Analytical issues in monitoring drinking-water contamination related to short-term, heavy rainfall events

Heavy rainfall events, increasing in frequency and intensity with climate change, impact on the quality of the water resource used for drinking-water production. Small-scale water suppliers are particularly sensitive because of their management and the related difficulties of adapting treatment to variations. Decision-support systems, based on monitoring and analytical tools, need to be developed to improve crisis-management procedures related to such events. After presenting the issues related to heavy rainfall events, the article summarizes the tools currently used for quality control of drinking water within this framework, the need for developments and other requirements.     

On-chip fraction collection for multiple selected ssDNA fragments using isolated extraction channels

High efficiency and high-purity fraction collection is highly sought in analysis of fragments-of-interest from selective polymerase chain reaction (PCR) products generated by High Coverage Gene Expression Profiling (HiCEP) methods. Here we demonstrate a new electrophoretic chip device enabling automatic high-efficient fractionation of multiple ssDNA target fragments during a run of separation. We used thoroughly isolated extraction channels for each selected target to reduce the risk of cross-contamination between targets due to cross-talk of extraction channels. Fragments of 35, 108 and 138 b, were successfully isolated, then the recovery was PCR-amplified and assessed by capillary electrophoresis (CE) analysis. Total impurity level of the targets due to unwanted fragments of 0.7%, 2% and 6% respectively, was estimated. Difficulties in collecting multiple target factions are due to band diffusion and DNA adsorption to the walls for the fragments in the separation channel, which is generated by transferring the DNA target fraction from the extraction section to the target reservoir. Therefore, we have carefully measured band broadening and analyzed its influence on the separation resolution due to the delay.     

Validated method using liquid chromatography-electrospray ionization tandem mass spectrometry for the determination of contamination of the exterior surface of vials containing platinum anticancer drugs

Contamination of the exterior surface of vials of cytostatic drugs by the drugs themselves is a potential hazard to human health. This study developed a validated method using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) for the determination of contamination of the exteriors of vials of cisplatin and carboplatin. Large Alpha^® sampling swabs were employed to wipe the vial exterior. Cisplatin or carboplatin and gold(III) as an internal standard were derivatized by N,N-diethyldithiocarbamate (DDTC). Pt(DDTC)₃⁺ and Au(DDTC)₂⁺ were monitored by the respective transitions of m/z 639.3-490.9 and 493.0-345.0, respectively. Each separation was completed within 9 min using a 3 μm particle ODS-column. Calibration curves for cisplatin and carboplatin were linear over concentration ranges of 30-10,000 and 30-30,000 pg vial⁻¹, respectively. The accuracies and precisions were 96.1-102.5% and within 8.2% for intra-assay and 99.6-103.3% and within 7.6% for inter-assay, respectively. Their lower limit of quantification was 30 pg vial⁻¹. Amounts of 0.17-17.0 ng vial⁻¹ as cisplatin and 0.48-794 ng vial⁻¹ as carboplatin were detected from the exterior surface of the vials. This validated method using LC-ESI-MS/MS for the determination of platinum anticancer drugs is helpful for monitoring contamination of the exterior surface of drug vials.     

A driver gas detection device for shock tunnels

A device has been produced which can detect the contamination of the test gas by the driver gas in a reflected shock tunnel. This device monitors the static pressure in a converging duct. The duct is designed to choke at a predetermined contamination level due to the change in the specific heat ratio produced by the contaminants. Experimental results are given for a freestream enthalpy of nominally 6 MJ/kg.     

关于两类污染数据回归分析的参数估计

研究简单回归模型：ｙｊ＝ａ＋βｘｊ＋εｊ，ｊ＝１，２，…，ｎ，其中Ｅεｊ＝０，Ｅε＾２ｊ＝σ＾２ｊ；但ｙ１，ｙ２，…，ｙｎ受到另一独立同分布随机变量序列ｔ，ｔ２，…，ｔｎ两种不同方式的污染，ｔｊ与ｙｊ独立。本文给出了两种污染方式下的ａ、β和污染参数的估计。     

Modifications of He implantation induced cavities in silicon by MeV silicon implantation

Doppler broadening spectroscopy (DBS) coupled to a slow positron beam has been used to investigate the formation of He-cavities in the presence of high vacancy concentrations in Cz-Si (1 1 1). Si samples were first implanted with MeV Si ions in order to create a damaged Si layer. DBS measurements show the presence of divacancy (SV₂/SSi lattice=1.052,WV₂/WSi lattice=0.83) from the surface up to 4.2 μm depth with a concentration higher than 10¹⁸ cm⁻³. The thickness of this damaged layer was confirmed by spreading resistance measurements. In the second step, samples were implanted with 50 keV ³He with fluence of 10¹⁶ cm⁻². DBS results show that the apparent divancancy concentration decreases at ³He implantation depth ∼435 nm due to ³He passivation of vacancies that occurs during the implantation process. After 900 °C annealing, large defects are detected at depth up to 2 μm and (S, W) values suggest the detection of cavities at the implantation depth. We also report the possible presence of impurity complexes. The formation of these complexes is attributed to the gettering of metallic impurities present in the Si sample.     

可压缩核废料污染问题的修正迎风差分格式及收敛性分析

对无弥散项的可压缩核废料污染问题模型建立修正迎风差分格式,并进行了收敛性分 析,最后给出其l2误差估计．     

Assessment of pesticide contamination in soil samples from an intensive horticulture area, using ultrasonic extraction and gas chromatography-mass spectrometry

In order to reduce the amount of sample to be collected and the time consumed in the analytical process, a broad range of analytes should be preferably considered in the same analytical procedure. A suitable methodology for pesticide residue analysis in soil samples was developed based on ultrasonic extraction (USE) and gas chromatography–mass spectrometry (GC–MS). For this study, different classes of pesticides were selected, both recent and old persistent molecules: parent compounds and degradation products, namely organochlorine, organophosphorous and pyrethroid insecticides, triazine and acetanilide herbicides and other miscellaneous pesticides. Pesticide residues could be detected in the low- to sub-ppb range (0.05–7.0 μg kg⁻¹) with good precision (7.5–20.5%, average 13.7% R.S.D.) and extraction efficiency (69–118%, average 88%) for the great majority of analytes. This methodology has been applied in a monitoring program of soil samples from an intensive horticulture area in Póvoa de Varzim, North of Portugal. The pesticides detected in four sampling programs (2001/2002) were the following: lindane, dieldrin, endosulfan, endosulfan sulfate, 4,4′-DDE, 4,4′-DDD, atrazine, desethylatrazine, alachlor, dimethoate, chlorpyrifos, pendimethalin, procymidone and chlorfenvinphos. Pesticide contamination was investigated at three depths and in different soil and crop types to assess the influence of soil characteristics and trends over time.     

Mechanism of fe impurity incorporation into semi-insulating gaas crystals

Total concentration of Fe impurity in Cr-doped semi-insulating GaAs crystals grown by various techniques was analyzed by atomic-absorption spectrophotometry. Analytical results show that Fe contamination likely occurs during HB-crystal growth. The Fe contamination may have originated mainly from the sandblasting procedure of the silica boat with impure abrasive. The interaction between the sandblasted boat surface and the GaAs melt was found to play an important role in the Fe impurity incorporation. It was also found that most of the Fe impurity is not incor-porated as elementary Fe in the HB-grown crystals. As far as the Fe contamination is concerned, direct synthesis LEC techniques seem to be the most advantageous at present.