On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultraviolet radiation |
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Authors: | Email author" target="_blank">I?FridolinEmail author L?-G?Lindberg |
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Institution: | 1.Department of Biomedical Engineering,Link?ping University,Link?ping,Sweden |
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Abstract: | The aim of the study was to assess the wavelength dependence of the UV absorbance during monitoring of different compounds
in the dialysate. UV absorbance was determined by using a double-beam spectrophotometer on dialysate samples taken at pre-determined
times during dialysis, over a wavelength range of 180–380 nm. Concentrations of several removed substances, such as urea,
creatinine, uric acid, phosphate andβ
2-microglobulin, were determined in the blood and in the spent dialysate samples using standard laboratory techniques. Millimolar
extinction coefficients, for urea, creatinine, monosodium phosphate and uric acid were determined during laboratory bench
experiments. The correlation between UV absorbance and substances both in the dialysate and in the blood was calculated at
all wavelengths. A time-dependent UV absorbance was determined on the collected dialysate samples from a single dialysis session
over a wavelength range of 200–330 nm. The highest contribution from observed compounds relative to the mean value of the
absorbance was found around 300 nm and was approximately 70%. The main contribution to the total absorbance from uric acid
was confirmed at this wavelength. The highest correlation for uric acid, creatinine and urea was obtained at wavelengths from
280 nm to 320 nm, both in the spent dialysate and in the blood. The wavelength region with the highest correlation for phosphate
andβ
2-microglobulin, with a suitable UV-absorbance dynamic range, was from 300 to 330 nm. In the wavelength range of 220–270 nm
the highest absorbance sensitivity for the observed substances was obtained. A suitable wavelength range for instrumental
design seems tobe around 290–330 nm. The relatively high correlation between UV absorbance and the substances in the spent
dialysate and in the blood indicates that the UV-absorbance technique can estimate the removal of several retained solutes
known to accumulate in dialysis patients. |
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Keywords: | Haemodialysis Dialysis monitoring Absorption Spectrophotometry Ultraviolet Absorbance Spent dialysate |
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