Evaporation Of Acetonitrile Research Articles

Determination of Novel Highly Effective Necrostatin Nec-1s in Rat Plasma by High Performance Liquid Chromatography Hyphenated with Quadrupole-Time-of-Flight Mass Spectrometry.

Necrostatins have been shown to retard necroptosis, a programmed necrotic-like cell death, which has been shown to underlie pathophysiology of various diseases. Nec-1s, a novel highly effective necrostatin, overcomes some drawbacks of former necrostatin analogues. The determination of Nec-1s in biological system, however, has not been carried out so far. Therefore, this study was undertaken to optimize and validate the HPLC-DAD-Q-TOF method for the assessment of Nec-1s levels in the plasma what is the necessity for designing its proper dosing regimen for in vivo studies. Benefits of the proposed analytical protocol include: (i) simple sample preparation (precipitation of plasma proteins, evaporation of acetonitrile, reconstitution in mobile phase), (ii) fast, selective and sensitive analysis due to a highly orthogonal LC-MS system providing less than 8 min analysis time, (iii) detection of Nec-1s without any matrix interferences, and quantitation of very low concentration levels of Nec-1s (LLOQ ~ 20 ng/mL), (iv) high reliability of Nec-1s determination with precision and accuracy values meeting the FDA criteria for biomedical analysis. The proposed analytical protocol is suitable for routine use in relevant biological studies, and, in this work, it was successfully applied for monitoring of Nec-1s plasma levels in rats providing reproducible and consistent results. Based on pharmacokinetic features, which can also be assessed due to the results of this study, there will be efforts to perform both acute and chronic in vivo studies and potential clinical safety studies first.

Quantitation of low concentrations of polysorbates in high protein concentration formulations by solid phase extraction and cobalt-thiocyanate derivatization

A spectrophotometric method was developed to quantify low polysorbate (PS) levels in biopharmaceutical formulations containing high protein concentrations. In the method, Oasis HLB solid phase extraction (SPE) cartridge was used to extract PS from high protein concentration formulations. After loading a sample, the cartridge was washed with 4M guanidine HCl and 10% (v/v) methanol, and the retained PS was eluted by acetonitrile. Following the evaporation of acetonitrile, aqueous cobalt-thiocyanate reagent was added to react with the polyoxyethylene oxide chain of polysorbates to form a blue colored PS–cobaltothiocyante complex. This colored complex was then extracted into methylene chloride and measured spectrophotometrically at 620nm. The method performance was evaluated on three products containing 30–40mgL−1 PS-20 and PS-80 in ≤70gL−1 protein formulations. The method was specific (no matrix interference identified in three types of protein formulations), sensitive (quantitation limit of 10mgL−1 PS) and robust with good precision (relative standard deviation ≤6.4%) and accuracy (spike recoveries from 95% to 101%). The linear range of the method for both PS-20 and PS-80 was 10 to 80mgL−1 PS. By diluting samples with 6M guanidine HCl and/or using different methylene chloride volumes to extract the colored complexes of standards and samples, the method could accurately and precisely quantify 40mgL−1 PS in up to 300gL−1 protein formulations.

Nanosolvation by acetonitrile and 18-crown-6 ether induce strongly different effects on the electron-capture induced dissociation of aromatic tripeptide cations in the gas phase

Experimental gas-phase Electron Capture-Induced Dissociation (ECID) coupled to mass-spectrometry has been performed on the doubly-protonated tripeptides Lys-Trp-Lys (KWK) and Lys-Tyr-Lys (KYK). In this report, we focus on the influence of non-covalent binding of two different molecules, acetonitrile and 18-crown-6 ether (CE), to these tripeptide cations on the relative probabilities of their main fragmentation channels (H loss, NH3 loss and NCα bond cleavage) after electron capture from sodium atoms. First, we recorded the spectra of bare peptide ions, and found that NCα bond cleavage leads to fragments containing the aromatic amino acid. The structures and energies of the low-lying conformers of the tripeptide dications and radical monocations obtained from our DFT and MP2 calculations are in line with this observation. Second, the ECID spectra of KWK and KYK dications nanosolvated by one and two molecules show that acetonitrile evaporation is almost complete a few microseconds after electron capture, whereas fragments nanosolvated by CE are abundant. This is consistent with the binding energy of these molecules to lysine-containing peptides, which is much higher for CE than for acetonitrile. One or two acetonitrile molecules have also been found to induce little effect on the fragmentation patterns of the charge-reduced peptide ions. By contrast, one or two CE decreases the NH3-loss probability, which is accounted for by the inhibition of this channel upon CE binding to the N-terminal ammonium group. Besides, this experimental result is consistent with our DFT calculations, which suggest a lower abundance of N terminally-protonated [KWK+2H]2+(CE)2 compared to bare tripeptide cations. Extracting the H-loss contribution from ECID data had never been done for tripeptides nanosolvated by CE. This allowed us to observe the enhancement of H loss from KWK and KYK nanosolvated by two CE, but surprisingly, not by one. This peculiar behavior might be due to H transfer from the reduced radical NH3 group to CE, followed by loss of the [CE+H] radical.

Robust polyazobenzene microcapsules with photoresponsive pore channels and tunable release profiles

Monodisperse silica particles coated with azobenzene polymer (PAzo) shell were synthesized through distillation precipitation polymerization. Robust PAzo microcapsules were obtained after selective removal of the silica templates by hydrofluoric acid (HF) etching. These PAzo microcapsules, confirmed by transmission electron microscopy (TEM) investigation, had excellent reversible photoisomerization with transformation between trans and cis isomers under ultraviolet (UV) and visible lights. Due to their compatibility with PAzo, acetonitrile would be trapped in the network of the shell during polymerization. Pore channels in the shell, confirmed by nitrogen adsorption–desorption test, would be produced after acetonitrile evaporation. Loading and release of rhodamine B (RhB) molecules in PAzo microcapsules were carried out and indicated that cis azobenzene showed larger pore diameter (named as “open switch”) under UV light which favored permeation of RhB molecules, while trans structure (named as “closed switch”) under visible light slowed down the process. In addition, both release profiles obeyed pure Fickian diffusion with a power law of t 0.42. Diffusion coefficient of RhB from PAzo microcapsules under visible light (1.47 × 10 −12 cm 2/s) was lower than that under UV light (2.12 × 10 −12 cm 2/s).

On-Column Solvent Exchange for Purified Preparative Fractions

On-column solvent exchange, using many of the principles of solid-phase extraction, has been implemented to significantly reduce evaporation cycle time following reverse-phase preparative HPLC. Additional benefits, such as a reduced potential for salt formation, thermal decomposition, and residual solvent, are also described. Fractions obtained from preparative separations, typically in a large volume of acetonitrile:water, are injected into the preparative HPLC and then eluted in acetonitrile, creating a new fraction in a volatile organic solvent. Minimal modification to the instrument was required, and unattended operation is possible. Acetonitrile evaporation is achieved within 3 h, compared with 17 h for aqueous-based fractions; lower temperatures can be used during the evaporation step; mobile-phase additives, likely to form salts with the target compound if concentrated in the fraction, are removed before evaporation; sample recovery and purity are unaffected.

Simple, high throughput ultra-high performance liquid chromatography/tandem mass spectrometry trace analysis of perfluorinated alkylated substances in food of animal origin: Milk and fish

The present study documents development and validation of a novel approach for determination of 23 perfluorinated alkylated substances (PFASs) in food of animal origin represented by milk and fish. The list of target analytes comprises four classes of PFASs, both ionic and non-ionic: 11 perfluorocarboxylic acids (PFCAs), 4 perfluorosulphonic acids (PFSAs), 5 perfluorosulphonamides (FOSAs) and 3 perfluorophosphonic acids (PFPAs). Fast sample preparation procedure is based on an extraction of target analytes with acetonitrile (MeCN) and their transfer (supported by inorganic salts and acidification) into the organic phase. Removing of matrix co-extracts by a simple dispersive solid phase extraction (SPE) employing ENVI-Carb and C18 sorbents is followed by an efficient sample pre-concentration performed by acetonitrile evaporation and subsequent dilution of residue in a small volume of methanol (matrix equivalent in the final extracts was 16 and 8 g mL −1, for milk and fish respectively). Using modern instrumentation consisting of ultra-high performance liquid chromatography (UHPLC) hyphenated with a tandem mass spectrometer (MS/MS), limits of quantification (LOQs) as low as 0.001–0.006 μg kg −1 for milk and 0.002–0.013 μg kg −1 for fish can be achieved. Under these conditions, a wide spectrum of PFASs, including minor representatives, can be determined which enables collecting data required for human exposure studies. The pilot study employing the new method for examination of milk and canned fish samples was realized. Whereas in majority of canned fish products a wide spectrum of PFCAs, perfluorooctanesulphonic acid (PFOS) and perfluoro-1-octanesulphonamide (PFOSA) was detected, only in a few milk samples very low concentrations (LOQ levels) of PFOS and perfluorooctansulphonic acid (PFDS) were found.

Rapid method for the determination of tranquilizers and a beta-blocker in porcine and bovine kidney by liquid chromatography with tandem mass spectrometry

A fast and simple liquid chromatography with tandem mass spectrometry method for detection and confirmation of tranquilizers (chlorpromazine, propionylpromazine, acepromazine, triflupromazine, promazine, azaperone and its metabolite, azaperol) and beta-blocker (carazolol) in porcine and bovine kidney has been presented. The method relies on the extraction with acetonitrile followed by centrifugation. After evaporation of acetonitrile, the residue was reconstituted in a mobile phase and filtrated. The separation of analytes was performed on a C18 column using a mobile phase of acetonitrile and ammonium formate buffer (0.05 M, pH 4.5) with gradient elution. The electrospray ionization was used to obtain the protonated molecules [M+H] + and two product ions were monitored for each compound. For quantification deutered internal standards were used. The whole method has been validated according to the European Union requirements. Specificity, decision limit (CCα), detection capability (CCβ), trueness and precision were determined. The results showed good trueness ranged from 73.2% to 110.6% with a good R.S.D., less than 13.0% under within-laboratory reproducibility conditions. The calculated critical concentrations of CCα for phenothiazines were between 5.8 and 6.6 μg kg −1 while for azaperone CCα was 105.5 μg kg −1 and for azaperol was 121.4 μg kg −1. CCα for carazolol was 16.7 μg kg −1 in bovine and 21.9 μg kg −1 in porcine kidney. CCβ for phenothiazines were between 6.3 and 7.6 μg kg −1, for azaperone was 119.0 μg kg −1 and for azaperol was 140.0 μg kg −1. For carazolol in bovine kidney CCβ was 18.6 μg kg −1 whereas in porcine kidney was 24.4 μg kg −1.

Electroosmotic flow variations caused by the volatility of buffer components: diagnosis and therapy.

In order to separate a polar amine pharmaceutical and its potential impurities, a micellar electrokinetic chromatography method was developed. The main compound and 11 other substances were completely separated using a 20 mM Tris buffer, pH 8.0, containing 50 mM sodium dodecylsulfate (SDS) and 24% (v/v) acetonitrile. However, a strong, continuous reduction in the EOF occurred and quantification was not possible. The EOF reproducibility could not be improved by suitable rinsing procedures. Surface effects or interactions did not cause the EOF changes, but the evaporation of acetonitrile was identified as the major source for EOF instability. However, a high concentration of acetonitrile was decisive for selectivity. Thus a reliable protection against the evaporation of this buffer constituent had to be found. Paraffin and various silicon oils were tested as covering film. In order to quickly test buffer systems if the evaporation of electrophoresis solutions is acceptable, an alternative experimental design without doing CE experiments had to be found. Electrical conductivity was chosen as parameter, because it can be determined simply and fast. The buffers under investigation were placed in a 50-ml beaker with a magnetic stirring rod, placed on a magnetic stirrer. The buffer solution was kept in motion at 120 rev./min. The beaker was covered around the measuring head with laboratory film and in addition to this with paraffin or silicon oil. An acetonitrile content up to 10% (v/v) was acceptable if a coverage was used. The various cover liquids had a similar effect. A content of 15% (v/v) already increased the evaporation effect significantly. Higher acetonitrile contents are not acceptable. A buffer similar to the originally transferred method, 20 mM Tris (pH 8.0), 50 mM SDS containing 10% (v/v) acetonitrile as well as 10% (v/v) isopropanol showed an acceptably low evaporation in the conductivity experiments. With this buffer, a stable EOF was also obtained. Conductivity measurements are generally applicable to quickly test buffers that contain organic solvents.

Determination of Residual Isometamidium in Cattle Tissues and Milk by HPLC

A determination method for the antitripanosomal agent, isometamidium (IMD) in cattle muscle, liver, fat and milk has been developed by using HPLC. The drug was extracted from a sample with acetonitrile-0.25mol/L ammonium formate methanol solution, and purified by liquid-liquid partition with ethyl acetate and water, followed by extraction of the water layer in the presence of NaCl with acetonitrile. After evaporation of acetonitrile, the residue was taken up in 1mL of 0.25mol/L ammonium formate methanol solution. The drug was determined by HPLC with detection at 380nm using an octyl column (TSK-GEL Octyl-80Ts, 4.6mm i. d.×150mm), and acetonitrile-0.03mol/L citric acid containing 0.005mol/L sodium 1-heptanesulfonate (3:7) as an eluent. Recoveries of the drug from cattle muscle, liver, fat and milk were 76.0, 75.3, 88.0 and 89.0%, respectively, when 0.1μg/g of IMD was spiked. The detection limit was 0.01μg/g. The analysis of IMD by LC/MS was also investigated.

Quantitation of insulin by capillary electrophoresis and high-performance liquid chromatography method comparison and validation

Two validated high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) assays for insulin are compared. Both methods are selective and robust, with best reproducibility in a 0.9% sodium chloride solution, pH 7–8, as the sample solvent. It is shown that, besides sample solvent and buffer pH, acetonitrile volatility is a crucial point for reproducibility. Its high importance for selectivity and ruggedness is also stressed. Trends have been extensively investigated and characterized. The separation efficiency is better for the CE method. Furthermore, the analysis time of the CE method is up to four times shorter than the respective parameter in HPLC and the acetonitrile consumption is more than 100-fold less. Earlier works stated that all relevant precision data, such as relative signal standard deviation (1.6% R.S.D. for peak areas, n=20), precision of the analytical result and the limit of quantitation, were about a factor of two worse than for corresponding HPLC data (0.8% R.S.D. for peak areas, n=19). This CE precision was further improved using relative instead of absolute peak areas, which compensate for the injection error (1.3% R.S.D. for relative peak areas, n=20). If acetonitrile evaporation is avoided, by covering the buffer with mineral oil, reproducibility is even better than with the HPLC assay (0.5% R.S.D. for relative peak areas, n=60).

Determination of the synthetic steroid norgestomet in bovine plasma by capillary column gas chromatography/negative chemical ionization mass spectrometry.

A sensitive and specific method is described for the determination of norgestomet in bovine plasma as low as 10 ppt with better than 83% average recovery and a relative standard deviation (RSD) of range 1-3%. Norgestomet is separated from the bulk of the endogenous substances in plasma by adsorption on a PrepSep C18 extraction column and elution with acetonitrile. The residue after evaporation of acetonitrile is reacted with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride to form syn and anti geometric isomers of the mono-oxime derivative. The derivative, after further clean-up and evaporation of solvent, is reconstituted with cyclohexane, and an aliquot is analyzed by capillary column gas chromatography/negative chemical ionization mass spectrometry using methane as the carrier gas. Selected ion monitoring was employed to detect the [M - HF]- fragment ion of the norgestomet mono-oxime derivative (m/z 547) and its dideuterated mono-oxime analog (m/z 549) which serves as the internal standard. Quantification is achieved by using the Quantitative Selected Ion Monitoring Processing System (QSIMPS) software to generate a standard curve of fragment ion area ratios v. concentration of norgestomet, and then calculate sample concentrations.

Analysis and Frequency of Detection of Dichlofluanid in Foodstuffs

Dichlofluanid was determined at ppb levels in foodstuffs by ECD-GC using 4 kinds of liquid phases with no interference. Addition of silver nitrate to samples when they were homogenized with acetone was indispensable to protect dichlofluanid from decomposition caused by SH compounds which are present in foods, and in wheat an interfering substance showing a similar retention time to dichlofluanid was also eliminated by addition of silver nitrate. After evaporation of acetone, the residue was dissolved in n-hexane and the hexane solution was extracted with acetonitrile. After evaporation of acetonitrile, the residue was column chromatographed on Florisil. Investigation of commercially available vegetables, fruits and wheat showed a high frequency of detection of dichlofluanid in greenhouse products, especially tomatoes, though at low levels.

Determination of nifursol in medicated animal feeds using high-performance liquid chromatography. Analytical Methods Committee.

A method is given for the determination of nifursol in medicated animal feeds by high-performance liquid chromatography. The additive is extracted from the feed sample into acetonitrile and this solution is concentrated by evaporation of acetonitrile under reduced pressure. The nifursol content of this solution is determined by HPLC using a column containing a strong anionic-exchange packing.

Simultaneous Determination of Selenocyanate and Thiocyanate Ions in the Presence of Cyanide by Oxidation withbis(Trifluoroacetoxy) iodobenzene

Abstract An investigation of the use of potentiometric titrations of selenocyanate and thiocyanate aqueous solutions, in the presence of cyanide ions, with bis (trifluoroacetoxy) iodobenzene in acetonitrile and then the gravimetric determination of the products of the reactions, elemental selenium and sulphate ions, has been carried out. Selenocyanates are first oxidized to selenium and then thiocyanates are oxidized to sulphate ions. Break point curves are identified. The rose-pink precipitate is filtered and the clear filtrate is warmed on a hot plate for evaporation of acetonitrile. A solution of barium chloride is added to the hot solution in order to precipitate the sulphate ions.