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PubMed · 8369364

Calibrators and control samples for bilirubinometers.

B G Blijenberg·G Brügmann·W J Geilenkeuser·R Kusyschyn·G Röhle·H Schlebusch·C Schneider
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Abstract

The different matrix properties of neonatal serum and commercial control samples can lead to considerable errors in the calibration and control of bilirubinometers. These difficulties can be avoided by calibration with serum from healthy adults which is supplemented with unconjugated bilirubin. But this procedure is impracticable for most routine laboratories. Under certain preconditions, control samples, with bilirubin concentrations determined with correctly calibrated bilirubinometers or spectrophotometers, are also suitable as calibrators. This was established by determination of the bilirubin concentration of 16 different control samples, using both the reference method and correctly calibrated bilirubinometers or spectrophotometers in three or four specialist laboratories. This was also confirmed in several interlaboratory surveys, some involving up to 72 laboratories. The results of these investigations show that a control sample should be used for the calibration of a bilirubinometer only if it meets the following preconditions: 1. There should be no significant difference between the bilirubin values determined with the reference method and with a correctly calibrated spectrophotometer or bilirubinometer. 2. The bilirubin concentration should lie in the range 230-300 mumol/l. The photometric response of bilirubinometers has a limited linear range, so that analytical results greater than 300 mumol/l must be rated as basically unreliable.

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BilirubinBlood Chemical AnalysisCalibrationHumansInfantInfant, NewbornLaboratories, HospitalNeonatal ScreeningReference StandardsReproducibility of ResultsSpectrophotometryComparative StudyJournal ArticleMulticenter Study

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B G Blijenberg, G Brügmann, W J Geilenkeuser, R Kusyschyn, G Röhle, H Schlebusch, C Schneider. 1993. Calibrators and control samples for bilirubinometers.. https://doi.org/10.1515/cclm.1993.31.6.367

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Solvent partition of 14C-unconjugated bilirubin to remove labeled polar contaminants.

Polar derivatives contaminating unconjugated bilirubin (UCB) are customarily extracted with weak alkali. As UCB degrades rapidly at alkaline pH, regeneration of polar derivatives may limit purification. This problem is especially important when trying to eliminate radiolabeled contaminants from 14C-UCB. As polar derivatives of UCB should have a much greater aqueous to CHCl3 partition ratio (PR) than UCB even at neutral pH, where degradation of UCB is minimal, 14C-UCB in CHCl3 was serially extracted with an aqueous buffer at pH 7.0 to determine whether labeled derivatives could be preferentially removed. A single extraction of customarily purified 14C-UCB removed 0.18+/-0.06% of the radioactivity as labeled derivatives. Subsequent serial extractions yielded a stable, 67% lower 14C-PR with only 0.03% of radioactivity as labeled derivatives. Reverse-phase high-performance liquid chromatography (HPLC) of phases from later extractions revealed, however, that up to 1.1% of the disintegration per minute (dpm) in CHCl3 phases and up to 50% in aqueous phases were polar impurities. HPLC of partition phases spiked with purified 14C-UCB revealed that these impurities derived from incomplete extraction of the least polar impurities and their regeneration during HPLC. In the dark under argon, 14C-UCB in CHCl3or dimethyl sulfoxide (DMSO) solution degraded very slowly to polar derivatives. Extraction of impurities from a solution of 14C-UCB in CHCl3 is best done using pH 7.0 buffer, with removal of over 80% of the labeled contaminants remaining after customary purification by alkaline extraction.

Bilirubin↗