Strong Anion-exchange Cartridge Research Articles

Profiling of organic acids by capillary gas chromatography–mass spectrometry after direct methylation in urine using trimethyloxonium tetrafluoroborate

Trimethyloxonium tetrafluoroborate (TMO) is applied as derivatising reagent to transform urinary organic acids into their methyl esters. The method is suggested as an alternative to the use of diazomethane which is carcinogenic and explosive. In contrast to other methods avoiding diazomethane, such as derivatizations with acetyl chloride–methanol and boron trifluoride–methanol, which require an organic reaction medium and therefore an extraction of the organic acids from the urine, TMO efficiently reacts with the acids in an aqueous solution and can therefore be directly applied to native urine. The use of TMO simplifies and improves the sample preparation in the profile analysis of urinary organic acids by capillary GC–MS and hereby increases the speed of analysis. The method gives reproducible results which are comparable with the data obtained using conventional solid-phase extraction with strong anion-exchange cartridges prior to derivatisation.

High-Performance Liquid Chromatographic Method for the Determination of Intracellular dTTP Pools

The size of intracellular 2′-deoxythymidine-5′-triphosphate (dTTP) pools is an important indicator of cytotoxicity in cells exposed to antiviral drugs and mutagens. We describe an ion paired reverse-phase high performance liquid chromatographic (HPLC) assay for the quantification of thymidine triphosphate in peripheral blood mononuclear cells (PBMC). Cell extracts are first purified by solid phase extraction using strong anion exchange (SAX) cartridges. The resulting fraction is analyzed by isocratic HPLC using a C18 column and a mobile phase consisting of triethylamine phosphate buffer with 2% acetonitrile. UV detection at 267 nm is used. Coefficients of variation for the assay are in the range of 6.0–9.8%. The overall recovery is 86.84%. LOQ for this assay is 48 ng/mL (100 nM), which is equivalent to 5 pmol/106 cells and give a signal to noise ratio of 4:1. The method described is used for the determination of dTTP pools in PHA-stimulated PBMC from healthy volunteers.

Determination of glycolic acid in cosmetic products by solid-phase extraction and reversed-phase ion-pair high-performance liquid chromatography

A procedure has been developed for the assay of glycolic acid in cosmetic products by reversed-phase high-performance liquid chromatography using an ion-pairing method. After dissolution in tetrahydrofuran–water (90:10, v/v), samples were purified by solid-phase extraction using silica-based strong anion-exchange cartridges and analysed directly on an Ultrasphere ODS column with UV detection at 210 nm and methanol–phosphate buffer (2:98, v/v), containing tetrabutylammonium iodide, as the mobile phase. Recovery of glycolic acid from different cosmetic matrices was between 92.4 and 96.2% and the precision of the method was better than 5.4% relative standard deviation. The procedure is rapid, simple, selective and it is suitable for routine analyses of commercial cosmetics.

Sensitive method for the detection of fumonisin B 1 in human urine

Fumonisins are a group of carcinogenic mycotoxins that occur worldwide. This paper reports a sensitive method for the detection and quantitation of fumonisin B 1 in human urine. Amberlite XAD-2 non-ionic polymeric adsorbent resin is used prior to strong anion-exchange (SAX) cartridge clean-up. As much as 100 ml of undiluted human urine can be loaded onto the column. Recoveries obtained using this method were 93.6, 95.1 and 94.4% when samples were spiked with 10, 50 and 500 ng/ml of fumonisin B 1, respectively. This method is highly reproducible (R.S.D.<5%) and gives good sample clean-up, which is suitable for HPLC analysis.

Improvements in the Analysis of Reduced Folate Monoglutamates and Folic Acid in Food by High-Performance Liquid Chromatography

A reversed-phase high-performance liquid chromatographic method with fluorescence and ultraviolet detection was used to evaluate the different steps in folate analysis to detect and quantify the most abundant folate forms naturally present in foods. Rapid heat extraction by microwave heating and an enzymatic deconjugation with hog kidney conjugase and chicken pancreas is presented. The extracts were purified with strong anion-exchange cartridges before injection. The combined use of ascorbic acid and mercaptoethanol in the extraction step noticeably improved the stability of tetrahydrofolate, making it also possible to analyze some of the most labile folate vitamers. Tetrahydrofolate was also shown to be easily degraded during the deconjugation step. The compounds 5-methyltetrahydrofolate and, to a lesser extent, 5-formyltetrahydrofolates were also found as important vitamers in foods. In addition, folic acid and 10-formylfolic acid could be determined with the described method. Keywords: Folates; folic acid; food; HPLC

Improved method for the determination of glyphosate in water

A method for the determination of glyphosate (Glyph) and its metabolite aminomethylphosphonic acid (AMPA) in environmental water was developed with the emphasis on the clean-up procedure. The organic compounds in the environmental water were extracted with dichloromethane and the sample was concentrated by rotary evaporation. The concentrated sample was then passed through a strong anion-exchange (SAX) cartridge with an additional 2 ml of resin in the hydroxide form packed above the SAX packing. Glyph and AMPA were eluted with citrate buffer at pH 5.00 and determined directly by high-performance liquid chromatography with a postcolumn reactor and fluorescence detector. The detection limit and average recovery for both components were <2 μg/l and >85%, respectively.

The Determination of Oxalate in Urine and Plasma by High Performance Liquid Chromatography

We describe a simple, sensitive assay for oxalate in urine or plasma. Acidified urine is pretreated by dilution with neutral phosphate buffer and passage through a C18 cartridge. Stabilized plasma is diluted with neutral acetate buffer and oxalate extracted using a strong anion exchange cartridge. Treated samples are applied to an ion-paired chromatographic system and oxalate detected electrochemically. Recovery of oxalate from augmented samples exceeded 97% from both urine and plasma. Within- and between-assay coefficients of variation assessed at three concentrations were, respectively, better than 4.1% and 8.4% for urine and 3.9% and 5.2% for plasma. The reference range for urinary oxalate excretion is 109-497 mumols/24 h. The range for plasma oxalate concentration is 0.6-2.8 mumols/L or 0.7-3.9 mumols/L after an overnight fast or without dietary restriction, respectively. Urine and plasma oxalate concentrations from this method, gave correlation coefficients (r) of 0.97 and 0.98, respectively, when compared with those from established oxalate oxidase based assays.

Solid-Phase Extraction of As(III) from Aqueous Samples Using On-Column Formation of As(III)-Trispyrrolidinedithiocarbamate

Abstract Two methods are presented for the selective preconcentration of As(III) by using complexation-type stationary phases. These phases are prepared: (1) by loading a C18-bonded silica with the cetyltrimethylammonium-pyrrolidinedithiocarbamate (CTA+-PDC−) ion-pair, or (2) by converting a strong anion-exchange (SAX) resin from the quaternary ammonium form into the pyrrolidinedithiocarbamate (PDC−) form. When As(III)-containing solutions are passed through such stationary phases, the immobilized PDC− yields the non-polar As(III)-trispyrrolidinedithiocarbamate (As(PDC)3) which is retained on the non-loaded second part of the C18 cartridge (method 1), or on an unloaded C18 cartridge coupled in series with the SAX cartridge (method 2). For both methods parameters influencing the preconcentration have been investigated by using the 74As(III) radiotracer; 74As(V) was applied to study the selectivity of both methods. A selective preconcentration of As(III) is possible. The retention mechanisms are discussed. ...

Solid-phase extraction of cytokinins from aqueous solutions with C18 cartridges and their use in a rapid purification procedure

Eleven cytokinins-including bases, ribosides, glucosides, and ribotides-were tested for their retention on C18 cartridges that were washed with 40 mL of water or a dilute acid at pH 3. Cytokinins were then eluted with methanol and analyzed by high performance liquid chromatography (HPLC). All pure cytokinin were well retained when the cartridge was washed with water, but Z and (diH)Z were less well retained at pH 3. The ribotides required 80% methanol for elution. Cotton leaf tissue (500 mg dry wt) was spiked with cytokinins, extracted with 80% methanol, and the extract bulk purified with hexane, insoluble polyvinylpyrrolidone, and minicolumns (strong anion exchange, amino, and C18 cartridges). Ribotides, added to leaf tissue, could not be recovered as ribotides; it was necessary to hydrolyze and purify them as ribosides. The cytokinins were separated and analyzed by HPLC on strong cation exchange and C18 columns. Recoveries through the entire procedure averaged 70%.

Quantitative Determination of Fumonisins B1and B2by High-Performance Liquid Chromatography with Fluorescence Detection

Abstract A high-performance liquid chromatographic method has been developed for the quantitative determination of the recently described mycotoxins, fumonisins B1 (FB1) and B2 (FB2) utilizing pre-column derivatization with o-phthaldialdehyde, isocratic elution, and fluorescence detection. Prior to analysis, sample extracts were purified on strong anion exchange cartridges. The method has been applied to the analysis of naturally contaminated corn and mixed horse feed samples as well as fungal culture material, for the presence of the mycotoxins. Detection limits are approximately 50 ng g−1 for FB1 and 100 ng g−1 for FB2. The method proved to be highly reproducible and recoveries of the toxins from the purification steps were found to be 99.5% and 85.9% for FB1 and FB2, respectively.

Comparison of sample preparation methods for the high-performance liquid chromatographic analysis of cell culture extracts for triphosphate ribonucleosides and deoxyribonucleosides

We compared four different procedures for the purification and concentration of nucleoside triphosphates in cell extracts prior to HPLC analysis. Two methods involved precipitation, with either acetonitrile or calcium fluoride. The acetonitrile procedure yielded reasonable recovery and sufficient purity for the subsequent HPLC analysis. The calcium fluoride coprecipitation procedure gave both good recovery and purity; but the recovery was shown to be dependent on the concentration of the nucleoside triphosphates. The other two methods involved small Sep-Pak cartridges. The silica cartridge procedure yielded unfavorable recoveries in periodatetreated cell extracts, apparently due to poor solubility of nucleoside triphosphates in the requisite solvents. The strong anion exchange cartridge procedure yielded both good recovery and purity. This procedure was found to be fast, efficient, and reliable for purifying and concentrating nucleotides in cell extracts.