Whole column detection:  application to high-performance liquid chromatography

Rowlen, Kathy L.; Duell, Kenneth A.; Avery, James; Birks, John W.

doi:10.1021/ac00198a008

Cited by 26 publications

(19 citation statements)

References 34 publications

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“…For Gaussian function 6-7 points are sufficient to describe it Calculates 7 points per peak for less than 0.1% error in peak area (uses Shannon's theorem) [18] 10 data points across 2.355 σ G Provides a "good guideline" for fast peaks [48] 8 data points across baseline width of a Gaussian 8σ G No criterion provided [52] 36 data points per peak Approximation derived from the inverse relationship between standard deviation of the Gaussian function and its Fourier transform [17] 14 data points per peak Analysis based on allowed maximum error (0.001%) in the peak height [14] sampling frequency = CQ√N 4V e 1 + k C= no. of data points desired per peak, Q= volumetric flow rate, N = plates, V o = void volume, k= retention factor [53] Real time oversampling (up to MHz) and data averaging Shows the advantage of oversampling points into one recorded data and averaging to improve the signal to noise ratio [19] 15 data points for a Gaussian peak 15 data points for < 0.1 % error in peak area; Simpson's rule: 6 x base width [15] Data acquisition rate has no influence on band broadening and resolution Also shows an example of "hidden features" in the software causing peak distortion [21]…”

Section: Suggestions For Practitioners and Manufacturersmentioning

confidence: 99%

Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial

Wahab

Dasgupta

Kadjo

et al. 2016

Analytica Chimica Acta

118

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With increasingly efficient columns, eluite peaks are increasingly narrower. To take full advantage of this, choice of the detector response time and the data acquisition rate a.k.a. detector sampling frequency, have become increasingly important. In this work, we revisit the concept of data sampling from the theorem variously attributed to Whittaker, Nyquist, Kotelnikov, and Shannon. Focusing on time scales relevant to the current practice of high performance liquid chromatography (HPLC) and optical absorbance detection (the most commonly used method), even for very narrow simulated peaks Fourier transformation shows that theoretical minimum sampling frequency is still relatively low (<10 Hz). However, this consideration alone may not be adequate for real chromatograms when an appreciable amount of noise is present. Further, depending on the instrument, the manufacturer's choice of a particular data bunching/integration/response time condition may be integrally coupled to the sampling frequency. In any case, the exact nature of signal filtration often occurs in a manner neither transparent to nor controllable by the user. Using fast chromatography on a state-of-the-art column (38,000 plates), we evaluate the responses produced by different present generation instruments, each with their unique black box digital filters. We show that the common wisdom of sampling 20 points per peak can be inadequate for high efficiency columns and that the sampling frequency and response choices do affect the peak shape. If the sampling frequency is too low or response time is too large, the observed peak shapes will not remain as narrow as they really are - this is especially true for high efficiency and high speed separations. It is shown that both sampling frequency and digital filtering affect the retention time, noise amplitude, peak shape and width in a complex fashion. We show how a square-wave driven light emitting diode source can reveal the nature of the embedded filter. We discuss time uncertainties related to the choice of sampling frequency. Finally, we suggest steps to obtain optimum results from a given system.

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Section: Suggestions For Practitioners and Manufacturersmentioning

confidence: 99%

Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial

Wahab

Dasgupta

Kadjo

et al. 2016

Analytica Chimica Acta

118

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show abstract

“…Furthermore, surface concentration combined with in situ spectroscopic measurement can be used as a detection strategy in chromatography, which can reverse the effects of dilution in the mobile phase for compounds that are highly retained on a column. 3 Several methods have been developed for in situ spectroscopic detection of pre-concentrated PAH analytes on solid surfaces by fluorescence spectroscopy [4][5][6] or room-temperature phosphorescence 7,8 measurements. One effective method involves adsorption of analytes on a C18derivatized silica trapped in a porous perfluorinated polyethylene or other membrane, followed by in situ fluorescence 5,6 or phosphorescence 7,8 detection.…”

Section: Introductionmentioning

confidence: 99%

C18-Modified Metal-Colloid Substrates for Surface-Enhanced Raman Detection of Trace-Level Polycyclic Aromatic Hydrocarbons in Aqueous Solution

2004

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Metal colloids immobilized on a glass support substrate are modified with a self-assembled alkylsilane (C18) layer to promote adsorption of polycyclic aromatic hydrocarbons from aqueous solutions. Detection of these compounds from low concentration solutions is accomplished by using surface-enhanced Raman scattering (SERS). SERS spectra of pyrene adsorbed to C18-modified immobilized silver colloids are dominated by Raman bands that are not consistent with pyrene and indicate that pyrene undergoes a chemical reaction at the surface. The origins of this surface product are investigated, and it is determined that silver and oxygen are required to form the product, whose Raman spectrum is consistent with oxidation to a quinone. When a C18-modified gold-colloid substrate is used, Raman scattering consistent with unreacted pyrene is observed. The adsorption and detection of pyrene adsorbed from low (2 ppb) concentration aqueous solutions onto C18-modified gold-colloid substrates is reported; naphthalene and phenanthrene are detected at approximately 5 ppb. Adsorption kinetics are rapid (<5 min), and the concentration-dependent SERS response is consistent with a Langmuir isotherm.

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“…However, by integrating the LC onto microfluidics platform has opened up the opportunity for whole column detection (Wang et al 2010;Chan et al 2014;Al Lawati et al 2014). Since the late 1980s, many reports shown great interest in whole column detection for LC as to help better understanding of the separation process within the stainless steel column (Gelderloos et al 1986;Rowlen et al 1989;Wu et al 2005). Besides that, whole column detections provide more than one result per assay as compared to the conventional post column detection.…”

Section: Introductionmentioning

confidence: 99%

A study of the in-column detection performance for chromatography separation

Leow

Chee

Patel

et al. 2015

Microfluid Nanofluid

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This paper studies the in-column detection performance for chromatography separation. Numerical modelling was performed to investigate the detection efficiency of the electrodes that are suspended within a packed chromatography column. The results show that the density of the silica beads packed within the channel does not hinder the detection ability of the electrode. The findings have been further validated with experimental works. A 8 in-column electrode array provides the full separation progress traces of the five neurotransmitters and metabolites (adrenalin, dopamine, DOPAC, serotonin and 5-HIAA) within the column. From the in-column detection, better peak resolutions are developed though the separation column as compared to the conventional post column detection. The whole progress of the separation shows that good separation (Rs > 1) can be obtained at E5 (28.7 mm from column inlet), whereas baseline separation could be obtained at E8 (last in-column electrode) with Rs ≥ 1.5 within 60 minutes. The presented results suggest the packing materials within the column does not obstruct the efficiency of the electrodes but able to produce a good baseline separation detection as compared to conventional post column detection.

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Whole column detection: application to high-performance liquid chromatography

Cited by 26 publications

References 34 publications

Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial

Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial

C18-Modified Metal-Colloid Substrates for Surface-Enhanced Raman Detection of Trace-Level Polycyclic Aromatic Hydrocarbons in Aqueous Solution

A study of the in-column detection performance for chromatography separation

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