Sensitive Ion Chromatographic Method Research Articles

Biotransformation of urea in the water of water bodies

Introduction. The transformation of substances is an urgent problem of environmental hygiene. Urea (carbamide) is a product of human and animal life - enters water objects with household collector wastewater, surface runoff in areas that use urea as fertilizer, waste discharges from livestock complexes, and effluents of enterprises that produce carbamide. Two aspects of the problems associated with urea contamination of water bodies can be identified: the lack of a direct instrumental method for controlling urea and the lack of a comprehensive approach to controlling urea and its biotransformation products: ammonium, nitrites and nitrates. These two factors determined the relevance of the research. Materials and methods. The studies used the «Stayer» ionic chromatography system with anionic and cationic separation columns: Phenomenex Star-Ion A-300 100/4.6 USA; Shodex IC YS-50 150/4.6 Japan; when developing the urea analysis method, the «Aquilon» cationic column AQULINE C1P, 5µ,150/4.6 was used. The detection is conductometric and amperometric. The research objects were: surface, bottled, tap water, model water solutions of carbamide. As a urease source, the soil (sod-podzolic) from the Educational and Experimental Soil-Ecological Center of the Lomonosov Moscow State University “Chashnikovo” was used. Results. A new highly sensitive ion chromatographic method for determining urea in the water of various water bodies with a sensitivity of 5 mg/dm3 with direct sample input and using sample preparation - 0.5 mg/dm3 is proposed. The results of studies of model aqueous solutions of urea, surface water, tap water of Moscow, many bottled water samples on the content of urea and products of its biochemical transformation are presented. The presence of urea in the surface water and tap water of Moscow was revealed, and a correlation between the urea content and ammonium ions, nitrites and nitrates in the water was stated. Limitations of the study. The studies were carried out with waters whose total mineralization did not exceed 15 mg-eq/dm3 (water of river Don), and the urea content established in the water samples was not lower than 0.5 mg/dm3. Conclusion. When monitoring urea contamination of various water bodies, it is necessary to consider the products of its biotransformation under the action of urease, for as a result of the processes of urea biotransformation, a low-toxic substance can form more toxic products: nitrites, nitrates and ammonium. Applying the kinetic approach to study the processes of urea biotransformation in water under model conditions showed that the extreme type of kinetic curves corresponds to the formation of intermediate products - nitrites, and the increasing type corresponds to the formation and accumulation of final products - nitrates and ammonium ions.

Determination of Inorganic Anions in Seawater Samples by Ion Chromatography with Ultraviolet Detection Using Monolithic Octadecylsilyl Columns Coated with Dodecylammonium Cation.

A fast and sensitive ion chromatographic method for the simultaneous determinations of six inorganic anions [iodate (IO3-), bromate (BrO3-), bromide (Br-), nitrite (NO2-), nitrate (NO3-), and iodide (I-)] in seawater is described using dodecylammonium (DA+)-coated monolithic octadecylsilyl (ODS) columns, a concentrated aqueous NaCl mobile phase containing dodecylammonium chloride (DAC), and a UV detector. The DA+-coated monolithic ODS columns show greater retention for iodate and weaker retention for iodide, compared to dilauryldimethylammonium (DDA+)-coated monolithic ODS columns. Six anions were determined within 12 min with baseline separation without interferences by matrix ions, such as Cl- and SO42-, in seawater, compared to a DA+-coated particulate ODS column (it took 25 min per sample) obtained previously. The detection limits (DLs) were comparable to the DA+-coated particulate ODS column: IO3- (7.7 μg L-1), BrO3- (20), Br- (88), NO2- (0.9), NO3- (1.9), and I- (0.9) with a 100-μL sample injection. A larger sample volume injection lowered the DLs of IO3-, BrO3-, and I-. The good performance was maintained for ca. 2 years examined. The robust IC system developed in the present work was successfully applied to real seawater samples without sample dilution in the recovery rates of 93 - 104% for all ions.

A simple and sensitive method for the determination of iodide and iodate in raw, ultraviolet- and ozone-treated aquacultural seawater samples using ion chromatography coupled to an ultraviolet detector

A new and sensitive ion chromatographic method for the speciation of iodine in aquacultural seawater samples has been developed.

Simultaneous determination of choline, carnitine and betaine in premixes by non-suppressed ion chromatography

A simple, highly sensitive ion chromatographic method for the simultaneous determination of betaine, choline and carnitine in feed premixes is described. Premixes were extracted via ultrasonication in water for 20 min and extracts were analyzed by ion chromatography using an aqueous 3.0 mmol L−1 methane sulfonic acid solution containing 15% (v/v) acetonitrile as the eluent and an IonPac SCS1 column. The composition of the mobile phase was optimized for the efficient separation of the three main analytes from each other as well as from common inorganic cations and trimethylamine, which is an ingredient for the synthesis of the analytes. The recoveries of choline, carnitine and betaine spikes added to premixes were all greater than 90% with replicate relative standard deviations of less than 10%. The limits of detection of this method for these analytes in premixes were calculated to be 10, 6 and 20 mg kg−1, respectively.

Ion chromatography for determination of nitrite and nitrate in seawater using monolithic ODS columns

A fast and highly sensitive ion chromatographic method using monolithic ODS columns was developed for the determination of nitrite (NO 2 −) and nitrate (NO3 −) in seawater. Two monolithic ODS columns (50 mm × 4.6 mm i.d. + 100 mm × 4.6 mm i.d.) connected in series were coated and equilibrated with 5 mM cetyltrimethylammonium chloride (CTAC) aqueous solution. The column efficiency with 0.5 M NaCl as the mobile phase did not decrease in spite of the increase in flow rate of the mobile phase. Thus, good chromatograms were obtained within 3 minutes for NO 2 − and NO 3 − in artificial seawater without interferences by coexisting ions. The detection limit (S/N = 3) with UV detection at 225 nm was 0.8 and 1.6 μg/L for NO 2 − and NO 3 −, respectively. The characteristics of the monolithic CTA +-coated ODS columns were discussed. The present method was successfully applied to the fast and sensitive determination of NO 2 − and NO 3 − in real seawater samples.

Sensitive and selective ion chromatographic method for the determination of trace beryllium in water samples

A selective and sensitive ion chromatographic method has been developed for the determination of beryllium in a number of water samples at low-μg/l concentrations. The separation was performed on a 250×4.0 mm I.D. iminodiacetic acid functionalised silica gel column. Chromatographed Be(II) was detected using visible detection at 590 nm following post-column reaction with chrome azurol S (CAS). The optimum separation and derivatisation conditions were studied in detail. The optimum eluent conditions were found to be 0.4 M KNO 3, adjusted to pH 2.5 using HNO 3, with optimum post-column detection being achieved using a solution containing 0.26 m M CAS, 2% Triton X-100, 50 m M 2-( N-morpholino)ethanesulfonic acid, pH 6.0. Under the above conditions, the concentration detection limit for Be(II) was found to be 3 μg/l in a standard solution and 4 μg/l in a typical tap water sample, using a 250 μl injection. The method was linear over the investigated range of 10 μg/l to 10 mg/l and highly reproducible. The method was successfully applied to a number of water samples of varying matrix complexity, including simulated seawater, and also to a natural freshwater certified reference material NIST 1640.

Determination of thiosulfate, thiocyanate and polythionates in a mixture by ion-pair chromatography with ultraviolet absorbance detection

A sensitive ion chromatographic method has been developed for the determination of mixtures of thiosulfate, thiocyanate and polythionates (tri-, tetra-, penta- and hexathionate). The proposed method is based on the separation of the sulfur anions on an octadecylsilica (ODS) column with an acetonitrile–water mobile phase containing tetrapropylammonium salt (TPA) as an ion-pairing reagent and the ultraviolet absorption detection of the sulfur anions. When an acetonitrile–water (20:80, v/v) solution (pH 5.0) containing 6 m M TPA was used as a mobile phase at flow-rate of 0.6 ml min −1, the sulfur anions were resolved within 22 min. The detection limits defined at S/N=3 and 230 nm were very low for all anions, except trithionate: 30 n M for thiosulfate, 60 n M for thiocyanate, 20 n M for tetrathionate, 15 n M for pentathionate and 18 n M for hexathionate. The proposed method gave recoveries ranging from 95.0 to 105.0% when applied to the determination of polythionates added to hot spring waters.

Determination of Iodide in Seawater by Ion Chromatography

A simple and highly sensitive ion chromatographic method with UV detection was developed for iodide (I(-)) in seawater. A high-capacity anion-exchange resin with polystyrene-divinylbenzene matrix was used for both preconcentration and separation of iodide. Iodide in artificial seawater (salinity, 35‰) was trapped quantitatively (98.8 ± 0.6%) without peak broadening on a preconcentrator column and was separated with 0.35 M NaClO(4) + 0.01 M phosphate buffer (pH 6.1). On the other hand, the major anions in seawater, chloride and sulfate ions, were partially trapped (5-20%) and did not interfere in the determination of I(-). The detection limit for I(-) was 0.2 μg/L for 6 mL of artificial seawater. The present method was applied to determination of I(-) (ND - 18.3 μg/L) and total inorganic iodine (I(-) + IO(3)(-) - I, 50.0-52.7 μg/L) in seawater samples taken near Japan.

An ion chromatographic method for the estimation of tresyl groups on activated supports

A simple and sensitive ion chromatographic method for the estimation of tresyl groups on several activated supports (tresylated diol silica, tresylated Sepharose 4B and Tresyl-5PW) has been developed. The method involves the hydrolysis of tresyl groups on the supports followed by ion chromatographic determination of the liberated 2,2,2-trifluoroethanesulfonic acid. It is useful for the prediction of the immobilization efficiency of proteins.

Ion chromatography method for iminodiacetic acid determination in biological matrices in the presence of nitrilotriacetic acid

A sensitive ion Chromatographic method for the determination of iminodiacetic acid in the presence of nitrilotriacetic acid in cell-free extracts is described using a mixture of carbonate, sodium hydroxide and 4-cyanophenol as the eluent. The eluent conductivity was chemically suppressed with a membrane suppressor and a conductivity detector was used for subsequent detection. The membrane was continuously regenerated with a sulphuric acid solution. Using a 20-μl injection loop, the detection limit for iminodiacetic acid was 230 μg/l. The influence of the eluent composition on the chromatography of iminodiacetic acid and interference by compounds present in biological matrices are discussed.