cis-Reticulatacin-10-ones A and B were synthesised as a predefined mixture of diastereoisomers (dr ∼ 1 : 9) in nine steps from the acid chloride 8, and without the use of hydroxyl protecting groups. Comparison of the chiral HPLC chromatogram of the synthetic sample with that of the natural product isolated from the roots of the tropical fruit tree Annona muricata L. showed the natural product t...

Hydroxylamines gradually undergo oxidation to their oximes on being dissolved in organic solvent (e.g. methanol). This phenomenon was followed by (1)H-NMR and liquid chromatography-mass spectrometry (LC-MS). The oxidation rate was estimated from the peak area observed on the mass chromatogram at the protonated molecule or fragment ion on LC-atmospheric pressure chemical ionization (APCI)-MS. Th...

A semicomatose 34-year-old man had fever, heart murmur, and multiple gangrenous lesions. Several blood cultures were negative. Cultures of the heart valve grew beta-haemolytic streptococcus group B. The organism was seen in buffy-coat examination of the venous blood. The gas-liquid chromatogram of the serum was different from those of normal controls and of patients with invasive candida infect...

Fig. 6. Analysis of the volatile amines present in Chenopodium vulvaria L. Curve A: standard mixture ofmono-, diand tri-methylamines. Curve B: chromatogram of the amines present in an acid extract ofthe plant, showing the presence of only ammonia and trimethylamine. (Column length, 4ft.; liquid phase, hendecanol-iS% liquid paraffin (v/v); temp., 78 50; flow rate of nitrogen, 5.7 ml./min.; nitro...

We describe a sensitive, simple technique for determining urinary oxalate. Urine, diluted as necessary with distilled water, is injected into an ion chromatograph. Oxalate is detected conductimetrically as a distinct peak near the tail of the chromatogram. This peak specifically represents oxalate, because it is abolished if the sample is treated with oxalate decarboxylase. We have used this te...

Department of Organic Chemistry II, Unive P.O. Box 644, 48080 Bilbao, Spain Departamento de Śıntesis y Estructura de Bi y Catálisis Homogénea (ISQCH), Universida Servicio de Resonancia Magnética Nuclear, C (CEQMA), Universidad de Zaragoza, CSIC, † Electronic supplementary information procedures and characterization of all NMR spectra and HPLC chromatogram Cartesian coordinates of all stationary...

During the evaluation of the continuous measurement signal of analytical instruments by a digital computer, the signal is sampled periodically, and the analytical information [1] is computed from this sequence of discrete values representing the signal by the procedure called data reduction [2]. For example, retention data, peak heights and/or peak areas are produced from the raw discretized si...

The commercially available pullulan (Pullulan PI-20) has a purity of more than 90 %. Its average molecular weight (at peak of a gel permeation chromatogram) is about 200 kD. The main impurities are mono-, diand oligosaccharides, which are carried over from the raw material (hydrolysed starch) into the final product. The specifications for Pullulan include standard parameters for identification ...