title: Determining performance parameters in qualitative multivariate methods using probability of detection (POD) curves. Case study: Two common milk adulterants.
abstract: A strategy for determining performance parameters of two-class multivariate qualitative methods was proposed. As case study, multivariate classification methods based on mid-infrared (MIR) spectroscopy coupled with the soft independent modelling of class analogy (SIMCA) technique for detection of hydrogen peroxide and formaldehyde in milk were developed. From the outputs (positive/negative/inconclusive) of the samples, which were unadulterated and adulterated at target value, the main performance parameters were obtained. Sensitivity and specificity values for the unadulterated and adulterated classes were satisfactory. Inconclusive ratios 12% and 21%, respectively, for hydrogen peroxide and formaldehyde were obtained. To evaluate the performance parameters related to concentration, Probability of Detection (POD) curves were established, estimating the decision limit, the capacity of detection and the unreliability region. When inconclusive outputs were obtained, two additional concentration limits were defined: the decision limit with inconclusive outputs and the detection capability with inconclusive outputs. The POD curves showed that for concentrations below 3.7gL-1of hydrogen peroxide and close to zero of formaldehyde, the chance of giving a positive output (adulterated sample) was lower than 5%. For concentrations at or above 11.3gL-1of hydrogen peroxide and 10mgL-1of formaldehyde, the probability of giving a negative output was also lower than 5%.
authors.affiliation: Department of Food Science, Faculty of Pharmacy (FAFAR), Federal University of Minas Gerais (UFMG), Av. Antônio Carlos, 6627, Campus da UFMG, Pampulha, 31270-010 Belo Horizonte, MG, Brazil; CAPES Foundation, Ministry of Education of Brazil, 70040-020 Brasília, DF, Brazil; Chemometrics, Qualimetric and Nanosensors Group, Department of Analytical and Organic Chemistry, Rovira i Virgili University, Marcel·lí Domingo s/n, 43007 Tarragona, Spain.
authors.forename: Carina de Souza
authors.initials: CS
authors.lastname: Gondim
authors.affiliation: Department of Food Science, Faculty of Pharmacy (FAFAR), Federal University of Minas Gerais (UFMG), Av. Antônio Carlos, 6627, Campus da UFMG, Pampulha, 31270-010 Belo Horizonte, MG, Brazil.
authors.forename: Roberto Gonçalves
authors.initials: RG
authors.lastname: Junqueira
authors.affiliation: Department of Food Science, Faculty of Pharmacy (FAFAR), Federal University of Minas Gerais (UFMG), Av. Antônio Carlos, 6627, Campus da UFMG, Pampulha, 31270-010 Belo Horizonte, MG, Brazil.
authors.forename: Scheilla Vitorino Carvalho
authors.initials: SVC
authors.lastname: de Souza
authors.affiliation: Chemometrics, Qualimetric and Nanosensors Group, Department of Analytical and Organic Chemistry, Rovira i Virgili University, Marcel·lí Domingo s/n, 43007 Tarragona, Spain. Electronic address: mariapilar.callao@urv.cat.
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Callao
authors.affiliation: Chemometrics, Qualimetric and Nanosensors Group, Department of Analytical and Organic Chemistry, Rovira i Virgili University, Marcel·lí Domingo s/n, 43007 Tarragona, Spain.
authors.forename: Itziar
authors.initials: I
authors.lastname: Ruisánchez
mesh_terms: D000818:Animals; D002417:Cattle; D005506:Food Contamination / Q000032:analysis*; D005557:Formaldehyde / Q000032:analysis*; D006861:Hydrogen Peroxide / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D005557:Formaldehyde; D006861:Hydrogen Peroxide
keywords: Method validation; Milk adulteration; Multivariate qualitative analysis; POD curves; Performance parameters; SIMCA