Determination of Quinine in Tonic Water and Caffeine in Coffee and Cola drinks using TLC-MS

Abstract

High Performance Thin Layer Chromatography coupled with Mass spectrometry (HPTLC–MS) is an analytical technique that requires low-level of sample preparation. Here it is illustrated with the determination of quinine in tonic water and caffeine in coffee and cola drinks. Tonic water and the analyzed cola drinks were decarbonized through ultrasonication, and boiled coffee was extracted through an appropriate 0.45 µm PTFE syringe filter. After the initial chromatographic separation, specific bands were eluted with an TLC-MS interface and detected with mass spectrometry.

Results

Caffeine (hRf = 56, m/z = 195.2, 236.2, Fig. 2) and quinine (hRf = 37, m/z = 325.4, Fig. 4) were detected under UV light (254 nm, Fig. 1; 366nm, Fig. 3) and measured by TLC-MS.

Fig.1: Developed plate at 254 nm.                        Fig.2: mass spectrum of caffeine in coffee
Chromatographic data shown in the table below

 

Fig.3: Developed plate at 366 nm.                       Fig.4: mass spectrum of quinine in tonic water.
Chromatographic data shown in the table below

 

Conclusion

These results demonstrate that caffeine and quinine can easily be analyzed by HPTLC-MS with a minimum of sample preparation in coffee, cola drinks or tonic water.

Chromatographic data

Track Compound Conc. [mg/mL] Application
volume [µL]
hRf Detected mass m/z
1 Caffeine standard 1 1 56 195.2, 236.2
2 Coffee   1 56 195.2, 236.2
3 Cola drinks   1 56 195.2, 236.2
4 Tonic water   1 37 325.4
5 Quinine standard 1 1 37 325.4
6 Caffeine standard 1 2 56 195.2, 236.2
7 Coffee   2 56 195.2, 236.2
8 Cola drinks   2 56 195.2, 236.2
9 Tonic water   2 37 325.4
10 Quinine standard 1 2 37 325.4

 

Application data

Chromatography
Plate HPTLC Silica gel 60 F254 MS-grade, 20x10cm
Sample preparation Caffeine and quinine standard diluted in Methanol;
Cola drinks and tonic water were decarbonated; Coffee boiled and filtered with a 0.45 µm syringe filter.
Sample application ATS 4 sample applicator (Camag), 6 mm bandwise
Application volume 1.0 and 2.0 µL
Mobile phase Isopropanol / n-Heptane / Water 7/3/1 + 1% Triethylamine
Migration distance 5 cm
Migration time 49 min
Extraction
Extraction equipment TLC-MS Interface “Plate Express” (Advion)
Extraction solvent Acetonitrile / Water 95/5 (v/v) + 0.1% Formic acid
Extraction flow 0.2 mL/min
Detection
Wavelength UV light at 254 nm and 366 nm
Staining None
MS equipment expression CMS (Advion)
MS detection ESI (+) mode (m/z 150 - 400)

Ordering Information

Description Product No.
HPTLC Si60 F254  MS-grade, 20x10 cm 1.00934
2-Propanol gradient grade for liquid chromatography LiChrosolv® 1.01040
n-Heptane for liquid chromatography LiChrosolv® 1.04390
Water for chromatography (LC-MS Grade) LiChrosolv® 1.15333
Triethylamine for synthesis 8.08352
Acetonitrile hypergrade for LC-MS LiChrosolv® 1.00029
Formic acid for analysis EMSURE 1.00264
Millex®-FH filter, 0.45 μm hydrophobic PTFE, 25 mm, non-sterile SLFH025NS

Materials