SAX Cartridge Research Articles

Spectrophotometric Determination of Polyoxyethylene Nonionic Surfactants in Ground Waters Using Triple-Stage Solid-Phase Extraction Followed by an Improved Ferric Thiocyanate Complexation Method

A practical spectrophotometric determination method for polyoxyethylene nonionic surfactants in ground waters was established, which is based on a ferric thiocyanate complexation colorimetric method preceded by a triple-stage solid-phase extraction technique using SCX, SAX, and C18 cartridges interconnected. Cationic and anionic surfactants interfere with the determination and were therefore effectively trapped and isolated by the SCX and SAX solid phases, respectively. Nonionic surfactants (NSs) were finally introduced and concentrated in the C18 cartridge. The analyte was quantitatively eluted from the C18 sorbent, and the residue was subjected to the colorimetric determination. The calibration line was linear (r2 = 0.9997) up to 200 µg L−1 of heptaoxyethylenedodecylether when analyzing sample sizes of 100 mL. Overall recoveries were 95–97% with an RSD of less than 3%. The method was applied to the analysis of river water, and 6.4 µg L−1 of NSs as heptaoxyethylenedodecylether was found by means of the standard addition method. The proposed method is very practical and features minimum consumption of chemicals.

Determination of quinolones and fluoroquinolones in hospital sewage water by off-line and on-line solid-phase extraction procedures coupled to HPLC-UV

In this work, the development of two solid-phase extraction procedures (off-line and on-line formats) for the identification and quantification of several (fluoro)quinolones in hospital sewage water by HPLC-UV is described. Both procedures are based on the use of C18 and anion exchange (SAX) sorbents for the preconcentration and clean-up steps, respectively, and all variables influencing both steps were optimised. In the off-line format, after its pH was adjusted to 2.5, sample was preconcentrated on a C18 cartridge and eluted with 4 mL of methanol/ammonia (94/6). The methanolic extract must be diluted up to 10 mL with water to allow quantitative retention of the analytes on the SAX cartridge. In the on-line format, the addition of 2.5% of NH4Cl to the sewage water sample (pH = 2.5) was necessary to increase the breakthrough volumes of the analytes in the C18 precolumn. Quantitative transfer of the (fluoro)quinolones from the C18 precolumn to the SAX precolumn was accomplished by pumping 2 mL of a mixture methanol/water (40/60, pH = 9.2) at 2 mL min(-1). Elution of the analytes from the SAX precolumn by means of the chromatographic mobile phase required the inclusion of an additional isocratic step at the beginning of the gradient program. Both off-line and on-line solid phase extraction procedures coupled to HPLC-UV were applied to the analysis of a sewage water sample collected in the sewer system at the output of the St Dimphna Hospital (Geel, Belgium). The fluoroquinolone ciprofloxacin was found in this sample and quantified at 5.8 +/- 0.4 microg L(-1) (off-line method) and 5.6 +/- 0.5 microg L(-1) (on-line method). The analysis of spiked samples containing the seven (fluoro)quinolones studied provided quantitative recoveries in all cases with low RSD values (from 6 to 12%), and all the analytes could be identified by means of their UV spectra with match factors varying from 950 to 985 depending on the (fluoro)quinolone.

High-Performance Liquid Chromatographic Determination of Naturally Occurring Folates during Tempe Preparation

A trienzyme treatment (protease, alpha-amylase, and human plasma conjugase), followed by purification using SPE with SAX cartridges and reversed-phase HPLC with UV-PDA detection, was performed for determination of the distribution of various folate forms and content at various stages of tempe preparation. The major folate form in soybean identified was 5-formyl tetrahydrofolate (5-CHO-H4folate), followed by 10-formyl tetrahydrofolate (10-CHO-PGA), and 5-methyl tetrahydrofolate (5-CH3-H4folate), whereas folic acid was not detected and tetrahydrofolic acid (H4folate) was not detectable. The most predominant form in tempe was also 5-CHO-H4folate, followed by 10-CHO-PGA, whereas the quantities of 5-CH3-H4folate and folic acid were negligible. Quantities and retention of folate significantly decreased during the first boiling, dehulling, soaking, and second boiling procedures, yielding folate retention of 32%. A remarkable increase in folate content was found after fermentation, 5.2-fold higher than that of the boiled soybean. This may be due to de novo formation of folate by Rhizopus oligosporus, the principal mold in tempe fermentation. HPLC results were approximately 38-55% lower than the values obtained from the microbiological assay using Lactobacillus casei.

Determination of free molecular phenolics and catechins in wine by solid phase extraction on polymeric cartridges and liquid chromatography with diode array detection☆

The use of HLB Oasis polymeric cartridges to extract phenolic acids and aldehydes from red wines has been assayed and compared with the combination of ODS and SAX cartridges. The recoveries on the polymeric cartridges resulted to be notably higher with good precisions. The best operation conditions (cartridge conditioning, sample volume, clean-up and elution) for these latter were selected by experiments carried out on a synthetic wine sample spiked with 14 compounds and on red wine samples. A matrix-matched calibration was advisable to reduce the influence of the matrix in the quantification of the analytes as it was verified from the application of standard addition calibrations on several wine samples. Determination of the analytes in the extracts was performed by reversed-phase HPLC using mobile-phase and flow gradients and detection at 250, 280 and 340 nm.

Determination of free molecular phenolics and catechins in wine by solid phase extraction on polymeric cartridges and liquid chromatography with diode array detection

The use of HLB Oasis polymeric cartridges to extract phenolic acids and aldehydes from red wines has been assayed and compared with the combination of ODS and SAX cartridges. The recoveries on the polymeric cartridges resulted to be notably higher with good precisions. The best operation conditions (cartridge conditioning, sample volume, clean-up and elution) for these latter were selected by experiments carried out on a synthetic wine sample spiked with 14 compounds and on red wine samples. A matrix-matched calibration was advisable to reduce the influence of the matrix in the quantification of the analytes as it was verified from the application of standard addition calibrations on several wine samples. Determination of the analytes in the extracts was performed by reversed-phase HPLC using mobile-phase and flow gradients and detection at 250, 280 and 340 nm.

Simultaneous determination of t,t-muconic, S-phenylmercapturic and S-benzylmercapturic acids in urine by a rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry method.

We describe a rapid and sensitive high-performance liquid chromatography/electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) method for simultaneous determination of the most relevant metabolites of benzene and toluene, t,t-muconic acid (t,t-MA), S-phenylmercapturic acid (S-PMA), and S-benzylmercapturic acid (S-BMA). Urine samples were purified before analysis by solid-phase microextraction (SPE) on SAX cartridges with 50 mg sorbent mass. The developed method fulfils all the standard requirements of precision and accuracy. Calibration curves were linear within the concentration range of the standards (0-80 microg/L(urine) for t,t-MA, and 0-25 microg/L(urine) for S-PMA and S-BMA), and had correlation coefficients > or =0.997. Limits of detection were 6.0 microg/L for t,t-MA, 0.3 microg/L for S-PMA, and 0.4 microg/L for S-BMA. The method was used to determine t,t-MA, S-PMA and S-BMA levels in urine of 31 gasoline-station workers, with personal monitoring data obtained from radial symmetry passive diffusive samplers. In the context of mean work-shift exposures of 75.9 microg/m(3) (range 9.4-220.2) for benzene and 331.9 microg/m(3) (78.2-932.1) for toluene, metabolite concentrations in end-of-shift urine samples ranged from 23.5-275.3 microg/g(creatinine) for t,t-MA, non-detectable to 0.9 microg/g(creatinine) for S-PMA, and 3.8-74.8 microg/g(creatinine) for S-BMA. No significant correlation was found between the environmental concentrations and urinary metabolites (p > 0.05 for all cases); the ratios of benzene metabolites could be influenced by exposure levels and co-exposure to xylenes and toluene. The high throughput of this procedure should facilitate exploration of the metabolic effects of benzene-related co-exposure to toluene and alkylbenzenes in large populations of subjects exposed to gasoline.

Optimization of the determination of organic acids and sugars in fruit juices by ion-exclusion liquid chromatography

An HPLC method for the determination of the main organic acids and sugars in fruit juices is proposed. Nine acids (including oxalic, citric, malic, quinic, galacturonic, ascorbic, succinic, and fumaric acid) and three sugars (sucrose, glucose and fructose) were separated by ion-exclusion chromatography using a resin-based Aminex HPX 87H column after a sample clean-up with Sax cartridges. In spite of the suitable chromatographic conditions, quantification of ascorbic and dehydroascorbic acids was affected by on-column degradation of the former into the latter. For all the other analytes the method showed a good precision and linearity and, as an application, eighteen commercial juices from 4 different fruits were tested. Independently from the fruit, citric and malic acids were the main acids in juices, with amounts varying from 0.05 to 3.23 g/L and from 0.52 to 5.61 g/L, respectively. Compared to other fruits, pears demonstrated the highest content of succinic acid, possibly due to the coelution of relatively high quantities of shikimic acid. In some juices, small amounts of quinic, fumaric and galacturonic acids were also found. Finally, peach juices were demonstrated to be the richest in sugars, with apple juices being the poorest.

Method Development for the Determination of Seven Organic Acids in Wines by Reversed-Phase High Performance Liquid Chromatography

A simple high performance liquid chromatographic method is described for the determination of seven organic acids usually found in wines. The acids were eluted in the isocratic mode, in less than 12 min, on a reversed-phase ODS-2 (250 × 4 mm I.D.), 5 μm, column with 0.02 M potassium dihydrogen phosphate (pH 2.88), to which was added a small amount of methanol (2%) as organic modifier, and were detected by ultraviolet absorbance at 230 nm. Galacturonic, tartaric, malic (both enantiomers), lactic, acetic, citric and succinic acids were determined, using xanthine as a chromatographic internal standard. The method was applied to white and red wines of Greek origin, after sample clean-up with polyvinylpyrrolidone, followed by passage through SAX cartridges and yielded recoveries from 78.0 to 106.8%. The limits of detection ranged between 0.001–0.05 g.L−1 and the linear ranges between 0.003–2.0 g.L−1.

Simultaneous Determination of Azimsulfuron, Flazasulfuron and Halosulfuron-methyl in Grains, Seeds, Vegetables and Fruits by HPLC.

A method was developed for the simultaneous determination of 3 sulfonylurea herbicides, azimsulfuron, flazasulfuron and halosulfuron-methyl in agricultural products. The herbicides were extracted with acetone, re-extracted with ethyl acetate, and then transferred to 2% dipotassium hydrogenphosphate solution. The herbicides were extracted again into ethyl acetate and cleaned up using Sep-Pak® Plus Alumina N and Bond Elut® SAX cartridge columns. The 3 sulfonylurea herbicides were determined by HPLC. The fortified peaks were confirmed by LC/MS with electrospray ionization (ESI), and the peaks of azimsulfuron, flazasulfuron and halosulfuron-methyl were determined. The recoveries of the 3 sulfonylurea herbicides from brown rice, corn, cotton seed, ginkgonut, chestnut, almond, walnut, cucumber, pumpkin, orange, grapefruit, mandarin, lemon and grape ranged from 77.0 to 112.3% following fortification at 0.05-0.5 μg/g. The detection limits were 0.01 μg/g for azimsulfuron and halosulfuron-methyl, and 0.02 μg/ml for flazasulfuron(S/N > 3).

Determination of Fumonisins B1 and B2 Produced by Isolates of Gibberella fujikuroi Complex in Corn and Rice

Fumonisins B1 (FB 1) and B2 (FB2) are the major mycotoxins produced mainly by some strains of Gibberella fujikuroi complex, fungi that occur worldwide on cereals. Contamination of food and feed with these fungi has been associated with a number of diseases in animals and humans. In this work, some steps in the analysis of FB 1 and FB 2 by HPLC to reduce analysis time, costs and impurities in the extracts are evaluated. Fumonisins were extracted with acetonitrile/water (1:1), and the extract was cleaned up by solid-phase extraction through C 18 cartridges. These cartridges have the advantage over SAX cartridges of being less time-consuming and producing cleaner extracts. The fumonisins were eluted from the cartridge with methanol/water (7:3) and derivatized with ophthaldialdehyde and 2-mercaptoethanol to yield highly fluorescent derivatives. Reversed-phase HPLC with fluorescence detection is used for the final separation and determination. Under these conditions, the analytical method proved to be linear for mycotoxin amounts in the range from 10–4000 ng. The detection limits in corn and rice samples (at a signal-to-noise ratio of 3:1) were 5 ng/g for both fumonisins.

AN IMPROVED HPLC METHOD FOR THE ANALYSIS OF ORGANIC ACIDS, CARBOHYDRATES, AND ALCOHOLS IN GRAPE MUSTS AND WINES

An improved high performance liquid chromatography (HPLC) method for the analysis of the main organic compounds in musts and wines is presented. A column packed with hydrogen sulfonated divinyl benzene-styrene copolymer and two detectors connected in series were used (UV at 210 nm and RI, respectively). The addition of acetonitrile (6%) to the mobile phase (0.045N H2SO4) allowed the simultaneous separation and quantification of several organic acids, glucose, fructose, glycerol, and ethanol. Direct injection and sample clean-up with a SAX cartridge was tested and compared. The SAX fractionation gave satisfactory results, however the direct injection of diluted wine (1:20) provided the best precision (CV ≤ 2.1%) and accuracy of analysis. Statistical analysis (paired t-test) disclosed significant differences only for glucose, fructose, α-ketoglutaric, and pyruvic acid. The role of column temperature for the analysis of vitamin C (ascorbic acid) was also investigated. Vitamin C underwent thermal degradation during analysis with column temperature ≥ 30°C.

Simultaneous analysis of anthranilic acid derivatives in pharmaceuticals and human urine by high-performance liquid chromatography with isocratic elution

A high-performance liquid chromatographic (HPLC) method for simultaneous determination of mefenamic acid (MFA), flufenamic acid (FFA) and tolfenamic acid (TFA) is presented for application to pharmaceuticals and human urine. Isocratic reversed-phase HPLC was employed for quantitative analysis using tetra-pentylammonium bromide (TPAB) as an ion-pair reagent. Urine samples were purified by solid-phase extraction using a silica-based strong anion-exchanger, Bond-Elut SAX cartridge. The HPLC assay was carried out using a Wakosil ODS 5C 18 column (5 μm, 150×4.6 mm I.D.). The mobile phase consisted of 1.9 g of TPAB dissolved in 1 l of a mixture of acetic acid–sodium acetate buffer solution, pH 5.0, and acetonitrile (11:9, v/v). The calibration curves of MFA, FFA and TFA showed good linearity in the concentration range of 33–167 μg/ml with a wavelength of 280 nm for pharmaceuticals, and in the low concentration range (1.7–30.1 μg/ml) with a wavelength of 230 nm for biological fluids. The correlation coefficients were better than 0.9999 in all cases. The lower limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 2 ng for MFA, 3.5 ng for FFA and 2.5 ng for TFA. The procedure described here is rapid, simple, selective and is suitable for routine analysis of pharmaceuticals and pharmacokinetic studies in human urine samples.

Mold Occurrence and Aflatoxin B1 and Fumonisin B1 Determination in Corn Samples in Venezuela

Fumonisins are mycotoxins produced mainly by Fusarium moniliforme and Fusarium proliferatum, which have been associated with several animal and human diseases. Aflatoxins are hepatotoxic, mutagenic, and teratogenic metabolites produced by Aspergillus flavus and Aspergillus parasiticus. Both have been reported at high levels in corn. This study was pursued to determine mold, aflatoxin B(1) (AFTB(1)), and fumonisin B(1) (FB(1)) levels in white and yellow corn. Mold levels were determined using potato dextrose agar and identification of the main genus of molds present in corn, AFTB(1) levels by immunoaffinity chromatography, and FB(1) levels by a Bond-Elut SAX cartridge and HPLC. AFTB(1) an

Determination of sulfur dioxide and ascorbic acid in beverages using a dual channel flow injection electrochemical detection system

A new flow injection method is described for the simultaneous determination of ascorbic acid (AA) and sulfur dioxide in red and white wines and various fruit juices. The flow injection manifold consists of a dual channel amperometric detection system, where AA is detected at a glassy carbon electrode set at +0.42 V (versus Ag/AgCl) and sulfur dioxide is detected at a platinum electrode at +0.90 V (versus Ag/AgCl) after separation by a gas diffusion unit. In the application of this method to the analysis of both analytes in wines and fruit juices, the results for white wines, fruit juices and juice concentrates agree well with data obtained by ion-exclusion chromatography. However, in the case of red wines and a sweet white wine, it is necessary to extract the analytes using solid phase extraction on a quaternary amine SAX cartridge before acceptable results are achieved by the new flow injection method. The linear dynamic range for AA is 3–50 mg/l with a detection limit of 1.5 mg/l and for sulfur dioxide the linear range is 0.25–15 mg/l with a detection limit of 0.05 mg/l. The sampling frequency for both analytes is 30/h.

99Tcm-tetrofosmin: evaluation of fractionated cold kits and two new methods of quality control.

The fractionation of Myoview into 1:5 was followed by storage at -80 degrees C for 3 months. The kits were reconstituted with 3.5 GBq 99Tcm-pertechnetate and the average radiochemical purity (RCP) was maintained at 96.5 +/- 1.6% (n = 24) for 24 h. There was no difference in biodistribution between the 1:5 fraction and the full kit, especially with respect to myocardial uptake. These observations show that it is possible to fractionate and store Myoview kits at -80 degrees C and produce a product that is stable over 3 months. This provides a cost-effective method for using 99Tcm-tetrofosmin. Two new methods of determining RCP were also examined and found to give results that were not significantly different from the recommended manufacturer's method. A mini paper chromatography (MPC) method using Whatman 17 paper and a solvent mixture of ethyl acetate: acetone (1:9) and an Amprep SAX cartridge method using absolute ethanol as the solvent were found to be more rapid and reliable methods of quality control for this product.

Determination of Alkylphenols and 2, 4-Dichlorophenol in Foods

An analytical method using GC/MS was developed for the determination of 11 alkylphenols and 2, 4-dichlorophenol (2, 4-DCP) residues in various foods. The phenolic compounds were extracted with 50% diethyl ether-hexane after the alkaline decomposition of food samples. The extracts were cleaned up on an acidic alumina column and a SAX cartridge. The phenolic compounds were derivatived with heptafluorobutyric anhydride and the derivatives or parent compounds were determined by GC/MS (SIM or SCAN). The method was applied to determine alkylphenols and 2, 4-DCP residues in 190 food samples purchased from markets. 4-Nonylphenol was found in some fish, meat and vegetables at the levels of 10-723ng/g, 9-180ng/g and 7-131ng/g, respectively. In addition, 2, 4-DCP was detected in some vegetables (2-17ng/g).

Cloud point preconcentration and liquid chromatographic determination of aromatic amines in dyestuffs

Aromatic amines at μg l −1 levels in water were determined with cloud point preconcentration followed by liquid chromatography (LC) with UV absorption detection. This method was applied to the determination of aromatic amines at 10 μg g −1 levels in commercial dyestuffs. The dyestuff was dissolved in water and precleaned with a SAX cartridge packed with an anion-exchange resin; the effluent was then analyzed using the proposed cloud point preconcentration, with subsequent determination by LC.

Ion chromatographic analysis of nutrients in seed exudate for microbial colonisation

Information on the composition, levels, availability and microbial utilisation of the nutrients present in root and seed exudates is invaluable in harnessing selected microbes as biocontrol agents. The complex matrix that is sugar beet seed exudate is examined utilising the chromatographic modes of ion-exclusion–partition and ion-exchange. Many of the carbohydrates, organic acids and inorganic anions present there are identified. Specifically, collected seed exudate samples are analysed on an Aminex HPX-87H cation-exchange chromatography column with a dilute sulphuric acid mobile phase and refractive index detection. Improved resolution for the organic acids present (succinate, oxalate, formate, acetate) is achieved by a pre-treatment extraction on SAX cartridges prior to this chromatographic analysis. The inorganic anions fluoride, chloride, nitrate, phosphate and sulphate are directly determined alongside oxalate by ion chromatography on a Dionex IonPac AS4A column with isocratic elution and suppressed conductivity detection. In addition, the sugars (galactose, glucose, mannose, lactose, raffinose, maltose) can be analysed by high-performance anion-exchange chromatography with pulsed amperometric detection.

Trace determination of hydroxyaromatic compounds in dyestuffs using cloud point preconcentration

Hydroxyaromatic compounds at ppb levels in water were determined with cloud point preconcentration followed by high-performance liquid chromatography (HPLC) with UV absorption detection. The extraction efficiencies and preconcentration factors of cloud point extraction were enhanced by the addition of neutral electrolytes to the micellar solutions. This method was applied to the determination of hydroxyaromatic compounds at ppm levels in commercial dyestuffs. The dyestuff was dissolved in water and pre-cleaned with a SAX cartridge packed with an anion-exchange resin; the effluent was then analyzed using the proposed cloud-point preconcentration, with subsequent determination by HPLC.

Determination of surfactants in surface water by solid-phase extraction, liquid chromatography and liquid chromatography-mass spectrometry

Determination of surfactants in surface waters is required owing to their toxicity to aquatic micro-organisms and potential oestrogenic effects. We have investigated methods for the determination of two types of surfactants by solid-phase extraction with C 18 and SAX cartridges. HPLC separation of anionic and non-ionic surfactants on a C 1 (TMS) column has been achieved and detection via both fluorescence and liquid chromatography-mass spectrometry (atmospheric pressure chemical ionisation interface) is reported. Recoveries are approximately 100% using the method developed with detection limits of 50 ng on column for detection by fluorescence. Alkylphenol ethoxylates have been detected in samples taken from the River Rother in South Yorkshire, UK, at levels of 5.6 μg1 −1 using the described methodology.