Enantioseparation of four-membered rings by gas chromatography; an overview

The separation of enantiomers by gas chromatography on a chiral stationary phase is stored and conveniently retrieved in the molecular database Chirbase/GC. According to the present information content (version 3/96), a great variety of analytes has been published in several hundred journals. A selected review is given on 364 enantiomer separations of 102 different molecules containing at least one four-membered saturated carbocyclic ring. Factors determining the degree of enantioseparation are outlined and analyzed. Received: 16 November 1996 / Revised: 17 April 1997 / Accepted: 30 April 1997     

Field method for the micro-quantitative determination of tetracycline in human urine

A simple, fast and sensitive titrimetric method has been developed for the determination of tetracycline hydrochloride in human urine using m-dinitrobenzene as color agent and Dowex 1 × 8 as detection medium. Received: 26 February 1997 / Revised: 23 April 1997 / Accepted: 29. April 1997     

Validation of a computer-program for the interpretation of infrared spectra

The capability of a modern interpretation system for IR spectra has been tested, in which the process of structural assignment is modelled by methods of fuzzy logic. Figures of merit were generated for different interpretation algorithms. These figures of merit permit the validation as well as a comparison of independent interpretation systems. The influence of the sample preparation practice onto the information content of the resulting spectrum has been evaluated as well. Automatically generated band tables show only restricted reliability. Received: 13 February 1997 / Revised: 1 April 1997 / Accepted: 3 April 1997     

Validation of a computer-program for the interpretation of infrared spectra

The capability of a modern interpretation system for IR spectra has been tested, in which the process of structural assignment is modelled by methods of fuzzy logic. Figures of merit were generated for different interpretation algorithms. These figures of merit permit the validation as well as a comparison of independent interpretation systems. The influence of the sample preparation practice onto the information content of the resulting spectrum has been evaluated as well. Automatically generated band tables show only restricted reliability. Received: 13 February 1997 / Revised: 1 April 1997 / Accepted: 3 April 1997     

MS-Pep: a computer program for the interpretation of mass spectra of peptide libraries

Electrospray mass spectrometry (ESI-MS) is an established method for the qualitative analysis of synthetic peptide libraries and combinatorial mixtures or collections of small organic compounds. However, the calculation of the mass distribution of even small peptide mixtures is a time-consuming and error-proned task. Therefore, the computer program MS-Pep has been developed, which calculates the masses of expected peptides, byproducts and the mass distributions of peptide libraries. Received: 2 December 1996 / Revised: 17 April 1997 / Accepted: 21 April 1997     

Size and phase fractionation of water components by membrane filtration Distribution patterns for arsenic, iron and manganese in aqueous effluents of tin ore settling plant

The possibility of on-line membrane size-fractionation of water components and simultaneous separation of particulate and dissolved matter at each filtration stage has been shown. The distribution patterns have been studied for As, Fe and Mn in effluent samples of tin ore tailings (Altenberg, Saxony, Germany). The seepage composition is characterized by high concentrations of Fe and As. The particulate and dissolved components were separated in five fractions between 0.025 and 8 μm. It was suggested that the distribution patterns of As and Fe compounds depend on the chemical conditions at the sampling sites. Manganese exists mainly in solvated forms in the liquid fractions. Received: 8 January 1997 / Revised: 8 April 1997 / Accepted: 9 April 1997     

Development of a modified beta-cyclodextrin based fluorosensor for dipyridamole

2,6-O-diethyl-β-cyclodextrins were prepared and immobilized onto silica gel to develop a fluorosensor for dipyridamole. The analytical performance characteristics of the proposed sensor for analysis of dipyridamole were as follows: the detection limit was 0.8 nmol/L with a relative standard deviation of 1.4% for 10 determinations of 50 nmol/L of dipyridamole. The modification of β-CD improved the sensitivity and selectivity for measuring dipyridamole. The recommended method has been successfully tested for the determination of dipyridamole in clinical samples (urine and pharmaceutical preparations). Received: 23 January 1997 / Revised: 14 April 1997 / Accepted: 21 April 1997     

A new proposal for a parameter-free integration software

An algorithm is presented that has successfully been utilized in practice for several years. It improves data analysis in chromatography. The program runs in an extremely reliable way and evaluates chromatographic raw data with an acceptable error. The algorithm requires a minimum of preliminaries and integrates even unsmoothed noisy data correctly. Received: 7 April 1997 / Revised: 23 May 1997 / Accepted: 4 June 1997     

Feasibility studies of neutron activation analysis with kilogram-size samples

Instrumental neutron activation analysis (INAA) can now directly be applied to samples with masses in the kilogram range. It enables the analysis of material which is considered to be not representative at the scale of the traditional analytical portion, but representative at much larger scale. Large sample INAA (LS-INAA) circumpasses various problems associated with sample-size reduction and homogenization. Examples of feasibility studies are given as on construction waste, contaminated soil, harbour sediment and recyclable material. Also the economics of this method of analysis is discussed. Received: 30 October 1996 / Revised: 3 April 1997 / Accepted: 16 April 1997     

A highly selective iodide electrode based on the bis(benzoin)-semiethylenediamine complex of mercury(II) as a carrier

A new PVC membrane electrode based on the bis(benzoin)-semiethylenediamine (BBSEA) complex of Hg(II) is described which exhibits excellent selectivity towards iodide, related to the unique interaction between the central Hg(II) and the iodide ion. The electrode has a linear response to iodide from 5 × 10^–7 to 5 × 10^–4 mol/L with a slope of 58 mV/dec.(20°C). The response characteristics were investigated in detail and the mechanism of the electrode was studied with AC impedance and quartz crystal microbalance (QCM) techniques. It can be used for iodide determinations in drug preparations. Received: 29 January 1997 / Revised: 17 April 1997 / Accepted: 20 April 1997     

Ion trap MS/MS of polychlorinated dibenzo-p-dioxins and dibenzofurans: confirming the concept of the molar response

It has been shown that the concept of molar response, which is applicable to single ion monitoring of M⁺, can also be employed for ion trap MS/MS measurements, simplifying the determination of PCDD/PCDF by an extended IDA approach. Received: 22 April 1997 / Revised: 16 June 1997 / Accepted: 18 June 1997     

ICP-MS – A powerful analytical technique for the analysis of traces of Sb, Bi, Pb, Sn and P in steel

The determination of Sb, Bi, Sn, Pb and P in steel using quadrupole- and double-focusing-sector-field-ICP-MS is described. Simple and fast methods for sample preparation were developed with regard to requirements of ICP-MS. Several certified steel reference materials were analyzed in order to verify the accuracy and precision of the applied methods. Received: 22 April 1997 / Revised: 19 June 1997 / Accepted: 23 June 1997     

Experiments to determine the escape probability of photoelectrons

A novel experimental method for the assessment of the escape probability of photoelectrons as a function of depth and their mean escape depths is described and illustrated for photoelectrons leaving an aluminium oxide surface. The results are compared with those of the straight line approximation model calculations. Received: 30 July 1997 / Revised: 7 April 1998 / Accepted: 8 April 1998     

Spectrophotometric reaction rate method for the determination of molybdenum by its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide

A kinetic spectrophotometric method for the determination of molybdenum is based on its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide. The decrease of the absorbance of pyrogallol red in the presence of hydrogen peroxide with time from 0.5 to 4.5 min is proportional to the concentration of Mo(VI) over the range 0.010–0.500 μg/mL. The limit of detection is 0.008 μg Mo/mL. The precision and the effect of the presence of more than forty ions on the molybdenum determination are reported. Probable interferences are completely removed by a cation exchange resin. The procedure was successfully applied to the determination of molybdenum in plant materials and steels. Received: 28 April 1997 / Revised: 16 June 1997 / Accepted: 18 June 1997     

Platinum speciation with hyphenated techniques: high performance liquid chromatography and capillary electrophoresis on-line coupled to an inductively coupled plasma-mass spectrometer – application to aqueous extracts from a platinum treated soil

1. An on-line hyphenation of reversed phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma-mass spectrometry (ICP-MS) is applied, using an ultrasonic nebuliser combined with a membrane desolvator as the interface. Thus, organic solvents (e.g. methanol, hexane) or gradients (e.g. methanol/water) as well as aqueous NaHCO₃/NaCl mixtures can be directly used without influence on the plasma. The high resolution power of HPLC enables the separation of Pt-species, whereas ICP-MS is taken for element specific detection with low detection limits. 2. Additionally, a powerful on-line coupling of capillary electrophoresis (CE) and ICP-MS [1, 2] was used for platinum speciation in parallel. With these two methods, independent from each other, first characterisation is achieved about the nature of Pt species formed by interaction with a soil. Aqueous extracts of a clay-like humic soil, treated with a Pt contaminated tunnel dust and Pt model compounds [3] were examined to elucidate transformation processes of Pt-species in a soil. Received: 19 February 1997 / Revised: 15 April 1997 / Accepted: 18 April 1997     

Platinum speciation with hyphenated techniques: high performance liquid chromatography and capillary electrophoresis on-line coupled to an inductively coupled plasma-mass spectrometer – application to aqueous extracts from a platinum treated soil

1. An on-line hyphenation of reversed phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma-mass spectrometry (ICP-MS) is applied, using an ultrasonic nebuliser combined with a membrane desolvator as the interface. Thus, organic solvents (e.g. methanol, hexane) or gradients (e.g. methanol/water) as well as aqueous NaHCO₃/NaCl mixtures can be directly used without influence on the plasma. The high resolution power of HPLC enables the separation of Pt-species, whereas ICP-MS is taken for element specific detection with low detection limits. 2. Additionally, a powerful on-line coupling of capillary electrophoresis (CE) and ICP-MS [1, 2] was used for platinum speciation in parallel. With these two methods, independent from each other, first characterisation is achieved about the nature of Pt species formed by interaction with a soil. Aqueous extracts of a clay-like humic soil, treated with a Pt contaminated tunnel dust and Pt model compounds [3] were examined to elucidate transformation processes of Pt-species in a soil. Received: 19 February 1997 / Revised: 15 April 1997 / Accepted: 18 April 1997     

Spectrophotometric reaction rate method for the determination of molybdenum by its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide

A kinetic spectrophotometric method for the determination of molybdenum is based on its catalytic effect on the oxidation of pyrogallol red with hydrogen peroxide. The decrease of the absorbance of pyrogallol red in the presence of hydrogen peroxide with time from 0.5 to 4.5 min is proportional to the concentration of Mo(VI) over the range 0.010–0.500 μg/mL. The limit of detection is 0.008 μg Mo/mL. The precision and the effect of the presence of more than forty ions on the molybdenum determination are reported. Probable interferences are completely removed by a cation exchange resin. The procedure was successfully applied to the determination of molybdenum in plant materials and steels. Received: 28 April 1997 / Revised: 16 June 1997 / Accepted: 18 June 1997     

Cathodic stripping voltammetry of NADH in presence of Cu2+

The adsorption and accumulation of NADH and the Cu²⁺-NADH system at the mercury electrode surface was examined using differential pulse cathodic stripping voltammetry (DPCSV). The method was developed for analytical trace determination of NADH. Experimental and operational parameters for the quantitative determination of NADH were optimized and the detection limit was found to be 9.960 × 10^–8 mol/L. The effect of some interferences (e.g. purine compounds, amino acids and some metal ions) was considered. Received: 3 January 1997 / Revised: 1 April 1997 / Accepted: 4 April 1997     

Cathodic stripping voltammetry of NADH in presence of Cu2+

The adsorption and accumulation of NADH and the Cu²⁺-NADH system at the mercury electrode surface was examined using differential pulse cathodic stripping voltammetry (DPCSV). The method was developed for analytical trace determination of NADH. Experimental and operational parameters for the quantitative determination of NADH were optimized and the detection limit was found to be 9.960 × 10^–8 mol/L. The effect of some interferences (e.g. purine compounds, amino acids and some metal ions) was considered. Received: 3 January 1997 / Revised: 1 April 1997 / Accepted: 4 April 1997     

Adsorption studies of dodecylamine at the quartz interface using an electrode-separated piezoelectric sensor

The adsorption process of dodecylammonium chloride (DAC) from aqueous solutions onto a quartz crystal interface was investigated in situ using an electrode-separated piezoelectric sensor (ESPS). Increasing amounts of DAC adsorbed onto a quartz crystal surface resulted in linearly decreasing oscillating frequencies of the ESPS. The adsorption density can be monitored by the frequency decrease. The adsorption density obtained by calculation using the Sauerbrey equation in the ESPS method is greater than that in solution depletion method. A calibration coefficient is added into the Sauerbrey equation to correct the influence of surface roughness of the quartz crystal on the adsorption density. The influence of solution properties on the adsorption density measurement was discussed. A dependence of the adsorption density on pH was reported. Received: 17 April 1997 / Revised: 1 December 1997 / Accepted: 7 December 1997