Summary The HPLC determination of ethylenethiourea (ETU, imidazolidine-2-thione) has been carried out by derivatisation with phenacyl
halides to give imidazole-[2,1-b]thiazoles, which were separated on a polystyrenedivinylbenzene (PS-DVB) column. A number
of different phenacyl halides including p-phenyl-, and naphthyl, were studied and the p-nitro reagent was selected as the
most suitable for residue analysis. The analysis was more sensitive than direct HPLC analysis and had a limit of detection
of 0.04 ng ETU.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
A simple, isocratic, normal phase chiral HPLC method was developed and validated for the enantiomeric separation of repaglinide,
(S)-(+)-2-ethoxy-4-N [1-(2-piperidinophenyl)-3-methyl-1-butyl] aminocarbonylmethyl] benzoic acid, an antidiabetic in bulk drug substance. The
enantiomers of repaglinide were resolved on a ChiralPak AD-H (amylose based stationary phase) column using a mobile phase
consisting of n-hexane: 2-propanol:trifluoroacetic acid (95:5:0.2 v/v/v) at a flow rate of 1.0 mL min−1. The resolution between the enantiomers was found to be not >3.5 in optimized method. The presence of trifluoroacetic acid
in the mobile phase played an important role, in enhancing chromatographic efficiency and resolution between the enantiomers.
The developed method was extensively validated and proved to be robust. The calibration curve for (R)-enantiomer showed excellent linearity over the concentration range of 900 ng mL−1 (LOQ) to 6,000 ng mL−1. The limit of detection and limit of quantification for (R)-enantiomer were 300 and 900 ng mL−1, respectively. The percentage recovery of the (R)-enantiomer ranged between 98.3 and 101.05% in bulk drug samples of repaglinide. Repaglinide sample solution and mobile phase
were found to be stable up to 48 h. The developed method was found to be enantioselective, accurate, precise and suitable
for quantitative determination of (R)-enantiomer in bulk drug substance. 相似文献
Several methanotrophic microorganisms, i.e.,Methylococcus capsulatus (Bath),Methylomonas albus (BG-8),Methylosinus trichosporium OB3b, andMethylocystis parvus (OBBP), were evaluated for growth and methane utilization. The effect of temperature was examined in the range of 25 to 45°C
for growth and methane utilization. The temperature variations (25–35°C) had minimal effect on growth ofM. albus and M. parvus. Methane consumption varied at different temperatures with a maximum of 0.67 mol%/h and 0.53 mol%/h. at 30 and 35°C, respectively,
forM. albus and M. parvus. The growth and methane consumption was slower forM. trichosporium OB3b as a maximum methane consumption of 0.07 mol%/h was obtained at 25°C and growth was inhibited at 35°C.M. capsulatus grew the best at 37°C and growth was affected at higher temperature of 45°C. Of the different cultures examined,M. albus andM. capsulatus grew the best and were further evaluated for the effect of pressure in the range of 10–50 psi. The results obtained usingM. albus demonstrated an enhancement in methane consumption rate by fourfold and final cell concentration by 40% at a pressure of
20 psi by injecting a methane/oxygen mixture, however further increase in the pressure up to 50 psi inhibited the growth.
The inhibition was not seen with nitrogen incorporated mixture of oxygen and methane, which suggest that the high partial
pressure of methane and/or oxygen are inhibitory for the growth ofM. albus. M. capsulatus was more sensitive to pressure as evidenced by inhibition at the relatively low pressure of 10 psi 相似文献
Liquid chromatography is a prominent analytical technique in separation science and chemical analysis, applied across numerous fields of research and within industrial applications. Over the past few decades, there has been a growing interest in the miniaturization of this technique, which has been particularly enabled through new miniature and portable detection technologies for in-field, at-site, and point-of-need (collectively ‘out-of-lab’) analyses. Accordingly, significant advances have been made in recent years in the development of miniaturized liquid chromatography with photometric, electrochemical, and mass spectrometric detection, enabling the development of field-deployable and portable instruments for various applications. Herein, recent developments in the miniaturization of detection systems for inclusion within, and/or coupling with, portable liquid chromatographic systems, are reviewed in detail together with critical comments and expected future trends in this area. 相似文献
A novel stability-indicating high-performance liquid chromatographic assay method was developed and validated for quantitative
determination of nitazoxanide in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated
from forced decomposition studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation
products, using an Ace5- C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH 5.5 by acetic acid) and acetonitrile
(55:45 v/v) as a mobile phase. The detection was carried out at a wavelength of 240 nm. The nitazoxanide was subjected to stress conditions
of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for nitazoxanide in base,
acid and in 30% H2O2 conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well
resolved from the main peak. The percentage recovery of nitazoxanide was from (100.55 to 101.25%) in the pharmaceutical dosage
form. The developed method was validated with respect to linearity, accuracy (recovery), precision, system suitability, specificity
and robustness. The forced degradation studies prove the stability indicating power of the method. 相似文献
A simple, rapid, and precise method is developed for the quantitative simultaneous estimation of telmisartan and ramipril
in combined pharmaceutical dosage form. A chromatographic separation of the two drugs was achieved with an ACE 5 C18, 25-cm analytical column using buffer–acetonitrile (55:45 v/v). The buffer used in mobile phase contains 0.1 M sodium perchlorate monohydrate in double distilled water pH adjusted 3.0
with trifluoroacetic acid. The instrumental settings are flow rate of 1.5 mL min−1, column temperature at 30 °C, and detector wavelength of 215 nm using a photodiode array detector. The resolution between
ramipril and telmisartan were found to be more than 5. Theoretical plates for ramipril and telmisartan were 13,022 and 6,629.
Tailing factor for ramipril and telmisartan was 0.94 and 0.98. Telmisartan, ramipril and their combination drug product were
exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were analysed by the
proposed method. Peak homogeneity data of telmisartan and ramipril is obtained using photodiode array detector, in the stressed
sample chromatograms, demonstrated the specificity of the method for their estimation in presence of degradants. The described
method shows excellent linearity over a range of 20–400 μg mL−1 for telmisartan and 2.5–50 μg mL−1 for ramipril. The correlation coefficient for telmisartan and ramipril are 1. The relative standard deviation for six measurements
in two sets of each drug in tablets was always less than 2%. The proposed method was found to be suitable and accurate for
quantitative determination and the stability study of telmisartan and ramipril in pharmaceutical preparations. 相似文献
A two-stage process for the manufacture of propylene oxide is described. The preliminary economics based on use of methanol
as a regeneration factor has resulted in a production cost of $12.10/lb of propylene oxide based on propylene oxide production
rate of 40 mg/g-cell/h in conventional reactor. Increasing the propylene oxide production from 40 to 500 mg/g-cell/h resulted
in a cost reduction from $12.10 to 5.8/lb of propylene oxide. The granular-activated, carbon-fluidized bed reactor (GAC-FBR)
absorbs the propylene oxide and when saturated is eluted with ethyl acetate, and the bed is regenerated by steam to drive
off the residual solvents. The estimated manufacturing costs are approx 59% lower (from $12.10/lb in conventional reactors
to $5.00/lb for GAC-FBRs) for products that are highly inhibitory such as epoxides. In the GAC-FBR reactor, enhancing the
propylene oxide production rate from 120 to 1500 mg/gcell/h has resulted in the cost reduction to $2.00/lb. Enhancing the
production capacity from 1 million lb to 10 million lb/yr has further reduced the cost of production to $1.00/lb.
This article is reprinted from the Symposium issue of ABAB entitled “Biotechnology for Fuels and Chemicals: Proceedings of
the Nineteenth Symposium of Biotechnology for Fuels and Chemicals” (pp. 651–659). Figures and captions are correct as they
now appear. 相似文献
A novel stability-indicating LC assay method was developed and validated for quantitative determination of olmesartan in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated from forced degradation studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation products, using an Ace5-C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH-5.5 by acetic acid) and acetonitrile (70:30 v/v) as a mobile phase. The detection was carried out at the wavelength of 235 nm. The olmesartan was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for olmesartan in acid, base and in 30% H2O2 conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of olmesartan ranged from (99.89 to 100.95%) in pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, specificity and robustness. The forced degradation studies prove the stability-indicating power of the method.