Simultaneous solid-phase extraction of acidic, neutral and basic pharmaceuticals from aqueous samples at ambient (neutral) pH and their determination by gas chromatography-mass spectrometry

Seven polymeric solid-phase extraction (SPE) sorbents were evaluated with regard to their ability to extract acidic, neutral and basic pharmaceuticals and estrogens simultaneously from water at neutral pH. Highest recoveries (70-100%) for the majority of the analytes were obtained with styrene-methacrylate and styrene-N-vinylpyrrolidone co-polymers. The latter one (Oasis HLB) was chosen for further refinement of an extraction method for the quantitative determination of acidic and neutral drugs in surface water samples at detection limits below 1 ng/l. A sequential elution protocol was applied for clean-up and separation of the extracted analytes into fractions suitable for further compound specific processing. The neutral analytes as well as the acidic compounds after derivatisation were quantified by GC-MS. Caffeine, ibuprofen, its metabolites and diclofenac were detected in river water samples in the 1-100 ng/l range.     

Dual gradient LC method for the determination of pharmaceutical residues in environmental samples using a monolithic silica reversed phase column

Detailed below is a simple reversed-phase liquid chromatography (RP-LC) method for the simultaneous separation of up to 21 acidic, basic, and neutral pharmaceuticals using Merck Chromolith Performance RP-C18e monolithic columns with direct ultraviolet (UV) absorption detection. By simultaneously applying a solvent elution gradient program with a mobile phase flow gradient, both a decrease in the overall analysis time and a general increase in peak efficiencies were observed. Mobile phase pH and buffer concentration were optimised using the overall resolution product under applied gradient conditions. Under optimised conditions peak area reproducibility (n?=?6) ranged between 0.4 and 9.3%, determined at the method LOQ level. For real sample analysis pharmaceutical residues were extracted using an optimised solid phase extraction (SPE) procedure, utilising Strata-X extraction cartridges, which overall provided the highest relative recovery data in comparison with four other commercially available SPE sorbents (17 out of 20 residues investigated had recoveries over 70%). Complete method precision, including all sample pre-treatment and LC analysis for six spiked river water samples at the 1 and 2?µg?L^?1 level was between 10 and 29%. Using 1?L volumes of 1?µg?L^?1 spiked estuarine water samples, the majority of detection limits were found to be in the 10–50?ng?L^?1 range.     

Semi-automated, solid-phase extraction procedure for liquid chromatographic determination of papaverine, diltiazem, desipramine and nicardipine in urine

Summary A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure is reported for the assay of papaverine, diltiazem, desipramine and nicardipine in urine. Disposable extraction cartridges (DECs) filled with C18, C8, C2, CH and PH silica-bonded phases were used. The effect on recovery of sample pH, composition of washing and elution solvents and nature of SPE cartridge were evaluated. The selectivity of SPE was examined using spiked urine samples and the PH cartridge gave rise to the cleanest extracts. Phenyl cartridges were conditioned with methanol and acetic acid-sodium acetate buffer. Urine sample was buffered and then applied to the DEC. The washing step was with acetone-water and subsequently with methanol-acetate buffer. The analytes were eluted with methanol-acetate buffer. The extract was evaporated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with UV detection at 212 nm. Recoveries of the tested compounds from spiked urine samples using the PH cartridge were in all cases>80%. The within-day and between-day repeatabilities were<5% and 9%, respectively.     

Electromembrane extraction using two separate cells: A new design for simultaneous extraction of acidic and basic compounds

Simultaneous extraction of acidic and basic analytes from a sample is seen to be a challenging task. In this work, a novel and efficient electromembrane extraction (EME) method based on two separate cells was applied to simultaneously extract and preconcentrate two acidic drugs (naproxen and ibuprofen) along with a basic drug (ketamine). Once both cells were filled with the sample solution, basic drug was extracted from one cell with the other cell used to extract acidic drugs. The employed supported liquid membranes for the extraction of acidic and basic drugs were 2‐ethyl hexanol and 1‐octanol, respectively. Under an applied potential of 250 V in the course of the extraction process, acidic, and basic drugs were extracted from a 3.0 mL aqueous sample solution into 25 μL acceptor solutions. The pH values of the donor and acceptor solutions in the cathodic cell were 5.0 and 1.5, respectively, the corresponding values in the anodic cell were, however, 8.0 and 12.5, respectively. The rates of recovery obtained within 20 min of extraction time at a stirring rate of 750 rpm ranged from 45 to 54%. With correlation coefficients ranging from 0.990 to 0.996, the proposed EME technique provided good linearity over a concentration range of 20–1000 ng/mL. The LOD for all drugs was found to be 6.7 ng/mL, while reproducibility ranged from 7 to 12% (n = 5). Finally, applying the proposed method to determine and quantify the drugs in urine and wastewater samples, satisfactory results were achieved.     

Solid-phase extraction of soy isoflavones

An automated method using solid-phase extraction (SPE) for the concentration and clean-up of soy isoflavone extracts is proposed in this work. Using a standardized sample (0.1 g of a freeze dried soybean extract/25 mL of water); eight SPE cartridges with a wide range of sorbents (C18, divinylbenzene and modified divinylbenzene) from different suppliers were evaluated and compared. A large variation on SPE cartridges performance was observed, especially regarding retention and breakthrough volume of isoflavones during sample load and washing steps. The most effective cartridges were the divinylbenzene based cartridges, especially Strata X (from Phenomenex) and HLB oasis (from Waters). Using Strata X cartridges, several extraction parameters, such as sample loading flow (5-15 mL min(-1)), extracting solvent volume (2-6 mL of methanol), pH of the extracting solvent and the necessity of drying the sorbent before elution, were evaluated to provide a fast, specific, quantitative and reproducible SPE method. The optimized method consists of conditioning the cartridge with 10 mL of methanol and 10 mL of water (10 mL min(-1)), loading 25 mL of the standardized extract onto the cartridges (5 mL min(-1)), washing the cartridge with 10 mL of water (10 mL min(-1)) and finally eluting with 4 mL of methanol (10 mL min(-1)). Mean isoflavones recovery was 99.37% and mean intra- and inter-day reproducibility was higher than 98%. The developed sample clean-up/concentration (6.25:1) method takes less than 10 min and can be used in the analysis of isoflavones from soy extracts.     

Stability of sulfonated derivatives of benzene and naphthalene on disposable solid-phase extraction pre-columns and in an aqueous matrix

The stability of 14 sulfonated benzene and naphthalene compounds was investigated using polymeric solid-phase extraction cartridges, based on the styrene-divinylbenzene polymer Isolute ENV+. Several different storage conditions were tested to carry out the stability study in polymeric cartridges, which included storage at room temperature, at 4 degrees C and at -20 degrees C, during a period of up to 3 months. An additional stability study was carried out, not with the polymeric solid matrix, but in an aqueous matrix. This study was performed storing the samples at 4 degrees C, during 2 months under three different conditions: acidifying the water sample to pH 2.5-3 with sulfuric acid, adding 1% of formaldehyde (additive used in waste water analyses), and storing the water sample at 4 degrees C without any additives. The extraction of the SPE process is analyzed by ion-pair chromatography-electrospray mass spectrometry, in the negative ion mode. This study showed that the stability of polar aromatic sulfonic acids on disposable polymeric cartridges and in the water matrix is related to temperature and pH, respectively. Target aromatic sulfonated compounds stored in polymeric solid-phase extraction cartridges, are more stable at lower temperatures. The target analytes showed also good stability when stored in water at acidic pH. From the different analytes studied, substituted naphthalenesulfonates suffered more degradation than mononaphthalenesulfonates or benzenesulfonates under the experimental conditions of this work.     

Determination of multiple pharmaceutical classes in surface and ground waters by liquid chromatography–ion trap–tandem mass spectrometry

This paper describes development, optimization and application of analytical method for determination and reliable confirmation of nineteen pharmaceuticals from different therapeutic classes (antibiotics—β-lactams, cephalosporines, sulfonamides, macrolides and tetracyclines; benzodiazepines; antiepileptics and analgoantipyretics) in surface and ground waters at ng l⁻¹ levels. Water samples were prepared using solid-phase extraction and extracts were analyzed by liquid chromatography–ion trap–tandem mass spectrometry with electrospray ionization in both positive and negative ionization mode. The efficiency of ten different SPE cartridges to extract diverse compounds from water was tested. The pH-value of the water sample, the volume of elution solvent and the sample volume were optimized. Matrix effect, especially pronounced for cephalexin and metamizole, was eliminated using matrix-matched standards. It was determined that extraction should be performed at pH ∼ 7.5, i.e. without pH adjustment, and at pH 3, depending on the analyte. Azithromycin, doxycycline and acetylsalicylic acid must be extracted in acidic environment, whereas extraction of paracetamol, ampicillin, erythromycin and metamizole should be performed without pH adjustment. Repeatability of the method was generally lower than 20%. The estimated limits of detection were in the range from 0.15 to 12.46 ng l⁻¹. The method was applied to 26 water samples for monitoring of selected drug residues. Results revealed the presence of carbamazepine (80% of water samples), azithromycin (23%), as well as trimethoprim and paracetamol (both 15%). The most striking was the false positive signal of diclofenac in every analyzed water sample. Confirmation of the positive results was performed by repeated injection of the positive sample extracts using confirmatory method with additional transitions.     

固相萃取柱上衍生气相色谱-质谱法测定水中烷基酚

以烷基酚(APs)主要降解产物辛基酚(4-t-OP)、壬基酚(4-n-NP)为研究对象,建立了固相萃取(SPE)柱上衍生化、气相色谱-质谱(GC-MS)法测定水中APs的分析方法。以C18柱为固相萃取柱、N,O-(三甲基硅)三氟乙酰胺(BSTFA)为硅烷化试剂,设计五因素四水平正交实验L16(45),对衍生化影响因素、衍生化溶剂、衍生化时间以及SPE主要影响因素pH值、盐度和洗脱剂进行优化;在优化条件下,方法的回收率(高于80%)和重现性(RSD低于10%)结果令人满意,4-t-OP和4-n-NP的仪器检出限分别为3.35ng/L和6.38ng/L。采用建立的方法,回收率略高于传统的SPE萃取衍生法,具有有机溶剂用量少,方法简单快速、灵敏度高的特点,适用于河水和海水中痕量烷基酚的快速测定。     

Solid phase extraction system for vitamin D and its major metabolites in human plasma

A new procedure using C18 and silica cartridges for the extraction and subsequent separation of vitamin D and its major metabolites from plasma has been developed and compared to a conventional extraction procedure with respect to lipophilic material extracted as evaluated by high-performance liquid chromatographic profiles. The C18 cartridges were efficient in extracting all compounds tested while subsequent chromatography of the extract on silica cartridges was effective in resolving vitamin D and its metabolites based on increasing polarity. High-performance liquid chromatographic profiles of each silica cartridge fraction clearly demonstrated that the newly conceived solid phase extraction was superior to conventional extraction methods with respect to cleanliness of sample fractions. This difference in lipophilic load between the new and conventional extraction systems was most apparent in the vitamin D and 25-hydroxyvitamin D containing fractions. The new extraction system can be used when total extraction and subsequent analysis of vitamin D and its major metabolites is desired.     

Flow injection Fourier transform infrared determination of nicotine in tobacco

A fully automated procedure is proposed for the Fourier transform infrared (FTIR) determination of nicotine in tobacco. The method is based on the on-line extraction of nicotine with CHCl3. Samples, weighed inside empty extraction cartridges, were humidified with NH3 and the cartridges were installed in a flow manifold in which they were extracted with 2 ml CHCl3 for 2 min, then 400 microliters of the extract were introduced into a micro-flow cell using a carrier of CHCl3 and the IR spectrum was registered continuously. The absorbance, in the wavenumber range 1334-1300 cm-1, was measured, obtaining a peak as a function of time. The area of this peak was interpolated on a calibration line established from standard solutions of nicotine in chloroform treated in the same way as samples. The method provided a limit of detection of 0.1 mg ml-1 nicotine, an RSD lower than 2% and a sampling frequency of the whole procedure of 6 h-1. Results obtained for natural samples of cut tobacco and cigar compared well with those obtained by a batch FTIR procedure, involving an off-line extraction with a total time of 16 min. However, for yellow tobacco cigarette, an on-line extraction time of 10 min was required to obtain a good recovery of nicotine.     

Clay‐Na as a sorbent for the extraction of anti‐inflammatory compounds in water samples

In this work, clay‐Na particles are used as the adsorbent for the solid‐phase extraction of acidic compounds. The novel sorbent under study is based on high‐specific surface area, cation‐exchange capacity designed specifically to offer ion‐exchange properties with the goal being to selectively extract a group of acidic compounds. The effects of the extraction parameters including extraction elution solvent, sample volume and pH. In optimum conditions, the repeatability for one fiber (n = 3), expressed as % relative standard deviation, was between 0.3 and 4.3% for the acid compounds. The detection limits for the studied acidic compounds were between 0.1–0.6 μg/L. The developed method offers the advantages of being simple to use and having a low cost of equipment.     

Optimization of solid-phase extraction for the liquid chromatography-mass spectrometry analysis of harpagoside, 8-para-coumaroyl harpagide, and harpagide in equine plasma and urine

Solid-phase extraction cartridges among those usually used for screening in horse doping analyses are tested to optimize the extraction of harpagoside (HS), harpagide (HG), and 8-para-coumaroyl harpagide (8PCHG) from plasma and urine. Extracts are analyzed by liquid chromatography coupled with multi-step tandem mass spectrometry. The extraction process retained for plasma applies BondElut PPL cartridges and provides extraction recoveries between 91% and 93%, with RSD values between 8 and 13% at 0.5 ng/mL. Two different procedures are needed to extract analytes from urine. HS and 8PCHG are extracted using AbsElut Nexus cartridges, with recoveries of 85% and 77%, respectively (RSD between 7% and 19%). The extraction of HG involves the use of two cartridges: BondElut PPL and BondElut C18 HF, with recovery of 75% and RSD between 14% and 19%. The applicability of the extraction methods is determined on authentic equine plasma and urine samples after harpagophytum or harpagoside administration.     

Preconcentration of trace amounts of beryllium in water samples on octadecyl silica cartridges modified by quinalizarine and its determination with atomic absorption spectrometry

A simple method has been developed for rapid and selective extraction, preconcentration and determination of trace amounts of beryllium. The extraction is carried out by octadecyl silica cartridge, modified with quinalizarine as a chelating agent. The effect of different parameters, such as sample matrix, flowrates of sample solution and eluent, pH, type and least amount of eluent for elution of Be(+2) ions from cartridge, breakthrough volume and limit of detection, were evaluated. Also, the effects of various cationic and anionic interferences on percent recovery of Be(+2) were studied. Be(+2) was extracted from solution at pH 6-6.6 and was eluted from modified cartridge with 5 ml of 0.5 M HNO(3). Extraction efficiencies >99% were obtained by elution of the cartridges with minimal amount of eluent. A preconcentration factor of 200 and a detection limit of 200 ng per 1000 ml were obtained. The method was applied to the recovery and determination of Be(+2) in different water and alloy samples.     

Determination of organotin compounds (OTC) at low levels in seawater by solid-phase extraction (SPE) and gas chromatography-pulsed flame photometric detection (GC-PFPD)

In this work, a simple, sensitive and affordable analytical method for the simultaneous determination of nine organotin compounds (butyltins, phenyltins and methyltins) in seawater using solid-phase extraction (SPE) and gas chromatography-pulsed flame photometric detection was developed and validated. The performance of three different SPE cartridges (Envi C₁₈, Oasis HLB and Oasis MCX) and three elution solvents of different polarity (hexane, methanol and acetonitrile) was evaluated. The extraction parameters, such as solvent volume, presence of complexing and ion-pairing reagents, sample volume and pH and breakthrough volume, were also investigated. Tributyltin, as the organotin compound of special interest, was efficiently extracted using any of the cartridges and solvents tested. However, the simultaneous extraction of all nine organotin compounds was the most efficient using reversed-phase Envi C₁₈ cartridge and 0.1% (w/v) tropolone in methanol as eluent. The optimised method resulted in good recovery, precision and linearity for all compounds, particularly for tri- and disubstituted species. Method detection limits ranged from 0.22 to 1.27 ng(Sn) L^?1 for butyltins, 0.37 to 4.91 ng(Sn) L^?1 for phenyltins and 0.45 to 1.16 ng(Sn) L^?1 for methyltins. The accuracy of butyltins determination was further verified by the comparison with purchased derivatised standards. The developed method was successfully applied to the environmental samples.     

Combined method of solid-phase extraction and GC-MS for determination of acidic,neutral, and basic emerging contaminants in wastewater (Poland)

In this study an analytical procedure of solid-phase extraction (SPE) followed by gas chromatography mass spectrometry (GC-MS) was elaborated and validated for simultaneous determination of 11 acidic, neutral and basic emerging contaminants in wastewater. The most frequently used pharmaceuticals were studied, i.e. five anti-inflammatory drugs – ibuprofen, diclofenac, ketoprofen, naproxen and salicylic acid, an antiepileptic drug carbamazepine, clofibric acid, antibacterial triclosan, a plasticiser bisphenol A and two β-blockers – propranolol and metoprolol. Sample enrichment was performed using Oasis HLB sorbent. Sample pH and sorbent washing step during the solid-phase extraction were optimised on real wastewater samples. Recoveries of the most polar acidic compounds diminished substantially when the alkalinity of the sample loaded into the cartridge increased. Thus finally wastewater was extracted at pH 2.0. Before elution, sorbent was washed subsequently with 5% methanol in water and n-hexane, which resulted in best recoveries of most of the target compounds and reduced a co-elution phenomena with respect to β-blockers. The optimised method was successfully applied to influent and effluent samples from wastewater treatment plant, Krakow, Poland. All target compounds except propranolol were identified in wastewater at a concentration up to 12.8 µg L^?1.     

General and selective isolation procedure for high-performance liquid chromatographic determination of anabolic steroids in tissues

A multi-residue method has been developed for the determination of anabolic steroids in animal tissue. The analytes are extracted from tissue with methanol and the extract is subjected to two solid-phase extractions, one using a non-specific adsorbing material, such as graphitized carbon black (Carbopack B), and the other Amberlite CG-400 I in the OH form. This procedure allowed the neutral anabolics (testosterone, trenbolone and progesterone) to be isolated and separated from the acidic type (phenolic group), such as diethylstilbestrol, oestradiol, zeranol/zearalenone and their respective metabolites. The determination was effected using high-performance liquid chromatography with different detectors (ultraviolet, fluorimetric and electrochemical). Several analytical parameters were studied: chromatographic conditions, recoveries, evaporation step, solvent flow-rate, cartridges reusability, interference of plastic cartridges. For all the anabolics investigated the recoveries were greater than 83.6%.     

Simultaneous determination of endocrine disrupting phenolic compounds and steroids in water by solid-phase extraction-gas chromatography-mass spectrometry

A solid-phase extraction (SPE)-gas chromatography (GC)-mass spectrometry (MS) analytical method for the simultaneous separation and determination of endocrine disrupting chemicals (EDCs) from water samples is described in detail. Important and contrasting EDCs including estrone, 17beta-estradiol, 17beta-ethynylestradiol, 16beta-hydroxyestrone, 4-nonylphenol, bisphenol A and 4-tert-octylphenol were selected as the target compounds. The SPE technique, followed by the derivatisation with bis (trimethylsilyl) trifluoroacetamide was used for the extraction recoveries of target compounds from water samples. A number of parameters that may affect the recovery of EDCs, such as the type of SPE cartridges, eluents, as well as water properties including pH value, and concentration of salts and humic substances were investigated. It is shown that the Oasis cartridges produced the best recoveries of target EDCs while ethyl acetate was efficient in eluting EDCs from SPE cartridges. The recovery of some EDCs was enhanced by the addition of salt, but reduced by the increase in pH value and humic acid concentration. The optimised method was further verified by performing spiking experiments in natural river water and seawater matrices, with good recovery and reproducibility for all the selected compounds. The established method was successfully applied to environmental water samples from East and West Sussex, UK, for the determination of the target EDCs.     

Electric Field-Assisted Solid Phase Extraction: Devices, Development and Application with a Cationic Model Compound

This work describes novel devices for electric field-assisted solid phase extraction (E-SPE) and an application was carried out on the antimicrobial marbofloxacin (MAR). Conventional syringe-type SPE cartridges were easily adapted to receive two electrodes that were inserted and positioned below and above the sorbent. The adapted cartridges were coupled to a flow extraction system, which consisted of an electrophoresis power supply, a peristaltic pump and a homemade SPE manifold. These devices were used to apply electric fields during the extraction of MAR from fortified buffer and milk samples. The recovery of MAR was improved (2.3 times) or reduced (4.2 times) in comparison to conventional SPE when the top electrode was used as cathode (E-SPE_(?/+)) or anode (E-SPE_(+/?)), respectively. The results demonstrated that usual SPE cartridges can be easily and inexpensively adapted for applying an electric field in SPE. It was also concluded that the electric field applied in a usual SPE cartridge can be employed as a new suitable approach to enhance the extraction efficiency of ionic compounds in a complex sample matrix.     

Simultaneous determination of various pharmaceutical compounds in water by solid-phase extraction-liquid chromatography-tandem mass spectrometry

A solid-phase extraction (SPE) followed by liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS-MS) method was developed and validated for simultaneous analysis of 11 pharmaceutical residues (propranolol, sulfamethoxazole, meberverine, thioridazine, carbamazepine, tamoxifen, mecoprop, indomethacine, diclofenac, meclofenamic acid and monensin) in environmental water samples. The collision energy chosen for the multiple reaction monitoring (MRM) experiment was optimised. A number of parameters that may affect the recovery of the pharmaceuticals, such as the type of SPE cartridges, eluents, as well as water properties including pH value, salinity and concentration of colloid and surfactant were investigated. It is shown that the Oasis HLB SPE cartridge produced the best recoveries of the target pharmaceuticals while methanol was efficient in eluting pharmaceuticals from SPE cartridges. The recovery of some target compounds was enhanced with increasing salinity, but reduced by increasing pH value, and unaffected by surfactant concentration (0-10 microg/l). The recovery of most compounds was slightly increased by the presence of colloids (0-10 mg/l), which however caused a reduction in recovery for sulfamethoxazole and meberverine. The optimised method was further verified by performing spiking experiments in river water and seawater matrices, with good recovery and reproducibility for all except two compounds. The established method was successfully applied to environmental water samples from East Sussex, UK, for the determination of the target pharmaceuticals.     

Determination of phenoxyalkanoic acids and other herbicides at the ng/ml level in water by solid-phase extraction with poly(divinylbenzene-co-N-vinylpyrrolidone) sorbent and high-performance liquid chromatography--diode-array detection

A method for the determination of phenoxyalkanoic acids and other polar compounds in environmental water samples without pH adjustment before extraction has been developed. Recoveries were calculated from 500 ml of milliQ water spiked at the level of 0.5 ng/ml using solid-phase extraction (SPE) and HPLC-DAD. Different SPE materials (RP-C18, ENV+, ENV+-C8, SAX and Oasis HLB) were tested. After method optimization, 15 of the 16 compounds studied could be extracted with recoveries better than 70% on the most suitable copolymeric poly(divinylbenzene-co-N-vinylpyrrolidone) material (Oasis HLB cartridges).