Cédric SARAZIN, Pierre RIOLLET, Michel NERTZ

Cédric SARAZIN, Pierre RIOLLET, Michel NERTZ
Wynsep SAS, 815 La Pyrénéenne, 31670 Labège Innopôle, France
csarazin@wynsep.com
INTRODUCTION
Capacitively coupled contactless conductivity detection (C4D), has become a powerful detection method in capillary electrophoresis for a large variety
of analytes. This universal detection is easy to implement and offers a great flexibility in capillary handling (no detection window).
In this work, a new modular capillary electrophoresis system (Wyn-CE) manufactured by Wynsep SAS is associated to a C4D detector in order to analyze
organic acids (sulfuric, tartaric, malic, citric, succinic, lactic, phosphoric, and gluconic acids) in wine. Obtained results were compared to those obtained
with the OIV–MA-AS313-19 method using a UV detection. In the second part, fluoride anion, inorganic cations (NH4+, K+, Ca2+, Mg2+, and Na+) and
glyphosate in water samples were also analyzed with fast and sensitive method.
ANALYSIS OF ORGANIC ACIDS IN WINE SAMPLES – COMPARISON UV AND C4D DETECTIONS
Organic acids in wine are important components in both winemaking and finished products of wine. They are naturally present in grapes and wine
or added by the human action. In order to control the wine quality, organic acid contents need to be controlled. CE with UV detection is one of the
method used for this application. We present a comparison with a new detection mode, contactless conductivity detection (C4D).
C4D DETECTION
UV DETECTION (OIV-MA-AS313-19 method)
Standard at 30 ppm
Standard at 10 ppm (except gluconate 20 ppm)
Performances
identical to
those described
in the OIV
2
(28 ppm)
(94 ppm)
Red wine #1
Red wine #2
(dil 1/25)
(61 ppm)
(10 ppm)
(37 ppm)
(47 ppm)
(10 ppm)
(dil 1/50)
Sample prep :
just filtering and
diluting red wine
4
(13 ppm)
1
6
(5 ppm)
(45 ppm)
5
(11 ppm)
8
(10 ppm)
1-sulfate ; 2-tartarate ; 3-malate ; 4- citrate ; 5-succinate ; 6-lactate ; 7-phosphate. (IS = chlorate, 20 mg/L).
Buffer : PDC + CTAB (EOF modif) + ACN, pH 5.6. Capillary : bare-fused silica, L = 60 cm, l = 52 cm, ID = 50 µm;
Injection : hydrodynamic, 50 mbar, 4s Voltage : - 16 kV; Temperature : 25 ° C. Detection : 254 nm, indirect
LOD (S/N = 3)(ppm)
UV detection
C4D
Sulfate
5.1
0.2
Sample prep :
just filtering and
diluting red wine
1-sulfate ; 2-tartarate ; 3-malate ; 4- citrate ; 5-succinate ; 6-lactate ; 7-phosphate ; 8, gluconate(IS = formate, 5 mg/L).
Buffer : MES + Histidine + CTAB (EOF modif), pH 6,1. Capillary : bare-fused silica, L = 70 cm, l = 40 cm, ID = 50 µm;
Injection : hydrodynamic, 50 mbar, 6s Voltage : - 30 kV; Temperature : 25 ° C. Detection, C4D, frequency 250 kHz, A = 100%
Tartarate
7.4
0.6
Malate
7.5
0.6
Very fast separation (2.5 min vs 6.5 min in UV)
Citrate
7.2
1.1
Succinate
6.5
1.0
Lactate
7.4
1.5
Phosphate
8.2
2.5
ADVANTAGES AND DRAWBACKS OF C4D vs UV
No detection window on capillary and no lamp
Less selective than UV (all ionized interfering compounds
can be detected)
High sensitivity compared to UV (Gain x 25 to 3)
ANALYSIS OF INORGANIC ANIONS AND CATIONS AND GLYPHOSATE IN WATER SAMPLES
FLUORIDE ANION and INORGANIC CATION ANALYSES IN WASTEWATER
At request of a water analysis laboratory, WynSep laboratory developed CE methods for the determination of fluoride
anion and inorganic cations in complex wastewater sample in order to confirm their results.
Cl-
NO2SO42NO3ClO4ClO3-
Standard 20 ppb
Standard 20 µM
F-
GLYPHOSATE ANALYSIS IN TAP WATER
Glyphosate is the most widely used herbicide in the world. WynSep
develop a CE method for the analysis of Glyphosate and its major
metabolite, aminophosphonic acid (AMPA).
Standard GLYP : 50 ppb
AMPA : 300 ppb
HCO3-
3- (300 mM)
Wastewater
Wastewater
(dil 1/50)
(dil 1/5000)
4- (250 mM)
Tap water spiked with : GLYP 5 ppb
AMPA 20 ppb
(12 ppm)2(10 mM)
1(20 mM)
EOF modifier : hexadimethrine bromide 1 % in water; Buffer : Tris + CHES, pH 8.6; Capillary : bare-fused silica, L = 90
cm, l = 78 cm, ID = 75 µm ; Injection : electrokinetic, -2 kV, 6 s ; Voltage : -25 kV ; Detection : C4D, frequency 500 kHz,
A = 70%; Temperature : 25 ° C
5(10 mM)
IS (20 µM)
Buffer : Glacial acetic acid + L-Histidine + 18-C-6, pH 4.1 ; Capillary : bare-fused silica, L = 65 cm, l = 50
cm, ID = 50 µm ; Injection : hydrodynamic, 50 mbar, 8 s ; Voltage : +30 kV ; Detection : C4D, frequency
500 kHz, A = 100% ; Temperature : 25 ° C. Identification : 1-NH4+ ; 2-K+ ; 3-Ca2+ ; 4-Na+ (51 µM) ;
5-Mg2+ (2 µM) ; (IS = Li+, 20 µM)
Buffer : MES + L-Histidine + CTAB, pH 6.3 ; Capillary : bare-fused silica, L = 55 cm, l = 35 cm, ID = 50 µm ;
Injection : electrokinetic, -10kV, 8 s after waterplug 50 mbar, 4s ; Voltage : -20 kV ; Detection : C4D,
frequency 300 kHz, A = 100% ; Temperature : 25 ° C.
CONCLUSION
Contactless capacitively coupled conductivity detector is a suitable detection method for inorganic anions and cations but also for organic compounds as organic acids or pesticides in capillary
electrophoresis. With C4D detection, important gains in sensitivity and analysis time are obtained compared to UV detection. For example, for organic acid analyses, LOD are divided by 25 and analysis
time by 3. The add of sample prep step to decrease matrix effects, should allow improve sensitivity for glyphosate analysis and after CE will become a valuable alternative to LC/MS methods.