A tutorial on the validation of qualitative methods: From the univariate to the multivariate approach

López, María Isabel; Callao, M. Pilar; Ruisánchez, Itziar

doi:10.1016/j.aca.2015.06.032

Cited by 105 publications

(36 citation statements)

References 37 publications

(45 reference statements)

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“…Figure (c) shows the scores for the model (2i)P‐F/B(f). As it is shown, four ‘unknown’ samples were classified in ‘Fuerte’ class while a Mexican oil sample was situated on the discriminant line between the two predefined classes: this is an inconclusive sample …”

Section: Resultsmentioning

confidence: 99%

Differentiation of avocados according to their botanical variety using liquid chromatographic fingerprinting and multivariate classification tree

et al. 2019

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Background The oil content, composition and marketing threshold value of an avocado depends on the cultivar hence, identifying the cultivar of the avocado fruit is desirable. However, analytical methods have not been reported with this aim. Results A multivariate classification tree method was proposed to discriminate three commercial botanical varieties of avocado: Hass, Fuerte and Bacon, using high‐performance liquid chromatography coupled to a charged aerosol detector (HPLC‐CAD). Prior to the chromatographic analysis the avocados were lyophilized and then the oil fraction was extracted using a pressurized liquid extraction system. Normal and reverse phase liquid chromatography were applied in order to obtain the chromatographic fingerprint for each sample. Soft independent modelling of class analogies (SIMCA) and partial least‐squares discriminant analysis (PLS‐DA) were applied. Classification quality metrics were determined to evaluate the performance of the classification. Several strategies to develop the classification models were employed. Finally, the useful application of ‘classification trees’ methodology, which has been scarcely applied in the field of analytical food control, was evaluated to perform a multiclass classification. Conclusion Discrimination of the three botanical varieties was achieved. The best classification was obtained when the PLS‐DA is applied on the normal‐phase chromatographic fingerprints. Classification trees are showed to be useful tools that provide complementary information to single concatenated models showing different results from the same prediction sample set. © 2019 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Differentiation of avocados according to their botanical variety using liquid chromatographic fingerprinting and multivariate classification tree

et al. 2019

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“…Os intervalos de recuperação aceitáveis descrito na literatura para a determinação de compostos orgânicos traço, em geral, devem estar na faixa de 70-120%. 13,20,22 Em relação às diferenças de recuperação na classe de hidrocarbonetos estudados cabe explicar que no gráfico estes estão organizados em ordem crescente de massa molar, o que confere uma diminuição da volatilidade da esquerda (C 14 ) para a direita (C 30 ). De maneira geral, observam-se melhores resultados de recuperação para os compostos de cadeia carbônica entre (C 16 -C24) em relação ao composto C 14.…”

Section: Ensaios De Adição E Recuperação Dos Biomarcadoresunclassified

“…Por esse motivo, a recuperação deve ser avaliada na faixa de concentração esperada para o composto de interesse. Isso foi feito adicionando a substância em pelo menos três diferentes concentrações, próximo ao limite de quantificação, próximo à concentração máxima permitida pelo método em teste e em uma concentração próxima à média da faixa de trabalho 13,22 .…”

Section: Figuraunclassified

“…Estes valores encontram-se dentro da faixa aceitável estabelecida entre 70 e 120%. 13,20,22 17 Em relação a perfil T 4 , os valores de desvio para as profundidades 0-5 cm; 106-111 cm; 203-208 cm; 295-300 cm; 369-343 cm ficaram na faixa de 2,87 a 6,11 %; 4,01 a 5,41 %; 2,98 a 5,10%; 4,01 a 7,01% e 3,05 a 5,98 % respectivamente, sendo todos considerados satisfatórios.…”

Section: Hidrocarbonetos Alifáticos E áCidos Graxosunclassified

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Evaluation of the Analytical Method Applied to Geochemical Biomarkers in a Paleoenvironmental Study of Coastal Barrier Associated to Conceição Lagoon (Florianópolis / SC)

Ferreira

Madureira

2016

Rev. Virtual Quim.

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Geochemical biomarkers play an important role in studies of palaeoenvironment reconstruction based on historical variation of sedimentary records. However, a great number of steps are usually involved for their analytical determination including extraction, clean up, derivatization (esterification and silanization) and individual calibration curves for accurate results. Thus, prior to the extraction an optimization procedure may be required to verify possible losses through the analytical method. In the present work distinct reaction times during the sterification step, NaCl concentration to separate the aqueous and organic phases and extracting solvents were assessed. The best working conditions achieved were reaction time of 8 hours, NaCl solution 20 % (m/v) and hexane. For the biomarkers analytical parameters sensitivity, linearity (R 2 ), LOD and LOQ were obtained with external calibration curves and checked against those obtained with spiked sediment. The results showed no significant differences for the analytical parameters. Due to the lack of certificate material, the precision and accuracy were studied by recovery tests. Solutions containing mix of aliphatic hydrocarbons, alcohols, carboxylic acids, sterols and ketones were added to sediment samples and submitted to all the steps of the process. This mix was left in contact with sediment samples for 1 hour, 24 hours and 7 days, in 3 concentration levels. The recovery were all within the acceptable range 70-120% and RSD < 10%. The analytical method was applied to samples taken from two single sediment cores (stations T3 and T4 with 525 cm and 364 cm depth, respectively) collected at the Mozambique-Barra da Lagoa (Florianópolis -Santa Catarina) beach. A preliminary assessment of the hydrocarbon distribution indicated a mixed source of organic matter through the T3 profile while the T4 core was dominated by terrestrial hydrocarbons with predominance of C3 plants.Keywords: Optimization; geochemical biomarkers; paleoenvironmental study; Conceição Lagoon. ResumoOs biomarcadores geoquímicos são de grande importância em estudos de reconstrução de paleoambientes. Devido ao grande número de etapas envolvidas na sua determinação, tais como extração com solvente, fracionamento, derivatização (esterificação e silanização) e quantificação, é preciso garantir que os resultados obtidos sejam confiáveis. Desta forma, antes das extrações dos biomarcadores nos perfis sedimentares deve-se fazer uma otimização de forma a identificar possíveis perdas envolvidas e avaliar o método analítico que será utilizado. No presente trabalho foram avaliadas a etapa de esterificação (tempos de reação e forma de extração). As melhores condições de trabalho foram com tempo de reação de 8 horas, solução de NaCl a 20% (m/v) e hexano. A sensibilidade analítica, linearidade (R 2 ), LOD e LOQ obtidos por meio de curvas de calibração externa para os biomarcadores não foram significativamente diferentes dos resultados obtidos por adição dos padrões em sedimento. A precisão e exatidão do...

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“…In this study, an enzymatic sensor was applied as a qualitative screening assay to detect PDE5 inhibitors in sex‐enhancement products. This biological‐effect‐based assay employs fluorescence detection and is based on measuring inhibition of PDE5 activity, a pharmacological mechanism shared among the adulterants.…”

Section: Introductionmentioning

confidence: 99%

Phosphodiesterase (PDE5) inhibition assay for rapid detection of erectile dysfunction drugs and analogs in sexual enhancement products

Santillo

Mapa

2018

Drug Testing and Analysis

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Products marketed as dietary supplements for sexual enhancement are frequently adulterated with phosphodiesterase-5 (PDE5) inhibitors, which are erectile dysfunction drugs or their analogs that can cause adverse health effects. Due to widespread adulteration, a rapid screening assay was developed to detect PDE5 inhibitors in adulterated products. The assay employs fluorescence detection and is based on measuring inhibition of PDE5 activity, the pharmacological mechanism shared among the adulterants. Initially, the assay reaction scheme was established and characterized, followed by analysis of 9 representative PDE5 inhibitors (IC , 0.4-4.0 ng mL ), demonstrating sensitive detection in matrix-free solutions. Next, dietary supplements serving as matrix blanks (n = 25) were analyzed to determine matrix interference and establish a threshold value; there were no false positives. Finally, matrix blanks were spiked with 9 individual PDE5 inhibitors, along with several mixtures. All 9 adulterants were successfully detected (≤ 5 % false negative rate; n = 20) at a concentration of 1.00 mg g , which is over 5 times lower than concentrations commonly encountered in adulterated products. A major distinction of the PDE5 inhibition assay is the ability to detect adulterants without prior knowledge of their chemical structures, demonstrating a broad-based detection capability that can address a continuously evolving threat of new adulterants. The PDE5 inhibition assay can analyze over 40 samples simultaneously within 15 minutes and involves a single incubation step and simple data analysis, all of which are advantageous for combating the widespread adulteration of sex-enhancement products.

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A tutorial on the validation of qualitative methods: From the univariate to the multivariate approach

Cited by 105 publications

References 37 publications

Differentiation of avocados according to their botanical variety using liquid chromatographic fingerprinting and multivariate classification tree

Differentiation of avocados according to their botanical variety using liquid chromatographic fingerprinting and multivariate classification tree

Evaluation of the Analytical Method Applied to Geochemical Biomarkers in a Paleoenvironmental Study of Coastal Barrier Associated to Conceição Lagoon (Florianópolis / SC)

Phosphodiesterase (PDE5) inhibition assay for rapid detection of erectile dysfunction drugs and analogs in sexual enhancement products

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