Ionization Detection System Research Articles

Fatty acid composition of two small fish in the Gyda River (Kara Sea Basin, Northwestern Siberia, Russia)

The fatty acid composition of the flesh of rainbow smelt (RS, Osmerus mordax) and ruffe (RF, Gymnocephalus cernuus), two small fish species inhabiting the Gyda River (Siberia, Russia), was assayed using a gas-liquid chromatographic method with an ionization detection system and high efficiency capillary columns. RS was found to be richer in the total fatty acid content than RF (21.5 vs. 7.07 mg g–1). The proportion of saturated fatty acids (SFA) was similar in the fish studied (29.2 % in RS and 29.6 % in RF) whereas the flesh of RS contained a higher proportion of monounsaturated fatty acids, MUFA (42.2 vs. 13.9 %), and a lower proportion of polyunsaturated fatty acids, PUFA (28.6 vs. 56.5 %) than RF. RS is rich in essential n-3 PUFAs (2610 and 2390 μg g–1 for docosahexaenoic and eicosapentaenoic acids, respectively). In RF, the atherogenic index (0.39) and thrombogenic (0.20) index were lower than in RS (0.59 and 0.27, respectively). The fatty acid profile of RS in the study area differed from that reported for the flesh of this species from a Canadian estuary probably due to substantial differences in the diet of RS in these habitats. A comparison among fish species from the Gyda River indicated that in terms of nutrition indices, RS has the highest similarity with the muksun Coregonus muksun while RF is closely related to the northern pike Esox lucius. Based on the results from this study, both RF and RS can be recommended for human consumption. In particular, RS may be used as a replacement for muksun, an overfished species, in the traditional diet of indigenous peoples in northwestern Siberia.

Portable mass spectrometry system: instrumentation, applications, and path to 'omics analysis.

Mass spectrometry (MS) is an information rich analytical technique and plays a key role in various 'omics studies. Standard mass spectrometers are bulky and operate at high vacuum, which hinder their adoption by the broader community and utility in field applications. Developing portable mass spectrometers can significantly expand the application scope and user groups of MS analysis. This review discusses the basics and recent advancements in the development of key components of portable mass spectrometers including ionization source, mass analyzer, detector, and vacuum system. Further, major areas where portable mass spectrometers are applied are also discussed. Finally, a perspective on the further development of portable mass spectrometers including the potential benefits for 'omics analysis is provided.

Method Development for Leachable Furfural Determination in Wood-Based Panels by HPLC-Uv System

Analytical method has been developed and validated to determine free or leachable furfural concentration in wood-based panels. Particleboards obtained from birch wood and suberinic acids binder were chosen as a reference material. Two methods and two solvents were tested. Acetone extracts of the samples were analyzed with gas chromatography (GC) flame ionization detector system. Water extracts were analyzed with high-performance liquid chromatography-ultraviolet spectroscopy (HPLC-UV) system. After the GC data in acetone extracts furfural concentration was below method limit of detection. HPLC-UV data showed that in water extracts furfural concentration was possible to determine. It was concluded that HPLC-UV is suitable and fast method for furfural determination in wood-based panels water extracts.

Evaluation of offline sampling for atmospheric C3-C11 non-methane hydrocarbons

The concentration variation of C3-C11 non-methane hydrocarbons (NMHCs) collected in several types of commercial flexible bags and adsorption tubes was systematically investigated using a gas chromatography-flame ionization detector (GC-FID) system. The percentage loss of each NMHC in the polyvinyl fluoride (PVF) bags was less than 5% during a 7-hr storage period; significant NMHCs loss was detected in aluminum foil composite film and fluorinated ethylene propylene bags. The thermal desorption efficiency of NMHCs for adsorption tubes filled Carbopack B and Carboxen1000 sorbents was greater than 95% at 300℃, and the loss of NMHCs in the adsorption tubes during 20-days storage at 4℃ was less than 8%. The thermal desorption efficiency for C11 NMHCs in the adsorption tube filled with Carbograph 1 and Carbosieve SⅢ absorbents was less than 40% at 300℃, and pyrolysis of the absorbents at 330℃ interfered significantly with the measurements of some alkenes. The loss of alkenes was significant when NMHCs were sampled by cryo-enrichment at -90℃ in the presence of O3 for the online NMHC measurements, and negligible for enrichment using adsorption tubes at 25℃. Although O3 scrubbers have been widely used to eliminate the influence of O3 on NMHC measurements, the loss of NMHCs with carbon numbers greater than 8 was more than 10%. Therefore, PVF bags and adsorption tubes filled Carbopack B and Carboxen1000 sorbents were recommended for the sampling of atmospheric NMHCs.

Research on accounting and detection of volatile organic compounds from a typical petroleum refinery in Hebei, North China

A volatile organic compound (VOC) emissions inventory of the petroleum refinery in Hebei was established. This refinery emits 1859.2 tons of VOCs per year, with wastewater collection and treatment system being the largest emissions source, accounting for 59.6% individually, followed by the recirculating cooling water system (13.4%), storage tanks (11.1%), and equipment leaks (9.4%). Organized and fugitive samples were collected simultaneously for different processes of each emissions source. A total of 100 VOC species were characterized and quantified using a gas chromatography-mass spectrometry/flame ionization detection system. The VOC emissions concentrations and chemical composition of each process were quite different. Most of the processes used alkanes as the main chemome. We concluded from the composite source profile weighted by the amount of VOC emissions that the characteristic species of this petroleum refinery were ethane (15.4%), propylene (11.7%), propane (8.5%), iso-pentane (8.3%), and toluene (4.7%). The ozone (O3) formation potential (OFP) and secondary organic aerosol formation potential (SOAP) were evaluated, and the results indicated that alkenes (mainly propylene) and aromatics (mainly toluene) were the priority control compounds. This study clarifies the current status of VOC emissions in the refinery in terms of emissions intensity, emissions components, and O3 and SOA reactivity. The key emissions sources and species screened provide scientific support for reducing refined emissions from the petrochemical industry.

Quantification of Cellulose Pyrolyzates via a Tube Reactor and a Pyrolyzer-Gas Chromatograph/Flame Ionization Detector-Based System.

Pyrolysis of cellulose primarily produces 1,6-anhydro-β-d-glucopyranose (levoglucosan), which easily repolymerizes to form coke precursors in the heating zone of a pyrolysis reactor. This hinders the investigation of primary pyrolysis products as well as the elucidation of cellulose pyrolysis mechanisms, particularly because of the significant buildup of coke during slow pyrolysis. The present study discusses the applicability of a pyrolysis-gas chromatography/flame ionization detection (Py-GC/FID) system using naphthalene as the internal standard, with the aim of substantially improving the quantification of pyrolyzates during the slow pyrolysis of cellulose. This method achieved quantification of levoglucosan with a yield that was 14 times higher than that obtained from offline pyrolysis in a simple tube reactor. The high yield recovery of levoglucosan was attributed to the suppression of levoglucosan repolymerization in the Py-GC/FID system, owing to the rapid escape of levoglucosan from the heating zone, low concentration of levoglucosan in the gas phase, and rapid quenching of levoglucosan. Therefore, this method facilitated the improved quantification of primary pyrolysis products during the slow pyrolysis of cellulose, which can be beneficial for understanding the primary pyrolysis reaction mechanisms. This method can potentially be applied to other polymeric materials that produce reactive pyrolyzates.

Evaluation of biogenic markers-based phenotyping for resistance to Aphanomyces root rot in field pea

Biogenic volatile organic compounds (VOCs) emitted by plants can reveal information about plant adaptation, defense processes, and biological pathways. Thus, such VOC data may be utilized to capture phenotypic plant responses to the environment. In this study, the main objective was to evaluate the potential of biogenic compounds, including VOCs, to phenotype two pea cultivars, Ariel (susceptible) and Hampton (high levels of partial resistance) for resistance to Aphanomyces root rot disease. Plants were monitored non-destructively for VOC emission at three-time points (15, 20, and 30 days after inoculation, DAI) using dynamic headspace sampling with gas chromatography-flame ionization detection (GC-FID) system, as well as destructively at the end of the experiments, using solvent extraction and pyrolysis of both shoot and root tissues. A non-inoculated control (mock-inoculated with distilled water) was utilized to compare the plant responses within a cultivar. The common chemical peaks between control and inoculated samples of both cultivars (RTcm) were analyzed after normalizing the relative peak intensity of inoculated samples with those of control samples, prior to a comparison between cultivars. In addition, unique chemical peaks (RTuq) present in inoculated samples, but not in control samples were also identified and their relative peak intensities were compared. Among the released green leaf volatiles (RTcm), the normalized relative peak intensity of hexanal emission, at 20 DAI, was higher in Ariel than that of Hampton. In addition, several putative chemical peaks (both RTcm and RTuq), previously known as indicators for disease response, exhibited some differences in their emission rates between pea cultivars in at least one of the time points. The destructive sampling revealed that shoot samples produced more putative unique biomarkers (RTuq) than the root samples. Based on the differences in putative chemical peaks between cultivars, this initial study supports the concept of utilization of biogenic biomarker-based phenotyping in distinguishing levels of resistance in the evaluated pea cultivars. More research is needed to further this approach for phenotyping other plant cultivars. Upon validation, the VOC profile integrated with high-throughput VOC sensing techniques can serve as a novel mechanism for phenotyping disease responses in crops.

Source profiles, emission factors and associated contributions to secondary pollution of volatile organic compounds (VOCs) emitted from a local petroleum refinery in Shandong.

An in-depth study was conducted to quantify and characterize VOC emissions from a petroleum refinery located in Shandong, China. The VOC emission inventory established in this study showed that storage tanks were the largest emission source, accounting for 56.4% of total emissions, followed by loading operations, wastewater collection and treatment system, process vents, and equipment leaks. Meanwhile, the localization factors for refining, storage tanks and loading operations were calculated, which were 1.33, 0.75 and 0.31g VOCs/kg crude oil refined. Furthermore, the characteristics of fugitive and organized emissions were determined for various processes and emission sources using a gas chromatography-mass spectrometry/flame ionization detection (GC-MS/FID) system. Most samples contained mainly alkanes, but the total VOC concentrations and key species varied greatly among processes. The source profile of the refinery, synthesized using the weighted average method, indicated that cis-2-butene (14.5%), n-pentane (10.2%), n-butane (7.4%), isopentane (6.5%) and MTBE (5.9%) were the major species released by this refinery. Assessment of O3 and secondary organic aerosol formation potentials were completed, and the results indicated that cis-2-butene, m/p-xylene, toluene, n-pentane, isopentane, benzene, o-xylene and ethylbenzene were the active species for which treatment should be prioritized.

Commissioning, performance benchmarking, and investigation of alkali emissions in a 10 kWth solid fuel chemical looping combustion pilot

Chemical looping combustion of biomass-sourced fuels (bio-CLC) is a novel bio-energy with carbon capture and storage (BECCS) technology for power and heat generation with net negative CO2 emissions. In this study, a new 10 kWth CLC pilot designed for high-volatiles biomass fuels was commissioned with ilmenite oxygen carrier and five different biomass fuels of varying volatile and alkali content fractions. The system was tested for its ability to convert high and low volatile content biomass, while achieving high carbon capture efficiency. The new pilot achieved carbon capture close to 100% for high-volatiles biomass, and >94% for low-volatiles biomass char fuels. Furthermore, due to the implementation of a volatiles distributor, the new pilot demonstrated an improvement of up to 10 percentage points of gas conversion efficiency for high-volatiles biomass vs. the previous generation reactor. Gaseous alkali emissions were measured with a surface ionization detection system. Flue gas alkali release levels were found to rise with higher fuel alkali content. Alkali emissions were found to be approximately similar in the AR and the FR for all but the straw pellet mixture fuel (highest alkali content fuel). For the straw pellet mixture, gaseous alkali release levels in the AR were up to seven times higher than those of the FR. In all cases, over 96% of the fuel’s alkalis were absorbed by the ilmenite bed material. Ilmenite’s strong alkali absorption characteristics were concluded to be the key determinant of gas-phase release of biomass alkali in the conducted experiments.

Fatty acids of follicular fluid phospholipids and triglycerides display distinct association with IVF outcomes

Research questionAre triglyceride fatty acids in the follicular fluid associated with either follicular fluid phospholipid fatty acids or IVF outcomes and, if so, how are they associated? DesignIn a prospective cross-sectional study, 70 women undergoing intracytoplasmic sperm injection were recruited. Follicular fluid phospholipids and triglycerides were separated by thin-layer chromatography. Fatty acids were measured using gas-liquid chromatography and flame ionization detection system. ResultsSignificant differences in fatty acid composition were observed between follicular fluid phospholipid and triglyceride fractions. Phospholipid stearic acid and n-3 polyunsaturated fatty acids, particularly alpha-linolenic acid, were negatively associated with the number of mature oocytes and cleaved embryos, whereas arachidonic acid was in direct correlation with cleavage rate per IVF cycle (β = 0.325, P = 0.022). In the case of triglyceride fraction, total monounsaturated fatty acids, oleic acid in particular, displayed significantly positive associations with the number of oocytes (β = 0.261, P = 0.043) and embryos (β = 0.310, P = 0.018). Furthermore, cleavage rate correlated inversely with palmitic acid (β = –0.359, P = 0.007) and directly with pentadecanoic acid (β = 0.378, P = 0.005). Most of these associations, however, were not independent of predictive fatty acids belonging to phospholipid fraction, according to multivariate analysis. ConclusionsFatty acid compositions of phospholipid and triglyceride fractions from human follicular fluid differentially correlate with IVF cycle parameters.

A pyrolysis study of allylic hydrocarbon fuels

AbstractThe pyrolysis of selected C3–C5 allylic hydrocarbons has been studied using a single‐pulse shock tube. A new single‐pulse shock tube has been designed and constructed by recommissioning an existing conventional shock tube. This facility enables the investigation of high‐temperature chemical kinetics with an emphasis on combustion chemistry. The modifications performed on the existing shock tube are described, and the details of the sampling system to analyze the species concentration using a gas chromatography‐mass spectrometry‐flame ionization detection (GC‐MS with a flame ionization detector) system are also provided. This facility is characterized and validated by performing cyclohexene pyrolysis experiments. Furthermore, the performance of the shock tube is demonstrated by reproducing previous literature measurements on the pyrolysis of isobutene. Postvalidation, this setup is used to study the pyrolysis of trans‐2‐butene and 2‐methyl‐2‐butene (2M2B). A newly developed mechanism, NUIGMech1.0, is used to simulate the experimental data of propene, isobutene, 2‐butene, and 2M2B, allylic hydrocarbon fuels. A description using two different kinetic simulation approaches is provided using our isobutene experiments as a reference. We found no significant differences between the two methods. Additionally, the contribution of different reaction classes on fuel consumption is detailed and the influence of geometry on fuel consumption and first aromatic ring: benzene is discussed.

Microextraction and gas chromatography–flame ionization determination of five antiepileptic drugs in biological samples using amino acid-based deep eutectic ionic liquids

This study investigated the use of amino acid-based deep eutectic solvents (AADESs) in the ultrasound assisted reverse-phase emulsification microextraction (UARPEME) of five antiepileptic drugs (AEDs) from biological samples. The extraction was performed by dispersing the AADES into the sample solution using ultrasonic irradiation. After completing extraction, the sample solution was centrifuged. Then, the pre-concentrated AEDs in the AADES (upper phase) were derivatized by adding phenyltrimethylammonium hydroxide solution to it. The derivatized analytes were then eluted with n-hexane and it was injected directly into the gas chromatography–flame ionization detection (GC–FID) system to determine target analytes after the methylation reaction inside the injection chamber. The effective parameters of the proposed AADES–UARPEME method that comprises three consecutive extraction, derivatization and elution steps, were optimized using one Taguchi orthogonal array design and two central composite designs and evaluated by analysis of variance. The optimized method was successfully implemented to analyze AEDs in the human biological samples (serum, urine, breast-milk and hair) and acceptable results were obtained. The resultant calibration curves were linear over the concentration range of 0.5–850 μg/L (R2 > 0.998). The estimated limits of detection and quantification were lower than 0.5 μg/L and the improvement factors were between 1378 and 1409. The intra- and inter-day repeatability values varied below 5.3% (n = 5) and the relative recovery values were calculated between 90 and 110% for all samples.

Characterization of Odor-Active Compounds, Polyphenols, and Fatty Acids in Coffee Silverskin.

For the first time the volatile fraction of coffee silverskin has been studied focusing on odor-active compounds detected by gas chromatography-olfactometry/flame ionization detector (GC-O/FID) system. Two approaches, namely headspace (HS) analysis by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and odor-active compounds analysis by gas chromatography-olfactometry/flame ionization detector (GC-O/FID), have been employed to fully characterize the aroma profile of this by-product. This work also provided an entire characterization of the bioactive compounds present in coffee silverskin, including alkaloids, chlorogenic acids, phenolic acids, flavonoids, and secoiridoids, by using different extraction procedures and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) system. Coffee silverskin was shown to be a good source of caffeine and chlorogenic acids but also of phenolic acids and flavonoids. In addition, the fatty acid composition of the coffee silverskin was established by GC-FID system. The results from this research could contribute to the development of innovative applications and reuses of coffee silverskin, an interesting resource with a high potential to be tapped by the food and nutraceutical sector, and possibly also in the cosmetics and perfumery.

A Spatial-Temporal Resolved Validation of Source Apportionment by Measurements of Ambient VOCs in Central China.

Understanding the sources of volatile organic compounds (VOCs) is essential in the implementation of abatement measures of ground-level ozone and secondary organic aerosols. In this study, we conducted offline VOC measurements at residential, industrial, and background sites in Wuhan City from July 2016 to June 2017. Ambient samples were simultaneously collected at each site and were analyzed using a gas chromatography–mass spectrometry/flame ionization detection system. The highest mixing ratio of total VOCs was measured at the industrial site, followed by the residential, and background sites. Alkanes constituted the largest percentage (>35%) in the mixing ratios of quantified VOCs at the industrial and residential sites, followed by oxy-organics and alkenes (15–25%).The values of aromatics and halohydrocarbons were less than 15%. By contrast, the highest values of oxy-organics accounted for more than 30%. The model of positive matrix factorization was applied to identify the VOC sources and quantify the relative contributions of various sources. Gasoline-related emission (the combination of gasoline exhaust and gas vapor) was the most important VOC-source in the industrial and residential areas, with a relative contribution of 32.1% and 40.4%, respectively. Industrial process was the second most important source with a relative contribution ranging from 30.0% to 40.7%. The relative contribution of solvent usage was 6.5–22.3%. Meanwhile, the relative contribution of biogenic emission was only within the range of 2.0–5.0%. These findings implied the importance of controlling gasoline-related and industrial VOC emissions in reducing the VOC emissions in Wuhan.

Fused-silica capillary internally modified with nanostructured octadecyl silica for dynamic in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons from aqueous media

The internal surface of a fused-silica capillary was made much more porous, more adsorptive and resistant to chemical and mechanical stresses by chemical coating using nanostructured octadecyl silica particles. The modification process was conducted using a simple and green nucleosynthesis procedure. The internally modified capillary was used as an in-tube solid-phase microextraction (IT-SPME) device for the extraction and preconcentration of ultratrace levels of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples, followed by determination using gas chromatography-flame ionization detection (GC-FID) system. Morphology and structure of the sorbent was characterized by FT-IR, SEM and energy dispersive X-ray techniques. The effects of a range of experimental variables on the efficiency of the IT-SPME-GC-FID method were evaluated and optimized. Under the optimal conditions, good linearity (R2 > 0.99) was obtained for the calibration graphs over the range of 1–4000 ng mL−1. Detection limits were 0.22–0.47 ng mL−1 and relative standard deviations were obtained in the range 4.4–10.3%. Recoveries of the spiked samples were found to be 78.7–103.5%. The proposed IT-SPME-GC-FID strategy was applied successfully for the analysis of PAHs in real water samples. The results demonstrated good analytical performances, compared with those reported elsewhere for the sampling and quantification of PAHs in aqueous media.

Catalytic pyrolysis of hemicellulose to produce aromatic hydrocarbons

Catalytic fast pyrolysis of hemicellulose with zeolite catalysts is a promising method to produce aromatic hydrocarbons (Carlson et al. 2009). In this paper, the behavior of hemicellulose catalytic pyrolysis with HZSM-5 (with three different silica to alumina ratio, 23, 50, 80), HY, and Hβ was studied. Pyrolysis vapor was separated into non-condensable vapors and condensable fractions. The fractions were qualified and quantified by a gas chromatography / flame ionization detector (GC/FID) system and a gas chromatography / mass spectrometer (GC/MS) system, respectively. The influences of catalysts and pyrolysis parameters were studied. Among the catalysts, HZSM-5(23) provided the desired acidity and shape selectivity for aromatic hydrocarbon production. A higher catalyst to hemicellulose ratio (CHR) and higher heating rate resulted in a higher aromatic hydrocarbon yield. The most suitable pyrolysis temperature for hemicellulose with HZSM-5 was 650 °C. During catalytic pyrolysis, thermal decomposition products underwent deoxygenation reactions promoted by the acid sites on the zeolite. The C2-C4 deoxygenated products produced monocyclic aromatic hydrocarbons (MAH) by shape-selective catalysis reactions in zeolite pores. With higher temperatures and higher residence times, monocyclic aromatic hydrocarbons facilitated cyclization reactions with C2-C4 deoxygenated products, thereby forming polycyclic aromatic hydrocarbons (PAH).

Composition and Atmospheric Reactivity of Ambient Volatile Organic Compounds(VOCs)in the Urban Area of Nanjing, China

Online gas chromatography with flame ionization detection (GC-FID) systems were employed to observe 56 species of volatile organic compounds (VOCs) in the environmental atmosphere in Nanjing in 2015. The results showed that the annual volume fraction of VOCs was (17.49±11.35)×10-9. The highest concentration of VOCs was in April (22.21×10-9), and the lowest in July (12.39×10-9). Diurnal values of VOCs concentration had no obvious variations. Alkanes, alkenes, aromatics, and acetylene accounted for 56.51%, 11.06%, 24.62%, and 7.81%, respectively. Propane (15.26%), ethane (14.14%), acetylene (7.81%), toluene (6.97%), n-butane (6.23%), ethylene (5.23%), isobutane (4.34%), propylene (4.13%), isoprene (4.12%), and m/p-xylene (4.06%) were the most abundant VOCs species. The average ratio of toluene/benzene (T/B) was 2.02, indicating that the atmospheric VOCs were mainly affected by emissions of motor vehicles, especially gasoline vehicles. The average ratio of ethane/ethyne (E/E) was 2.24, showing that the plume had aged. The hydroxyl radical (·OH) loss rate(L·OH) and ozone formation potential(OFP)were applied to assess the chemical reactivity of VOCs. The atmospheric activity of VOCs was higher in the winter and spring than in the summer and autumn. Aromatics and alkenes were the most important contributors to L·OH and OFP. Their contributions to L·OH and OFP were 46.96% and 41.58%, and 33.73% and 39.86%, respectively. Propylene, ethylene, and xylene were the most active species.

One-Year Characterization and Reactivity of Isoprene and Its Impact on Surface Ozone Formation at A Suburban Site in Guangzhou, China

Isoprene has a potentially large effect on ozone (O3) formation in the subtropical, highly polluted city of Guangzhou. Online measurements of isoprene in Guangzhou city are scarce; thus, isoprene levels were monitored for one year at the Guangzhou Panyu Atmospheric Composition Station (GPACS), a suburban site in Guangzhou, using an online gas chromatography-flame ionization detector (GC–FID) system to investigate the characterization and reactivity of isoprene and its effect on the O3 peak profile in different seasons. The results showed that the daily average mixing ratios of isoprene at GPACS were 0.40, 2.20, 1.40, and 0.13 mixing ratio by volume (ppbv) in spring, summer, autumn, and winter, respectively. These values were considerably higher than the mixing ratios of isoprene in the numerous other subtropical and temperate cities around the world. Furthermore, isoprene ranked first with regard to O3 formation potential (OFP) and propylene-equivalent mixing ratio among 56 measured non–methane hydrocarbons (NMHCs). The ratios of isoprene to cis-2-butene, an exhaust tracer, were determined to estimate the fractions of biogenic and anthropogenic emissions. The results revealed a much greater contribution from biogenic than anthropogenic factors during the daytime in all four seasons. In addition, night-time isoprene emissions were mostly associated with vehicles in winter, and the residual isoprene that remained after photochemical loss during the daytime also persisted into the night. The high levels of isoprene in summer and autumn may cause the strong and broad peaks of the O3 profile because of its association with the most favorable meteorological conditions (e.g., high temperature and intense solar radiation) and the highest OH mixing ratio, which could affect human health by exposing people to a high O3 mixing ratio for prolonged periods. The lower mixing ratios of isoprene resulted in a weak and sharp peak in the O3 profile in both spring and winter. The high level of isoprene in the subtropical zone could accentuate its large impact on atmospheric oxidant capacity and air quality in Guangzhou city.

Compact prototype GC-PID system integrated with micro PC and micro GC column

In this work, a portable gas chromatography (GC) photo ionization detector (PID) system integrated with a micro column and a micro pre-concentrator (PC) was developed for GC application. The micro pre-concentrator filled with single walled-carbon-nanotubes as adsorption material was able to concentrate trace gas. Different from conventional GC column, the micro GC column was able to completely separate the gas mixtures, dramatically reducing volume of GC system. The experimental results indicate that the microfabricated compact prototype GC PID system demonstrated high repeatability of 0.42% and low detection limit of less than 1 ppb to rapidly detect volatile organic compounds (VOCs).

Estimation of Dietary Intake Concentration of Polycyclic Aromatic Hydrocarbon (PAH) Carcinogens from <i>Tilapia zilli</i> Commercially Available from Escravos River, Nigeria

The Concentrations of Polycyclic Aromatic Hydrocarbons in the organs of a commonly consumed Tilapia zilli from Escravos River in Delta State, Nigeria were evaluated to ascertain the level of their bioaccumulation and the possible human health risks associated with their consumption. Samples were analysed with a Gas Chromatographic Flame Ionization Detector system and results were subjected to a one-way Analysis of Variance (ANOVA) to test for the significant level of the parameters across the groups. The level of significance was above 95% and the results were presented as mean ± standard error. The values of PAHs reported followed different trends. The muscle had the highest average concentration (313.43±1.64 mg/kg) followed by kidney (266.72±0.36 mg/kg) and the liver (266.17±0.81 mg/kg) while the gills had the lowest average concentration (192.96±1.09 mg/kg). The average concentrations of PAH reported in this research are highly above the EU recommended benchmark (2 µg/kg). The reported ailments from the communities cut across Escravos river could be traced to long term exposure of humans to these polycyclic aromatic hydrocarbons in the sea foods which are transferred into their food chain because of their high level of dependency for protein source.