On-line monitoring of glucose and penicillin by sequential injection analysis

An overview of sequential injection chromatography

New generation of sequential injection analysis (SIA) called sequential injection chromatography (SIC) has already been consolidated as a good alternative of high performance liquid chromatography (HPLC) for fast analysis of simple samples. Benefits of flow methods are automation, miniaturization and low sample and mobile phase consumption. Implementation of short monolithic chromatographic column into SIA opens new area-on-line chromatographic separation of multi-compound sample in low-pressure flow system, with the advantage of flow programming and possibility of sample manipulation. In the presented review the potential of SIC and its comparison with HPLC for determination of pharmaceutical mixtures is discussed and outlines past and recent trends focused on separation with SIC.

Determination of catecholamines by flow-injection analysis and high-performance liquid chromatography with chemiluminescence detection

A chemiluminescence (CL) detection of catecholamines [norepinephrine (NE), epinephrine (E), dopamine (DA) and L-dopa (LD)] is described for the flow-injection (FI) and high-performance liquid chromatographic (HPLC) determination of these compounds. The detection method is based on the inhibition effect of catecholamines (CAs) on the CL reaction of luminol with iodine in the alkaline medium. The proposed FI method allows the determination of CAs in pharmaceutical preparations for the purpose of drug quality control. The calibration curves show good linearity in the concentration range of: 1.1-20.0 microg l(-1) (NE), 0.5-5.0 microg l(-1) (E), 0.6-9.0 microg l(-1) (DA) and 0.6-10.0 microg l(-1) (LD). The limits of detection (defined as a signal-to-noise ratio of 3) are: 0.34 microg l(-1) (NE), 0.15 microg l(-1) (E) and 0.18 microg l(-1) (DA, LD). The HPLC procedure was successfully applied for the determination of catecholamines (NE, E, DA) in human urine after solid-phase extraction (SPE). In a simple run time CAs can be determined in 20 min. The chromatographic linear ranges are: 5.0-72.0 microg l(-1) (NE), 5.0-48.0 microg l(-1) (E) and 5.0-96.0 microg l(-1) (DA). The limits of detection for three urinary CAs are: 0.71 microg l(-1) (NE), 0.26 microg l(-1) (E) and 0.73 microg l(-1) (DA).

Enzymatic chemiluminescent assay of glucose by sequential-injection analysis with soluble enzyme and on-line sample dilution

This work reports a sequential-injection analysis (SIA) method for the enzymatic assay of glucose with soluble glucose oxidase (GOD) and on-line sample dilution with chemiluminescence (CL) detection. A zone of sample was aspirated in the holding coil of the SIA manifold and, if necessary, was diluted on-line by means of an auxiliary dilution conduit. Then, a zone of GOD was aspirated adjacent to the sample zone and a stopped-flow period was applied to allow the enzymatic reaction to proceed with production of hydrogen peroxide. Then, zones of a catalyst (Co(II) solution) and alkaline luminol were aspirated into the holding coil. Finally, the flow was reversed and the stacked zones were sent to a flow-cell located in front of a photomultiplier tube (PMT) that monitored the CL intensity. The linear dynamic range was 1 x 10(-5)-1 x 10(-3) mol L(-1) glucose, the coefficient of variation at 8 x 10(-5) mol L(-1) of glucose was s(r)=3.1% (n=8), the limit of detection at the 3sigma level was c(L)= 1 x 10(-6) mol L(-1) and the sampling frequency was 28 h(-1). With on-line dilution by a factor of 1/200, the linear range could be extended up to 0.2 mol L(-1) glucose. The advantages of the proposed method are the simple manifold and instrumentation used, the scope for automated on-line dilution, the low consumption of sample and reagents and the elimination of enzyme immobilisation procedures. The method was applied to the analysis of commercial drinks and honey with percent relative errors in glucose determination in the range 100+/-6.1%.

Application of sequential injection analysis to pharmaceutical analysis

Sequential injection analysis is a well established tool for automation of pharmaceutical analysis. A short historical background of this technique is given as well as a brief discussion on the basic principles and potentials. The current applications of SIA in the pharmaceutical analysis are also described and discussed. The manifolds developed offer good analytical characteristics and are suitable for analysis of drug formulations, process analysis, drug-dissolution, drug-release testing and functional assays for screening potential drugs. The results obtained are in good agreement with those furnished by the application of the reference methods presented in the pharmacopoeias.

Fermentation monitoring and process control

The use of modern analytical online methods such as two-dimensional fluorescence measurements gives new insights into bioprocesses. With the resulting data, it is not only possible to better understand and document, for example, biotransformations, but also to develop efficient control strategies that lead to better productivity and lower costs.