domain spectroscopy (THz-TDS) combined with chemometrics was studied and the spectral characteristics of carbaryl in terahertz region was investigated. Samples were prepared by mixing carbaryl at different amounts with rice powder, and then a 13 mm diameter, and about 1 mm thick pellet with polyethylene (PE) as matrix was compressed under the pressure of 5-7 tons. Terahertz time domain spectra of the pellets were measured at 0.5~1.5 THz, and the absorption spectra at 1.6. 3 THz were acquired with Fourier transform far-IR spectroscopy. The method of sample preparation is so simple that it does not need separation and enrichment. The absorption peaks in the frequency range of 1.8-6.3 THz have been found at 3.2 and 5.2 THz by Far-IR. There are several weak absorption peaks in the range of 0.5-1.5 THz by THz-TDS. These two kinds of characteristic absorption spectra were randomly divided into calibration set and prediction set by leave-N-out cross-validation, respectively. Finally, the partial least squares regression (PLSR) method was used to establish two quantitative analysis models. The root mean square error (RMSECV), the root mean square errors of prediction (RMSEP) and the correlation coefficient of the prediction are used as a basis for the model of performance evaluation. For the R,, a higher value is better; for the RMSEC and RMSEP, lower is better. The obtained results demonstrated that the predictive accuracy of. the two models with PLSR method were satisfactory. For the FT-Far-IR model, the correlation between actual and predicted values of prediction samples (Rv) was 0.99. The root mean square error of prediction set (RMSEP) was 0.008 6, and for calibration set (RMSECV) was 0.007 7. For the THz-TDS model, R. was 0. 98, RMSEP was 0.004 4, and RMSECV was 0.002 5. Results proved that the technology of FT-Far-IR and THz- TDS can be a feasible tool for quantitative determination of carbaryl in rice. This paper provides a new method for the quantitative determination pesticide in other grain samples.

[Chemical composition and mass closure of particulate matter in Beijing, Tianjin and Hebei megacities, Northern China].

To seek an efficient prevention and control method of regional atmospheric pollution in Jingjinji area, mass concentrations and size-resolved chemical composition of particulate matter were investigated at four urban sites and one background site from June 2009 to May 2010. The results show that the annual mean concentration of PM10 was 124, 141, 151 and 183 microg x m(-3) in Beijing, Tianjin, Tangshan and Baoding respectively, while the corresponding percentage of daily limit value exceedances was 29%, 36%, 39% and 52%, which is well above the maximum allowed limit of 150 microg x m(-3) (National Air Quality Stand II). As for PM2.5, the annual average concentration was 55, 68, 79 and 116 microg x m(-3) in Beijing, Tianjin, Tangshan and Baoding, which is higher than that in the background site with a factor of 1.5, 1.9, 2.2 and 3.2, respectively, while the corresponding proportion of daily exceedances of 75 microg x m(-3) (WHO IT-1) was 29%, 33%, 42% and 65%. Seasonal variations of PM2.5 and PM10 concentration were significant at the urban sites with the highest value being measured in winter. In order to reconstruct the particle mass, the determined components were classified into five groups as follows: secondary inorganic aerosol, sea salt, heavy metal, mineral matter and construction dust. The urban-sites-averaged contribution of these components to PM2.1 was 28.5%, 5.8%, 1.8%, 14.8% and 3.8%, whereas that to PM2.1-9 was 11.3%, 6.7%, 1.1%, 43.5% and 7.6%, respectively. The particle pollution was very severe in Baoding with the major component of secondary inorganic aerosol and mineral matter in PM2.1 and PM2.1-9, respectively. The estimated contribution of anthropogenic sources to PM2.1 in Beijing was larger than that of natural sources with a factor of 3.5 whereas the ratio of anthropogenic sources to natural ones was 0.6 for PM2.1-9. The contribution of secondary components to PM2.1 was equivalent to primary emissions, which suggests the precursors emitted from coal combustion and vehicle exhaust should be controlled in the target area. In contrast, the ratio of primary emissions to secondary particulate matters in PM2.1-9 was up to 5, indicating measures are required to reduce dust from construction areas. Finally, the reduction of human health-related heavy metals is also necessary despite its minor contribution to particles.

[Study on the method of using ICP-MS to determine microelements in the animal feed].

The method for the determination of microelements such as Cu, Zn, Fe, Mn, Cr, Cd, Pb, As and Se in the animal feed by inductively coupled plasma-mass spectrometry was developed. The operation parameters, spectrum interference, matrix effect and memorial effect were studied in detail. Under optimal condition, the detection limits of these nine elements were from 2.03 x 10(-3) to 3.17 microg x L(-1), and the linear range was over three orders with a correlation coefficient above 0.999. This method was applied directly to determine microelements in real samples involving the standard wheat powder, formular feed and pre-mix feed. The determination results of microelements in the standard wheat powder accorded with reference results. The recovery of microelements in the formular feed was from 86% to 115%, and the relative standard deviations < or = 8.2% (n = 6). The results of elements content in the pre-mix feed were identical with those determined by national standard method. This method is simple, sensitive, accurate and can perform simultaneous multi-elements determination compared with conventional method of animal feed determination. The results were satisfactory.

Distribution of platinum group elements in road dust in the Beijing metropolitan area, China.

Dust samples collected from the Beijing metropolitan area (China) were evaluated to determine the distribution and the concentration of platinum group elements (PGEs). The dust particles that were smaller than 100 mesh size fraction (150 microm) were analyzed after aqua regia digestion. Concentrations of Pt, Rh, and Pd were found to be between 3.96 and 356.3 ng/g, 2.76 and 97.11 ng/g, and 0.1 and 124.9 ng/g, respectively, in the urban areas of Beijing, whereas for the background samples collected from the suburbs of Beijing, the concentrations of Pt, Pd, and Rh were very low and ranged from 0.1 to 0.9 ng/g, 0.5 to 1.4 ng/g, and 0.8 to 2.2 ng/g, respectively. The distributions of PGEs in road dust were an accurate reflection of the levels of pollution and were found to match with the local traffic conditions. A strong positive correlation was established among all the elements found in road dust. This suggests that emissions of abraded fragments from vehicle exhausts may be the source of the high concentration of Pt, Rh, and Pd in road dust along the main roads of Beijing.

[Elimination of spectral interference in the determination of trace palladium in plants by inductively coupled plasma-mass spectrometry].

Inductively coupled plasma-mass spectrometry (ICP-MS) was employed to determine palladium in plants. The spectroscopic interferences with Pd in the ICP-MS determination were studied in detail. Spectral interferences with Pd were corrected using mathematical correction equation based on abundance ratio. The potential of the method was evaluated by the comparison with the method using complex separation by DDTC and the determination of PGEs (platinum group elements) in standard reference materials (GBW 07293). The experimental results showed that using the studied method, Pd could be determined in the leaves of Japanese pagoda, annual grass, holly and tine tree collected along main roads in Beijing (China) during 2005 with satisfactory.

[Simultaneous determination of trace platinum, palladium and rhodium in environmental dust samples by ICP-MS after open-digestion].

A sensitive method for simultaneous determination of Pt, Pd and Rh in dust samples by ICP-MS after open-digestion was developed. The digestion method for the samples and conditions for measurement for ICP-MS were studied in detail. Aquaregia was proved to be a better solvent for the digestion of dust samples. Under the optimum conditions, the limits of detection of Pt, Pd and Rh were 0.48, 4.22 and 0.42 ng x g(-1), respectively. The proposed method was applied to the real sample analysis, and good recoveries were obtained. The recoveries of Pt, Pd and Rh were found to be between 87.6%-88%, 85.2%-87.8%, and 93%-95%, respectively.

[Solid phase extraction and room temperature phosphorimetry coupling technique and its application].

The principle and application in the environmental analysis of Solid Phase Extraction (SPE) combined with Room Temperature Phosphorescence (RTP) analysis were reviewed. The principle, device, separation modes, operation procedures and application of SPE were commented. The merits and shortages in the operation procedure and quantitative analysis of classic RTP were also summarized. The potential application in the trace sample analysis and the advantage of coupling technique of SPE and RTP were indicated. The sensitivity and selectivity of the coupling technique could be greatly increased because of the strong enrichment ability of the SPE materials and the high selectivity of RTP. So far the technique has been successfully used in the analysis of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PClDBFs) in the environmental samples according to their phosphorescence emission after preconcentration on the Whatman 1PS filter paper and C18 or C8 SPE membranes.

A new simple and rapid electrochemical method for the determination of hydroxyl radical generated by Fenton reaction and its application.

A simple and rapid electrochemical method to detect the hydroxyl radical is described. This method employed the reaction between.OH and dimethyl sulfoxide (DMSO) to generate quantitatively formaldehyde, which then reacted with hydrazine hydrochloride at pH 6.2. The product showed a second-order derivative cathodic wave with the peak potential of -1.08 V( vsSCE) by single sweep oscillopolarography. The electrochemical behavior of the product was investigated by single sweep oscillopolarography and cyclic voltammetry. The experimental conditions for the measurement were optimized and the scavenging activity of some flavonoids on hydroxyl radicals was studied.