Development and Verification of a Suspension-Based TXRF Method for Chromium Determination in Feed and Fecal Samples...

In the present study, a rapid method based on total reflection X-ray fluorescence (TXRF) was developed to determine chromium in feed and fecal samples, containing chromic oxide. The method uses suspension sample preparation with gallium as an internal standard and does not require chemical reagents or complete sample digestion. Key parameters affecting performance, such as particle size, sample concentration, and acquisition time, were optimized to ensure stable signals and reliable quantification. The method showed a limit of quantification of 24 µg g^-1 for Cr₂O₃ and good precision (relative standard deviations of 3-7% for both feed and fecal samples), at Cr₂O₃ concentrations in the range of 20-50 mg kg^-1. These performance characteristics meets the requirements for digestibility studies. It requires only small sample quantities with minimal preparation. The developed method is suitable for routine analysis, particularly in studies generating large numbers of samples. The accuracy of the method was confirmed through agreement with results obtained using an independent method based on inductively coupled plasma optical emission spectrometry (ICP-OES) after acid digestion. The scatter plot analysis of the results obtained by both methods showed a linear regression line with a slope of 0.978 and a correlation coefficient (R²) of 0.9559, indicating good agreement. The p-value from the paired t-test performed was greater than 0.05, suggesting that the observed differences between paired measurements are not statistically significant at the 95% confidence level. The Bland-Altman analysis demonstrated negligible systematic deviation between the two methods.