Bestimmung von Chlorcholinchlorid-R�ckst�nden in Getreide nach d�nnschicht-chromatographischer Isolierung durch Remissionsspektralphotometrie

Optimisation of the quantitative determination of chlormequat by matrix‐assisted laser desorption/ionisation mass spectrometry

“…Since the early beginnings of residue analysis of chlormequat in plant tissues, the separation of chlormequat from high amounts of naturally occurring choline and other quaternary ammonium compounds has been an important issue 1,. 39,, 40 Although choline ( m/z 104) and chlormequat ( m/z 122) were separated in the time‐of‐flight mass analyser, choline still interfered with MALDI quantification. A high amount of choline competed for ion formation with chlormequat, and thus diminished the chlormequat signal in the spectrum.…”

“…Consequently, the choline concentration in a real sample had to be reduced to such an extent as to not perturb quantification using MALDI. Thin‐layer chromatography (TLC) in different variations has been an often‐reported method for separation of choline from chlormequat40–42 and seemed to be simple and efficient for this purpose. Depending on the available instrumentation, different methods for the combination of TLC with MALDI‐MS have already been reported 32,.…”

Determination of residues of the plant growth regulator chlormequat in pears by ion-exchange high performance liquid chromatography-electrospray mass spectrometry†

“…Various methods for the determination of chlormequat residues have been reported but these have generally been based on non-specific determinative techniques, necessitating timeconsuming procedures for clean-up and for separation of chlormequat from naturally occurring or co-formulated choline and other choline derivatives. Ion-exchange and alumina columns have generally been employed prior to determination, [3][4][5][6][7][8][9][10][11] although thin-layer chromatography (TLC) has been used for separation prior to colorimetry. 4 The determinative steps have included colorimetry after chemical derivatisation or complexation, [3][4][5][6] TLC with colorimetric detection and visual comparison 7 or densitometry, 8,9 and GC determination as the derivative formed by treatment with sodium thiophenolate.…”

“…Ion-exchange and alumina columns have generally been employed prior to determination, [3][4][5][6][7][8][9][10][11] although thin-layer chromatography (TLC) has been used for separation prior to colorimetry. 4 The determinative steps have included colorimetry after chemical derivatisation or complexation, [3][4][5][6] TLC with colorimetric detection and visual comparison 7 or densitometry, 8,9 and GC determination as the derivative formed by treatment with sodium thiophenolate. 10,11 The use of potassium pentafluorothiophenolate to form an electron-capturing derivative has also been reported, 12 but the derivative formed was subsequently shown to be non-specific and the method to be potentially prone to interferences in the presence of a variety of methylating agents.…”