Implications of dispersion in connecting capillaries for separation systems involving post-column flow splitting

Gunnarson, Caden; Lauer, Thomas; Willenbring, Harrison; Larson, Eli J.; Dittmann, Monika; Broeckhoven, Ken; Stoll, Dwight R.

doi:10.1016/j.chroma.2021.461893

Cited by 13 publications

(12 citation statements)

References 23 publications

(32 reference statements)

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“…Due to sensitivity differences of the two mass spectrometers, the major portion was fed to the isotope ratio mass spectrometer and the minor portion to the high-resolution mass spectrometer. For LC, it has been shown in detail that the choice of the capillary inner diameter and length affects the splitting ratio and, as a consequence, the measured raw isotope ratios because the flow through the membrane separation unit in the LC-IRMS interface can change, which affects the pervaporation of CO 2 and thus its amount entering the mass spectrometer. In addition, they point out that the interaction of the split ratio and splitter placement must be carefully matched to the detectors involved when two detectors are used .…”

Section: Resultsmentioning

confidence: 99%

“…For LC, it has been shown in detail that the choice of the capillary inner diameter and length affects the splitting ratio and, as a consequence, the measured raw isotope ratios because the flow through the membrane separation unit in the LC-IRMS interface can change, which affects the pervaporation of CO 2 and thus its amount entering the mass spectrometer. In addition, they point out that the interaction of the split ratio and splitter placement must be carefully matched to the detectors involved when two detectors are used . The positioning of the splitter influences the length of the connecting capillaries and thus the resulting back pressure.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, they point out that the interaction of the split ratio and splitter placement must be carefully matched to the detectors involved when two detectors are used. 27 The positioning of the splitter influences the length of the connecting capillaries and thus the resulting back pressure. LC-IRMS is limited to the use of water as an eluent in contrast to conventional LC−MS applications.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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How to Couple LC-IRMS with HRMS─A Proof-of-Concept Study

et al. 2022

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Compound-specific stable isotope analysis (CSIA) is a unique analytical technique for determining small variations in isotope ratios of light isotopes in analytes from complex mixtures. A problem of CSIA using gas chromatography (GC) and liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) is that any structural information of the analytes is lost due to the processes involved in determining the isotope ratio. To obtain the isotopic composition of, for example, carbon from organic compounds, all carbon in each analyte is quantitatively converted to CO 2 . For GC-IRMS, open split GC-IRMS-MS couplings have been described that allow additional acquisition of structural information of analytes and interferences. Structural analysis using LC-IRMS is more difficult and requires additional technical and instrumental efforts. In this study, LC was combined for the first time with simultaneous analysis by IRMS and high-resolution mass spectrometry (HRMS), enabling the direct identification of unknown or coeluting species. We have thoroughly investigated and optimized the coupling and showed how technical problems, arising from instrumental conditions, can be overcome. To this end, it was successfully demonstrated that a consistent split ratio between IRMS and HRMS could be obtained using a variable postcolumn flow splitter. This coupling provided reproducible results in terms of resulting peak areas, isotope values, and retention time differences for the two mass spectrometer systems. To demonstrate the applicability of the coupling, we chose to address an important question regarding the purity of international isotope standards. In this context, we were able to confirm that the USGS41 reference material indeed contains substantial amounts of pyroglutamic acid as suggested previously in the literature. Moreover, the replacement material, USGS41a, still has significant amounts of pyroglutamic acid as impurity, rendering some caution necessary when using this material for isotopic calibration.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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How to Couple LC-IRMS with HRMS─A Proof-of-Concept Study

et al. 2022

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“…Although entrapment of residual solvent(s) within the deposited mass on QCM could be suspected as a possible reason for the varying response, we excluded this possibility as the frequency shift immediately stabilized and stayed constant upon a longer drying period regardless of the eluent composition (see Supporting Information, Section S3 and Figure S1). In fact, the overall split ratio shift for the HPLC–QCM dry-mass sensing system is caused by backpressure originating from the small inner diameter of the liquid channel of the spray dryer (25 × 20 μm 2 ), which is the only additional constriction in the system compared to manufacturer’s data. − In addition, the pressure in the system leads to a deformation of the liquid channel made of PDMS and thus to an increase of its hydraulic diameter ( D hyd ) as reported by Kartanas et al This deformation strongly influences the hydraulic resistance [ R res ∝ 1/( D hyd ) 4 ] and thus the generated backpressure. Since D hyd is dependent on the liquid dynamic viscosity, the trend of the split ratios must follow the trend of the dynamic viscosities of the respective solvent compositions.…”

Section: Resultsmentioning

confidence: 99%

Quartz Crystal Microbalance as a Holistic Detector for Quantifying Complex Organic Matrices during Liquid Chromatography: 1. Coupling, Characterization, and Validation

Wabnitz,

Canavan,

Chen

et al. 2024

Anal. Chem.

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A matrix in highly complex samples can cause adverse effects on the trace analysis of targeted organic compounds. A suitable separation of the target analyte(s) and matrix before the instrumental analysis is often a vital step for which chromatographic cleanup methods remain one of the most frequently used strategies, particularly high-performance liquid chromatography (HPLC). The lack of a simple real-time detection technique that can quantify the entirety of the matrix during this step, especially with gradient solvents, renders optimization of the cleanup challenging. This paper, along with a companion one, explores the possibilities and limitations of quartz crystal microbalance (QCM) dry-mass sensing for quantifying complex organic matrices during gradient HPLC. To this end, this work coupled a QCM and a microfluidic spray dryer with a commercial HPLC system using a flow splitter and developed a calibration and data processing strategy. The system was characterized in terms of detection and quantification limits, with LOD = 4.3−15 mg/L and LOQ = 16−52 mg/L, respectively, for different eluent compositions. Validation of natural organic matter in an environmental sample against offline total organic carbon analysis confirmed the approach's feasibility, with an absolute recovery of 103 ± 10%. Our findings suggest that QCM dry-mass sensing could serve as a valuable tool for analysts routinely employing HPLC cleanup methods, offering potential benefits across various analytical fields.

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“…With a 1 z split 1:4, effective peak capacities of 1800, 3400, and 5100 could be achieved in 60, 120, and 200 min, respectively. Several disadvantages of post-1 D-flow-splitting can be listed: (i) maintaining the same 1 z split from run-to-run can be challenging and makes this method questionable for quantification, (ii) low split ratios imply high dilution (low 2 V i in Equation ( 10)), (iii) significant additional band broadening may occur in case of very low 1 z split as was recently highlighted [32,33], and (iv) flow splitting alone may not be sufficient to avoid injection effects for fully orthogonal combinations. In this latter case, the additional reduction of 1 𝑑 𝑖,col ∕ 2 𝑑 𝑖,col may be necessary.…”

Section: Flow Splitting ( 1 Z Split < 1)mentioning

confidence: 99%

Strategies to circumvent the solvent strength mismatch problem in online comprehensive two‐dimensional liquid chromatography

Chapel

Heinisch

2021

J of Separation Science

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On-line comprehensive two-dimensional liquid chromatography is a powerful technique for the separation of highly complex samples. Due to the addition of the second dimension of separation, impressive peak capacities can be obtained within a reasonable analysis time compared to one-dimensional liquid chromatography. In online comprehensive two-dimensional liquid chromatography, the separation power is maximized by selecting two separation dimensions as orthogonal as possible, which most often requires the combination of different mobile phases and stationary phases. The online transfer of a given solvent from the first dimension to the second dimension may cause severe injection effects in the second dimension, mostly due to solvent strength mismatch. Those injection effects may include peak broadening, peak distortion, peak splitting or breakthrough phenomenon. They are often found to reduce significantly the peak capacity and the peak intensity. To overcome such effects, arising specifically in online comprehensive two-dimensional liquid chromatography, different methods have been developed over the years. In this review, we focused on the most recently reported ones. A critical discussion, supported by a theoretical approach, gives an overview of their advantages and drawbacks.

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Implications of dispersion in connecting capillaries for separation systems involving post-column flow splitting

Cited by 13 publications

References 23 publications

How to Couple LC-IRMS with HRMS─A Proof-of-Concept Study

How to Couple LC-IRMS with HRMS─A Proof-of-Concept Study

Quartz Crystal Microbalance as a Holistic Detector for Quantifying Complex Organic Matrices during Liquid Chromatography: 1. Coupling, Characterization, and Validation

Strategies to circumvent the solvent strength mismatch problem in online comprehensive two‐dimensional liquid chromatography

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