Delgadillo, Ivonne

Galvis-Sánchez, Andrea C.

Ganito, Susana

Rangel, António O. S. S.

Tóth, Ildikó V.

English

Repositório Institucional da Universidade Católica Portuguesa

Andrea C. Galvis-Sánchezab, Ildikó V.Tóthc, Susana Ganitobd, Ivonne Delgadillob and António O.S.S. RangelaaCBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, PortugalbDepartamento de Química, Universidade de Aveiro, Aveiro, PortugalcREQUIMTE, Serviço de Química-Física, Faculdade de Farmácia, Universidade de Porto, Porto, PortugaldPascoal e Filhos S.A. Gafanha da Nazaré, Aveiro, PortugalDevelopment of two methods for monitoring codfish desalting process based on flow injection analysis and Fourier-mid infrared spectroscopyTraditional analytical determinations for chloride are precise but are time consuming and difficult to perform for routine analysis. A pronounced tendency towards “clean methods” was observed in the recent years: Flow injection analysis (FIA) technique permits: automatic sample processing, high repeatability, adaptability to miniaturization, waste and reagent reduction. Mid-infrared spectroscopy (MID-IR) allows in-situ monitoring and real-time analytical determinations.The main objective of the present work was to compare the performance of a flow-injection (FIA) system and a mid-infrared (MID-IR) spectroscopy procedure for the determination of sodium chloride in the cod muscle and desalting solutions during cod desalting process.1. Dried salted codfish 2. Desalting process for 30 h 3. Samplingc) Reference method: volumetric determinations based on Mohr and Volhard methods  Chloride determination by:Figure 1. FIA manifold for theturbidimetric determination of chloride: S,sample or standard; C1, water; C2, nitricacid (2 mol L-1); R, silver nitrate (1x10-2mol L-1); L’, sample loop (15 µL); L”,reagent loop (60 µL); C, commutator; KR,200 cm knitted reactor; , UV/VISspectrophotometer; W, waste.Figure 2. MID-IR ATR System.a) Flow injection analysis b) Mid-infrared spectroscopy123Sampling and AnalysisTable 2. Analytical characteristics of the FIA and MID-IR ATRsystems for the determination of sodium chloride.Operation ConditionsFigures of MeritTable 1. Characteristics of the FIA and IR-Spectroscopy methods FIA FT-MID Mode Turbidimetric Attenuated total reflection Detection system Spectrophotometer (CCD-array detector, Ocean Optics) Fourier Infrared – Spectrometer (Spectrum BX, Perkin–Elmer) Spectral range 9090 – 50000 cm-1 (λ=425 nm) 600 – 4000 cm-1  Accessories  Peristaltic pump (Gilson, Manipuls 3) ATR Golden Gate (Specac)  Cuvette holder (Ocean Optics)   Optical fibers (i.d: 300 μm)   Tungsten/halogen light source (DH-200, Mikropack)  Software SpectraSuite Spectrum v.5.3.1 and CATS program[1]  ResultsConclusions: The flow analysis system was shown to be an accurate methodology, rapid and convenient alternative, when applied to the determination of chloride in the desaltingsolutions. Technological aspects associated to codfish processing (i.e. cod freshness, salting and drying methods) will influence the desalting process and might also affect theturbidimetric NaCl determination. Salt content in cod fish and desalting cod solutions was predicted with good results by using MID-IR, however more data should be incorporated into the models in order tocreate a robust way of prediction of the NaCl concentration.AcknowledgementsThe first author acknowledges the Fundação para a Ciência e a Tecnologia (Portugal) via the fellowship ref. SFRH/BPD/37890/2007Reference[1] Barros, A. 1999. Contribution à la sélection et la comparaison de variables caractéristiques. Ph. D. Thesis. Institut National Agronomique Paris-Grignon Paris. France.-0.050.150.350.550.750.951.150 500 1000 1500 2000 2500Elapsed Time (s)Absorbancea)y = 0.0021x - 0.0472R2 = 0.9994-0.050.150.350.550.750.951.151.350 200 400 600Concentration (mg L-1)AbsorbanceAbsorbanceb)Figure 3. Flow injection peaks (a) of chloride working standardsolutions and codfish extracts; calibration curve (b) from 0.05 to0.6 g L-1 NaCl.y = 0,991x + 0,460LV = 2R2 = 0,9810.05.010.015.020.025.00 5 10 15 20Reference NaCl concentration (%)Predicted NaCl concentration (%)Predicted NaCl concentration (%)Figure 4. PLS1 regression of spectral data of sodiumchloride in cod fish extracts.y = 1,002x - 0,051LV = 4R2 = 0,930-0.10.40.91.41.92.42.93.40 0.5 1 1.5 2 2.5 3 3.5Reference NaCl concentration (%)Predicted NaCl concentration (%)Figure 5. PLS1 regression of spectral data of sodiumchloride in desalting solution samples. FIA FT-MID LOD (g L-1) 0.04 5.0 LOQ (g L-1) 0.13 16.0 Working range (g L-1) 0.05 – 0.6 0 – 200 Determination rate / h 40 20 Reagent consumption per assay  Not used Silver Nitrate     6.0 mg  Polyvinyl alcohol     3.0 mg  Nitric acid 3.1 g  LOD: limit of detection LOQ: limit of quantification  

Development of two methods for monitoring codfish desalting process based on flow injection analysis and Fourier-mid infrared spectroscopy

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Development of two methods for monitoring codfish desalting process based on flow injection analysis and Fourier-mid infrared spectroscopy

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