Use of an amino-silica column for the high-performance liquid chromatographic analysis of synthetic oligodeoxy-nucleotides.

The use of an amino-silica column in the chromatographic analysis of synthetic oligodeoxyribonucleotides and their derivatives from different stages of oligonucleotide synthesis has been investigated. By eluting with 0.10 M potassium phosphate solution of pH 3.30, the nucleotide composition of oligonucleotides can be established within 15 min. In a linear gradient of phosphate buffer (0.10-0.75 M) at neutral pH, the separation of oligonucleotides by length and in an acidic medium pH 3.30-4.30) by composition is possible; the oligonucleotides may be in the free form or modified by the various protecting groups used in synthetic oligonucleotide chemistry. The analysis of some reaction mixtures from different stages of oligonucleotide synthesis and of a number of synthetic oligodeoxyribonucleotides and their derivatives has been performed.     

A gradient HPLC test procedure for the determination of impurities and the synthetic precursors in 2-[4-(1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]-butyl)-phenyl]-2-methylpropionic acid

A gradient high-performance liquid chromatographic (HPLC) test procedure is developed and evaluated for its ability to establish the levels of impurities and remaining synthetic precursors in 2-[4-(1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]-butyl)-phenyl]-2-methylpropionic acid. A gradient program with a mobile phase of 0.02 M sodium phosphate buffer and 0.004 M sodium perchlorate in acetonitrile-water (approximately pH 2.5) is used with a Spherisorb C6 column. The acetonitrile composition is increased linearly from 40% to 65% over a 45-min period and held at 65% for 20 min. UV detection at 210 nm is used to quantitate all components. The procedure is validated for accuracy using spiked levels (0.1% to 1.5%, w/w) with two suspected impurities, the synthetic precursors. A multiday repeatability study using two different Spherisorb C6 columns and HPLC systems shows consistent impurity quantitation results with one production lot of the bulk compound.     

Enhanced mass detection of oligonucleotides using reverse-phase high-performance liquid chromatography/electrospray ionization ion-trap mass spectrometry

A new method providing enhanced sensitivity for the analysis of oligonucleotides using an on-line coupled system of reversed-phase high-performance liquid chromatography (RP-HPLC) and electrospray ionization ion-trap mass spectrometry (ESI-MS) has been developed. The presented method allows the use of the standard gradient elution of 0.1 M triethylammonium acetate (TEAA) buffer (adjusted to pH 7.0 with acetic acid) and acetonitrile that is typically used for the separation of oligonucleotides in RP-HPLC. An added feature of this method is the ability to combine and mix additional 0.1 M imidazole in acetonitrile after the separation column for improved ESI-MS performance. This is similar to the post-column reaction method in liquid chromatography (LC) and the liquid sheath flow method in LC/ESI-MS, both of which offer the advantage of not compromising the chromatographic separation conditions. The application of this new method is demonstrated to afford improved sensitivity for the analysis of oligonucleotides (20-50 mer) via on-line coupled HPLC/ESI-MS analysis and purification systems.     

HPLC of nucleotides. II. General methods and their development for analysis and preparative separation. An approach to selectivity control

In order to develop efficient separation methods for nucleotides according to their size and heterocyclic composition, the application of ion-exchange, reverse-phase, and normal-phase adsorption HPLC has been studied. The comparative investigation of retention power and selectivity of various packings (non-polar bonded-phase and amino silicas) in relation to nucleotide length and composition yields data which enable suitable packings to be selected and a method of preparing the new packing for a particular separation problem to be formulated. Thus a new anion exchanger with high selectivity and dynamic mass transfer has been prepared for fractionation of large oligonucleotides. The effect of the eluent pH and composition (organic modifier, salt) on retention, selectivity, and resolution in ion-exchange and reverse-phase HPLC has been studied. The optimum separation conditions comprise elution with oppositely directed gradients of the salt and the modifier, use of a precolumn packing that provides the best protection for the main column without loss of its efficiency, and the optimum gradient program for the desired retention of the component of interest. The relation between loading and sample concentration has been studied and the system for gradient elution improved. Our work shows that two-dimensional separation is the most reliable and informative method for preparation of homogeneous oligonucleotides. The hydrophobic-pair ion-exchange mechanism is proposed for ion-pair chromatography. Protected and partially deblocked oligonucleotides, chemically synthesized for genetic engineering studies, have been separated with high selectivity by adsorption (normal-phase) HPLC which is efficient for gradient elution with isohydric eluents. The analysis of a monomeric composition of nano-(pico-) molar amounts of oligonucleotides has been developed; the procedure involves microcolumn digestion of the oligonucleotides with immobilized enzymes followed by microcolumn separation of the nucleoside-mononucleotide mixture. Also, a new slurry method for packing stable HPLC columns with a tightly consolidated, nonshrinkable bed of particles has been developed.     

Assay of human erythrocyte pyrimidine and deoxypyrimidine 5'-nucleotidase by isocratic reversed-phase high-performance liquid chromatography

We report a rapid and reproducible assay for activity of human erythrocyte pyrimidine 5'-nucleotidase and deoxypyrimidine 5'-nucleotidase. The nucleotides CMP, UMP, dUMP, dCMP or dTMP are individually incubated 30 min at 37 degrees C with erythrocyte hemolysate and 4 mM magnesium chloride in Tris, pH 7.5. Data are provided for standardization of the reaction with each substrate. Individual nucleoside products are assayed in less than 10 min by reversed-phase high-performance liquid chromatography at 280 nm with 0-14% methanol in 0.01 M potassium dihydrogen phosphate. This is the first report of a high-performance liquid chromatographic assay system which allows quantitation of the activity of pyrimidine 5'-nucleotidase isozymes using five individual pyrimidine and deoxypyrimidine nucleotides as the substrates.     

Development of a perfusion ion-exchange chromatography method for the separation of soybean proteins and its application to cultivar characterization

A perfusion ion-exchange chromatography method has been designed, for the first time, for the separation of soybean proteins and its application to the characterization of soybean cultivars. For that purpose, the gradient, the mobile phase composition (buffer concentration, buffer pH, and elution salt), and the temperature were optimized. The method consisted of a two-step gradient (0% B for 2 min and from 0 to 50% B in 10 min) being mobile phase A a 2 0mM borate buffer (pH 9) and mobile phase B a 20 mM borate buffer (pH 9) containing 1M sodium chloride. The procedure used for the preparation of sample solutions was significantly simpler than that proposed by other authors and basically consisted of dissolving in water. This method enabled the separation of soybean proteins from a soybean protein isolate in 11 peaks in about 9 min. The method was used to separate soybean proteins in different commercial soybeans. In general, the 11 peaks yielded by the soybean protein isolate were also observed in the chromatograms of all soybeans. However, the area percentages of every peak in every soybean enabled the differentiation between soybeans. Moreover, the method was also used to separate soybean proteins in the proteic fractions obtained from every soybean. Multivariate methods were used for patterns recognition and the classification of samples.     

Rapid, high-sensitivity reversed-phase liquid chromatographic assay for 9-chloro-2-(2-furyl) [1,2,4]triazolo[1,5-c]quinazolin-5-imine and its oxo metabolite in plasma using fluorescence detection

A rapid, sensitive and specific assay for 9-chloro-2-(2-furyl) [1,2,4]triazolo[1,5-c]quinazolin-5-imine (I) and its oxo metabolite (II) in plasma was developed and validated employing reversed-phase high-performance liquid chromatography with fluorescence detection. Sample preparation was achieved by a simple ethyl acetate extraction from plasma buffered at pH 10 (0.1 M boric acid-0.1 M potassium chloride). Chromatographic analyses were performed isocratically on a C18 column, with a mobile phase consisting of methanol-0.2 M sodium acetate buffer, pH 5.0 (67:33, v/v). Chromatographic run time was less than 8 min. The assay was linear (r greater than 0.9998) over the concentration range 1.50-10,000 ng/ml for both I and II; for individual studies, curves covering a range of two orders of magnitude were generally employed. Limits of detection for I and II were 0.5 and 1.0 ng/ml, respectively. A preliminary investigation of the plasma concentrations of I and II in the rat following a single 30 mg/kg oral dose demonstrated the applicability of the method for pharmacokinetic studies.     

Liquid chromatographic determination of multiple sulfonamides, nitrofurans, and chloramphenicol residues in pasteurized milk

A rapid and selective liquid chromatographic method was developed to detect 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in pasteurized milk. The 10 drugs were extracted with chloroform-acetone and the organic phase was evaporated; the residues were dissolved in an aqueous sodium acetate buffer solution 0.02M (pH = 4.8), and the fat was removed by washing with hexane. The aqueous layer was collected, filtered, and injected. The 6 sulfonamides and chloramphenicol were detected at 275 nm ultraviolet (UV) using a gradient system starting with sodium acetate buffer solution-acetonitrile (95 + 5) and finishing with sodium acetate buffer solution-acetonitrile (80 + 20). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution-acetonitrile (80 + 20). For 50 ppb fortified milk, the average recoveries were (sulfathiazole) 65.52%; (sulfamerazine) 75.36%; (sulfamethazine) 93.94%; (sulfachlorpyridazine) 75.94%; (sulfamethoxazole) 85.18%; (sulfamonomethoxine) 83.45%; (chloramphenicol) 104.17%; (nitrofurazone) 91.81%; (furazolidone) 100.76%; and (furaltadone) 72.38%. Method detection limits ranged from 4 ppb (nitrofurazone) to 16 ppb (sulfamethazine). Some matrix interferences (3-7 ppb) were observed only with sulfonamides.     

High-performance liquid chromatographic assay for pteroylpolyglutamate hydrolase

A highly sensitive assay for pteroylpolyglutamate hydrolase is described employing high-performance liquid chromatography (HPLC) with ultraviolet detection at 280 nm. The method is based on the separation of pteroylpolyglutamates containing various glutamyl residues on a C18 muBondapak reversed-phase column. Individual pteroylpolyglutamates are eluted by a gradient of 2.5-8.5% acetonitrile in 0.1 M potassium phosphate buffer (pH 6.0) within 20 min. The polyglutamates with higher glutamyl residues were less well retained in the reversed-phase column. The relationship between the peak area and the amount of pteroylpolyglutamate was observed to be linear over the range 10 pmol to 2.5 nmol. Human serum pteroylpolyglutamate hydrolase was studied using pteroylpentaglutamate as substrate in 0.1 M sodium acetate buffer (pH 4.5). The enzyme appeared to function as an exopeptidase based on the detection of intermediates, pteroyltetra-, tri-, and -diglutamate, and the product, pteroylmonoglutamate. Using the HPLC assay, extracts of Plasmodium falciparum were found not to contain detectable enzyme activity.     

Optimizing processing parameters for signal enhancement of oligonucleotide and protein arrays on ARChip Epoxy

Signal enhancement of oligonucleotide and protein arrays on ARChip Epoxy was achieved by optimizing chip processing parameters. The parameters investigated were fabrication, blocking and guide dot concentration, probe concentration and modification, print buffer, humidity during arraying, slide agitation, spot volume and spotter compatibility. The optimum oligonucleotide concentration was 20 microM, while the optimum protein concentration was 0.05 mg/ml. Amino-modified oligonucleotides were best able to be bound to the resin's epoxy groups at pH 8, whereas thiol-modified oligonucleotides displayed an optimum coupling value of pH 7. So as to avoid background (BG) contamination of probes around bright guide dots, the concentration of fluorescent guide dots was set to 1 muM. The most suitable print buffers for oligonucleotide arrays using both piezo- and contact-printing systems proved to be 3 x SSC/1.5 M betaine and commercial ArrayLink. When 0.01% monochlortriazinyl-beta-cyclodextrin sodium salt (MCT) was added, the hybridization signal doubled in strength as compared to plain buffer. The optimum print buffer for proteins was 0.1 N phosphate buffer, pH 8/10% glycerine. The optimum humidity for arraying oligonucleotides was 60% and for proteins 40%. Initially agitating slides for 15 min was found just as effective as agitating slides over the total hybridization period (2.5 h), and this resulted in a three times stronger signal.     

液相色谱-串联质谱法同时检测水产品中苦参碱和鱼藤酮残留

建立了液相色谱-串联质谱同时检测水产品中苦参碱与鱼藤酮残留的方法.试样以乙酸铵缓冲液乙腈提取,提取液中加入 NaCl盐析后,以正己烷除脂净化.采用 Agilent Zobax SB-C<,18>色谱柱,以乙酸铵缓冲液-乙腈为流动相,梯度洗脱分离后,采用电喷雾电离源串联质谱的正离子模式测定.分析物在0.001～0.05m...     

Rapid characterization of oligonucleotides by capillary liquid chromatography-nano electrospray quadrupole time-of-flight mass spectrometry

A fast quality control method is developed allowing the desalting and characterization of oligonucleotides by capillary liquid chromatography and on-line nano-electrospray ionization quadrupole time-of-flight mass spectrometry using column switching. The influence of addition of ammonium acetate, trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid, formic acid or acetic acid to the sample, addition of ammonium acetate to the trapping solvent and variation of the trapping time on the further reduction of cation adduction was studied. Final conditions were the addition of 0.1 M ammonium acetate to the sample, the use of a trapping solvent consisting of 0.4 M aqueous 1,1,1,3,3,3-hexafluoro-2-propanol (HFLP) adjusted to pH 7.0 with triethylamine plus 10 mM ammonium acetate during 8 min and the elution of the oligonucleotides with 0.4 M HFIP in 50% methanol. The potential of the optimized procedure is demonstrated for different synthetic oligonucleotides.     

Fractionation and separation of human salivary proteins by pH-gradient ion exchange and reversed phase chromatography coupled to mass spectrometry

In the present work, a 2-D capillary liquid chromatography method for fractionation and separation of human salivary proteins is demonstrated. Fractionation of proteins according to their pI values was performed in the 1-D employing a strong anion exchange (SAX) column subjected to a wide-range descending pH gradient. Polystyrene-divinylbenzene (PS-DVB) RP columns were used for focusing and subsequent separation of the proteins in the 2-D. The SAX column was presaturated with a high pH buffer (A) consisting of 10 mM amine buffering species, pH 9.0, and elution was performed with a low pH elution buffer (B) having the same buffer composition and concentration as buffer A, but pH 3.5. Isoelectric point fractions eluting from the 1-D column were trapped on PS-DVB trap columns prior to back-flushed elution onto the PS-DVB analytical column for separation of the proteins. The 1-D fraction eluting at pH 9.0-8.7 was chosen for further analysis. After separation on the RP analytical column, nine RP protein fractions were collected and tryptic digested for subsequent analyses by MALDI TOF MS and column switching capillary LC coupled to ESI TOF MS and ESI QTOF MS. Eight proteins and two peptides were identified in the pH 9.0-8.7 fraction using peptide mass fingerprinting and uninterpreted MS/MS data.     

An optode sensor for Cu2+ with high selectivity based on porphyrin derivative appended with bipyridine.

A porphyrin derivative (fluorophore) appended with bipyridine (ionophore) has been applied for preparation of a Cu2+-sensitive optical chemical sensor, which is based on fluorescence quenching of porphyrin derivative entrapped in a poly(vinyl chloride) membrane by the energy transfer process. The sensor exhibits a linear response toward Cu2+ in the concentration range 2.0 x 10(-8) - 1.0 x 10(-5) M, with a working pH range from 6.0 to 8.0 and a high selectivity. The detection limit is 5 x 10(-9) M. The response time for Cu2+ is less than 5 min with concentrations lower than 5 x 10(-6) M. The optode can be regenerated using 0.3 M EDTA (pH 9) and acetate buffer solution. The effect of the composition of the sensor membrane was studied, and the experimental conditions were optimized. The sensor has been used for direct determination of Cu2+ in water samples with satisfied results.     

Separation of Ribose-5-phosphate,Ribose-1-phosphate,Deoxyribose-1-phosphate by High Performance Liquid Chromatography and Spectrophotometric Determination Using 2-Cyanoacetamide

Abstract

A simple procedure for separation of ribose-5-phosphate, deoxyribose-1-phosphate and ribose-1-phosphate is based on high performance liquid chromatography using reversed phase 4 × 300 mm “μ Bondapak/NH₂” column. The column is equilibrated with 0.13 M borate buffer (pH 7.5) followed by gradient elution of ribose-5-phosphate, deoxyribose-1-phosphate and ribose-1-phosphate using water, 0.05 M borate buffer containing 0.1 M MgCl₂ (pH 9.6) and 0.05 M sodium acetate-acetic acid buffer containing 0.1 M MgCl₂ (pH 5.0) as eluants respectively. Eluates of borate complex “μ Bondapak/NH₂” column are brought to pH 9.6 by the addition of 1 N KOH and enzymatically hydrolysed with alkaline phosphatase (EC 3.1.3.1) to release the free pentoses. The free pentoses are mixed with a reagent solution prepared from aqueous solution of 2% cyanoacetamide and 0.6 M borate buffer (pH 9.6), and the mixture is boiled for 10 minutes and the absorbance of the product is measured at 276 nm using a spectrophotometer.     

High-performance liquid chromatography of sulphonamides extracted from bovine and porcine muscle by solid-phase dispersion.

A method has been developed for the analysis of sulphonamides in bovine and porcine muscle, based on solid-phase dispersion. Muscle tissue was blended with pre-washed C18 coated silica (55-105 microns), and the resulting homogeneous solid packed into a polypropylene syringe barrel. Fatty material was washed from the sample using hexane, and the sulphonamide analytes eluted with dichloromethane. The collected fraction was dried under nitrogen and reconstituted in 20% methanol in 0.01 M sodium acetate/acetic acid (pH 5) buffer. After sonication and filtration, the sample was analysed by high-performance liquid chromatography on a C18 column using UV diode array detection. Individual sulphonamides could be detected down to 0.01 ppm, whilst analyte identity could be confirmed by diode array spectrum down to 0.02 ppm.     

Ion-pair reversed-phase high-performance liquid chromatography analysis of oligonucleotides: retention prediction

An ion-pair reversed-phase HPLC method was evaluated for the separation of synthetic oligonucleotides. Mass transfer in the stationary phase was found to be a major factor contributing to peak broadening on porous C18 stationary phases. A small sorbent particle size (2.5 microm), elevated temperature and a relatively slow flow-rate were utilized to enhance mass transfer. A short 50 mm column allows for an efficient separation up to 30mer oligonucleotides. The separation strategy consists of a shallow linear gradient of organic modifier, optimal initial gradient strength, and the use of an ion-pairing buffer. The triethylammonium acetate ion-pairing mobile phases have been traditionally used for oligonucleotide separations with good result. However, the oligonucleotide retention is affected by its nucleotide composition. We developed a mathematical model for the prediction of oligonucleotide retention from sequence and length. We used the model successfully to select the optimal initial gradient strength for fast HPLC purification of synthetic oligonucleotides. We also utilized ion-pairing mobile phases comprised of triethylamine (TEA) buffered by hexafluoroisopropanol (HFIP). The TEA-HFIP aqueous buffers are useful for a highly efficient and less sequence-dependent separation of heterooligonucleotides.     

Comparative study for separation of aquatic humic substances by capillary zone electrophoresis using uncoated, polymer coated and gel-filled capillaries

Several comparative capillary zone electrophoresis (CZE) experiments were carried out by means of uncoated, polyvinyl alcohol (PVA) and polyacrylamide (PAA) coated silica open tubular capillaries and gel-filled capillaries (linear non-cross-linked polyacrylamide, PAGE, by a pre-coated PAA capillary) using different kinds of background electrolytes (BGEs) and organic modifiers for characterization of aquatic dissolved humic matter (DHM). Organic compounds, such as acetic acid, acetate buffer, methanol, ethylene glycol, acetonitrile, dimethylsulphoxide, 5 M urea and sodium dodecyl sulphate (SDS) were tested as sample modifiers to improve the separative power. The fractionation mode by a PVA coated open tubular capillary using 40 mM phosphate buffer at pH 6.8 and 5 M urea-water as the sample modifier turned out to be fairly practical as well as its PAA homologue. Linear non-cross-linked PAGE with 10% gel concentration and 5 M urea-water as the sample modifier using 40 mM phosphate buffer at pH 6.8 produced the most reliable results as to the adaptation of physical gels, especially if the interactions of humic solutes with the gel matrix are not critical. The addition of SDS in the linear PAGE gel increased the interaction of humic solutes with the gel matrix but also improved the separative power and strengthened the chaotropic effect of the urea modifier.     

Alternating Current Tensammetry of Tetraphenylborate (TPB) and its Application for Potassium Determination

Alternating‐current polarography of tetraphenylborate ion (TPB) in acetate buffer (pH 4 to 5) or 0.1 to 0.5 M NaCl produces a characteristic tensammetric (pseudocapacitive) peak at ?0.95 V (vs. SCE). Within a limited range (till about 0.2 mM), the tensammetric peak current is proportional to the TPB concentration but it levels off at higher concentration. TPB concentration can also be determined within 5 to 50 μM by measuring the capacity current at ?0.4 V or the differential pulse polarographic peak current at ?0.85 V. The tensammetric peak current was used to determine the solubility of potassium tetraphenylborate in acetate buffer and sodium chloride solutions. Also, a method for amperometric back‐titration of potassium ion was worked out and applied to the analysis of mineral water.     

Potassium and sodium chloride ion pairs are presumed to constitute a complex during elution from a Sephadex G-15 column with sodium phosphate buffer

When a mixed solution of 0.72 M potassium and sodium chloride was eluted from a Sephadex G-15 column with 0.025 M sodium phosphate buffer (pH 7.0), the elution profiles of ions showed that the potassium and chloride ion pair from the sample and the sodium and chloride ion pair produced by ion-exchange reaction, were eluted in the same fractions as if they constituted a complex. When a mixed solution of different concentrations of potassium and sodium chloride was eluted with the same buffer, the excess amount of one ion pair over the other was eluted freely from the presumed complex.