S. P. Srivastava

DIRECT ESTIMATION OF AROMATIC CARBON (Ca) CONTENT OF BASE OILS BY 1H-NMR SPECTROSCOPY

ABSTRACT A direct and fast method for the estimation of aromatic carbon content (Ca) in base oils produced through different processes has been developed based on 1H-NMR spectroscopy. The identity of the complex and overlapped 1H-NMR region of 2.0−3.5 ppm, which constitutes resonances from α-substituents (−CH, −CH2 and −CH3 groups), has been revealed by 2D HetCor spectral analyses. This information has facilitated the estimation of quaternary (Cq) and bridgehead (Cb) aromatic carbons from 1H-NMR spectrum using the derived equations. The complete and unambiguous assignment of the 1H-NMR spectrum led to the estimation of Ca content of base oils. The classical Brown-Ladner (BL) equation for Ca estimation has been modified by taking the actual contribution of −CH, CH2 and CH3 groups, instead of using average values. The proposed 1H-NMR, and the modified BL methods correlate very well (R2 = 0.97) with the standard 13 C-NMR method for Ca estimation.

Perioperative considerations in a sickle cell patient undergoing cardiopulmonary bypass.

An 11-year-old child, a known case of sickle cell anaemia with a history suggestive of sickling crisis in the past was scheduled for surgical pulmonary valvotomy. Pre-operative blood transfusion and hydroxyurea were administered. Pre-operative blood transfusion is indicated in sickle cell disease patients to raise the haematocrit level and lower sickle haemoglobin (HbS) levels. Before the start of cardiopulmonary bypass (CPB), exchange transfusion was performed to reduce HbS level and raise adult haemoglobin level. Hypothermia was prevented by employing normothermic CPB.