An inter-laboratory comparison of urinary 3-hydroxypropylmercapturic acid measurement demonstrates good reproducibility between laboratories

Table 1 Analytical method characteristics

Laboratories	1	2	3	4
Method	LC-ESI-MS/MS	LC-ESI-MS/MS	LC-ESI-MS/MS	LC-ESI-MS/MS
mode	positive	negative	positive	negative
SPE (column)	Phenomenex Strata-X	Isolute ENV+	Waters OASIS	Waters OASIS
SPE recovery (%)	74	68	75	78
HPLC column (make)	Waters Xterra MS C18	Waters HILIC-Silica	Waters Acquity Phenyl	Thermo BioBasic AX
HPLC column (size)	50 × 2.1 mm, 2.5 μm	150 × 2.1 mm, 3 μm	100 × 2.1 mm, 1.7 μm	50 × 3 mm, 5 μm
Quantifier ion (mass)	m/z 222 - 163	m/z 220 - 89	m/z 222 - 117	m/z 220 -91
Qualifier ion (mass)	m/z 222 - 117	m/z 220 - 91
precision intra-day (%)	1.1 to 5.9	1.4 to 8.6	1.1 to 1.5	1.2 to 6.5
precision inter-day (%) ^a	5.1 to 5.3	3.3 to 7	1.7 to 3.9	3.3 to 7.5
accuracy (%)	93.2 to 102	83.9 to 102	97.6 to 102	96.8 to 101
LOD (ng/ml)	2.21	ND^d	ND	ND^d
LOQ (ng/ml)	7	25	50^f	35^f
Linearity (ng/ml)	7 to 5400	25 to 10000	50 to 5000	35 to 5000
Matrix effect (%)	ND	7.4 to 17	-1.7 to 19.6	-5.5 to 6.3

^aValues represent the precision range obtained for low, medium, and high concentrations at the time the methods were developed, except for Lab 1 where only low and high concentrations were tested.
^bBased on calibration standards.
^cLOD was an estimate based on spiked water, water being used as the SPE solvent.
^dNot determined
^eLOQ was established in spiked water, water being used as SPE solvent.
^fMatrices used were either diluted non-smoker urine or non-smoker urine with very low 3-HPMA background.

ISSN: 1756-0500