Application of the Hadamard transform to gas chromatograms of continuously sampled mixtures

Kaljurand, Mihkel; Küllik, E.

doi:10.1007/bf02314770

Cited by 21 publications

(12 citation statements)

References 5 publications

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“…Due to such small sample volume, the detection sensitivity is limited, although the use of large volume in a single injection becomes possible and devices to achieve this are commercially available 8–10. With respect to chromatographic separations, some studies have reported on the use of HT for GC 11. The advantages of the HT technique using pseudorandom injections in GC have also been proposed but only by means of computer simulation.…”

Section: Introductionmentioning

confidence: 99%

Application of Hadamard transform to gas chromatography/nonresonant multiphoton ionization/time‐of‐flight mass spectrometry

Cheng

Chang

Uchimura

et al. 2010

J of Separation Science

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The technique of Hadamard transform was successfully coupled with GC/nonresonant multiphoton ionization/TOFMS, for the first time. 1,4-Dichlorobenzene and the fourth harmonic generation (266 nm) of a Nd:YAG laser were employed as a model sample and an ionization laser, respectively. A Hadamard-injector coupled with a capillary-based supersonic jet nozzle (capillary-injector) was also developed in this study. The Hadamard-injector was used to obtain the chromatogram, which was encoded by successive sample introduction based on Hadamard codes, and the capillary-injector was used for injection of GC-elutes into TOFMS. Compared with a conventional single injection method, the S/N ratios were substantially improved after inverse Hadamard transformation of the encoded chromatogram. Under optimized conditions, when Hadamard matrices of 103 and 255 were used, the S/N ratios of the signals for 1,4-dichlorobenzene (concentration level, 4 microg/1 mL ACN) were substantially improved to 4.1- and 6.6-fold, respectively, and those improvements are in good agreement with those obtained by theory (5.1- and 8.0-fold).

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Section: Introductionmentioning

confidence: 99%

Application of Hadamard transform to gas chromatography/nonresonant multiphoton ionization/time‐of‐flight mass spectrometry

Cheng

Chang

Uchimura

et al. 2010

J of Separation Science

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“…However, the calculation can begin at the earliest after the elution of the last component from the last injection of the first PRBS . For a process stream with a constant composition, the convoluted chromatogram can be described by the forward Hadamard transformation given in eq where S ( m × m matrix) is the convolution matrix derived from the PRBS . The deconvoluted chromatogram can be obtained by multiplying the inverse convolution matrix with the convoluted chromatogram according to the inverse Hadamard transformation given in eq . …”

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Online High Throughput Measurements for Fast Catalytic Reactions Using Time-Division Multiplexing Gas Chromatography

et al. 2018

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Developing new catalysts is crucial for optimization of chemical processes. Thus, advanced analytical methods are required to determine the catalytic performance of new catalysts accurately. Usually, gas chromatographic methods are employed to analyze quantitatively the product distribution of volatile compounds generated by a specific catalyst. However, the characterization of rapidly changing catalysts, e.g., due to deactivation, still poses an analytical challenge because gas chromatographic methods are too slow for monitoring the change of the complex product spectra. Here, we developed a gas chromatographic technique based on the concept of multiplexing gas chromatography (mpGC) for fast and comprehensive analysis of the product stream from a catalytic testing unit. This technique is applied for the study of the catalytic reaction of methanol-to-olefins (MTO) conversion. For this method, the time distance between two measurements is chosen so that the chromatograms but not the peaks themselves are superimposed. In this way, stacked chromatograms are generated in which the components from successively injected samples elute baseline separated next to each other from the column. The peaks from different samples are interlaced, and for this reason, the method is referred to as time-division multiplexing gas chromatography (td-mpGC). The peaks are analyzed by direct peak integration not requiring a Hadamard transformation for deconvolution of the raw data as usual for many mpGC applications. Therefore, the sample can be injected equidistantly. The integrated peaks have to be allocated to the correct retention times. The time distance between two measurements for studying the reaction and regeneration cycles of MTO catalysts is 4.3 min and 38 s, respectively. Column switching techniques such as back-flush and heart-cut are introduced as general tools for multiplexing gas chromatography.

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confidence: 99%

“…Multiplexing chromatography can be described by Hadamard transformation . Within this model, the convoluted chromatogram is the result of the forward Hadamard transformation according to eq . where S ( m × m matrix) is the convolution matrix derived from the PRBS . The inverse convolution matrix multiplied with the convoluted chromatogram produces the deconvoluted chromatogram, shown in eq (inverse Hadamard transformation). …”

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Online Continuous Trace Process Analytics Using Multiplexing Gas Chromatography

2017

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The analysis of impurities at a trace level in chemical products, nutrition additives, and drugs is highly important to guarantee safe products suitable for consumption. However, trace analysis in the presence of a dominating component can be a challenging task because of noncompatible linear detection ranges or strong signal overlap that suppresses the signal of interest. Here, we developed a technique for quantitative analysis using multiplexing gas chromatography (mpGC) for continuous and completely automated process trace analytics exemplified for the analysis of a CO stream in a production plant for detection of benzene, toluene, ethylbenzene, and the three structural isomers of xylene (BTEX) in the concentration range of 0-10 ppb. Additional minor components are methane and methanol with concentrations up to 100 ppm. The sample is injected up to 512 times according to a pseudorandom binary sequence (PRBS) with a mean frequency of 0.1 Hz into a gas chromatograph equipped with a flame ionization detector (FID). A superimposed chromatogram is recorded which is deconvoluted into an averaged chromatogram with Hadamard transformation. Novel algorithms to maintain the data acquisition rate of the detector by application of Hadamard transformation and to suppress correlation noise induced by components with much higher concentrations than the target substances are shown. Compared to conventional GC-FID, the signal-to-noise ratio has been increased by a factor of 10 with mpGC-FID. Correspondingly, the detection limits for BTEX in CO have been lowered from 10 to 1 ppb each. This has been achieved despite the presence of detectable components (methane and methanol) with a concentration about 1000 times higher than the target substances. The robustness and reliability of mpGC has been proven in a two-month field test in a chemical production plant.

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Application of the Hadamard transform to gas chromatograms of continuously sampled mixtures

Cited by 21 publications

References 5 publications

Application of Hadamard transform to gas chromatography/nonresonant multiphoton ionization/time‐of‐flight mass spectrometry

Application of Hadamard transform to gas chromatography/nonresonant multiphoton ionization/time‐of‐flight mass spectrometry

Online High Throughput Measurements for Fast Catalytic Reactions Using Time-Division Multiplexing Gas Chromatography

Online Continuous Trace Process Analytics Using Multiplexing Gas Chromatography

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