Kinetic-spectrophotometric method for the determination of trace amounts of bromide in seawater

A novel simple, sensitive and rapid kinetic-spectrophotornetric method is proposed for the determination of trace amounts of bromide. The method is based on its catalytic effect on the oxidation of methylene blue (MB) by hydrogen peroxide in strongly acidic solution. The oxidation reaction is activated by large amounts of chloride and can be monitored spectrophotometrically by measuring the decrease in the absorbance of MB at 746 run. The determination of bromide is performed by a fixed-time method at the first 100 s from the initiation of the reaction. Unlike other kinetic-spectrophotornetric methods for the determination of bromide, the proposed method does not require heating the solution. Bromide can be determined in the range from 80 to 960 mu g l(-1) with the detection limit of 35 mu g l(-1). The relative standard deviation of ten replicate determination of 480 mu g l(-1) bromide was 1.4%. The influence of potential interfering ions was studied. The proposed method was satisfactorily applied to the determination of bromide in seawater without interfering effect from chloride ion.</p

Characterization of Pieces of Paper That Form Reagent Containers for Use as Portable Analytical Devices

Reagent-deposited pieces of paper were characterized by the use of a compact conductometer, a compact pH sensor, and a conventional spectrophotometer to assess their suitability for use as reagent containers. The pieces of paper were fabricated by wax printing to form a limited hydrophilic area to which a consistent volume of an aqueous reagent could be added. The pieces of paper without the reagent increased the conductivity of water gradually because of the release of sodium salts, whereas pH of NaOH decreased because of the acidity of the functional groups in the paper. Three reagents, sulfamic acid as an acid, Na2CO3 as a base, and BaCl2 as a metal salt, were deposited on the pieces of paper to evaluate their ability to release from the pieces of paper. Sulfamic acid and Na2CO3 were released in quantities of 58 and 73% into water after 420 s, whereas 100% of BaCl2 was released after 480 s. The conductometric titrations of NaOH, HCl, and Na2SO4, and the spectrophotometry of Fe2+ were examined using the pieces of paper that contained sulfamic acid, Na2CO3, BaCl2, and 1,10-phenanthroline. Titrations using the pieces of paper suggested that the reagents were quantitatively released into the titrant, which resulted in a linear relationship between the endpoints and the equivalent points. In 120 s of soaking time, 60-70% of the reagents were released. The spectrophotometric measurements of Fe2+ indicated that when an excess amount of the reagents was deposited onto the pieces of paper, they nonetheless sufficiently fulfilled the role of a reagent container

Sequential flow injection analysis with potentiometric detection for the determination of ammonium and urea in human saliva

info:eu-repo/semantics/publishedVersio

Dual-Purpose Photometric-Conductivity Detector for Simultaneous and Sequential Measurements in Flow Analysis

This work presents a new dual-purpose detector for photometric and conductivity measurements in flow-based analysis. The photometric detector is a paired emitter-detector diode (PEDD) device, whilst the conductivity detection employs a capacitively coupled contactless conductivity detector (C4D). The flow-through detection cell is a rectangular acrylic block (ca. 2 x 2 x 1.5 cm) with cylindrical channels in Z-configuration. For the PEDD detector, the LED light source and detector are installed inside the acrylic block. The two electrodes of the C4D are silver conducting ink painted on the PEEK inlet and outlet tubing of the Z-flow cell. The dual-purpose detector is coupled with a sequential injection analysis (SIA) system for simultaneous detection of the absorbance of the orange dye and conductivity of the dissolved oral rehydration salt powder. The detector was also used for sequential measurements of creatinine and the conductivity of human urine samples. The creatinine analysis is based on colorimetric detection of the Jaffe reaction using the PEDD detector, and the conductivity of the urine, as measured by the C4D detector, is expressed in millisiemens (mS cm(-1))

Microfluidic paper-based analytical device (µPAD) for salivar ammonia/ammonium

info:eu-repo/semantics/publishedVersio

Simple and Highly Sensitive Spectrophotometric Flow Injection Method for the Determination of Iodate in Iodized Salt

Abstract A simple and rapid flow injection (FI) spectrophotometric method is newly proposed for the determination of iodate in iodized salt. The method is based on the oxidation of 2-Chloro-10-[3-(4-methyl-1-piperazinyl) propyl] phenothiazine maleate (prochlorperazine / PCP) by iodate in acidic medium to form a red product: the increase in absorbance of the oxidation product is detected at 525 nm. Various chemical and physical experimental variables of the FI method were optimized, and the effect of interfering ions was also examined. Under the optimal conditions, iodate can be determined in the range of 1x10 -6 to 3x10 -5 mol l -1 with high precision (RSD=0.1% at 8x10 -6 mol l -1 of iodate, n=15). The detection limit (S/N=3) of the method was down to 8.5x10 -8 mol l -1 . The proposed method was validated against the FI with I 3 --starch reaction and the conventional titration method: the results obtained for three methods were statistically analyzed by the analysis of variance (ANOVA). It was found that there is no significant difference among these methods at 95% confidence. The method was applied to the determination of iodate in iodized salt

Quality control of gasohol using a micro-unit for membraneless gas diffusion

This work describes the development of a new spectrophotometric flow technique suitable for monitoring of ethanol content in gasohol fuel. Membraneless gas-diffusion (MBL-GD) was applied with one-step aqueous extraction of gasohol (1:2 gasohol/water). Segments of aqueous extract and color developing reagent were allowed to flow into two separate channels in the MBL-GD device. Inside the device, ethanol vapor can diffuse across a small headspace between the two channels (donor and acceptor). Introduction of an air-segment behind the zone of acceptor reagent to stop dispersion of the colored zone greatly improves the rapidity of analysis using this MBL-GD technique. Two methods were developed for quality control of gasohol by measuring ethanol content. Method I is suitable for direct calibration of E5 and E10. Method II is recommended for E20. These methods have high accuracy with good precision (% RSD: 1 to 4.9, n&#8201;=&#8201;45) and have a sample throughput of 26 samples per hour. E10 samples were compared with analysis using a standard GC method. </p

Simple Flow-Based System with an In-Line Membrane Gas–Liquid Separation Unit and a Contactless Conductivity Detector for the Direct Determination of Sulfite in Clear and Turbid Food Samples

This study presents a simple flow-based system for the determination of the preservative agent sulfite in food and beverages. The standard method of conversion of sulfite ions into SO2 gas by acidification is employed to separate the sulfite from sample matrices. The sample is aspirated into a donor stream of sulfuric acid. A membrane gas&ndash;liquid separation unit, also called a &lsquo;gas-diffusion (GD)&rsquo; unit, incorporating a polytetrafluoroethylene (PTFE) hydrophobic membrane allows the generated gas to diffuse into a stream of deionized water in the acceptor line. The dissolution of the SO2 gas leads to a change in the conductivity of water which is monitored by an in-line capacitively coupled contactless conductivity detector (C4D). The conductivity change is proportional to the concentration of sulfite in the sample. In this work, both clear (wine) and turbid (fruit juice and extracts of dried fruit) were selected to demonstrate the versatility of the developed method. The method can tolerate turbidity up to 60 Nephelometric Turbidity Units (NTUs). The linear range is 5&ndash;25 mg L&minus;1 SO32&minus; with precision &lt;2% RSD. The flow system employs a peristaltic pump for propelling all liquid lines. Quantitative results of sulfite were statistically comparable to those obtained from iodimetric titration for the wine samples