A new Method of preparing Nitrogen Samples from Haem for Mass Spectrometric Isotope Analysis [antikvár]

Haematohgia 4 (J), pp. 21—26 (1970) A New Method of Preparing Nitrogen Samples from Haem for Mass Spectrometric Isotope Analysis I. CoRNiDES, Hedvig Medzihradszky, I. Bernát Mining, Institute for Organic arian Army Medical Corps, Bi (Received August 27, 1969) Hungarian Research Institute for Mining, Institute for Organic Chemistry of Eötvös Loránd University, and Hungarian Army Medical Corps, Budapest, Hungary The life span of a select population of the red cells formed in the bone marrow after thermal injury was studied by means of the "N stable isotope tracer technique. The adequacy of this method depends on the suitable preparation of nitrogen samples from haem for isotope analysis. A new procedure has been worked out for this purpose utilizing oxidation by cupric oxide in high vacuum at a temperature of about 600 °C. Being much less time consuming and at the same time reasonably accurate, the procedure is superior to the methods hitherto used. Determination of the concentration of the heavy nitrogen isotope in the circulating haem after administering glycine labelled with makes it possible to estimate the rate of haemoglobin production and the life span of the red cells. The curve obtained can be divided into three main portions, viz. a rapid rise in labelling over the first few days followed by a plateau and finally a descending portion corresponding with the isotope's disappearance from the blood haem. This last phase indicates the destruction and elimination of the red cells the labelling of which had presumably occurred in the bone marrow during the administration of the labelled glycine [7]. The method is based on the principle of building the label into the erythrocytes during their development, consequently in the labelling of a select population. The investigation involves two separate procedures. First, the whole nitrogen content of the haem is liberated in elementary, i.e. gaseous, form. This is then followed by isotopic analysis by mass spectrometry. Mass spectrometric isotope analysis has developed into a routine practice and if its different sources of error [ 1 ] are minimized it ensures an accuracy of + 0.01% or less. Accuracy and speed of the method are considerably influenced and in many cases severely restricted by the procedure of preparing the sample in a suitable form for introduction into, and ionization in, the mass spectrometer ion source. In our case the procedure means the liberation of the nitrogen of a complex and stable compound, of the haem, in elementary gaseous form ensuring the preservation of the nitrogen isotope ratio of the compound and the elimination of impurities adversely affecting the reliability of the mass spectrometric analysis. In a similar investigation James et al. [2] used the two step procedure described by Rittenberg [3], consisting of conversion of organic nitrogen to ammonia Haematologia 4, 1970