Improvements to a high-performance liquid chromatographic assay for allopurinol and oxipurinol in plasma

A simple method for quantification of allopurinol and oxipurinol in human serum by high-performance liquid chromatography with UV-detection

“…Previously, it was suggested to use ammonium sulfate for precipitation instead of a strong acid solution (perchloric acid as in our method or trichloroacetic acid as described by Kramer et al [22]), because it was found that the low pH of the injected samples could shorten column life [26]. Recently, Tada et al did not find any column deterioration using acidic samples and a buffered mobile phase (100 mM potassium phosphate; pH 4.0) [14].…”

Simultaneous analysis of allopurinol and oxypurinol using a validated liquid chromatography–tandem mass spectrometry method in human plasma

“…Generic PPT has been the technique of choice for quantitative recovery of AP and OP from biological samples as documented in several reports [3] , [9] , [20] . Two other methods report combined use of PPT and LLE [8] , [13] ; however, the details of extraction procedure were not presented in one of the methods [13] .…”

“…Thus, to have a simple and rapid method for sample preparation from plasma matrix, PPT was tested with common precipitants like acetonitrile, methanol and also with different acids like trichloroacetic acid (TCA), perchloric acid and FA. There have been some issues in published reports related to reduction in column efficiency due to direct injection of acidic supernatants, especially when using TCA as the precipitant and therefore it is recommended to neutralize the acid with ammonium sulfate [20] . Although the recovery was reduced to some extent due to neutralization, a similar approach was adopted after PPT with 20% TCA.…”

Facile and rapid high-performance liquid chromatography method for simultaneous determination of allopurinol and oxypurinol in human serum

“…It has often claimed that direct injection of serum or plasma onto HPLC columns causes column deterioration. Chang and Kramer reported that injections of acidic supernatant after precipitation of the protein with 20% trichloracetic acid caused column deterioration, and recommended neutralization using an excess of ammonium sulphate (18). However, recovery of AL (0·4–40 μ g/mL) and OX (40 μ g/mL) after neutralization was found to be low (89–96%) (19).…”