Methodological refinements in the determination of 146 polychlorinated biphenyls,including non-ortho- and mono-ortho-substituted PCBs,and 26 organochlorine pesticides as demonstrated in heron eggs

A method for the determination of 146 polychlorinated biphenyls (PCBs), including four non-ortho- and eight mono-ortho-substituted congeners, and 26 chlorinated pesticides is described. The method consists of ultrasonic extraction, Florisil cleanup, HPLC fractionation over porous graphitic carbon (PGC), and final determination with GC/ECD, GC/MS, or both. Two PCB congeners (PCB 30 and PCB 161) and two polybromobiphenyls (2,4',5-tribromobiphenyl and 3,3',4,4'-tetrabromobiphenyl) were used as surrogate standards to evaluate the analytical efficiency. Four PCB congeners, PCB 14 and PCB 159 for the first fraction, PCB 61 for the second fraction, and PCB 204 for the third fraction, were used as internal standards to monitor the GC performance. The retention behavior of PCBs and pesticides on the PGC column are discussed. The method was found to be reproducible, effective, and reliable under the operational conditions proposed and was applied successfully to the analysis of individual PCBs and chlorinated pesticides in black-crowned night heron (Nycticorax nycticorax) egg samples.     

A novel optical sensor for the measurement of furfuraldehyde intransformer oil

Measuring the concentration of furfuraldehyde (FFA) within oil samples taken periodically from power transformers is usually carried out as a means of condition monitoring. Normally, laboratory-based techniques such as high performance liquid chromatography are applied for this measurement. We report the construction of a novel optoelectronic sensor for the determination of FFA in transformer oils to concentrations as low as 0.1 ppm. The sensor will form the basis of a compact and portable instrument that can be used by a nonspecialist operator to determine, on-site, the concentration of FFA in oil extracted from the transformer     

Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system

A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.     

Carbon disulfide measurement in marine waters using oxygen-doped electron capture detection with purge-trap preconcentration

An oxygen-doped GC/ECD system has been found to be highly sensitive to carbon disulfide (CS(2)). The detector shows a linear response up to at least 13 pmol of CS(2) injected and has a detection limit of 30 fmol. By combining the oxygen-doped GC/ECD with a purge-trap system, CS(2) in seawater can be readily separated and determined. A comparison is provided between an oxygen-doped ECD and a nondoped ECD.     

Trace detection of dissolved hydrogen gas in oil using a palladium nanowire array

The electrical resistance, R, of an array of 30 palladium nanowires is used to detect the concentration of dissolved hydrogen gas (H(2)) in transformer oil over the temperature range from 21 to 70 °C. The palladium nanowire array (PdNWA), consisting of Pd nanowires ～100 nm (width), ～20 nm (height), and 100 μm (length), was prepared using the lithographically patterned nanowire electrodeposition (LPNE) method. The R of the PdNWA increased by up to 8% upon exposure to dissolved H(2) at concentrations above 1.0 ppm and up to 2940 ppm at 21 °C. The measured limit-of-detection for dissolved H(2) was 1.0 ppm at 21 °C and 1.6 ppm at 70 °C. The increase in resistance induced by exposure to H(2) was linear with [H(2)](oil)(1/2) across this concentration range. A PdNWA sensor operating in flowing transformer oil has functioned continuously for 150 days.     

Determination of methionine and selenomethionine in yeast by species-specific isotope dilution GC/MS

A method for the simultaneous determination of methionine (Met) and selenomethionine (SeMet) in yeast using species-specific isotope dilution (ID) gas chromatography/mass spectrometry (GC/MS) is described. Samples were digested by refluxing for 16 h with 4 M methanesulfonic acid. Analytes were derivatized with methyl chloroformate and extracted into chloroform for GC/MS analysis. In addition to use of commercially available 13C-enriched Met and SeMet spikes for species specific ID analysis, a 74Se-enriched SeMet spike was also available for comparison of results. In selective ion monitoring mode, the intensities of ions at m/z 221, 222, 269, 270, and 263 were used to calculate the 221/222, 269/270, and 269/263 ion ratios for quantification of Met and SeMet. Concentrations of 5959 +/- 33 and 3404 +/- 12 microg g(-1) (one standard deviation, n = 6) with relative standard deviations of 0.55 and 0.36% for Met and SeMet, respectively, were obtained using 13C-enriched spikes. A concentration of 3417 +/- 8 microg g(-1) (one standard deviation, n = 6) was obtained using the 74Se-enriched SeMet spike. The concentration of SeMet measured in the yeast is equivalent to 66.43 +/- 0.24% of total Se and 30.31 +/- 0.11% of total Met is in the form of SeMet. Method detection limits (three times the standard deviation) of 3.4 and 1.0 microg g(-1) were estimated for Met and SeMet, respectively, based on a 0.25-g subsample of yeast with 1 mL of extract used for derivatization. A similar concentration of 5930 +/- 29 microg g(-1) (one standard deviation, n = 4) for Met and a lower concentration of 2787 +/- 49 microg g(-1) (one standard deviation, n = 4) for SeMet were obtained for this yeast sample using species-specific ID analysis based on GC/MS with 13C-enriched Met and SeMet spikes when a 2-h open microwave digestion approach using 8 M methanesulfonic acid was used.     

Permeation of captan through disposable nitrile glove

The purpose of this study was to investigate the permeation of an aqueous emulsion of the pesticide, captan, as a wettable powder (48.9% captan) through a disposable nitrile glove material using an American Society for Testing and Materials (ASTM)-type I-PTC-600 permeation cell. The goal was to investigate the protective capability of the gloves against dermatitis. The analytical method was based on gas chromatography–mass spectrometry (GC–MS) and gas chromatography–electron capture detection (GC–ECD). The least quantifiable limit (LQL) was 6 ng for GC–ECD and 30 ng for GC–MS. Testing was conducted using the ASTM F739 closed-loop permeation method and a worst-case aqueous concentration 217 mg/ml of captan 50-WP. The average permeation rates were low, with 12±5 ng/(cm² min) after 2 h, 50±25 ng/(cm² min) after 4 h, and 77±58 ng/(cm² min) after 8 h. The calculated diffusion coefficient was (1.28±0.10)×10⁻⁵ cm²/h. No significant swelling or shrinkage occurred at P≤0.05. Infrared (IR) reflectance analysis of pre- and post-exposure glove surfaces confirmed no outer or inner surface degradation. The disposable nitrile glove showed excellent resistance to a highly concentrated aqueous emulsion of captan. Because the ASTM normalized breakthrough detection time of 250 ng/cm² was <2 h, these gloves should not be reused once worn, and decontamination is not advised. Protection is also advised for agricultural reentry field workers, because captan has been shown to persist on crops with a half-life greater than the current reentry intervals of 1–4 days.     

波纹和百叶窗型表冷器空气侧换热性能的实验研究及分析方法

本文对方形组合式空调机组翅片管换热器空气侧的换热性能进行了实验研究和计算模型分析。将分布参数法（TTM）和创新的分排参数法(RDDM)拓展到方形组合式空调机组制热工况的实验数据处理中,分析翅片管换热器空气侧的换热性能,并与传统的ε-NTU法、集中参数法（LMTD）对比,4种方法计算的j因子和传热系数h偏差均在10%的范围内;基于分排参数模型,研究不同翅片形状、不同翅片间距、不同管径和不同翅片管排数下,传热因子j的变化情况。结果表明：j随Re增加逐渐减小,Re从3 000增至6 020,j下降了25.6%。相同Re下,开窗翅片比波纹翅片的j大,并随着Re的增加两者之间的最大偏差从26.3%缩小为8.3%。j随翅片间距和管径的增大而增大,随着管排数增加而降低,8排管时j急剧降低至约0.008。     

Screening of pentachlorophenol-contaminated wood by thermodesorption sampling and photoacoustic detection

The still-remaining high amounts of pentachlorophenol (PCP), used as wood preservative, in buildings and in waste wood are a potential risk for humans and the environment. To ensure a fast and selective measurement of PCP, a screening tool was developed, which is not only sensitive, but, unlike conventional methods, it requires no added chemicals, is simple, cost-effective, mobile, and capable of on-site operation. The instrument combines light-induced thermodesorption sampling followed by an external cavity diode laser based photoacoustic detector. Measurements on wood samples proved that the system can determine PCP to as low as a concentration of 10 microg/cm2 within minutes without destruction of the sample. The system was calibrated with reference to the concentration of PCP impregnated on the wood surface. It is demonstrated that measurements are not influenced by moisture content of the wood samples.     

Low-Level (PPB)Determination of Cisplatin in Cleaning Validation (Rinse Water) Samples. II. A High-Performance Liquid Chromatogrphic Method

A high-performance liquid chromatographic (HPLC) method is described for the determination of residual levels of cisplatin from extracts of surfaces with very low surface area; from extracts of surfaces of coupons made of Teflon® (polytetrafluoroethylene, PTFE), stainless steel, and glass; and in aqueous solution collected after rinsing equipment and parts. Initially, the method was developed to determine cisplatin at concentrations ranging from 20 to 200 ng/ml by direct injection. Retaining the same method conditions, the scope of the method was expanded by the addition of a sample preconcentration step, allowing analyses at levels ranging from 0.5 ng to 20 ng/ml. Preconcentration is necessary for the determination of cisplatin in rinse waters at a quantifiable concentration of about 2 PPB. Under these conditions, the detection limit is about 0.2 to 0.3 ng/ml. Residual cisplatin on different types of surfaces, including surfaces with very low surface area, can be determined by swabbing each test surface with a derivatizing solution. The cisplatin recovered in the swabbing solution can be analyzed by HPLC using direct injection or preconcentration, depending on the expected level of cisplatin in the sample. Initial methods were developed to quantitate at a cisplatin concentration of about 100 PPB or higher in solution extracted from surfaces. However, when surface areas are limited because of the size of the parts, solution concentration becomes very low as a result of the minimum volume required for extraction. To support the application of swabbing techniques to surface analysis, stainless steel, Teflon, and glass surfaces were spiked with cisplatin at 2.5 to 20 ng/cm². Satisfactory overall recoveries of 90% ± 10% were obtained from all surfaces. Cisplatin has no ultraviolet/visible (UV/Vis) spectral-active functional group that can be used to detect low levels of cisplatin. Hence, diethyldithiocarbamate (DDTC) was used as a derivatizing agent to increase sensitivity to UV absorption at 340 nm. Diethyldithiocarbamate forms complexes with the platinum in cisplatin to yield a platinum-DDTC (Pt-DDTC) complex with a high molar-extinction coefficient. The Pt(DDTC)² complex thus formed was chromatographically separated and then quantitated by comparison of its detector response to that of a similarly derivatized standard preparation. DDTC also has application as a cleaning agent for cisplatin (e.g., for production equipment cleaning, spill cleanup). Destruction of cisplatin can be effected by the reaction of cisplatin with this cleaning agent. Derivatization of cisplatin will convert active cisplatin to platinum-DDTC on surfaces or in solution. Final cleaning can be accomplished using a water-for-injection rinse. After such a cleaning process, the rinse water, when collected and analyzed, showed levels of free cisplatin less than the detection concentration of 0.2 PPB and a total platinum concentration less than 10 PPB as Pt-DDTC complex.     

An experimental investigation of heat transfer and friction losses of interrupted and wavy fins for fin-and-tube heat exchangers

The present paper discusses the results of an extensive investigation about the performance of various fin configurations, carried out in the Luve Contardo experimental facilities and aimed to enhance the heat transfer capabilities of air-cooled condensers and liquid coolers. Test results here discussed are relative to 15 coil prototypes, having the same tube and fin geometry (25×21.65 mm staggered 5/8” tube banks, 2 mm fin spacing) but different fin surface geometry, from flat to wavy to louvered to “winglet”. Different rates of heat transfer and pressure loss enhancement were obtained, also depending on the quality of the pressing process. General approaches to evaluate the “goodness” of one fin design with respect to another one provided questionable results: pressure loss influence on the air flow cannot be properly evaluated unless the actual fan head curve and the coil dimensions (front area and rows number) are stipulated. The performance of air-cooled condensers was therefore predicted and compared, for various fin design and for coil arrangements of practical interest. The type of fin adopted strongly influences the heat exchanger performance and louvered fins generally provide the best results.     

Simulation study on the use of strippable coatings for radiocesium decontamination of concrete

The contamination and decontamination of concrete by a soluble contaminant (radiocesium) was modeled using the finite element method. The decontamination process relied on the application of a hyper-accumulating strippable polymer (HASP?) [corrected] to sequester contaminant that was transported to the concrete surface. The model accounted for the transport of cesium by diffusion, capillary pressure-driven convection, and equilibrium adsorption of cesium within the concrete substrate and HASP? [corrected] coating. The influence of HASP? [corrected] properties (porosity, thickness, and cesium distribution coefficient), and a wide range of operation variables (HASP? [corrected] contact time, delay time until HASP? [corrected] decontamination begins, influence of evaporative boundary conditions) on final decontamination efficacy were explored. Transient saturation (moisture content) and cesium concentration profiles were used to understand key factors in the decontamination process, and water wicking experiments were performed to validate the capillary convection model. The results showed that prompt HASP? [corrected] application after the initial contamination event is critical for high decontamination efficacies. A 30-day HASP? [corrected] treatment removed about 90% of the contaminant when HASP? [corrected] was applied within 30min of the initial contamination event, whereas the decontamination process removed less than half as much cesium if months were allowed to elapse months prior to decontamination. Multiple applications of fresh HASP? [corrected] were also shown to improve decontamination performance under certain circumstances.     

The operating performance and products distribution of the catalytic oxidation of methyl-isobutyl-ketone over a Pt/gamma-Al2O3 catalyst

Catalytic oxidation is one of the cost-effective technologies to solve the troublesome volatile organic compounds. This study treated methyl-isobutyl-ketone (MIBK) by a commercial catalyst, Pt/gamma-Al(2)O(3), in a fixed-bed reactor. The effects of operating factors, such as operating temperature, MIBK concentration, space velocity, and O(2) concentration, on the performance of the catalyst were investigated. The products and reactants distributions from the oxidation of MIBK over Pt/gamma-Al(2)O(3) were observed. The results show that the products containing carbon atoms are CO, CO(2), and C(3)H(6)O. Two catalyst life-tests were also carried out to characterize the deactivation effect of MIBK. The result shows that the deactivation effect may be due to the coke on the catalyst surface at 423 K. From the statistical analysis, the operating temperature is the most effective factor on the conversion of MIBK. The catalysts were also characterized by surface area analysis and elemental analysis before and after the test. The results show that the catalytic deactivation may be due to carbon coating. At low temperature (423 K), the phenomenon of carbon coating was more obvious than that at high temperature (573 K). The product distributions from the oxidation of MIBK over Pt/gamma-Al(2)O(3) were analyzed by GC. The results indicate that the C(3)H(6)O is formed from the beginning, presenting a peak at 423 K, 6.54 ppm. The CO concentration also peaked at the same temperature, 6.84 ppm.     

Design of efficient zeolite sensor materials for n-hexane

The effectiveness of several zeolite catalysts was investigated using the cataluminescence (CTL) gas sensor system. Trace amounts of n-hexane in air samples were detected by this method. This research establishes that the specific pore size of the zeolite offers designable environment for selective CTL reaction, and "Lewis-type" basic sites appear to contribute to the catalytic nature of the zeolite surface. By incorporating either Cs+ or K+, the velocity and luminescence intensity of these catalytic reactions increase while going from Na to Cs, according to the basic nature of this group of cations in the following order: Cs > K > Na. The proposed sensor shows high sensitivity and selectivity to n-hexane at a mild reaction temperature of 225 degrees C. Quantitative analysis was performed at a selected wavelength of 460 nm. The linear range of CTL intensity versus concentration of n-hexane was 0.776-23.28 microg/mL (R = 0.997, n = 7) on CsNaY, and 0.776-23.28 microg/mL (R = 0.998, n = 7) on CsNaX, with a detection limit of 0.155 microg/mL (signal-to-noise ratio 3). Interferences from foreign substances such as methanol, ethanol, 2-propanol, acetone, acetonitrile, chloroform, or dichlormethane and other alkanes, aromatics, and alkyl aromatics such as methane, n-pentane, 3-methylpentane, 3,3-dimethylpentane, methylbenzene, ethylbenzene, and sec-butylbenzene were very low or not detectable. Results of a series of GC and GC/MS experiments suggest that the possible mechanism of the reaction is the formation of an unstable transition structure with a four-member ring, and this ring most probably consists of an oxygen atom and a carbonium ion localized on the zeolite suface.     

超临界二氧化碳萃取—GC/ECD测定土壤中高级脂肪酸

本文报导了一种用超临介二氧化碳萃取—气相色谱电子捕获检测器测定土壤中高级脂肪酸的实用分析方法.即采用超临介二氧化碳萃取法萃取土壤中的高级有机酸,选用五氟苄基溴(PFBBr)衍生化反应生成相应的酯,经过硅胶柱纯化、最后用GC(ECD)进行测定。方法简便、可靠。应用该方法测定了中国几类未开垦森林土壤中的高级脂肪酸,获得了满意结果。     

The behavior of organic components in copper recovery from electroless plating bath effluents using 3D electrode systems

An electrochemical method was applied for the recovery of copper both from the spent solutions and from the rinse waters of electroless copper plating baths, containing copper sulfate, formaldehyde, quadrol, and NaOH. Experiments were conducted in a rotating packed cell (Rollschichtzelle) to investigate the effects of current density, electrolyte composition, temperature, and pH on the copper recovery. All the copper (final CCu=0.1 ppm) was recovered from the waste and rinse waters of chemical copper plating plants with 70% current efficiency by the electrochemical treatment in a rotating packed cell at 130 A/m2 current density, room temperature, with 5mm diameter cathode granules, with the presence of formaldehyde, and with a specific energy consumption of 3.2-3.5 kW h/kg Cu. On the other hand, final copper concentrations of 5 ppm were reached with 62% current efficiency and 5.5-5.8 kW h/kg Cu specific energy consumption, with electrolytes containing no formaldehyde.     

Valence parity to distinguish c' and z• ions from electron capture dissociation/electron transfer dissociation of peptides: effects of isomers, isobars, and proteolysis specificity

Valence parity provides a way to distinguish between N-terminal and C-terminal electron capture dissociation/electron transfer dissociation (ECD/ETD) product ions based on their number of hydrogen plus nitrogen atoms determined by accurate mass measurement and forms a basis for de novo peptide sequencing. The effect of mass accuracy (0.1-1 ppm error) on c'/z(?) overlap and unique elemental composition overlap is evaluated for a database of c'/z(?) product ions each based on all possible amino acid combinations and four subset databases containing the same c' ions but with z(?) ions determined by in silico digestion with trypsin, Glu-C, Lys-C, or chymotrypsin. High mass accuracy reduces both c'/z(?) overlap and unique elemental composition overlap. Of the four proteases, trypsin offers slightly better discrimination between N- and C-terminal ECD/ETD peptides. Interestingly, unique elemental composition overlap curves for c'/c' and z(?)/z(?) peptide ions exhibit discontinuities at certain nominal masses for 0.1-1.0 ppm mass error. Also, as noted in the companion article (Polfer et al. Anal. Chem.2011, DOI: 10.1021/ac201624t), the number of ECD/ETD product ion amino acid compositions as a function of nominal mass increases exponentially with mass but with a superimposed modulation due to higher prevalence of certain elemental compositions.     

Screening of several drugs of abuse in Italian workplace drug testing: performance comparisons of on-site screening tests and a fluorescence polarization immunoassay-based device

According to the Italian laws, some categories of workers entrusted with duties possibly constituting a threat to security, physical safety, and health of third parties have to be screened to exclude the use/abuse of the following drugs of abuse: opiates, cocaine, cannabinoids, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, methadone, and buprenorphine. Toxicological tests can be performed with urinary on-site rapid screening devices, provided that sensitivities up to specified cutoffs are ensured. The present study reports performances, in terms of sensitivity, specificity, and accuracy, of an automatic on-site test and of an FPIA-based device, using gas chromatography/mass spectrometry (GC/MS) as a reference methodology. Three levels of concentration were tested, corresponding to the cutoff and to 2 and 3 times the limits, respectively. In terms of sensitivities, neither the on-site nor the benchtop instrumentations gave positive results, since values of zero percentage were obtained for concentrations up to 2-fold the limits. Even if good results were obtained in terms of specificity and accuracy by both devices, none of them seem to be adequate for the current application to the toxicological screening at workplaces. In fact, a rapid screening device can be used for drug tests provided that it ensures sensitivity at the prescribed cutoffs. Data showed that such is completely rejected and a more sensitive instrumentation should be preferred.     

茶叶中啶虫脒残留量检测方法的研究

建立了啶虫脒在茶叶中残留量的气相色谱检测方法。样品采用丙酮／正已烷（1／2,v／v）混合溶剂提取,经LC-18SPE小柱净化,气相色谱（配ECD）检测,以保留时间和外标法定性、定量。结果表明,该方法的最低检出限为0．004mg／kg,不同水平的加标回收率范围为73．8％～108．7％,RSD（n=6）为8．51％～10．1％。方法操作简便,净化效果理想,能满足残留分析的要求,可用于茶叶啶虫脒残留量的测定。该方法也可为其他产品中啶虫脒残留量的测定提供参考。     

Determination of alpha- and beta-hydroxycarbonyls and dicarbonyls in snow and rain samples by GC/FID and GC/MS employing benzyl hydroxyl oxime derivatization

A flame ionization detector (FID) combined with capillary gas chromatography (GC/FID) and gas chromatography/ mass spectrometry (GC/MS) has been used to identify multifunctional carbonyls in wet precipitation samples. The carbonyl groups were first derivatized to O-benzylhydroxyloxime (BH oxime) by using O-benzylhydroxylamine. The BH oxime derivatives were then treated with N,O-bis(trimethylsilyl)acetamide for the hydroxyl group to derive their TMS ethers. The BH oxime/TMS derivatives were measured using GC/FID as well as GC/MS on positive EI and CI (isobutane was used as CI gas) modes. Three groups of carbonyl compounds (monoaldehydes, dicarbonyls, hydroxycarbonyls) were identified in the samples by using this method. We have identified, for the first time, a group of alpha- and beta-hydroxycarbonyls, glycolaldehyde, hydroxyacetone, and 4-hydroxy-2-butanone, in wet precipitation samples. Concentrations of hydroxycarbonyls ranged from 0.9 to 53.8 microg/L in the precipitation samples. Their concentration level is similar to that of low molecular weight dicarboxylic acids, which have been reported as major water-soluble organic compounds in rain.