Non-suppressed Conductivity Detection Research Articles

Analytical Methods for Ionic Profile of Dialysate Iron Therapy Drug Ferric Pyrophosphate Citrate By Ion Chromatography using Suppressed and Non-Suppressed Conductivity Detection

In present study, ionic profile of pharmaceutical drug molecule ferric pyrophosphate citrate by ion exchange chromatography using conductivity detection was carried out. Ferric pyrophosphate citrate is an iron organic complex used for hemodialysis for the chronic kidney disease patients. The drug is used as iron supplementation to balance the iron loss during the dialysis for the kidney affected patients. Anions, cation and metal ion were analyzed by ion chromatographic method. Relevant anions sulphate, phosphate, citrate and pyrophosphate were analyzed by suppressed conductivity detection. Both isocratic and gradient separation methods were developed for the anions analysis. Cation sodium was analyzed by non-suppressed conductivity detection. Metal iron was determined by direct conductivity detection. All the analyses were done covering selectivity, precision, linearity and accuracy aspects of analysis. Calibration outcome of RSD 0.4 to 3.0% and correlation coefficient values greater than 0.999 were observed during the studies. Spiking studies were done to check the accuracy of the analysis and the recovery values ranging from 93 to 110% were observed. Around 90% ionic content of the drug molecule can be characterized using the developed ion chromatographic methods. These methods can be directly applied for the routine analysis of drug in the pharmaceutical industries.

A new approach to ion exchange chromatography with conductivity detection for adulterants investigation in dietary supplements.

The extent of adulteration of dietary supplements has significantly increased in recent years. This situation worries health authorities and requires auxiliary analytical tools for the investigation of illegal substances purposely added. Ion exchange chromatography with conductivity detection is a consolidated analytical technique for the determination of inorganic compounds in various matrices. This technique has been applied to the pharmaceutical characterization of mainly impurities and degradation products. This work presents a new approach to ion exchange chromatography as a screening method to investigate the presence of amfepramone, femproporex, sibutramine, bisacodyl and amiloride in dietary supplements advertised for weight loss. The method was optimized and validated using a Metrosep C4 100/4.0 cation exchange column. The mobile phase consisted of 1.8 mm HNO3 containing 2% acetonitrile (v/v), with a flow rate of 0.9 ml min-1 , and nonsuppressed conductivity detection was applied. The limits of detection and quantification varied from 1.01 to 3.62 mg L-1 and from 1.48 to 8.72 mg L-1 , respectively. The proposed method was successful applied to 78 solid dietary supplement samples, in two of which adulterations were found. Moreover, ion exchange chromatography with conductivity detection could be easily used for quality control without prior complex sample pre-treatment.

Determination of N-Carbamoylglutamate in Rumen Fluid

N-carbamoylglutamate (NCG) is a feed additives obtained synthetically from sodium glutamate,which is a structural analogue of N-acetylglutamate. Current study is aimed at developing ion chromatographic method for the determination of NCG in rumen fluid. Successful determination was performed on cation-exchange column and non-suppressed conductivity detection with total rune time of 11 minutes. Simple one-step cleanup using anion exchange cartridge was used to remove interfering compounds. Method was applied to determine NCG in rumen fluid, which was obtained from three rumen fistulated dairy cows. Incubated NCG sample in rumen fluid was assessed at various time intervals (0, 2, 4, 6, 12 and 24 h at 39 oC). Results showed that NCG was disappeared at the rate of 7.8, 12.8, 13.3, 14.2, and 17.8 % at 2, 4, 6, 12 and 24 h, respectively. It is concluded from the results that the procedure is quick and uncomplicated. NCG can be detected in rumen fluid without lengthy separation using cation-exchange chromatography. This technique can be applied for determination of NCG in rumen fluid as well as for practical use in animals feed.

Simple determination of betaine, l-carnitine and choline in human urine using self-packed column and column-switching ion chromatography with nonsuppressed conductivity detection.

A sequential online extraction, clean-up and separation system for the determination of betaine, l-carnitine and choline in human urine using column-switching ion chromatography with nonsuppressed conductivity detection was developed in this work. A self-packed pretreatment column (50 × 4.6 mm, i.d.) was used for the extraction and clean-up of betaine, l-carnitine and choline. The separation was achieved using self-packed cationic exchange column (150 × 4.6 mm, i.d.), followed by nonsuppressed conductivity detection. Under optimized experimental conditions, the developed method presented good analytical performance, with excellent linearity in the range of 0.60-100 μg mL-1 for betaine, 0.75-100 μg mL-1 for l-carnitine and 0.50-100 μg mL-1 for choline, with all correlation coefficients (R2 ) >0.99 in urine. The limits of detection were 0.15 μg mL-1 for betaine, 0.20 μg mL-1 for l-carnitine and 0.09 μg mL-1 for choline. The intra- and inter-day accuracy and precision for all quality controls were within ±10.32 and ±9.05%, respectively. Satisfactory recovery was observed between 92.8 and 102.0%. The validated method was successfully applied to the detection of urinary samples from 10 healthy people. The values detected in human urine using the proposed method showed good agreement with the measurement reported previously.

Determination of betaine, l-carnitine, and choline in human urine using a self-packed column and column-switching ion chromatography with nonsuppressed conductivity detection.

A simple method for the determination of betaine, l-carnitine, and choline in human urine was developed based on column-switching ion chromatography coupled with nonsuppressed conductivity detection by using a self-packed column. A pretreatment column (50mm × 4.6mm, id) packed with poly(glycidyl methacrylate-divinylbenzene) microspheres was used for the extraction and cleanup of analytes. Chromatographic separation was achieved within 10min on a cationic exchange column (150mm × 4.6mm, id) using maleic anhydride modified poly(glycidyl methacrylate-divinylbenzene) as the particles for packing. The detection was performed by ion chromatography with nonsuppressed conductivity detection. Parameters including column-switching time, eluent type, flow rates of eluent, and interfering effects were optimized. Linearity (r2 ≥ 0.99) was obtained for the concentration range of 0.50-100, 0.75-100, and 0.25-100 μg/mL for betaine, l-carnitine, and choline, respectively. Detection limits were 0.12, 0.20, and 0.05 μg/mL for betaine, l-carnitine, and choline, respectively. The intra- and interday accuracy and precision for all quality controls were within ±10.11%. Satisfactory recovery was observed between 92.5 and 105.0%. The validated method was successfully applied for the determination of betaine, l-carnitine, and choline in urine samples from healthy people.

A rapid ion chromatography column-switching method for online sample pretreatment and determination ofl-carnitine, choline and mineral ions in milk and powdered infant formula

A simple and rapid column-switching ion chromatography with non-suppressed conductivity detection method was developed for simultaneous determination ofl-carnitine, choline and mineral ions in milk and powdered infant formula samples.

GROUNDWATER QUALITY STUDIES IN TWO TRANSYLVANIAN RURAL COMMUNITIES USING PARALLEL ION CHROMATOGRAPHY

Groundwater originating from two rural communities from Cluj and Bistrita Nasaud counties was analyzed using parallel ion chromatography, the focus being on major anions (chloride, nitrite, nitrate, phosphate and sulphate) and cations (potassium, sodium, ammonium, calcium and magnesium). These analytes were determined simultaneously using a Shimadzu two-channel instrument with non-suppressed conductivity detection, separations being carried out using an Allsep Anion 7u column and an Universal Cation 7u column. From the 17 investigated sampling sites (wells up to 20 m deep), four proved to have nitrate concentrations higher than the maximum allowed limit according to the Romanian Law of Water Quality (50 mg/L), ranging from 57.82 to 311.13 mg/L, while high levels of ammonium were detected in three sites (from 0.94 to 11.74 mg/L, compared with the 0.5 mg/L which is the maximum admitted level). Groundwater originating from Apahida (Cluj County) proved to be highly contaminated with inorganic ions, the major causes being the intensive agriculture applied in this area and the salifer layers. However, some highly contaminated sites were recorded also in Prundu Bargaului from Bistrita Nasaud County; the major cause here is the manure storage relatively close to the water wells. The proposed analysis method increases much the laboratory productivity by decreasing the sample preparation time and the analysis time, all analytes being determined simultaneously in one run; it is simple and rapid, having potential to be used in groundwater quality surveys in the purpose of correlating diffuse pollution inputs with changes in water quality.

Ion Chromatography of Tri-Substituted Imidazolium Ionic Liquid Cations: Method and Application for Octanol–Water Partition Coefficient (KOW) Determination

A method was developed for simultaneous determination of four trisubstituted imidazolium ionic liquid cations (1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl-2,3-dimethylimidazolium) by ion chromatography using a carboxylic acid cation exchanger bonded to a silica-based column and direct (nonsuppressed) conductivity detection. The effects of the type of eluents, organic acid concentration, acetonitrile volume fraction, and column temperature on the cations retention were investigated. The optimal conditions for the method were 5 mmol L−1 methanesulfonic acid +10% acetonitrile as an eluent, 1.0 mL min−1 flow rate, and a column temperature of 30°C. The detection limit (S/N = 3) were 0.82–2.39 mg L−1 for the cations. The method was validated, accurate, and reproducible. This method was successfully applied to determine trisubstituted imidazolium ionic liquid cations in spiked tap water. The octanol–water partition coefficients (Kow) of these four trisubstituted imidazole substances were also reported in this study.

Anion separations for liquid chromatography using propylpyridinium silica as the stationary phase

This work describes the characterization and potential applications of a silica-based anion-exchange phase prepared by a two-step modification process that incorporates a propylpyridinium group. The effects of pH and eluent concentration on anion separation were examined using 150mm×3.9mm HPLC columns packed with the new phase. The mobile phase pH values ranged from 3.8 to 6.6 using phthalic acid/Tris solutions. The best separation was achieved using 2.5mmolL−1 phthalate/2.4mmolL−1 Tris solution at pH 4.2 as mobile phase with non-suppressed conductivity detection. The new stationary phase was used for the separation of some inorganic and organic anions showing good resolution. The stability of the silica-based anion exchange phase was also evaluated.Analytical curves, for concentrations ranging from 0.25 to 10mgL−1 for the inorganic anions chloride, nitrite, bromide and nitrate, showed good linear correlations (r>0.998). The method was tested with certified rainwater samples. The measured and certified values were in good agreement, indicating that the new phase holds significant promise for the analysis of these anions in environmental samples.

Simultaneous determination of alkali, alkaline earth and transition metal elements in uranium and thorium based nuclear fuel materials by single column ion chromatography

A single-column ion chromatography (SCIC) for the simultaneous determination of alkali, alkaline earth and transition metal elements in UO2, ThO2 powders and sintered (Th, U) O2 pellet is described in this paper. Metrosep cation 1-2 analytical column containing poly butadiene-maleic acid (PBDMA) coated silica has been applied to the ion chromatographic separation of 12 cations (copper, lithium, sodium, ammonium, nickel, potassium, zinc, cobalt, manganese, magnesium, calcium and strontium) using an isocratic elution with tartaric acid and oxalic acid as mobile phase with non-suppressed conductivity detection. Mobile phase composition was optimized to 1 mM tartaric acid and 0.75 mM oxalic acid for the baseline separation of 12 cations. The calibration plots were linear in the range of 0.05–40 mg L−1 with regression coefficients better than 0.998. The relative standard deviations (RSDs) of the retention time, peak area and peak height were less than 1, 2.8 and 3.0%, respectively. The recoveries of the spiked samples for the cations were 94–110%. The method developed was validated by comparison with certified standards of UO2 and ThO2 powders.

Determination of methylamines and trimethylamine- N-oxide in particulate matter by non-suppressed ion chromatography

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of methylamines (methylamine, dimethylamine, trimethylamine) and trimethylamine- N-oxide in particulate matter air samples. The analytes were well separated by means of cation-exchange chromatography using a 3 mM nitric acid/3.5% acetonitrile (v/v) eluent solution and a Metrosep C 2 250 (250 mm × 4 mm i.d.) separation column. The effects of the different chromatographic parameters on the separation were also investigated. Detection limits of methylamine, dimethylamine, trimethylamine, and trimethylamine- N-oxide were 43, 46, 76 and 72 μg/L, respectively. The relative standard deviations of the retention times were between 0.42% and 1.14% while the recoveries were between 78.8% and 88.3%. The method is suitable for determining if methylamines and trimethylamine- N-oxide are a significant component of organic nitrogen aerosol in areas with high concentration of these species.

Ion Chromatographic Determination of Residual Phase Transfer Catalyst in Active Pharmaceutical Ingredient

A new ion chromatography method with non-suppressed conductivity detection has been developed for the quantification of residual phase transfer catalyst-tetrabutylammonium bromide (TBAB) in an active pharmaceutical drug, Levetiracetam. Separation conditions are optimized to get a clear separation of TBAB from drug impurities using a Metrosep Cation C2-150 column. Conditions are also optimized to separate tetramethylammonium bromide, tetraethylammonium bromide, and tetrapropylammonium bromide, which are also used as phase transfer catalysts in several syntheses. Method performance was checked for selectivity, linearity, limit of quantification, limit of detection, accuracy, and precision. The method has superior performance with linearity r(2) > or = 0.9999, recovery from 94.7% to 96.5%, precision < or = 0.74%. In-line preconcentration is used to achieve limits of detection and quantification of 39 ng and 118 ng of TBAB, which corresponds to 1.56 and 4.72 microg/g of TBAB with respect to sample weight. The proposed method can be used for routine quality assurance analysis in the pharmaceutical industry.

Simultaneous determination of dimethylamine, trimethylamine and trimethylamine- n-oxide in aquatic products extracts by ion chromatography with non-suppressed conductivity detection

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of dimethylamine (DMA), trimethylamine (TMA) and trimethylamine- n-oxide (TMAO) in aquatic products. They were separated by means of cation-exchange chromatography using a 3.0 mmol/L methanesulfonic acid solution as eluent and an IonPac CS17 column (250 mm × 4 mm i.d.) as the separation column. Detection limits of dimethylamine, trimethylamine and trimethylamine- n-oxide were 0.06, 0.08 and 0.10 mg/L, respectively. The relative standard deviations (RSDs) of peak area were less than 3.53%. The recoveries were between 93.7% and 104.1%. Unlike traditional methods, this validated method is inexpensive and stable.

Long‐chain alkylimidazolium ionic liquids, a new class of cationic surfactants coated on ODS columns for anion‐exchange chromatography

Separations of common inorganic anions were carried out on ODS columns coated with two long-chain alkylimidazolium ionic liquids ([C(12)MIm]Br and [C(14)MIm]Br) as new cationic surfactants for ion chromatography. With phthalate buffer solution as the mobile phases and non-suppressed conductivity detection, high column efficiencies and excellent selectivity were obtained in the separation of inorganic anions. Chromatographic parameters are calculated and the results show that the coated column possesses significant potential for the analysis of some inorganic anions such as CH(3)COO(-), IO(3)(-), Cl(-), BrO(3)(-), NO(2)(-), Br(-), NO(3)(-), SO(4)(2-), I(-), BF(4)(-), and SCN(-). The effect of eluent pH values on the separation of anions has been studied on the column coated with [C(12)MIm]Br. The stability of the coated columns was also examined.

Determination of betaine, choline and trimethylamine in feed additive by ion-exchange liquid chromatography/non-suppressed conductivity detection

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of betaine, choline and trimethylamine in feed additive. The analytes and the common inorganic cations were well separated by means of cation-exchange chromatography using a 4.5 mmol/L methanesulfonic acid solution containing 10% (v/v) acetonitrile as eluent and an IonPac SCS1 column (250 mm × 4 mm i.d.) as the separation column. The effects of the different chromatographic parameters on the separation were also investigated. Detection limits of betaine, choline and trimethylamine were 0.076, 0.044 and 0.041 mg/L. The relative standard deviations (RSDs) of the retention time and peak area were less than 0.30% and 0.88%, respectively. The recoveries were between 93.2% and 112.6%. The method is suitable for use as a routine method in production quality control of feed additive.

New stationary phase for anion-exchange chromatography

This work describes the preparation of an anion-exchange phase based on silica, using a two-step modification process. First, 10 μm Davisil silica particles were silanized with chloropropyltrimethoxysilane to yield chloropropyl silica. The modified silica was then reacted with pyridine to produce positively charged propylpyridinium groups on the surface, the anion-exchange sites. The phase was characterized by thermogravimetric analysis and infrared and solid state 13C and 29Si NMR spectroscopies. HPLC separations of common inorganic anions, including chloride, nitrite, bromide and nitrate, were performed using 150 × 3.9 HPLC columns packed with the phase, using a phthalate buffer solution as mobile phase with non-suppressed conductivity detection. Efficiency and resolution were calculated and the results show that the new phase has significant promise for the analysis of these anions in environmental samples.

Early milestones in the development of ion-exchange chromatography: a personal account

Ion chromatography as we know it today was built on a foundation of knowledge accumulated over a period of many years. Here, we review some of the outstanding earlier achievements in ion-exchange chromatography. Beginning about 1947, Spedding and Powell at Iowa State published a series of papers describing practical methods for preparative separation of the rare earths by displacement ion-exchange chromatography. The same group then demonstrated the ion-exchange separation of 14N and 15N isotopes in ammonia. Beginning in the 1950s, Kraus and Nelson at Oak Ridge published numerous analytical methods for metal ions based on separation of their chloride, fluoride, nitrate or sulfate complexes by anion chromatography. In the period from about 1960 to 1980 many clever chromatographic methods for metal ion separations were reported by researchers throughout the world and automatic in-line detection was gradually introduced. A truly innovative method by Small, Stevens and Bauman at Dow Chemical Co. marked the birth of modern ion chromatography. Anions, as well as cations, could now be separated quickly and conveniently by a system of suppressed conductivity detection. A method for anion chromatography with non-suppressed conductivity detection was published by Gjerde et al. in 1979. This was followed by a similar method for cation chromatography in 1980. Ion chromatography as we know it today did not just happen. It was built on a solid foundation of knowledge that has accumulated over a period of many years. Revisiting the older ion-exchange chromatography serves not only to pay tribute to some remarkable accomplishments, but it can also be a learning experience. Trends and ideas in science tend to run in repeating cycles. Thus, an awareness of older work may provide inspiration for new research using improved contemporary technology. Selection of milestones is a rather personal matter. I chose to write about subjects of which I came to have a firsthand knowledge during my career. The topics selected are in roughly chronological order and cover the period from about 1945 to 1980. An effort has been made to explain the chemical principles as well as to recount the major accomplishments of the various research projects.

Ion chromatography on chelating stationary phases: separation of alkali metals

Analytical 250×4.6 mm I.D. columns packed with iminodiacetic acid (IDA) derivatised silica were used to separate alkali metal ions and the ammonium ion in combination with non-suppressed conductivity detection. The addition of 2.5–10 mmol/l of the macrocyclic crown ether 18-crown-6 to the nitric acid eluent resulted in a change in the elution order and a significant improvement in the resolution between potassium and ammonium because of selective complexation of potassium. However, the admixture of 15-crown-5 did not improve the resolution of lithium and sodium, although 15-crown-5 is a selective complexing agent for sodium. Retention and resolution of lithium, sodium, ammonium, cesium, rubidium and potassium ions increased at lower temperatures down to 1°C. The simultaneous separation of alkali and transition metals under isocratic conditions was achieved with an eluent comprising 10 mmol/l 18-crown-6, 1.5 mmol/l dipicolinic acid, and 1.9 mmol/l nitric acid. The chromatographic system enabled the quantitation of alkali metal ions with detection limits in the low ppb range and excellent linearity. Finally, the applicability of the method was approved by quantitation of sodium, ammonium and potassium in different water samples.

Ion-pair reversed phase liquid chromatography-indirect conductivity detection and response deviations of underivatised amino acids

Pairing chromatography is coupled with non-suppressed conductivity detection for the analysis of underivatised amino acids. The use of low concentrations of strong acids (perfluorinated carboxylic acids) as ion pairing reagents permitted indirect conductivity detection of the amino acids due to the high difference in the limiting equivalent ionic conductance between the hydrogen cation of the mobile phase and the ammonium cation of amino acids. A main system peak was induced after equilibrium perturbation. Its retention time and peak area were linearly related to the amount of ion pairing reagent adsorbed on the stationary phase and its concentration in the mobile phase, respectively. Amino acid response deviations relative to the baseline depended on their apparent charge and their elution in comparison to the elution of the main system peak. The choice of the optimum chromatographic conditions was a compromise between amino acid sensitivity, chromatographic separation, and stability of the system (minimum number of system peaks). An industrial fermentation product containing glutamic acid in excess (100–1 000 times more than the other amino acids) is used as a real application. The conductivity response of glutamic acid was almost annihilated by operating with a mobile phase pH close to the isoelectric point of Glu, leading to the successful determination of closely eluted minority amino acids. Linear calibration curves (0.9979 < r 2 < 0.9992) are obtained for two orders of magnitude with good relative standard deviations for peak areas (0.76–1.63%) and retention time (0.06–0.12%). Limits of detection are evaluated from 20 to 50 ng of injected amount (using a 10 μL loop) depending on the amino acid.

Simultaneous ion-exclusion chromatography and cation-exchange chromatography of anions and cations in environmental water samples on a weakly acidic cation-exchange resin by elution with pyridine-2,6-dicarboxylic acid.

A non-suppressed conductivity detection ion chromatographic method using a weakly acidic cation-exchange column (Tosoh TSKgel OApak-A) was developed for the simultaneous separation and determination of common inorganic anions (Cl-, NO3- and SO4(2-)) and cations (Na+, NH4+, K+, Mg2+ and Ca2+). A satisfactory separation of these anions and cations on the weakly acidic cation-exchange column was achieved in 25 min by elution with a mixture of 1.6 mmol L-1 pyridine-2,6-dicarboxylic acid and 8.0 mmol L-1 18-crown-6 at flow rate of 1.0 mL min-1. On this weakly acidic cation-exchange resin, anions were retained by an ion-exclusion mechanism and cations by a cation-exchange mechanism. The linear range of the peak area calibration curves for all analytes were up to two orders of magnitude. The detection limits calculated at S/N = 3 ranged from 0.25 to 1.9 mumol L-1 for anions and cations. The ion-exclusion chromatography-cation-exchange chromatography method developed in this work was successfully applied to the simultaneous determination of major inorganic anions and cations in rainwater, tap water and snow water samples.