A rapid method for the clean-up of chlorinated biphenyls (CBs) isolated from environmental samples

The use of silicalite, a zeolitic form of silica, is suggested as a means of purifying samples prior to the determination of chlorinated biphenyls (CBs), particularly those which are heavily contaminated with petroleum derived n-alkanes. Experiments using mussel, fish and sediment extracts show that CBs are recovered quantitatively after silicalite treatment of lipid extracts.     

Effects of Protein on the Detection of Chlorobenzenes in Fish and Their Elimination by Modified QuEChERS Method

Molecular fluorescence spectrometry, resonance Rayleigh scattering and gas chromatography-mass spectroscopy（GC-MS） were used to study the effect of pure fish serum albumin（FSA） as the model protein on the extraction of three chlorobenzenes（CBs： 1,3-DCB, 1,2-DCB and 1,2,4-TCB; DCB=dichlorobenzene; TCB=trichlorobenzene） in fish samples. The results show that there was a strong binding effect between CB and FSA. In an aqueous solution of 90%（volume fraction） acetone, a slow but full protein denaturation might take place, which would cause the unfolding of protein and the releasing of CBs. Based on these results, a QuEChERS（quick, easy, cheap, effective, rugged and safe） method was modified by replacing the traditional acetonitrile with acetone aqueous solution in the present work. This modified QuEChERS method was applied in the determination of CBs in fish samples. The spiked recoveries and the limits of detection were 80.4%--118.3% and 2.4--7.3 ng/g, respectively. This paper proposes a new strategy by slowing down the protein denaturation and releasing bound organic compounds to enhance the extraction efficiency of CBs in fish samples.     

Analysis of seven chlorobiphenyl congeners by multidimensional gas chromatography

Chlorobiphenyl congeners (CBs) are used as indicator compounds in analysis performed to determine whether or not PCB concentrations in food products, waste mineral oil, and environmental samples comply with the maximum levels permitted by legislation. Seven of these compounds have been checked for coelution with other CB congeners by means of a multidimensional gas chromatographic method utilizing a combination of two narrow bore columns, one coated with a conventional non-polar stationary phase and the other with a liquid crystalline (smectic) stationary phase. Peaks of the relevant CBs have been transferred, by heart cutting, from the non-polar column to the liquid crystal column, on which unambiguous separation from possible coeluting CB congeners was obtained. It has been shown that if the seven congeners are analyzed solely on a single, non-polar capillary column the results obtained for two of them may be affected by coelution of other compounds.     

Evaluation of dialysis as a technique for the removal of lipids prior to the GC determination of ortho- and non-ortho-chlorobiphenyls, using 14C-labelled congeners.

Dialysis was evaluated as a non-destructive clean-up technique to isolate chlorobiphenyls (CBs) from fish-oil prior to further analysis. 14C-CBs were used to study the transfer processes of the CBs across polyethylene membranes. Single step processes using equilibrium dialysis were compared to a dynamic method of refluxing solvent. The dynamic method reduced the duration of the separation to 8 h. The transfer of CBs and the lipids was dependent on temperature and nature of the analyte with smaller molecules being dialysed substantially faster than larger molecules. An optimised dynamic method was used to compare the dialytic clean-up with a traditional method using sulfuric acid-impregnated silica for the determination of CBs in a laboratory reference material. Labelled recovery standards for each individual congener are recommended in combination with dialysis as a method for clean-up.     

Preparation and evaluation of a molecularly imprinted sol-gel material for on-line solid-phase extraction coupled with high performance liquid chromatography for the determination of trace pentachlorophenol in water samples

A highly selective imprinted amino-functionalized silica gel sorbent was prepared by combining a surface molecular imprinting technique with a sol-gel process for on-line solid-phase extraction-HPLC determination of trace pentachlorophenol (PCP) in water samples. The PCP-imprinted amino-functionalized silica sorbent was characterized by FT-IR, SEM, nitrogen adsorption and the static adsorption experiments. The imprinted functionalized silica gel sorbent exhibited high selectivity and offered a fast kinetics for the adsorption and desorption of PCP. The prepared sorbent was shown to be promising for on-line solid-phase extraction for HPLC determination of trace levels of PCP in environmental samples. With a sample loading flow rate of 5 ml min(-1) for 2 min, an enhancement factor of 670 and a detection limit (S/N = 3) of 6 ng l(-1) were achieved at a sample throughput of five samples h(-1). The precision (RSD) for nine replicate on-line sorbent extractions of 10 microgl(-1) PCP was 3.8%. The sorbent also offered good linearity (r = 0.9997) for on-line solid-phase extraction of trace levels of PCP. The method was applied to the determination of PCP in local lake water, river water and wastewater samples.     

Development of a rapid method for the detection of cocoa butter equivalents in mixtures with cocoa butter

A simple and rapid gas chromatographic (GC) method was developed for the detection of cocoa butter equivalents (CBEs) in cocoa buffer (CB). It is based on the use of a 5 m nonpolar capillary column for the separation of the main triglycerides of CB according to their acyl/carbon numbers. The GC procedure was optimized to avoid thermal degradation of the triglycerides. By computing the ratio C54/C50 and (C54/C50) x C52 and by 2-dimensional plotting of these values, authentic CB samples were clearly distinguished from samples containing various CBEs. The detection of little as 1% CBE in CB (corresponding to about 0.3% CBE in chocolate) in a model system was shown to be possible. Under real conditions, for a wide range of CBs, about 2.5% CBEs in CB were detected. With this method, quantitation was possible at a concentration of 5% CBEs in CB mixtures, which corresponds to around 1% in chocolate; this value is far below the maximum level of 5% CBEs allowed to be added to chocolate.     

A collaborative study for intermethod comparison

A collaborative study for the determination of vinclozolin and captan in lettuce and pears was conducted in the author's laboratory. In two 3-day courses the participants of twelve laboratories analysed the samples by the micro on-line method and two macro methods for intermethod comparison. The pesticides were determined by GC-ECD after clean-up on silica gel deactivated by 10% water. The results of the micro method are well comparable with those of the macro methods. Therefore, the macro extraction methods can be substituted by the micro on-line method.     

不同取代度纤维素苯甲酸酯负载钌纳米簇催化苯加氢反应

以纤维素为原料、苯甲酰氯为酯化剂的条件下合成了纤维素苯甲酸酯(CB), 通过控制苯甲酰氯的量得到了不同取代度的CB, 且不同取代度的CB 在苯、环己烯和环己烷中的溶胀度不同. 将CB 与正丁醇还原得到的单分散Ru 纳米簇进行杂化后得到Ru/CB 杂化膜, 并将其用于催化苯选择加氢反应. 利用傅立叶转换红外光谱仪, X-射线光电子能谱,X-射线衍射和透射电子显微镜对不同取代度的CB 和杂化膜的结构与性能进行了表征. 研究发现, 杂化膜的溶胀度是影响苯的转化率和环己烯选择性的重要因素. 活性评价结果表明, 苯的转化率随着取代度的增大而增大, 最高为2.8%;环己烯的选择性随取代度的增大而减小, 最高为53.4%.     

Determination of atropisomeric and planar polychlorinated biphenyls, their enantiomeric fractions and tissue distribution in grey seals using comprehensive 2D gas chromatography

High prevalence of uterine occlusions and sterility is found among Baltic ringed and grey seal. Polychlorinated biphenyls (CBs) are suspected to be the main cause. The CB concentrations are higher in affected than in healthy animals, but the natural variation is considerable. Thus, it might be possible to assess the health status of seals by CB analysis. The ratios of chiral compounds (enantiomeric fractions (EFs)) such as atropisomeric CBs are of particularinterest, since these may reflect differences in metabolic rates. An analytical procedure was developed and used to determine the levels of atropisomeric CBs, planar-CBs (WHO-PCBs) and total CBs in seals of different health status. Comprehensive 2D gas chromatography (GC x GC) was used to separate the target analytes from other CBs and interferences and a micro electron-capture detector (microECD) was used for detection. EFs of the atropisomeric CBs were difficult to determine as the levels were low and the interferences many. Two column combinations bad to be used to avoid biased results-both had a chiral column as first-dimension column. The second-dimension column was coated with either a high-polarity cyanopropyl or a liquid crystal phase. EFs were determined for five atropisomeric CBs, i.e. CBs 91,95, 132, 149 and 174. The results were verified by GC x GC-time-of-flight mass spectrometry (TOF-MS). Some atropisomeric CBs had EFs that deviated strongly from the racemic-mixture value. The deviations were larger in liver than blubber, which indicates enantioselective metabolism. However, there was no selective passage of the studied atropisomeric CBs across placenta and no selective blood-brain barrier. Similarly, no correlation between EFs and health status was observed, although there was a correlation between the total CB levels and health status.     

Screening and confirmation of PAHs in vegetable oil samples by use of supercritical fluid extraction in conjunction with liquid chromatography and fluorimetric detection

A fast, simple, non-destructive method for the direct screening of polycyclic aromatic hydrocarbons (PAHs) in vegetable oil samples is proposed. The method uses a supercritical fluid extraction (SFE) system coupled on-line with a fluorimetric detector to determine PAHs. This special assembly avoids the main problems encountered in the determination of PAHs in complex matrices such as vegetable oils. PAHs are selectively extracted by using silica gel in the thimble and cleaned up by passage through a C18 column. Interferences are preferentially retained by the silica gel during the SFE process while PAHs are adsorbed in the C18 column and the remainder of the matrix is sent to waste. Finally, the C18 column is purged to remove residual CO₂ gas and adsorbed PAHs are recovered by desorption with a solvent. The extracts from positive samples are subsequently analyzed by liquid chromatography (LC) with fluorescence detection. The proposed method allows the confirmation of vegetable oil safety and hence provides a new tool for consumer protection.     

Comprehensive two-dimensional gas chromatography of the 209 polychlorinated biphenyls

Comprehensive two-dimensional gas chromatography (GC x GC) of the 209 polychlorinated biphenyls (CBs) was carried out using a longitudinally modulated cryogenic system (LMCS) and liquid carbon dioxide as cryogen. The effluent from a non-polar column was modulated and further separated on either a polar or a shape-selective second-dimension column. Five GC x GC column combinations were evaluated, with DB-XLB as the first column in each case. DB-XLB separates more congeners than any other GC column currently available. When combined with a biscyanopropyl siloxane (SP-2340 or BPX70) or smectic liquid crystal (LC-50) second-dimension column in a GC x GC system many additional CBs can be separated. In total, 176 and 181 of the 209 congeners were separated (Rs = 0.5) on the column combinations DB-XLB/SP-2340 and DB-XLB/LC-50, respectively. Of the 136 CBs present in any Aroclor mixture at concentrations greater than 0.05% (w/w), 126 were resolved using either of these two column combinations. The seven frequently measured CBs 28, 52, 101, 118, 138, 153, 180, and the WHO-PCBs 77, 81, 105, 114, 118, 123, 126, 156. 157, 167, 169 and 189 were all separated from Aroclor CBs on the DB-XLB/LC-50 column set, whereas CBs 118 and 131 coeluted on the DB-XLB/SP-2340 column set. In addition, three technical CB formulations (Aroclors 1232, 1248 and 1260) and a seal blubber sample (Halichoerus grypus) from the Baltic Sea were analyzed. Similar peak patterns were found for Aroclor 1260 and the CBs in the seal blubber, facilitating use of this technical CB formulation to identify the CBs in the blubber by GC x GC. Individual CBs in environmental samples, such as seal blubber, may be identified semi-automatically by matching the samples GC x GC profiles to a template generated using a standard containing all 209 CBs. Using such a template, 64 CBs were identified in the grey seal blubber sample.     

Phenyl‐functionalized silica‐coated magnetic nanoparticles for the extraction of chlorobenzenes,and their determination by GC‐electron capture detection

We have prepared a solid phase for the extraction of chlorobenzenes (CBs) by coating magnetic (Fe₃O₄) nanoparticles with silica via a sol‐gel process using a mixture of tetraethoxysilane and triethoxyphenylsilane. The nanoparticles were characterized by SEM, energy‐dispersive spectroscopy, and X‐ray diffractometry. The nanoparticles were used for the extraction of 1,4‐dichlorobenzene (1,4‐DCB), 1,2,3‐trichlorobenzene (1,2,3‐TCB), 1,2,4‐trichlorobenzene (1,2,4‐TCB), and 1,2,3,4‐tetrachlorobenzene (1,2,3,4‐TeCB) from water, followed by their determination by GC‐electron capture detection. Under optimal conditions, enrichment factors ranging from 220 to 360 were obtained. All determination coefficients (r²) are >0.99, and linear response is found in range 0.025–1.5 μg/L (at the lower end), and 6–120 μg/L (at the higher end). Detection limits are 6, 10, 11, and 500 ng/L for 1,2,3,4‐TeCB, 1,2,4‐TCB, 1,2,3‐TCB, and 1,4‐DCB, respectively. All RSDs are <6% (for n = 5). The method was successfully applied to the determination of CBs in environmental water samples.     

Improved capillary electrophoretic separation of nine (fluoro)quinolones with fluorescence detection for biological and environmental samples

A capillary electrophoretic method has been developed for the separation of nine (fluoro)quinolones. Detection is done by fluorescence measurement with broad wavelength band excitation between 240 and 400 nm. Best separation is achieved in a carrier electrolyte containing 50 mM H3PO4 adjusted to pH 7.55-acetonitrile (60:40, v/v). Detection limits are in the low microgl(-1) range. The suitability to real samples has been demonstrated by analyzing blood samples and surface water samples. Sample preconcentration and sample clean-up can easily be done by solid-phase extraction. Different phases based on alkyl- or phenyl-modified silica as well as on polymers have been investigated for this purpose. The method should also be useful for determination of residues of (fluoro)quinolones in food or other matrices.     

Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching

Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

A simple and fast method for the simultaneous determination of polychlorinated biphenyls and polybrominated diphenyl ethers in small volumes of human serum

A fast extraction and clean-up method for the simultaneous determination of PCBs and PBDEs has been developed. The procedure consisted of a solid-phase extraction (SPE) of the analytes on an Oasis HLB cartridge and the subsequent on-line fat elimination by directly dropping the eluate from the SPE cartridge onto a second cartridge containing layers of activated neutral silica gel and sulphuric acid modified silica gel. Detection limits using a gas chromatography coupled with an ion trap detector in the tandem mass spectrometry mode were from 0.03 to 0.3 pg/microL for PCBs and from 0.07 to 1.3 pg/microL for PBDEs. Repeatability (lower than 11%) and reproducibility (lower than 17%), expressed as relative standard deviation (RSD, n=4), were satisfactory. The feasibility of the method developed for the determination of the target compounds was evaluated by participation in several rounds of interlaboratory exercises involving human serum with a wide range of PBDE and PCB concentrations. The method has been applied to the evaluation of PBDEs and PCBs in human serum samples of up to 1 mL.     

Real-time monitoring of intravenous hypnotics propofol

A method for the determination of intravenous hypnotics in blood by monitoring of its concentration in exhaled air under clinical conditions is described. The results of propofol quantification in exhaled air are compared with those in blood collected by means of mass spectrometry. The possibility of the on-line noninvasive control of propofol in blood in the course of complex anesthesia using a mass spectrometer with electron ionization is demonstrated.     

Functionalized cucurbiturils and their applications

Cucurbit[n]uril (CB[n], n = 5-10), a new family of molecular hosts comprising n glycoluril units, have gained much attention in the new millennium for their exceptional molecular recognition ability. The CB homologues have brought dynamism to CB chemistry, as witnessed by the heightened interest in the field for the last several years. Compared to the chemistry of cyclodextrins and calixarenes, however, that of CB[n] has developed slowly until recently, which may be attributed mainly to their poor solubility in common solvents, and inability to functionalize these molecules. The direct functionalization method of CB[n] propelled CB chemistry to a new height as this new method not only solved the solubility problem but also opened up the gateway to the generation of tailor-made CB[n] derivatives. The functionalization of CB[n] led us to investigate numerous applications including artificial ion channels, vesicles, stationary phases in chromatography, ISEs, polymers, nanomaterials, and many others. This tutorial review describes the recent advances and challenges in the functionalization of CBs along with the applications of functionalized CBs.     

碱性体系在线氢化物发生—原子荧光光谱法测定痕量铋

提出了一种碱性体系在线氢化物发生－原子荧光光谱法测定痕量铋的分析方法。设计了在线氢化物发生系统流路及操作程序，研究了碱性体系氢化物发生的各项最佳条件。方法操作简便快速，能有效地消除过渡元素的严重化学干扰。应用于黄铜标样中痕量铋的直接测定，获得满意结果。     

Modified graphitized carbon black as transducing material for reagentless H2O2 and enzyme sensors

Direct electron transfer between redox enzymes and electrodes is the basis for the third generation biosensors. We established direct electron transfer between quinohemoprotein alcohol dehydrogenase (PQQ-ADH) and modified carbon black (CBs) electrodes. Furthermore, for the first time, this phenomenon was observed for pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (PQQ-GDH). Reagentless enzyme biosensors suitable for the determination of ethanol, glucose and sensors for hydrogen peroxide were designed using CB electrodes and screen-printing technique. Aiming to create an optimal transducing material for biosensors, a set of CB batches was synthesized using the matrix of Plackett-Burman experimental design. Depending on the obtained surface functional groups as well as the nano-scale carbon structures in CBs batches, the maximal direct electron transfer current of glucose and ethanol biosensors can vary from 20 to 300 nA and from 30 to 6300 nA for glucose and ethanol, respectively. Using modified CB electrodes, an electrocatalytic oxidation of H₂O₂ takes place at more negative potentials (0.1-0.4 V versus Ag/AgCl). Moreover, H₂O₂ oxidation efficiency depends on the amount and morphology of fine fraction in the modified CBs.     

Preparation of poly(propyleneimine) dendrimer immobilized silica gel and its application as novel microcolumn packing for the on-line FI preconcentration and separation of platinum

A G4.0 poly(propyleneimine) dendrimer immobilized silica gel (PPID-SG) was prepared with a divergent approach from gamma-aminopropyl silica gel (APSG) by repeating the reactions: 1) cyanoethylation of -NH2 and 2) reduction of -CN. Then it was successfully applied as the microcolumn packing for the on-line flow-injection (FI) preconcentration and separation and flame atomic absorption spectrometry (FAAS) determination of Pt. A limit of detection (LOD) of 0.014 microg/mL was obtained when 0.5 microg/mL Pt in chloride acid of PH = 3 was preconcentrated with a sample flow rate of 4.6 mL/min for 60s and the relative standard deviation (RSD) was 2.65%. Coexisting metal ions with concentration of 5.0 mg/mL and anion ions of 20.0 mg/ml have no interference in the determination of Pt. The proposed method was successfully applied to the determination of Pt in nickel alloy and anode slime samples.