Fe determination in environmental water using ICP-MS-IDA

Treball Final de Grau en Química. Codi: QU0943. Curs acadèmic 2013-201

Recertification of 25-hydroxyvitamin D standards by Isotope Pattern Deconvolution (IPD)

Vitamin D (VTD) is an important prohormone widely known since its deficiency is directly related to development of rickets in children and osteoporosis in adults. Furthermore, recent studies have demonstrated that vitamin D has also an important role in non-skeletal conditions such as autoimmune diseases, cardiovascular diseases and cancer, among others. This vitamin can be found in two main forms: vitamin D2 and vitamin D3. The metabolism of both forms of vitamin D are subjected to a first hydroxylation in the liver to form 25-hydroxyvitamin D (25(OH)D) and then to a second one in the kidney to form 1,25-dihydroxyvitamin D (1,25(OH)2D), the active form of vitamin D. Nevertheless, the measurement of 25(OH)D in serum samples is preferred test for the assessment of vitamin D status over the 1,25(OH)2D. There are two main reasons for this choice: the longer lifetime (3 weeks versus 4 h) and its higher concentration levels (ng/mL versus pg/mL)[2]. Over the last years, a dramatic rise in vitamin D testing (as 25(OH)D) has been observed, due to two main reasons: the increased number of patients with VTD deficiency and the increase of the role of VTD as a biomarker related to several diseases. In this work we propose a recertification approach for 25(OH)D2/D3 solvent standards based on Isotope Pattern Deconvolution (IPD) using NIST SRM 2972 as reference material. This approach could help to meet the requirements for external standardization criteria using in-house calibration curves

Determination of selected endogenous anabolic androgenic steroids and ratios in urine by ultra high performance liquid chromatography tandem mass spectrometry and isotope pattern deconvolution

An isotope dilution mass spectrometry (IDMS) method for the determination of selected endogenous anabolic androgenic steroids (EAAS) in urine by UHPLC–MS/MS has been developed using the isotope pattern deconvolution (IPD) mathematical tool. The method has been successfully validated for testosterone, epitestosterone, androsterone and etiocholanolone, employing their respective deuterated analogs using two certified reference materials (CRM). Accuracy was evaluated as recovery of the certified values and ranged from 75% to 108%. Precision was assessed in intraday (n = 5) and interday (n = 4) experiments, with RSDs below 5% and 10% respectively. The method was also found suitable for real urine samples, with limits of detection (LOD) and quantification (LOQ) below the normal urinary levels. The developed method meets the requirements established by the World Anti-Doping Agency for the selected steroids for Athlete Biological Passport (ABP) measurements, except in the case of androsterone, which is currently under study

Evaluation of uncertainty sources in the determination of testosterone in urine by calibration-based and isotope dilution quantification using ultra high performance liquid chromatography tandem mass spectrometry

Three quantification methodologies, namely calibration with internal standard (Cal-IS, non-weighted), weighted calibration with internal standard (wCal-IS) and isotope pattern deconvolution (IPD) have been used for the determination of testosterone in urine by LC-MS/MS. Uncertainty has been calculated and compared for the three methodologies through intra- and inter-laboratory reproducibility assays. IPD showed the best performance for the intra-laboratory reproducibility, with RSD and combined uncertainty values below 4% and 9% respectively. wCal-IS showed similar performance, while Cal-IS where not constant and clearly worse at the lowest concentration assayed (2 ng/mL) reaching RSD values up to 16%. The inter-laboratory assay indicated similar results although wCal-IS RSD (20%) was higher than IPD (10%) and Cal-IS get worse with RSD higher than 40% for the lowest concentration level. Uncertainty budgets calculated for the three procedures revealed that intercept and slope were the most important factors contributing to uncertainty for Cal-IS. The main factors for wCal-IS and IPD were the volumes of sample and/or standard measured.The authors acknowledge financial support from the Generalitat Valenciana (Research group of excellence Prometeo II 2014/023 and Collaborative Research on Environment and Food Safety ISIC/2012/016), as well as University Jaume I for project PB1-1B2013-55. Finally, the authors are grateful to the Serveis Centrals d'Instrumentació Científica (SCIC) of University Jaume I for using Acquity and TQD instruments

Espectrometría de masas de dilución isotópica y deconvolución de perfiles isotópicos aplicada a problemas complejos: Determinación de esteroides en muestras clínicas y drogas en aguas residuales

Compendi d'articlesEn la presente tesis se presenta una cuantificación alternativa basada en IDMS: la deconvolución de perfiles isotópicos (IPD). Si bien es una técnica ampliamente utilizada en estudios de especiación, su uso para análisis molecular es todavía novedoso. Se trata de una herramienta matemática, basada en regresión lineal múltiple, capaz de hallar la contribución –como fracción molar– de cada compuesto al perfil isotópico de una mezcla de un compuesto natural y su homólogo marcado isotópicamente, sin necesitar curva de calibrado. IPD se aplicó a la determinación de esteroides androgénicos endógenos en orina –evaluada en términos de incertidumbre y de cuantificación de hasta 4 metabolitos–, estudios enfocados a análisis clínicos –certificación de estándares de vitamina D y cuantificación de estrógenos en suero–, y a drogas de abuso en aguas residuales –para estudios de epidemiología basada en aguas residuales–.Programa de Doctorat en Cièncie

Determination of testosterone in urine by UHPLC-MS/MS using isotope pattern deconvolution

Treball Final de Màster Universitari en Tècniques Cromatogràfiques Aplicades (Pla de 2013). Codi: SIY009. Curs acadèmic 2014-201

Development and Validation of the Simultaneous Measurement of Estrone and 17β-Estradiol in Serum by LC-MS/MS for Clinical Laboratory Applications

A straightforward analytical method for the determination of estrone (E1) and 17β-estradiol (E2) at ultra-low levels in serum samples by LC-MS/MS has been developed and validated. This method entails an extraction and derivatization with dansyl chloride followed by separation with a C18 column. A comparison of the developed LC-MS/MS method against our routine immunoassay shows a good correlation for E2 while an important negative bias is observed for E1 by RIA. The later comparison for E1 shows the need to switch from the current routine automated immunoassays to highly-sensitive LC-MS/MS quantifications in order to provide accurate and reliable clinical results, especially at very low levels

Re-certification of hydroxyvitamin D standards by isotope pattern deconvolution

Background Vitamin D testing in analytical clinical laboratories has been experiencing a rapid increase of demand over the last years, as it plays a key role in several disorders. Due to the narrow ranges of medical significance regarding its concentration levels in human serum, accurate and precise determinations of vitamin D metabolites are required. Methods We present an isotope dilution mass spectrometry quantification method for the re-certification of routine commercial standards used in method validation steps, isotope pattern deconvolution (IPD) based on LC-MS/MS. Results IPD allowed to compensate for the observed biases of +4.7% for 25(OH)D3, −29% for 25(OH)D2 and −30% for 24,25(OH)2D3 standard concentrations, respectively in an easy, cheap and straightforward way. Conclusions Is has been observed that, in some cases, discrepancies may exist between stated purity or amount of routinely used commercial standards and actual values, which would lead to unwanted bias in the developed methodologies. The present correction has helped meeting the regulations established by international standardization programs, including Vitamin D Standardization Program (VDSP)

Method development and validation for the determination of selected endocrine disrupting compounds by liquid chromatography mass spectrometry and isotope pattern deconvolution in water samples. Comparison of two extraction techniques

n the present work two different extraction methodologies have been developed and validated for the determination of t-octylphenol (OP) and the technical mixture of nonylphenol (NP) (both, priority substances of EU Water Policy) and bisphenol A (BPA) in water samples. BPA has been quantified by isotope dilution mass spectrometry and isotope pattern deconvolution (IPD) for the first time taking advantage of 13C-isotopic analogues as internal standards, together with the previously studied alkylphenols. After preconcentration of the selected compounds, samples were analyzed by ultra high pressure liquid chromatography and tandem mass spectrometry (UHPLC-MS/MS). For this purpose two extraction methodologies were proposed and compared: a routine extraction methodology based on solid-phase extraction (SPE), and a non-conventional technique based on hollow fiber liquid phase microextraction (HF-LPME). The sought methodologies were satisfactorily validated in drinking water, surface water and effluent wastewater at two concentration levels, 0.1 and 1 µg/L for alkylphenols and 0.5 and 5 µg/L for BPA. Recoveries within 89-113% and 91-113% were obtained for HF-LPME and SPE respectively, with acceptable coefficients of variation in all cases according to SANCO guidelines. In addition, the use of isotope pattern deconvolution calculations provided the concentration of each analyte without the need to perform any calibration curve. Finally, a comparison of both methodologies is included, showing that while HF-LPME provides shorter sample preparation time and overall cost, SPE extraction and manipulation is highlighted as user friendly

Re-certification of hydroxyvitamin D standards by isotope pattern deconvolution

peer reviewedBackground: Vitamin D testing in analytical clinical laboratories has been experiencing a rapid increase of demand over the last years, as it plays a key role in several disorders. Due to the narrow ranges of medical significance regarding its concentration levels in human serum, accurate and precise determinations of vitamin D metabolites are required. Methods: We present an isotope dilution mass spectrometry quantification method for the re-certification of routine commercial standards used in method validation steps, isotope pattern deconvolution (IPD) based on LC-MS/MS. Results: IPD allowed to compensate for the observed biases of +4.7% for 25(OH)D3, −29% for 25(OH)D2 and −30% for 24,25(OH) 2 D 3 standard concentrations, respectively in an easy, cheap and straightforward way. Conclusions: Is has been observed that, in some cases, discrepancies may exist between stated purity or amount of routinely used commercial standards and actual values, which would lead to unwanted bias in the developed methodologies. The present correction has helped meeting the regulations established by international standardization programs, including Vitamin D Standardization Program (VDSP). © 2019 Elsevier B.V