using 20 microliter deproteinised serum samples for injection , the the detection limits for theophylline and proxyphylline are about 0.040 and 0.055 microgram per ml serum or plasma , respectively , and the corresponding sensitivities are about 0.033 and 0.048 microgram compound for 0.0044 absorbance units at 280 nm .
C0229671
serum
C0032105
plasma