Highly Isoselective Ring-Opening Polymerization of -β-Butyrolactone: Access to Synthetic Poly(3-hydroxybutyrate) with Polyolefin-like Material Properties.

We report the highly isoselective ring-opening polymerization (ROP) of racemic β-butyrolactone (β-BL) using -generated catalysts based on Y[N(SiHMe)](THF) and salan-type pro-ligands. The catalyst system produces isotactic poly(3-hydroxybutyrate) (PHB) with record productivity (TOF up to 32 000 h) and the highest isoselectivity ( up to 0.89) in ROP of β-BL achieved to date.

Absolute content determination by quantitative NMR (qNMR) spectroscopy: a curious case of aldosterone.

Quantitative NMR spectroscopy has been utilized to calculate the absolute content (g g) of aldosterone, which is necessary for electrolyte balance and blood pressure regulation, in commercially available materials. Explanations have been provided for many signals observed in the HNMR spectrum, false interpretation of which can have significant effects if such a value is utilized for the primary calibrators in ID-LC-MS/MS ('gold standard') reference methods in clinical chemistry.

Quantitative NMR (qNMR) spectroscopy based investigation of the absolute content, stability and isomerization of 25-hydroxyvitamin D2/D3 and 24(R),25-dihydroxyvitamin D2 in solution phase.

Vitamin D is an important parameter, in serum/plasma based diagnostic analysis, for the determination of optimal regulation of calcium and phosphate homeostases in the human body, vital for the monitoring/progression of osteomalacia and rickets. Particularly, the quantification of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D in blood is an excellent indicator for the vitamin D status of a patient. For this purpose, LC-MS/MS methods, based on appropriate vitamin D reference standards, are considered to be 'gold standard' for such measurements.

An isotope dilution LC-MS/MS-based candidate reference method for the quantification of androstenedione in human serum and plasma.

The accurate measurement of androstenedione in human serum and plasma is required for steroid profiling to assure the appropriate diagnosis and differential diagnosis of hyperandrogenism. In this work, we introduce an isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) candidate reference measurement procedure for the quantification of androstenedione in human serum and plasma. The performance of the procedure enables its use in the evaluation and standardization of routine assays and for the evaluation of patient samples to ensure the traceability of individual patient results.

An isotope dilution LC-MS/MS based candidate reference method for the quantification of cyclosporine A, tacrolimus, sirolimus and everolimus in human whole blood.

An isotope dilution LC-MS/MS based candidate reference measurement procedure for the quantification of cyclosporine A, tacrolimus, sirolimus and everolimus in human whole blood is presented to be used for evaluation and standardization of routine assays applied for therapeutic drug monitoring. The assay allows baseline separation of the four immunosuppressive drugs within a total runtime of 9 minutes using a C4 reversed phase column. Sample preparation is based on protein precipitation with zinc sulphate followed by purification with solid phase extraction.