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Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial
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 samplin...
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| Published in: | Analytica chimica acta 2016-02, Vol.907, p.31-44 |
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| creator | Wahab, M. Farooq Dasgupta, Purnendu K. Kadjo, Akinde F. Armstrong, Daniel W. |
| description | 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 ( |
| doi_str_mv | 10.1016/j.aca.2015.11.043 |
| format | article |
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[Display omitted]
•Concept of sampling frequency relevant to chromatographic peaks is revisited.•Association of response time with digital filters is described.•Qualitative identification of embedded filters with pulsed LED experiments.•Practical considerations for choosing sampling frequency and response times.•Effect of coupled sampling frequency and response time is shown.</description><identifier>ISSN: 0003-2670</identifier><identifier>EISSN: 1873-4324</identifier><identifier>DOI: 10.1016/j.aca.2015.11.043</identifier><identifier>PMID: 26803000</identifier><language>eng</language><publisher>Netherlands: Elsevier B.V</publisher><subject>Detectors ; Digital filters ; Fast separations ; Filtering ; Filtration ; Focusing ; High-efficiency chromatography ; Liquid chromatography ; Noise ; Response time ; Response times ; Sampling ; Sampling theorem</subject><ispartof>Analytica chimica acta, 2016-02, Vol.907, p.31-44</ispartof><rights>2015 Elsevier B.V.</rights><rights>Copyright © 2015 Elsevier B.V. All rights reserved.</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c532t-e9be47d26441c881b79060b4ebaa7141455b2ddc196f1a0219a82d3ab7f20f6b3</citedby><cites>FETCH-LOGICAL-c532t-e9be47d26441c881b79060b4ebaa7141455b2ddc196f1a0219a82d3ab7f20f6b3</cites><orcidid>0000-0003-4455-2184</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27924,27925</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/26803000$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Wahab, M. Farooq</creatorcontrib><creatorcontrib>Dasgupta, Purnendu K.</creatorcontrib><creatorcontrib>Kadjo, Akinde F.</creatorcontrib><creatorcontrib>Armstrong, Daniel W.</creatorcontrib><title>Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial</title><title>Analytica chimica acta</title><addtitle>Anal Chim Acta</addtitle><description>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.
[Display omitted]
•Concept of sampling frequency relevant to chromatographic peaks is revisited.•Association of response time with digital filters is described.•Qualitative identification of embedded filters with pulsed LED experiments.•Practical considerations for choosing sampling frequency and response times.•Effect of coupled sampling frequency and response time is shown.</description><subject>Detectors</subject><subject>Digital filters</subject><subject>Fast separations</subject><subject>Filtering</subject><subject>Filtration</subject><subject>Focusing</subject><subject>High-efficiency chromatography</subject><subject>Liquid chromatography</subject><subject>Noise</subject><subject>Response time</subject><subject>Response times</subject><subject>Sampling</subject><subject>Sampling theorem</subject><issn>0003-2670</issn><issn>1873-4324</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2016</creationdate><recordtype>article</recordtype><recordid>eNqNkU1r3DAQhkVpabZpf0AvRcceYkcjy5bdnkLoRyDQQ9KzkKXRrhZ_RZIDC_3x1XbTHktOw8AzL8z7EPIeWAkMmst9qY0uOYO6BCiZqF6QDbSyKkTFxUuyYYxVBW8kOyNvYtznlQMTr8kZb1pW5XVDft3pcRn8tKUu4MOKkzlc0IBxmaeINPkRI9WTpTj2aC1aGv120gN1fkhBJz9P1E_U6Zgu6M5vdxSd88Yfc-jgH1ZvqdmFedRp3ga97A6f6BVNa5qD18Nb8srpIeK7p3lOfn79cn_9vbj98e3m-uq2MHXFU4Fdj0Ja3ggBpm2hlx1rWC-w11qCAFHXPbfWQNc40PnHTrfcVrqXjjPX9NU5-XjKXcKcf4xJjT4aHAY94bxGBbLLhdUg5DPQpq1bJhk8B2Ud1FJWGYUTasIcY0CnluBHHQ4KmDqqVHuVVaqjSgWgssp88-Epfu1HtP8u_rrLwOcTgLm6R49BxT_Fo_UBTVJ29v-J_w0xQ678</recordid><startdate>20160211</startdate><enddate>20160211</enddate><creator>Wahab, M. 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Farooq</creatorcontrib><creatorcontrib>Dasgupta, Purnendu K.</creatorcontrib><creatorcontrib>Kadjo, Akinde F.</creatorcontrib><creatorcontrib>Armstrong, Daniel W.</creatorcontrib><collection>PubMed</collection><collection>CrossRef</collection><collection>MEDLINE - Academic</collection><collection>Environment Abstracts</collection><collection>Environmental Sciences and Pollution Management</collection><collection>Environment Abstracts</collection><collection>Environmental Engineering Abstracts</collection><collection>Solid State and Superconductivity Abstracts</collection><collection>Technology Research Database</collection><collection>Engineering Research Database</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Analytica chimica acta</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Wahab, M. Farooq</au><au>Dasgupta, Purnendu K.</au><au>Kadjo, Akinde F.</au><au>Armstrong, Daniel W.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial</atitle><jtitle>Analytica chimica acta</jtitle><addtitle>Anal Chim Acta</addtitle><date>2016-02-11</date><risdate>2016</risdate><volume>907</volume><spage>31</spage><epage>44</epage><pages>31-44</pages><issn>0003-2670</issn><eissn>1873-4324</eissn><abstract>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.
[Display omitted]
•Concept of sampling frequency relevant to chromatographic peaks is revisited.•Association of response time with digital filters is described.•Qualitative identification of embedded filters with pulsed LED experiments.•Practical considerations for choosing sampling frequency and response times.•Effect of coupled sampling frequency and response time is shown.</abstract><cop>Netherlands</cop><pub>Elsevier B.V</pub><pmid>26803000</pmid><doi>10.1016/j.aca.2015.11.043</doi><tpages>14</tpages><orcidid>https://orcid.org/0000-0003-4455-2184</orcidid><oa>free_for_read</oa></addata></record> |
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| subjects | Detectors Digital filters Fast separations Filtering Filtration Focusing High-efficiency chromatography Liquid chromatography Noise Response time Response times Sampling Sampling theorem |
| title | Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A tutorial |
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