Plasma was subjected to methylene blue (MB) photochemical virus inactivation using the Maco Pharma Maco-Tronic system which allows three units to be illuminated together, thus reducing processing time. The plasma bag system used incorporates an integral membrane plasma filter and a dry MB pill which dissolves in the plasma to give a 1-microM concentration. There is computer-controlled processing and datalogging. In an assessment of 10 pools of Group A plasma, the losses of coagulation factors, following MB/light treatment, were 23% fibrinogen, 10% FV, 26% FVIII, 11% FIX and 13% FXI. Group O, Group B and Group AB plasmas were not tested. Von Willebrand factor (vWf) multimers showed no substantial change when treated with MB, and no losses were seen for antithrombin III (ATIII), protein C and vWf:Ag. Measurements of C3a, C5a, prothrombin fragment 1+2 and FXIIa indicated that there was no activation as a result of filtration.
A sensitive colorimetric method has been developed for the determination of trace amounts of sulphide in condensed steam. For precise work the colour produced by"-diethyl-p-phenylenediamine in the presence of iron ( 111) ions is measured spectrophotometically covering the range 0-5 to 100,xg of sulphide-sulphur; the standard deviations a t the 100 and I.O-,xg levels are about 3 and 0.08 pg, respectively. Reasonably accurate results over the range 0.5 to 25 ,ug of sulphide-sulphur can be obtained "on site" by a simple visual titration of a reference solution with a methylene blue solution. The NN-diethyl-p-phenylenediamine was shown to be superior to the dimethyl homologue normally used, and its use does not appear to have been reported previously. Methods of sampling and the effect of sulphite are also discussed.
When cryoprecipitate is prepared from plasma which has been treated with methylene blue plus light (MB) for the purpose of virus inactivation, clottable fibrinogen content is 40% lower compared with units prepared from untreated plasma. Initial studies showed that when frozen MB plasma units were removed to +2 to +6 degrees C for 4 h and then returned to -40 degrees C prior to cryoprecipitation, fibrinogen recoveries increased from 24 to 42%. Although fibrinogen yield improved when plasma units were stored at +2 to +6 degrees C for varying lengths of time, FVIII levels decreased with increasing time. Conditioning for 8 h was studied in more detail. Groups of two plasma units were mixed together, divided into two equal units, frozen/thawed and treated with MB. One of each pair was stored continually at -40 degrees C, whereas the other was removed to +2 to +6 degrees C for 8 h. Samples were assayed for fibrinogen, FVIII, VWF:Ristocetin cofactor activity (RCo), VWF:Ag and VWF:Collagen binding (CB). The cryoprecipitate fibrinogen content increased to a mean of 207 mg unit(-1). VWF:Ag, VWF:RCo and VWF:CB recoveries also increased. FVIII recovery decreased from 50 to 45% (mean 124 iu unit(-1)). Conditioning has been validated for routine production of cryoprecipitate from imported plasma.
The moisture content of a fertiliser as manufactured has a significant effect on its tendency to cake during storage. The lower the moisture content the better, but on the other hand any unnecessary drying leads to extra costs in manufacture, and therefore a rapid, reliable and accurate method for the determination of moisture is necessary. Of those available, titration with Fischer reagent is of the most general application; oven drying, for example, cannot be used with fertilisers containing ammonium nitrate. To ensure complete reaction with the reagent the fertiliser must be finely ground and it is, of course, essential that the grinding be carried out with neither loss nor gain of moisture. An apparatus has been designed and constructed that enables grinding of the fertiliser and titration of the moisture to be completed in a single vessel. Grinding is effected under methanol by a high-speed cutter and the Fischer reagent is then added automatically, the end-point being detected by a sensing electrode. Electronic valves were used in the original apparatus, but a transistorised version has now been made, which is compact and more convenient for laboratory use. Although designed primarily for the examination of fertilisers the apparatus can be used for determining moisture in any solid that is insoluble in methanol; it has been found useful for determining trace amounts of water in oils. The method and the apparatus are the subject of U.K. Patent No. 1,021,745 granted to Imperial Chemical Industries Limited.
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