Ion-interaction Reversed-phase High-performance Liquid Research Articles

Determination of vanadium as 4-(2-pyridylazo)resorcinol–hydrogen peroxide ternary complexes by ion-interaction reversed-phase liquid chromatography

The separation and determination of the vanadium(V) ternary complex formed with 4-(2-pyridylazo)resorcinol (PAR) and hydrogen peroxide using ion-interaction reversed-phase high-performance liquid chromatography on a C 18 column has been investigated. The optimal mobile phase was a methanol–water solution (32:68, v/v) containing 3 m M tetrabutylammonium bromide, 5 m M acetic acid and 5 m M citrate buffer at pH 7, with absorbance detection at 540 nm. The stoichiometry of the ternary complex of vanadium at pH 6 in 10 m M acetate buffer using the mole ratio and Job’s method by HPLC indicated that the mole ratio of V(V):PAR:H 2O 2 was 1:1:1. The optimal conditions for precolumn formation of the ternary complex were 10 m M acetate, 7 m M H 2O 2, 0.3 m M PAR, and pH 6. The method gave relative standard deviations of retention time, peak area and peak height for the ternary complex of 0.187, 0.45 and 0.57%, respectively. The detection limit (at a signal-to-noise ratio of 3) for V(V) was 0.09 ng/ml in the digested sample using a 100-μl injection loop (or 0.09 μg/g in the solid fertiliser sample). The method was applied to the analysis of fertilisers (phosphate rocks and nitrogen, phosphorus and potassium fertiliser). The results for vanadium obtained by the HPLC method agreed well with those from magnetic sector inductively coupled plasma MS analysis.

Separation and determination of niobium(V) and tantalum(V) as 2-(5-bromo-2-pyridylazo)-5-[ N-propyl- N-(3-sulfopropyl)amino]phenol citrate ternary complexes in geological samples using ion interaction high-performance liquid chromatography

A method for the simultaneous separation and determination of Nb(V) and Ta(V) as ternary complexes formed with 2-(5-bromo-2-pyridylazo)-5-[ N-propyl- N-(3-sulfopropyl)amino]phenol (PAPS) and citrate was developed using ion interaction reversed-phase high-performance liquid chromatography (HPLC) on a C18 column. An artificial neural network (ANN) in combination with a reduced factorial experimental design was utilised to optimise the mobile phase compositions and the conditions used for pre-column complex formation. Under the optimum conditions determined by the ANN, the Nb(V) and Ta(V) complexes were eluted within 5 min. The detection limits (signal to noise ratio = 3, detection wavelength 600 nm) for Nb(V) and Ta(V) were 0.03 and 0.40 μg/l, respectively, which correspond to 0.03 and 0.40 μg/g in the solid samples. The method was applied to the analysis of geological samples and the results obtained by the HPLC method agreed well with the results obtained by ICP-MS and also with the certified values.

Determination of Niobium(V) and Tantalum(V) as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP)-citrate ternary complexes in geological materials using ion-interaction reversed-phase high-performance liquid chromatography

A method for the simultaneous separation and determination of Nb(V) and Ta(V) as ternary complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) and citrate using ion-interaction reversed-phase high performance liquid chromatography on a C 18 column has been developed. The mobile phase compositions and pre-column complex formation conditions were optimised. Under the optimum conditions, the Nb(V) and Ta(V) complexes were eluted within 4 min with a mobile phase of methanol-water (50% v/v) containing 12 mM tetrabutylammonium bromide and 12 mM citrate buffer at pH 7, with absorbance detection at 600 nm. The resulting % relative standard deviation of retention times, peak area and peak height for Nb(V) and Ta(V) complexes were 0.007, 0.000, 0.67, 2.69, 0.44 and 2.17, respectively. The detection limits (signal to noise ratio = 3) for Nb(V) and Ta(V) were 0.03 ppb and 0.41 ppb, respectively. The method was applied to the analysis of geological samples (granite, basalt and andesite) and the results for Nb(V) obtained by the HPLC method using standard addition calibration agreed well with ICP-MS analysis and with certified values for all materials. For Ta(V), good agreement with certified values was obtained for granite samples using standard addition, but interferences were observed for basalt and andesite which prohibited the determination of Ta(V) in these samples.

Determination of niobium(V) and tantalum(V) as 4-(2-pyridylazo)resorcinol–citrate ternary complexes in geological materials by ion-interaction reversed-phase high-performance liquid chromatography

A method for the simultaneous separation and determination of Nb(V) and Ta(V) as ternary complexes formed with 4-(2-pyridylazo)resorcinol (PAR) and citrate was developed using ion-interaction reversed-phase high-performance liquid chromatography on a C 18 column. Method parameters, such as pre-column complex formation conditions and composition of the complexes were investigated using spectrophotometry and HPLC. Under the optimum conditions, the Nb(V) and Ta(V) complexes were eluted within 12 min with a mobile phase of methanol–water (32:68, v/v) containing 5 m M acetate, 5 m M TBABr and 5 m M citrate buffer at pH 6.5, with detection at 540 nm. A typical separation efficiency was 33 000 and 20 000 theoretical plates per metre for Nb(V) and Ta(V), respectively. The relative standard deviation of retention times for the Nb(V) and Ta(V) complexes were 0.16% and 0.17% and for peak areas were 0.28% and 1.36%, respectively. The detection limits (signal-to-noise ratio=3) for Nb(V) and Ta(V) were 0.4 ppb and 1.4 ppb, respectively. Results obtained for standard reference rock samples agreed well with certified values and results obtained by inductively coupled plasma MS.

Separation of phenylurea pesticides by ion-interaction reversed-phase high-performance liquid chromatography Diuron determination in lagoon water

An ion-interaction HPLC method is developed for the separation of the phenylurea herbicides asulam, diuron, isoproturon, linuron and monuron. C 18 was used as stationary phase and octylammonium phosphate as ion-interaction reagent, in the presence of methanol or acetonitrile as organic modifier. Detection limits lower than 9 μg/l can be obtained without preconcentration steps. The method was applied to the analysis of diuron in a sample of lagoon water. Using liquid-liquid extraction, a diuron concentration of 42 μg/l was found.

High-performance liquid chromatography detection of sulfide in tissues from sulfide-treated mice.

The biological and forensic use of ion-interaction reversed-phase high-performance liquid chromatography for the determination of hydrogen sulfide-derived methylene blue is evaluated by measuring the sulfide content in tissues from sulfide-treated mice. Various preparative conditions were examined. The determinations of background levels of sulfide from brain, liver and kidney were compared to sulfide levels from mice exposed to 60 micrograms g-1 sodium hydrosulfide. At the time of death, significant increases above background sulfide levels were measured for all three biological tissues. To evaluate its forensic potential, we used this sulfide detection methodology to evaluate comparatively the sulfide levels from fresh and frozen samples of brain, liver and kidney. The stability of sulfide levels obtained from frozen brain makes this tissue the most reliable tissue for forensic evaluation. Samples of brain, liver and kidney obtained within 24 h of death by sulfide intoxication had demonstrable elevations in sulfide concentration.

Separation of food-related biogenic amines by ion-interaction reversed-phase high performance liquid chromatography. Tyramine, histamine, 2-phenylethylamine, tryptamine and precursor aminoacids. Application to red wine

Methods for the separation of food-related biogenic amines (histamine, tyramine, 2-phenylethylamine and tryptamine) have been developed based on ion-interaction reversed-phase liquid chromatography.

Simultaneous determination of nitrites, nitrates and amines by ion-interaction reversed-phase high-performance liquid chromatography : Application to lagoon water

The conditions for the simultaneous separation of aliphatic and aromatic amines, nitrites and nitrates by ion-interaction reversed-phase high-performance liquid chromatography (HPLC) were optimized. The mechanism that governs retention in this HPLC technique is discussed. Sensitivity of the order of 0.10 ppm for nitrites and nitrates can be obtained with octylamine orthophosphate as eluent at 210 nm. Amounts of 0.20 ppm of nitrates and 0.50 ppm of 1,4-phenylenediamine can be easily identified and determined in matrices as complex as sea water.

Determination of sulfide in brain tissue and rumen fluid by ion-interaction reversed-phase high-performance liquid chromatography

Determination of sulfide in brain tissue and rumen fluid by ion-interaction reversed-phase high-performance liquid chromatography

Determination of the principal anionic components in wines and soft drinks, by ion interaction reversed-phase high-performance liquid chromatography

Mise en evidence des conditions experimentales pour la separation et le dosage des anions, en utilisant les salicylates d'heptylamine et d'ocylamine comme agents d'interaction ionique. Les principaux acides organiques presents dans le vin (chlorures, phosphates) peuvent etre facilement separes et doses par cette methode

Role of the alkyl chain length of the ion interaction reagent, flow-rate, column packing and detection in ion interaction reversed-phase high-performance liquid chromatography in separations of anions using amine salicylates

The effect of different factors on retention in ion interaction reversed-phase high-performance liquid chromatography was investigated. In particular, the factors considered were the alkyl chain length of the lipophilic cation of the ion interaction reagent, the flow-rate, the size of the stationary phase packing and the choice of detector. The reagents used and compared were hexylamine, octylamine and decylamine salicylates, and the stationary phases were C 18 reversed phase with packing sizes of 5 (spherical) and 10 μm (irregular). A comparison was made between UV spectrophotometric (direct and indirect) and conductometric detections. Mixtures of inorganic and organic anions were separated and also some real samples. The system studied was shown to be suitable for analysis of nitrates in drinking waters and for the evaluation of the contents of some organic acids (acetic, succinic, malic and tartaric) in vinegars.