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PubMed2004

Development of a solid-phase extraction method for the determination of polychlorinated biphenyls in water.

Polychlorinated biphenyls (PCBs) in water were extracted with a rebuilt extraction unit using 47 mm C18 solid-phase extraction (SPE) disks. Three types of disks (SPEC, ENVI and Empore) were investigated for the extraction of seven PCBs from 11 reagent water spiked at two concentration levels (20 and 1000 ng/l). The Empore disks produced the best analyte recoveries (91-107% with R.S.D. of 1-8%) at the low concentration level and displayed no leaking tendency. Empore disks were therefore considered superior to ENVI and SPEC disks for the conditions outlined in this work. The obtained extracts were dried and purified in an additional clean-up step using custom-made columns containing Florisil and Na2SO4. For water containing large amounts of organic matter, a pre-filtration was included. Final analysis was carried out on a dual-column GC-electron-capture detection system with on-column injection. The optimised extraction method, including clean-up, was less time-consuming and used less hazardous organic solvents than conventional liquid-liquid extraction (LLE) methods. Recoveries were 92-102% with R.S.D. of 3-8%.

Chromatography, Gas↗
PubMed1995

Rapid and highly automated determination of morphine and morphine glucuronides in plasma by on-line solid-phase extraction and column liquid chromatography.

A high-performance liquid chromatography (HPLC) method has been developed for the determination of morphine and its main metabolites, morphine-6-glucuronide (M-6-G) and morphine-3-glucuronide (M-3-G), in plasma or cerebrospinal fluid. Samples were extracted using on-line solid-phase extraction followed by reversed-phase HPLC with fluorescence detection. Recoveries of 20 ng morphine and morphine glucuronides in plasma were over 95%. The limit of detection using 400 microliters of a biological matrix was 0.85, 3.4 and 1.0 ng/ml of M-3-G, M-6-G and morphine, respectively. Inter- and intra-day assay precision was better than 10%. The main advantages of the present described method are increased recoveries (> 95%) and a high degree of automation allowing a high speed in routine analysis. The time required for the fully automated analysis of one sample was less than 26 min.

Automation↗
PubMed2007

Pesticide multiresidue analysis in Panax ginseng (C. A. Meyer) by solid-phase extraction and gas chromatography with electron capture and nitrogen-phosphorus detection.

An analytical multi-residue method using gas chromatography coupled with electron capture and a nitrogen-phosphorus detector was investigated for the simultaneous determination of 18 commonly used insecticides and fungicides in Korean ginseng (Panax ginseng C. A. Meyer). Samples were previously extracted with an acetonitrile and cleaned up by solid-phase extraction (SPE). The calibration curves were linear, with determination coefficients higher than 0.989. Recoveries at concentrations between 0.01 and 14.9 ppm ranged from 72.3 to 117.2%, with precision, which was expressed as relative standard deviation (RSD), at values lower than 5%. The proposed method was applied to the determination of pesticide levels from 12 ginseng samples, taken from four different agricultural areas of Jeonnam province, where several insecticides and fungicides were applied. Except in one sample, tolclofos-m was the only pesticide contained at a level lower than the maximum residue limits (MRL) authorized by the Korea Food and Drug Administration (KFDA) in real ginseng samples grown for 4, 5 and 6 years.

Calibration↗
PubMed2003

Screening of pesticides via solid-phase extraction and gas chromatography.

This work describes an analytical method for the screening of pesticide residues in water. The developed method identifies and quantitates a variety of pesticides in water samples such as organochlorine, organophosphate, chloronitrile, phthalimide, dicarboximide, and triazine. The analytical technique employed for the extraction and cleanup step involves solid-phase extraction with C-18 cartridges. The identification and determination of concentration is carried out with gas chromatography. Two columns of different polarity and two specific detectors are used. An electron capture detector is used for organochrolorine, and a thermoinic detector is used for organonitrogen and organophosphate. The good resolution achieved with the temperature program and the combination of columns is shown in the chromatograms obtained. The limits of detection, percent recovery, and their respective standard deviations are determined for each product. According to the results obtained, this method permits monitoring of the pesticides mentioned, many of which are moderately to highly toxic to aquatic organisms.

Calibration↗
PubMed1997

Determination of Aconitum alkaloids in blood and urine samples. I. High-performance liquid chromatographic separation, solid-phase extraction and mass spectrometric confirmation.

Determination of four toxic Aconitum alkaloids, aconitine, mesaconitine, hypaconitine and jesaconitine, in blood and urine samples has been established using high-performance liquid chromatography (HPLC) combined with ultraviolet absorbance detection, solid-phase extraction and mass spectrometry (MS). These alkaloids were hydrolyzed rapidly in alkaline solution (half lives (t1/2) five months) and were unstable in solutions of methanol and ethanol (t1/2<one month). These alkaloids were separated on an octadecylsilica column with isocratic elution using a solvent mixture of tetrahydrofuran and 0.2% trifluoroacetic acid (14:86, v/v), which was found to be the optimal solvent of the elution systems examined. Calibration curves with UV detection were linear on injection of amounts ranging from 2.5 to 500 ng, and the limit of detection was 1 ng (S/N=3). These four alkaloids in aqueous solution were recovered almost totally by solid-phase extraction using the styrene polymer resin, Sep-Pak Plus PS-1, and were eluted using a mixture of acetonitrile and hydrochloric acid. These Aconitum alkaloids were confirmed by HPLC coupled with fast atom bombardment MS, giving their protonated molecular ions as base peaks. These alkaloids were detected by HPLC with UV detection from blood samples spiked with more than 50 ng ml(-1) of alkaloids, but were not detectable from urine samples spiked with 5 microg ml(-1) of alkaloids because of severe sample interference.

Aconitine↗
PubMed1995

Determination of urinary 4,4'-methylenedianiline and its acetylated metabolites by solid-phase extraction and HPLC analysis with UV and electrochemical detection.

An analytical procedure based on solid-phase extraction and high-performance liquid chromatography using both ultraviolet and electrochemical detection was developed to determine, without derivatization, stable urinary forms of 4,4'-methylenedianiline (MDA) and of its acetylated metabolites at the micrograms/l level, in post-shift urine from 63 exposed workers. The determination of MDA, N-acetyl MDA (MAMDA) and N,N'-diacetyl MDA (DAMDA) was achieved on the non-hydrolysed urine samples, and that of total MDA on urine samples after alkaline hydrolysis. It was necessary to protect urine samples with sulfamic acid in order to stabilize amines and to improve the precision and accuracy of the analyses. Under these conditions, unstable labile conjugates were determined as their parent stable amine. The distribution of total MDA, MDA, MAMDA and DAMDA was assessed in 116 urine samples. Their relative concentrations (arithmetic means) were found to be in the following order: total MDA > MAMDA > MDA > DAMDA. While MAMDA represented more than 50% of total MDA, MDA and DAMDA were lower than 15% and 3% respectively. Acetylation of MDA, described as a possible pathway of detoxication, is confirmed to be an important metabolization route in humans, essentially through the monoacetylated metabolite. However, the individual ratio MAMDA/total MDA was found to vary widely (roughly from 0% to 100%).

Acetylation↗
PubMed2003

Bromate assay in water by inductively coupled plasma mass spectrometry combined with solid-phase extraction cartridges.

Based on selective sorption of bromide, bromoacetic acids (BAA) and bromomethanes on solid-phase extraction (SPE) cartridges, a sensitive and convenient method was developed for the determination of bromate in waters by inductively coupled plasma mass spectrometry (ICP-MS). Dionex OnGuard Ag and reversed-phase (RP) cartridges were tested for retention characteristics for bromide, BAA and bromomethanes. When a sample acidified with nitric acid was passed through an RP cartridge, BAA and bromomethanes were retained, afterwards bromide was absorbed as a precipitate of silver bromide and bromate was unretained when the nearly neutral sample passed a combination of Ag and H cartridges. After SPE pretreatment the recovery of bromate was 96-106%, and bromide remaining in the aqueous phase was found to be less than 0.06 microg L(-1) when the original bromide concentrations were less than 5 mg L(-1). Effectiveness of stacked Ag and H cartridges in removing bromide from chloride-containing samples was also examined. Common cations and other anions did not interfere with bromate determination. The detection limit for bromate is 57 ng L(-1). This method has been applied to analyse waters from various sources, and the recovery of the spiked bromate was in the range of 92-107%.

Journal Article↗
PubMed1994

Solid-phase extraction technique for the analysis of biological samples.

This article reviews the literature on solid-phase extraction published in the last 10 years. Emphasis has been placed on dealing with samples of biological origin. The sections consist of introduction, history and development, types of columns, selection of a suitable column, types of samples, advantages and applications.

Animals↗
PubMed2006

Quantification of free and esterified sterols in Portuguese olive oils by solid-phase extraction and gas chromatography-mass spectrometry.

A simple and accurate method based on solid-phase extraction (SPE), transesterification and gas chromatography-mass spectrometry (GC-MS) was developed for the quantitative analysis of free and esterified sterols of olive oil. In order to achieve better separation of esterified and free sterols, silica and alumina SPE adsorbents were tested. Separations by silica provided more reproducible results. The transesterification of both sterol fractions was found to be more user friendly than saponification as a method to liberate the sterols from the respective esters. The free sterols were then silylated with N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) with 1% of trimethylchlorosilane (TMCS). The most favourable conditions for exploitation of this reagent were established. The optimized methodology was suitable for evaluation of free and esterified sterols in Protected Designation of Origin (PDO) olive oils and monovarietal olive oils with different maturation indices. The prevailing phytosterols in all olive oils were beta-sitosterol and campesterol. The free sterols predominated, although they seemed to decrease with the maturation of the olive fruits.

Aluminum Oxide↗
PubMed2006

Determination of bisphenol A in milk by solid phase extraction and liquid chromatography-mass spectrometry.

A simple and reliable analytical method based on solid phase extraction (SPE) and liquid chromatography coupled with electrospray ionization mass spectrometry was developed for the determination of bisphenol A (BPA) in milk. The effects of the experimental parameters of the LC-ESI-MS system (mobile phase and additives, flow rate, temperature of the ionization source, cone voltage and capillary potential) on the obtained signal were assessed and the parameters were optimized to provide maximum sensitivity and detectability. In addition, the performance of three commercial SPE sorbents (C18, PS-DVB and hydroxylated PS-DVB) was evaluated using spiked water and milk, diluted with a mixture of water-methanol (8:1). By using C18 cartridges and BPA-d(16) as internal standard, the mean relative recoveries at three fortification levels ranged between 97 and 104% and the corresponding inter-day precision (RSD%) was below 6% for 50 and 500 ng/g and below 20% for 5 ng/g fortification levels. It is shown that the ion suppression during ESI, the losses from the sample preparation procedure and the inter-day instability of LC-ESI-MS were overcome by the use of the deuterated internal standard. The concentration of BPA found in commercial canned milk samples ranged from <1.7 to 15.2 ng/g.

Animals↗
PubMed2006

The determination of nicotinic acid in plasma by mixed-mode liquid chromatography-tandem mass spectrometry following ion exchange solid phase extraction.

An assay for nicotinic acid in plasma samples has been developed using ion exchange solid phase extraction in 96-well format followed by mixed-mode ion exchange/reversed-phase liquid chromatography with positive ion tandem mass spectrometry detection. The assay avoids the need for time-consuming derivatisation procedures or involatile ion-pair chromatography reagents. The assay is linear over the wide range 0.05-20 microg/mL, based on a 100 microL sample (correlation coefficient>0.99). The assay is accurate and precise (bias and coefficient of variation<18%) over this calibration range.

Administration, Oral↗
PubMed2000

Recent developments in polymer-based sorbents for solid-phase extraction.

A review with 136 references on the principles and recent developments in the solid-phase extraction based on polymer sorbents is presented. New polymer-based materials, chromatographic modes, experimental configurations are described and their advantages for a rapid sample preparation of certain classes of compounds with different functional groups are discussed and compared to silica-based sorbents.

Chromatography, Liquid↗
PubMed2000

Sensitive determination of dissolved sulfide in estuarine water by solid-phase extraction and high-performance liquid chromatography of methylene blue.

A sensitive method involving solid-phase extraction and HPLC analysis of methylene blue has been developed to measure nanomolar levels of dissolved sulfide in oxic surface waters. The procedure included 1) a preconcentration step, in which methylene blue generated from sulfide reaction with n,n-dimethyl-p-phenylenediamine in acidic conditions in the presence of ferric ion was absorbed onto Waters tC18 cartridge; and 2) a determination step, in which methylene blue was separated by HPLC in a gradient elution to minimize natural organic matter interference and detected by absorbance. The concentrations of the dissolved sulfide, quantified by standard addition, were about 2.1-4.7 nM in oxic surface waters from Galveston Bay, Texas.

Chromatography, High Pressure Liquid↗
PubMed2000

Application of solid-phase extraction to the analysis of the isomers generated in biodesulfurization against methylated dibenzothiophenes.

A solid-phase extraction (SPE) technique was applied to analyze and characterize the biodesulfurization reactions against asymmetrically methylated dibenzothiophenes (mDBTs) such as 1-, 2-, 3- and 4-methyldibenzothiophenes present in fossil fuels. Recently, we found that these mDBTs are efficiently degraded by the bacterial strain, Rhodococcus erythropolis KA2-5-1. Separation and concentration of the microbial desulfurization products from each of the mDBTs could be carried out with high efficiency and reproducibility by the SPE procedure. These desulfurization products were identified using the SPE technique combined with GC, GC-atomic emission detection, GC-MS and 1H nuclear magnetic resonance spectroscopy. The analytical data obtained suggested that the desulfurization reactions against mDBTs by this bacterial strain may occur through specific carbon-sulfur bond-targeted cleavages that can be affected by the positions of methyl groups.

Chromatography, Gas↗
PubMed1999

Novel high-performance liquid chromatographic and solid-phase extraction methods for quantitating methadone and its metabolite in spiked human urine.

A novel solid-phase extraction (SPE) method and HPLC method were developed for the determination of methadone and its metabolite from spiked human urine. For sample cleanup, a spiked urine sample was pretreated with phosphoric acid followed by a well-thought-out SPE method using a 10-mg Oasis HLB 96-well extraction plate. In this SPE method, the concentration of methanol as well as the pH are optimized to preferentially isolate the analytes of interest from the sample matrix. Low elution volumes (200 microl) are achieved; this eliminates evaporation and reconstitution of the sample solution. Recoveries from human urine matrix were greater than 91% with RSD values less than 4.5%. For the HPLC analysis, the separation was obtained using a SymmetryShield RP18 column with a mobile phase of 0.1% TFA-methanol (60:40, v/v). Good peak shapes were obtained without the need of addition of any competing reagent to the mobile phase. Additionally, significant signal-to-noise enrichment was achieved by diluting the final SPE eluates four-fold with water.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Pitfalls and solutions in the development of a fully automated solid-phase extraction method for drug screening purposes in plasma and whole blood.

A fully automated solid-phase extraction (SPE) method for drug screening is described. The extraction of 19 toxicologically relevant drugs from pretreated plasma and pretreated whole blood was accomplished automatically by a Gilson ASPEC system equipped with disposable 2.8-mL Bond Elut Certify columns. The automated extraction procedure includes 11 fundamental steps: column preconditioning; sample application; column washing; pH adjustment; elution of drugs by two eluents, which were collected into two separated tubes; addition of the chromatographic standard solution; and several SPE column rack movement steps. After evaporation, the drugs were quantitated by gas chromatography. Water was chosen as the transfer liquid in the ASPEC system because it was cheap and, more importantly, because it caused no protein precipitation problem. The effects of the sample and eluent flow rates were investigated, and it was found that low flow rates were necessary to recover the drugs maximally. In the study, the optimal flow rates of sample application, acetone-chloroform elution, and ammoniated ethyl acetate elution were 1.5, 0.72, and 0.33 mL/min, respectively. The absolute recoveries of 19 drugs from whole blood exceeded 82%, with relative standard deviations less than 5% at 2 micrograms/mL.

Blood Chemical Analysis↗
PubMedDate not supplied

Gas chromatographic quantitation of dextropropoxyphene and norpropoxyphene in urine after solid-phase extraction.

A gas chromatographic technique with flame ionization detection, which is based on a solid-phase extraction (SPE) procedure using mixed-mode SPE columns, for the simultaneous quantitation of dextropropoxyphene and norpropoxyphene in urine is presented. Urine is treated with sodium hydroxide in order to rearrange, by base catalysis, norpropoxyphene to norpropoxyphene amide, which is then extracted with these columns and chromatographed. The method is specific, linear over the range 0-2000 ng/mL, sensitive, and reproducible. The extracts are cleaner than those obtained with traditional liquid-liquid extraction procedure, which is an important feature in view of further mass spectrometric confirmation of narcotics and other drugs.

Analgesics, Opioid↗
PubMedDate not supplied

Sample preparation for determination of macrocyclic lactone mycotoxins in fish tissue, based on on-line matrix solid-phase dispersion and solid-phase extraction cleanup followed by liquid chromatography/tandem mass spectrometry.

A new method based on matrix solid-phase dispersion (MSPD) on-line with a solid-phase extraction (SPE) cleanup process followed by liquid chromatography with tandem mass spectrometry (LC/MS/MS) is presented for the determination of 3 macrocyclic lactone mycotoxins in fish tissues: zearalenone, alpha-zearalenol, and beta-zearalenol. The sample was prepared in a device that used a reversed-phase material (C18) or a normal-phase material (neutral alumina) as a matrix dispersing agent, and a graphitized carbon black cartridge was used for sequential cleanup by SPE. LC/MS/MS was used for selective determination. Isocratic elution with acetonitrile-methanol-water was used for LC separation; for MS/MS, 2 types of interfaces (a pneumatically assisted electrospray ionization interface or an atmospheric pressure chemical ionization interface) were evaluated and compared in terms of the intensity of the total ion current produced by each analyte. The use of highly selective MSPD on-line with SPE for sample preparation before analysis allowed the removal of interfering matrix compounds present in tissue extracts that would otherwise cause severe ionization suppression of zearalenone and its metabolites during the ionization process. Average recoveries at 100 ng/g were between 83 and 103% with C18 and > or = 67% with neutral alumina; the relative standard deviations were < 11% with C18 and < 18% with alumina. The limits of detection ranged from 0.1 to 1.0 ng/g. Sample preparation is simple to perform, no special technical equipment is required, and solvent volumes are minimal.

Animals↗