Ion-pair Reversed-phase High Performance Research Articles

Assay of N1-Acetylpolyamine Oxidase Activity with N1,N11-Didansylnorspermine as the Substrate by Ion-Pair Reversed Phase High Performance Liquid Chromatography

An assay method to measure N(1)-acetylpolyamine oxidase (PAO) activity with N(1),N(11)-didansylnorspermine (DiDNS333) as the substrate by high performance liquid chromatography (HPLC) was developed. Dansylpolyamines were synthesized, and their activity as a substrate for partially purified PAO from rat liver was evaluated. Among the dansylpolyamines, DiDNS333 was a useful substrate for the development of the PAO assay method. DiDNS333 was degraded by PAO to 1-dansylamido-3-propanal (DNS3al) and N(1)-dansylnorspermidine (DNS33). As DNS3al was separated into two peaks by HPLC of the assay mixture containing aminoguanidine, determination of DNS33 was used for the development of the assay method. When the assay method was applied to inhibition studies, the DNS33 peak on the chromatogram was consistently produced, and weak interference was found in the incubation with higher concentrations of natural polyamines. This result suggested that contaminating polyamines in biological samples do not interfere with this method. When the assay method was applied to cell extract from Chinese hamster ovary cell samples, the PAO activity, even at the low level in the cells, could easily be detected with as little as 10 microg of protein, which corresponds to 1x10(5) cells. This HPLC method is a rapid, sensitive and useful assay for the measurement of PAO activity.

Analysis of Risedronate and Related Substances by Ion-Pair Reversed-Phase High-Performance Liquid Chromatography with Evaporative Light-Scattering Detection

A simple method has been developed for the analysis of risedronate and related substances by ion-pair reversed-phase high-performance liquid chromatography (RPLC) with evaporative light-scattering detection (ELSD). After optimization of the chromatographic conditions, satisfactory separation of the compounds was achieved on an Intersil C(8) column with an isocratic mobile phase: 8:4:88 (v/v) acetonitrile-methanol-12 mM ammonium acetate buffer containing 35 mM n-amylamine (pH 7.0). The mobile-phase flow rate was 1.0 mL min(-1). The calibration plot was linear in the range of 352 to 1760 microg mL(-1) for risedronate. The precision and reproducibility were 0.3 and 0.5%, respectively. The average recovery of risedronate was 100.4% and the RSD was 0.6%. The method was validated and shown to be precise, accurate, and specific for the assay of risedronate in both bulk material and dosage forms. The proposed liquid-chromatographic method can be satisfactorily used for the quality control of risedronate.

Insights into the mechanism of separation of heparin and heparan sulfate disaccharides by reverse-phase ion-pair chromatography

Reverse-phase ion-pair high performance liquid chromatography (RPIP-HPLC) and ultra-performance liquid chromatography (RPIP-UPLC) are increasingly popular chromatographic techniques for the separation of organic compounds. However, the fine details of the RPIP separation mechanism are still being debated. Many factors including type and concentration of the ion-pairing reagent, mobile phase pH, organic modifier, ionic strength, and stationary phase all play a role in the overall efficiency and optimization of ion-pairing separations. This study investigates the role that competition between ion-pairing reagents with different steric bulk and hydrophobicity plays in the separation of structural isomers of heparin and heparan sulfate (HS) disaccharides. In addition to providing insights into the mechanism by which RPIP-HPLC can resolve closely related disaccharides, the use of competition between ion-pairing agents could lead to new methods for the separation of larger heparin and HS oligosaccharides. This approach should also be applicable to the analysis of other compound classes, and could lead to a general approach for the chromatographic resolution of mixtures of charged analytes having similar structures.

Analysis of Fluorescent Dye-labeled Oligonucleotides by Ion-Pair Reversed-Phase High-Performance Liquid Chromatography

Abstract The ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) of fluorescent-labeled oligonucleotides separation was established, and the concentration of triethylamine-acetic acid (TEAA, 0–0.15 M), pH value (4.5–7.0), and gradient strength were optimized. The retention mechanism of fluorescent dye-labeled oligonucleotides was evaluated by comparing the retention of 5, 10, 15-mer unlabeled oligonucleotides with that of 5'end carboxyfluorescein (5'FAM)-labeled oligonucleotides. In addition, TaqMan™ probes as well as other fluorescent dye-labeled oligonucleotides were considered for separation. The results show that the best resolution of different length fluorescent dye-labeled oligonucleotides was observed at a TEAA concentration of 0.01 M and pH 7.0. The retention behavior of fluorescent-labeled oligonucleotides was significantly different from that of the unlabeled isomers; therefore, they can be separated completely. We found that the retention of unlabeled oligonucleotides enhanced with the increase of the length of the molecule. In contrast, the retention of fluorescent-labeled oligonucleotides reduced with the increase of the length of the molecule. Because the hydrophobicity of fluorescent dyes can greatly impact the retention, the oligonucleotides labeled using fluorescent dyes with higher hydrophobicity would have a longer retention time. However, the effect of the hydrophobicity was limited as the length of the oligonucleotide was increased to a certain level.

Optimization and validation of an ion‐pair RP‐HPLC‐UV method for the determination of total free iodine in rabbit plasma: application to a pharmacokinetic study

An ion-pair reverse-phase high performance liquid chromatographic method with UV-vis detection has been developed for the determination of total free iodine in rabbit plasma after vaginal administration of povidone-iodine (PVP-I). Sample preparation was done by protein precipitation with acetonitrile in 96-well format and aspirin was used as the internal standard. The 100 microL sodium thiosulfate solution (5 g L(-1)) was added to 100 microL plasma sample before protein precipitation, to convert the total free iodine in plasma to iodide (I(-)). Separation was performed on a C(18) column (200 x 4.6 mm i.d., 5 microm). The mobile phase consisting of a mixture of water phase (containing 10 mmol L(-1) 18-crown-6 ether, 5 mmol L(-1) octylamine and 5 mmol L(-1) sodium dihydrogen phosphate, pH adjusted to 6.0 with phosphoric acid) and acetonitrile in the ratio 70:30 (v/v) was delivered isocraticly at a flow rate of 1.0 mL min(-1). The method was sensitive with a lower limit of quantification of 0.005 microg mL(-1), with good linearity (r(2) > 0.9990) over the linear range of 0.005-2 microg mL(-1). All the validation data, such as linearity, accuracy and precision, were within the required limits. The method was successfully applied to study the pharmacokinetic of PVP-I in rabbits after vaginal administration.

Quantitative determination of acetaminophen, phenylephrine and carbinoxamine in tablets by high-performance liquid chromatography

An alternative methodology for analysis of acetaminophen (Ace), phenylephrine (Phe) and carbinoxamine (Car) in tablets by ion-pair reversed phase high performance liquid chromatography was validated. The pharmaceutical preparations were analyzed by using a C18 column (5 μm, 300 mm, 3.9 mm) and mobile phase consisting of 60% methanol and 40% potassium monobasic phosphate aqueous solution (62.46 mmol L-1) added with 1 mL phosphoric acid, 0.50 mL triethylamine and 0.25 g sodium lauryl sulfate. Isocratic analysis was performed under direct UV detection at 220 nm for Phe and Car and at 300 nm for Ace within 5 min.

Determination of azithromycin by ion-pair HPLC with UV detection

An ion-pair reversed phase high performance liquid chromatographic method with UV detection was developed for the determination of azithromycin using sodium heptanesulfonate as an ion-pair reagent. The mobile phase consisted of a mixture of ammonium dihydrogen phosphate (0.045M, pH 3.0 adjusted by phosphoric acid):acetonitrile 47:15 (v/v) and the concentration of sodium heptanesulfonate in the aqueous phase was 0.002M. UV detection was performed at 210nm. The chromatographic column was Dikma Technologies Diamonsil C18 column, 5μm 150mm×4.6mm, which was maintained at 25°C. Applying the method to a stability study of azithromycin eye drops, it was found that the related substance could be detected and the profile of the AZM peak was symmetrical and the column efficiency was high. Accordingly, it is suitable for the routine analysis and stability testing of azithromycin preparations.

Comparison of Biotransformation of Inorganic Selenium by Lactobacillus and Saccharomyces in Lactic Fermentation Process of Yogurt and Kefir

The aim of the present study was to characterize, quantify, and compare the different selenium species that are produced when lactic fermentation with two different types of microorganisms, bacteria (Lactobacillus) and yeast (Saccharomyces), take place to produce yogurt and kefir, respectively, and to study the transformation process of these species as a function of time. These two dairy products were chosen for the study because they are highly consumed in different cultures. Moreover, the microorganisms present in the fermentation processes are different. While the bacteria Lactobacillus is the one responsible for yogurt fermentation, a partnership between bacteria and the yeast Saccharomyces causes kefir fermentation. A comparative study has been carried out by fermenting Se(IV) enriched milk in the presence of both types of microorganisms, where the concentration range studied was from 0.5 to 20 microg g (-1). Enzymatic extraction enabled selenium speciation profiles, obtained by anionic exchange and ion-pairing reversed phase high performance liquid chromatography (IP-RP-HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) detection. Scanning electron microscopy (SEM) applied to the enriched samples showed segregated Se (0), at added concentrations higher than 5 microg g (-1). The main Se species formed depended on the type of microorganism involved in the fermentation process, SeCys 2 and MeSeCys being the main species generated in yogurt and SeMet in kefir. The results obtained are different for both kinds of samples. Lactic fermentation for yogurt produced an increment in selenocystine (SeCys 2) and Se-methylselenocysteine (MeSeCys), while fermentation to produce kefir also incremented the selenomethionine (SeMet) concentration. The Se species are stable for at least 10 and 15 days for kefir and yogurt, respectively. After this period, selenocystine concentration decreased, and the concentration of Se-methylselenocysteine was found to significantly increase.

Separation of geometrical isomers of {Fe[3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine]3}2+ ([Fe(PDT)3]2+) using ion-pair reversed-phase high performance liquid chromatography

A method has been developed for the separation of two geometrical isomers of the {Fe[3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine]3}2+([Fe(PDT)3]2+) using ion-pair reversed-phase high performance liquid chromatography (RP-HPLC). The effects of the chromatographic conditions, such as the content of acetonitrile and the type and concentration of the ion-pair reagents (sodium perchlorate (NaClO4) or sodium dodecyl sulfate (SDS)) in the binary mobile phase (acetonitrile and water), on the retention factor (k), resolution, and selectivity were iscussed. It was found that no matter how the ion-pair reagent was NaClO4 or SDS at different concentrations, the acetonitrile content in the mobile phase has good linear regression equations with the ln k of the two isomers. It was also observed that SDS showed more positive effect on the k of the two geometrical isomers than that of NaClO4. Moreover, the separation of the two isomers in the ternary mobile phase (acetonitrile, methanol and water) was developed. The chromatographic conditions, including the content of the organic modifier (acetonitrile and methanol) and the type and concentration of the ion-pair reagents (SDS and NaClO4), were optimized. Two geometrical isomers were rapidly and successfully separated under the optimized conditions, which used acetonitrile/methanol/water (20: 50: 30, v/v/v) as the mobile phase and 60 mmol/L NaClO4 as the ion-pair reagent. Good linear regression equations between the peak areas and concentrations for the two isomers were obtained. The detection limits of the fac-isomer and mer-isomer were 4.28 and 3.44 ng/mL (S/N = 3), respectively.

Determination of arsenic species in human urine using high performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS)

A speciation technique for arsenic (As) has been applied using ion pair reverse phase-high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS). Six As-species (arsenite, arsenate, dimethylarsinic acid, dimethylarsinous acid, monomethylarsonic acid and monomethylarsonous acid) have been separated with isocratic elution within less than 6 minutes. A cation exchange column was used for separation of AsB, AsC, Tetra (Me4As+) and TMAsO. The As chemical form and oxidation state is highly important in respect to toxicity; therefore total As-determination is insufficient for a complete toxicological evaluation and risk assessment. Arsenic-speciation has been studied on urine samples of children from an As-affected area in the Iron Quadrangle, Brazil. DMAsV and MMAsV were the major urinary metabolites in these samples. The mean value for total As-concentration of all samples (n = 15) was 26.3 ng As mL−1 with a range of 16.1 to 55.2 ng As mL−1. TMAsO and AsC (arsenocholine) were not detected in this study. In most samples, monomethylarsonous acid [MMAsIII] was detected up to 2.0 ng As mL−1. DMAsIII was not detected at any time, most probably due to volatilisation and some oxidation to DMAsV. The chromatographic recoveries, calculated from ([sum(species) × 100]/total As in urine samples), ranged from 77.4 to 94.9%. This work also contributes to the pertinent discussion regarding the reliability of MMAsIII/DMAsIII speciation in urine.

Comparison of pharmacokinetics, efficacy and toxicity profile of gemcitabine using two different administration regimens in Chinese patients with non-small-cell lung cancer

To conduct a randomized comparative trial of pharmacokinetics, efficacy and toxicity profile treatment with 1200 mg/m(2) gemcitabine using standard 30-min infusion or fixed dose rate (FDR) infusion [10 mg/(m(2) x min)] on days 1 and 8 plus carboplatin AUC (area under curve) 5 on day 1 in Chinese non-small-cell cancer patients. Twelve patients were enrolled in this study. Plasma gemcitabine concentrations were measured by ion-pair reversed phase high performance liquid chromatography. Antitumoral activity and toxicity of gemcitabine was assessed according to World Health Organization criteria. The obtained mean parameters, such as T(1/2) (elimination half time), AUC, and CL (clearance), were consistent with those reported in literature. Qualified response rate in our study was 33.3% for standard arm and 50% for FDR arm. Additional 50% and 33.3% patients contracted stable disease (SD) in standard arm and FDR arm, respectively. The predominant toxicity was hematologic, and patients in the standard infusion arm experienced consistently more hematologic toxicity. Pharmacokinetic and clinical data in this trial support the continued evaluation of the FDR infusion strategy with gemcitabine.

Speciation, quantification and stability of selenomethionine, S-(methylseleno)cysteine and selenomethionine Se-oxide in yeast-based nutritional supplements

The speciation and stability of organoselenium compounds present in the selenized yeast evaluated in National Cancer Institute human intervention trials were examined along with those of related supplements. Total selenium was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES), ICP-mass spectrometry (ICP-MS) and/or electrothermal atomic absorption spectrometry (ET-AAS) after microwave digestion. Enzymatic extraction enabled selenium speciation profiles to be obtained by ion-pair reversed phase high performance liquid chromatography (HPLC) with ICP-MS detection. Extracts were also subjected to chloroformate derivatization followed by Se and S specific GC analysis with atomic emission detection (GC-AED). Currently available and archived supplements show major differences in speciation for selenomethionine, selenomethionine Se-oxide and S-(methylseleno)cysteine with respect to time and conditions of storage. The formation of the latter compound is reported under different synthetic and elevated temperature conditions.

Highly sensitive and simple method for measurement of pipecolic acid using reverse-phase ion-pair high performance liquid chromatography with tris(2,2′-bipyridine)ruthenium(III) chemiluminescence detection

A new, highly sensitive chemiluminescence method for measurement of pipecolic acid in various substances such as human serum, cow's milk, beer, and apple juice has been developed. The method is based on reverse-phase ion-pair high performance liquid chromatographic separation and subsequent tris(2,2′-bipyridine)ruthenium(III) chemiluminescence detection. It was confirmed that imino acids show strong chemiluminescence upon mixing with tris(2,2′-bipyridine)ruthenium(III). A calibration graph, based on a standard pipecolic acid solution, was linear over the range 5.0 × 10 −9 M to 2.0 × 10 −5 M and the detection limit was 24 fmol (signal-to-noise ratio = 3). This highly sensitive and selective determination method can be applied to selected samples without purification or pre-concentration procedures. Compared to the previous HPLC methods, the proposed method is easier, more sensitive, and time-saving.

Retention of quinolones on human serum albumin and α 1-acid glycoprotein HPLC columns: Relationships with different scales of lipophilicity

The retention of 10 quinolone antibacterial agents on HPLC stationary phases supporting human serum albumin (HSA) or α 1-acid glycoprotein (AGP) was investigated. Among ofloxacine and flumequine, the two chiral compounds in the selected set, only the latter showed a split chromatographic peak and only on HSA but not on AGP, indicating that enantioselective specific sites play only a minor role in the retention. The retention of quinolones, which included four acidic and six zwitterionic congeners, was correlated with various lipophilicity scales: (i) theoretically calculated values, c log P, (ii) values measured at pH 7.4 by the shake-flask method, log D 7.4, and (iii) values extrapolated by retention data measured by ion-pair reversed-phase high performance liquid chromatography (RP-HPLC). We assumed that the latter values, log P i.p., were close to the lipophilicity of the neutral forms, log P N, for both acidic and zwitterionic congeners. No relationship was found between retention on serum proteins and c log P values, whereas a reasonable relationship was found with log D 7.4 values, but only when the two subclasses, acidic and zwitterionic congeners, were considered separately. The relationship between retention data on serum proteins and log P i.p. values indicated that the affinity for serum proteins depends on the lipophilicity of the neutral forms only for log P values up to 1.5. Above this value, protein retention does not further increase, becoming almost constant. Based on both the observations above reported and the small values of the slopes of regression equations, we conclude that the interaction of the more lipophilic quinolones, mainly the zwitterions, with serum proteins is not governed uniquely by lipophilicity but also by other mechanisms, probably of electrostatic nature.

Selenium speciation in Agaricus bisporus and Lentinula edodes mushroom proteins using multi-dimensional chromatography coupled to inductively coupled plasma mass spectrometry

In this study, selenium species from Se containing proteins in mushrooms ( Agaricus bisporus and Lentinula edodes) were investigated with size-exclusion liquid chromatography coupled to UV and inductively coupled plasma mass spectrometry (ICP-MS). Different protein extraction protocols were investigated. Variability of the fractionation patterns with three extraction media (0.1 M NaOH, 30 mM Tris–HCl, and enzymatic digestions) was evaluated for both mushroom types. A 24 h Tris–HCl extraction followed by acetone addition was found to be optimal for protein precipitation. Presumably protein bound selenoamino acids were released using enzymes (proteinase K, protease XIV and trypsin). The selenium speciation of the proteolytic extract of the water soluble proteins fraction was carried out by using reversed-phase ion-pairing high performance liquid chromatography (RP-HPIPC) coupled on-line to ICP-MS for selenium specific detection. Selenocystine, selenomethionine, methylselenocysteine and inorganic selenium were established in both samples utilizing retention time standards and standard additions to the sample.

Flow-injection in-line complexation for ion-pair reversed phase high performance liquid chromatography of some metal-4-(2-pyridylazo) resorcinol chelates

Flow injection (FI) was coupled to ion-pair reversed phase high performance liquid chromatography (IP-RPHPLC) for the simultaneous analysis of some metal-4-(2-pyridylazo) resorcinol (PAR) chelates. A simple reverse flow injection (rFI) set-up was used for in-line complexation of metal-PAR chelates prior to their separation by IP-RPHPLC. The rFI conditions were: injection volume of PAR 85 μL, flow rate of metal stream 4.5 mL min −1, concentration of PAR 1.8 × 10 −4 mol L −1 and the mixing coil length of 150 cm. IP-RPHPLC was carried out using a C 18 μBondapak column with the mobile phase containing 37% acetonitrile, 3.0 mmol L −1 acetate buffer pH 6.0 and 6.2 mmol L −1 tetrabutylammonium bromide (TBABr) at a flow rate of 1.0 mL min −1 and visible detection at 530 and 440 nm. The analysis cycle including in-line complexation and separation by IP-RPHPLC was 16 min, which able to separate Cr(VI) and the PAR chelates of Co(II), Ni(II) and Cu(II).

Analysis of saliva for glutathione and metabolically related thiols by liquid chromatography with ultraviolet detection

A method for simultaneous determination of glutathione and its precursors cysteine, cysteinylglycine and homocysteine in saliva is presented. The procedure involves reductive conversion of disulfides to thiols, derivatization to their 2-S-quinolinium derivatives with 2-chloro-1-methylquinolinium tetrafluoroborate and separation and quantitation by reversed-phase ion-pairing high performance liquid chromatography with ultraviolet detection at 355 nm. The calibration performed with saliva samples spiked with thiol disulfides, within the practical concentration ranges, showed linear response of the detector. The method applied to the saliva samples donated by volunteers showed mean concentration (SD, n = 8) of cysteine, cysteinylglycine, glutathione and homocysteine: 26.5 (31.6), 6.05 (5.12), 16.97 (7.68), 3.64 (1.34) nmol/ml respectively.

Comparison of a + T-Rich Oligonucleotides with and without Self-Complementary Sequence Using Ion-Pair Reversed-Phase High-Performance Liquid Chromatography/Tandem Electrospray Ionization Mass Spectrometry

Both A+T-rich oligonucleotides with and without self-complementary sequences were analyzed using ion- pair reversed-phase liquid chromatography/electrospray ionization mass spectrometry (IP-RP-HPLC/ESI-MS) by tryethylammonium acetate (TEAA) and hexafluoroisopropanol (HFIP) buffer systems to study the characteristics of their retention behavior and electrospray ionization tandem mass spectrometry (ESI-MS/MS) response. The results indicated that the chain length had the same effect on the retention of A+T-rich oligonucleotides in both of TEAA and HFIP buffer systems but the sequence had a different impact on the retention in the two buffer systems. A+T- rich oligonucleotides with a self-complementary sequence were much shorter than those without in the TEAA buffer system whereas a slight difference was observed in the HFIP buffer system. Similar total ion current (TIC) intensity was observed both in oligonucleotides with or without self-complementary sequence. The opposite trend of a change in the TIC intensities with increasing chain length were observed in both the TEAA and HFIP buffer systems. A lower charge state was predominant in the TEAA buffer system whereas a higher charge state was mainly distributed in the HFIP buffer system. The oligonucleotides without self-complementary sequences had a higher charge state than those with self-complementary sequences. A- and T- are more esily formed at a higher charge state whereas the sequence fragments will be formed more easily at a lower charge state in both A+T-rich oligonucleotides with and without self-complementary sequences.

Ion-pair reverse-phase high performance liquid chromatography method for determination of Huperzine-A in beagle dog serum

Huperzine-A (Hup-A), a biologically potent, reversible acetylcholinesterase inhibitor for the treatment of Alzheimer disease (AD) in China, has very low blood concentration. In order to study the pharmacokinetics of newly developed Hup-A transdermal patches in animal, a rapid and sensitive ion-pair reverse-phase high performance liquid chromatography (RP-HPLC) method for the determination of Hup-A in beagle dog serum using mebendazole as internal standard has been developed and validated. The analyte and internal standard were extracted from serum using chloroform–isopropanol (95:5, v/v), analyzed on a C (18) column (5 μm, 150 mm × 4.6 mm i.d.) with a mobile phase consisting of methanol–water–glacial acetic acid (50:48.5:1.5, v/v/v), using sodium dodecylsulfonate as an ion-pair reagent, and detected with UV detector at 313 nm. The chromatographic run time was within 15 min. The assay was linear over the concentration range of 1–12 ng/ml and intra- and inter-day precision over this range was not more than 12.8%. The limit of quantification in serum was 1 ng/ml. The method was successfully applied to characterize the Hup-A concentration–time profiles and study the single and multiple doses phamacokinetics of Hup-A transdermal patches in beagle dogs. The pharmacokinetic study results showed that Hup-A patches has the characteristic of sustained or controlled drug release in vivo.

Analysis of phosphorus herbicides by ion-pairing reversed-phase liquid chromatography coupled to inductively coupled plasma mass spectrometry with octapole reaction cell

A reversed phase ion-pairing high performance liquid chromatographic (RPIP-HPLC) method is developed for the separation of two phosphorus herbicides, Glufosinate and Glyphosate as well as Aminomethylphosphonic acid (AMPA), the major metabolite of Glyphosate. Tetrabutylammonium hydroxide is used as the ion-pairing reagent in conjunction with an ammonium acetate/acetic acid buffering system at pH 4.7. An inductively coupled plasma mass spectrometer (ICP-MS) is coupled to the chromatographic system to detect the herbicides at m/z 31P. Historically, phosphorus has been recognized as one of the elements difficult to analyze in argon plasma. This is due to its relatively high ionization potential (10.5 eV) as well as the inherent presence of the polyatomic interferences 14N16O1H+ and 15N16O+ overlapping its only isotope at m/z = 31. An octapole reaction cell is utilized to minimize the isobaric polyatomic interferences and to obtain the highest signal-to-background ratio. Detection limits were found to be in the low ppt range (25–32 ng/l). The developed method is successfully applied to the analysis of water samples collected from the Ohio River and spiked with a standard compounds at a level of 20 μg/l.