Determination of platinum levels in serum and urine samples from pediatric cancer patients by TXRF

Abstract

A simple total reflection x‐ray fluorescence (TXRF) procedure was developed to monitor plasma drug levels and urine elimination in pediatric cancer patients undergoing chemotherapy with platinum‐containing drugs. Serum and urine specimens were irradiated with cut‐off filtered or monochromatized x‐rays using an easy procedure that avoids sample digestion. Specimens from normal patients were standardized by adding known trace amounts of elements absent in these matrices and diluting to 1 : 1 in water. These were used to derive TXRF spectrometer sensitivity curves relative to cobalt as internal element standard and to the incoherently scattered Compton peak as internal standard. Accuracy, precision and detection limits attained in the analysis of minute amounts of unknown serum and urine, treated in the same manner as the standardized samples, are shown to be appropriate for routine monitoring of platinum in cancer patients. Copyright © 2000 John Wiley & Sons, Ltd.

Direct analysis of biological samples by total reflection X-ray fluorescence

“…The self-absorption and scattering must be minimized by an adequate sample preparation [11][12][13][14][15][16][17][18][19][20][21][22], e.g., microtomes, slurries, dilution, etc. and drying procedure.…”

“…The dependence of the analytical results on the sample matrix, when the incoherent peak is used as an internal standard was overcome using a sample spiked with known amounts of those elements non-existing, or existing in the sample at negligible concentrations as calibration standards [17,22]. After the normalized sensitivities are found, a fitting of the curve of sensitivity with a second or third order polynomial permits us to obtain all the values of sensitivities in the selected range of Z, and to interpolate the calibration curve to include sensitivity values for the elements of interest in the sample.The use of the described method of Compton peak standardization is restricted to samples with low variability in their matrices.…”

“…After the normalized sensitivities are found, a fitting of the curve of sensitivity with a second or third order polynomial permits us to obtain all the values of sensitivities in the selected range of Z, and to interpolate the calibration curve to include sensitivity values for the elements of interest in the sample.The use of the described method of Compton peak standardization is restricted to samples with low variability in their matrices. This can be tested by determining the ratio of an internal standard to the Compton peak [17,22] and evaluating the relative standard deviation for a representative number of samples. The procedure has been applied to serum samples in the determination of Fe, Cu, Zn and Se in the study of cancer diagnosis methods [31,34], the determination of Pt [17,22] for the evaluation of drug levels and in some tissues like brain for the determination of Cu and Zn [18].…”

“…Direct analysis by itself, or combined with in situ preparation procedures, is a suitable alternative for the quantitative determination of trace elements by TXRF in clinical samples as serum [22], whole blood [19], human brain [17], amniotic fluid [23] and lyophilized tissues [24]. The latter brings about a series of advantages, namely, reduction of analysis time and sample handling, the use of scarce samples and minimization of contamination and analyte losses.…”

Atomic spectrometry update. Clinical and biological materials, foods and beverages

“…Greaves et al 188 used XRF to determine Pt in both serum and urine from paediatric patients treated with Pt drugs. Kadhim et al 57 developed a method for in vivo quantitative determination of Pt in kidneys of patients receiving Pt drugs.…”