摘要:

Methyl pyrazines, particularly 2,5-dimethylpyrazine (DMP) and 2,3,5-trimethylpyrazine (3MP) are among the major flavor compounds associated with various seed and grain food processing operations, including roasting and drying. Synthetic polymers selective for DMP and 3MP were prepared by a molecular imprinting technique, and the binding characteristics of the imprinted polymers were examined by chromatographic methods. Despite the low molecular weight and lack of strongly interacting pendant functional groups in the pyrazine targets, the polymers showed selectivity for their respective templates over other pyrazines. Such polymers are envisioned to be of potential use in the analysis of flavor compounds in the food industry and in the selective isolation or enrichment of flavor profiles.

ISSN:0003-2719    

DOI:10.1080/00032719908542860

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Thiamazole is covalently attached onto the surface of a silver electrode to form a chemically modified one, which is long-lived and stable. It shows the capability of selectively complexing myoglobin and can be applied as a selective biosensor for this compound. Myoglobin is accumulated onto the CME at 0.32V (vs.SCE). After exchanging the medium, it is determined by differential pulse stripping voltammetry. A cathodic stripping peak is obtained by scanning the potential from 0.32V to 0.0V. The peak currents are linearly proportional to the concentrations of the protein in the range of 0.5∼5.0mg/ml. The relative standard deviation is 6.4% for 6 successive determinations of 3.0mg/ml myoglobin.

ISSN:0003-2719    

DOI:10.1080/00032719908542861

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A Pyrocatechol Violet (PCV) modified electrode for the voltammetric determination of aluminum is reported. The modified electrode is simply prepared by dip-coating a pyrolytic graphite electrode in a NaAc-HAc buffer solution of PCV. Optimum experimental conditions for aluminum determination include a 0.2 mol/L NaAc-HAc buffer solution of pH 4.8, a PCV concentration of 0.02 mol/L used to modify the electrode and the use of differential-pulse mode for measurement. The peak currents of differential pulse voltammograms (DPV) decrease with the addition of Al into the buffer solution while the peak potentials remain the same. The decreasing value of peak current ▵ipis linear with Al concentration in the range of 1x10−8to 1x10−7mol/L and 1x10−7to 1x10−6mol/L. The detection limit is 5x10−9mol/L and the relative standard deviation for 4x10−8mol/L Al is 2.9% (n=8). The stability of this electrode is satisfactory. No serious interference is found. This method has been applied to determine Al in drinking water samples.

ISSN:0003-2719    

DOI:10.1080/00032719908542862

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The hydrolysis of starch by the catalysis of α-amylase was monitored by a network analysis method, resulting in a new method for determination of α-amylase with a Bulk Acoustic Wave (BAW) viscosity sensor. The response of the sensor to the viscosity and density change of this process are measured. The frequency shift during a certain time interval is linearly related to the concentration of α-amylase in the range of 20-500 U.L−1. This method is simple, as no extra reagent such as chromogen or fluorescein is needed. It is fit for the continuous monitoring of the catalytic process and it may also be used to study the dynamics of the process.

ISSN:0003-2719    

DOI:10.1080/00032719908542863

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Through flow injection analysis experiments, it was discovered that unsaturated complexes of Cu(II) with proteins had a much stronger catalytic effect on the luminol–H2O2chemiluminescence reaction than did Cu(II). Based on this, a new rapid and sensitive method for determination of some proteins in the range 0.1–20.0 μg ml−1was established. The detection limits were at the 0.03–0.05μg ml−1level for bovine serum albumin (BSA), human serum albumín (HSA), human γ–globulin (γ–G), and egg albumin (EA). The method was used for the determination of proteins in human serum with satisfactory results.

ISSN:0003-2719    

DOI:10.1080/00032719908542864

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple method for differentiation of carbonic anhydrase (CA) I, from CA II, is described based on using the nicotinates as specific CA I inhibitors. Nicotinates inhibit the activity of CA I activity; at a concentration of 5x10−1M 100% inhibition is complete. But no effect on CA II activity is observed.In vivoadministration of xanthinol nicotinate in doses of 20 mg/kg b.w. completely inhibited erythrocyte CA I activity. Association inex vivoof methyl-nicotinate at a concentration of 5x10−1M did not further modify erythocyte CA activity that had already been reduced by i.v. administration of xanthinol nicotinate. The nicotinate class could be used as a test for an accurate differentiation of CA I from CA II activityin vitro, in vivoand inex vivo; by subtraction of I from total CA activity, one could also find the erythrocyte CA II activity. Theex vivoassays, using the test with nicotinates we call Nicosilvanil, would easily allow monitoring of CA I and II activity changes under physiological, pathological and experimental conditions, in response to various endogenous or therapeutical stimuli with either activating or inhibitory effects. Considering convenience, simplicity, and cost effectiveness of the reagents for theNicosilvanil Test, this assay has the potential of being useful in routine analysis and differentiation of CA I from CA II activity in erythrocyte samples, as well as in other tissues and organs.

ISSN:0003-2719    

DOI:10.1080/00032719908542865

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A flow-through method for the determination of free aromatic amines in radiodiagnostic preparation was developed. The concentration range of determination, sensitivity of measurement, limit of detection and determination, and repeatability of measurement were found. The method was tested for the analysis of the compound Iodipamide.

ISSN:0003-2719    

DOI:10.1080/00032719908542866

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A flow-injection chemiluminescence (CL) analysis for the determination of analgin is presented. It is based on the CL reaction of analgin with Ce (IV) in sulphuric acid sensitized by the fluorescent dye Rhodamine 6G. The proposed procedure has a linear range of 0.05-10ug/ml, with a relative standard deviation (RSD) of 2.1% at 1.0ug/ml. The detection limit (3σ) is 0.02ug/ml. The method has been successfully applied to the determination of analgin in tablets.

ISSN:0003-2719    

DOI:10.1080/00032719908542867

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB) has been shown to improve liver function in chronic hepatitis patients. Despite the fact that the oral bioavailability for DDB appears to be low and variable, the intestinal absorption of the drug is not well understood because of the lack of sensitivity and inadequate separation of DDB from endogenous peaks derived from the serum in previously developed HPLC assays. The present study describes a reliable HPLC method for DDB in serum samples for normal dose human bioavailability trials. A deproteinated serum sample was subjected to a solid-phase extraction procedure. The residue of the Sep-Pak eluent was reconstituted in acetonitrile and an aliquot was directly injected onto an octadecyl silica column (4 μm, 250 x 4.5mm I.D.). The mobile phase consisting of acetonitrile and water (52.5% acetonitrile in water, v/v), was delivered at a flow rate of lml/min, and DDB elution from the HPLC column was monitored by UV absorption at 278nm. The assay was linear in the range of 5-100ng DDB/ml serum with inter-day and intra-day variation less than 14.3 and 13.2 %, respectively. To determine whether the HPLC assay can be utilized in normal dose bioavailability studies, human serum samples (1ml each) were obtained from a typical normal dose bioavailability study (oral capsule for DDB; 15 mg as DDB) and analyzed for DDB. The drug was readily detectable in all samples from 30min to 720min after administration. Therefore, these data indicate that this HPLC assay is readily applicable to a normal dose pharmacokinetic study of DDB in human subjects.

ISSN:0003-2719    

DOI:10.1080/00032719908542868

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λmax.

ISSN:0003-2719    

DOI:10.1080/00032719908542869

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor