Digital movie-based on automatic titrations.

This study proposes the use of digital movies (DMs) in a flow-batch analyzer (FBA) to perform automatic, fast and accurate titrations. The term used for this process is "Digital movie-based on automatic titrations" (DMB-AT). A webcam records the DM during the addition of the titrant to the mixing chamber (MC). While the DM is recorded, it is decompiled into frames ordered sequentially at a constant rate of 26 frames per second (FPS). The first frame is used as a reference to define the region of interest (ROI) of 28×13pixels and the R, G and B values, which are used to calculate the Hue (H) values for each frame. The Pearson's correlation coefficient (r) is calculated between the H values of the initial frame and each subsequent frame. The titration curves are plotted in real time using the r values and the opening time of the titrant valve. The end point is estimated by the second derivative method. A software written in C language manages all analytical steps and data treatment in real time. The feasibility of the method was attested by application in acid/base test samples and edible oils. Results were compared with classical titration and did not present statistically significant differences when the paired t-test at the 95% confidence level was applied. The proposed method is able to process about 117-128 samples per hour for the test and edible oil samples, respectively, and its precision was confirmed by overall relative standard deviation (RSD) values, always less than 1.0%.

Kinetics independent spectrometric analysis using non-linear calibration modelling and exploitation of concentration gradients generated by a flow-batch system for albumin and total protein determination in blood serum.

An automatic method for kinetics independent spectrometric analysis is proposed in this study. It uses a non-linear calibration model that explores concentration gradients generated by a flow-batch analyser (FBA) for the samples, dye, and the single standard solution. The procedure for obtaining the gradients of the dye and standard solution is performed once at the beginning of analysis. The same procedure is applied thereafter for each sample. For illustration, the proposed automatic methodology was applied to determine total protein and albumin in blood serum by using the Biuret and Bromocresol Green (BCG) methods. The measurements were made by using a laboratory-made photometer based on a red and green bicolour LED (Light-Emitting Diode) and a phototransistor, coupled to a "Z" form flow cell. The sample throughput was about 50 h(-1) for albumin and 60 h(-1) for total protein, consuming about 7 microL of sample, 2.6 mL of BCG and 1.2 mL of biuret reagents for each determination. Applying the paired t-test for results from the proposed analyser and the reference method, no statistic differences at 95% confidence level were found. The absolute standard deviation was usually smaller than 0.2 g dL(-1). The proposed method is valuable for the determination of total protein and albumin; and can also be used in other determinations where kinetic effects may or may not exist.

Automatic determination of chlorine without standard solutions using a biamperometric flow-batch analysis system.

This study presents an automatic analysis system that does not require the use of standard solutions. The system uses an electrochemical flow cell for in line generation of the standards, and operates under the standard addition technique. The versatility of this system was demonstrated by the development of a one key touch fully automatic method for the determination of total available chlorine in real samples. The extremely simple, accurate and inexpensive method was based simply on the biamperometric monitoring of the well known redox reaction of chlorine with iodide ions in a flow-batch system, where the produced iodine (triiodide ions) generates an electrical current proportional to the chlorine concentration in the sample. The flow-batch parameters were optimized to maximize the sensitivity without losses on the precision of the analysis. An excellent linear dependence between the biamperometric signal and the chlorine concentration for the standard additions and a good agreement between the proposed approach and a reference method were obtained. The method was successfully applied to determine chlorine in several different bleach and chlorinated water samples (r=0.9995, LOD=8.261 x 10(-7) mol L(-1)) and could be easily extended to other oxidants and samples. Comparison to a reference method and recoveries close to 100% demonstrated the reliability of the proposed method. In addition, low residue disposal and reagent consumption, allied with high accuracy and precision, make it very promising for routine applications.