Selective extraction of benzoic acid from landfill leachate by solid-phase extraction and ion-exchange chromatography

In this work a simple method was described for selective extraction of benzoic acid from landfill leachate samples. The samples were submitted to solid-phase extraction (SPE) with XAD-4 resin as the stationary phase and ion-exchange chromatography (IEC) using the ion-exchange resin Amberlyst A-27. The instrumental analysis was performed by gas chromatography with mass spectrometric detection (GC-MSD). Benzoic acid was isolated, identified and quantified. The extraction process is rapid, simple and of low cost. It was also environmental friendly, that is, it was used a minimum amounts of hazardous organic solvents and produced also minimum quantities of residues.     

牛奶样品中新霉素残留量的离子色谱法测定

建立了阴离子交换色谱-脉冲安培检测分析牛奶中新霉素残留量的方法.实验采用三氯乙酸沉淀蛋白,弱阳离子交换固相萃取柱富集净化,处理牛奶样品,并考察了三氯乙酸浓度、样品过柱速度以及洗脱剂浓度等因素对牛奶中新霉素测定结果的影响.牛奶中新霉素的回收率在50.3%～76.9%范围内,基底加标工作曲线的相关系数为0.9949(n=6),线性范围为10.0～160.0ng/mL.所建立的方法可满足牛奶中低新霉素残留量的检测需要.     

Recent developments in matrix solid-phase dispersion extraction

Matrix solid-phase dispersion is a sample preparation strategy widely applied to solid, semisolid or viscous samples, including animal tissues and foods with a high lipidic content. The process consists in blending the matrix onto a solid support, allowing the matrix cell disruption and the subsequent extraction of target analytes by means of a suitable elution solvent. First introduced in 1989, MSPD employment and developments are still growing because of the feasibility and versatility of the process, as evidenced by the several reviews that have been published since nineties. Therefore, the aim of the present review is to provide a general overview and an update of the last developments of MSPD.     

固相萃取法与基质固相分散法在橙子中有机磷农药残留分析中的应用

建立了固相萃取(SPE)-反相高效液相色谱(RP-HPLC)同时测定橙子中痕量辛硫磷、二嗪农有机磷农药残留量的方法。样品经甲醇超声提取、C18固相萃取柱净化后,采用液相色谱柱分离,以乙腈-水(体积比为85∶15)为流动相等度洗脱,于254 nm下紫外检测。结果表明:在0.1～10.0 mg/L和0.4～10.0 mg/L范围内,辛硫磷、二嗪农的质量浓度与峰面积呈良好的线性关系;样品的加标平均回收率为87.3%～102.7%,相对标准偏差(RSD)为0.9%～4.9%。将该分析结果与用基质固相分散法(MSPD)处理样品所得的结果相比较,发现SPE对二嗪农的提取效果较好,而MSPD对辛硫磷的提取效果较好,但两种方法都能较好地净化样品,均能满足残留量的分析要求。     

Evaluation of matrix solid-phase dispersion (MSPD) extraction for multi-mycotoxin determination in different flours using LC-MS/MS

An existing matrix solid-phase dispersion (MSPD) method for aflatoxins (AFs) and ochratoxin A (OTA) extraction was extended by further 14 mycotoxins. After it careful optimization, this method was applied to determine the occurrence of these mycotoxins on commercial flour samples (with different cereals composition) collected from local markets. In a total of 49 samples investigated, 9 mycotoxins were identified. Nivalenol (NIV) and Beauvericin (BEA) were the mycotoxins found most frequently. The samples that presented major contamination were wheat flours and bakery preparations. Despite of the great number of positives finding, only one wheat flour sample exceeded the maximum limits (ML) for OTA established by the European Union (EU). However, it would be interesting to calculate the total ingest of these mycotoxins along the years.     

Poly-hydroxamic acid (PHA) matrix for gadolinium pre-concentration and removal

A novel hydrophilic, three dimensionally cross-linked, aliphatic backbones with pendant hydroxamic acid (HA) group as functional moiety has been synthesized and utilized targeting removal of gadolinium [Gd(III)] from laboratory waste aqueous effluent. To understand the nature of sorption, gadolinium solution of various concentrations viz., 20, 10, 5.0, 1.0, 0.5 and 0.1 ppm has been contacted with a dose rate of 1 g/100 mL for 2 h. In this study, ICP-AES has been used for determination of concentration (ppm) of gadolinium in feed, filtrate and elute. EDXRF study also ensures the presence of gadolinium in the respective medium. Loaded gadolinium matrix was eluted with 1 N HCl for determining the elution factor (0.98).     

Determination of fluoroquinolones in blood by matrix solid-phase dispersion extraction and CE

A simple and rapid method for the determination of residues of four fluoroquinolones in blood samples was developed. The method was based on matrix solid‐phase dispersion extraction followed by CE with ultraviolet detection. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate aqueous solution was used as the background electrolyte for the separation of fluoroquinolones. The average recoveries of the four fluoroquinolones at two spiked levels ranged from 54.0 to 86.4% for pig blood, and 45.4 to 79.9% for deer blood, with the relative standard deviations <9.45%. Detection limits for the four fluoroquinolones in blood sample ranged from 0.15 to 0.31 μg/mL.     

Preliminary evaluation of new polymer matrix for solid-phase extraction of nonylphenol from water samples

Molecularly imprinted (MIP) and blank polymers with affinity for nonylphenol were designed using computational modelling. Chromatographic tests demonstrated higher affinity of imprinted polymers towards the template nonylphenol as compared with blank polymers. The performance of both polymers in solid-phase extraction was however very similar. Both blank and imprinted polymers appeared to be suitable for the removal and pre-concentration of nonylphenol from contaminated water samples with 99% efficiency of the recovery. The commercial resins PH(EC) (Biotage) and C18 (Varian) tested in the same conditions used for comparative purposes had recovery rate <84%. The polymer capacity for nonylphenol was 231 mg g⁻¹ for blank and 228 mg g⁻¹ for MIP. The synthesised materials can have significance for sample pre-concentration and environmental analysis of this class of compounds.     

Two-dimensional coordination polymer matrix for solid-phase extraction of pesticide residues from plant Cordia salicifolia

The 2D coordination polymer (_∞[Gd(DPA)(HDPA)]) was tested for extraction of acephate, chlorpropham, pirimicarb, bifenthrin, tetradifon, and phosalone from the medicinal plant Cordia salicifolia, whose extracts are commercialized in Brazil as diuretic, appetite suppressant, and weight loss products, using GC/MS, SIM. Considering that there are no Brazilian regulations concerning maximum permissible pesticide residue concentrations in medicinal herbs, recovery experiments were carried out (seven replicates), at two arbitrary fortification levels (0.5 and 1.0 mg/kg), resulting in recoveries in range of 20 to 107.7% and SDRSDs were between 5.6 and 29.1% for _∞[Gd(DPA)(HDPA)] sorbent. Detection and quantification limits for herb ranged from 0.10 to 0.15 mg/kg and from 0.15 to 0.25 mg/kg, respectively, for the different pesticides studied. The developed method is linear over the range assayed, 0.5–10.0 μg/mL, with correlation coefficients ranging from 0.9975 to 0.9986 for all pesticides. Comparison between _∞[Gd(DPA)(HDPA)] sorbent and conventional sorbent (neutral alumina) showed similar performance of _∞[Gd(DPA)(HDPA)] polymeric sorbent for three (bifenthrin, tetradifon, and phosalone) out of six pesticides tested.     

Liquid ion-exchange extraction study of hexacyanoferrate(III) with trioctylmethylammonium chloride (aliquat-336)

Liquid-liquid ion-exchange extraction of various anions including hexacyanoferrate(III) with a chlorobenzene solution of trioctylmethylammonium chloride (TOMA-Cl; Aliquat-336 chloride) is described. The ion-pair extraction constant of TOMA-Cl (K^Q.Cl_ex = 10⁴) and the ion-exchange extraction constants of TOMA-Cl for each anion (K^Cl.X_ex) are reported. The order of selectivity of anion extraction is Fe(CN)^3-₆ (log K^Q.X_ex = 22.41) > ClO^-₄(8.47) > PAR^- (7.80) > I^-(7.32) > NO^-₃(5.81) > Br^-(5.34) > Cl^-(4.00).     

Graphitized carbons for solid-phase extraction

The objective of this review is to provide updated information about the most important features of graphitized carbonaceous sorbents used for solid-phase extraction (SPE) of organic compounds from liquid natural matrices or extracts. The surface characteristics of graphitized carbon blacks and porous graphitic carbons are described which are responsible for the various types interactions (hydrophobic, electronic and ion-exchange) with analytes. The method development is given which is based on the prediction from liquid chromatographic retention data obtained using porous graphitic carbon. Emphasis is placed on their capability for trapping very polar and water-soluble analytes from aqueous samples. Comparison is made between carbon-based SPE sorbents and other reversed-phase materials such as octadecyl silicas and highly cross-linked copolymers. Especially, the difficulty encountered for the desorption of some strongly retained analytes is explained by LC data and solutions are given for optimizing the composition and volume of the desorption solution. Many examples illustrate the various common features of graphitized carbons which are the extraction of very polar analytes and multiresidue extractions. Some applications are specific to graphitized carbon black due to the presence of surface functional groups. They include the extraction of anionic compounds such as benzene and naphthalene sulfonates or acidic pesticides. Other applications are specific to porous graphitic carbon due to its flat and homogeneous surface. One example is the trace extraction of coplanar polychlorinated biphenyls (PCBs), dibenzo-p-dioxins and dibenzofurans from other PCB congeners.     

Solid-phase extraction versus matrix solid-phase dispersion: Application to white grapes

The use of matrix solid-phase dispersion (MSPD) was tested to, separately, extract phenolic compounds and organic acids from white grapes. This method was compared with a more conventional analytical method previously developed that combines solid liquid extraction (SL) to simultaneously extract phenolic compounds and organic acids followed by a solid-phase extraction (SPE) to separate the two types of compounds. Although the results were qualitatively similar for both techniques, the levels of extracted compounds were in general quite lower on using MSPD, especially for organic acids. Therefore, SL-SPE method was preferred to analyse white “Vinho Verde” grapes. Twenty samples of 10 different varieties (Alvarinho, Avesso, Asal-Branco, Batoca, Douradinha, Esganoso de Castelo Paiva, Loureiro, Pedernã, Rabigato and Trajadura) from four different locations in Minho (Portugal) were analysed in order to study the effects of variety and origin on the profile of the above mentioned compounds. Principal component analysis (PCA) was applied separately to establish the main sources of variability present in the data sets for phenolic compounds, organic acids and for the global data. PCA of phenolic compounds accounted for the highest variability (77.9%) with two PCs, enabling characterization of the varieties of samples according to their higher content in flavonol derivatives or epicatechin. Additionally, a strong effect of sample origin was observed. Stepwise linear discriminant analysis (SLDA) was used for differentiation of grapes according to the origin and variety, resulting in a correct classification of 100 and 70%, respectively.     

Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 microL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized.     

Synthesis and applications of surface-grafted Th(IV)-imprinted polymers for selective solid-phase extraction of thorium(IV)

A new functional monomer N-(o-carboxyphenyl)maleamic acid (CPMA) was synthesized and chosen for the preparation of surface-grafted ion-imprinted polymers (IIPs) specific for thorium(IV). Polymerizable double bond was introduced to silica gel surface by amidation reaction between -NH₂ and maleic anhydride. In the ion-imprinting process, thorium(IV) was complexed with the carboxyl groups, then was imprinted in the polymers grafted to the silica gel surface. The imprinted Th(IV) was removed with 3 mol L⁻¹ HCl. The obtained imprinted particles exhibited excellent selectivity and rapid kinetics process for Th(IV). The relatively selective factor (α_r) values of Th(IV)/La(III), Th(IV)/Ce(III), Th(IV)/Nd(III), Th(IV)/U(VI), and Th(IV)/Zr(IV) were 85.7, 88.9, 26.6, 64.4, and 433.8, respectively, which were greater than 1. The precision (R.S.D.), the detection limit (3σ), and the quantification limit (10σ) of the method were 1.9%, 0.51 ng mL⁻¹ and 1.19 ng mL⁻¹, respectively. The prepared IIPs as solid-phase extractants were successfully applied for the preconcentration of trace thorium in natural and certified samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) with satisfactory results.     

Novel molecularly imprinted polymer prepared by nanoattapulgite as matrix for selective solid-phase extraction of diethylstilbestrol

Using nanoattapulgite as matrix, both diethylstilbestrol surface molecularly imprinted polymer and non-imprinted polymer were synthesized in this work. Compared with each other, the diethylstilbestrol surface molecularly imprinted polymer is superior to non-imprinted polymer in adsorption capacity, selectivity and mass transfer property. The maximum static adsorption capacities of diethylstilbestrol surface molecularly imprinted polymer, non-imprinted polymer and nanoattapulgite for diethylstilbestrol was 105.14, 78.54 and 28.50 mg g⁻¹, respectively. As the packing material of solid-phase extraction, the diethylstilbestrol surface molecularly imprinted polymer has been applied to concentrating diethylstilbestrol in pond water and fish samples. A corresponding analytical method to determine diethylstilbestrol has been developed. The limit of detection for diethylstilbestrol in pond water sample and fish samples were 3 μg L⁻¹ and 15 μg kg⁻¹.     

96-well plate-to-plate gravity fluorous solid-phase extraction (F-SPE) for solution-phase library purification

Large particle size (125_210 microm) fluorous silica gel bonded with a -SiCH2CH2C8F17 stationary phase has been employed for gravity-driven fluorous solid-phase extraction (F-SPE) on two types of 96-well plates. A 1 or 0.75 g portion of fluorous silica is packed to each well of the 3.5-mL Ex-Blok and the 2.2-mL deep-well filtration plates, respectively. Up to 50 mg of reaction mixture is loaded and then eluted with a fluorophobic solvent (DMSO, DMF, or 85:15 DMF-H2O). Products collected in 96-well receiving plates are directly concentrated on a GeneVac vacuum centrifuge. This simple and highly efficient plate-to-plate F-SPE technique has been demonstrated in the purification of four 96-compound libraries produced by scavenging reactions with 1-(perfluoroctyl)propyl isatoic anhydride (F-IA), amide coupling reactions with 2-chloro-4,6-bis[(perfluorooctyl)propyloxy]-1,3,5-triazine (F-CDMT) or 2,4-dichloro-6-(perfluorooctyl)propyloxy-1,3,5-triazine (F-DCT), and Mitsunobu reactions with fluorous diethyl azodicarboxylate (F-DEAD) and triphenylphosphine (F-TPP). Approximately 80% of products in each library have greater than 85% purity after F-SPE without conducting chromatography.     

Molecularly imprinted solid-phase extraction of (-)-ephedrine from Chinese Ephedra

Method of molecularly imprinted solid phase extraction (MISPE) of (-)-ephedrine from Chinese Ephedra has been developed in the research. The molecularly imprinted polymer (MIP) with good selectivity and affinity for (-)-ephedrine was synthesized with (-)-ephedrine as the template, methacrylic acid as the functional monomer. The washing and elution conditions in MISPE were selected and optimized for efficient analyte extraction and sample clean-up. A clean analytical HPLC base line of ephedra extract was obtained after MISPE, which indicated that the sample pre-treatment was efficient. Good recovery and precision were obtained in the assessment for the MISPE-HPLC procedure, which demonstrated it is a reliable method and can be used for the determination of (-)-ephedrine in herbal ephedra.     

Microscale solid-phase extraction system for explosives

A simple, semi-automated, microcolumn solid-phase extraction (SPE) system is optimized for the extraction, preconcentration and HPLC analysis of seven different explosives and explosive derivatives contaminating seawater, river water and well water samples. The microcolumns were constructed from 1/16 in. O.D. PTFE tubing (1 in.=2.54 cm) packed with 0.5-1.5 mg of SPE material. LiChrolut EN or Porapak R. The extraction system consisted of two syringe pumps and several solenoid valves. Optimal detection limits were realized when the sample water flow-rate was maximally increased within the limits of the pump, 5-10 ml/min (despite exceeding the breakthrough threshold of the SPE microcolumn), and when the eluate volume collected from the column was minimized, <5 microl (despite very low recovery percentages).     

Chemically modified resins for solid-phase extraction

The packings most widely used for solid-phase extraction are hydrophobic and make poor surface contact with aqueous samples unless the resins are first treated with an activating organic solvent such as methanol. Insertion of an acetyl- or hydroxymethyl group into a porous polystyrene-divinylbenzene resin provides a more hydrophilic surface that is easily wetted by water alone. Small columns of the chemically modified resins were found to be very efficient for the solid-phase extraction of many types of organic solutes from aqueous samples. Comparative recovery studies showed that the modified resins are superior to both silica packings and unmodified organic resins for the solid-phase extraction of organic compounds, and especially for polar organics such as phenols.