AUTOMATIC BATCH ANALYSERS

Fig. 1.3 Scheme of the different types of automatic analysers, classified according to the way In which sample transport Is effected. The examples Illustrate the determination of a single analyte In a liquid sample requiring dilution (0) and sequential addition of two reagents (Ri, R2) for the analytical reaction to develop, (a) Batch analyser, (b) Continuous analysers (SFA, segmented-flow FIA, flow-injection CCFA, completely continuous flow), (c) Robot station. Note that agitation is carried out by independent units in (a), is not required in (b) and is effected by a single unit in (c). (Adapted from [17] with permission of Ellis Horwood). 

Fig. 8.1 Ways of incorporating separation techniques into (a) batch and (b) continuous automatic analysers.

It is significant that Technicon, the pioneering and virtually exclusive developers of continuous automatic analysers, have recently devoted their production efforts to batch models. Probably, their RA-1000 model was created to compete with the centrifugal analysers introduced by other firms and which were gradually displacing continuous-flow AutoAnaiyzers, widely used until a decade or so. 

Fig. 8.11 Commoner configurations of batch automatic systems in which the sampling system is an independent module, (a) Automation of the first stage of the analytical process in optical, electroanalyti-cal,thermal or magnetic instruments, (b) Different ways of incorporating samples into specific analysers.

It is the first stage of laboratory analytical methodologies which poses the greatest problems for automation (see Chapter 2). Operations such as weighing, dissolution, grinding and centrifugation are difficult to incorporate on-line in automatic analysers (whether batch or continuous). It is therefore here that robotic systems cover a field inaccessible to the remainder of automatic methodologies. 

QuanOptimize from Micromass also allows automated method development for quantitative LC/MS/MS. It automatically identifies the best method for each compound, then runs batches of samples for quantitative analyses and report results in a QuanLynx browser. Thermo recently launched a similar product for automatic MS tuning. Known as QuickQuan, it generates data and stores it in a central Microsoft Access or Oracle database for future access. The infusion-based valve switching auto-tuning device allows individual compounds to be fully and automatically optimized in about 1 min. 

In addition to the analysis of the thermal stability of the perchloric acid organic reaction media mixtures, a procedure was worked out to determine the fate of the perchloric acid by chlorine analysis of the batch, effluent streams, etc. Preliminary analyses on selected process samples showed no tendency for perchloric acid to concentrate in recycle material and therefore build up in the reactor. A total of less than 1% of the initial charge of perchloric acid (total chlorides calculated as perchloric acid) was found in the combined recovered acid-ester and olefin fractions. Less than 1 % of the initial charge of perchloric acid was found in the finished ester. The analytical method used was an oxygen bomb decomposition, followed by titration of chlorides with 0.0liV silver nitrate, using a recording automatic titrator. The eventual fate of the perchloric acid catalyst was... 

Goodman [28] described an automated procedure for the determination of nitrate in soils. The apparatus automatically extracts and analyses batches of up to 60 soil samples. Analysis is performed electrochemically by means of an ion-selective electrode and reference electrode. Corning ion-selective electrodes were found to be superior to those produced by Orion in this application. Recoveries of nitrate in this method were between 94 and 95%. The calibration curve was linear down to 2.5 mg/1 nitrate. A plan of the general arrangement is shown in Fig. 6.3. 

Common to all analytical procedures (manual, automatic, etc.) is the initial careful measurement of a volume of fluid (in clinical chemistry usually blood, serum, plasma, or urine) as well as volumes of standardizing solutions the accuracy and precision of this single operation are probably the factors that most affect the reliability of the whole procedure for any particular type of analysis. Several different sorts of error may be introduced at this stage the absolute volume of sample measured for each of a batch of replicate analyses may be incorrect the variation from one member of a batch to another in respect of the volume of sample taken may be outside the limits acceptable for the analysis and, when batches of specimens are analyzed, there may be cross-contamination of one specimen with material remaining in the system from the analysis of another specimen. 

Usually it can be defined in the LIMS whether the determined results are checked and compared automatically with the limits, which have been assigned before to a standard. In this case, the system is capable of making a proposal about how the sample or the entire batch could be evaluated. The modem LIMS supports a retrospective evaluation of data. It is possible to present the result of a specific test in a graph together with the results of former analyses. This function can be used for trend analyses — for example, for the rating of suppliers or for the observation of the trend of a specific test parameter. 

In contrast to the two operations described above, the incorporation of the solid sample Into the analyser or Instrument Is comparatively easy to automate. Samplers with cups or vials holding each sample separately are relatively Inexpensive. In batch analysers, samples are treated and transferred separately continuous analysers, which are much commoner, involve Intermediate operations (dissolution, extraction, etc.) and do not have many automatic systems available for incorporation of solid samples. One such system Is the... 

Analytical separation techniques play a major role in the above-mentioned preliminary operations. Their implementation on automatic systems can be achieved in a variety of ways, although most often it is done in one of two ways, namely discontinuously or off-line and continuously or on-line. The former is better suited to continuous analysers (SFA, FIA), and the latter is equally suited to continuous and batch analysers. 

Automatic centrifugal analysers are also batch analysers with final transfer of the reaction mixture prior to measurement. They have become very popular in clinical laboratories in the last few years. The different manufacturers offer a wide a range of models the Centrifichem Models 400 and 600, manufactured by Union Carbide, are probably the best known and most widely used, so they will be described here as the most typical representatives. It should be noted, though, that there are no significant differences between... 

As all 30 samples are, apparently, measured in a simultaneous fashion, the system can be said to effect a parallel multi-determination —hence the generic name parallel fast analyser given by some workers to these instruments, which are even dealt with separately from batch analysers in automatic methods of analysis. However, such a difference is only apparent and, in fact, it is a typically discontinuous process, both because of the sequential measurement (with a single detector) and because there is a manual intermediate operation (the transport of the transfer disc from one module to the other). 

FP-901 analyser proper is a semi-automatic nine-channei photometer with vertical parallel light paths unlike conventional photometers. It has nine light sources and as many photodetectors. Measurements are carried out simultaneously, which makes this a parallel batch system. However, despite its apparent multi-parameter character, it can only determine one parameter in each batch of operations. It allows for Incubation at 30 or 37 C and for mixing within each cuvette. Its functioning is controlled by a microprocessor. 

The different topics dealt with were chosen according to various criteria such as the degree of consolidation, scope of application and most promising trends. The monograph consists of four parts. The first, after dealing with the basic principles behind the automation of laboratory processes (Chapter 1) and the role of computers In this context (Chapter 2), describes automatic systems for sampling (Chapter 3) and sample treatment (Chapter 4). The second part discusses the principles and commonest components of the principal types of analysers, namely continuous (Chapters 5-7), batch (Chapter 8) and robotic (Chapter 9). The third part Is devoted to the automation of analytical Instrumentation spectroscopic (Chapter 10), electroanalytlcal (Chapter 11) and... 

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