Flow Injection procedures for glycerol determination in biodiesel and manganese in water samples

Author(s)

Sidnei Gonçalves da Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2011-10-18

Examining board members

Fabio Rodrigo Piovezani Rocha; Lucio Angnes; Orlando Fatibello Filho; Pedro Vitoriano de Oliveira; Jarbas José Rodrigues Rohwedder

• Advisor: Fabio Rodrigo Piovezani Rocha

Abstract

Flow injection procedures based on solenoid micro pump were developed for free and total glycerol determination in biodiesel samples and manganese in fresh water. In a first work, free glycerol was determined by spectrophotometry, after glycerol oxidation by periodate, yielding formaldehyde, followed by formation of the colored product 3,5-diacetil-1,4-dihidrolutidine (DDL) upon reaction with acetylacetone. The analyte was extracted with water in replacement of organic solvents. A linear response was observed from 5 to 50 mg L-1, and detection limit was estimated as 1 mg L-1 (99.7% confidence level) equivalent to 0.0004% (w/w), 50 times lower than the threshold value established by Brazilian, European and American regulations. The coefficient of variation was lower than 1.5% (n=10) and sampling rate was estimated at 34 samples h-1, consuming 340 µg of KIO4 and 15 mg of acetylacetone per determination. The same reaction was exploited for fluorimetric detection of free and total glycerol in biodiesel, and glycerol total was quantified after saponification of mono-, di- and triglycerides remaining in biodiesel. To free glycerol determination a linear response was observed from 5 to 70 mg L-1, with a detection limit of 0.5 mg L-1, which corresponds to 0.0002% (w/w) in biodiesel, and coefficient of variation was lower than 1.0% (n=10). To total glycerol determination, a linear response was observed from 25 to 300 mg L-1, with a detection limit of 1.5 mg L-1, and coefficient of variation of 1.4% (n=10). The sampling rate was estimated at 35 and 30 samples h-1, to free and total glycerol, respectively. The results obtained to biodiesel samples agreed at the 95% confidence level with reference procedures. The formation of the Mn(III)/EDTA complex was exploited for manganese determination in water. Mn(II) was oxidized in a reactor containing lead dioxide immobilized on polyester. Long pathlength spectrometry was exploited to increase sensitivity, aiming to reach the threshold limit established by environmental legislation. A linear response was observed from 25 to 1500 µg L-1, with a detection limit of 6 µg L-1(99.7% confidence level). Sample throughput and coefficient of variation were 36 samples h-1 and 2.6% (n=10), respectively, consuming 500 µg of EDTA. The amount of lead in the residue corresponds to 250 µg per determination, and it is possible to perform up to 1600 measurements. Interferences by organic matter were observed and active charcoal was employed to remove the interfering species. Results were in agreement with those attained by GF AAS at the 95% confidence level. (AU)

• FAPESP's process: 08/01045-0 - Multicommuted flow systems for determination of free glycerol, manganese and total organic carbon in different sample matrices
• Grantee: Sidnei Gonçalves da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate