Aqueous Ammonium Acetate Research Articles

Determination of Organic Acids in Ground Water by Liquid Chromatography/Atmospheric Pressure Chemical Ionization/Mass Spectrometry

ABSTRACT Current methods of determining organic acids in ground water are labor-intensive, time-consuming and require a large volume of sample (100 milliliter to 1.0 liter). This paper reports a new method developed to determine aliphatic, alicyclic, and aromatic acids in ground water using liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry (LC/APCI/MS). This method was shown to be fast (less than 1 hour), effective, and reproducible, requiring only 1.0 mL of ground-water sample. Ground water was pH-adjusted, filtered through 0.45 μm filters and directly injected into the LC. A binary solvent system consisting of 40 mM of aqueous ammonium acetate and methanol and a C18 column were used for chromatographical separation. The APCI was operated under negative ionization mode. Selected ion monitoring (SIM) was used for detection and quantitation of the analytes. This method was applied to the analysis of organic acids in ground-water samples collected from an aquifer contaminated with JP-4 fuel hydrocarbons at Wurtsmith Air Force Base in Oscoda, Michigan. Aromatic acids identified in the contaminated ground water include o-, m-toluic acids (2- and 3-methylbenzoic acids), 2,6-dimethylbenzoic acid, 2,3,5- and 2,4,6-trimethylbenzoic acids and two additional trimethylbenzoic acids with unknown location of methylation. The detection of aromatic acids in groundwater from the KC-135 site provided evidence for in situ microbial degradation of hydrocarbons occurring in the aquifer.

Estimation of impurity profiles of drugs and related materials Part 18. Impurities and degradation products of mazipredone

Reversed-phase HPLC methods using C-18 and C-8 columns as well as various isocratic and gradient systems with aqueous ammonium acetate, methanol and acetonitrile are described for the separation of the impurities of mazipredone (11 β,17-dihydroxy-21-(4-methyl-1-piperazinyl)-pregna-1,4-diene-3,20-dione hydrochloride). These methods were used also for the estimation of the hydrolytic and oxidative degradation pathways of mazipredone in 0.1 M hydrochloric acid and sodium hydroxide at 80°C. With the aid of HPLC-(APCI)-MS and HPLC-diode-array UV techniques 15 impurities and degradation products have been identified.

Double column-switching high-performance liquid chromatographic method for the determination of TAK-603 and its metabolites in human serum

A double column-switching high-performance liquid chromatographic (HPLC) method for the determination of concentrations for TAK-603 (T) and its metabolites, T-72258 (M-I) and T-72294 (M-III), in human serum was developed. The analytes were extracted with ethyl acetate from human serum samples treated with triethylamine and injected into the HPLC system. Separation of the analytes was performed on the HPLC system with double column-switching technique. The mobile phases A and B for the first column and the mobile phase C for the second column used were a mixture of methanol–10 m M aqueous ammonium acetate solution (1:1, v/v), methanol and a mixture of methanol–10 m M aqueous ammonium acetate solution (11:9, v/v), respectively. The eluate was monitored with a UV detector at a wavelength of 253 nm. The work-up procedure was reproducible and more than 90% of the analytes could be recovered from human serum. The lower limits of quantitation were all 1 ng/ml for the analytes when 0.5 ml of human serum was used. Standard curves were linear with a correlation coefficient ( R) of more than 0.999 in the range of 1–500 ng/ml for T, M-I and M-III in human serum. The intra- and inter-day precision of the method for the various analytes were below 4.8%. The accuracy was good with the deviations between spiked and calculated concentrations of the analytes being within 11.0%. The method was successfully applied to analyze serum samples after an oral administration of T to healthy male volunteers.

Analysis of phosphorylated carbohydrates by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry utilising a β-cyclodextrin bonded stationary phase

Chromatographic separation of phosphorylated carbohydrates was achieved on a β-cyclodextrin (CD) bonded HPLC column. Applying acetonitrile–aqueous ammonium acetate gradient elution, the separation of sugar phosphates relied on the combination of anion-exchange and hydrophilic interaction properties of CD bonded phases in the presence of ammonium ions. Furthermore, this solvent system allowed on-line coupling to electrospray ionization mass spectrometry (ESI-MS) and direct structural characterisation of carbohydrate phosphates by tandem mass spectrometry (MS–MS). In addition to the analysis of various pentose and hexose phosphates, the HPLC–ESI-MS–MS method was successfully applied to demonstrate the enzymatic formation of D-1-deoxyxylulose 5-phosphate from pyruvate and glyceraldehyde phosphate catalysed by yeast transketolase.

Enantioselective HPLC Determination of R and S Trimipramine in Human Serum Using an Octyldecylsilane Column with β-Cyclodextrin as Mobile Phase Additive and Solid Phase Extraction

A stereospecific HPLC method was developed for the analysis of the enantiomers of trimipramine in human serum. The assay uses amitriptyline as the internal standard and a C18 solid phase extraction column for serum sample clean-up. It is free of interference from desmethyl-trimipramine, 2-hydroxy-desmethyl-trimipramine and 2-hydroxy-trimipramine, the three major metabolites of trimipramine. Recoveries of 98.8% and 97.5% were obtained for the R and S enantiomers of trimipramine, respectively. Resolution of the enantiomers was obtained using an octyldecylsilane column with β-cyclodextrin as the mobile phase additive. The composition of the mobile phase was 80:20 v/v aqueous 10mM ammonium acetate buffer pH 4 (adjusted with acetic acid)- absolute ethanol containing 20mM β-cyclodextrin at a flow rate of 0.7mL/min. Linear calibration curves were obtained in the 25-400ng/mL range for each enantiomer in serum. The detection limit based on a S/N = 3 was 10ng/mL for each enantiomer in serum with UV detection at 220nm. The limit of quantitation for each enantiomer was 25ng/mL. Precision calculated as %RSD and accuracy calculated as % error were in the range 0.7–4.5% and 0.9–3.1%, respectively, for the R enantiomer and 0.7–5.1% and 0.4–4.4% respectively, for the S enantiomer. Separation of the three major metabolites of trimipramine was also investigated.

Quantitative High-performance Liquid Chromatographic Analysis of Famotidine in Pharmaceutical Dosage Forms

A rapid and specific high-performance liquid chromatographic (HPLC) method has been developed for quantitative analysis of famotidine in pharmaceutical dosage forms. The method was applied to medicines on the Turkish market. A LiChrospher RP-18 column, HP-1050 UV-detector and methanol—0·1 M aqueous ammonium acetate (30 : 70) as the solvent system (flow rate 1·0 mL min−1) were used. Quantitative determination of famotidine was carried out at 254 nm wavelength. The method was found to be rapid—under 5 min per assay—and was selective enough to allow the determination of famotidine in the presence of certain excipients.

Identification of soyasaponins by liquid chromatography–thermospray mass spectrometry

Saponins are important bioactive molecules widespread in the plant kingdom. Soyasaponins, isolated from Glicine max (Leguminosae), have been shown to exhibit various biological activities, e.g., an inhibitory effect on lipid-oxidation and liver-lesion generation and an improving effect on hyper-cholesteremia. Mass spectral investigation of these metabolites requires soft ionization techniques such as desorption chemical ionization, fast atom bombardment and thermospray mass spectrometry. A high-performance liquid chromatographic method was developed for thermospray mass spectrometric analysis of saponins contained in soybean flour extracts. The analyses were performed using a ternary eluent (water–acetonitrile–methanol) in gradient conditions with post-column addition of aqueous ammonium acetate. Six saponin components could be separated and identified. The mass spectra obtained provided information concerning both molecular masses and aglycone composition.

Determination of Ceftazidime and Pyridine by HPLC: Application to a Viscous Eye Drop Formulation

Abstract A stability-indicating high performance liquid chromatographic (HPLC) method was developed to determine the cephalosporin antibiotic ceftazidime and its degradation product pyridine. The method was applied to analysis of an aseptically prepared viscous ceftazidime eye drop formulation (ceftazidime 5% w/v in Sno Tears). The chromatographic conditions were: Spherisorb 5μm hexyl column, 100 × 4.6mm; mobile phase acetonitrile:aqueous ammonium acetate 0.05M (7:93); flow rate 2ml/min; detector wavelength 254nm. The retention times of ceftazidime and pyridine were 1.3min and 3.8min respectively. The chromatographic precision of the method was typically 0.3–0.5% relative standard deviation (RSD) for ceftazidime. The recovery of ceftazidime from the eye drop was 101.3% and the within-day precision was 0.8% RSD. The limit of detection for pyridine was 2.4ng. Ceftazidime degraded by 7% over 7 days in the eye drops, with the production of pyridine accounting for 50% of the degraded antibiotic.

An improved high-performance liquid chromatography system for the analysis of basic dyes in forensic casework

Acrylic fibres are frequently encountered as physical evidence in casework in the Northern Ireland Forensic Science Laboratory. Separation and analysis of the basic dyes, used in the garment industry for the dyeing of acrylic fibres, was carried out by isocratyic HPLC with a narrow bore column. The HPLC eluent used was a mixture of methanol and aqueous ammonium acetate solution (pH 9.76) in a ratio of 9:1. The sensitivity of the system is such that the dyes extracted from 0.2 cm of a black acrylic fibre could be detected using three injections on a single channel detector at wavelengths of 400, 500 and 600 nm (for yellow, red and blue dye components respectively).

High-performance liquid chromatographic separation of nucleic acids on a fluorocarbon-bonded silica gel column

The separation of nucleic acids and related compounds was investigated using high-performance liquid chromatography on a new fluorocarbon-bonded silica gel column. The polyadenylate enzymic partial hydrolysate sample and a mixture of various polynucleotide samples were sufficiently separated in the reversed-phase mode using gradient elution with aqueous ammonium acetate—acetonitrile. A mixed-mode separation on the fluorinated phase coated with a tetraalkylammonium salt was also examined for the separation of various polynucleotides, including tRNAs.

Analysis of poppy straw and poppy straw concentrate by reversed‐phase high‐performance liquid chromatography

AbstractA method of reversed‐phase high‐performance liquid chromatography using an elution gradient has been developed to analyse morphine, codeine, thebaine, and oripavine — this last‐mentioned substance for the first time — in samples of poppy straw and poppy straw concentrate. Gradient elution of the octadecylsilane column was performed: the gradient was from 10 to 30% of solvent A (methanol) in solvent B (containing 67% of 0.5% aqueous ammonium acetate solution containing diethylamine, and 33% of methanol) over a 25 min period. The four alkaloids were identified and quantified with the aid of an internal standard.

Determination of serum creatinine by isotope dilution method using discharge-assisted thermospray liquid chromatography/mass spectrometry.

A discharge-assisted thermospray (plasmaspray) liquid chromatography/mass spectrometric method for the determination of serum creatinine is described. The method incorporates stable isotope dilution using (D3)creatinine as an internal standard. Separation is performed in reversed-phase high-performance liquid chromatography using 0.01 M aqueous ammonium acetate as a flow solvent. Effluents are directly introduced to the mass spectrometer and [MH]+ ions are monitored during LC/MS using the selected ion monitoring method. Satisfactory agreement between the analytical result and the certified value of the serum sample of standard reference material and relative standard deviation ranging from 0.6% to 1.2% was obtained.

Quantitative High Performance Liquid Chromatographic Determination of Bamipine Combined with Tricyclic Antidepressants and/or Antipsychotics in Pharmaceutical Formulations

Abstract An advanced reserved phase High Performance Liquid Chromatographic (HPLC) method using UV detection, at 251, is presented for the simultaneous determination of bamipine combined with tricyclic antidepressants and/or antipsychotics in various pharmaceutical formulations. Sample analyses were performed on a bonded reserved-phase C-2,5 μm, 250 × 4.6 mm ID (Lichrosorb RP-2)column using aqueous ammonium acetate at constant ionic strength 0.015 M and acetonitrile 35: 65 as eluent, at a flow rate of 0.9 ml/min. The pH was adjusted to 4.7 with acetic acid. The presence of acetate buffer both shortens the elution time and improves the symmetry of the chromatographic peaks. The retention time was for bamipine, prochlorperazine, trifluoperazine, thioridazine, chlorprothixene, haloperidol, clomipramine, trimipramine 8.83, 11.83, 11.50, 11.08, 10.42, 8.05, 10.25, 9.67 min respectively. Linearity and precision data have been assessed. The method also involves an investigation of the dependence of the capacity ratio k′ on the pH and the polarity of the mobile phase.

On-line low-level screening of polar pesticides in drinking and surface waters by liquid chromatography—thermospray mass spectrometry

Mass spectra of 39 carbamate, triazine, phenylurea and organophosphorus polar pesticides were obtained by liquid chromatography—mass spectrometry with a thermospray interface. The analytes generated [M + H] + or [M + NH 4] + as the base peak with methanol−0.1 M ammonium acetate as the mobile phase in the discharge positive-ion mode. Chlorophenols showed much better sensitivity in the negative-ion mode; their spectra were dominated by the deprotonated molecular ion. Trace enrichment of these pesticides on a 10 mm × 3.0 mm I.D. precolumn packed with C 18-bonded silica was coupled on-line with reversed-phase column liquid chromatography—thermospray mass spectrometry (LC-TSP-MS). The LC separation was carried out on a 250 × 4.6 mm I.D. C 18-bonded silica column using a linear methanol—aqueous ammonium acetate gradient [10:90 to 90:10 (v/v) in 45 min]. When optimized TSP-MS conditions and 50-ml water samples were used, the detection limits for the pollutants tested typically were in the 2–90 ng/l range with time-scheduled selected-ion monitoring; the repeatability was good and the LC-TSP-MS system was robust. Several surface and drinking water samples were analysed and low levels of simazine, atrazine, isoproturon and diuron were detected.

Determination of 1-(β- d-arabinofuranosyl)-5-(1-propynyl)-uracil and a metabolite, 5-propynyluracil, in plasma using ASTED (automated sequential trace enrichment of dialysates) combined, on-line, with high-performance liquid chromatography

A high-performance liquid chromatographic assay was developed for the determination of the potential antiviral drug 1-(β- d-arabinofuranosyl)-5-(1-propynyl)uracil (I) and a metabolite, 5-propynyluracil (II), in plasma. Plasma samples were mixed with monochloroacetic acid to reduce the effect of protein binding. The mixture was dialysed prior to concentration of analytes on an ODS cartridge followed by isocratic separation on an ODS analytical column using acetonitrile in aqueous ammonium acetate. Detection was by ultraviolet absorption. The quantifiable limit for both I and II is 0.2 μmol/l with a mean inter- and intra-assay precision of 1.3–2.5% (coefficient of variation).

Determination of trace aluminium by differential pulse adsorptive stripping voltammetry of aluminium(II) -8-hydroxyquinoline complex

A rapid and sensitive differential-pulse adsorptive stripping voltammetric method, based on the formation of an electroactive complex between aluminium(III) and 8-hydroxyquinoline (HOx), is presented for the determination of trace levels of aluminium. The complex showed an oxidative peak potential at +0.876 V vs. Ag/AgCl (saturated KCl) at a glassy carbon (GC) electrode in aqueous ammonium acetate (0.024 M, pH 6.8. A good linear relationship between the peak current and Al(III) concentration in the ranges 4.00 X 10 −8–5.00 X 10 −6 and 8.00 X 10 −6–4.00 X 10 −5 M were observed. In the lower Al(III) concentration region, the anodic peak was the result of the stripping of the absorbed Al(III)-HOx complex, whereas in the higher concentration range, the diffusional oxidation current of the solution species predominated. A surface saturation region was observed from 5.00 X 10 −6 to 8.00 X 10 −6 M Al(III). Relatively few interferences were found and these were easily masked. The detection limit for Al(III) for this method is 1.00 X 10 −8 M and ten determinations of Al(III) at 1.00 X 10 −7 M gave a relative standard deviation of 6.2%. The method was employed in the analysis of Al(III) in a US Environmental Protection Agency water pollution quality control sample (WP 386) and excellent agreement with the certified value was obtained.

High-performance liquid chromatographic analysis of sulfonated aromatics using a β-cyclodextrin-bonded phase

A cyclodextrin-bonded phase and methanol—aqueous ammonium acetate mobile phase were used in the liquid chromatographic analysis of a number of sulfon

Liquid chromatography/thermospray mass spectrometry of monosaccharides and their derivatives

Thermospray (TSP) mass spectrometry has proved to be a useful technique for analysing various highly polar compounds. The use of a quadrupole mass spectrometer equipped with a thermospray/plasmaspray interface in the analysis of more than 30 monosaccharides and sugar derivatives is described. A 1:1 mixture of methanol or acetonitrile and 0.1 M aqueous ammonium acetate as eluent at 1 cm3 min−1 affords the best results. The correct setting of the capillary tip temperature and repeller voltage was fundamental for the ionization of carbohydrates. The/optimum values of these parameters were 240–250°C and 220–240 V, respectively. The thermospray mass spectra of most carbohydrates exhibit strong [M + NH4]+ ions which provide molecular mass information. The underivatized and derivatized monosaccharides could be grouped according to the presence or absence and the relative abundances of [M + NH4 − H2O]+, [M + H]+ and [M + NH4]+ ions.

Rapid high-performance liquid chromatographic determination of urinary N-(1-methylethyl)-N′-phenyl-1,4-benzenediamine in workers exposed to aromatic amines

A procedure has been developed for determining N-(1-methylethyl)-N′-phenyl-1,4-benzenediamine in urine by using high-performance liquid chromatography. The method uses chloroform extraction for partial clean-up of the urine sample. The separation is carried out on a reversed-phase column using 65 mmol/l aqueous ammonium acetate in acetonitrile (30:70, v/v) as the mobile phase. The column effluent is monitored at 290 nm with an ultraviolet detector. The analyte is separated from other normal urine constituents in less than 4 min. Peak height and concentration are linearly related. Coefficients of variation assessed for within-day reproducibility were 5.9 and 3.7% at concentrations of 22.3 and 92.1 μg/l, respectively. The mean analytical recovery from urine samples spiked with known amounts of amine was 89.7 ± 6.8%. The request of only a small volume of urine and the simple pre-treatment procedure makes it suitable for the routine monitoring of the exposure of rubber vulcanization workers to aromatic amines.

A Simultaneous Analysis by High Performance Liquid Chromatography of Bamipine Combined with Tricyclic Antidepressants and/or Antipsychotics in Dosage Forms

Abstract A reversed phase high-performance liquid chromatographic method is described for the simultaneous determination of antihistamines, tricyclic antidepressants and anti-psychotics in pharmaceutical formulations and in spiked placebos. The separation was performed on an octadecyl-silica column using acetonitrile: tetrahydrofuran: 0.015 M aqueous ammonium acetate (53:42: 5) as mobile phase. The presence of ammonium acetate both shortens the elution time and improves the symmetry of the chromatographic peaks. Measurements were made at 251 nm.