High-performance liquid chromatographic determination of (−)-cathinone in plasma

Summary High-performance liquid chromatography (HPLC) for the determination of (–)-cathinone in rabbit and human plasma has been studied. The problem of dimerization during extraction from plasma was satisfactorily resolved. Detection was by UV at 257 nm. Concentration levels as low as 24 ng ml^–1 were satisfactorily determined. This level of sensitivity should be adequate for the detection of (–)-cathinone in the blood of khat users and also for the quantitative determination of (–)-cathinone in blood for pharmacokinetic purposes. The applicability of the assay procedure to pharmacokinetic studies is demonstrated.     

Determination of tetracyclines in plasma by high-performance liquid chromatography

A new method for the separation and quantitative determination of certain anti-biotics of the tetracycline series in blood plasma by high-performance liquid chromatography on a column filled with Partisil PXP 5 silica gel is described.I. M. Sechenov First Moscow Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 376–379, May–June, 1981.     

Determination of the guanosine content of technical preparations

A method is proposed for the quantitative determination of the guanosine contents of technical preparations using the Folin reagent. The sensitivity of the method is 2.5 µg/ml, and the error of the determination does not exceed ±2.3%.All-Union Scientific-Research Institute of Applied Biochemistry, Olaine. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 504–507, July–August, 1983.     

Quantitative determination of raffinose in cottonseed meal

A chromatographic method is proposed for the quantitative determination of raffinose in cottonseed meal. The relative error of a single determination is ±4.0%.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 698–699, November–December, 1984.     

Determination of stichoposides in the body of the holothurianStichopus japonicus

A method has been developed for the quantitative determination of triterpene glycosides — stichoposides — in the tissues of the Far Eastern holothurianStichopus japonicus Selenka. The quantitative determination of the combined triterpene glycosides was based on the isolation of a glycosidic fraction from an ethanolic extract on a column of Polikhrom-1 with subsequent spectrophotometry at 268 nm of the product formed as the result of the reaction of the glycosides with 1 N NaOH. The quantitative determination of the individual glycosides is based on the densitometry of slides or thin-layer chromatography in silica gel with the aid of a Lyuman-IUF-1 luminescence microscope.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Pacific Ocean Institute of Oceanography and Fisheries. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 56–59, January–February, 1984.     

Extraction by reversed micelles of triton N-42 for the spectrophotometric determination of cetyltrimethylammonium bromide

Micellar preconcentration of 1 : 2 associates of Bromophenol Blue with cetyltrimethylammonium bromide is proposed to improve the procedure for the spectrophotometric determination of cationic surfactants. The preconcentration procedure involves quantitative extraction by reversed micelles of Triton N-42 in decane followed by the decomposition of the micellar solution with chloroform. The loss of 10^–7–10^–5 M cetyltrimethylammonium bromide in 5–100-fold preconcentration was not supported by the added-found method (RSD = 3–5%). The determination limit for cetyltrimethylammonium bromide is 2 × 10^–7 M.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 17–21.Original Russian Text Copyright © 2005 by Demidova, Bulavchenko.     

Determination of trichlormethiazide in human plasma and urine by high-performance liquid chromatography

Summary This paper describes a high-performance liquid chromatographic (HPLC) assay method for the determination of trichlormethiazide (TCM) in human plasma and urine. After extraction and separation on an ODS column TCM from plasma was detected by oxidation in an electrochemical detector (ECD) by a porous graphite electrode. The sensitivity was better than HPLC with UV detection, enabling the determination of 2 ng ml^–1 TCM in human plasma. This method also allows determination of TCM at higher concentrations by exchanging the UV for the electrochemical detector. To study the pharmacokinetics, TCM in plasma and urine was assayed with coefficients of variation in the range 2–3%. The method has the advantages of high sensitivity for plasma assay and high precision with a simple procedure for both plasma and urine samples. Small samples of 0.5 ml plasma per assay also reduced the total volume of plasma needed.     

Methods of assessment of atropine and scopolamine levels in transdermal permeation

Three methods of atropine and scopolamine determination in transdermal permeation have been developed. Radiometric determination seems to be an excellent, quick and extremely sensitive method, which ought to be preferred when working with biological systems. The radioreceptor analysis is of group specificity. It can be used to advantage in monitoring atropine plasma concentrations exceeding 1.5 ng cm^–3 and scopolamine concentrations above 50 pg cm^–3. GC/MS provides adequate specificity and sensitivity for the determination of therapeutic levels of atropine and scopolamine in blood. The sensitivity of this method is approximately 1–2 ng cm^–3.     

Chromatopolarographic determination of the alkaloids from the seeds ofHaplophyllum perforatum

Summary 1. The polarographic behavior of haploperine, haplopine, haplophyllidine, and perforine in Britton-Robinson buffer solutions and in (C₂H₅)₄NOH solutions has been studied. Optimum conditions for their quantitative determination in solutions within the range of concentrations from 5×10^–4 to 1×10^–2 M have been found.2. A method for the separate quantitative determination of the alkaloids in the seeds ofH. perforatum has been developed.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 5, pp. 333–337, 1966     

Quantitative determination of cineol

Summary 1. A method for the quantitative determination of cineol in the raw material and in eucalyptus preparations by IR spectroscopy has been developed.2. The method possesses high accuracy and is reliable and specific.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–17, January–February, 1975.     

Chromato-photocolorimetric determination of digoxin

Procedures have been developed for the quantitative determination of digoxin as such and in solutions for injection and tablets by a chromato-photocolorimetric method with the aid of which it is possible to obtain reliable results with adequate accuracy. The relative error of the determination does not exceed ±4.0%.All-Union Scientific-Research Institute of Pharmacy, Moscow. Tashkent Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 66–71, January–February, 1985.     

Rapid analysis of fluoxetine and its metabolite in plasma by LC-MS with column-switching approach

A rapid and sensitive method was developed for the simultaneous determination of fluoxetine and its primary metabolite, norfluoxetine, in plasma. It was based on a column-switching approach with a precolumn packed with large size particles coupled with a liquid chromatography–electrospray ionisation–mass spectrometry (LC-ESI-MS). After a simple centrifugation, plasma samples were directly injected onto the precolumn. The endogenous material was excluded thanks to a high flow rate while analytes were retained by hydrophobic interactions. Afterwards, the target compounds were eluted in back flush mode to an octadecyl analytical column and detected by ESI-MS. The overall analysis time per sample, from plasma sample preparation to data acquisition, was achieved in less than 4 min. Method performances were evaluated. The method showed good linearity in the range of 25–1000 ng mL^–1 with a determination coefficient higher than 0.99. Limits of quantification were estimated at 25 ng mL^–1 for fluoxetine and norfluoxetine. Moreover, method precision was better than 6% in the studied concentration range. These results demonstrated that the method could be used to quantify target compounds. Finally, the developed assay proved to be suitable for the simultaneous analysis of fluoxetine and its metabolite in real plasma samples.     

Determination of a new calcium antagonist in human plasma by liquid extraction enrichment and HPLC with UV detection

Summary An HPLC method has been developed for the determination of SL 85.1016, a new calcium antagonist arylbenzylamide methylthioether derivative. SL 85.1016 and the internal standard, SL 87.0210, are extracted from alkaline human plasma withn-hexane and back extracted into 0.05 M phosphate buffer (pH 2.5; 0.2 ml). Acetonitrile (50 l) is added to the final aqueous extract in order to prevent absorption of the compounds of interest onto the walls of the glass tube; this solution then is partially processed by HPLC on a C₁₈ column with UV detection (254 nm). The determination limit of the method is 2 ng.ml^–1 of SL 85.1016 in human plasma; the response to the drug is linear in the range 2–200 ng.mg^–1.     

Quantitative determination of vincanidine in the roots of Vinca erecta

Conclusions 1. An extraction-photometric method for the quantitative determination of vincanidine is proposed.2. A method for the separate determination of the amounts of vincanine and vincanidine in a single sample of raw material has been developed.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodhysk Soedinenii, No. 1, pp. 50–52, January–February, 1974.     

Method for the quantitative determination of adlumine inCorydalis sempervirens and as the isolated substance

A chromato-spectrometric method has been developed for the quantitative determination of the biologically active alkaloid adlumine of pale corydalis which permits the determination of adlumine in the plant material with an accuracy of ±3.62% and of the isolated substance with an accuracy of ±0.79%.N. N. Sechenov First Moscow Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 346–349, May–June, 1984.     

Quantitative determination of narwedine inUngernia victoris andU. Severtzovii

Summary A polarographic method for the quantitative determination of narwedine inUngernia victoris and a chromatopolarographic method for its determination inU. severtzovii have been proposed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 610–612, September–October, 1975.     

Xanthones from <Emphasis Type="Italic">Halenia corniculata</Emphasis>. 2. Quantitative Determination of Total γ-Pyrone Content in the Aerial Part

A method for quantitative determination of total γ-pyrone content in the aerial part of Halenia corniculata was developed. Their total content in various samples of the aerial part was investigated.__________Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 245–247, May–June, 2005.     

Determination of triterpene saponins in fruit of the hawthorn

A method has been developed for the quantitative determination of triterpene saponins in the fruit of the hawthorn (haws) which is based on the formation of a complex of these compounds with tungstophosphoric acid on a sorbent with the use of the photodensitometric method. Advantages of the method are specificity, high sensitivity, and reproducibility.All-Union Scientific-Research Institute of Pharmacy, USSR Ministry of Health, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 230–232, March–April, 1989.     

Application of chemometric methods to the simultaneous kinetic spectrophotometric determination of iodate and periodate based on consecutive reactions

A kinetic spectrophotometric method for the simultaneous determination of iodate and periodate in mixtures was proposed. The method is established on the different kinetic behaviours of the analytes which react with starch–iodide in the presence of sodium chloride in sulfuric acid medium. The kinetic data were collected from 260 to 900 nm every 10 nm, within a time range of 0–180 s at 1 s interval, and the absorbance collected at 291, 354 and 585 nm, respectively, increased linearly with the concentration between 0.1–1.2 mg L^− 1 for both iodate and periodate. The mechanism investigation revealed that the iodate/periodate–iodide–starch system is a consecutive reaction. Subsequently, the mathematical model for the quantitative kinetic determination based on the consecutive reactions by utilizing chemometric methods was deduced, and the simultaneous determination of synthetic mixtures of iodate and periodate was then applied. Kinetic data collected at 291, 354 and 585 nm, were processed by chemometric methods, such as classical least square (CLS), principal component regression (PCR), partial least square (PLS), back-propagation artificial neural network (BP-ANN), radial basis function–artificial neural network (RBF-ANN) and principle component–radial basis function–artificial neural network (PC-RBF-ANN). The results showed that calibration model with the data collected at 354 nm had some advantages for the prediction of the analytes as compared with the ones of other two wavelengths, and the PLS and PC-RBF-ANN gave the lower prediction errors than other chemometric methods. The proposed method was applied to the simultaneous determination of iodate and periodate in several real samples; and the standard addition method yielded satisfactory recoveries in all instances.     

A simple high-performance liquid chromatographic determination of mexiletine in human plasma at therapeutic levels

Summary A method for the quantitative determination of mexiletine in human plasma by high-performance liquid chromatography has been described. The plasma samples are buffered to pH 12 and extracted on Clin-Elut columns with diethylether-ethylacetate (1:1), after addition of the internal standard, the 2,4,6 methyl analogue of mexiletine. The minimum detectable amount of mexiletine is 50 ng in 0.5 ml plasma. Recovery is between 96–114% and the relative standard deviation at 1.5 ml^–1 level of mexiletine is 2.1% Accurate determinations of human plasma levels were performed after oral or intravenous treatment.Part of the work was presented at the 29. Kongreß der Deutschen Gesellschaft für Laboratoriumsmedizin, Hamburg 1985.