Application of an integrated matrix-assisted laser desorption/ionization time-of-flight, electrospray ionization mass spectrometry and tandem mass spectrometry approach to characterizing complex polyol mixtures.

Polyols are being used in a wide range of industrial applications including surfactants and precursors for grafted polymers. The characterization of polyols is of significance in correlating compositions and structures with their properties. We illustrate two real world examples where traditional analytical methods including GPC and NMR failed to reveal compositional differences, but the combination of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), electrospray ionization mass spectrometry (ESI MS), and MS/MS can produce compositional information required for problem solving. The first example involves failure analysis of four ethylene oxide and propylene oxide (EO/PO) copolymer products. The results from the mass spectrometry analysis unequivocally demonstrate that one of the samples has a small variation in copolymer composition, leading to its abnormal activity. The second example is in the area of deformulation of complex polyol mixtures. Two samples displaying similar properties and activities were found to be two different polyol blends. One of the samples is a more cost-effective product. These examples demonstrate that MALDI, ESI MS, and MS/MS should be seriously considered as an integrated component of an overall polyol characterization program in product failure analysis and deformulation.

Effects of matrix-assisted laser desorption/ionization experimental conditions on quantitative compositional analysis of ethylene oxide/propylene oxide copolymers.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has the potential to become a valuable tool for the compositional analysis of copolymers. For a copolymer composed of structurally very similar building blocks with minor chain length changes, one would expect the relative peak intensities observed in the MALDI mass spectra to reflect its composition, at least within a narrow mass range. However, we show that variations in experimental conditions in MALDI can have a significant effect on the mass spectral appearance of a copolymer. The effects of concentration, laser power, type of matrices and solvents on mass spectra of an ethylene oxide/propylene oxide copolymer are illustrated. These somewhat surprising results show that great care needs to be exercised when interpreting copolymer spectra for compositional analysis, even for copolymers with structurally similar monomers. This work also points out that further studies are needed to better understand and optimize spectral acquisition conditions for reliable copolymer compositional analysis by MALDI.

Bart's hydrops fetalis--clinical presentation and management--an analysis of 25 cases.

Twenty-nine hydropic infants were born in the Kandang Kerbau Hospital between 1980 and 1985, during which there were 131,658 deliveries, giving an incidence of 1 in 4,540 total births. Twenty-five of these cases were confirmed to be due to homozygous alpha thalassaemia. No case of fetal hydrops due to Rh isoimmunization was detected. The mean age of the mothers was 28.86 +/- 4.05 years (+/- SD). Eight patients had delivered 1 hydropic baby previously while 1 had a history of 2 babies with hydrops fetalis; 92% of the patients had been followed antenatally while 8% were first seen when they were admitted in labour; 25% of the patients had anaemia, 52% had polyhydramnios, 20% developed hypertension and 64% had bilateral lower limb oedema. None of the patients had concomitant hypertension, generalized oedema and proteinuria. In 4 cases of recurrent hydrops, serial ultrasound scans were performed from early pregnancy but ultrasonic features of hydrops fetalis were only seen from 27 weeks' gestation. Spontaneous labour occurred in 75% of patients at a mean of 32.3 +/- 3.3 weeks (+/- SD). All delivered vaginally and only 1 patient required abdominal decompression. Four patients required Caesarean section, 2 for failure to progress after induction of labour, 1 for major placenta praevia and the fourth for fetal distress; in the last case, diagnosis of hydrops fetalis was only made after delivery of the baby. All the babies in the series died within one hour of delivery. Homozygous alpha thalassaemia is the commonest cause of hydrops fetalis in Singapore and is an invariably fatal condition. It is associated with an increased incidence of maternal anaemia, polyhydramnios and prematurity.