Direct determination of calcium and phosphorus in mineral supplements for cattle by wavelength dispersive X-ray fluorescence (WD-XRF)

The current study describes a simple and rapid method for the direct determination of Ca and P in mineral supplements for cattle by wavelength dispersive - X-ray fluorescence (WD-XRF). For calibration, solid standards obtained through a set of reference materials (RMs) of mineral supplements for cattle with concentrations of Ca ranged from 120 to 223 g kg− 1 (r = 0.9809) and P ranged from 29 to 95 g kg− 1 (r = 0.9957) were used. For Ca, the matrix-matching using the RM 18/03 diluted in Na2CO3: NaCl (1:1 w/w) in the range of 0-204 g kg− 1 (r = 0.9975) was also used as calibration strategy. The proposed method presented limits of detection of 47 mg kg− 1 for Ca and 36 mg kg− 1 for P using calibrations with RMs and 61 mg kg− 1 to Ca using matrix-matching calibration strategy. Accuracy was assessed by the analysis of four RM of mineral supplements for cattle. A statistical evaluation using student's t-test showed that there is no significant difference between the value obtained with the proposed method and the certified value, at 95% confidence level. The method was successfully applied and is a good alternative to conventional acid digestion routine analysis for determination of Ca and P in mineral supplements for cattle.