Rapid SPE-HPLC determination of the 16 European priority polycyclic aromatic hydrocarbons in olive oils

Polycyclic aromatic hydrocarbons (PAHs) are a large class of organic compounds. It has been established that the main source of exposure to these compounds for human beings is through food, particularly fats and oils, due to the lipophilic nature of these polycyclic compounds. The aim of this work was to optimise and validate a method involving SPE and HPLC for rapid determination of the 16 European Union (EU) priority PAHs (required by the Recommendation 2005/108/EC) in vegetable oils. Two spectrofluorometric detectors and a UV-Visible detector in series were used to identify and quantify the target compounds. Linearity, recoveries, LOD, and LOQ were found to be in agreement with the performance criteria for benzo[a]pyrene (BaP) analysis as required by the Commission Directive 2005/10/EC, and satisfactory for all the compounds of interest, except for cyclopenta[c,d]pyrene, which presented a very low signal in the UV. Optimised chromatographic conditions for the separation of 25 PAHs, comprising both EPA and EU priority PAHs plus benzo[e]pyrene and benzo[b]chrysene, have been also proposed.     

Application of counter-current chromatography as a new pretreatment method for the determination of polycyclic aromatic hydrocarbons in environmental water

Counter‐current chromatography (CCC) was investigated as a new sample pretreatment method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in water environmental samples. The experiment was performed with a non‐aqueous binary two‐phase solvent system composed of n‐heptane and acetonitrile. The CCC column was first filled with the upper stationary phase, and then a large volume of water sample was pumped into the column while the CCC column was rotated at 1600 rpm. Finally, the trace amounts of PAHs extracted and enriched in the stationary phase were eluted out by the lower mobile phase and determined by gas chromatography–flame ionization detector (GC‐FID) or gas chromatography–mass spectrometry (GC‐MS). The enrichment and cleanup of PAHs can be fulfilled online by this method with high recoveries (84.1–103.2%) and good reproducibility (RSDs: 4.9–12.2%) for 16 EPA PAHs under the optimized CCC pretreatment conditions. This method has been successfully applied to determine PAHs in lake water where 8 PAHs were detected in the concentration of 40.9–89.9 ng/L. The present method is extremely suitable for the preparation of large volume of environmental water sample for the determination of trace amounts of organic pollutants including PAHs as studied in this paper.     

Optimisation and validation of programmed temperature vaporization (PTV) injection in solvent vent mode for the analysis of the 15 + 1 EU-priority PAHs by GC-MS

This paper presents the optimisation of a programmed temperature vaporization solvent vent (PTV-SV) injection gas chromatographic mass spectrometric (GC-MS) method for the analysis of the 15 + 1 EU-priority PAHs in food extracts. Three operation parameters (vent time, vent flow and vent pressure) were optimised by applying a D-optimal experimental design. Among these variables, vent time showed the highest effect on the analytical response (signal intensity) of the target PAHs.The 15 + 1 EU-priority PAHs were analysed in solvent solutions and in extracts of fortified sausage. In addition, blank lamb meat extracts were prepared and spiked with the target PAHs prior to GC-MS analysis. The performance of the optimised PTV-SV injection GC-MS method was scrutinised for linearity, precision, matrix effects and robustness. All parameters were found satisfactorily. Compared to PTV injection in splitless mode, the PTV-SV injection method provided an enhancement of sensitivity for all target PAHs. Especially significant was the improvement of the S/N ratios of the compounds with the highest molecular mass.     

Development and optimisation of a dopant assisted liquid chromatographic-atmospheric pressure photo ionisation-tandem mass spectrometric method for the determination of 15+1 EU priority PAHs in edible oils

European food legislation defines a set of 16 polycyclic aromatic hydrocarbons (PAHs) as of high concern for human health. The EU set contains structurally very similar PAHs with ring numbers between 4 and 6, and so raises some separation aspects and problems, which were not experienced with traditionally analysed PAHs. Many of the currently applied gas chromatographic mass spectrometric (GC-MS) methods suffer from separation problems, while high performance liquid chromatography with fluorescence detection (HPLC-FLD) is neither capable of detecting the whole set of EU priority PAHs nor does it (compared to GC-MS) allow structural identification. In addition HPLC-FLD shows limitations with difficult matrices due to interferences. The aim of this paper is to fill this gap by describing a liquid chromatographic dopant assisted atmospheric pressure photo ionisation tandem mass spectrometric (LC-DA-APPI-MS/MS) method for the determination of 15+1 EU priority PAHs in edible oil, which complies with the requirements set by European food legislation. Measurements were performed in positive ion mode. Anisole at a flow rate of 30 μl/min was used as dopant. Sample preparation was performed offline by donor-acceptor complex chromatography (DACC). Compared to HPLC-FLD methods the presented method enables the determination of all 15+1 EU priority PAHs at the low μg/kg concentration range including less fluorescence active compounds like benzo[j]fluoranthene and indeno[1,2,3-cd]pyrene. By analysing four reference materials it could be demonstrated that this method provides accurate results and is sufficiently sensitive for food control purposes. Statistically significant differences between the reference values and the measured analyte contents were not found. The method performs well also for very complex samples. Repeatability relative standard deviations (RSDr) of the determination of the target PAHs in olive oil were for most analytes below 5%. The limit of detection (LOD) of the method met the requirement set by EU legislation (0.3 μg/kg).     

Feasibility of two multidimensional techniques, heart-cut MDGC and GCxGC, for the separation of PCBs and PBDEs

The feasibility of heart-cut MDGC-ECD and GCxGC-muECD for the separation of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) has been evaluated. Among the different column combinations tested, the best results were obtained when using either a DB-5 type or an HT-8 column as the first dimension combined with a mid-polar stationary phase (50% phenyl) as the second dimension. The co-elutions between the target PCBs and PBDEs in the first dimension were satisfactorily resolved once transferred to the second column. Repeatability and intermediate precision were satisfactory in both systems, considering retention times in both dimensions. Nevertheless, peak area/volume precision was better for heart-cut MDGC since software for the data analysis in the case of GCxGC was still under development. The need for multiple injections of the same extract on the heart-cut MDGC system was the main drawback since the analysis time it increased. GCxGC becomes then a valuable alternative able to achieve the same performance in one injection. However, the GCxGC data analysis is still very time-consuming and needs further development. The applicability of both separation techniques was shown using a human breast milk sample with low concentrations of PCBs (0.2-227 pg/g fresh weight) and PBDEs (1.2-41 pg/g fresh weight).     

Evaluation of the separation characteristics of application-specific (volatile organic compounds) open-tubular columns for gas chromatography

The solvation parameter model is used to characterize the separation characteristics of two application-specific open-tubular columns (Rtx-Volatiles and Rtx-VGC) and a general purpose column for the separation of volatile organic compounds (DB-WAXetr) at five equally spaced temperatures over the range 60-140 degrees C. System constant differences and retention factor correlation plots are then used to determine selectivity differences between the above columns and their closest neighbors in a large database of system constants and retention factors for forty-four open-tubular columns. The Rtx-Volatiles column is shown to have separation characteristics predicted for a poly(dimethyldiphenylsiloxane) stationary phase containing about 16% diphenylsiloxane monomer. The Rtx-VGC column has separation properties similar to the poly(cyanopropylphenyldimethylsiloxane) stationary phase containing 14% cyanopropylphenylsiloxane monomer DB-1701 for non-polar and dipolar/polarizable compounds but significantly different characteristics for the separation of hydrogen-bond acids. For all practical purposes the DB-WAXetr column is shown to be selectivity equivalent to poly(ethylene glycol) columns prepared using different chemistries for bonding and immobilizing the stationary phase. Principal component analysis and cluster analysis are then used to classify the system constants for the above columns and a sub-database of eleven open-tubular columns (DB-1, HP-5, DB-VRX, Rtx-20, DB-35, Rtx-50, Rtx-65, DB-1301, DB-1701, DB-200, and DB-624) commonly used for the separation of volatile organic compounds. A rationale basis for column selection based on differences in intermolecular interactions is presented as an aid to method development for the separation of volatile organic compounds.     

Highly sensitive determination of haloperidol in human serum by capillary gas chromatography using a surface ionization detector

A method has been developed for highly sensitive determination of haloperidol in human serum involving a simple extraction procedure followed by gas chromatographic separation. Target components were separated from the extracting solvents with a Van den Berg type solventless sample injector before introduction Into a DB-1 capillary separation column. A surface ionization detector (SID), which has highly selective sensitivity for Substituted amines, was employed for quantitation using bromperidol as an internal standard. Chloroform proved to be the best extracting solvent, yielding a quantitative detection limit of 5 ng/ml (S/N = 2). Comparison of the response to target compounds obtained by the SID, FTD (flame thermionic detector), and FID (flame ionization detector) showed the SID to be superior.     

凝固漂浮有机液滴-分散液液微萃取结合高效液相色谱法同时测定地表水中多环芳烃和酞酸酯

多环芳烃和酞酸酯是国际公认的优控污染物,因此准确快速地测定水中多环芳烃和酞酸酯非常重要。凝固漂浮有机液滴-分散液液微萃取（DLLME-SFO）是一种简便、快速、环境友好、灵敏度高的样品前处理技术。采用DLLME-SFO同时测定地表水中多环芳烃和酞酸酯的分析方法鲜有报道。该文采用凝固漂浮有机液滴-分散液液微萃取富集技术,结合高效液相色谱紫外/荧光法,建立了同时测定地表水中16种多环芳烃和6种酞酸酯的分析方法。考察优化了影响萃取效率的主要因素,包括萃取剂的种类和用量、分散剂的种类和用量、萃取时间和离子强度等。优化后的萃取实验条件为：5.0 mL水样,10 μL十二醇为萃取溶剂,500 μL甲醇为分散溶剂,涡旋振荡时间2 min,氯化钠用量0.2 g。目标化合物经多环芳烃专用色谱柱（SUPELCOSIL^TM LC-PAH,150 mm×4.6 mm,5 μm）结合乙腈-水梯度洗脱分离,16种多环芳烃除苊烯外采用荧光检测,苊烯和6种酞酸酯采用紫外检测,外标法定量。结果表明,22种目标化合物的基质加标回收率为60.2%~113.5%,相对标准偏差为1.9%~14.3%;多环芳烃和酞酸酯的检出限分别为0.002~0.07 μg/L和0.2~2.2 μg/L;多环芳烃和酞酸酯的定量限分别为0.006~0.23 μg/L和0.8~7.4 μg/L。该方法简便、快速,环境友好,灵敏度高,可用于地表水中多环芳烃和酞酸酯的快速分析检测。     

Comparison of two sample clean‐up methodologies for the determination of polycyclic aromatic hydrocarbons in edible oils

An off‐line high‐performance normal‐phase liquid chromatography procedure with a silica column followed by reversed‐phase high‐performance liquid chromatography (HPLC) with fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils is reported. The method was validated using certified reference materials and compared with a standardized method widely used in the food industry, consisting in low pressure column chromatography with alumina as stationary phase followed by reversed phase HPLC determination. The limits of detection were lower than 1 ng/g and good selectivity was achieved for both methods. There were no significant differences in accuracies and precisions obtained for each approach. The advantages and disadvantages of the two methods are discussed.     

Layer-by-layer self-assembled multi-walled carbon nanotubes/silica microsphere composites as stationary phase for high-performance liquid chromatography

Multi-walled carbon nanotubes (MWCNTs) were layer-by-layer assembled onto silica microspheres to form MWCNTs/SiO(2) composites and were characterized by surface analysis, elemental analysis, and contact angle. The composite was used as a stationary phase in HPLC for the separation of many kinds of aromatic compounds. The separation of polycyclic aromatic hydrocarbons (PAHs) affected by the number of MWCNTs layers on SiO(2) was investigated. Retention times and resolutions of PAHs were affected by the assembled layer of MWCNTs and the type of organic additive in the mobile phase. When the MWCNTs layer increased to 5 (MWCNTs/SiO(2)-5), PAHs can be completely separated. Aromatic compounds with different substituents can be well separated when only water was used as the eluent on the MWCNTs/SiO(2)-5 column. Decreasing the pH of the eluent can increase the retention factors of organic acids. Organic amines can also be separated with acetonitrile as organic additive, which were eluted in the order of the electronic cloud density of their aromatic rings. Comparing the MWCNTs/SiO(2)-5 column with a commercial HPLC column, it was clearly shown that the commercial column exhibited the characteristic of hydrophobicity, and the MWNCTs/SiO(2)-5 column exhibited the characteristic of a large π-electron system.     

Separation characteristics of phenyl-containing stationary phases for gas chromatography based on silarylene-siloxane copolymer chemistries

The solvation parameter model is used to characterize the retention properties of five open-tubular column stationary phases (ZB-5 ms, DB-5 ms, DB-XLB, DB-17 ms, and DB-35 ms) based on silarylene-siloxane copolymer chemistries at five equally spaced temperatures over the range 60-140 degrees C. System constant differences and regression models for varied compounds are used to establish the selectivity equivalence of the silarylene-siloxane copolymer stationary phases and to compare their separation characteristics with poly(dimethyldiphenylsiloxane) stationary phases containing a nominally similar concentration of phenyl groups. These studies demonstrate that ZB-5 ms and DB-5 ms are selectivity equivalent. DB-XLB is significantly more dipolar and polarizable than DB-5 ms. In general terms, the silarylenesiloxane copolymer stationary phases are slightly less cohesive and more dipolar and polarizable with similar hydrogen-bond basicity to the poly(dimethyldiphenylsiloxane) stationary phases they were designed to replace. None of the silarylenesiloxane copolymer or poly(dimethyldiphenylsiloxane) stationary phases are hydrogen-bond acidic. Selectivity differences between the two types of stationary phase are temperature dependent and tend to be smaller at higher temperatures within the temperature range studied. Consequently, selectivity differences cannot be globalized without reference to the temperature for the comparison.     

Comprehensive analysis of polycyclic aromatic hydrocarbons in wastewater using stir bar sorptive extraction and gas chromatography coupled to tandem mass spectrometry

The objective of this study was the optimization and comparison of two extraction methods for the determination of polycyclic aromatic hydrocarbons (PAHs) in wastewater (WW). A distribution study of the target compounds between the aqueous phase and the suspended particulate matter (SPM) has been performed in order to establish whether the analysis of both phases is necessary. In this sense, the feasibility of stir bar sorptive extraction (SBSE) and solid-phase extraction (SPE) for the determination of 24 PAHs in WW samples has been evaluated. The results demonstrated the suitability of SBSE to perform a comprehensive analysis of liquid samples containing high amounts of SPM, such as in the determination of PAHs in WWs. A gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) method has been also optimized for the separation and detection of the target compounds, avoiding the co-elution of some groups of isomers, such as benzo[b], [j] and [k] fluoranthenes and indene[1,2,3-cd]pyrene/dibenz[a,h]anthracene. For that purpose, a specific capillary column developed for PAH determination was used. The SBSE procedure was validated and adequate parameters (such as recovery, linearity, precision, limits of detection and quantification) were obtained. Finally, the validated method was applied to the analysis of real samples collected from an experimental WW treatment plant, detecting some PAHs at concentrations in the range 0.007-0.022 μg L(-1).     

HPLC retention behaviors of poly-aromatic-hydrocarbones on Cu(II)-octabromotetrakis(4-carboxyphenyl)porphine derivatives-immobilized aminopropyl silica gels in polar and non-polar eluents

As one of approaches of developing novel HPLC stationary phases, we prepared Cu-octabromotetrakis(4-carboxyphenyl)porphine derivative-immobilized silica gels (Cu-OBTCPP(D)), and evaluated the availability of the resultant Cu-OBTCPP(D) as a stationary phase for separation of poly-aromatic-hydrocarbons (PAHs) and their related compounds. A Cu-OBTCPP(D) column was revealed to have an ability to separate simple PAHs and be useful as a stationary phase in both polar and non-polar eluents. The retention property of the Cu-OBTCPP(D) column was evaluated in various comparative experiments using commercially available columns. In comparison with 2-(1-pyrenyl)ethyl dimetylsilyl silica gel column (PYE column) regarding the retention behavior for PAHs etc., the Cu-OBTCPP(D) column showed stronger interactions involving pi electron in non-polar eluent than PYE column. In comparison with a pentabromobenzyloxy propylsilyl silica gel column (PBB column) regarding the influence of bromination, the Cu-OBTCPP(D) column was affected differently from the PBB column. In comparison with nitrophenylethyl silica gel column (NPE column) regarding the retention behavior for compounds having a dipole in a non-polar eluent, the Cu-OBTCPP(D) column showed electrostatic interactions such as dipole-dipole interaction equivalent to or larger than the NPE column.     

顶空固相微萃取-气相色谱-质谱法测定玩具中可迁移有机锡化合物

建立了顶空固相微萃取结合气相色谱-质谱联用技术测定玩具中10种可迁移有机锡化合物的方法。玩具材料经0.07 mol/L HCl浸泡2 h后,使用醋酸-醋酸钠缓冲溶液将浸泡液的pH值调至4.7,然后加入四乙基硼化钠将浸泡液中的有机锡化合物乙基化,在振荡条件下用100 μ m聚二甲基硅氧烷(PDMS)纤维进行顶空固相微萃取,萃取完成后将纤维插入气相色谱进样口进行热解吸,使用DB-5毛细管柱对10种有机锡化合物进行分离。10种有机锡化合物的检出限为0.5~5 μg/kg。两个加标水平(0.500 μg/L和5.00 μg/L)下的回收率分别为80.7%~118.7%和86.2%~120.5%,RSD均低于15%。应用该方法测定了玩具可触及材料(包括涂层、织物、塑料、木料)中的可迁移有机锡化合物。该方法简便、快速、灵敏度高,不需使用有毒有机溶剂,绿色环保。     

Quantification of cephalexin as residue levels in bovine milk by high-performance liquid chromatography with on-line sample cleanup

A multidimensional, selective and precise high performance liquid chromatography (HPLC) method based on direct injection of biological samples has been developed for the determination of cephalexin in skimmed and whole bovine milk. The cephalosporin antibiotic was extracted from bovine milk using an octyl restricted access medium bovine serum albumin column (C₈-RAM-BSA) and analyzed on an octadecyl column using phosphate buffer (pH 7.5, 0.01 M): ACN (92:8, v/v) and ultraviolet detection at 260 nm. The calibration graph was linear in the concentration range of 25-1600 ng/mL and this is in accordance with the tolerance level of 100 ng/mL set by the FDA (Food and Drug Administration) and EU (European Union) for cephalexin as residue in bovine milk. The intra- and inter-day coefficients of variation for the replicate analysis at the quality control levels were less than 15% while the transfer efficiency was in the range of 90.2-92.3%. The limits of detection and quantification were 10 and 20 ng/mL, respectively.     

Selectivity assessment of popular stationary phases for open-tubular column gas chromatography

The solvation parameter model is used to study the influence of temperature and composition on the selectivity of nine poly(siloxane) and two poly(ethylene glycol) stationary phase chemistries for open-tubular column gas chromatography. A database of system constants for the temperature range 60-140 degrees C was constructed from literature values with additional results determined for HP-50+, DB-210, DB-1701, DB-225 and SP-2340 columns. The general contribution of monomer composition (methyl, phenyl, cyanopropyl, and trifluoropropyl substituents) on the capacity of poly(siloxane) stationary phases for dispersion, electron lone pair, dipole-type and hydrogen-bond interactions is described. The selectivity coverage of the open-tubular column stationary phases is compared with a larger database for packed column stationary phases at a reference temperature of 120 degrees C. The open-tubular column stationary phases provide reasonable coverage of the range of dipole-type and hydrogen-bond base interactions for non-ionic packed column stationary phases. Deficiencies are noted in the coverage of electron lone pair interactions. None of the open-tubular column stationary phases are hydrogen-bond acids. The system constants are shown to change approximately linearly with temperature over the range 60-140 degrees C. The intercepts and slopes of these plots are used to discuss the influence of temperature on stationary phase selectivity.     

气相色谱-质谱法同时测定塑料食品接触材料中25种芳香族伯胺的迁移量

采用固相萃取前处理技术,结合气相色谱-质谱法对食品接触材料中25种芳香族伯胺的迁移量进行了同时测定。样品中25种目标物分别用蒸馏水和30 g/L醋酸浸出后,用氨水调节浸泡液至pH 8～10,经固相萃取小柱富集净化,再用体积比为1:1的叔丁基甲醚和乙醇混合液洗脱定容后用气相色谱-质谱仪测定。不同芳香族伯胺的检出限略有差异,在0.4～2.0 μg/kg的范围内。加标水平在10 μg/kg时,除2,4-二氨基苯甲醚在酸性模拟物中的回收率较低外,其他芳香族伯胺的回收率均在51.6%～118.4%之间,相对标准偏差(n=7)为0.5%～9.8%。同时探讨了不同实验条件如叔丁基甲醚和乙醇的体积比、pH值等条件对25种芳香族伯胺回收率的影响。结果表明,该方法准确、稳定,完全满足欧盟指令No 10/2011对食品接触塑料材料及制品中芳香族伯胺特定迁移量的限量要求,可用于食品接触材料中芳香族伯胺的实际检验。     

Evaluation of the Linear-Elution-Strength Model for the Prediction of Retention and Selectivity in Isothermal Gas Chromatography

Linear-elution strength theory and temperature-programmed gas chromatography is evaluated as a rapid method for predicting isothermal retention factors and column selectivity. Retention times for a wide range of compounds are determined at the program rates of 3 and 12 °C/min for the temperature range 60 to 160 °C on three open-tubular columns (DB-1701, DB-210 and EC-Wax) and used to predict isothermal retention factors for each column over the temperature range 60 to 140 °C. The temperature-program predicted isothermal retention factors are compared with experimental values using linear regression and the solvation parameter model. It is shown that isothermal retention factors predicted by the linear-elution-strength model only approximately represents the experimental data. The model fails to predict the slight curvature that exists in most plots of the experimental retention factor (log k) as a function of temperature. In addition, regression of the temperature-program predicted isothermal retention factors against the experimental values indicates that the slopes and intercepts deviate significantly from their target values of one and zero, respectively, in a manner which is temperature dependent. The temperature-program predicted isothermal retention factors result in system constants for the solvation parameter model that are different to those obtained from the experimental retention factors. These results are interpreted as indicating that linear-elution-strength theory predicts retention factors that fail to accurately model stationary phase interactions over a wide temperature range. It is concluded that temperature-program methods using linear-elution-strength theory are unsuitable for constructing system maps for isothermal separations.     

Accurate analysis of trace earthy-musty odorants in water by headspace solid phase microextraction gas chromatography-mass spectrometry

A simple and sensitive method was developed for the simultaneous separation and determination of trace earthy-musty compounds including geosmin, 2-methylisoborneol, 2-isobutyl-3-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,3,4-trichloroanisole, 2,4,6-trichloroanisole, and 2,3,6-trichloroanisole in water samples. This method combined headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry and used naphthalene-d(8) as internal standard. A divinylbenzene/carboxen/polydimethylsiloxane fiber exposing at 90°C for 30 min provided effective sample enrichment in HS-SPME. These compounds were separated by a DB-1701MS capillary column and detected in selected ion monitoring mode within 12 min. The method showed a good linearity from 1 to 100 ng L(-1) and detection limits within (0.25-0.61 ng L(-1)) for all compounds. Using naphthalene-d(8) as the internal standard, the intra-day relative standard deviation (RSD) was within (2.6-3.4%), while the inter-day RSD was (3.5-4.9%). Good recoveries were obtained for tap water (80.5-90.6%), river water (81.5-92.4%), and lake water (83.5-95.2%) spiked at 10 ng L(-1). Compared with other methods using HS-SPME for determination of odor compounds in water samples, this present method had more analytes, better precision, and recovery. This method was successfully applied for analysis of earthy-musty odors in water samples from different sources.