Experimental design considerations in quantification experiments by using the internal standard technique: Cholesterol determination by gas chromatography as a case study

Araujo, Pedro; Couillard, Felicia Dawn; Leirnes, Else; Ask, Kjersti; Bøkevoll, Annbjørg; Frøyland, Livar

doi:10.1016/j.chroma.2006.03.119

Cited by 26 publications

(17 citation statements)

References 7 publications

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“…higher efficiency) and hence, being timesaving, especially as the number of experimental variables increases (Ferreira et al, 2004(Ferreira et al, , 2007Araujo et al, 2006). Doehlert design has been utilized for optimizing chromatographic/ detector conditions (Tak et al, 2007), determining optimal levels of internal standards for quantification (Araujo et al, 2006) and foremost for optimizing DI-SPME/HS-SPME for analyzing a variety of analytes (Aguilar et al, 1999;Navalón et al, 2002a;Pizarro et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Optimization of a novel headspace–solid‐phase microextraction–gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices

DiCicco

Láng

Harper

2009

Biomedical Chromatography

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Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace-solid-phase microextraction-gas chromatographic (HS-SPME-GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer-coated, drug-eluting cardiovascular stents. The effects of four independent experimental variables (HS-SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack-of-fit. The optimized HS-SPME-GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS-SPME-GC method can offer higher sensitivity compared with conventional headspace analyzer-based sampling.

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Section: Introductionmentioning

confidence: 99%

Optimization of a novel headspace–solid‐phase microextraction–gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices

DiCicco

Láng

Harper

2009

Biomedical Chromatography

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“…In a recent comparative study between the internal standard and the traditional calibration method by using LCMS/MS [9], it is reported that the degree of ionization in the electro-spray ion source is strongly dependent on the amount of molecules resulting in a non-linearity in the concentration/response ratio. It must be said, that several quantitative studies [10][11][12] have demonstrated the variability of the RF as a direct result of varying the analyte and internal standard concentrations indicating clearly that among the possible variables affecting the RF accuracy, the interaction analyte/internal-standard could play an important role which is generally omitted in quantification studies.…”

Section: Response Factor Accuracy and Recoverymentioning

confidence: 99%

Direct Injection of Redissolved Cell Culture Media into a Single-Column Liquid Chromatography Coupled to Mass Spectrometry for the Measurement of PGE2

Araujo¹,

Du²,

Nguyen³

et al. 2008

TOACJ

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Abstract:The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatography coupled to mass spectrometry involves time-consuming procedures such as derivatisation, degradation, solid-phase extraction, liquidliquid extraction, thin layer chromatography and sometimes, combination of all these procedures prior to the injection of the sample in the chromatography system. The performance of a method that allows the direct injection of redissolved cell culture media into a single-column liquid chromatography instrument coupled to mass spectrometry is evaluated. The external standard calibration curves were linear between 1-50 ng/ml for Williams' medium E and L-15 medium. The limit of detection and quantification were 0.5 and 1 ng/ml in both media respectively. The recovery values were 98.6% for Williams' medium E and 100.3% for L-15 medium. The internal standard method was not used for quantitative purposes due to the variability of the response factor. The proposed method has potential for broad implementation in monitoring biomarkers in cell cultures.

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“…A possible answer to the former question could be the application of trial and error methods or rules of thumb techniques such as targeting the internal standard to the lower 1/3 of the working standard curve [4][5] but to the latter question no answer has been given as yet. We have recently proposed a general method to determine a region where the RF does not change with changes in the analyte and internal standard concentrations [6] and have pointed out the potential applicability of this method in the analysis of biomedical samples.…”

Section: Introductionmentioning

confidence: 99%

Improved quantification of prostaglandins in biological samples by optimizing simultaneously the relationship eicosanoid/internal standard and using liquid chromatography tandem mass spectrometry

Araujo¹,

Bjørkkjær

Berstad

et al. 2007

Prostaglandins, Leukotrienes and Essential Fatty Acids

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Although a wide variety of articles on quantification of eicosanoids by using internal standards are published every year, little has been done on how much internal standard should be added. This article demonstrates that the application of experimental design enables estimating the interaction eicosanoid/internal-standard and to select confidently an optimal amount of internal standard and a response factor (RF) for the analysis of eicosanoids in a high number of samples, where the amount of sample is limited and the unknown levels of eicosanoids are spanned in a wide range of concentrations. The results revealed that the interaction eicosanoid/internal-standard is an important factor that affects the validity of the RF and subsequently the accuracy of the analysis  Corresponding author.

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Experimental design considerations in quantification experiments by using the internal standard technique: Cholesterol determination by gas chromatography as a case study

Cited by 26 publications

References 7 publications

Optimization of a novel headspace–solid‐phase microextraction–gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices

Optimization of a novel headspace–solid‐phase microextraction–gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devices

Direct Injection of Redissolved Cell Culture Media into a Single-Column Liquid Chromatography Coupled to Mass Spectrometry for the Measurement of PGE2

Improved quantification of prostaglandins in biological samples by optimizing simultaneously the relationship eicosanoid/internal standard and using liquid chromatography tandem mass spectrometry

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