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Biomedical subjects

B Michalke

Publications and source records attributed to B Michalke.

25 records · Page 2Linked to original sources
PubMed1996

Capillary electrophoresis - a useful tool in speciation investigations.

1. CE is shown as a tool for a more-dimensional identification of organic metal binding partners. Methods are given for a further improvement of the identification security of the organic ligands [1], when analyzing molecules of nearly equal mobility. CE is used here as a powerful tool for quality assurance and quality control in speciation investigations.2. Methods are presented for a direct separation and identification of different species. As an example, seleno organo compounds are separated from their sulphur analogues in model solutions and native samples. Standard addition methods [1, 2] as well as UV spectra of both species help to identify these molecules as seleno- or sulphur-organo compounds. Further methodological developments and separations are shown for Pt-compounds.

Journal Article↗
PubMed1996

Separation of free iodide from other I-species in human serum - Quantification in serum pools and individual samples.

A method for the determination of free iodide in human serum has been developed. Iodide from pooled serum samples has been separated from the organic matter by SEC, subsequently freeze-dried and analyzed by ion chromatography. Investigations for recovery and precision have been carried out and provided sufficient results. For quality assurance ICP-MS has been taken additionally as a total I-detector. The iodide results of ICP-MS agree well with IC values. Iodine containing SEC- fractions from iodide-spiked samples has shown no increased I-values except that in the iodide fractions, proving that there has been no iodide conversion into other I-species (and vice versa) during the whole procedure. Free iodide from two serum pools of different healthy persons has been determined as 2.25 and 2.43 microg I(-)/l, respectively. The values are related to total iodine levels determined by ICP-MS. For comparative reasons a table of individual iodine and iodide values is presented.

Journal Article↗
PubMed1995

Capillary electrophoretic methods for a clear identification of selenoamino acids in complex matrices such as human milk.

Selenoamino acids from size-exclusionchromatographic fractions of human milk were identified and determined by capillary electrophoresis (CE). For this purpose, different CE methods were developed to separate these selenoamino acids from other molecules with similar molecular masses. Methods were introduced for the clear identification of the analytes. These methods were designed to allow the identification of selenoamino acids in spite of the presence of many molecules with similar mobilities. Further, they overcome identification problems caused by shifts of migration times (due to different ionic compositions) compared with standard solutions.

Electrophoresis, Capillary↗
PubMed1991

Contribution to Zn-speciation in human breast milk: fractionation of organic compounds by HPLC and subsequent Zn-determination by DCP-AES.

Human milk was collected between the 2nd and 7th day after delivery from different women, pooled and separated into fat, proteins and low molecular weight (LMW) substances by centrifugation. The fatty share was rejected, the remaining two fractions were further separated by size exclusion chromatography (SEC) as described in (1), and analyzed for zinc (Zn). The HPLC-method was checked for stability of organo-metal complexes. Only bi-distilled water served as mobile phase during HPLC in order to maintain the Zn/organic molecule-complex intact and to avoid unnecessary contamination sources. Among milk proteins, zinc was associated with casein, albumin, lactoferrin, and metallothionein, whereas among LMW substances a zinc peak could be observed exclusively with citrate. The identity of citrate and proteins was verified with comparable HPLC runs of standard solutions, by citrate-specific examination of HPLC fractions and by isoelectric focusing (IEF) of collected HPLC fractions. Furthermore, native human milk, as well as fractions of proteins and LMW substances (with and without HPLC separation), were quantified with regard to total content of zinc, protein and citrate. No loss of substances was found. In human milk, zinc is primarily bound to citrate (approximately 3200 micrograms/L of Zn in pooled human milk = 95%), and only about 5% of the total amount of zinc is attached to proteins (approximately 150 micrograms/L of Zn in pooled human milk). Determination of citrate content in human milk used in this study yielded values approximately twice as high as data cited in the literature (325-655 mg/L compared with 95-270 mg/L, (2,3)).(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1990

Protein fractionation and Cd-speciation in human breast milk by HPLC and voltammetry.

A method for preparative separation of proteins from human breast milk was developed, which preserved the intactness of metal-protein complexes as well as keeping the sample injection and fraction harvesting free of Cd-contamination. Preliminary, incomplete separation was performed on a TSK 60 x 4 mm ID column, in order to check the retention time of the Cd-protein complex in relation to the elution times of protein standards. The Cd-profiles were determined by DPASV (differential pulse anodic stripping voltammetry) and showed concentrations below 100 ng/L (detection limit) except in the fraction 55-59 min, where about 1 microgram/L of Cd in human milk was determined. This Cd-elution time was in accordance with the retention of the metallothionein (Mt) standard (57 min) of the above mentioned column. Further attempts to identify the protein nature of the Cd-species were carried out by isoelectric focusing. The "Mt-fraction" of breast milk was focused and the resulting distribution profile compared to the profile of the Mt-standard. Good correspondence was achieved. Further investigation will be based on the use of a more efficient column (TSK 1000 x 8 mm ID) for separation and further identification of the Cd-species.

Cadmium↗
PubMedDate not supplied

[Mineral analysis of roentgenologically defined calcifications in patients with chronic calcifying tendinitis of the rotator cuff].

AIM: Extracorporeal shockwave application (ESWA) is in clinical use to promote disintegration of symptomatic calcifications of the rotator cuff of the shoulder. However, disintegration of roentgenologically comparable calcifications of the rotator cuff is not always successfull. It is known from urologic stone lithotripsy that the susceptibility for disintegration of stone-like concrements depends on their mineral content. Therefore, in the present investigation the relative contents of calcium and phosphorus in rotator cuff calcifications were determined. METHOD: 39 surgically removed rotator cuff calcifications were analyzed by means of atomic emission spectrometry. RESULTS: The relative content of calcium of the rotator cuff calcifications was found to be 22.3 % +/- 5.7 % (mean +/- SD; 6.8 % - 32.4 %), that of phosphorus as 10.5 % +/- 2.4 % (2.7 % - 14.4 %). The data neither depend on the gender of the patients nor on their age at the time point of surgical removal of the rotator cuff calcifications. CONCLUSION: Roentgenologically comparable calcifications of the rotator cuff demonstrated distinct individual differences concerning the relative contents of calcium and phosphorus. The present results may serve as the first indication that the susceptibility of rotator cuff calcifications for disintegration may depend on their relative contents of calcium and phosphorus.

Adult↗