Sample Treatment Approaches for Trace Level Determination of Cesium in Hepatitis B Vaccine by Suppressed Ion Chromatography

The hepatitis B surface antigen manufactured by recombinant DNA technology is extracted from the culture media by density gradient centrifugation using cesium salts. Cesium is considered to be toxic, because it affects active ion transport by blocking potassium channels. The residual trace levels of cesium in hepatitis B vaccine samples are determined by suppressed ion chromatography. Hepatitis B vaccines contain various buffer salts, aluminum-containing adjuvants, proteins and traces of iron. The polyvalent cations (Al³⁺, Fe³⁺) and proteins degrade the chromatographic performance in terms of decreased retention time and poor reproducibility. Different sample preparation approaches were evaluated with the aim of eliminating these foulants: (1) filtration, (2) digestion and (3) digestion-protein precipitation. Quantitative elimination of these foulants was achieved in the digestion-protein precipitation sample clean-up approach. Cesium was separated on the IonPac CS17 column with suppressed conductivity detection. The results of the ion chromatography (IC) method were compared with ICP-MS analysis. The precision of determination was better than 6.5% (relative standard deviation) with a method detection limit of 45 ng mL⁻¹. The expanded uncertainty in the measurement at 95% confidence level (coverage factor 2) is better than 16.3%.

     

Determination of trace phosphorus in zirconium-niobium alloy and Zircaloy by UV-vis spectrophotometry

A spectrophotometric method has been developed for the determination of traces of phosphorus in zirconium based alloys (Zr-2.5Nb and Zircaloy). It is achieved by selective fluoride complexation controlled by boric acid. The samples were dissolved in HF and fluoro-complexes of the matrices were formed by maintaining the concentration of HF while the excess HF was controlled by boric acid. After the formation of phosphomolybdate, extracted into n-butyl acetate, ion-associated with crystal violet and the absorbance was measured at 582 nm. The results obtained by this procedure were in close agreement with the certified reference material (CRM) values and further these values were compared with the values determined by Glow Discharge-Quadrupole Mass Spectrometry (GD-QMS). The potential interferences like fluoride, silicon, arsenic(V), niobium, titanium, tantalum, etc., were tolerable to large level. LOD (3 s) was found to be 0.055 mg kg(-1) with a precision (R.S.D.) of 2-3% and molar absorptivity was 2.7x10(5) L mol(-1) cm(-1).     

Development of an In Situ Evaporation System for the Preconcentration of Anionic Impurities in High Purity Water

A simple, inexpensive dual vessel evaporating system has been developed to avoid contamination that may arise from the laboratory environment. A 200-fold preconcentration was achieved by the evaporation of 100 mL Milli-Q water on a water bath for 6 h and subsequent analysis was carried out by ion chromatography (IC). The detection limits achieved were 1, 2 and 11 ng L^?1 for fluoride, chloride, and nitrate, respectively. Accuracy, based on spiked recovery data, was 93–103% and precision, in terms of relative standard deviation on five replicates, ranged from 4 to 7%.     

Determination of traces of chloride and fluoride in H2SO4, H3PO4 and H3BO3 by in situ analyte distillation-ion chromatography

A simple dual vessel in situ analyte distillation (IAD) system has been developed for suppressed ion chromatographic determination of chloride and fluoride ions in complex matrices. In IAD system, water vapours generated from the outer vessel reacts with sulfuric acid generating heat, thus favouring the quantitative distillation of chloride and fluoride within 30 min on water bath temperature (approximately 80 degrees C). The distilled analytes, as their respective acids in water, were directly injected into an ion-chromatograph. This newly developed method has been applied for analysis of trace impurities in H2SO4, H3PO4 and H3BO3. The detection limits for chloride is 8, 80 and 70ppb (w/w) for H2SO4, H3PO4 and H3BO3, respectively. For fluoride the detection limits are 6 and 60 ppb (w/w) for H2SO4 and H3PO4, respectively. The recovery of spikes for both the analytes ranged between 87 and 100%.