Determination of pipecolic acid in urine and plasma by isotope dilution mass fragmentography.

Pristanic acid and phytanic acid in plasma from patients with peroxisomal disorders: stable isotope dilution analysis with electron capture negative ion mass fragmentography.

A sensitive and selective stable isotope dilution method was developed for the accurate quantitation of pristanic acid and phytanic acid using electron capture negative ion mass fragmentography on pentafluorobenzyl derivatives. This technique allows detection of 1 pg of each compound and was applied to plasma from healthy controls and patients suffering from various peroxisomal disorders. The a...

Determination of cadmium and lead in urine by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry.

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of Cd and Pb in urine samples. The isotope ratios for each element in each analytical run were calculated from the peak areas of each isotope. A relatively low vaporization temperature was used, which separated the analyte from the major matrix components an...

Determination of plasma bile acids by capillary gas-liquid chromatography-electron capture negative chemical ionization mass fragmentography.

Combined capillary gas-liquid chromatography-electron capture negative chemical ionization mass spectrometry of pentafluorobenzyl ester-TMSi ether derivatives of bile acids and isotope dilution using deuterated internal standards are introduced as a sensitive and selective analysis technique for plasma bile acids. As a result of the high ionization efficiency of pentafluorobenzyl derivatives un...

Accuracy of a fully enzymatic method for creatinine, as judged by isotope dilution-mass fragmentography.

Assay of 1,25-dihydroxy vitamin D3 by isotope dilution--mass fragmentography.

We describe a specific assay of 1,25-dihydroxy vitamin D3 in human serum, based on isotope dilution-mass fragmentography. We added [26-2H3]-1,25-dihydroxy vitamin D3 to a fixed amount of serum. The steroids were extracted with chloroform/methanol and purified by liquid chromatography. The purified materal was converted into the trimethylsilyl ether and analyzed. Unlabeled 1,25-dihydroxy vitamin...