J. Hau et al., Determination of the plant growth regulator chlormequat in food by liquid chromatography-electrospray ionisation tandem mass spectrometry, J CHROMAT A, 878(1), 2000, pp. 77-86
A confirmatory method for the determination of trace levels of chlormequat
in a variety of different food matrices was developed. It entails a single
clean-up step over a solid-phase cation exchange resin and subsequent liqui
d chromatography-electrospray ionisation tandem mass spectrometry using a s
table isotopically labelled internal standard. Mass spectral acquisition wa
s done in selected reaction monitoring mode, selecting the transitions from
both the Cl-35 and the Cl-37 isotope of chlormequat. Recoveries after extr
action and clean-up, determined with radio-labelled chlormequat and average
d over the spiking range (16-65 mu g kg(-1)) in four different commodities,
were within 88-96%, with a coefficient of variation better than 8%. The me
thod can be applied to pears, pear juice concentrates, fruit purees, and ce
real products, with typical limits of detection for chlormequat estimated a
t 2-5 mu g kg(-1). A survey of different food commodities revealed that chl
ormequat was detectable - albeit at very low levels - in many of the food s
amples analysed, with the highest concentration recorded in pears purchased
in Switzerland and of South African origin (5.5 mg kg(-1)). Measurements w
ere also conducted on two LC-MS instruments and demonstrate the versatility
and robustness of the method and its applicability to instruments of diffe
rent ion source design. (C) 2000 Elsevier Science B.V. All rights reserved.