Solvent vapour monitoring in work space by solid phase micro extraction

Solid phase micro extraction (SPME) is a fast, solvent-less alternative to conventional charcoal tube sampling/carbon disulfide extraction for volatile organic compounds (VOC). In this work, SPME was compared to the active sampling technique in a typical lab atmosphere. Two different types of fibre coatings were evaluated for solvent vapour at ambient concentration. A general purpose 100 microm film polydimethylsiloxane (PDMS) fibre was found to be unsuitable for VOC work, despite the thick coating. The mixed-phase carboxen/PDMS fibre was found to be suitable. Sensitivity of the SPME was far greater than charcoal sorbent tube method. Calibration studies using typical solvent such as dichloromethane (DCM), benzene (B) and toluene (T) showed an optimal exposure time of 5 min, with a repeatability of less than 20% for a broad spectrum of organic vapour. Minimum detectable amount for DCM is in the range of 0.01 microg/l (0.003 ppmv). Variation among different fibres was generally within 30% at a vapour concentration of 1 microg DCM/l, which was more than adequate for field monitoring purpose. Adsorption characteristics and calibration procedures were studied. An actual application of SPME was carried out to measure background level of solvent vapour at a bench where DCM was used extensively. Agreement between the SPME and the charcoal sampling method was generally within a factor of two. No DCM concentration was found to be above the regulatory limit of 50 ppmv.     

Comparison of oil composition changes due to biodegradation and physical weathering in different oils

The well-characterized Alberta Sweet Mixed Blend oil and several other oils which are commonly transported in Canada were physically weathered and then incubated with a defined microbial inoculum. The purpose was to produce quantitative data on oil components and component groups which are more susceptible or resistant to biodegradation, and to determine how oils rank in relation to each other in terms of biodegradation potential. The biodegraded oils were characterized by quantitative determination of changes in important hydrocarbon groups including the total petroleum hydrocarbons, total saturates and aromatics, and also by quantitation of more than 100 individual target aliphatic, aromatic and biomarker components. The study reveals a pattern of distinct oil composition changes due to biodegradation, which is significantly different from the pattern due to physical or short-term weathering. It is important to be able to distinguish between these two forms of loss, so that loss due to weathering is not interpreted as loss due to biodegradation in the laboratory or in the field. Based on these findings, the oil composition changes due to biodegradation can be readily differentiated from those due to physical weathering. To rank the tested oils with respect to biodegradability, losses in total petroleum hydrocarbons and aromatics were used to calculate biodegradation potential indices, employing equations proposed by Environment Canada and the US National Oceanic and Atmospheric Administration. The different methods produced very similar biodegradation trends, confirming that patterns of oil biodegradability do exist.     

Characterization, weathering, and application of sesquiterpanes to source identification of spilled lighter petroleum products

Biomarkers have become increasingly important for identifying the source of spilled oil, due to their specificity and high resistance to biodegradation. The biomarkers most commonly used in forensic investigations are the high molecular weight (MW) tri- and pentacyclic terpanes and steranes. For lighter petroleum products such as jet fuels and diesels, the refining processes remove most high MW biomarkers from the original crude oil feedstock. The smaller bicyclic sesquiterpanes, however, are concentrated in these products. Sesquiterpanes are ubiquitous components of crude oils and ancient sediments. Examination of GC-MS chromatograms of these bicyclic biomarkers using their characteristic fragment ions (m/z 123, 179, 193, and 207) provides a highly diagnostic means for identifying spilled oil, particularly for lighter refined product samples that are difficult to identify by current techniques. In this work, sesquiterpanes in crude oils and petroleum products are identified and characterized, distributions of sesquiterpanes in oils and refined products are compared, the effects of evaporative weathering on sesquiterpane distributions are examined, and a methodology using diagnostic indices of sesquiterpanes is developed for oil correlation and differentiation. Finally, two case studies are presented to illustrate the unique utility of sesquiterpanes for fingerprinting and identifying unknown diesel spills.     

Forensic fingerprinting of diamondoids for correlation and differentiation of spilled oil and petroleum products

Diamondoids (adamantanes and diamantanes) are rigid, three-dimensionallyfused cyclohexyl-ring alkane compounds that can be found in almost all crude oils and in most petroleum products. Forforensic environmental investigations, the most commonly used biomarkers are high molecular weight (MW) tri- to pentacyclic terpanes and steranes. Most of these high MW biomarkers, however, are removed from the original crude oil feedstocks during the refining processes, while smaller biomarkers including diamondoids are concentrated in petroleum products. Fingerprinting diamondoids could thus provide another diagnostic means for correlation and differentiation of spilled oils and be particularly valuable for light to midrange distillates, such as jet and diesel fuels, the source of which may be difficult to identify using routine biomarker techniques. In this work, a reliable GC-MS analytical method has been developed for characterization and quantitation of diamondoids. The method detection limits for five target diamondoids were determined to be in the range of 0.06-0.14 microg/g oil. Distributions of diamondoids in over 100 different oils and refined products were quantitatively compared. The concentrations of four groups of target biomarkers were found, in general, to decrease in the order of sesquiterpanes > terpanes and steranes > adamantanes > diamantanes in both crude oils and refined products. A number of indices of admantanes and diamantanes have been developed and assessed as source indicators using their diagnostic powers (DP). The effects of evaporative weathering and biodegradation on alteration of diamondoid distributions have been quantitatively investigated. Finally, a spill case study by statistical evaluation of diagnostic ratios using the "two-tailed" Student's tapproach is presented to illustrate the unique utility of diamondoids for correlation and differentiation of unknown spilled diesels.     

用C_1柱的反相液相色谱对辛基酚聚氧乙烯醚型非离子表面活性剂快速分离和测定其氧乙烯聚合物分布(英)(待续)

提出了一个迅速、简单、可重复进行的反相ＨＰＬＣ法, 用来分离和定性辛基酚聚氧乙烯醚表面活性剂的各种齐聚物组分。使用一支Ｃ１ 三甲基硅烷基（ＴＭＳ） 色谱柱得到很高的分离度和灵敏度。本方法对聚乙氧基化的辛基酚聚氧乙烯单元直到４０ 的ＰＥＯＰ表面活性剂（ 摩尔质量分布大约达到２０００） 进行了成功的分离和鉴定。８ 种ＰＥＯＰ表面活性剂的齐聚物分布的情况给予了计算和图形描述。对流动相组成和制备所用的溶剂对齐聚物分离影响进行了详细的研究。     

Character sets of today and tomorrow

This paper reviews the character sets used in today's computer systems and discusses character sets for future computer systems. Some newer Latin-based character sets are introduced and compared in terms of their suitability for information interchange and information processing. Finally, the character set most appropriate for use in future computer systems is suggested.     

Accelerated solvent extraction (ASE) of environmental organic compounds in soils using a modified supercritical fluid extractor

Accelerated solvent extraction (ASE) has been applied to the quantitative extraction of a selected list of semi-volatiles, which include polycyclic aromatic hydrocarbons (PAHs), phenols, polychlorinated biphenyls (PCBs) and total petroleum hydrocarbons. Two conventional supercritical fluid extraction (SFE) systems, the Suprex Prep Master and SFE/50 systems have been modified to function as ASE systems. Using solvent instead of supercritical fluid, extraction in an enclosed system proceeded under high pressure and temperature. Parameters such as extraction temperature and effect of modifiers were investigated. Although limited by a 150 degrees C maximum oven temperature, effective extraction could be carried out in less than 25 min for all the compounds studied. The technique was applied to a variety of real matrices contaminated with hydrocarbons, PAHs and phenols. Validations of the technique were performed using standard reference materials. Recoveries for these matrices were good (>75%) and precision (R.S.D.) was generally less than 10%. Primarily a rapid field extraction technique, comparison with other rapid extraction such as sonication and microwave assisted extraction (MAP) were made. Recoveries were found to be comparable to MAP and superior to sonication. On the present ASE system, only sequential extraction can be carried out but given the rapid nature of the process, about 15 samples can be carried out in a working day.     

Modeling evaporation using models that are not boundary-layer regulated

Experimentation shows that oil is not strictly air boundary-layer regulated. The fact that oil evaporation is not strictly boundary-layer regulated implies that a simplistic evaporation equation suffices to describe the process. The following processes do not require consideration: wind velocity, turbulence level, area, thickness, and scale size. The factors important to evaporation are time and temperature. The equation parameters found experimentally for the evaporation of oils can be related to commonly available distillation data for the oil. Specifically, it has been found that the distillation percentage at 180 degrees C correlates well with the equation parameters. Relationships have been developed enabling calculation of evaporation equations directly from distillation data: percentage evaporated = 0.165 (%D)ln(t) where %D is the percentage (by weight) distilled at 180 degrees C and t is the time in minutes. These equations were combined with the equations generated to account for the temperature variations: percentage evaporated = [0.165(%D)+0.045(T-15))ln(t) The results have application in oil spill prediction and modeling. The simple equations can be applied using readily available data such as sea temperature and time. Old equations required oil vapour pressure, specialized distillation data, spill area, wind speed, and mass transfer coefficients, all of which are difficult to obtain.