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.     

高效液相色谱法测定棉布中的联苯胺

应用高效液相色谱法对棉布中的联苯胺进行了测定。色谱条件：ＨｙｐｅｒｓｉｌＯＤＳ柱（５μｍ,１５ｃｍ×４．６ｍｍｉ．ｄ．）,流动相组成为Ｖ（甲醇）Ｖ（水）＝７５２５,流速０．６ｍＬ／ｍｉｎ,检测波长２５４ｎｍ,压力１７．７ＭＰａ。以保留时间约２．５ｍｉｎ的联苯胺标样作对比,通过平行试验测定３个样品,测得联苯胺在棉布中的质量比（平均值）为１００．５７μｇ／ｇ。方法快速、灵敏,回收率为８４．７％。     

Determination of sulphonated azo dyes in food by ion-pair liquid chromatography with photodiode array and electrospray mass spectrometry detection

An ion-pair liquid chromatography method with on-line photodiode-array and electrospray mass spectrometry detection was developed to determine 10 commonly used sulphonated azo dyes (Tartrazine, Amaranth, New Coccine, Sunset Yellow FCF, Allura Red AC, Ponceau R, Ponceau 3R, Orange I, Orange II and Metanil Yellow) in food. A reversed phase C(18) column with gradient elution was utilized to separate these compounds. Triethylamine was added in the mobile phase as an ion-pair reagent for chromatographic separation. Photodiode-array detection was employed for quantitative determination and electrospray mass spectrometry was used for identification. Good linearity (0.05-10 ppm, r(2)=0.999) and detection limit (<0.01 ppm) were determined with 5 mul injection. In addition, precision and accuracy associated with this newly developed method will be presented. A liquid extraction method was also developed to extract these dyes from different foodstuffs. The application of this method was demonstrated by analyzing sulphonated azo dyes in soft drinks, fruit jam, and salted vegetables.     

Ultrasonic Extraction Coupled with Capillary Electrophoresis for the Determination of Azo Dyes in Lipsticks Using Ionic Liquid as Dynamic Coating and Background Electrolyte

A simple and rapid method based on ultrasonic extraction and capillary electrophoresis using 1‐butyl‐3‐methylimidazolium tetrafluoroborate as dynamic coating and background electrolyte was developed. The method was applied to the separation and determination of three azo dyes in two lipsticks. To increase extraction rate and yield, lipstick samples were coated on a glass slide before ultrasonic extraction. The dyes were extracted by ultrasonic extraction for 30 min, and then determined by capillary electrophoresis. Several experimental factors, such as ionic liquid concentration, pH value of background electrolyte and applied voltage, were examined and optimized. Under the optimal conditions, three azo dyes were completely separated within 12 min, and the detection limits for the three azo dyes ranged from 0.33 to 0.88 μg/mL. The recoveries were in the range of 96.8% to 108.8%.     

Application of zein‐modified magnetite nanoparticles in dispersive magnetic micro‐solid‐phase extraction of synthetic food dyes in foodstuffs

A simple method for the simultaneous and trace analysis of four synthetic food azo dyes including carmoisine, ponceau 4R, sunset yellow, and allura red from some foodstuff samples was developed by combining dispersive μ‐solid‐phase extraction and high‐performance liquid chromatography with diode array detection. Zein‐modified magnetic Fe₃O₄ nanoparticles were prepared and used for μ‐solid‐phase extraction of trace amounts of mentioned food dyes. The prepared modified magnetic nanoparticles were characterized by scanning electron microscopy and FTIR spectroscopy. The factors affecting the extraction of the target analytes such as pH, amount of sorbent, extraction time, type and volume of the desorption eluent, and desorption time were investigated. Under the optimized conditions, the method provided good repeatability with relative standard deviations lower than 5.8% (n = 9). Limit of detection values ranged between 0.3 and 0.9 ng/mL with relatively high enrichment factors (224–441). Comparing the obtained results indicated that Fe₃O₄ nanoparticles modified by zein biopolymer show better analytical application than bare magnetic nanoparticles. The proposed method was also applied for the determination of target synthetic food dyes in foodstuff samples such as carbonated beverage, snack, and candy samples.     

Temperature-induced dispersive solid-phase extraction as a new approach for preconcentration of Sudan dyes in water and food samples prior to the determination by high-performance liquid chromatography

This study introduced a new microextraction method named temperature-induced dispersive solid-phase extraction. The performance of the method was demonstrated with the determination of Sudan dyes in food and natural water samples. In this method, a low quantity of sorbent was added to the aqueous solution and the mixture was shaken manually for about one minute. Then, the solution was heated in an ultrasonic water bath, and the sorbent was dissolved. Subsequently, the solution was cooled down with ice water, and consequently, the solubility of the sorbent was reduced in the sample solution and became cloudy. The phase separation was accelerated by centrifugation. The upper liquid phase was picked up using a syringe, and the remainder was solved in methanol and introduced into the HPLC for analysis. Various parameters affecting the extraction yield were evaluated. Analytical parameters, including limits of detection (0.011–0.016 μg/L) and quantification (0.038–0.055 μg/L), relative standard deviations (2.3%–3.1%), and preconcentration factor (40) proved the high efficiency of the developed method for the analysis of Sudan dyes. The proposed method was used to measure Sudan dyes in water and food samples and showed good extraction recoveries (95.0%–103.5%).     

Determination of Benzidine and its Congeners by Liquid Chromatography with Electrochemical Detection

High performance liquid chromatography coupled with electrochemical detection (HPLC-EC) method has been developed for the determination of benzidine and its related congeners in wastewater at the low ng/mL level. With a µ-Bondapak C₁₈ column, 53% acetonitrile (pH 4.7), and electrochemical detection at +1.0 V applied potential, the detection limits range from 3 ng/mL for benzidine to 10 ng/mL for 3,3′-dichlorobenzidine, assuming a 100 µL injection. The detection limits can be further lowered to the sub-ng/mL level by incorporating a short precolumn into the HPLC system for on-line sample enrichment. Recoveries are generally greater than 80% — except for benzidine and 3,3′-diaminobenzidine which give 50–70% recoveries. Industrial wastewater samples from a coke-plant and a plant producing 3,3′-dichlorobenzidine based dyes were successfully studied via this method.     

Sorption of azo dyes from aqueous solutions by tetradodecyloxybenzylcalix[4]resorcinarene derivatives

Four water-insoluble tetradodecyloxybenzylcalix[4]resorcinarenes with various functional groups at the upper macrocycle rim (unsubstituted calix[4]resorcinarene 1, carboxylic acid derivative 2, ethyl ester derivative 3 and aminoethylamide derivative 4) were synthesized and tested as sorbents for water-soluble azo dyes methyl orange (MO), acid orange 5 (AO 5) and congo red (CR) by solid–liquid extraction method without background electrolyte. It was observed that the sorption of azo dyes reaches 99% for sorbent 4, which is partial protonated in contact with water and becomes able to electrostatic interactions with the dyes. It was demonstrates that calixresorcinarene 4 has the excellent sorption capacity for AO5 (130.5?mg dye per g of sorbent) due to effective calixresorcinarene—dye association in equal molar ratio mode.     

Evaluation of a new hypercrosslinked polymer as a sorbent for solid-phase extraction of polar compounds

A new hypercrosslinked polymer (HXLGp) with hydrophilic character due to the presence of hydroxyl moieties has been tested as a sorbent for the solid-phase extraction (SPE) of several polar compounds from water samples. This new sorbent enables the on-line extraction of 300 ml of sample with recoveries higher than 80% for polar compounds such as oxamyl, methomyl or desisopropylatrazine (DIA). The HXLGp has also been compared to other commercially available sorbents such as Oasis HLB (hydrophilic macroporous), to hydrophobic hypercrosslinked resins and to a previously synthesized sorbent based on N-vinylimidazole-divinylbenzene. The results are consistently better with the new synthesized sorbent. The method was successfully applied to the on-line SPE-HPLC of tap and river water samples. The validation with river water samples provided good linearity range and detection limits between 0.03 for methomyl and 4-nitrophenol (4NP) to 0.2 microg l(-1) for phenol (Ph).     

镍铁类水滑石对偶氮阴离子染料的吸附脱色作用

采用镍铁类水滑石作为吸附剂,对偶氮阴离子染料酸性大红G、活性艳红X-3B和直接耐酸大红4BS废水进行脱色处理,研究了时间、镍与铁的物质的量之比、初始pH和无机电解质添加剂等因素对脱色率的影响,并结合红外光谱和X射线衍射分析结果讨论了其吸附脱色机理.结果表明,三种染料在镍铁类水滑石上的吸附均为层间的阴离子交换吸附和外表面的吸附.通过阴离子交换进入层间后,不同于直接耐酸大红4BS阴离子,酸性大红G和活性艳红X-3B两种阴离子与水滑石层间水分子之间产生氢键作用;在化学键合过程中,染料分子被镍铁类水滑石表面Fe3+氧化,同时偶氮键断裂导致脱色.     

The evaluation of structural changes in wool fibre keratin treated with azo dyes by Fourier Transform Infrared Spectroscopy

Fourier Transform Infrared Spectroscopy spectroscopy is a useful technique for the analysis of structural changes in wool fibres at the molecular and supermolecular levels. Ecological requirements the textile industry has to meet oblige manufacturers to use ecological dyes in the process of fibre dyeing. These dyes should not split into the forbidden, carcinogenic aromatic amines (e.g. benzidine) while used. Wool was dyed with an azo dye, then underwent a chemical reaction. Changes were observed in the region of Amide A, Amide B, Amide I and II, dipolar ions amino acids, and the fingerprint region.     

Characterization of sulfonated azo dyes and aromatic amines by pyrolysis gas chromatography/mass spectrometry

Sixteen sulfonated and unsulfonated azo dyes as well as eleven sulfonated and unsulfonated aromatic amines were analyzed and qualitatively characterized by means of pyrolysis gas chromatography/mass spectrometry at different temperatures. Aniline and aminonaphthalene were found to be the dominant pyrolysis products of sulfonated aromatic amines and dyes. Azo dye and dye class specific key compounds such as benzidine, vinyl-p-base and 4-aminoazobenzene could be identified by pyrolysis gas chromatography/mass spectrometry of commercial acid, cationic, direct, reactive and solvent dyes. 500 degrees C was the optimal pyrolysis temperature for most of the pyrolyzed compounds. The method was applied to a dried sample of a textile wastewater concentrate from a dyeing process. Reactive azo dyes of the group of Remazol dyes and anthraquinone dyes could be identified as the major compounds of the sample. The finding of caprolactam (a printing additive) suggests that the wastewater contained effluent from a process of heat-activated printing with reactive dyes. p-Chloraniline, a banned aromatic amine, was identified. Chemical reduction of the wastewater sample prior to pyrolysis resulted in the release of volatile aromatic amines and aided the classification of several products of pyrolysis.     

Application of an ampholine‐functionalized hybrid organic–inorganic silica material for the SPE of aromatic amines

An SPE cartridge based on an ampholine‐functionalized hybrid organic–inorganic silica sorbent has been adopted for the analysis of aromatic amines including 4‐aminobiphenyl, benzidine, 2‐naphthylamine, p‐chloroaniline, 2,4,5‐trimethylaniline, and 3,3′‐dichlorobenzidine. Crucial variables governing the extraction efficiency of the material such as the pH of sample, sample loading volume, solvent used for elution, and elution volume have been thoroughly optimized. The adsorption capacities for the six aromatic amines ranged from 0.17 to 1.82 μg/mg. The recoveries of aromatic amines spiked in textile samples ranged from 78.9 to 103.0%, with RSDs of 1.1–11.9% (n = 3). Moreover, the extraction efficiency of the ampholine‐functionalized hybrid organic–inorganic silica sorbent was at least comparable with that of Oasis WCX.     

Standard additio--a way of improving quantification of banned azo dyes in leather

An analytical procedure based on supercritical-fluid extraction and microwave-assisted extraction was applied on six different real leather samples for the determination of banned azo dyes. Determination of the dyes was performed indirectly by measuring their corresponding harmful aromatic amines, formed after reduction. A comparative study between external standard calibration and standard addition using both the dyes as well as the corresponding amines showed that the latter quantification method provided the highest accuracy.     

Harmful azo colorants in leather. Determination based on their cleavage and extraction of corresponding carcinogenic aromatic amines using modern extraction techniques

This study concerns the possibilities of using microwave-assisted extraction (MAE) or supercritical fluid extraction (SFE) for detection of harmful azo colorants in leather. After degreasing of the leather sample with SFE there follows a reductive cleavage of the azo colorants to their corresponding aromatic amines in the MAE or SFE equipment. The aromatic amines are subsequently extracted using either MAE or SFE and then finally determined by liquid chromatography with diode-array detection. The results have been compared with recoveries obtained using the German DIN method 53316. This standard method, based on conventional solvent extraction, is used in several European countries. Overall much better recoveries were obtained using MAE or SFE. With both MAE and SFE the amine recoveries of spiked leather samples were generally above 50%. The average recoveries were 62% for MAE and 60% for SFE (solvent collection) compared to 24% with the DIN method. For genuine leather samples the recoveries decreased, especially for benzidine. In this case the average values for MAE, SFE and DIN were 54, 38 and 19%, respectively. The quantification limits in leather samples using MAE or SFE were below 1 mg/kg for all amines investigated. The within-laboratory precision was generally better than 10%, varying somewhat with the analyte considered. With the proposed methodology, the amount of hazardous organic solvents used could be decreased and the sample throughput increased with at least a factor of two with less manual handling compared to the DIN method.     

Weak anion-exchange hypercrosslinked sorbent in on-line solid-phase extraction–liquid chromatography coupling to achieve automated determination with an effective clean-up

A mixed-mode polymeric sorbent was on-line coupled to liquid chromatography (LC) for the first time and applied to the selective solid-phase extract a group of pharmaceuticals in complex environmental water samples. The mixed-mode polymeric sorbent is a high-specific surface area hypercrosslinked polymer resin (HXLPP) in the form of monodisperse microspheres further modified with 1,2-ethylenediamine (EDA) moieties. These properties allow its application as a weak anion-exchange (WAX) sorbent in the on-line solid-phase extraction (SPE) coupling. The on-line SPE-LC method developed using the HXLPP-WAX sorbent was successfully applied to percolate a large volume of ultrapure (500 ml), river (250 ml) and effluent sewage (100 ml) water samples. In all the cases, the HXLPP-WAX resin provided near total recoveries of the most acidic compounds studied and clean chromatograms. This is because the ion-exchange interactions enable a washing step to be added to the SPE protocol that removes the compounds with weak acidic, neutral and basic properties from the sample matrix.     

Application of polyaniline as an efficient and novel adsorbent for azo dyes removal from textile wastewaters

In this work, application of polyaniline coated onto wood sawdust (PAni/SD) for the removal of methyl orange (MO) as a typical azo dye from aqueous solutions is introduced. The effects of some important parameters such as pH, initial concentration, sorbent dosage, and contact time on the uptake of MO solution were also investigated. In order to get a better comparison, adsorption experiments were also carried out using commercial grade of granulated activated carbon (GAC) and sawdust without coating (SD) at the same time. It was found that PAni/SD can be used to remove azo dyes such as MO from aqueous solutions very efficiently. Experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Kinetic parameters for the adsorption of MO dyes for the selected adsorbents are also reported. In order to study the possibility of desorption for frequent application, chemical regeneration of the used adsorbents was also investigated. Desorption or recovery of dye and regeneration of adsorbent (PAni/SD) was found to be quite possible and of high performance. Application of modified sawdust with polyaniline for the removal of azo dye is very promising for textile wastewater treatment.     

On-line coupling of subcritical water extraction with high-performance liquid chromatography via solid-phase trapping

Although ambient water is very polar and cannot dissolve many organic species, water at elevated temperatures behaves like a polar organic solvent. Thus, subcritical water has been proven to be an effective extraction fluid for several classes of organic compounds. While solvent trapping was used to collect the extracted analytes in most of previous subcritical water extractions, sorbent trapping has also been developed for subcritical water extraction. In this study, an on-line system for subcritical water extraction and high-performance liquid chromatography (HPLC) was built and tested. A sorbent trap was used as the interface between subcritical water extraction and HPLC. Several shut-off valves have been utilized to switch the system from one mode to another (e.g., from the extraction mode to HPLC mode). The coupling technique of subcritical water extraction and HPLC eliminates the liquid-liquid extraction used in solvent trapping subcritical water extraction and provides higher sensitivity. Compared to the off-line system reported in an earlier work, the operation of this on-line system is even easier. Some peak broadening occurred after the coupling the water extraction with HPLC for the analytes studied. The performance of this on-line system was evaluated by the extraction and determination of caffeine, nitrotoluenes, polychlorinated biphenyls, chlorophenols and anilines.     

Solid-phase extraction of polar compounds with a hydrophilic copolymeric sorbent

A new synthesized copolymer based on N-vinylimidazole-divinylbenzene (VIm-DVB) was tested as a sorbent for the solid-phase extraction (SPE) of polar analytes. In the on-line SPE, this synthesized sorbent enabled 100 ml of sample to be preconcentrated with recoveries as high as 80% for oxamyl, phenol (Ph) and derivates, bentazone and (4-chloro-2-methylphenoxy)acetic acid (MCPA). For the off-line SPE, 1000 ml of sample was extracted and recoveries were higher than 92% for all compounds with the exception of oxamyl (83%) and methomyl (78%). The VIm-DVB sorbent gives better recoveries than the previously synthesized 4-vinylpyridine-divinylbenzene (VP-DVB) resin and similar to such highly crosslinked commercial sorbents as LiChrolut EN or Oasis HLB. Real water samples were used to validate the on-line SPE method. Linearity was good and detection limits were between 0.1 and 0.2 microg l(-1).     

New hydrophilic polymeric resin based on 4-vinylpyridine-divinylbenzene for solid-phase extraction of polar compounds from water

A 4-vinylpyridine-divinylbenzene (VP-DVB) resin was synthesized to be used for on-line solid-phase extraction process and it was tested for a group of polar compounds. The high specific surface area and the nitrogen content of the VP-DVB sorbent increased the interactions with the polar analytes in the preconcentration process. The sorbent enabled 100 ml of water to be concentrated with recoveries higher than 70% for several polar compounds (including phenol) except for oxamyl (55%) and methomyl (43%). The method was used to analyse water samples by liquid chromatography and UV detection. Linearity was good and detection limits were 0.1-0.2 microg l(-1) for all compounds. Several tap and river water and waste water treatment plant samples were analyzed; phenol and (4-chloro-2-methyl-phenoxy)acetic acid (MCPA) were tentatively determined in some samples.