Off-line SPE Research Articles

Simultaneous Analytical Method for Various Paraben and Alcohol Preservatives in Supposedly Natural and Organic Cosmetics by Off-line SPE–UHPLC–DAD and LC–MS/MS

Simultaneous Analytical Method for Various Paraben and Alcohol Preservatives in Supposedly Natural and Organic Cosmetics by Off-line SPE–UHPLC–DAD and LC–MS/MS

Mass Spectrometry Approaches for Detection and Determination of Prostaglandins from Biological Samples.

Accurate determination of prostaglandins (PGs) from biological samples is critical for understanding their biological functions and interactions during physiological and pathological processes. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a highly sensitive, accurate, and high-throughput approach for simultaneous detection of ultra-trace PGs from a single biological sample. Here we describe LC-MS/MS techniques and related sample pretreatment methods including both off-line and on-line SPE for the determination of PGs in biological samples.

Determination of 107 typical pesticides and metabolites in raw water and drinking water by online-solid phase extraction coupled with ultra performance liquid chromatography-triple quadrupole mass spectrometry

In order to monitor the risk of pesticide pollutants in drinking water, an analytical method based on online-solid phase extraction coupled with ultra performance liquid chromatography-triple quadrupole mass spectrometry (online-SPE-UPLC-MS/MS) was established for the simultaneous rapid screening and determination of 107 pesticides and metabolites (organophosphorus, organic nitrogen, organic heterocycle, carbamate, amide, benzoyl urea, neonicotinoid, etc.) in raw water and drinking water. Different injection volumes (5, 10, and 15 mL) were compared. The detection response increased with an increase in the injection volume, but the matrix effect also became more pronounced. Under the premise of ensuring the sensitivity of the method and meeting the detection requirements, the injection volume was selected as 5 mL. Accordingly, the samples were filtered through a 0.22-μm hydrophilic polytetrafluoroethylene filter, and then, 5 mL samples were injected into the online-SPE system by the automatic sampler. After adsorption on an X Bridge C18 online-SPE column, the samples were washed with pure water and eluted by gradient elution using acetonitrile and 0.1% formic acid aqueous solution as the mobile phases, with separation on an ACQUITY HSS T3 column. The samples were detected by multiple reaction monitoring with electrospray ionization in positive and negative ion modes, and quantified by an external standard method. Using raw water and drinking water as the sample matrices, the accuracy and precision of the method were verified. The 107 pesticides and metabolites showed good linear relationships in different ranges with correlation coefficients (r2)>0.995. The limits of detection (LODs, S/N=3) of the method were 0.03-1.5 ng/L, and the limits of quantification (LOQs, S/N=10) were 0.1-5.0 ng/L. The target pesticides were spiked at concentration levels of 1, 20, and 50 ng/L. The spiked recoveries of the 107 targets in raw water and drinking water samples were 60.6%-119.8% and 61.2%-119.0%, respectively. The corresponding relative standard deviations (RSDs, n=6) were 0.3%-18.6% and 0.4%-17.1%. The pesticide residues in raw water and drinking water were determined by this method. Amide herbicides, triazine herbicides, triazole insecticides, carbamate insecticides, and neonicotinoid insecticides had high detection rates. The detected concentrations ranged from 0.1 to 97.1 ng/L in raw water and from 0.1 to 93.6 ng/L in drinking water. The sample consumption of online-SPE method was lower than that in the traditional off-line SPE methods, which greatly improved the convenience of sample collection, storage, and transportation. The samples only need to be filtered before injection and analysis. The method is simple to operate and shows good reproducibility. With this online-SPE method, only 23 min were required from online enrichment to detection completion. The developed method has the advantages of high analytical speed and high sensitivity. The method is suitable for the trace analysis and determination of 107 typical pesticides in raw water and drinking water, which effectively improves the detection efficiency of pesticides in water and has high potential for practical application. It can extend technical support for the pollution-level analysis of typical pesticides and metabolites in drinking water and provide an objective basis for human health risk assessment.

Characterization, Classification and Authentication of Spanish Blossom and Honeydew Honeys by Non-Targeted HPLC-UV and Off-Line SPE HPLC-UV Polyphenolic Fingerprinting Strategies.

Honey is a highly consumed natural product produced by bees which is susceptible to fraudulent practices, some of them regarding its botanical origin. Two HPLC-UV non-targeted fingerprinting approaches were evaluated in this work to address honey characterization, classification, and authentication based on honey botanical variety. The first method used no sample treatment and a universal reversed-phase chromatographic separation. On the contrary, the second method was based on an off-line SPE preconcentration method, optimized for the isolation and extraction of polyphenolic compounds, and a reversed-phase chromatographic separation optimized for polyphenols as well. For the off-line SPE method, the use of HLB (3 mL, 60 mg) cartridges, and 6 mL of methanol as eluent, allowed to achieve acceptable recoveries for the selected polyphenols. The obtained HPLC-UV fingerprints were subjected to an exploratory principal component analysis (PCA) and a classificatory partial least squares-discriminant analysis (PLS-DA) to evaluate their viability as sample chemical descriptors for authentication purposes. Both HPLC-UV fingerprints resulted to be appropriate to discriminate between blossom honeys and honeydew honeys. However, a superior performance was accomplished with off-line SPE HPLC-UV polyphenolic fingerprints, being able to differentiate among the different blossom honey samples under the study (orange/lemon blossom, rosemary, thyme, eucalyptus, and heather). In general, this work demonstrated the feasibility of HPLC-UV fingerprints, especially those obtained after off-line SPE polyphenolic isolation and extraction, to be employed as honey chemical descriptors to address the characterization and classification of honey samples according to their botanical origin.

A Fully Automated Online SPE-LC-MS/MS Method for the Determination of 10 Pharmaceuticals in Wastewater Samples.

The increasing use of pharmaceuticals, their presence in the aquatic environment, and the associated toxic effects, have raised concerns in recent years. In this work, a new multi-residue analytical method was developed and validated for the determination of 10 pharmaceuticals in wastewaters using online solid-phase extraction (online SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The compounds included in the method were antineoplastics (cabazitaxel, docetaxel, doxorubicin, etoposide, irinotecan, methotrexate, paclitaxel, and topotecan), renin inhibitors (aliskiren), and antidepressants (maprotiline). The method was developed through several experiments on four online SPE cartridges, three reversed phase chromatography columns, and four combinations of mobile phase components. Under optimal conditions, very low limits of detection (LODs) of 1.30 to 10.6 ng L−1 were obtained. The method was repeatable, with relative standard deviations (RSD, %) for intraday and interday precisions ranged from 1.6 to 7.8 and from 3.3 to 13.2, respectively. Recovery values ranged from 78.4 to 111.4%, indicating the reproducibility of the method. Matrix effects were mainly presented as signal suppression, with topotecan and doxorubicin being the two most affected compounds (31.0% signal suppression). The proposed method was successfully applied to hospital effluents, detecting methotrexate (4.7–9.3 ng L−1) and maprotiline (11.2–23.1 ng L−1). Due to the shorter overall run time of 15 min, including sample preparation, and reduced sample volume (0.9 mL), this on-line SPE-LC-MS/MS method was extremely convenient and efficient in comparison to the classical off-line SPE method. The proposed method was also highly sensitive and can be used for ultratrace quantification of the studied pharmaceuticals in wastewaters, providing useful data for effective environmental monitoring.

Offline SPE, Online SPE and Direct Injection. Performance Critical Comparison for the Determination of CECs in Complex Liquid Environmental Matrices

Offline SPE, Online SPE and Direct Injection. Performance Critical Comparison for the Determination of CECs in Complex Liquid Environmental Matrices

Determination of domoic acid in seawater by solid phase extraction-liquid chromatography-tandem mass spectrometry

软骨藻酸(domoic acid, DA)是一种由海洋硅藻产生的生物毒素,具有强烈的神经毒性,近海水环境中的DA严重威胁海洋渔业生物和人类健康,因此对近海水环境中的DA进行有效监测至关重要。该文基于固相萃取-液相色谱-串联质谱联用技术(SPE-LC-MS/MS),建立了适用于海水中痕量、超痕量DA的检测方法。针对近海水生环境中DA浓度相对较高的情况下,采用在线SPE-LC-MS/MS检测模式,可减少前处理过程,提高样品的分析效率。离线SPE结合在线SPE-LC-MS/MS可实现大洋和极地海水中含量更低的DA的检测。通过对在线固相萃取条件和液相色谱、质谱条件的优化,海水样品经过滤和酸化简单处理后直接进样0.6 mL进行在线SPE-LC-MS/MS检测,DA在10.0~500.0 ng/L范围内线性关系良好(线性相关系数R2=0.9992),检出限(LOD)和定量限(LOQ)分别为4.0和10.0 ng/L,并且具有较好的方法回收率(≥81.0%)和精密度(RSD≤4.2%),表明方法可用于近海海水中痕量DA的检测。通过对离线固相萃取柱的选择和酸化条件的优化,80.0 mL海水样品经离线HLB固相萃取柱富集后,进行在线SPE-LC-MS/MS检测,DA在0.3~50.0 ng/L范围内线性关系良好(R2=0.9990),回收率(≥69.2%)和精密度(RSD≤4.4%)较好,LOD和LOQ分别为0.1和0.3 ng/L,说明方法的灵敏度较直接进样法大幅提升,实现了海水中超痕量DA的准确测定。这两种检测方法操作简单,样品用量小,灵敏度高,可满足近海养殖区及远岸海水中DA监测的要求。

Identification of fatty acids in fractionated lipid extracts from Palmaria palmata, Alaria esculenta and Saccharina latissima by off-line SPE GC-MS

The fatty acid profiles of the three lipid fractions, neutral lipids (NL), free fatty acids and polar lipids (PL), from the macroalgae Palmaria palmata (wild), Alaria esculenta (cultivated) and Saccharina latissima (cultivated) were studied in light of dietary important fatty acids. Blade and stipe from the macroalgae were collected at the end of the growth season (May/June) at Frøya (Trøndelag, Norway). A total of 51 fatty acids were identified in the algae, including several fatty acids novel to one or more of the algae. The NL and PL fractions of P. palmata were the most promising from a health perspective, due to a high content of eicosapentaenoic acid (10.1 ± 0.5% and 6.6 ± 0.1%, respectively) and no trans-fatty acids. In addition, these fractions had very low omega-6/omega-3 ratios (< 0.1) and can therefore be beneficial for balancing the omega-6/omega-3 ratio in the diet. The NL fraction of A. esculenta had the highest content of monounsaturated- and polyunsaturated fatty acids (20.9 ± 1.4 and 21.8 ± 1.9% of alga, respectively), as well as the highest content of the two essential fatty acids, linoleic acid (5.3 ± 0.4% of alga) and alpha-linolenic acid (2.4 ± 0.2% of alga). Indices related to risk factors for coronary heart disease were most favourable in the NL fraction of S. latissima and the NL and PL fractions of A. esculenta.

Simultaneous determination of ten nonsteroidal anti-inflammatory drugs from drinking water, surface water and wastewater using micro UHPLC-MS/MS with on-line SPE system

A simple, accurate and sensitive micro UHPLC-MS/MS method was developed and validated for the simultaneous determination of 10 nonsteroidal anti-inflammatory drugs (NSAIDs) from different environmental matrices. The micro LC ‒ on-line SPE method described in this study allowed to determine the selected drugs at ultra-trace levels without the most commonly used complex off-line SPE sample preparation procedures. The presented method is capable of reaching satisfactory low LOQ values with analysing the sample directly after being diluted with water. In order to attain high sensitivity, mass spectrometry was carefully optimized for the analysis of the drugs. Fenoprofen, flurbiprofen and naproxen were found to produce CO2 loss during ionization, forming intense [M-H-CO2]- ions instead of [M-H]-. All the other compounds were analyzed through their [M+H]+ and [M-H]- ions. Effect of mobile phase pH on ionization was also studied. Lower pH resulted in higher ion intensities. For this reason, a reversed phase chromatographic separation was applied at pH 3.1 with formic acid at concentration of 0.01%. Matrix effects have been evaluated during validation and sample dilution was optimized focusing on the lowest achievable LOQ values. Analytes were determined from drinking water directly, from surface water and wastewater following dilution with purified water by 2 : 8 (v/v) and 1 : 9 (v/v), respectively. Finally, the method was applied to real sample analysis.

Study of sample preparation for determination of endocannabinoids and analogous compounds in human serum by LC–MS/MS in MRM mode

Endocannabinoids are lipids with a key role in physiological processes such as the immune response or the metabolism. This involvement explains their association to pathologies such as cancer, obesity or multiple sclerosis. The determination of endocannabinoids constitutes a challenge for clinical laboratories due to the variety of biological matrices and the wide range of concentrations at which they can be found. This research deals with the comparison of three sample preparation strategies (viz., on-line SPE, off-line SPE for interferents removal, and protein precipitation) for subsequent LC–MS/MS analysis of 14 endocannabinoids and analogous compounds in serum. As a result, the on-line coupling between SPE and LC–MS/MS is proposed as the best approach for this determination. The proposed method allows full automation of the overall process, shortening of the analysis time, and avoidance of errors associated with sample preparation steps. The improvement in sensitivity and selectivity thus achieved allows obtaining quantification limits at the pg mL−1 level, which makes possible the application of the method for clinical studies.

Profiling of polyunsaturated fatty acids in human serum using off-line and on-line solid phase extraction-nano-liquid chromatography-quadrupole-time-of-flight mass spectrometry

Polyunsaturated fatty acids (PUFAs) play a pivotal role in the biological effects, and are the potential biomarkers for some diseases. However, the structural diversity and similarity, the low concentration, and the interference of high abundant endogenous components challenge the PUFAs profiling. Herein, a novel analytical approach, off-line and on-line solid phase extraction-nano-liquid chromatography-quadrupole-time-of-flight mass spectrometry (off-line and on-line SPE-nano-LC-Q-TOF-MS), was established to monitor the PUFAs. The combination of off-line and on-line SPE removed most of impurities, and the recoveries ranged from 80.1% to 93.0% and the matrix effects were from 85.1% to 92.8%. Using this method, 51 PUFAs could be separated well and quantified with the limits of quantification between 0.006 and 2.2 pg. Finally, this developed method was applied successfully to simultaneously qualify and quantify the potential biomarkers in the allergic patients. 21 PUFAs including LTB4, 5S-, 11S-, 15S-HETE and 15S-HEPE showed significant differences. Our study indicated that the established method has the potential to sensitively and accurately determine the PUFAs in biological samples.

A strategy of utilizing Zn(II) as metallic pivot in room temperature ionic liquid to prepare molecularly imprinted polymers for compound with intramolecular hydrogen bonds

A method of preparing molecularly imprinted polymers (MIPs) with Zn(II) as a metallic pivot was adopted to solve the problem of imprinting compound with intramolecular hydrogen bonds by forming stronger coordination binding interaction among the template-functional monomer-Zn2+ complex. A ternary porogenic system including dimethyl sulfoxide, dimethylformamide, and room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was employed to fabricate imprinted monolith with high porosity and good flow-through properties, in which chicoric acid (CA), zinc acetate, 4-vinylpyridine (4-VP), and ethylene glycol dimethacrylate (EDMA) was the template, metallic ion, functional monomer, as well as crosslinker, respectively. The influence of polymerization factors including the 4-VP-CA ratio, monomer-crosslinker ratio, template-Zn2+ ratio on imprinting factors was systematically investigated. When the ratio of 4-VP to CA was 24:1, the greatest IF value (24.81) was achieved on the CA-MIP prepared with zinc acetate. In addition, off-line SPE with the optimal MIPs monolith led to high purity of CA (98.0% ± 0.5%) from extraction of Cichorium intybus L. roots with the recovery of 77.5% ± 2.5% (n = 6). As a conclusion,the strategy of introducing metal ions as metal pivot to prepare MIPs was a powerful method for the MIPs synthesis to the template molecules with intramolecular hydrogen bonds.

Simultaneous determination of thirteen different steroid hormones using micro UHPLC-MS/MS with on-line SPE system

Ultratrace analysis of sample components requires excellent analytical performance in terms of limits of quantitation (LOQ). Micro UHPLC coupled to sensitive tandem mass spectrometry provides state of the art solution for such analytical problems. Using on-line SPE with column switching on a micro UHPLC–MS/MS system allowed to decrease LOQ without any complex sample preparation protocol. The presented method is capable of reaching satisfactory low LOQ values for analysis of thirteen different steroid molecules from human plasma without the most commonly used off-line SPE or compound derivatization. Steroids were determined by using two simple sample preparation methods, based on lower and higher plasma steroid concentrations. In the first method, higher analyte concentrations were directly determined after protein precipitation with methanol. The organic phase obtained from the precipitation was diluted with water and directly injected into the LC–MS system. In the second method, low steroid levels were determined by concentrating the organic phase after steroid extraction. In this case, analytes were extracted with ethyl acetate and reconstituted in 90/10 water/acetonitrile following evaporation to dryness. This step provided much lower LOQs, outperforming previously published values. The method has been validated and subsequently applied to clinical laboratory measurement.

Preconcentration of β‐blockers using functionalized ordered mesoporous silica as sorbent for SPE and their determination in waters by chiral CE

A method for simultaneous separation and determination of four enantiomeric pairs of β-blockers in waters by chiral CE has been developed. Off-line SPE was employed using functionalized ordered mesoporous silica as sorbent. Separation by CE was achieved using a BGE composed by methylated-β-CD (1.25% w/v) dissolved in a 50mM phosphate buffer (pH 2.5) and 30°C, with good chiral resolution for all enantiomers. Mesoporous silica functionalized with octadecyl groups (denoted SBA15-C18) was prepared by a postsynthesis method and applied for the preconcentration of atenolol, propranolol, metoprolol, and pindolol enantiomers in waters by off-line SPE. Under optimized conditions, a preconcentration factor of 300 was achieved, employing 100 mg of SBA15-C18 as sorbent, with recoveries between 96 and 105% in tap water and good repeatability (% RSD = 7-11%, n=6). Commercial C18 amorphous silica (ExtraBondR C18 ) was also tested as sorbent for SPE, but results revealed better extraction capacity with higher recoveries for the SBA15-C18 material. The analytical characteristics of the off-line SPE-chiral CE method were evaluated, showing good precision, linearity, and accuracy with method quantification limits between 5.3 and 13.7μg/L for all enantiomers. The SBA15-C18 material allowed the extraction of four enantiomeric pairs of β-blockers spiked in tap water, river water, and ground water with recoveries between 58 and 105%.

A rapid and fully automatic method for the accurate determination of a wide carbon-chain range of per- and polyfluoroalkyl substances (C4–C18) in human serum

A rapid and fully automatic method for determining 21 per- and polyfluoroalkyl substances (with carbon chains ranging from C4 to C18, including 13 PFCAs, 5 PFSAs, 2 Cl-PFESAs, and PFOSA) in human serum samples was developed. The HPLC parameters, Turboflow column, mobile phase, sample injection volume, loading flow rate, and sample cleanup and elution time were optimized. 25μL serum sample was directly injected into the developed on-line Turboflow SPE HPLC–MS/MS system for analysis after dilution. Matrix effects were corrected due to the matrix removal efficiency of the Turboflow column and sufficient types of internal isotope standards that were used. The established method showed a good linearity (r2>0.99), rapid processing time (20min per sample), satisfactory recoveries (matrix spiked recoveries range from 84.6% to 114%) and precision (intra-day and inter-day RSDs ranged from 1.5% to 9.2% and from 1.1% to 7.0%, respectively). The limits of detection (LODs) of the 21 analyzed PFASs were between 0.008 and 0.19ngmL−1. The LODs of short- and long-chain PFASs, such as PFBA, PFPeA, PFHxDA, and PFODA, were 0.008, 0.022, 0.15 and 0.19ngmL−1, respectively; the spiked recoveries of these PFASs were 101, 105, 87.1, and 85.8%, respectively. Both the LODs and recoveries were better than previous studies. Further, serum PFASs concentrations detected by the presented on-line SPE method were consistent with the traditional off-line SPE method (r: 0.98–0.99), which verified the accuracy and applicability of the present method. The method shows good practical prospects in the analysis of trace per- and polyfluoroalkyl substances in human serum.

Liquid chromatography mass spectrometry determination of perfluoroalkyl acids in environmental solid extracts after phospholipid removal and on-line turbulent flow chromatography purification

An on-line TFC (Turbulent Flow Chromatography) clean up procedures coupled with UHPLC–MS/MS (Ultra High Performance Liquid Chromatography Mass Spectrometry) multi-residue method was developed for the simultaneous determination of 8 perfluroalkyl carboxylic acids (PFCA, from 5 to 12 carbon atoms) and 3 perfluoroalkyl sulfonic acids (PFSA, from 4 to 8 carbon atoms) in environmental solid matrices. Fast sample preparation procedure was based on a sonication-assisted extraction with acetonitrile. Phospholipids in biological samples were fully removed by an off-line SPE purification before injection, using HybridSPE® Phospholipid Ultra cartridges.The development of the on-line TFC clean-up procedure regarded the choice of the stationary phase, the optimization of the mobile phase composition, flow rate and injected volume.The validation of the optimized method included the evaluation of matrix effects, accuracy and reproducibility. Signal suppression in the analysis of fortified extracts ranged from 1 to 60%, and this problem was overcome by using isotopic dilution. Since no certified reference materials were available for PFAS in these matrices, accuracy was evaluated by recoveries on spiked clam samples which were 98–133% for PFCAs and 40–60% for PFSAs. MLDs and MLQs ranged from 0.03 to 0.3ngg−1 wet weight and from 0.1 to 0.9ngg−1 wet weight respectively. Repeatability (intra-day precision) and reproducibility (inter-day precision) showed RSD from 3 to 13% and from 4 to 27% respectively. Validated on-line TFC/UHPLC–MS/MS method has been applied for the determination of perfluoroalkyl acids in different solid matrices (sediment, fish, bivalves and bird yolk).

Overestimation of 25-hydroxyvitamin D3 by increased ionisation efficiency of 3-epi-25-hydroxyvitamin D3 in LC-MS/MS methods not separating both metabolites as determined by an LC-MS/MS method for separate quantification of 25-hydroxyvitamin D3, 3-epi-25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in human serum.

An LC-MS/MS method was developed for simultaneous quantification of 25-hydroxyvitamin D3 (25(OH)D3), 3-epi-25(OH)D3, and 25(OH)D2 in human serum. Sample preparation consisted of protein precipitation followed by off-line SPE. Calibration curves for each vitamin D metabolite were constructed in phosphate-buffered saline with 60 g/L albumin including its corresponding stable isotope labelled (SIL) internal standard. A pentafluorophenyl (PFP) analytical column was used to resolve 25(OH)D3 from 25(OH)D2 and 3-epi-25(OH)D3, followed by SRM registration using positive ESI-MS/MS. Accuracy was assessed from measurement of samples with NIST reference method procedure (RMP) assigned values. The PFP LC-MS/MS method was compared to an in-house C18 column LC-MS/MS method, not resolving 25(OH)D3 from 3-epi-25(OH)D3, using adult and newborn samples. Intra-assay and inter-assay coefficients of variation were less than 4% and 7.5%, respectively for all three vitamin D metabolites; lower limits of quantification were 1, 1 and 2 nmol/L and linearity of methods were 1-500, 1-200 and 2-500 nmol/L for 25(OH)D3, 3-epi-25(OH)D3 and 25(OH)D2, respectively. The PFP LC-MS/MS method showed minimal bias to the NIST RMP. Method comparison revealed that in the C18 LC-MS/MS method, the 3-epi-25(OH)D3 concentration is overestimated inadvertently not only from co-elution of both analytes, but also by an additional 30-40% higher ionisation efficiency of 3-epi-25(OH)D3 when compared to 25(OH)D3. This accurate LC-MS/MS method allows the simultaneous measurement of 25(OH)D3, 3-epi-25(OH)D3, and 25(OH)D2 in human serum. Due to increased ionisation efficiency, the contribution of the 3-epi-25(OH)D3 metabolite to the total 25(OH)D3 concentration is significantly overestimated in MS methods that do not resolve 3-epi-25(OH)D3 from 25(OH)D3 and may compromise its use in infant samples known to have significant amounts of 3-epi-25(OH)D3.

Improvements in analytical methodology for the determination of frequently consumed illicit drugs in urban wastewater

Rapid and sensitive analytical methodology based on ultra high-performance liquid chromatography-tandem mass spectrometry has been developed for the determination of widely consumed drugs of abuse (amphetamines, MDMA, cocaine, opioids, cannabis and ketamine) and their major metabolites in urban wastewaters. Sample clean-up and pre-concentration was performed by a generic off-line SPE procedure using Oasis HLB. Special effort was made to incorporate amphetamine, which was found highly problematic in the wastewater samples tested, including an additional clean-up with Oasis MCX SPE and dispersive primary secondary amine. Correction for possible SPE losses or degradation during storage was made by the use of isotope-labelled internal standards (ILIS), available for all compounds, which were added to the samples as surrogates. Although ILIS were also efficient for matrix effects correction, the strong ionization suppression observed was not eliminated; therefore, a four-fold dilution prior to SPE was applied to influent wastewaters and a low injection volume was selected (3 μL), in order to reach a compromise between matrix effects, chromatographic performance and sensitivity. The method was validated at 25 and 200 ng L(-1) (effluent), and 100 and 800 ng L(-1) (influent), obtaining limits of quantification (i.e. the lowest level that the compound can be quantified and also confirmed with at least two MS/MS transitions) between 0.4-25 ng L(-1) (effluent) and 2-100 ng L(-1) (influent). The applicability of the method was demonstrated by analysis of 14 influent and 14 effluent wastewater samples collected over 2 weeks in Castellón (Spain) within a European collaborative study.

SPE of Phenols on New Amine - Based Copolymers

Porous microspheres, copolymers: bis [4(2-hydroxy-3-methacryloyloxypropoxy)-phenysulfide (BES.DM) and glycidyl methacrylate (GMA) have been prepared by suspension-emulsion polymerization. The copolymer (BES.DM+GMA) including reactive epoxide rings was modified with three amines: butylenediamine (BDA), diethylenetriamine (DETA), triethylenetetramine (TETA). Next, attachment of HCO3- species to the primary amine groups took place.The prepared porous polymers were used as adsorbents in off-line SPE experiments. A mixture of phenol (PH), 2-chlorophenol (ChP), 2,4-dichlorophenol (DChP) and 2,4,6-trichlorophenol (TChP) as testing compounds was applied.Depending on the way of chemical modification, the prepared adsorbents possessed diverse sorption properties towards the testing compounds. Competition of the phenolic compounds for active sites presented on the polymer surface was observed. The most effective in water purification process were polymers possessing both amine and bicarbonate groups. The best recovery results were obtained for 2,4-dichlorophenol.

Quantitative HPLC-MS analysis of nucleotide sugars in plant cells following off-line SPE sample preparation

An analytical workflow was developed for the absolute quantification of uridine diphosphate (UDP)-sugars in plant material in order to compare their metabolism both in wild-type Arabidopsis thaliana and mutated plants (ugd2,3) possessing genetic alterations within the UDP-glucose dehydrogenase genes involved in UDP-sugar metabolism. UDP-sugars were extracted from fresh plant material by chloroform-methanol-water extraction and further purified by solid-phase extraction with a porous graphitic carbon adsorbent with extraction efficiencies between 80 ± 5 % and 90 ± 5 %. Quantitative determination of the UDP-sugars was accomplished through HPLC separation with a porous graphitic carbon column (HypercarbTM) which was interfaced to electrospray ionization Orbitrap mass spectrometry. The problem of instable retention times due to redox processes on the stationary phase were circumvented by grounding of the column effluent and incorporation of a column regeneration procedure using acetonitrile-water containing 0.10 % trifluoroacetic acid. The method was calibrated using external calibration and UDP as internal standard. Calibration functions were approximated by first- or second-order regression analysis for concentrations spanning three orders of magnitude. Upon injecting sample volumes of 2.65 μL, the limits of detection for the UDP-sugars were in the 70 nmol L−1 range. Six different UDP-sugars, including UDP-glucose, UDP-galactose, UDP-arabinose, UDP-xylose, UDP-glucuronic acid, and UDP-galacturonic acid were found in concentrations of 0.4 to 38 μg/g plant material. Data evaluation by analysis of variance (ANOVA) revealed statistically significant differences in UDP-sugar concentrations between wild-type and mutant plants, which were found to conclusively mirror the impaired metabolic pathways in the mutant plants. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-014-7746-3) contains supplementary material, which is available to authorized users.