Empore Extraction Research Articles

SPE-HPLC/DAD determination of trimethoprim, oxytetracycline and enrofloxacin in water samples

In this paper high-performance liquid chromatography with diode array UV detection (HPLC/DAD) after SPE sample pretreatment for simultaneous analysis of pharmaceuticals from three different classes: enrofloxacin, oxytetracycline and trimethoprim, has been developed, optimised and validated. The chromatographic separation was developed on spiked wellspring water samples and checked on model wastewater samples of veterinary pharmaceuticals before and after RO/NF membrane treatment (feed and permeate streams) and on process wastewaters of industrial origin. Chromatographic separation was performed on Varian ProStar HPLC/DAD with C-18 column (Microsorb-MV 100 C18, 150 × 4.6 mm; 5 µm, Varian, USA). Detection and quantification was performed at 254 nm. The best separation was achieved with mobile phase 0.5% formic acid and 1% trifluoroacetic acid in 0.05 M ammonium acetate-methanol, 70 + 30, (v/v) after extraction procedure on polystyrenedivinylbenzene Varian Empore extraction disks. The extraction efficiency was checked by recovery experiments.

Dual Function Surface-Enhanced Raman Active Extractor for the Detection of Environmental Contaminants

Surface-enhanced Raman spectroscopy (SERS) has lagged behind other analytical techniques utilized in routine chemical analyses despite the information-rich spectra produced. This can be attributed in part to the difficulties in finding effective substrates that provide high sensitivity and highly reproducible SERS responses. Herein, we have developed a silver-coated polypropylene filter (AgPPF) as a highly sensitive and promising SERS substrate for the detection of environmentally significant chemicals, including selected pharmaceuticals, personal care products, and possible endocrine disruptors. The present approach involves preconcentration studies of selected environmental compounds with 3M's High Performance Extraction Disc Cartridges (HPEDCs) and characterization of the same HPEDC filters as a SERS substrate. The polypropylene microfiber prefilter that encloses the empore extraction medium is modified by physical vapor deposition with silver and used as the SERS substrate. The HPEDC itself is used to concentrate analytes into a desired concentration range, achieving maximum sensitivity. Surface roughness and nanoscale structure of silver films on the microfiber were characterized by atomic force microscopy (AFM). The mass thickness of the silver and volume were optimized for the highest SERS signal using rhodamine 6G as a model compound. A novel component of our HPEDC studies involves the hyphenation of the concentration protocol and SERS. The hyphenation of sample concentration and SERS allows more sensitive surface-enhanced detection. Mitoxanthrone dihydrochloride, crystal violet dye, 4-aminobenzoic acid, and rhodamine 6G were employed to study the sensitive SERS detection and were observed as low as 5 x 10(-8) M to 1 x 10(-10) M without any preconcentration step. Additionally, SERS signatures of some flavonoids, targeted as possible Endocrine Disrupting Chemicals by the US Environmental Protection Agency, such as Apigenin and Daidzein, are reported along with their sensitive detection down to ng/mL for the first time with preconcentration.

Separation Techniques for Quantification of Radionuclides in Environmental Samples

The reliable and quantitative measurement of radionuclides is important in order to determine environmental quality and radiation safety, and to monitor regulatory compliance. We examined soil samples from Podunajske Biskupice, near the city of Bratislava in the Slovak Republic, for the presence of several natural (U, Th, K) and anthropogenic (Cs, Sr, Pu, Pu, Am) radionuclides. The area is adjacent to a refinery and hazardous waste processing center, as well as the municipal incinerator plant, and so might possess an unusually high level of ecotoxic metals. We found that the levels of both naturally occurring and anthropogenic radionuclides fell within the expected ranges, indicating that these facilities pose no radiological threat to the local environment. During the course of our analysis, we modified existing techniques in order to allow us to handle the unusually large and complex samples that were needed to determine the levels of Pu, Pu, and Am activity. We also rated three commercial techniques for the separation of 90Sr from aqueous solutions and found that two of them, AnaLig Sr-01 and Empore Extraction Disks, were suitable for the quantitative and reliable separation of Sr, while the third, Sr-Spec Resin, was less so. The main criterion in evaluating these methods was the chemical recovery of Sr, which was less than we had expected. We also considered speed of separation and additional steps needed to prepare the sample for separation.

Solid-phase extraction and TLC quantification of enrofloxacin, oxytetracycline, and trimethoprim in wastewater

Quantitative determination of the antibiotics enrofloxacin, oxytetracycline, and trimethoprim in aquatic samples is reported. The method involves solid-phase extraction (SPE) and preconcentration of the antibiotics, separation by thin-layer chromatography (TLC) and quantification by video densitometry. TLC separation was performed on HPTLC CN F 254 s plates with H 2 C 2 O 4 -methanol as mobile phase. Spots were detected and quantified at λ = 254 nm by videodensitometry. Limits of detection ( LOD ) and limits of quantification ( LOQ ) for TLC determination were calculated. The method was evaluated for spiked water samples. Antibiotics were extracted by solid-phase extraction (SPE) on a polystyrene-divinyl-benzene (SDB) Empore extraction disk. The extraction efficiency was checked by recovery experiments.

Determination of Commonly Used Herbicides in Surface Water Using Solid-Phase Extraction and Dual-Column HPLC-DAD

The present study describes the application of different solid-phase extraction techniques for the extraction, separation, and quantitative determination of 10 commonly used herbicides with different chemical structures (chlorsulfuron, diuron, bentazone, linuron, chlorpropham, fenoxoprop-ethyl, MCPA, diclofop-methyl, fluazifop-butyl, trifluraline) in water. Octadecyl (C18) Empore extraction disks, octadecyl (C18), and stryene divinylbenzene (SDB) Bond Elut Env cartridges were compared for solid-phase extraction efficiency. Herbicides were separated and quantified by reversed-phase high performance liquid chromatography with diode-array detection (HPLC-DAD) with simultaneous separation on two columns of differing polarity (C18 and CN) to confirm identification. Analytical separation was performed simultaneously on C18 and CN columns. Reanalysis of the sample extracts on a (cyano) CN column were used to confirm the identity of these compounds. Method optimization and validation parameters were presented in this work. Recoveries varied from 76.0% to 99.0% for C18 disks, from 75.1% to 100.0% for C18 cartridges, and from 54.0% to 98.0% for SDB cartridges over concentrations at 0.025–0.4 μg L−1. The limits of detection were 0.012–0.035 μg L−1.

GC/MSによる室内環境中の防蟻剤の一斉分析

We have established a method for simultaneously analyzing termiticides (13 kinds) in indoor air based on collection by combination of quartz filter and C18 Empore extraction disks, and measurement using gas chromatography mass spectrometry (GC/MS). The lower limit of determination for each substance was 0.02 microg/m3 when 2 m3 of air was sampled. The recovery was 66-100%, and the relative standard deviation was 3.7-14.2%. In experiments using a model box with commercial termiticides, we verified that emissions of bis (2, 3, 3, 3-tetrachloropropyl) ether (S421) increased with a rise in temperature from 10 degrees C to 20 degrees C to 40 degrees C, whereas almost no etofenprox was released into the air regardless of temperature. In addition, decanal, nonanal and alkanes (C13 and C14), which are major components of termiticides, were detected in relatively high concentrations. In the present study, regardless of low vapor pressure of the termiticides, several compounds were detected with the model box experiment. The conclusion that can be drawn is that it is necessary to survey the indoor environmental pollution.

Determination of the Mutagen 3-Nitrobenzanthrone in Rainwater Collected in Kyoto, Japan

The mutagen 3-nitrobenzanthrone was determined in rainwater. Rainwater was collected at a residential area in Kyoto, Japan. Organic matter containing 3-nitrobenzanthrone in rainwater was extracted using a 3M (St. Paul, MN, U.S.A.) Empore Extraction Disk C18, and the extract was purified on a pyrenylethyl silylated silica gel column. The purified sample was then reduced using a platinum black column heated at 80°C. The reduced product of 3nitrobenzanthrone, i.e. 3-aminobenzanthrone, was analyzed by normal-phase HPLC with fluorescence detection. 3Nitrobenzanthrone in the rainwater was determined in the range of 0.07‐2.6 ng l ‐1 . The concentration was higher from May to July and lower from October to December. 1-Nitropyrene was also determined by reversed-phase HPLC with fluorescence detection after platinum black column reduction. 1-Nitropyrene was detected in the range of 0.0056‐0.19 ng l ‐1 , and this concentration range was lower than that of 3-nitrobenzanthrone.

Novel field sampling procedure for the determination of methiocarb residues in surface waters from rice fields.

Methiocarb was extracted from surface water samples collected at experimental rice field sites in Louisiana and Texas. The sampling system consisted of a single-stage 90-mm Empore extraction disk unit equipped with a battery-powered vacuum pump. After extraction, the C-18 extraction disks were stored in an inert atmosphere at -10 degrees C and shipped overnight to the laboratory. The disks were extracted with methanol and the extracts analyzed by reversed-phase high-performance liquid chromatography with a methanol/water mobile phase. Methiocarb was detected by ultraviolet absorption at 223 nm and quantified with the use of calibration standards. Recoveries from control surface water samples fortified at 5.0, 10, 50, and 100 ng/mL methiocarb averaged 92 +/- 7%. A method limit of detection for methiocarb in rice field surface water was estimated to be 0.23 ng/mL at 223 nm.

A simple synthesis of [ 11C]carfentanil using an extraction disk instead of HPLC

[ 11C]Carfentanil was prepared without the need for purification by HPLC. The tetrabutylammonium salt of the precursor carboxylate was reacted with [ 11C]methyl triflate in DMSO. The resulting [ 11C]carfentanil was trapped on an Empore extraction disk and washed to remove precursor and most radioactive contaminants. The product was eluted by a small volume of ethanol, mixed with water and passed through a small column containing fibrous anion exchanger to remove remaining radioactive contaminants.

Investigation into the effects of temperature and stirring rate on the solid-phase extraction of diuron from water using a C 18 extraction disk

A novel experimental method for determining the equilibrium constant, K eq, and the uptake rate constant, k up, for the solid-phase extraction (SPE) of diuron from water using a C 18 Empore extraction disk is reported. Log K eq and log k up are determined at 7.0, 11.0, 18.0 and 23.0°C and for stirring rates of 100, 200 and 400 rpm. From a Van ‘t Hoff plot of log K eq versus T −1 the enthalpy of sorption, Δ H 0, is shown to be negative which indicates that the thermodynamic process of uptake is exothermic. The rate of stirring has no effect on log K eq over the temperature range 7.0–23.0°C. The enthalpy of activation, Δ H 0, calculated from Arrhenius plots of log k up versus T −1 at 100, 200 and 400 rpm show that the kinetic process of uptake is endothermic. At 100 rpm the rate of uptake is limited by the aqueous diffusion of diuron. At 200 rpm or greater the aqueous diffusion layer around the disk is sufficiently small to prevent diffusion from being a limiting factor. The method described in this paper is limited to the analysis of analytes that contain a significant UV chromophore and are relatively soluble in water, but it can also be used to investigate pH and salinity effects on the SPE of diuron from water.

Determination of L-756 423, a novel HIV protease inhibitor, in human plasma and urine using high-performance liquid chromatography with fluorescence detection

A method for the determination of L-756 423, a novel HIV protease inhibitor, in human plasma and urine is described. Plasma and urine samples were extracted using 3M Empore extraction disk cartridges in the C 18 and MPC (mixed-phase cation-exchange) formats, respectively. The extract was analyzed using HPLC with fluorescence detection (ex 248 nm, em 300 nm), and included a column switching procedure to reduce run-time. The assay was linear in the concentration range 5 to 1000 ng/ml when 1-ml aliquots of plasma and urine were extracted. Recoveries of L-756 423 were greater than 84% over the calibration curve range using the described sample preparation procedures. Intra-day precision and accuracy for this assay was less than 9% RSD and within 7%, respectively. Inter-day variabilities for the plasma ( n=17) and urine ( n=10) were less than 5% and 3% for low (15 ng/ml) and high (750 ng/ml) quality control samples. Bovine serum albumin (0.5%) was used as an additive to urine to prevent precipitation of L-756 423 during the storage of clinical samples. The assay was used in support of human clinical trials.

Improved Solid Phase Extraction Procedure for Assay of Cephalosporins in Human Urine Samples

Solid phase extraction technique has been evaluated for the treatment of urine samples in the analysis of cephalosporins before injection into an HP-Hypersil ODS-C18 column. Cephalexin, cefotaxime, cefazolin, cefuroxime, and cefoxitin were tested with seven different reversed-phase extraction column cartridges and the obtained urine extracts were not clean. However, 3M Empore extraction disk cartridges packed with octadecyl (C18) bonded silica provided clean extracts with a single extraction. The recoveriés of the five cephalosporins ranged from 56 to 60 % in the 1.25–500 g/mL concentration range. The assay was accurate, precise, and adequate for testing the drug content in urine samples. The detection limit found for the five drugs was 0.25 g/mL after an injection of 10 L. The reliability of this study was tested by analyzing a urine sample containing cefuroxime after a minimum single dose administration (250 mg).

Large volume preconcentration of dissolved hydrocarbons and polychlorinated biphenyls from seawater. Intercomparison between C 18 disks and XAD-2 column

The extraction efficiency of XAD-2 and 90 mm C 18 Empore disk for trace level determination (ng/L) of organic pollutants (i.e. hydrocarbons, chlorinated compounds) has been evaluated. Whereas C 18 Empore extraction disk exhibited higher extraction efficiency for aliphatic hydrocarbons from spiked Milli Q water and seawater, Amberlite XAD-2 column was more efficient for the extraction of individual PCB congeners and most of parent PAHs from spiked Milli Q water. However, in case of seawater analysis, the C 18 disk exhibited a higher extraction efficiency for the 3–4 aromatic ring PAHs. Only labile PAHs (i.e. benzo[ a]pyrene) and other analytes associated with fine particles were better recovered in XAD-2. Breakthrough volumes for the C 18 ( φ=90 mm) disks were compound dependent but they were at least 5–10 times lower than typical volumes for XAD-2. However, the C 18 disk application enables a solvent usage reduction leading to procedural blank improvement compared to XAD-2 columns.

Development of a Fast and Simple Method for Determination of β-Agonists in Urine by Extraction on Empore Membranes and Detection by a Test Strip Immunoassay

A rapid screening method for β-agonists in cattle urine was developed that offers speed and protocol simplicity and that could be performed on the spot. The method consists of an extraction on Empore membranes with strong cation exchange properties and a test strip immunoassay. The Empore extraction provides a fast and simple cleanup of the urines and a concentration step with recoveries ranging from 50-80% for the β-agonists of the aniline type and around 10% for salbutamol and terbutaline. A test strip immunoassay is performed on the diluted extract. With the use of an antiperoxidase antibody, an internal negative control was included, to which all color reductions are compared. Although a portable colorimeter increased the sensitivity of the test, a visual interpretation was sufficient to give a correct yes/no answer. The whole test takes about 30 min and has a visual detection limit for clenbuterol of 1 ng/mL of urine. The test also shows good sensitivity for salbutamol, despite the low recovery with the Empore extraction.

Analytical methods for the determination of organochlorine compounds: Application to environmental samples in the Slovak Republic

The paper deals with the isolation of chlorinated phenols, benzenes and insecticides from water, soil and vegetable samples. A review of the current procedures is presented. Solid-phase extraction on Empore extraction discs was experimentally evaluated for isolation of the compounds from surface and ground waters. For the isolation of chlorophenols from soil and vegetable samples, a method of simultaneous steam distillation/extraction was elaborated which proved to be also applicable for waste waters and sludges. Chlorinated insecticides and benzenes were extracted from soil and vegetable samples with the Soxhlet procedure. Final determinations were carried out by GC–electron-capture detection. The recoveries of the methods were well over 70%, with relative standard deviations below 14%. Samples of surface and ground waters, soil and vegetables, mostly from the vicinity of chemical and municipal waste dumping sites, were analysed. The highest contamination levels were found for chlorinated phenols in surface water from the vicinity of a former chemical waste dumping place where the concentrations of 2,6-dichlorophenol and pentachlorophenol were 4.3 and 3.9 μg l −1, respectively.

Efficient method for the quantitation of urinary leukotriene E4: extraction using an Empore C18 disk cartridge.

We describe here an efficient procedure for the precise quantitation of leukotriene E4 (LTE4) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [3H]LTE4 to 2 ml of urine, an Empore C18 cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE4 in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE4 was extracted from the effluent using an Empore C18 cartridge. The concentration of LTE4 was subsequently quantified by enzyme immunoassay. LTE4 can be recovered from urine with sufficient efficiency (69.9+/-4.7%, mean+/-S.D., n=101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE4, the recovery of LTE4 added to the urine specimen was less than 120%. The concentration of LTE4 in urine from normal healthy subjects was 48.0+/-15.3 pg/mg creatinine (n=15).

Use of metal chelate affinity chromatography and membrane-based ion-exchange as clean-up procedure for trace residue analysis of tetracyclines in animal tissues and egg.

A new and efficient procedure for the clean-up of tetracycline residues in animal tissues and egg prior to reversed-phase high-performance liquid chromatography is described. The principal steps involve homogenization of the tissues in sodium succinate buffer and methanol, followed by centrifugation and clean-up with metal chelate affinity chromatography (MCAC). After further concentration on an Empore extraction membrane with cation-exchange properties, the sample is analysed by HPLC with fluorescence detection. The method was tested on porcine kidney and muscle, bovine liver and whole chicken's egg. The recoveries were determined from spiked tissues for oxytetracycline, tetracycline, chlortetracycline and doxycycline and ranged from 40 to 70%, with repeatabilities below 10% R.S.D.. The analytical responses were linear in the range up to at least 1000 ng/g. The detection limits of the method were estimated at 0.42 ng/g of oxytetracycline, 0.49 ng/g of tetracycline, 0.66 ng/g of chlortetracycline and 1.38 ng/g of doxycycline in porcine muscle, using signal-to-noise ratios of 4:1. Similar detection limits were estimated for kidney, liver and egg. The measured limits of quantification were 2 ng/g for oxytetracycline, 3 ng/g for tetracycline, 4 ng/g for chlortetracycline and 5 ng/g for doxycycline in porcine kidney. The advantage of this method over existing methods is its increased limit of detection.

Gas-solid retention volumes of organic compounds on styrene-divinylbenzene and ethylvinylbenzene-divinylbenzene co-polymer sorbent beads

Reliable gas sampling with a sorbent requires a good knowledge of the gas-solid retention volumes of the analytes on the sorbent. Literature data on specific retention volumes at 20°C ( V g,293, l/g) are reviewed for a number of styrene-divinylbenzene (Sty-DVB) and ethylvinylbenzene-divinylbenzene (EVB-DVB)sorbents, namely XAD-3, Porapak P, Porapak Q, Chromosorb 101, and Chromosorb 102. New measurements are also made by gas-solid chromatography for a Sty-DVB polymer employed in one variety of Empore membrane extraction filters. For all of the data, the log V g, 293 values are highly correlated with both log p L 0 (log of the liquid vapor pressure at 20°C) and with T b(pure compound boiling point, K). The correlation equations allow the prediction of log V g,293 based on either log p L 0 or T b. Equations that can be used for a wide range of compounds and a range of Sty-DVB and EVB-DVB sorbents are: log V g,293 = 1 .16 log p L 0 + 3.51, and log V g,293 = 0.022 T b − 6.60. Separate equations are recommended for aliphatic acids and alcohols. For the Sty-DVB beads used in one variety of Empore extraction filters, the correlation equations are log V g,293 = 0.99 log p L 0 + 3.04, and log V g,293 = 0.0175 T b = t- 4.97. Most of the available data support absorption into the resin matrix as the dominant gas-solid partitioning mechanism for organic analytes to Sty-DVB sorbent materials.

Automated Sample Preparation for Monitoring Groundwater Pollution by Carbamate Insecticides and Their Transformation Products

We investigated automated on-line solid-phase extraction (SPE) followed by liquid chromatographic (LC) techniques for monitoring carbamates and their transformation products. Analytical determinations were performed by LC with UV or postcolumn fluorescence detection (U.S. Environmental Protection Agency Method 531.1 for carbamate insecticides) after preconcentration with on-line SPE using C18 Empore extraction disks. On-line SPE/LC/thermospray mass spectrometry with time-scheduled selected-ion monitoring was used as confirmatory method. The method was used to determine pesticide traces in well waters of a typical aquifer in the Almeria area (Andalucia, south of Spain) from March 1993 to February 1994. The major pollutants, found in highest amounts, were carbofuran, methiocarb, and methomyl, at levels of 0.32, 0.3, and 0.8 micrograms/L, respectively. According to results of seasonal variation studies, pollution by carbamate insecticides is sporadic and exceeds the limit of 0.5 micrograms/L for total pesticides allowed by the European Economic Community Drinking Water Directive only twice a year. 3-Hydroxycarbofuran and methiocarb sulfone also were detected, showing the importance of including the main toxic break-down products of carbamate insecticides in future monitoring programs.

Off-line and on-line solid-phase extraction followed by liquid chromatography for the determination of priority phenols in natural waters

Two analytical methods have been developed for the determination in water of 18 priority phenolics listed in US EPA method 604 and on EEC list 76/464. A solidphase extraction system using eight different sorbents packed in a precolumn was coupled on-line with a liquid chromatograph with UV detection. The ensuing method uses 50–100 mL of ground water; its performance was compared with that of an off-line method using Empore extraction disks and 1 L water samples. Phenol recoveries varied from <20 to 100% for concentrations in the range 0.1–10 μg/L at an acid pH. The presence of the phenols in water was confirmed by using thermospray LC-mass spectrometry in the negative ion mode. The stability of the phenols in water was studied at a 10 μg/l level in ground and estuarine water at acid pH (2.5–3) and at 4°C for 1 month. The system was validated by various interlaboratory exercises with samples containing 2,4,6-trichlorophenol and pentachlorophenol at concentrations from 0.1 to 0.5 μg/L.