Banca de QUALIFICAÇÃO: BEATRIZ DO NASCIMENTO OLIVEIRA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : BEATRIZ DO NASCIMENTO OLIVEIRA
DATE: 03/04/2023
TIME: 09:00
LOCAL: Google Meet
TITLE:

Development of a colorimetric method for determination of acid phosphatase aiming forensic applications.

KEY WORDS:

Sexual crimes; Acid phosphatase; Colorimetric detection; Forensic chemistry

PAGES: 60
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

Sexual crimes are those that threaten sexual dignity and freedom, characterized as a form of violence with a higher incidence of female gender. In this way, identifying biological fluids such as blood, saliva and semen is one of the crucial steps in the analysis of crime scenes or samples for forensics. In this sense, the presence of seminal fluid (semen) on the victim or on clothes, for example, may constitute criminal evidence. Semen has a complex composition, however, the acid phosphatase (AP) enzyme can be used as a marker, since it has concentrations in seminal fluid up to 400 times higher compared to other body fluids. The objective is to develop a methodology with colorimetric detection test that uses a small amount of sample, is likely to be used in the field, with a quick and selective response, thus helping to confirm criminal evidence. The proposed method is based on the detection of AP using ascorbic acid 2-phosphate (AAP) as substrate, which, after enzyme action, releases inorganic phosphate and reduced ascorbic acid (AAr) at pH 5.0, which is used to detect the enzyme in the medium. In this case, AAr reacts with Fe(III) ions leading to the formation of Fe(II) and oxidized ascorbic acid (AAo). Therefore, the reaction of Fe(II) ions generated in situ with K3[Fe(CN)6] in an acid medium leading to the formation of Prussian blue (AZP, Fe4[Fe(CN)6]3), a colloid dark blue (λ = 710 nm). Using AZP as a colorimetric probe with λmax > 500 nm avoids possible spectral interference due to the composition of complex samples. Initially, the main reaction parameters were optimized using AAr, under the best analytical performance conditions Fe(III) 0.17 mM, K3Fe(CN)6 1.7 mM, both in HNO3 0.4 M. The stability of the AZP was improved using polyvinylpyrrolidone (PVP) at 0.20% (w/v). In order to simplify the method, it was verified that there is no statistical difference (95% confidence) between the analytical curves for AAr (5 to 40 µM) adding the reagents separately or as a single mixture [Fe(III) + K3Fe(CN)6 + PVP]. Then, optimized conditions were applied to detect AP, using AAP (0.75 mU) as substrate at pH 5.0 (HAc/NaAc, 100 mM). In these conditions, an analytical curve for AP was obtained, with a linear range from 0.50 to 3.0 U L -1, corresponding to the equation A710 nm = 0.32×CAP + 0.016 (n = 8, r = 0.9964) and LOD = 0.004 U L-1. As a proof of concept, the method was successfully applied on a real semen sample (CAAE: 58121322.7.0000.5013) in a qualitative evaluation after dilution of the semen, applied on the surface of cloth (cotton), swab and in the device of paper. Finally, the proposed method proved to be applicable in different situations, with a response of up to 20 min, being an alternative to use in the field and contributing to a quick decision-making when necessary.

BANKING MEMBERS:
Externo(a) à Instituição - Maria do Carmo Hespanhol
Interno(a) - 1869296 - CINTYA D'ANGELES DO ESPIRITO SANTO BARBOSA
Presidente - 1613338 - JOSUE CARINHANHA CALDAS SANTOS
Externo(a) à Instituição - RODOLFO DE MELO MAGALHÃES SANTANA