Determination of Methylisothiazolinone in wall paint using TLC-MS


Complex sample matrices can be a big problem for various analytical techniques. To minimize effects like sample carry-over, contamination or even damage of the instrumental equipment, extensive sample preparation procedures have to be performed. With TLC-MS (thin layer chromatography - mass spectrometry) one can easily analyse even complex matrices such as wall paint with a minimum of sample preparation. Below the analysis of methylisothiazolinone (MIT) in wall paint is described. One gram wall paint was weighed out and stirred for 15 minutes in 10 mL methanol / 0.4% acetic acid (20/80). Afterwards it was filtered through a 0.45 μm syringe filter. Mass spectrometry was performed by coupling the TLC-MS Interface (Camag) with an ESI mass spectrometer.


Methylisothiazolinone was detected under UV light at an hRf value of 65. The quantification by triple determination of the wall paint using peak areas and a 4 point calibration curve resulted in an average MIT concentration of 19 ppm based on the amount of wall paint matrix. In Figure 1 the UV scan the complex matrix of the wall paint of the MIT standard (a) as well as the one of the wall paint (b) recorded at 276 nm are presented. It could be clearly shown that was perfectly separated from the contained methylisothiazolinone. The mass spectrum (Fig. 2) shows the protonated molecule of methylisothiazolinone at m/z 116.2 measured at the hRf value of 65.

UV scan of TLC plate with chromatographically separated MIT standard

Figure 1: UV scan of TLC plate with chromatographically separated MIT standard (a) and wall paint containingMIT (b) at 276 nm.

Mass spectrum and structure of methylisothiazolinone

Figure 2: Mass spectrum and structure of methylisothiazolinone.


These results demonstrate that methylisothiazolinone can be easily analysed by TLC-MS with a minimum of sample preparation even in a complex matrix like wall paint.

Application data

Plate HPTLC Silica gel 60 WR F254s, 20x10 cm
Sample preparation stir 1 g wall paint in 10 mL Methanol / 0.4% Acetic acid (20/80), filtration
Sample application ATS 4 sample applicator (Camag), 6 mm band-wise
Application volume 0.1 - 2 μL
Mobile phase Methanol / Acetonitrile / 0.4% Acetic acid 3/3/90 (v/v/v)
Migration distance 5 cm
Migration time 13 min
Extraction equipment TLC-MS Interface from Camag
Extraction solvent Acetonitrile / Water 95/5 (v/v) + 0.1% Formic acid
Extraction flow 0.2 mL/min
Documentation equipment documentation unit Reprostar / Digistore (Camag)
Wavelength scan under UV light at 276 nm
Staining none
MS equipment single-quadrupole mass spectrometer
MS detection ESI (+) mode (m/z 50 - 300)

Chromatographic data

Compound Conc. [mg/mL] Application volume [μL] hRf Detected mass m/z
MIT standard 0.15 0.1, 0.2, 0.3, 0.4 65 116.2
MIT in wall paint - 2 65 116.2

Ordering information

Description Product No.
HPTLC Silica gel 60 WR F254s, 20x10 cm 1.15552
Acetonitrile hypergrade for LC-MS LiChrosolv® 1.00029
Methanol hypergrade for LC-MS LiChrosolv® 1.06035
Acetic acid 99 – 100% for synthesis 8.18755
Formic acid for analysis EMSURE® 1.00264
Water for chromatography (LC-MS Grade) LiChrosolv® 1.15333
Millex®-FH filter, 0.45 μm hydrophobic PTFE, 25 mm, non-sterile SLFH025NS