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Ultraviolet (UV) absorbance of spent dialysate has been proposed as a method for monitoring hemodialysis efficiency. The contribution of the various uremic toxins to UV absorption, however, needs clarifying. Urea, creatinine and uric acid were measured in blood and dialysate before and during dialysis in 22 maintenance hemodialysis patients. Absorbance was measured in dialysate. High-performance liquid chromatography (HPLC) analyses of dialysate revealed uric acid as the predominant peak. Spent dialysate absorbance decreased, during dialysis, similarly to serum and dialysate urea, creatinine and uric acid. Dialysate urea correlated closely with absorbance, though urea did not contribute to absorbance, which was determined mostly by uric acid. Uric acid and urea removals were very similar. The spectrophotometric Kt/V correlated with spKt/V urea, with slight but significant differences between the two measurements. UV absorbance is determined mostly by uric acid. Absorbance measurements seem suitable as a method for monitoring dialysis efficiency.

In this preliminary study hydrophobic interaction chromatography (HIC) is proposed as a good tool in order to detect conformational changes induced by chemical denaturants in two globular proteins, cytochrome C (Cyt C) and myoglobin (MYO). Alterations in protein structure were manifested chromatographically by reproducible changes in peak heights, retention time, and appearance of multiple peaks. The HIC behavior of the two model proteins denatured by guanidinium thyocyanate (GdmSCN) was investigated, keeping constant various concentrations of urea in the mobile phase in a TSK-Gel Phenyl-5PW column (TosoBiosep). Suitable elution conditions provide evidence of the simultaneous presence of two denatured forms in the case of MYO, and sequential different denatured states of Cyt C. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 293–300, 2003

The effect of seasonal formation/melting process of pack ice on the PCB level of sea water at Gerlache Inlet and Wood Bay (Ross Sea, Antarctica) was investigated during four Italian expeditions, i.e. 1988-89, 1990-91, 1991-92, and 1993-94. Surface sea water samples from Gerlache Inlet and Wood Bay before pack ice melting showed a typical total PCB concentration of 133 pg/l and 120 pg/l, respectively, which increased by a factor of about 1.3 in both sampling sites during pack ice melting. This effect was attributed to the transfer of PCBs contained in the pack ice to sea water, and salinity was used as a tracer to verify this hypothesis. In this respect, pack ice and sea water samples were collected during the 1993-94 Italian expedition, and both salinity (S) and total PCB content were measured. A fairly good agreement was observed between the experimental PCB concentration and the value calculated by the dilution model which was applied to the mixing process between sea and pack ice melting waters. Although this effect seems to be limited in time and space it is nevertheless significant because it happens during summer when biological species have their highest activity.

For the development of an on-column chromatographic method for the simultaneous separation and detection of selenium(IV) and tellurium(IV), their chromatographic behaviours on cation and anion exchangers as well as on multiphase cation- and anion-exchange/reversed-phase columns, have been investigated. The eluent medium consisted of diluted hydrochloric acid at different concentrations and flow-rates. The detection of selenium(IV) and tellurium(IV) was based on post-column derivatization, of the eluted species, with 1,1,3,3-tetramethylthiourea (TMTU). The TMTU concentration, pH and flow-rate was optimized in order to obtain the best sensitivity for both the analytes. The capacity factor value, k′, as well as the charge of the species eluted on the different columns tested, have been obtained for all experimental conditions. It has been demonstrated that the on-column chromatographic separation between selenium(IV) and tellurium(IV) is achievable by exploiting their different elution patterns on ion exchangers. On the basis of peak symmetry and analyte resolution at different concentration ratios, the cation-exchange mode was chosen. Injecting 50 μl of samples, detection limits of 78 and 83 μg/l for tellurium and selenium, respectively were obtained. Concentrations lower than 10 μg/l could be determined by increasing the injection volume or by means of on-line preconcentration.