Detection limits polycyclic aromatic hydrocarbons

Electrochemical immunosensors have been widely used for environmental analysis in amperometric, potentiometric, and conductimetric configurations. Amperometric immunosensors measure the current generated by oxidation or reduction of redox substances at the electrode surface, which is held at an appropriate electrical potential. Wilmer et al. measured concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) in water by using an amperometric immunosensor with a limit of detection of 0.1 Jtg L-1 (Wilmer et al., 1997). Some examples of new developments are the disposable screen-printed electrodes for the detection of polycyclic aromatic hydrocarbons (PAHs)... 

Because process mixtures are complex, specialized detectors may substitute for separation efficiency. One specialized detector is the array amperometric detector, which allows selective detection of electrochemically active compounds.23 Electrochemical array detectors are discussed in greater detail in Chapter 5. Many pharmaceutical compounds are chiral, so a detector capable of determining optical purity would be extremely useful in monitoring synthetic reactions. A double-beam circular dichroism detector using a laser as the source was used for the selective detection of chiral cobalt compounds.24 The double-beam, single-source construction reduces the limitations of flicker noise. Chemiluminescence of an ozonized mixture was used as the principle for a sulfur-selective detector used to analyze pesticides, proteins, and blood thiols from rat plasma.25 Chemiluminescence using bis (2,4, 6-trichlorophenyl) oxalate was used for the selective detection of catalytically reduced nitrated polycyclic aromatic hydrocarbons from diesel exhaust.26... 

Limited data is available on the concentration of volatile organic compounds, semi-volatile organic compounds (SVOCs), and polycyclic aromatic hydrocarbons (PAHs) from gasification processes. The data that is available indicate that VOCs, SVOCs, and PAHs are either non-detectable in flue gas streams from IGCC process or, in some cases where they were detected, they are at extremely low levels (on the order of parts per billion and lower). The analysis of syngas also indicates greater than 99.99 percent chlorobenzene and hexachlo-robenzene destruction and removal efficiencies and part per billion or less concentration of selected PAHs and VOCs.9-14... 

According to the vendor, Cement-Lock technology has successfully removed polycyclic aromatic hydrocarbons (PAHs), PCBs, and tetrachlorodibenzo-1,4-dioxin (TCDD)/2,3,7,8-tetra-chlorodibenzofuran (TCDF) from soils and sediments in bench-scale tests. Metal concentrations were also reduced below detection limits in bench-scale tests. These metals included arsenic, cadmium, chromium, lead, nickel, mercury, and silver. 

Moreover, the sensitivity of biosensors containing Sphingomonas sp. or Pseudomonas fluorescens allowed the specific determination of the polycyclic aromatic hydrocarbon (PAH) naphthalene, although both biosensors showed relatively high responses to salicylate and acetate [117]. However, the remarkably low limit of detection obtained by these biosensors of 10 pg 1" naphthalene was not sufficient for the monitoring of drinking water, due to the prescribed upper limit for the concentration of PAH in drinking water of 0.2 pg 1". ... 

In the EU Directive on Drinking Water Quality [35], 23 individual chemical parameters have specific limits together with two group limits for polycyclic aromatic hydrocarbons and pesticides. In the case of pesticides, no individual pesticide is permitted to exceed 0.1 pgL , and pesticides in total should not exceed 0.5 xgL" . These limits were a compromise, the original demand having been for a zero limit for pesticides in drinking water, and these standards were set, in 1998, as the effective analytical detection limit. The revision of this directive and its application to pharmaceuticals is currently under discussion, although it seems unlikely that specific limits will be set for individual pharmaceuticals [36]. 

Various workers [23-32] have studied the application of high performance liquid chromatography to the determination of PAHs in water samples. Hagenmaier et al. [31] used a reversed phase high-pressure liquid chromatography procedure for the determination of trace amounts of polycyclic aromatic hydrocarbons in water. Different column packing materials were tested, in conjunction with non polar stationary phases of various polarities, for separation efficiency, detection limits and long-term stability. The method was suitable for concentrations as low as 2ng L 1 in a IL sample. Compounds... 

Other approaches already realized include the development of a simple and rapid method for spironolactone determination based on the quenching of the fluorescence of CdSe quantum dots by the analyte52 or the determination of anthracene with a detection limit of 1.6 x 10-8 M based on the quenching effect of this polycyclic aromatic hydrocarbon on water-soluble CdSe/ZnS quantum dots, prepared via a simple sonochemical procedure using (3-cyclodextrin ((3-CD) as surface coating agent.53... 

Specific requirements for the end products include tests and migration limits for various types of toxic or harmful compounds such as Michler s ketone (4,4 bis(dimethylamino)benzophenone), 4,4 bis(diethylamino) benzophenone (DEAB), diisopropyhiaphthalenes (DIPNs) phthalates, solvents, partially hydrogenated terphenyls (HTTP), azo colourants, fluorescent whitening agents, primary aromatic amines, polycyclic aromatic hydrocarbons (PAH) and benzophenone. The amounts of these substances should be either below the detection limits or, in some cases (DIPN, HTTP, solvents) as low as can be reasonably achieved. For benzophenone a specific migration limit of 0.1 mg/dm is defined. The requirements generally apply to products intended to be used in contact with aqueous and/or fatty foodstuffs or also with dry, non-fatty foodstuffs (requirements for DIPNs, HTTP, phthalates and solvents). 

Polycyclic aromatic hydrocarbons have been encountered in different environmental matrices (e.g., soil, atmosphere, water, biota, etc.). Because PAHs have natural fluorescent properties, LC-FLD is advantageous over GC-MS because of its ability to measure the different PAH isomers and comparable detection limits are obtained. LC-DAD and LC-APCI-MS can also be applied and have the advantage... 

Supercritical fluid chromatography (SFC) with ELD, using CO2 or C02-MeOH as mobile phase, was applied to simultaneous determination of 11 priority phenols and 13 polycyclic aromatic hydrocarbons. Voltammetric measurements allow low-nanogram detection limits of reducible and oxidizable analytes, even if they elute simultaneously from the chromatographic column . SFC with MeOH-modified CO2 was performed under isobaric and pressure-programmed conditions, combined with ELD. LOD was 250 p,g of 2,6-dimethylphenol for oxidative ELD and 100 pg of 1,3-dinitrobenzene for reductive ELD . Various sorbents were investigated for SPE preconcentration prior to SFC 20 . 

Because of the large scale dilution of contaminants in the aquatic matrices, concentrations of many organic pollutants are below the detection limits of standard analytical and sampling methods. Thus, gas chromatography with specific detection methods such as electron capture detector and HPLC has been frequently used for analysis of pesticides and polycyclic aromatic hydrocarbons in water and biological samples. 

Formation, factors affecting concentrations, legal limits and occurrence of polycyclic aromatic hydrocarbons in smoked meat products and smoke flavor additives are briefly reviewed by Simko. The most widely employed techniques such as thin-layer chromatography (TLC), gas chromatography (GC), and high-performance liquid chromatography (HPLC) are evaluated. Moreover, sample preparation, pre-separation procedures, separation and detection systems being used for the determination have been evaluated with emphasis on the latest developments in applied food analysis and... 

The results of PAH analysis with different types of interfaces (e.g. ESI, APCI, PBI and TSP - were reported by Clench et al. reviewing the state of the art of various mass spectral techniques [28]. For more polar PAHs pneumatically assisted ESI-LC-MS was used to determine mixtures of hydroxy polycyclic aromatic hydrocarbons. The abundance of ions dependent on flow rates was shown. ESI inonization was found to be less sensitive compared to APCI ionisation [304]. PAH analysis with ESI-LC-MS combined with RP-LC with post-column addition of silver nitrate was applied for the determination of 10 PAHs in river water. PAHs resulted in [Mj and [M-i-Ag]. The detection limits of different PAHs in spiked samples ranged from 0.001 to 0.03 pg L [442]. 

We have demonstrated that polycyclic aromatic hydrocarbons can be rapidly measured by using the DNA intercalation -fluorescence technique. The limits of detection obtained are sensitive enough to be used for measurements on environmental carcinogens Future studies will utilize evanescent wave technology with fiber optics and immobilized DNA to develop a portable real time instrument for in situ measurements of carcinogens.. 

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