Ultrasonication extraction coupled with magnetic solid-phase clean-up for the determination of polycyclic aromatic hydrocarbons in soils by high-performance liquid chromatography

C18-functionalized magnetic microspheres synthesized in a three-stage system and characterized by Fourier transform infrared (FTIR) spectroscopy and SEM were applied for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) in soil samples combined with ultrasonication extraction. Magnetic solid-phase extraction (MSPE) parameters, such as elution solvents, amounts of sorbents, enrichment time and organic modifier, were optimized together with ultrasonication time and extraction solvents. Under the optimal conditions, the developed method provided spiked recoveries of 63.2-92.8% with RSDs of less than 6.4% and limits of detection were 0.5-1.0 ng/g. This new method provides several advantages, such as high extraction efficiency, convenient extraction procedure and short analysis times. Finally, the method was successfully applied to the determination of polycyclic aromatic hydrocarbons in soil samples.     

Exploration of coordination polymer as sorbent for flow injection solid-phase extraction on-line coupled with high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in environmental materials

The copper(II) isonicotinate (Cu(4-C5H4N-COO)2(H2O)4) coordination polymer was prepared, characterized and explored as sorbent for flow injection solid-phase extraction on-line coupled with high-performance liquid chromatography (HPLC) for determination of trace polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Naphthalene, phenanthrene, anthracene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(ghi)perylene with various shape, size and hydrophobicity were used as model analytes. The porosity of the coordination polymer allows these guest PAHs molecules to diffuse into the buck structure, and the shape and size of the pores lead to shape- and size-selectivity over the guests. The precolumn packed with the coordination polymer was shown to be promising for solid-phase extraction of PAHs in environmental samples with subsequent HPLC separation and UV detection. With extraction of 50 ml of sample solution, the enhancement factors for the PAHs studied ranged from 200 to 2337, depending on the shape, size and hydrophobic property of the PAHs. The detection limits (S/N = 3) of 2-14 ng l(-1) and the sample throughput of 3 samples h(-1) were obtained. The developed method was applied to the determination of trace PAHs in a certified reference material (coal fly ash) and local water samples.     

Comparison of adsorbents for on-line solid-phase extraction of polycyclic aromatic hydrocarbons before liquid chromatography with UV detection

Summary On-line solid-phase extraction (SPE) coupled with reversed-phase liquid chromatography and UV detection at 254 nm has been used for the determination of trace-level polycyclic aromatic hydrocarbons (PAH) in soil extracts. Five commercially available adsorbents (C₈, C₁₈, PLRP-S, PRP-1, and Bond-Elut Env) were evaluated. Results showed that recovery of the PAH decreased with increasing molecular weight, because of their poorer solubility. Recovery of high-molecular-weight PAH was significantly improved by addition of 10% (v/v) acetonitrile to the sample before loading of the SPE adsorbent. PAH recovery ranged from 64.0 to 108% when a 50 mL sample spiked with 1 μg L⁻¹ was applied to these adsorbents. Determination of PAH was possible with detection limits below 0.05 μg L⁻¹, which corresponds to 0.2 μg kg⁻¹ soil. The method was successfully used to determine PAH in soil extracts.     

Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter was used to replace a conventional sample loop on the injector valve of the HPLC for on-line solid-phase extraction. The sample solution was loaded and the analytes were then preconcentrated onto the preconcentration column. The collected analytes were subsequently eluted with a mobile phase of methanol-water (95:5). HPLC with a photodiode array detector was used for their separation and detection. The detection limits (S/N = 3) for preconcentrating 42 mL of sample solution ranged from 0.9 to 58.6 ng L(-1) at a sample throughput of 2 samples h(-1). The enhancement factors were in the range of 409-1710. The developed method was applied to the determination of trace NAPH, PHEN, ANT, FLU, BbF, BkF, BaP and BghiP in local river water samples. The recoveries of PAHs spiked in real water samples ranged from 87 to 115%. The precisions for nine replicate measurements of a standard mixture (NAPH: 4.0 microg L(-1), PHEN: 0.40 microg L(-1), ANT: 0.40 microg L(-1), FLU: 2.0 microg L(-1), BbF: 1.6 microg L(-1), BkF: 2.0 microg L(-1), BaP: 2.0 microg L(-1), BghiP: 1.7 microg L(-1)) were in the range of 1.2-5.1%.     

Carboxyl modified multi-walled carbon nanotubes as solid-phase extraction adsorbents combined with high-performance liquid chromatography for analysis of linear alkylbenzene sulfonates

Recently, multi-wall carbon nanotubes (MWCNTs) as adsorbents of solid-phase extraction are attractive because they can be used for enrichment of organic compounds and metal ions at trace levels. In this study, we use the carboxyl modified multi-wall carbon nanotubes (CMMWCNTs) as adsorbents of solid-phase extraction for extraction of linear alkylbenzene sulfonates (LAS), which are widely used anion surfactant with different homologues, and detected by HPLC-UV. The effect of eluent and its volume, sample pH and flow rate, sample volume and the ultrasonic time of sample, the content of the electrolyte (NaCl) were investigated and optimized. The detection limit for LAS homologues was 0.02-0.03 μg L⁻¹ with R.S.D. (n = 6) ranging from 2.04 to 10.03%. The recoveries of LAS homologues in the spiked environmental water samples ranged from 84.8 to 106.1%. The proposed method has been applied successfully to the analysis of LAS in aqueous environmental samples, which demonstrates that CMMWCNTs-based solid-phase extraction is a precision and convenient enrichment method and can be used for analysis of LAS homologues in water samples.     

Multiwalled carbon nanotubes as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for simultaneous determination of 10 sulfonamides in eggs and pork

The sulfonamides (SAs) have been widely used as effective chemotherapeutics and growth promoters in animals' feeding, but their residues could be a potential danger to human health due to their carcinogenic potency and possible antibiotic resistance. Development of a simple and sensitive method for the determination of SAs residues in food of animal origin, therefore, is of great significance. An on-line solid-phase extraction (SPE) method using multiwalled carbon nanotubes as sorbent coupled with high-performance liquid chromatography (HPLC) for simultaneous determination of 10 sulfonamides (SAs) in eggs and pork was developed. The adsorptive potential of carbon nanotubes for solid-phase extraction of sulfonamides was investigated for the first time in the present paper. To on-line interface solid-phase extraction with HPLC, a conventional sample loop on the six-port injector valve of the HPLC was replaced by a preconcentration column packed with carbon nanotubes. The analytes in water solution were preconcentrated onto the preconcentration column and subsequently eluted with mobile phase of methanol-water (22:78). The developed on-line solid-phase extraction method for HPLC permitted the current HPLC separation and the next preconcentration proceeded in parallel, and thus allows one determination finished within 35 min. The RSD of 10 SAs for nine replicate measurements of a standard mixture of 1 microgl(-1) were in the range of 2.5-7.8%. The method was applied to the determination of trace sulfadiazin (SDZ), sulfamerazine (SMR), sulfadimidine (SDMD), sulfathiazole (STZ), sulfamoxol (SMO), sulfamethizole (SMT), sulfamethoxypyridazine (SMP), sulfachlorpyridazine (SCP), sulfadoxin (SDX) and sulfisoxazole (SIA) in eggs and pork. The results indicated that the proposed method was simple, cost-effective and sensitive.     

Multiwalled carbon nanotubes as solid-phase extraction materials for the gas chromatographic determination of organophosphorus pesticides in waters

In the present work, a GC method with nitrogen-phosphorus detection (NPD) was developed for the simultaneous determination of eight organophosphorus pesticide (OPP) residues (i.e., ethoprofos, diazinon, chlorpyrifos-methyl, fenitrothion, malathion, chlorpyrifos, fenamiphos, and buprofezin) in water samples. Preconcentration of the water samples was carried out using an SPE procedure with multiwalled carbon nanotubes (MWCNTs) of 10-15 nm od, 2-6 nm id, and 0.1-10 microm length as stationary phase. Extraction parameters, such as the amount of MWCNTs, sample volume, pH, and type and amount of the eluent were optimized. The most favorable conditions were as follows: 40 mg MWCNTs, 800 mL water, pH 6.0, and 20 mL dichloromethane, respectively. The MWCNTs-SPE-GC-NPD method was applied to the determination of these pesticides in real water samples: mineral and ground water as well as run-off water from an agricultural area collected shortly before opening out onto the sea. A recovery study was developed with five consecutive extractions of the three types of water spiked at three concentration levels (n = 15). Mean recovery values were in the range of 75-116% for mineral water (RSD < 6.3%), 67-119% for ground water (RSD < 5.8%), and 57-81% for run-off waters (RSDs < 6.9%), except for fenamiphos (mean recovery values between 40 and 84% for the three types of waters, RSDs < 8.9%). LODs were in the low ng/L level (i.e., levels below the maximum residue limits (MRLs) established by the European Union (EU) legislation for these compounds in waters). The proposed method was also applied to the analysis of six water samples (two of each type: mineral, ground, and run-off waters) in which no residues of the selected pesticides were found. Results show that the MWCNTs used in this work have a high adsorbability of the pesticides under study. The main advantage of the use of these MWCNTs is their low cost when compared with those MWCNTs previously used in the literature and with conventional SPE cartridges.     

Commercial polymeric fiber as sorbent for solid-phase microextraction combined with high-performance liquid chromatography for the determination of polycyclic aromatic hydrocarbons in water

A novel microextraction method making use of commercial polymer fiber as sorbent, coupled with high-performance liquid chromatography-fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in water has been developed. In this technique, the extraction device was simply a length (8 cm) of a strand of commercial polymer fiber, Kevlar (each strand consisted of 1000 filaments, each of diameter ca. 9.23 μm), that was allowed to tumble freely in the aqueous sample solution during extraction. The extracted analytes were desorbed ultrasonically before the extract was injected into HPLC system for analysis. Extraction parameters such as extraction time, desorption time, type of desorption solvent and sample volume were optimized. Each fiber could be used for up to 50 extractions and the method showed good precision, reproducibility and linear response within a concentration range 0.05–5.00 μg L⁻¹ with correlation coefficients of up to 0.9998. Limits of detection between 0.4 and 4.4 ng L⁻¹ for seven PAHs could be achieved. The relative standard deviations (n = 3) of this technique were between 2.9% and 12.1%.     

Rapid determination of polycyclic aromatic hydrocarbons in tea infusion samples by high-performance liquid chromatography and fluorimetric detection based on solid-phase extraction

This paper describes a method for the determination of PAHs in black, green and decaffeinated tea infusion samples. The method is based on the solid phase extraction of the PAHs using Sep-Pak vac tC-18 cartridges. The PAHs are then eluted from the cartridges with dichloromethane. Quantification and detection are carried out by HPLC with a fluorimetric detector using a program of excitation and emission wavelength pairs. Recoveries at concentration levels in the range 190-1790 ng l-1 were higher than 65% for all PAHs except dibenz[a,h]anthracene, for which it was around 54%. The mean content of PAHs was in the range 28.7-112 ng l-1 in the tea infusions, with relative standard deviations between 2 and 18% (n = 4).     

Multi-walled carbon nanotubes as solid-phase extraction adsorbents for the speciation of cobalamins in seafoods by liquid chromatography

Multi-walled carbon nanotubes (MWCNTs) were evaluated as potential adsorbents for miniaturized solid-phase extraction coupled to liquid chromatography. The adsorption capacity of this sorbent was applied to assess the speciation of four cobalamins representing the various forms of vitamin B₁₂. The preconcentration on the MWCNTs was based on the retention of analytes by introducing the sample online into the mini-column system. Dimethyl sulfoxide was used to elute the retained vitamins for liquid chromatographic analysis. The experimental conditions of the continuous flow device, which affect the enrichment procedure, such as the type and amount of nanotubes, the volume, pH and flow rate of the sample solution, and the eluent and its volume, were optimized. For detection purposes, a diode array device was used and good resolution was obtained with a mobile-phase acetonitrile–phosphate buffer and gradient elution. Specificity was demonstrated by the retention characteristics and UV spectra and by comparing the peak purity index with commercial standards. Linearity, precision, recovery, and sensitivity were satisfactory. Detection limits ranged from 0.35 to 30 ng mL⁻¹. The method was successfully applied to the determination of cobalamins in seafoods, which were extracted from the sample with a buffer solution using an ultrasonic probe. The reliability of the procedure was checked by analyzing a certified reference material.     

在线固相萃取-液相色谱法直接测定水中超痕量多环芳烃

建立了在线固相萃取-液相色谱直接测定水体中16种超痕量多环芳烃（PAHs）的方法。水样经高速离心后，加入适量甲醇，配制成40%（体积分数）甲醇水溶液，直接进样2 mL至在线固相萃取流路，进行萃取富集，再通过阀切换将洗脱的PAHs转移至分析流路进行分离检测。16种PAHs在各自范围内线性关系良好，相关系数均大于0.996；方法的检出限为0.14~12.50 ng/L，其中苯并[a]芘（B（a）P）的检出限为0.38 ng/L。实际水样在10、40和200 ng/L加标水平下的加标回收率为76.1%~134.9%，RSD为0.3%~16.6%。B（a）P在1 ng/L加标水平下的回收率为71.8%~92.7%，RSD为3.9%。结果表明，该方法操作简单，灵敏度高，溶剂消耗量少，可满足水样中PAHs，尤其是B（a）P的超痕量分析要求。     

基于氮化碳复合材料磁性固相萃取结合高效液相色谱法测定尿液中3种羟基多环芳烃

建立了测定尿液中3种羟基多环芳烃的氮化碳复合材料磁性固相萃取结合高效液相色谱-荧光检测法。所构筑的磁性氮化碳材料，经扫描电子显微镜、X射线衍射仪、振动样品磁强计和比表面积分析仪表征后，用于尿液中3种羟基多环芳烃的富集净化。考察了吸附剂用量、吸附时间、洗脱溶液和洗脱体积（单次洗脱体积×洗脱次数）对萃取效率的影响。结合高效液相色谱-荧光分析，在0.25~250 μg/L范围内线性关系良好（相关系数r=0.999），3种羟基多环芳烃的检出限和定量限分别为0.08和0.25 μg/L，回收率为90.1%~102%，日内和日间精密度分别为1.5%~7.7%和2.2%~8.7%。该本方法简单、快速、高效，可用于尿液中羟基多环芳烃的分析。     

Dynamic microwave-assisted extraction coupled on-line with solid-phase extraction: determination of polycyclic aromatic hydrocarbons in sediment and soil

This paper describes a new extraction tool for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil and sediment samples, using dynamic microwave-assisted extraction combined with solid-phase extraction (DMAE-SPE). The critical variables for DMAE-SPE are investigated and optimized in an experimental design. The technique proved to be fast, accurate and able to yield quantitative extraction of PAHs from naturally contaminated sediment and soil samples. The set-up is fully automated and features monitored extraction, which facilitates rapid optimization of the method. In addition, only small quantities of solvent and sample are required.     

Screening and determination of polycyclic aromatic hydrocarbons in seafoods using QuEChERS-based extraction and high-performance liquid chromatography with fluorescence detection

A rapid, sensitive, and accurate method for the screening and determination of polycyclic aromatic hydrocarbons (PAHs) in edible seafood is described. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction and HPLC with fluorescence detection (FLD). The method was developed and validated in response to the massive Deepwater Horizon oil spill in the Gulf of Mexico. Rapid and highly sensitive PAH screening methods are critical tools needed for oil spill response; they help to assess when seafood is safe for harvesting and consumption. Sample preparation involves SPE of edible seafood portions with acetonitrile, followed by the addition of salts to induce water partitioning. After centrifugation, a portion of the acetonitrile layer is filtered prior to analysis via HPLC-FLD. The chromatographic method uses a polymeric C18 stationary phase designed for PAH analysis with gradient elution, and it resolves 15 U.S. Environmental Protection Agency priority parent PAHs in fewer than 20 min. The procedure was validated in three laboratories for the parent PAHs using spike recovery experiments at PAH fortification levels ranging from 25 to 10 000 microg/kg in oysters, shrimp, crab, and finfish, with recoveries ranging from 78 to 99%. Additional validation was conducted for a series of alkylated homologs of naphthalene, dibenzothiophene, and phenanthrene, with recoveries ranging from 87 to 128%. Method accuracy was further assessed based on analysis of National Institute of Standards and Technology Standard Reference Material 1974b. The method provides method detection limits in the sub to low ppb (microg/kg) range, and practical LOQs in the low ppb (microg/kg) range for most of the PAH compounds studied.     

Multiwalled carbon nanotubes/cryogel composite, a new sorbent for determination of trace polycyclic aromatic hydrocarbons

A new cost-effective sorbent, multiwalled carbon nanotubes/poly (vinyl alcohol) cryogel composite (MWCNTs/PVA), was prepared under frozen conditions for the extraction and preconcentration of trace polycyclic aromatic hydrocarbons (PAHs) in water samples. This was followed by high performance liquid chromatography (HPLC) with fluorescence detection. The proposed method provided a high enrichment factor with an extremely high extraction efficiency (89–98%) of three spiked levels of three standard PAHs with relative standard deviations of less than 8%. The low detection limits of the method were 5, 8 and 5 ng L^{− 1} for benzo(a)anthracene, benzo(b)fluoranthene and benzo(a)pyrene, respectively. This method was successfully applied for the determination of the three PAHs in real water samples where they were found in the range of 7 to 22 ng L^{− 1}. The major advantages of MWCNTs/PVA over the commercial C₁₈ is that it can be operated at a higher loading flow rate without sorbent clogging and requires a shorter time for completion without any loss of extraction efficiency.     

On-line solid-phase extraction and high performance liquid chromatography determination of polycyclic aromatic hydrocarbons in water using polytetrafluoroethylene capillary

Naphthalene, biphenyl, acenaphtene, anthracene and pyrene were extracted from water samples using inner walls of polytetrafluoroethylene capillary. Optimum conditions for sorption, desorption and heart-cutting of the analyte zone were found. Combined on-line solid-phase extraction and HPLC method for determination of these compounds was proposed. Limits of detection were: (μg L⁻¹): 0.4 (naphthalene), 0.3 (biphenyl), 0.6 (acenaphtene), 0.2 (anthracene) and 0.1 (pyrene).     

基于整体柱的固相萃取-高效液相色谱法测定尿液中4种羟基多环芳烃

建立了基于聚合物整体柱的固相萃取-高效液相色谱测定尿液中4种羟基多环芳烃（OH-PAHs）的分析方法。在注射器管中合成聚（甲基丙烯酸丁酯-乙二醇二甲基丙烯酸酯）整体柱（poly （BMA-co-EDMA））,并将其用于尿液中4种羟基多环芳烃的前处理,同时考察了上样浓度、淋洗液、洗脱液和洗脱体积对萃取效率的影响。结合高效液相色谱-荧光分析,4种羟基多环芳烃在各自的范围内线性关系良好（r≥0.9991）;方法的检出限和定量限分别为0.06~0.09 ng/mL和0.20~0.30 ng/mL;日内（n=5）和日间（n=3）精密度分别为1.4%~5.3%和2.6%~7.3%。对焦炉工人尿液样品进行加标（3 ng/mL）回收试验,回收率为78.2%~117.0%。该固相萃取柱能够有效萃取和净化尿液中4种羟基多环芳烃,并且可以重复使用。该法简单、准确,可应用于尿液中羟基多环芳烃的分析。     

Modern state of high-performance liquid chromatography of polycyclic aromatic hydrocarbons

The review is devoted to the recent studies in the field of high-performance liquid chromatography (HPLC) of polycyclic aromatic hydrocarbons (PAHs). The existing certified techniques, developments of synthesis of new sorbents for separating PAH isomers, and study of the retention mechanism are discussed. It also considers the modern methods of extraction and concentration of PAHs, mainly from environmental objects, which are compatible with subsequent identification by HPLC, as well as the necessity of analytical control of contamination of the environment, food sources, and food supplies with PAHs.     

Magnetic mixed hemimicelles solid-phase extraction of xanthohumol in beer coupled with high-performance liquid chromatography determination

In this study, silica-coated magnetic nanoparticles (Fe(3)O(4)/SiO(2) NPs) modified by cetyltrimethylammonium bromide (CTAB) were synthesized. They were successfully applied for extraction of xanthohumol in beer based on magnetic mixed hemimicelles solid-phase extraction (MMHSPE) coupled with high-performance liquid chromatography-ultraviolet determination. The main factors influencing the extraction efficiency including the surfactant amount, the beer pH, the extraction time, the desorption condition and the maximum extraction beer volume were optimized. Under the optimized conditions, a concentration factor of 60 was achieved by extracting 120 mL beer sample using MMHSPE and the detection limit of xanthohumol is 0.0006 mg/L. The proposed method was successfully applied for determination of xanthohumol in various beer samples with the xanthohumol contents in the range of 0.031-0.567 mg/L. The satisfactory recoveries (90-103%) were obtained in analyzing spiked beer samples.     

Determination of some selected polycyclic aromatic hydrocarbons in environmental samples by high-performance liquid chromatography with fluorescence detection

Summary Analytical methods for the determination in environmental samples, of some selected Polycyclic Aromatic Hydrocarbons (PAH's), which are included on the EPA Priority Pollutant list, have been developed and evaluated. The methodology involves the extraction of PAH's from water samples by solvent extraction with dichloromethane. Solid samples were ultrasonically extracted with acetone/hexane and the extract was cleaned up on a silica gel/alumina column. The concentrated and cleaned up extracts were analysed by HPLC on a polymeric C₁₈ column using a gradient of acetonitrile/water as the mobile phase and fluorescence detection. Typical detection limits lie in the range of 1–30 ng ml^–1 of the analytes, but after sample pretreatment detection limits of 10–300 ng l^–1 were obtained. The extraction, clean-up and HPLC methodology was applied to the determination of selected PAH's in coal washings samples and the method was validated by the quantification of PAH's in a natural contaminated and a spiked sediment.