Thursday, 13 April 2017




5.1 Introduction
5.2 Apparatus
5.3 Reagents
5.4 Samples

5.1 Introduction

Quality analytical work can only be performed if all materials used are suitable for the job, properly organized and well cared for. This means that the tools are adequate and in good condition, and that sample material receives attention with respect to proper handling, storing and disposal.
The tools used for analysis may be subdivided into four categories:
1 Primary measuring equipment (pipettes, diluters, burettes, balances, thermometers, flow meters, etc.)2. Analytical apparatus or instruments.
3. Miscellaneous equipment and materials (ovens, furnaces, fridges, stills, glassware, etc.)
4. Reagents.
The saying that a chain is as strong as its weakest link applies particularly to these items. An analyst may have gone out of his/her way (as he/she should) to prepare extracts, if the cuvette of the spectrophotometer is dirty, or if the wavelength dial does not indicate the correct wavelength, the measurements are in jeopardy. Both the blank and the control sample (and a possible "blind" sample or spike) most likely will reveal that something is wrong, but the harm is already done: the problem has to be found and resolved, and the batch might have to be repeated. This is a costly affair and has to be minimized (it is an illusion to think that it can be totally prevented) by proper handling and maintenance of the equipment.
Also the quality and condition of a number of other working materials have to be watched closely. The calibration of thermometers, burettes and pipettes, particularly the adjustable types, may exceed the acceptable tolerance (and be put out of use). New glassware may look clean but always needs to be washed. Glassware may give off unwanted elements (boron, silicon, sodium). The same goes for milling and grinding equipment (pestles and mortars, tungsten carbide grinders, brass or steel sieves). For virtually all analyses glassware needs to be rinsed with deionized water after washing. Therefore, if glassware, such as volumetric flasks, is shared by analysts, they should be able to rely on the loyalty and good laboratory practice of their colleagues.
A similar reasoning applies to reagents. One of the most prominent sources of the errors made in a laboratory is the use of wrongly prepared or old reagents. Therefore, reagents have to be prepared very carefully and exactly following the prescriptions, they have to be well labelled and expiry dates have to be observed closely. Filtering a pH buffer solution in which fungi are flourishing may save time and reagent but is penny-wise and pound-foolish.
Of equal importance for the quality of the work is the proper handling of the sample material. Not only the technical aspects such as sample preparation, but particularly the safeguarding of identity and integrity of the samples as well as the final storage or disposal (chain of custody).
As part of the overall quality assurance, in this chapter a number of instructions and suggestions are presented to ensure the analytical reliability of the main tools and proper organization of sample handling.

5.2 Apparatus

5.2.1 Registration
5.2.2 Operation

For quality assurance, with respect to instruments and other equipment the following requirements should be met:
1. Apparatus used for generation of data, and for controlling environmental factors relevant to the study should be suitably located and of appropriate design and adequate capacity.2. The apparatus used should be periodically inspected, cleaned, maintained, and calibrated according to Standard Operating Procedures. Records of procedures should be maintained.
In practice, therefore, a number of record forms and instructions need to be prepared.

5.2.1 Registration Instrument Identification List Instrument Maintenance List. Instrument Calibration List Instrument Identification List

For proper management a complete list of all available apparatus is indispensable. This Instrument Identification List should contain all information relevant for ensuring reliable and continuous functioning of the apparatus. A model page for such an instrument list is given as Model APP 003.
Such a record should, in addition to the description and registration/identification number, contain information about the supplier (to contact in case of inspection, repair or replacement), the date the apparatus was installed, and the person to whom the responsibility for the instrument was assigned. This list can be compiled by any laboratory staff member on behalf of the head of laboratory. A copy can be issued to all laboratory staff (as well as the Quality Assurance Officer if applicable) or the list is deposited in a central place accessible to all staff. The latter option allows a card-box system (physical and/or on computer) where cards can easily be inserted and removed. When new apparatus is acquired the list must be revised (or a new list or page may be issued) including the deletion of old apparatus when replaced. Instrument Maintenance List. Instrument Calibration List

For apparatus that needs maintenance and calibration at regular intervals an Instrument Maintenance List and an Instrument Calibration List (or card-box system) must be prepared. These lists, which may be combined, include columns for instrument identification, reference to the logbook concerned and fixed dates or intervals for actions. They are an aide-mémoire for the laboratory management, the actions themselves being recorded in the logbooks. A model for these lists is given (Model APP 004).

5.2.2 Operation Operation Instruction Manual
5.2 2.2 Instrument Maintenance Logbook
5.2 2.3 User Logbook SOPs for use of equipment Operation Instruction Manual

For all apparatus an Operation Instruction Manual should be available. Usually this is the instruction manual issued by the supplier. Should this instruction not be satisfactory, incomplete, or in a language in which the user is not proficient, then a proper instruction manual should be made. Most commonly, the technician using an instrument writes this as a SOP. Examples are given at the end of this chapter (see Often, laboratories have the instruction manual and maintenance logbook (see next) combined into one volume.

5.2 2.2 Instrument Maintenance Logbook

In addition to the instruction manual, for each apparatus a Maintenance Logbook should be prepared. All relevant actions taken with respect to the apparatus should be recorded in this logbook, e.g., problems encountered and repairs made, periodic inspections, and calibrations (other than normal calibrations with standard curves as part of an analysis). A model for the pages of such a logbook is given as Model APP 041.
When initiating these logbooks for apparatus that have been in use for some time, the present condition of the apparatus is the starting point and must be assessed and recorded in the logbook together with any other information which happens to be known and which might be relevant for future functioning (age, past problems, defects, repairs, etc.). This is preferably compiled by the technician-in-charge of each instrument concerned. If this venture is taken up from scratch it is advisable to start with analytical instruments that generate data, and subsequently deal with the auxiliary equipment.
Maintenance should always be carried out by qualified technicians either from inside or outside the institute. Many laboratories have maintenance contracts with suppliers. Such contracts are generally quite expensive and should be critically reviewed regularly on usefulness and length of intervals. Depending on the intensity and skill with which equipment is used maintenance intervals can often be extended (unless accreditation bodies require strict adherence to maintenance schedules). For other equipment regular maintenance may be changed into if-and-when-you-need maintenance, particularly those which are checked or calibrated before each use (which may reveal a gradual decline in response, e.g. AAS) and those for which back-up instruments are available (e.g. electronic balances). Often, however, such policies are only theory because for some reason qualified service may not readily be available, for instance when the supplier has no local office in the country. This makes the in-house maintenance facilities even more important. A sensible measure is to build up a stock of essential parts (e.g. hollow cathode lamps for AAS), necessary tools, blueprints and, if possible, back-up equipment. Keep records of all these items. Also, arrangements with other laboratories for mutual assistance can be useful.
Note. An example of an organization with this aim is SPALNA, the Soil and Plant Analytical Laboratory Network of Africa. Secretariat at: IITA. Oyo Rd.. PMB 5320. Ibadan. Nigeria.

5.2 2.3 User Logbook

Finally, for all apparatus sensitive to use and particularly to misuse, such as flame photometers. AAS. ICPs, chromatographs, autoanalyzers. X-ray equipment, spectro-photometers etc.. a User Logbook should be prepared in which users identify themselves and report particulars of the use: date, duration, elements measured, matrix in which was measured, and whether any problems were encountered (if there were serious problems, these should then be recorded in the Maintenance Logbook as well and reported to the head of laboratory). A suggestion for a page of this logbook is given as Model APP 051.
To facilitate easy and rapid information for the user (and the HoL or QA officer) in some laboratories the status of maintenance and calibration is given on a label on the instruments. SOPs for use of equipment

As indicated above, a SOP should be made for the use of each apparatus. Although much freedom exists as to the format of such SOPs, a minimum of essential information should be included. As a guide, a few examples are given at the end of this chapter. These comprise:
1. A standard instruction for writing these SOPs (Model F 011),2. Two SOPs for primary measuring equipment: an adjustable pipette and an electronic balance (Models APP 061, and APP 062).
3. A SOP for a common analytical instrument: a pH meter (Model APP 071).
One of the most important aspects of the SOPs for this equipment is the calibration and adjustment (standardization). A number of tools belonging to the category of primary measuring equipment cannot be adjusted e.g., volumetric flasks, standard glass burettes, volumetric pipettes. This type of equipment is not normally calibrated unless there is reason to suspect inaccuracy or when it is to be used for very accurate analytical work. Sometimes different qualities are available e.g., volumetric flasks Class A and Class B (tolerance ±0.1% and ±0.2% respectively).
Note: When calibrating volumetric glassware the weight of the displaced air may not be neglected: this amounts to a correction of 0.11% (i.e. filling up a volumetric flask with 100.00 ml water of 25°C should result in a weight increase of 99.89 g).

5.3 Reagents

5.3.1 Reagent chemicals
5.3.2 Standard and Reagent solutions

5.3.1 Reagent chemicals

It is advisable to use analytical grade chemicals in the laboratory throughout. Nevertheless, in soil analysis, analytical grade is often not really necessary and is the chemically pure grade satisfactory. It is then a matter of balancing the saving of money against disadvantages such as needing more space (some chemicals will be in stock in two grades), more book-keeping and risk of making mistakes. The minimum requisite purity of chemicals (including that of water and other solvents) should be stated in the description of the analytical procedure (see Chapter 7).
When chemicals (and gases) arrive in the laboratory' the containers need to be labelled. On the label should be recorded the date it was received, when it was first opened and, in some cases, the expiry date. Such labels can conveniently be home-made with the PC. A suggestion for a model is given in Figure 5-1.
Fig. 5-1 - Label for reagent chemical containers
When taking chemicals form a bottle there are three basic rules to obey:
1. Use a clean spoon or spatula (do not use one which happens to lie around, unless it is cleaned).2. Do not return chemical to the bottle.
3. Close the bottle tightly after use.

5.3.2 Standard and Reagent solutions

There are basically two types of standards needed for chemical analysis:
1. Standard reagents for standard reagent solutions, e.g., the popular standard reagent ampoules, or pure chemicals. These are needed for first-line control (calibration of measuring instruments).2. Standard sample material, to be divided in primary (certified) standard material and the "home-made" control samples. These are needed for second-line and third-line control.
The present discussion is restricted to Type 1, the standard reagents. The standard sample material is discussed in Chapters 7. 8, and 9.
In addition to standard solutions for calibration, reagent solutions need to be prepared for extractions and analytical reactions.
Much of the success of an analysis depends on the reliability of the used standard and other reagent solutions. These should be prepared with great care and only by experienced personnel. In larger routine laboratories extracting solutions are often made by one person or a unit and centrally stored. Each preparation of a solution should be recorded in a Reagents Book (or separate Standards Book). A model for a page of such a book is given. When an ampoule is used rather than a reagent chemical, this can be entered in the column "Amount weighed in". (If titrations are used to determine titres, details of this can be recorded on Worksheets belonging to the analytical procedure involved).
The lay-out of a reagent book may be one of two kinds:
1. All reagents prepared are recorded chronologically.
2. For each reagent a page (or set of pages) is reserved.
In the latter case the first row of the form (RF 032) may be preprinted or prefilled-in for convenience.
When a standard or any other reagent solution is prepared the bottle in which it is stored should be properly labelled. A suggestion for the model of such a label is given in Figure 5-2.
Fig. 5-2. Label for reagent solutions.
For bottles containing standard solutions for calibration of instruments labels of slightly different model can be used as shown in Figure 5-3. In the upper empty section the what the shelf-life of a reagent solution is marker in large characters for easy recognition which is convenient during the calibration procedure, e.g. "Ca 10" for AAS. For handling reagent solutions similar rules apply as for reagent chemicals: do not return unused solution to the bottle (contamination!) and close the analyte and concentration can be written with a field marker in large characters for easy recognition which is convenient during the calibration procedure, e.g., "Ca 10" for AAS. For handling reagent solutions similar rules apply as for reagent chemicals: do not return unused solution to the bottle (contamination!) and close the bottles immediately and tightly after use to prevent evaporation and contamination. Even so, reagent solutions should generally not be kept for longer than six months after preparation (while some may only be used for few days, and some should be prepared freshly each time they are used!). In some cases, expiry dates are provided by the supplier, but in most cases only experience can teach what the shelf-life of a reagent solution is. Sometimes, reagent solutions can be re-standardized to extend the shelf-life (place new or additional label or sticker!). To avoid mistakes, coloured labels (or coloured dots) may be used. For example, red labels could be used for reagents with a short life (e.g. buffer solutions), blue labels for reagents that should be stored in the refrigerator, and yellow for reagents that are to be kept in the dark.
Fig. 5-3. Label for standard solutions.
The preparation of each (standard) reagent solution including information about labelling, storing and disposal, should be written up as a SOP.

5.4 Samples

Test samples of soil, plant and water vary widely in nature and condition. The sampling itself will not be discussed here as the responsibility for this usually lies outside the laboratory.
Note. This does not mean that the sampling procedure has no influence on the analytical results. Several factors such as moisture content, packing, time lapse between sampling and analysis, etc. may be of influence. In addition, the technique and pattern of sampling (grid density) can have a strong bearing on the interpretation of the results.
The laboratory should demand proper packaging, labelling and administration of samples before they reach the laboratory. Specific information as to the character of the sample may be very useful for further processing. In fact, SOPs, protocols, registration forms and labels (made of plastic, not of paper) can be prepared and issued to clients or project managers prior to sampling or delivery to the laboratory. This greatly facilitates the administration and processing in the laboratory and reduces the risk of mistakes and confusion. There is probably no laboratory which has never experienced a problem in this field.
Good Laboratory Practice aims at proper administration and a continuous scrutiny of the identity of samples and an unbroken chain of custody. Every effort should be made to prevent samples being accidentally interchanged, being contaminated (broken bags), losing their identity (i.e. their label or number) or getting lost. A system can never be full-proof and there may always be circumstances beyond one's control (e.g. fire), and particularly possible malevolence and sabotage are virtually impossible to prevent.
Chain of custody
From the moment samples arrive at the laboratory (or institute) their identity, integrity (spilling and contamination!), and knowledge of their whereabouts must be safeguarded. This implies the following actions:
1 Inspection of packaging, condition of samples, (dry, moist), identification (labels still readable?).2. Registration by an authorized person who takes care of further routing the samples according to a protocol.
This will usually imply handing over the samples to someone charged with the preparation (drying, sieving etc.) and transfer to the laboratory. Each institute needs a protocol describing the formal procedure for handling samples. An example of a simple draft version is given as Model PROT 011.
The registration procedure includes entering particulars of the samples into a Sample Logbook with forms of a design fitted for the purpose. An example is given here as Model RF 011. The sample numbers can be entered into the logbook or, perhaps more conveniently, attached to the registration form when a proper sample list is accompanying the samples. A copy of this list is kept in the (physical) file which is made for each work order. The registration procedure also includes assigning a programme of analyses and defining a target date of completion. An example of a form for this purpose is given as Model RF 021.
It is emphasized that a computerized laboratory information and management system (LIMS) is a powerful tool in the organization and quality control of the laboratory (see Chapter 8). In the chain of custody a LIMS is useful as it facilitates the registration of samples and analytical programme and produces ready-to-use printed sticker-labels with all relevant information for the sample containers.
Finally, the ways samples are stored and disposed of also have to be described in protocols. As mentioned in Section 4.2.3, sometimes contaminated samples may have to be treated as chemical waste.


APP 003 - Instrument Identification List
APP 004 - Instrument Maintenance/Calibration List
APP 041 - Logbook of AAS
APP 051 - User Logbook of AAS
F 011 - Standard Instructions for drafting apparatus SOPs
APP 061 - Operation of Eppendorf Varipette 4810
APP 062 - Operations of electronic balance Sartorius
APP 071 - Operation of pH meter Metrohm E 632
RF 032 - Page of Reagents Book
PROT 011 - Protocol for custody chain of samples
RF 011 - Protocol for accepting delivery of samples
RF 021 - Form for accepting order for analysis

APP 003 - Instrument Identification List

Page: 1 # ...

Model: APP 003Version: 2Date: 96-05-15File:

Title: Instrument Identification List
Instr. no.
Serial no.
Install. date
Person-in-charge (deputy)
Logbook no.

APP 004 - Instrument Maintenance/Calibration List

Page: 1 # ...

Model: APP 004Version: 2Date: 96-05-15File:

Title: Instrument Maintenance/Calibration List
Instr. no.
Serial no.
Maintenance / Calibration schedule
Logbook no.

APP 041 - Logbook of AAS

Page: 1 # ...

Model: APP 041Version: 2Date: 97-03-17

Title: Maintenance Logbook of AAS Perkin Elmer AAnalyst 100
Serial no.:_____________Location: _____________
Inspection / Problem / Action taken / Remarks
Sign. HoL

APP 051 - User Logbook of AAS

Page: 1 # ...

Model: APP 051Version: 2Date: 97-02-26

Title: User Logbook of AAS Perkin-Elmer AAnalyst 100
Serial no.:_____________Location: _____________
Name user
Problems Y/N
Other Particulars

F 011 - Standard Instructions for drafting apparatus SOPs

Page: 1 # ...

Model: F 011Version: 2Date: 95-12-11

Title: Standard instructions for drafting apparatus SOPs
QA Officer (sign.):Date of expiry:
The first page is composed according to Standard Instruction F 001 (General Instructions)
Give title of SOP, e.g. "Operation of Philips/Pye Unicam SP3-200 Infrared Spectrophotometer".
State briefly the purpose of the apparatus. If applicable, mention the analytes and matrices that can be used. If apparatus is part of larger system specify this.
Describe briefly the principle of the technique used.
Give all data relevant for the identification, location, etc., as well as for its proper use: conditions under which the apparatus can be used, relevant specifications and/or limitations.
3.1 General information
Give the following general data. This can also be given in an Appendix. Alternatively, make reference to the corresponding Maintenance Logbook where all this information must be given also:
- name and description of apparatus; type and serial numbers; own identification number
- name manufacturer and/or supplier
- dates of receipt and implementation
- location of apparatus
- name of person responsible for apparatus
3.2 Functional information
Specify working ranges, limitations and other information relevant for the application of the apparatus, e.g.:
- working range(s) for applicable analytes (usually given by manufacturer)
- lower limit(s) of detection
- sensitivity
- signal/noise ratio
- temperature range
- other limitations (e.g. matrix concentrations)
Give definitions of used terms-
Where necessary refer to other relevant SOPs e.g.:
- F 011 Standard instruction for drafting apparatus SOPs
Describe the precautions to take for safe operation, e.g. checking of gas and pressure valves; use of fume exhaust; fire or explosion danger; wearing gloves or safety goggles; use of pipette balloon; etc. etc.
A number of relevant documents accompany the apparatus facilitating control and optimal use with minimum trouble or failure.
7.1 Logbook(s)
For each apparatus a logbook should be made. All relevant events concerning the use and maintenance of the apparatus should be recorded in this book. It may be divided in two parts or consists of two volumes: Instrument Maintenance Logbook and User Logbook. The logbook(s) should have the following features:
- Front page with title, SOP number, serial number, and date of issue,
- Second page with general information mentioned under 3.1.
7.1.1 For maintenance:
(instructions for maintenance are given under 8 below)
- In case of trouble:
date of mishap
description of problem
date of restoring to service
- In case of maintenance:

date of latest and next service (maintenance status)
kind of maintenance
what parts were used and have to be ordered
particulars for next service particulars of calibration (instructions for calibration are given under 10)
7.1.2 For user registration:
- date of use
- name of user
- particulars of determination (analyte, matrix)
- duration of use
- relevant observations (problems, note for next user)
7.2 Manufacturer or supplier documents
These are the original manuals delivered with the apparatus. Often, photocopies are kept with the apparatus (particularly smaller manuals may get lost). If the original is not kept with the apparatus, make clear where to be found: with sticker, on photocopy, in logbook(s), centrally in manual file, or otherwise.
7.3 Internal documents
In the laboratory there should be a list of persons who are authorized to
- use the apparatus
- perform the maintenance
- perform the calibration
8.1 General
Give here all actions necessary to prepare the apparatus for use. Include instructions for proper environment such as:
- correct gases, lamps, cooling system
- climate control in working room
- safety measures and pollution control
8.2 Operation instruction
Divide this paragraph in as many numbered parts as there are separate steps to be performed. Describe these steps accurately and in chronological order, using the imperative.
When the operation instruction is extensive or already exists as a separate document, it need not be integrated with the apparatus SOP. Its existence as an annex to the SOP is then mentioned in Section 3.
8.3 Malfunctioning, Interferences
Describe all interferences and malfunctioning that are known to possibly occur and disturb the proper functioning of the apparatus. Give information about
- kind of problem
- appearance or how it can be recognized
- how it can be solved
- who to turn to for assistance to solve the problem
9.1 Definition/description
If applicable, state the maximum period between services or give service scheme of kind and frequency of service. As an appendix, there must be a list of essential spare parts that should be in stock. The final part of each service should be a test of the relevant specifications of the apparatus.
9.2 Maintenance by own personnel
Describe the technical operations that need to be performed for maintenance of the apparatus. If necessary, distinguish between different kinds of service. Use a stepwise description of the operation (as for the operation instruction 6.2). Record particulars in the Maintenance Logbook.
9.3 Maintenance by third party
Give information about
- name, address and telephone number of company (or individual) involved
- name of contact person
- specifications of warranty and of the contract (e.g., frequency) for service
The serviceman roust report his findings in writing; these reports must be filed (e.g. stick in Maintenance Logbook or in special Maintenance Report File cross-referenced with a remark in the Maintenance Logbook).
10.1 Definition
CalibrationDetermining the value of the deviation(s) of an instrument from an applicable standard.
AdjustmentOperation to make instrument sufficiently accurate for the measurement (this operation is also called standardization)
Give here all operations or manipulations necessary to calibrate the described apparatus. In certain cases this may involve adjustment. Use a stepwise description of the operation. The operation for adjustment should (also) be described in the Operation Instruction (8.2).
Note: This calibration is to be distinguished from the calibration of an instrument for each measurement. This is usually done batchwise using standard series specified in the various analytical methods.
Relevant calibration items are;
- Pre-set values and tolerated deviations)
- Frequency of calibration
- what calibration standards are used
- relation to national or international standards
- environmental conditions during calibration
- measures to minimize shifts in adjustment
10.2 Calibration by own personnel
Record in logbook:
- calibration status of instrument
- calibration result
10.3 Calibration by third party
Give information about contract for calibration:
- Name, address and phone number of company
- Name contact person
- Contract number
- Frequency of service
Note: Calibration of modern instruments by third party becomes less and less necessary. Usually it is included in maintenance contracts.
When an instrument is not functioning properly or defect it may no longer be used. Describe if there are other reasons for putting the instrument out of action, e.g. when calibration or maintenance dates have expired. (In non-accredited laboratories the latter two rules are often not observed. Quality may then be in jeopardy.) State how the instrument is to be labelled if it is not to be used,
Record in logbook:
- Date of putting out of action
- Reason
- Suggestions for solving the problem
- Date of restoring into action
Rough data are the measuring results of the instrument. This may be a figure on a display, a chromatogram, a printer list with data, etc.
State which rough data are to be archived and how this is done.
Instruments may be connected to a computer which records (and interprets) the rough data. These data may, in turn, (semi)automatically or manually be transferred to a PC for calculation and/or a laboratory information management system (LIMS).
13.1 Description
Describe clearly the situation and procedures involved. Include the procedure for archiving and retrieving data and for how long data will be kept.
13.2 Software
The use of software inherently implies the occurrence of problems which may necessitate help-desk service. Therefore, the following information should be documented:
- Name of program
- Date and/or version number
- Author or supplier. Address and phone number of contact person
State which references were used for drafting the SOP (if not mentioned earlier). Also give references which may contribute to knowledge and skill of the user of the equipment.
Source: Institute for Inland Water Management and Waste Water Treatment (RIZA), Lelystad.

APP 061 - Operation of Eppendorf Varipette 4810

Page: 1 # 7

Model: APP 061Version: 1Date: 95-11-27

Title: Operation of Eppendorf Varipette 4810

7.1Volume adjustment



7.3.1Calculation of mean volume

7.3.2Calculation of bias

7.3.3Calculation of precision

9.1Maintenance by user

9.2Maintenance by supplier

Head (sign.):Date of Expiry:
Pipetting small volumes of solutions.
The pipetting mechanism is based on displacement of liquid by means of manual displacement of air above the liquid.
Volume range: 20m l - 2500 m l. Suitable for aqueous and organic solutions.
Accuracy:The closeness of the measured value to the true value,

(Note; this may also be expressed as bias: see for definition Guidelines for Quality Management)
Precision:The closeness with which replicate measured values agree.
F 001Administration of SOPs
F 011Standard instruction for drafting apparatus SOPs
APP 041Maintenance Logbook
APP 003Instrument Identification List
APP 004Instrument Maintenance List
Not applicable.
Prevent liquid from entering the pipette body at all times.
7.1 Volume adjustment
See Figure 1
1. Pull control knob until a click is heard (or felt).
2. Turn control knob until desired volume is shown on display,
3. Press control knob until a click is heard.
7.2 Pipetting
See Figure 2.
Fig.2. Liquid charge, liquid discharge, tip ejection
7.3 Calibration
Calibrate once a month with a cleaned pipette (see Section 9.1) at both minimum and maximum volume of working range and at an intermediate volume (see Table 2).
1. Pipette and weigh 10 times a chosen pipette volume of demineralized water (boiled for 15 mins. and cooled) using an analytical balance (resolution 0.1 mg). Record data on worksheet (for model see Appendix of this SOP).2. Calculate mean volume of the pipette with Equation 1 of Section 7.3.1 of this SOP,
3. Verify if accuracy (trueness) and precision are within specifications of manufacturer.
7.3.1 Calculation of mean volume
The mean volume is calculated with Equation 1:
v = mean pipette volume (m l)
g = mean of 10 calibration weighings (g)
d = density of used water (g/ml) at temperature of this water (see Table 1)
Table 1. Density of water at different temperatures
Water temp. (°C)
Density (g/ml)
Water temp. (°C)
Density (g/ml)
7.3.2 Calculation of accuracy (trueness)
The accuracy is calculated with Equation 2:
a =accuracy (%)
b = pipette setting (m l)
v = mean pipette volume (m l)
7.3.3 Calculation of precision
The precision is calculated with Equation 3:
p = precision (%)
s = standard deviation of 10 calibration weighings (g)
g = mean weight of 10 calibration weighings (g)
When the calibration results do not meet the specifications of the manufacturer (see Table 2), the pipette should not be used. If the pipette cannot be fixed by proper maintenance (see 9.1 of this SOP), then it should be fixed by the supplier or be withdrawn from service (or be used for other purposes where lower accuracy is permitted; the pipette should then be clearly marked).
Specifications of manufacturer:
Table 2. Factory specifications of the Varipette 4810
Varipette range
Setting (m l)
200 - 1000 m l
100 ± 0.8 %
£ 0.3 %

100 ± 0.6 %
£ 0.2 %

100 ± 0.6 %
£ 0.2 %
500 - 2500 m l
100 ± 0.7 %
£ 0.3 %

100 ± 0.6 %
£ 0.2 %

100 ± 0.6 %
£ 0.2 %
Problem:drops of liquid inside the pipette tip.

Cause:tip has come loose.

Solution:fix tip.
Problem:liquid dripping from tip.

Cause:wrong tip, or leak in pipette.

Solution:replace tip, or clean pipette (see 9.1).
9.1 Maintenance by user
Calibrate according to instruction in Section 7.3. Prior to calibration inspect if pipette is dirty. If so, pipette should be cleaned by qualified person. The parts of the Varipette are shown in Figure 3.
9.2 Maintenance by supplier
When a problem cannot be solved by own qualified personnel, the pipette has to be sent to the supplier for repair. (Recalibrate when returned.)
Dates and particulars of repairs, cleaning services, and calibrations must be recorded in the logbook for automatic pipettes.
Eppendorf 4810. Operation Manual, IS 92.
Source: Winand Staring Centre for Integrated Land, Soil and Water Research (SC-DLO), Wageningen.
Calibration performed by:


Pipette type + Identification no.:

Pipette setting (m l)):Min.:Max.:Intermediate
Temperature water (°C):

Density water (g/ml):

Weight (g)
Weighing no.
Min. volume
Max. Volume












Final results (see 7.3 this SOP):

Factory Specification

Sign. Head
Volume (m l)

Accuracy (%)

Precision (%)

APP 062 - Operations of electronic balance Sartorius

Page: 1 # 5

Model: APP 062Version: 1Date: 95-02-02

Title: Operations of electronic balance Sartorius 3708 MP 1




Head (sign.)Date of Expiry
To measure the mass of substances or objects.
Electronic mass compensation.
3.1 General
Serial no. 2709013. For particulars see appropriate section in Balance Maintenance Logbook.
3.2 Functional
Weighing range
0 - 320 g
0.001 g
Precision (standard deviation)
± 0.0005 g
Linearity deviation (max.)
0.001 g
Taring range (by subtraction)
320 g
Taring time
10 ms
Measuring time (approx.)
The balance should be level and prevented from
- vibrations
- large temperature fluctuations
- direct sunlight
- draught
Not applicable.
F 001Administration of SOPs
F 011Standard instruction for drafting apparatus SOPs
APPBalance Maintenance Logbook
APP 003Instrument Identification List
APP 004Instrument Maintenance List
Not applicable.
Balance pan
Spirit level
Sensitivity adjustment
Power switch
Weight display
Screws for metal house
Levelling screws
Tare sensor
Data output
Sensitivity of the balance depends on varying earth rotation velocities at different locations in the world and must therefore be checked and adjusted.
7.1 Preparation
1. Check if balance is level.
2. Turn on switch "B". Allow balance to warm up for at least 20 mins.
7.2 Checking
1. Press tare sensor "F" to zero balance.
2. Place calibration weight (e.g., 300 g) on the balance pan.
3. The weight should be 300.000 ± 0.001 g.
4. If this not the case, adjust sensitivity according to Section 7.3 below.
7.3 Adjustment
1. Remove plate "G". The sequence of the counters of the 6-digit switch corresponds with the sequence of the weight display, i.e., the right counter corresponds to the right digit of the weight display.2. Place calibration weight on the weighing pan (only if weight had been removed).
3. In case of a lower weight indication: increase value on switch until weight indication equals that of the calibration weight.
4. In case of a higher weight indication: reduce value of switch until weight indication equals that of the calibration weight.
5. Permissable tolerance in all cases: ± 0.001 g (1 in final digit).
6. Press sensor "F" to zero balance and repeat sensitivity adjustment.
7. Fasten plate "G" again.
If calibration is unsuccessful, the balance should not be used until it has been repaired.
7.4 Weighing
7.4.1 Direct weighing
1. Press tare sensor to zero balance,2. Place sample on balance pan. Read weight indication on display after illumination of stability indicator "g"
7.4.2 Weighing-in
1. Place tare container on balance pan. Press tare sensor to zero balance.
2. Transfer sample material into tare container. Read net weight on display.
Note: This procedure can be repeated as often as necessary up to the maximum capacity of the balance.
7.4.3 Weighing to a pre-set value
1. Example: pre-set value: 50 g.
2. While transferring sample to container observe the 10 g digit until "4" appears.
3. Proceed adding sample material until weight of "49" appears.
4. Continue adding procedure and watch other digits accordingly.
ProblemWeight indication does not light up, decimal point does not light up:

CausePower supply

Supply voltage

Balance not switched on

Fuse defective (Warning: when changing fuse, pull plug from socket!)
ProblemWeight indication does not light up, decimal point does

ProblemWeight indication is changing continuously

CauseBalance not switched on long enough, operating temperature not yet reached

Unsatisfactory installation conditions (draught, vibrations)
ProblemWeighing results incorrect

CauseUnsatisfactory installation conditions

Balance not levelled

Sensitivity setting incorrect (solution: adjust balance)
If balance cannot be made to function property, call qualified assistance.
9.1 Maintenance by user
- Keep balance clean
- Calibrate and adjust balance weekly and after each removal.
- Removing the balance:
1. Pull plug from socket2. Remove balance
3. Connect plug with socket
4. Level balance
5. Switch on balance
6. Wait for 20 minutes (or less if balance was warm) and adjust balance as described in Sections 7.2 and 7.3 of this SOP.
9.2 Maintenance by supplier
Have balance serviced, calibrated and adjusted once a year.
record in Maintenance (and/or Calibration) Logbook:
- All malfunctions encountered
- All actions taken to solve problems
- All calibrations
Instruction for Installation and Operation of 3707 MP 1 No date. Sartorius-Werke, Göttingen, Germany.
Source: Winand Staring Centre for Integrated Land, Soil and Water Research (SC-DLO), Wageningen.

APP 071 - Operation of pH meter Metrohm E 632

Page: 1 # 5

Model: APP 071Version: 1Date: 94-11-22

Title: Operation of pH meter Metrohm E 632







6.7Calibration and adjustment

Head (sign.):Date of Expiry:
To measure pH of soil paste, extracts, solutions, waters.
The potentiometric pH measurement is based on measuring the difference in electrical potential between solution and electrode. It is a relative measurement dependent on electrode and temperature. Therefore, the pH meter must be calibrated and adjusted (standardized) with standard buffers of known pH.
With glass electrodes the pH range is 0 - 12.
Readability: 0.01 unit.
Temperature range: 0 - 100°C.
Electrode: combination glass electrode, e.g. Metrohm 6.0203.100
F 002Administration of SOPs
F 011Standard instruction for drafting apparatus SOPs
APP 041Maintenance Logbook
APP 042User Logbook
APP 003Instrument Identification List
APP 004Instrument Maintenance List
APP ...Inspection and maintenance of pH meter Metrohm E 632
APP ...Inspection and maintenance of combination glass electrodes
Not applicable.
6.1 Principle
The standardization of the pH meter consists of two adjustment steps. The deviation of the preset ("true") value of buffer solutions is electronically compensated.
The first step is always executed with a pH 7 buffer, whereas the second step can be done with a lower (e.g. pH 4) or higher (pH 9 or 10) buffer depending on the range in which the sample measurements are made (in exceptional cases a buffer of very low pH may be required, e.g., pH 2).
6.2 Materials
Thermometer, -10 to 100 °C, accuracy 0.5 °C.
6.3 Reagents
Buffer solutions pH 4.00, 7.00 and 9.00 or 10.00 (25 °C)Dilute standard analytical concentrate ampoules according to instruction.

Note: Standard buffer solutions of which the pH values deviate slightly from these values can also be used.
WaterDeionized or distilled water, with electrical conductivity < 2 m S/cm and pH > 5.6 (Grade 2 water according to ISO 3696).

Note: If no standard ampoules are used buffer solutions can be prepared as follows (these solutions can also be prepared to act as "independent" standards):
Buffer solution pH 4Dissolve 10.21 g potassium hydrogen phthalate, C8H5KO4, in water in a 1 L volumetric flask and make to volume with water. (First dry the potassium hydrogen phthalate at 110 °C for at least 2 hrs.).

The pH of this 0.05 M phthatate solution is 4.00 at 20°C and 4.01 at 25°C.
Buffer solution pH 7Dissolve 3.40 g potassium dihydrogen phosphate, KH2PO4, and 3.55 g disodium hydrogen phosphate, Na2HPO4, in water in a 1 L volumetric flask and make to volume with water. (Both phosphates should first be dried at 110 °C for at least 2 hrs.).

The pH of this 0,25 M (of each phosphate) solution is: 6.88 at 20°C and 6.86 at 25°C,
Buffer solution pH 9Dissolve 3.80 g disodium tetraborate decahydrate, Na2B4O7.10 H2(borax), in water in a 1 L volumetric flask and make to volume with water. (Note:Observe the expiry date of borax: this may lose crystal water upon aging.)

The pH of this 0.01 M borax solution is 9,22 at 20°C and 9.18 at 25 °C.
6.4 Precautions
- The electrode must be stored in a 3 M KCl solution.
- The diaphragm of the electrode must be submerged in the solution during measurement.;
- The electrolyte level inside the electrode must be above the level of the solution being measured.
6.5 Accuracy (bias)
The pH is readable in 2 decimals. For standardization procedures and the preparation of reagents the second decimal has significance and can be used. For the measurement of soil suspensions and extracts the second decimal usually has no meaning and the result should be rounded off to one decimal. (For rules of decimal significance and rounding off see Chapter 7 of these Guidelines for QM).
6.6 Starting
- Connect electrode with socket on the back of the instrument,
- Switch on mains with push button 7 (see Figure 1). The instrument is now ready for use.
- If necessary, push button 3 (stand-by) and button 5 (pH) and set switch 13 (slope) on 1.00.
6.7 Calibration and adjustment
These should always be performed after:
- switching on the pH meter- replacement of electrode
- checking the calibration and the deviation of the pH from the theoretical value of the standard buffer appears to exceed 0.05 unit.
When the pH meter is on and already adjusted then only a check of the adjustment is needed (described in Section 7.1 of this SOP),
6.7.7 Calibration step 1
- Transfer sufficient standard buffer solution pH 7.00 to a 50 ml or 100 ml beaker.- Measure temperature of buffer and set switch 14 (temp. compensation) to this temperature.
- Immerse electrode in buffer solution and push button 4 (measure).
- With button 6 (Ucomp) adjust value on display (8) to theoretical pH value of the buffer at the measured temperature. (Note: this value can be read from a table enclosed with the standard ampoule).
- Push button 3 (stand-by). Rinse electrode with water. Setting of switch 6 (Ucomp) should now not be changed any more.
6.7.2 Calibration step 2
- Transfer a sufficient volume of one of the two other buffer solutions (pH 4 or 9) to a 50 ml or 100 ml beaker. (Note: this second buffer is chosen such that the pH of the solution to be measured falls in between , the first and second calibration buffer).- Measure temperature of buffer and adjust switch 14 (temp. compensation) to this temperature.
- Immerse electrode in buffer solution and push button 4 (measure),
- With switch 13 (slope) adjust the value on the display to the theoretical pH value of this buffer. (Note: this value can be read from a table enclosed with the standard ampoule).
The setting of switch 13 may not be lower than 0.95. If this condition is not met, this electrode may not be used for the measurement and must be exchanged for another one which does meet the condition.
- Push button 3 (stand-by) and rinse electrode with water.
- As a check, repeat readings of buffers (pH 7 first) and readjust according to Step 1 and 2 if necessary.
6.8 Measurement
- Measure temperature of solution (or suspension) to be measured and adjust switch 14 (temp. compensation) to this temperature.- Immerse electrode in solution (or suspension) to be measured.
- Push button 4 (measure) and read pH value.
Note: For Quality Control it is essential to include measurement of an independent buffer solution of known pH (as a check on calibration) and of a control sample (in each batch, to check the system under measuring conditions).
- Push button 3 (stand-by), rinse electrode with water and place in electrode holder filled with 3 M KCl solution.
- Enter use in User Logbook.
7.1 Checking of adjustment
Checking of the adjustment of previously adjusted pH meters (verification) is needed:
- Prior to each new use of the instrument.- During batch measurement. The frequency is indicated in the procedure of the investigation (e.g., after every 50 or 100 measurements or once every hour).
This verification is done with at least one of the calibration buffers indicated in Section 6.3. If the deviation exceeds 0.05 unit from the preset value, the instrument must be recalibrated and adjusted as described in Section 6.7 above.
7.2 Inspection and maintenance of electrodes
Periodical inspection of the pH electrodes, as well as inspection after complaints about malfunctioning must be carried out by a qualified technician and is described in SOP Model APP ...
7.3 Inspection and maintenance of pH meter
Periodical inspection of the pH meter, as well as inspection after complaints about malfunctioning must be carried out by a qualified technician and is described in SOP Model APP ...
Metrohm, Instructions for use, digital pH-meter E632.
Metrohm, Application Bulletin 188/1e.
Bates, R..G. (1973) Determination of pH, theory and practice, John Wiley & Sons, New York.
DIN 19266, pH-Messung, Standardpufferlösungen.
ISO 3696. Water for analytical laboratory use. Specification and test methods.
Source: Delft Geotechnics, Delft

RF 032 - Page of Reagents Book

Analysis code
Bottle no. used
Amount weighed in
Final volume
Label no.

Verified by:Date:Sign.:

PROT 011 - Protocol for custody chain of samples

Page: 1 # 1

Model: PROT 011Version: DraftDate: 96-03-26

Title: Protocol for custody chain of samples
To organize the pathway of samples through the institute.
From the arrival at the institute until the discarding or final storage, samples usually go through several hands and are processed at several places. To ensure their integrity, traceability and to prevent that they get lost, their pathway and the responsible personnel involved ("chain of custody") must be documented.
- RF 011Form for accepting delivery of samples
- RF 001Sample List
- RF 021Form for accepting order for analysis
- RF ...Sample Storage Logbook
- RF ...Sample Location Logbook
- PROT ...Storage of samples
- PROT ...Disposal of sample material
4.1Upon arrival of samples at the institute an authorized officer fills out form RF 011 (protocol for accepting delivery of samples).
4.2If there is a regular custodian, the samples are handed over to him/her. (The custodian can be the officer who received the samples).
4.3Document RF Oil is taken to the person responsible for farther processing (e.g. Project Officer, Head of Laboratory). This person signs for acceptance and keeps a copy of the form. Another copy is made for the Work Order File prepared for the corresponding work order (This file contains hard copies of all relevant information and documents concerning the work order). The original is kept at a designated place (e.g. book of forms RF 011).

Note. If samples can be received by more than one person or at more than one location/department, more than one book or file of forms RF 011 may be kept. The forms RF 011 could then be differentiated with a suffix (e.g. A, B, etc.).
4.4The whereabouts of samples are recorded by the custodian in a Sample Location Logbook. If samples are stored behind lock and key, anybody taking out (sub)samples has to sign for this in a Sample Storage Logbook.
4.5After completion of the analytical work, the sample is (re)stored for possible later use. The duration of storage is indicated in the Sample Storage Logbook. It is useful to record the location also in the Work Order File (e.g. on the Order Form RF 021).

(Duration of storage may be determined by agreement with customer or by usual procedure of the Institute, e.g. 1 year or indefinitely. This is also recorded on the order form RF 021.)
QA Officer (sign.):Date of Expiry:

RF 011 - Protocol for accepting delivery of samples

Page: A...

Model: RF 011-AVersion: 2Date: 96-01-22

Title: Form for accepting delivery of samples
Work order no.:
Date of arrival:
Name Client/Project:
Origin of samples:
Number & kind of samples:
a. ......... soil / plant / water samples*
b. ......... ring or core samples (or: ...... boxes with core samples)
c. ......... other (specify):
Condition of samples*:moist / dry / unknown
Sample list enclosed*:yes / no (if list is missing, make one for Work Order File)
Other information enclosed:

Order for analysis enclosed*:yes / no
Type of packaging*:crate / cardboard box / bag / other: ................
Number of packages:........
Condition of package*:undamaged / damaged (specify)
Samples received by:........................................sign.:
* Circle as appropriate.
Samples placed in custody of:..........................................sign.:
This document passed to:Project officer (name):..................................sign.:

: Laboratory (name): ....................................sign.:

: Other (name): .............................................sign.:

RF 021 - Form for accepting order for analysis

Page: A...

Model: RF 021Version: 3Date: 96-12-06

Title: Form for accepting order for analysis
Work order no.:
Date of arrival:
Name Client/Project:
Origin of samples:
Number & kind of samples:
a. ......... soil / plant / water samples*
b. ......... ring or core samples (or: ...... boxes with core samples)
c. ......... other (specify):
Kind or particulars of material relevant for analytical approach
Sample list correct?*:yes / no (without proper list, order cannot be processed)
Condition of samples*:moist / dry
Analytical programme submitted*:yes / no (tick requested analyses overleaf)
All samples same programme?*:yes / no (if "no", describe under Remarks overleaf)
Requested date of completion:
Sample residue*:discard / store indefinitely / store until (date): ...................
* Circle as appropriate.
Order accepted by (on behalf of lab):..................................sign.:
Entered into SOILIMS:date:sign.:
Order Confirmation sent to client:date:sign.:
Change in Registration
Entered into SOILIMS:date:sign.:
Order Confirmation to client:date:sign.:
Tick requested analyses:
· Preparation
· pH-H2O
· pH-KCl
· EC2.5
· Particle-size analysis (specify fractions below)
· Water-dispersible clay
· Exchangeable bases
· Exchangeable acidity
· Exchangeable Al
· Organic carbon
· Total carbon
· Carbonate equivalent
· Available phosphate
· Gypsum
· Dithionite extraction
· Acid oxalate extraction
· Na pyrophosphate extraction
· P-retention
· pH-NaF
· Melanic index
· DTPA extr. (Cu, Fe, Zn, Mn)
· Boron (hot water)
· Saturation extract
· 1:5 extract
· pF*011.522.
· Bulk density
· Specific surface area
· X-ray diffraction*:clay / whole sample / other fractions: ............

· Guinier photo*:clay / whole sample / other fractions: ...........

· Plant analysis (specify below)
· Water analysis (specify below)
* Circle as appropriate.

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