QUANTITATIVE ANALYSIS OF CALCIUM OXALATE STONES BY INFRARED SPECTROSCOPY
1986 Volume 77 Issue 9 Pages 1485-1492
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1986 Volume 77 Issue 9 Pages 1485-1492
Powder samples of 80 upper urinary tract stones composed of weddellite and/or whewellite and apatite, the contents of which had been estimated by thermogravimetry (TG), were analysed with two kinds of the double-beam recording infrared spectrophotometers, 620 MX of Beckman Instruments, Inc. and IRA-2 of Japan Spectroscopic Co. Ltd.. A 1.0mg powder sample was weighed and mixed with 150mg or 100mg KBr to form a pellet. The typical absorption bands of apatite in the region 1100-1000cm-1 and those of calcium oxalate at 1320, 920, 780 and 520cm-1 were selected and their absorbances were measured on the infrared spectra of 64 samples recorded with 620 MX and the infrared spectra of 51 samples recorded with IRA-2 (Fig. 1 and 2). Comparing the absorbances with the contents of weddellite, whewellite and apatite estimated by TG, an attempt was made to determine the percentage of these components by infrared analysis of calcium oxalate stones.
The results are as follows:
1) It was reported by Bellanato and associates7) that there was a direct correlation between the ratio of the absorbance of the band at 780cm-1 to that of the band at 520cm-1 (D780cm-1/D520cm-1) and the ratio of the whewellite content to the total of weddellite and whewellite. However, it was shown in this study that the correlation coefficient between these ratios was-0.54 (p<0.01) when D780cm-1/D520cm-1 was determined on 51 infrared spectra recorded with IRA-2 (Fig. 4).
2) It was reported by Takasaki that there was a good correlation between the ratio of the absorbance of the bands in the region 1100-1000cm-1 to that of the band at 1320cm-1 (Dp/Do) and the ratio of the apatite content to the total of calcium oxalate and apatite. It was shown in this study that the correlation coefficient between Dp/Do where the ratio of Dp to Do was less than 1.0 and the ratio of the apatite content to the total of calcium oxalate and apatite was 0.96 (p<0.01) when Dp/Do was determined with 620 MX in 52 samples and 0.95 (p<0.01) when determined with IRA-2 in 47 samples (Fig. 5).
3) The correlation coefficient between the absorbance of the band at 920cm-1(D920cm-1) and the weddellite content was 0.87 (p<0.01) when D920cm-1 was measured with 620 MX in 35 samples and 0.81(p<0.01) when measured with IRA-2 in 29 samples (Fig. 8).
4) The correlation coefficient between D780 cm-1 and the whewellite content was 0.89 (p<0.01) when D780cm-1 was measured with 620MX in 64 samples and 0.88 (p<0.01) when determined with IRA-2 in 51 samples (Fig. 9). The correlation coefficient between D520cm-1 and the whewellite content was 0.92 (p<0.01) when D520cm-1 was determined with IRA-2 in 51 samples (Fig. 10).
5) The correlation coefficient between the depth (mm) of the band at 780cm-1 and the whewellite content was 0.87 (620 MX, p<0.01) and 0.89 (IRA-2, p<0.01), and that between the depth of the band at 520cm-1 and the whewellite content was 0.92 (IRA-2, p<0.01). Thus it was suggested that the depth of the absorption band was also correlated with the whewellite content in calcium oxalate stones (Fig. 11).
6) Each of the absorption bands in the region 3600-3000cm-1, at 920cm-1, at 780cm-1 and at 670cm-1 was classified into three patterns and scored according to the shape and depth; those characteristic of weddellite were given two points, those characteristic of whewellite were given 0 point and those showing the intermediate shape and depth were given one point (Fig. 3). The total point (Weddellite score) which ranges between 8 and 0 was then compared with the ratio of the weddellite content to the total of weddellite and whewellite (Fig. 12). Since the correlation coefficient b
