Sodium Heptanesulphonate Research Articles

Inhibition of corrosion of carbon steel by heptane sulphonic acid - Zn2+ system

Corrosion inhibition of carbon steel in dam water by sodium heptane sulphonate (SHS) and zinc ion system was investigated using weight loss and potentiodynamic polarization methods. Results of weight loss method indicated that inhibition efficiency (IE) increased as the inhibitor concentration increased. A synergistic effect existed between SHS and Zn 2+ . The influence of sodium potassium tartrate (SPT) on the IE of the SHS-Zn 2+ system was evaluated. As the immersion period increased, the IE decreased. Polarization study revealed that SHS-Zn 2+ system functioned as a cathodic inhibitor. AC impedance spectra revealed that a protective film was formed on the metal surface. The nature of the metal surface was analyzed by FTIR spectra, SEM and AFM analyses.

Rapid Screening of Volatile Ion-Pair Reagents Using UHPLC and Robust Analytical Method Development Using DoE for an Acetyl Cholinesterase Inhibitor: Galantamine HBr

As over 70% of pharmaceutical compounds are bases, the analysis of these basic compounds by high performance liquid chromatography (HPLC) continues to be of great value and interesting. Acetyl cholinesterase inhibitors (AChEIs), which contain the basic compounds like Rivastigmine tartrate, Galantamine hydrobromide and Donepezil with different polarities, were chosen for the study. A rapid screening of the volatile ion-pairing reagents was performed using modern techniques like ultra high performance liquid chromatography (UHPLC). The experiments were planned using the ‘Design of Experiments’ (DoE) approach to identify the LC–MS compatible ion-pair reagent. In this study, Heptafluorobutyric acid (HFBA) has given a very good peak shape with tailing factor at 1.4 and theoretical plates up to ~5,000 were observed, compared to tailing factor at 1.9 and theoretical plates up to ~3,000 with non-volatile ion-pair reagent sodium heptane sulphonate (SHS). Similarly retention with HFBA was optimum as ~5 min in short run time method compared to ~13 min with SHS. This ion-pair reagent has proved to be good replacement of sodium alkyl sulphonate modifiers. HFBA can also be used for semi-preparative work for isolation of impurities by just evaporating the solvents. It avoids the extraction of other inorganic modifiers.

SEPARATION OF DIFFERENT IONIC FORMS OF L-α-METHYLDOPA AND OTHER AMINO ACIDS BY REVERSED-PHASE ION-PAIR HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

The present work is devoted to the analysis of the phenomenon of “double peaks” of aminoacids in High Performance Liquid Chromatography. Therefore, we have carried out some experiments in order to confirm that the appearance of several peaks from the injection of a single compound was related to different ionic forms of this compound. It could be shown that elution of multiple peaks for L-α-methyldopa did not refer to its degradation products, but to the different ionic species present in the media. The same occurred with its derivative 3-O-methylmethyldopa and with dl-phenylalanine. The separation between ionic forms was possible due to the use of sodium heptanesulphonate, an anionic ion-pairing reagent, which selectively interacts with different charged species. These findings show that equilibrium species can be separated by an appropriate analytical method, depending on the employed conditions.

Determination of bisbenzylisoquinoline alkaloids by high-performance liquid chromatography

Reversed-phase ion pair chromatography with UV detection was used to determine nine type VI and VIII bisbenzylisoquinoline alkaloids: aromoline, obamegine, berbamine, homoaromoline, colorflammine, thalrugosine, norobaberine, tetrandrine and isotetrandrine. The eluent was acetonitrile—0.05 M dihydrogen phosphate buffer (pH 3.0) (27:73, v/v) containing 0.1% diethylamine and 2 m M sodium heptanesulphonate. Five alkaloids were determined in the stem woods of a Lauraceous plant, Dehaasia triandra Merr.

High-performance liquid chromatographic measurement of urocanic acid isomers and their ratios in naturally light-exposed skin and naturally shielded skin

We have developed methods for sampling and extraction of trans-urocanic acid and cis-urocanic acid from human skin, and subsequent high-performance liquid chromatographic measurement of these isomers. Sampling involves applying cellophane adhesive tape to the skin for 10 s. Urocanic acid isomers were completely extracted by immersing the tape in KOH solution. The HPLC column was a Tosoh ODS 80 TS (250×4.6 mm I.D., 7 μm average particle size) eluted with 20 m M potassium dihydrogenphosphate containing 1 g/l sodium heptanesulphonate (pH 3.7)–acetonitrile (93:7, v/v) at a flow-rate of 1.0 ml/min. The isomers were detected by UV absorbance at 264 nm. This technique was used to analyze the ratio of trans-urocanic acid/ cis-urocanic acid on human skin at various sites on the body. It was found that the ratio was low in naturally light-exposed skin and high in naturally shielded skin.

Selenoamino acid speciation using HPLC-ETAAS following an enzymic hydrolysis of selenoprotein

A high-pressure liquid chromatography-electrothermal atomic absorption spectroscopy (HPLC-ETAAS) hyphenated technique was used for the determination of seleno compounds present in a selenium-enriched yeast. Conditions were optimized for the separation and quantification of the selenoamino acids, selenocystine and selenomethionine, in the presence of other compounds. The separation was achieved by ion-pairing chromatography using sodium heptanesulphonate as the anionic counterion. On-line detection was carried out using electrothermal atomic absorption with palladium(II) as a matrix modifier. Different extraction procedures were tested on a selenium-enriched yeast. A 92% recovery of the total selenium present in the material was obtained. Attempts to evaluate selenium speciation were carried out ; selenomethionine and selenocystine were identified as the major components (42% and 35% respectively).

Solid-phase extraction of nicotine and its metabolites for high-performance liquid chromatographic determination in urine.

A solid-phase extraction, using Extrelut-1 glass columns, has been applied to urine samples of both passive and active smokers for high-performance liquid chromatographic determination of nicotine and its metabolites cotinine and trans-3'-hydroxycotinine. Chromatography was performed using a reversed-phase LC8DB column and a mobile phase consisting of water-acetonitrile (80:9, v/v) containing 5 ml triethylamine, 670 mg/l sodium heptanesulphonate, and 0.034 M each of K2HPO4 and citric acid (pH 4.4), at a flow-rate of 1.6 ml/min. The results obtained indicate that solid-phase extraction is a reliable and quick procedure which can be applied also to other nicotine metabolites.

Determination of thiamine (vitamin B,) and riboflavin (vitamin B2) in meat and liver by high-performance liquid chromatography

HPLC methods described so far for the determination of thiamine and riboflavin in meat samples have used mostly fluorescence detection. The aim of this work was to elaborate a suitable method with UV detection for this purpose and to compare the thiamine and riboflavin contents obtained for meat and liver samples from various pig groups. Homogenized spare rib, chop, ham and fiver samples were treated with acid and heated (at 121°C, 30 min), followed by enzymatic digestion to release the vitamins. After a clean-up procedure the simultaneous determination of thiamine and riboflavin was performed with a Nucleosil ODS (3 μ m) packed column at 45°C. The mobile phase was phosphate buffer (pH 3.0)-acetonitrile (84:16, v/v) containing 5 m M sodium heptanesulphonate. The relative standard deviation was 5% for thiamine and 12% for riboflavin in meat and 8% for thiamine and 5% for riboflavin in liver for four parallel determinations.

Stability-indicating high-performance liquid chromatographic assay for α-methyldopa in sustained-release capsules

A stability-indicating high-performance liquid chromatographic assay has been developed for the analysis of α-methyldopa (MD) in sustained-release capsules and in the presence of MD decomposition products and an MD industrial impurity, 3-O-methyl-methyldopa (MMD). The method utilizes reversed-phase chromatography (cyano-bonded column), an acidic mobile phase containing sodium heptanesulphonate as ion-pairing reagent and UV detection. Detector responses were linear in the ranges 0.5–200 μg/ml for MD and 0.2–100 μg/ml for MMD. The mean recoveries of MD from authentic sample and sustained-release capsules were 100.09 ± 0.38 and 100.38 ± 0.46%, respectively. The recovery of MD added to degraded MD were 99.69% by the proposed method and 153.13% by the US Pharmacopeial (USP) spectrophotometric method. The method is sensitive, accurate and rapid and can be used in routine analysis for MD.

Fluorescence assay for small peptides and amino acids: High-performance liquid chromatographic determination of selected substrates using activated S-flunoxaprofen as a chiral derivatizing agent

The applicability of the fluorescent S-flunoxaprofen, activated to the corresponding acyl chloride, as a chiral derivatizing agent for amino acids and small peptides was evaluated. The amino acid or peptide solution was evaporated to dryness. The carboxylic moieties were esterified with 3 M hydrochloric acid in 2-propanol. The solvent and hydrochloric acid were evaporated, and the residue was dissolved in aqueous sodium heptanesulphonate and extracted with benzene-butanol (85:15, v/v). The organic phase was evaporated and S-flunoxaprofen chloride reagent solution (in dichloromethan) added, together with 20 mg of anhydrous sodium carbonate. After 60 min at 40°C the solvent was evaporated and the residue reconstituted in mobile phase ( n-hexane-dichloromethane-ethanol). Resolution of the diastereomeric derivatives was accomplished on a Zorbax Sil high-performance liquid chromatography column. The eluate was monitored either fluorimetrically at 305/355 nm or by measuring the UV absorption at 305 nm. The procedure leads to highly fluorescent derivatives of amino acids or small peptides, which are resolvable on silica gel stationary phases.

High-performance liquid chromatographic determination of ampicillin and its metabolites in rat plasma, bile and urine by post-column degradation with sodium hypochlorite

A high-performance liquid chromatographic method has been developed for the determination of ampicillin (1) and its metabolites [(5 R, 6 R)-ampicilloic acid (2), the (5 S, 6 R)-epimer (3) and the corresponding (2 R)-piperazine-2′, 5′-dione (4)] in rat plasma, bile and urine. The method involves the separation of 1–4 from the background components of the biological fluids on a reversed-phase C 18 column, using sodium heptanesulphonate as an ion-pairing agent and methanol in the mobile phase, followed by post-column degradation with 1.5 M sodium hydroxide-0.02% sodium hypochlorite solution at ambient temperature, and detection of the degradation product(s) of each compound at 270 nm. The detection limits were about 25 ng for each compound at a signal-to-noise ratio of 3. At concentrations of 2–5 μ/ml of each compound, the within- and between-run precisions (relative standard deviation) were 0.77–7.15% and 1.76–5.96%, respectively. The plasma, biliary and urinary levels of 1 and its metabolites were determined by the proposed method after intravenous administration of 1 to rats.

Fluorimetric determination of amino acids by high-performance liquid chromatography using a hollow-fibre membrane reactor

A high-performance liquid chromatographic method has been developed for the determination of primary amino acids. The method involves separation of primary amino acids on a C 18 column using sodium heptanesulphonate as an ion-pairing agent, post-column derivatization with o-phthalaldehyde and 2-mercaptoethanol introduced into the main flow stream using a sulphonated hollow-fibre membrane reactor immersed in their solutions and fluorimetric detection of derivatives (λ ex = 340 nm, λ em = 450 nm). A higher or similar sensitivity was obtained compared with the conventional post-column derivatization method. The detection limits were 0.2–2.3 pmol at a signal-to-noise ratio of 3. For amounts of 48–110 pmol, the precision was of the order of 1.1–4.0% (relative standard deviation, n = 20).

High-performance liquid chromatography of paraquat and diquat in urine with rapid sample preparation involving ion-pair extraction on disposable cartridges of octadecyl-silica

A high-performance liquid chromatographic system is presented which separates the paraquat, diquat and 1,1′-diethyl-4,4′-bipyridyldiylium (internal standard) dications in under 7 min. An octadecyl-silica (ODS-silica) column is used with an eluent of 25 % methanol (v/v) containing sodium heptanesulphonate (0.01 M) and a diethylamine-orthophosphoric acid buffer. The method is suitable for the analysis of paraquat and diquat in commercial weedkillers and human urine samples following poisoning. A rapid procedure for the extraction of the herbicides from urine has been developed using disposable cartridges of ODS-silica pre-treated with sodium heptanesulphonate. The quaternary compounds are extracted as ion-pairs with the hydrophobic sulphonate anions.