Chemistry 7, No. Microcomputers a laboratory

Journal of Automatic Chemistry of Clinical Laboratory Automation, Vol. 7, No. 4 (October-December 1985), pp. 192-196

Microcomputers in a water authoritylaboratory

M. P. Bertenshaw and K. C. WheatstoneSevern-Trent Water Authority, Lower Severn Divisional Laboratory, 141 ChurchStreet, Malvern, Worcestershire WR14 2AN, UK

Introduction

Water authorities in the UK are required not only toprovide a potable water supply ofhighstandard, but alsoto monitor and maintain standards of quality in all otheraspects of their activities. This involves analysis of a verylarge number ofsamples from all parts ofthe hydrologicalcycle, from rivers and domestic supplies to sewagesludges and trade effluents. For example, the Severn-Trent Water Authority, one of 10 in England and Wales,carries out around 2.5 M chemical and bacteriologicaldeterminations per year. Many determinations arerequired under European Economic Community (EEC)legislation, particularly in connection with water supply;however, most information is used in operational investi-gations, works management, assessing charges for treat-ment of trade effluents, or environmental quality control.

Samples for analysis are submitted to water authoritylaboratories from where the results are transmitted tolocal or central computers for immediate examination bydata users; these include operational scientists, water-supply and reclamation operational controllers andpollution-control inspectors. Data archives are main-tained and updated so that they may be subsequentlyexamined for trend analysis and long-term statisticalreporting. In addition, Part 2 of the 1974 Control ofPollution Act (UK) requires that a publically accessibleregister of analytical data must be made available by allwater authorities.

Many water authority laboratories currently use someform of computerized data management system forscheduling and validating analyses prior to reporting andarchiving. Manual (keyboard) entry of results has, untilrecently, been the most common means of mountinginformation onto laboratory computers" this is not onlyextremely tedious for the operator but also contributes amajor source of error to reported data. Although labora-tory instruments used in routine analysis are normallyfitted with a communications facility suitable for connec-tion to a computer or printer, the laboratory computercannot necessarily be configured to receive and collatedata directly from such instruments since data producedusually requires some intermediate processing. Farther-more, dedicated interfacing of several laboratory instru-ments to a central laboratory computer makes inefficientuse of the computer’s time and resources and may evendisrupt its primary data management role. The availabil-ity of inexpensive microcomputers with suitable I/Ointerfaces now makes it economical to dedicate a micro-

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computer to each instrument for data aquisition andprocessing prior to downloading to the central laboratorycomputer. High priority has therefore been given toinvestigating means of automatic data capture and thispaper describes several areas of analysis in whichmicrocomputers have been implemented in the Severn-Trent Water Authority’s Lower Severn Divisional Labor-atory at Malvern (figure 1).

The Malvern Laboratory carries out over 300000determinations per year, of which more than 200 000 areobtained through microprocessor facilities. Althoughmost of the applications below illustrate clear labour-saving advantages which may be easily quantified, it ishoped that the reader will also appreciate the consider-able savings in both time and convenience in improveddata reliability over that experienced with manual dataentry. Furthermore, it should be appreciated that ’in-lab’data processing, through intermediate microcomputers,gives the analyst greater freedom concerning choice ofinstruments and selection of analytical methods.

Lineprinter

/ Master[ terminal

Microwavetransmitter IBMto Seriesmainframe LABoratory

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po.rtableTandyModel 12

computerscomputer

Suspended solids

AAS ’ [Flame AASFurnace AASCalculation packagesFor COD, ionic balance etc.

Figure 1. Data links at Malvern Laboratory.

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replay Lunit ] \

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Continuousflowanalysis

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erminal

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M. P. Bertenshaw and K. C. Wheatstone Micros in a water authority laboratory

Laboratory data management Microcomputer hardware

Malvern Laboratory is one of five laboratories inSevern-Trent Water Authority using LABDAPS (LAB-oratory DAta Processing System). This system has beendeveloped over several years by Severn-Trent dataprocessing staff, in collaboration with laboratory scien-tists. It provides most of the data management require-ments of an analytical laboratory; these include registra-tion of samples, scheduling of analyses, validation ofresults, production of reports, management statistics andfile maintenance procedures. The software cannot beeasily modified by laboratory staff since it is written inPL/I. It does, however, cater for nearly all possibleindividual requirements such as worksheet and reportlayouts, in addition to essential reference file informationsuch as sampling site descriptions, analysis suite detailsand determinand reporting limits.

LABDAPS runs on an IBM Series/1 minicomputerwhich, at Malvern, uses 256 Kbyte core with 29 Mbytehard disk storage configured for three full multi-taskingusers. Peripherals include Newbury 7009 and 8009terminals, a Centronics 6080 lineprinter, an IBM 8 infloppy disk drive and a Penny and Giles 2100 tape replayunit. A modem unit gives access to a microwavetransmitter through which information is sent to adivisional mainframe computer; some information is alsotransmitted to a regional water quality archive. Forautomatic data capture, a rigid format must be adoptedfor each of the three modes of transfer permitted:keyboard, 8 in diskette, or tape replay.

Manual keyboard input of data is performed through asequence of pre-formatted screens in which each result isvalidated against previously derived limits held on a file.Results are entered against laboratory worksheets; theseare documents identified uniquely by number, eachlisting a batch of samples scheduled for a certaindetermination or set of determinations. It is possible tosimulate keyboard entry of characters through theRS232C link intended for a printer on Newbury termi-nals. Serial transmission to a terminal therefore providesthe simplest channel ofcommunication from a laboratorymicrocomputer.

Alternatively, worksheets from the Series/1 computer canbe transferred using the diskette facility by copying onto8 in diskettes in IBM3740 format. This is a disketteexchange standard for transfer of data between differentcomputers and is provided by most major manufacturers.The diskette is copied onto a worksheet file on themicrocomputer into which results are captured. The fileis then output to diskette in IBM 3740 format to be readby the Series/1 computer. Owing to this additionalfile-transfer step between computers, known as ’reformat-ting’, diskette transfer is reserved for large batches ofdata(typically 200-600 data items).

The tape replay facility is specifically intended for usewith raw data from continuous flow analysis (CFA)systems and runs in conjunction with bespoke software onthe Series/1. Through this facility, the Series/1 canprocess up to 10 channels of CFA data simultaneously.

Tandy Model 100 portable computers are used in severalapplications described below (see also figure 1). Thesemains/battery-operated microcomputers incorporate a40 x 8 character liquid-crystal screen, an RS232C portfor I/O, a parallel printer port and a cassette recordersocket. A 32K read only memory (ROM) supportsMicrosoft BASIC, text editing, communications andfile-handling facilities. Random access memory (RAM)can be expanded from 8K to 32K and is protected byinternal batteries.’

Tandy Model 12 computers are used in applicationswhere large amounts of data are to be manipulated.These incorporate an 80 x 24 character screen, two

RS232C ports, a parallel printer port, dual 8 in floppydisk drives and a 64K RAM. All programs are written inMicrosoft BASIC, with additional Z80 machine-codeI/O routines.

Processed raw data are handled by the microcomputersin two ways: sequentially or by direct access. The TandyModel 100 portable computer supports only sequentialfile access in its solid-state memory. This type of file issuitable for uploading serial data to the laboratorycomputer by RS232C link. However, changes to a

sequential file, such as a result amendment or deletion,are complex because the entire file must be searched insequence for the data item to be edited, then a new filecreated. (In practice, the original file is renamed beforeopening for input so that output is made to the originalfilename.) Also, serial transmission times can becomeunacceptably long since the Series/1 validates resultsduring data entry.

For large data files, it is more convenient to use direct fileaccess and diskette data transfer. This necessitates theuse of more sophisticated hardware, for example, atMalvern Laboratory, the Model 12 computer. Editingroutines are much faster using this type of data storageand more efficient data transfer can be made to thelaboratory computer using the 8 in diskette facilitydescribed above.

Sample registration

The registration ofa single sample onto a laboratory datamanagement system is by no means straightforward sincethis interacts with nearly all files on the computer.Consequently, simultaneous receipt of many samplesfrom a variety of sources can become one of the most

complex and time-consuming tasks in laboratory dataprocessing. In order to achieve smooth and efficientregistration of samples, analytical requirements .andsample details should be recorded as quickly andaccurately as possible. LABDAPS provide a facility forpre-booking known sample runs; this facility is usedwhenever possible and can show considerable benefits.However, most samples are received without priorknowledge or are taken on such an irregular or unpredict-able basis that it is inappropriate to record them in thesample runs file. Therefore the majority of samples haveto be registered individually.

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A Longines Data 3000 optical mark reader (OMR),which accepts sample input documents specially desig-ned for the purpose, is now being evaluated at theMalvern Laboratory. Sampling officers fill in these formsin the field by marking prescribed boxes in pencil. At thelaboratory, the forms are fed through the OMR in whichinformation is coded and transmitted to a Model 12microcomputer for further processing. After automatic-ally validating the information, the microcomputer regis-ters samples onto LABDAPS by serial transmission ofdata through a sequence of pre-formatted screens, whichare normally used for manual registration from akeyboard. Since information is passed from input docu-ments to the laboratory computer with no input from thecomputer operator, details given on the forms by ourcustomers are accurately recorded.

Atomic absorption spectrophotometry

Most modern atomic absorption spectrophotometers(AAS) are fitted with internal, dedicated microprocess-ors. A microcomputer may be connected to the instru-ment for data collection and processing, normally usingan RS232C link. AAS instruments interfaced to micro-computers at Malvern include Instrumentation Labora-tory 157 and 457 models and a Varian 875. Output takesthe same format as would be found on a printer;characters sent down the RS232C port include messagessuch as ’MEAN’ or ’RSD’, line-feeds, sample numbersand numeric results. The instruments are always con-figured to output the mean of two or more readings oneach sample, blank or standard; therefore, all themicrocomputer has to do is to recognize the mean resultand store it.

When used in conjunction with an autosampler, theseinstruments will usually provide an option to periodicallyzero the absorbance readings on blanks and reslope onstandards. However, where there is appreciable base-lineor sensitivity drift between standards, significant errorscan result, particularly in samples immediately prior torecalibration (see figure 2[a]). A more accurate approachis to read blanks and standards as if they were samplesthen retrospectively apply base-line and sensitivity cor-rection to sample data by time-based interpolationbetween blanks and standards (see figure 2[b]). No use ismade of the instrument microprocessor’s ability toauto-zero or reslope during the run since these functionsare performed externally; however, curve correction isapplied by the instrument during initial calibration, sincethere is no advantage in performing this externally. Finalresults are not calculated until the end ofa run ofsamples,but this does not result in any inconvenience since theanalyst is rarely in attendance during long automatedsample runs.

Suspended solids

This is a measurement ofweight differences in dried filterpapers before and after filtration of known volumes ofsamples. Raw data required comprise initial weight offilter (W1 g), volume ofsample taken for filtration (Vml)and final weight offilter with solids (W2 g); calculation ofsuspended solids is given by 106 X (W2-W1)/V mg/1.

TIME

(b)

C

B

TIME

Figure 2. Flame AAS traces indicating assignment of base-line(B) and calibration C) by an instrument microprocessor (figure2[a]) and an external microcomputer (figure 2[6]).

The procedure adopted before the introduction of a

microcomputer involved hand-written records of all rawdata, followed by keyboard entry onto the laboratorycomputer for calculation of results. Occurrence of tran-scription errors was not uncommon, perhaps not surpris-ingly since five-place decimal weighings are recorded.Having purchased an electronic balance with RS232output it required only a simple program on a TandyModel 100 to record weighings and download calculatedresults to the laboratory computer.

The balance, a Mettler AE163, is operated by afootswitch which, when pressed, triggers an output to thecomputer, but only when the balance registers a stablereading. Integration time and stability level may beselected on the balance. The computer can beprogrammed to only accept readings within a certainrange in order to avoid recording zero weights if thefootswitch is operated accidentally between filter weigh-ings. A fast routine for manually entering sample volumesis provided in which a default volume of 200 ml is used sothatonly volumes other than this value need to be enteredby the analyst. Raw data may be displayed, edited orprinted before serial transmission of final results to thelaboratory computer. More than 15 000 suspended solidsresults per year are determined in this way. Additionally,

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total dissolved solids are processed using the sameprogram.

Biochemical oxygen demandMeasurement of dissolved oxygen (DO) in a samplebefore and after a five-day incubation period at 20 C isthe standard method for estimating biochemical oxygendemand (BOD). Raw data required for the test compriseinitial DO (D1), sample dilution factor (d) and final DO(D2); calculation of mg/1 BOD is given by d (D2-D 1)

(d-l) B/d, where B is the measured BOD of thedilution water. It can be seen that DO readings anddilutions used in this calculation are analogous to weightsand volumes used in the suspended solids calculationabove. It therefore took little effort to adapt the suspen-ded solids software for BOD determinations, with addi-tional programming to allow for blank subtraction.

DO readings are taken from a Corning 155 digitalpH/mV meter incorporating an RS232 output. Two EILdissolved oxygen probes are alternately connectedthrough a ’Y’ switch so that one can be read whilst theother is equilibrating with fresh sample. Output isinitiated at the meter which awaits a stable reading beforetransmission to the microprocessor. An audible signal isproduced on signal transmission which leaves the analystfree to make up sample dilutions during stabilizingperiods. Alternatively, an alarm sounds if the initial DOreading is too low so that the sample may be furtherdiluted prior to incubation.

Owing to the length oftime taken to complete BOD tests,i.e. five days, and the possibility of accidentally losingdata from the RAM files of the microcomputer, tapesecurities of raw data files are kept until the final resultsare downloaded to the laboratory computer. As withsuspended solids, determined raw data can be validatedand printed before final results are transmitted to thelaboratory computer. Approximately 10 000 BOD deter-minations per annum are carried out at Malvern.

incrementsup to 100 min, but typically 2. to 5s intervalsare appropriate for most CFA systems in order thatsufficient readings are taken for peak definition.

Once the Squirrel-logged data have been transmitted to amicrocomputer, a peak-picking routine is applied forwhich the computer requires the following information_:

(1) Expected number of peaks.(2) Approximate time per peak.(3) Recording interval.(4) Threshold value for first peak.(5) Minimum value for assignment of peak maximum.

The last item is required so that small peaks are omittedfrom the peak maxima assignment routine. Conse-quently, long intervals in which there are no significantpeaks place great reliance on the timing accuracy of theautosampler and the measured time per peak. Inpractice, a standard should be inserted at least every !0samples to eliminate this problem and, at the same time,provide more reliable calibration.

Management information

Timely management information is essential for theefficient and effective management of a laboratory. Keyareas for which information must be collected are:

(1) Levels of service: this will include ’quality’ character-istics such as time between receipt of sample andreporting of results, and analytical quality control(AQC) statistics.

(2) Work-load: this is quantitative information such asnumbers of samples, determinations, standards etc.,usually collected over several time periods, forexample daily, weekly or monthly.

(3) Efficiency: this can be measured on several criteria,usually combining quantitative information with oneor more ofmanpower, time, total laboratory cost etc.to produce unit cost figures.

Continuous flow analysis

Many routine tests carried out at Malvern are performedusing the technique of continuous flow analysis (CFA).Although there is a current trend in water authoritylaboratories towards automated discrete analysis, theMalvern Laboratory has such a large investment in CFAapparatus that its replacement cannot yet be justified oneither cost or efficiency grounds. Raw data obtained onTechnicon AAII CFA equipment for routine tests such asammonia, TON, chloride, etc., are processed through theSeries/1 computer via a tape logger and repiay unit (see.figure 1).

The Series/1 computer automatically collects data andproduces reports on (1) and (2) above, but manipulationofdata to produce information on efficiency and unit costsis better achieved using a microcomputer. Bulk data aretransferred from the Series/1 to a Tandy Model 12microcomputer via 8 in diskettes and the appropriateadditional information (manpower figures, hoursworked, total costs etc.) added both manually and fromdata stored on a Model 100 microcomputer. Thecombined data are processed on the Model 12 in order toproduce management information summary reports asrequired.

Certain other tests are run less frequently; these are moreconveniently handled through an independent channel ofprocessing. This alternative system uses a Model 12microcomputer in conjunction with a solid-state,analogue-to-digital, data-logging device, the GrantSquirrel. The Squirrel stores up to 4000 readings on eachoftwo channels, although single- or four-channel versionsare also available. Recording intervals are selectable in ls

Other applications

Microcomputers can often assist the analyst in a numberof less obvious ways. For instance, there are alwaysrepetitive calculations to be performed which are moreconveniently run on a microprocessor rather than acalculator. At Malvern, these include determinations ofionic balance, dry solids, organic matter, metals equi-

195


valents and chemical oxygen demand. Furthermore, theability to use laboratory computers as word processorswhen not engaged in analytical work can be of enormousbenefit. Any laboratory method can now be recalled fromfloppy disk so that alterations to text can be made and arevised version obtained immediately.

There is currently considerable interest in the use ofmicroprocessor-controlled robot arms for sample prep-aration in laboratories. However, the inhomogeneousnature of many samples of interest to the water industryat present precludes the use of robots in areas of samplepreparation where representative subsamples arerequired. For example, there is not yet available a robotarm capable of lifting and shaking a litre bottle of liquidcontaining suspended material and removing an appro-priate volume subsample for the BOD test. It is likely thatfuture advances in technology will overcome thesedifficulties, otherwise the quest for increased automationand efficiency may bring about changes in emphasisplaced on such tests.

Conclusions

This paper shows some applications of microcomputersin a water authority laboratory; these have demonstratedthe following benefits:

(1) Increased reliability of data.(2) Time savings.(3) Increased efficiency.(4) Enhanced flexibility.(5) Improved management information.

However, the introduction of such rapidly developingtechnology in the laboratory must be done with flexibilityand compatibility in mind, whilst maximizing the use ofexisting laboratory instruments.

Acknowledgement

We wish to thank Mr V. W. Howells, Divisional Scientist,Lower Severn Division, S.T.W.A., for his helpful com-.ments.on the manuscript.

NOTES FOR AUTHORSJournal ofAutomatic Chemistry incorporating Journal ofClinical Laboratory Automation covers all aspects ofautomation and mechanization in analytical, clin-ical and industrial environments. The Journal pub-lishes original research papers; short communica-tions on innovations, techniques and instrumenta-tion, or current research in progress; reports onrecent commercial developments; and meetingreports, book reviews and information on forthcom-ing events. All research papers are refereed.

ManuscriptsTwo copies of articles should be submitted. Allarticles should be typed in double spacing withample margins, on one side of the paper only. Thefollowing items should be sent: (1) a title-pageincluding a brief and informative title, avoiding theword ’new’ and its synonyms; a full list of authorswith their affiliations and full addresses; (2) anabstract of about 250 words; (3) the main text; (4)appendices (if any); (5) references; (6) tables, eachtable on a separate sheet and accompanied by acaption; (7) illustrations (diagrams, drawings andphotographs) numbered in a single sequence fromupwards and with the author’s name on the back ofevery illustration; captions to illustrations shouldbe typed on a separate sheet. Papers are acceptedfor publication on condition that they have beensubmitted only to this Journal.

ReferencesReferences should be indicated in the text bynumbers following the author’s name, i.e. Skeggs[6]. In the reference section they should bearranged thus:

to a journalMANK$, D. P., Journal of Automatic Chemistry, 3(1981), 119.to a book

MALMSWADW, H. V., in Topics in Automatic Chemistry,Ed. Stockwell, P. B. and Foreman,J. K. (Horwood,Chichester, 1978), p. 68.

IllustrationsOriginal copies ofdiagrams and drawings should besupplied, and should be drawn to be suitable forreduction to the page or column width oftheJournal,i.e. to 85 mm or 179 mm, with special attention to

lettering size. Photographs may be sent as glossyprints or as negatives.

Proofs and offprintsThe principal or corresponding author will be sentproofs for checking and will receive 50 offprints freeof charge. Additional offprints may be ordered on aform which accompanies the proofs.Manuscripts should be sent to either Dr P. B. Stockwell orMs M. R. Stewart, see inside front cover.

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