Cyclodextrins as chiral selectors in capillary electrophoresis: a comparative study for the enantiomeric separation of some beta-agonists.

A comparative study for the enantiomeric separation of terbutaline, clenbuterol, salbutamol and dobutamine was performed by capillary electrophoresis using cyclodextrins and their derivatives as chiral selectors. Several parameters such as buffer composition and temperature were studied. Simple, fast and reliable enantioseparations were achieved for all drugs studied, especially when the isomerically pure sulfated beta-cyclodextrin derivatives were used as chiral selectors.

Moclobemide-selective membrane electrode and its pharmaceutical applications.

A liquid membrane electrode prepared with moclobemide-dipicrylamine ion-pair complex, dissolved in nitrobenzene as solvent, was studied for analytical performance. The linear response covers the range 10(-3)-10(-6) M moclobemide solution, with a slope of 50.7 mV decade(-1) (pH range 3.5-8). The detection limit is 3 x 10(-7) M. The electrode shows stability, good reproducibility and fast response. The selectivity of the electrode is good. There are two important interfering ions: mianserin and thiamine (Vitamin B(1)). The compression excipients (such as Mg(2+), starch, talcum powder) do not interfere. These characteristics of the electrode enabled it to be used for the determination of moclobemide in drugs and as an active substance, via indirect and direct potentiometric methods. Via an indirect potentiometric method moclobemide, as an active substance, can be determined with an average recovery of 99.96% and a relative standard deviation of 0.85%, and this method can also be used for its determination in drugs with a relative standard deviation of < 2%. The electrode is useful for the determination of the dissolution rate of moclobemide tablets. The physical processes are numerically simulated by typical equations. The apparent first-order rate constants for disintegration and dissolution were calculated.

HLA class I self peptides isolated from a T-cell leukemia reveal the allele-specific motif of HLA-B38.

Naturally-processed self peptides bound to HLA class I molecules of a T-cell leukemia (HLA-A1, A31, B38, B58) were isolated for sequence analysis. Acid-eluted peptides were subjected to reversed-phase HPLC separation and single-fraction sequencing was performed by Edman degradation. The peptides were found to be mostly nonamers and could be grouped into three distinct structural motifs. One of the peptide groups consistently displayed histidine at position 2 and a bulky hydrophobic residue at the C-terminus (XHXPXXXXY/F). The only HLA class I structure expressed by this T-cell leukemia which is consistent with the binding of peptides carrying this sequence motif is HLA-B38. A peptide binding assay confirmed this assignment. HLA-B38 is present in 10-12% of the Jewish population and is associated with several autoimmune disorders. The HLA-B38 motif may be an important tool for identifying potential T-cell epitopes involved in these diseases and for designing peptide vaccines.

Use of an ion-selective membrane electrode for the determination of the active components in intestopan.

The conditions for the determination of broxyquinoline and brobenzoxaldine, the active components of "Intestopan", by use of ion-selective membrane electrodes are described. Broxyquinoline is determined directly through precipitation with CuSO(4), and brobenzoxaldine is first hydrolysed in alkaline solution and the product precipitated with CuSO(4). In both cases the CuSO(4) in excess is determined by potentiometric titration at pH 5.6 with EDTA, a Cu(2+)-selective electrode being used for end-point detection.

Nafronyl ion-selective membrane electrodes and their use in pharmaceutical analysis.

A simple potentiometric method is described for the rapid determination of nafronyl-drugs in pharmaceutical preparations such as tablets. Nafronyl ion-selective membrane electrodes with either the nafronyl-dipicrylamine ion-pair complex in 1,2-dichloroethane or the nafronyl-dinonylnaphthalenesulphonic acid ion-pair complex in a PVC matrix as electroactive materials were used. Both electrodes exhibit near-Nernstian responses to protonated-nafronyl activity from 10(-2) to about 10(-5)M, in pH ranges that depend on the nature of the electroactive material used in the membrane. Nafronyl in the mg-range can be determined by potentiometric titration with sodium tetraphenylborate solution, with a relative standard deviation of less than 2.0%. No interference from any excipients in the tablets was observed.

Determination of sulpha-drugs with ion-selective membrane electrodes--II.

Two liquid-membrane electrodes, one sensitive to Cu(2+) and the other to Ag(+), were used for the determination of various sulpha-drugs with pK(a) > or = 6 (as the sodium salts) by potentiometric titration with CuSO(4) and AgNO(3). The construction and basic characteristics of these two electrodes are discussed.

Nicolae Teclu (1839-1916) A pioneer of flame spectroscopy.

A brief account is given of Teclu's career and his contributions as a pioneer of the study of flames.

Construction of a new Hg(2+)-selective liquid-state electrode.

The construction and basic characteristics of a new liquid-state Hg(2+)-selective membrane electrode are discussed. The membrane consists of the PAN chelate of Hg(II), dissolved in CHCl(3). The linear response range of the electrode is 10(-1) -10(-5)M Hg(2+) with a slope of 28.5 mV/decade of concentration. The response time of the electrode in dilute solutions is less than 3 min, and in concentrated solutions it is only a few sec. The electrode has been used in precipitation or complexation titrations in which Hg(2+) is involved (e.g., in the determination of some organic compounds in drug synthesis).

Construction and analytical applications of an extractive electrode sensitive to mercury(I).

The construction and characteristics of a new type of extractive electrode sensitive to Hg(2+)(2) are described. The performance of the electrode is compared with that of an ion-selective electrode with mercurous dithizonate as the active substance. The Hg(2+)(2) -extractive electrode contains Pd(HDz)(2) in its membrane. Its stability and sensitivity are remarkable. It has been used as indicator electrode for the titration of halides alone and in mixtures, and for determination of mercury(I), mercury(II), silver, and of substances containing or reacting with mercury. The basis of the electrode response is discussed.

A liquid state Hg(2+)-sensitive electrode.

The construction and basic characteristics of a liquid-state Hg(2+)-sensitive electrode are discussed. The membrane consists of the Hg(2+) chelate of diketohydrindylidene-diketohydrindamine (DYDA) in chloroform. The range of linear response of the electrode is 10(-1)-10(-5)M Hg(2+) with a slope of 31 mV/decade. The response time of the electrode is a few seconds in concentrated solutions. The electrode may be used with good results in potentiometric titrations involving Hg(2+).

Potentiometric determination of n-butyl-1-biguanide with a liquid-state Cu2+-sensitive electrode.

Alkyl-1-biguanides are determined by titration with copper(II), or excess of copper(II) is added and the surplus determined by titration with EDTA, a liquid-state copper-sensitive electrode being used in both cases for potentiometric detection of the end-point.