Measurement of plasma tyrosine by HPLC-UV or LC-MS-MS for assessing chemically induced tyrosinaemia

Certain chemicals can cause a marked increase in the levels of the amino acid tyrosine in plasma (tyrosinaemia). An HPLC-UV method involving the removal of plasma proteins using a simple ultrafiltration device was developed here and has been in use for a number of years. This has now been adapted to LC-MS-MS and this has resulted in great improvements in productivity. Validation data are presented for both methods over the relevant range of 5–500 μg mL⁻¹ Although a low level of detection is not required, HPLC-MS-MS analysis presents a great advantage in sample throughput and improved cost effectiveness with no obvious disadvantages.