Combining amperometry and mass spectrometry as a dual detection approach for capillary electrophoresis

Abstract

Dual detection concepts (DDCs) are becoming more and more popular in analytical chemistry. In this work, we describe a novel DDC for capillary electrophoresis (CE) consisting of an amperometric detector (AD) and a mass spectrometer (MS). This detector combination has a good complementarity as the AD exhibits high sensitivity, whereas the MS provides excellent selectivity. Both detectors are based on a destructive detection principle, making a serial detector arrangement impossible. Thus, for the realization of the DDC, the CE flow was divided into two parts with a flow splitter. The DDC was characterized in a proof-of-concept study with ferrocene derivates and a nonaqueous background electrolyte. We could show that splitting the CE flow was a suitable method for the instrumental realization of the DDC consisting of two destructive detectors. By lowering the height of the AD compared to the MS, it was possible to synchronize the detector responses. Additionally, for the chosen model system, we confirmed that the AD was much more reproducible and had lower limits of detection (LODs) than the MS. The LODs were identical for the DDC and the single-detection arrangements, indicating no sensitivity decrease due to the CE flow splitting. The DDC was successfully applied to determine the drug and doping agent trimetazidine.

Determination of Trimetazidine in Urine by Capillary Electrophoresis with Amperometric Detection

“…The high extraction e ciency of the mentioned method, combined with very small sample volumes used in capillary electrophoresis, has the potential for a signi cant sample preconcentration in the order of hundred or thousand times, which overcomes the limitation of the relatively high limit of quanti cation (LOQ) of TMZ, determined as 0.180 µg dm − 3 . This value is in good agreement with our previously published work concerning a dual-detection concept [12]. On the other hand, both LOQ and LOD of this method are comparable not only with optical detections [9][10][11], but also with most MS detections, in which LOQ for TMZ were found in a range from tenths to hundreds of ng dm − 3 [5][6][7].…”

“…The experimental electrophoretic conditions, used in all following experiments, were based on our previous study [12] and chosen as follows -separation voltage 25 kV, injection time 15 seconds, inlet side of the capillary 10 cm higher than the outlet xed in the electrochemical detector cell and the capillary-to-working electrode distance was set to 50 µm.…”

“…In the past two decades, the most frequently used methods for the determination of TMZ in body uids, namely urine or plasma, were liquid chromatography with mass spectrometry (LC/MS) [5][6][7][8], diode array [9], or UV [10] detection. Utilization of capillary electrophoresis (CE) is, in this particular case, not so common and only a few articles can be found [11,12]; however, they provide limits of detection in the range of lower tens of µg dm − 3 , which is comparable with LC/MS techniques. At the same time, very low sample consumption (on the order of nanoliters), wide range of separable analytes, user-friendliness and low nancial and material requirements speak in favor of CE [13].…”

Sensitive and selective determination of the neonicotinoid nitenpyram utilizing capillary electrophoresis hyphenated to amperometric detection/mass spectrometry

“…The parallel arrangement of AD and MS, which are both destructive detection methods, was achieved by a commercially available flow splitter. This concept combines the high separation efficiency and low sample consumption of CE with two detectors providing complementary information about the sample [13,14]. AD is among the most sensitive detection methods for electroactive analytes and shows good reproducibility and long-term stability in non-aqueous media [15].…”

“…However, only limited qualitative information is obtained by AD [16]. MS is a powerful technique when it comes to the identification of unknown or co-migrating analytes [13]. Furthermore, the risk of false positives in the resulting electropherograms is eliminated by the DDC as the composition of each peak can be monitored by MS.…”