Good practice

Laboratory glassware reprocessing – removing labels (Dr. Weigert tutorial)
Laboratory glassware reprocessing – removing marker residues (Dr. Weigert tutorial)
Laboratory glassware reprocessing – avoiding glass corrosion (Dr. Weigert tutorial)
Laboratory glassware reprocessing – reprocessing sensitive materials (Dr. Weigert tutorial)
Prerequisite/Fundamental Consideration
General handling of laboratory glass
Correct use/way of working
General aspects of cleaning
Disinfection
The degree of purity
Maintenance & Quality Assurance
Documentation and Validation
Sustainability/Environment
Laboratory glassware reprocessing – removing labels (Dr. Weigert tutorial)
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PGlmcmFtZSBzcmM9Imh0dHBzOi8vd3d3LnlvdXR1YmUtbm9jb29raWUuY29tL2VtYmVkLzVVNGhnaVRYRzFJP3JlbD0wIiBmcmFtZWJvcmRlcj0iMCIgYWxsb3dmdWxsc2NyZWVuPSJhbGxvd2Z1bGxzY3JlZW4iPjwvaWZyYW1lPg==

If you work in a laboratory on a daily basis, you will know that there is more to cleaning than meets the eye. Clean and, especially, residue-free laboratory glassware is essential to safe and successful work in the lab.

The many different types of contamination in a laboratory environment mean that residue-free and value-preserving cleaning of laboratory glassware is particularly challenging. The Dr. Weigert tutorial series “Laboratory glassware reprocessing” provides tips and recommendations for daily laboratory practice on how to clean typical contaminants on laboratory glassware efficiently and with no residue.

Label residue on laboratory glassware is one example of a familiar problem in laboratories. There are various label papers and label adhesives, some of which are easier to remove than others. For example, paper labels that can be individually inscribed are often used. Hazard warning labels can also be found on many items of laboratory glassware. And work at low temperatures, for example, requires the use of highly cold-resistant labels with outstanding adhesion properties (e.g. cryogenic labels for temperatures of minus 18 °C or below). This Dr. Weigert tutorial provides practical tips and recommendations for residue-free removal of labels.

Laboratory glassware reprocessing – removing marker residues (Dr. Weigert tutorial)
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PGlmcmFtZSBzcmM9Imh0dHBzOi8vd3d3LnlvdXR1YmUtbm9jb29raWUuY29tL2VtYmVkL0twdTdRNEE1Tm1FP3JlbD0wIiBmcmFtZWJvcmRlcj0iMCIgYWxsb3dmdWxsc2NyZWVuPSJhbGxvd2Z1bGxzY3JlZW4iPjwvaWZyYW1lPg==

If you work in a laboratory on a daily basis, you will know that there is more to cleaning than meets the eye. Clean and, especially, residue-free laboratory glassware is essential to safe and successful work in the lab.

Various reprocessing processes are used for the value-preserving cleaning of laboratory utensils. These depend on the particular contamination of the laboratory glassware. The Dr. Weigert tutorial series “Laboratory glassware reprocessing” provides tips and recommendations for daily laboratory practice on how to clean typical contaminants on laboratory glassware efficiently and with no residue.

Laboratory glassware is often inscribed for labelling. A range of markers and felt-tip pens are available for this. The various colours such as green, blue and black consist of differing dyes. Removing the residue of these dyes is difficult, and the results can vary.

In this tutorial, Dr. Weigert provides tips and recommendations for removing stubborn marker residue and felt-tip pen residue.

Laboratory glassware reprocessing – avoiding glass corrosion (Dr. Weigert tutorial)
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PGlmcmFtZSBzcmM9Imh0dHBzOi8vd3d3LnlvdXR1YmUtbm9jb29raWUuY29tL2VtYmVkL2ZPS0xFbEpWUmlrP3JlbD0wIiBmcmFtZWJvcmRlcj0iMCIgYWxsb3dmdWxsc2NyZWVuPSJhbGxvd2Z1bGxzY3JlZW4iPjwvaWZyYW1lPg==

If you work in a laboratory on a daily basis, you will know that there is more to cleaning than meets the eye. Clean and, especially, residue-free laboratory glassware is essential to safe and successful work in the lab.

The many different types of contamination in a laboratory environment mean that residue-free and value-preserving cleaning is particularly challenging and raises specific questions. The Dr. Weigert tutorial series “Laboratory glassware reprocessing” provides tips and recommendations for daily laboratory practice relating to cleaning and hygiene.

This tutorial is about how glass corrosion can be prevented. Glass corrosion, i.e. structural change of the glass surface, arises as a result of the wrong choice of cleaning process, for instance. In addition to loss of accuracy of volumetric instruments such as pipettes, laboratory glassware or measuring cylinders, glass corrosion leads to colour removal of scales. This reduces the service life of the laboratory glassware and can even cause distorted analysis results.

In this tutorial, Dr. Weigert shows that automated reprocessing is a gentle type of cleaning. By selecting the right cleaning agent that is specifically geared towards the task in hand and preserves materials, the materials used can last even longer, and glass corrosion can be prevented.

Laboratory glassware reprocessing – reprocessing sensitive materials (Dr. Weigert tutorial)
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PGlmcmFtZSBzcmM9Imh0dHBzOi8vd3d3LnlvdXR1YmUtbm9jb29raWUuY29tL2VtYmVkLzZQSVFiR1BxX2tRP3JlbD0wIiBmcmFtZWJvcmRlcj0iMCIgYWxsb3dmdWxsc2NyZWVuPSJhbGxvd2Z1bGxzY3JlZW4iPjwvaWZyYW1lPg==

If you work in a laboratory on a daily basis, you will know that there is more to cleaning than meets the eye. Clean and, especially, residue-free laboratory glassware is essential to safe and successful work in the lab.

The Dr. Weigert tutorial series “Laboratory glassware reprocessing” provides tips and recommendations for daily laboratory practice relating to cleaning and hygiene. This tutorial is about how to achieve maximum material preservation when cleaning sensitive laboratory utensils.

Various sensitive materials are used in laboratories. These include objects made of pure aluminium as well as anodised laboratory utensils such as Kapsenberg caps and test plates. The anodised coating forms an additional layer of protection and enables colour coding by means of the dyed top oxide layer.

Particularly gentle methods are required for automated reprocessing of these materials. In this tutorial, Dr. Weigert uses a cleaning experiment to show why it is important to choose the correct process parameters, and what the consequences of an incorrect cleaning program can be.

Prerequisite/Fundamental Consideration

a. Selection of laboratory glass

What is important in the selection of glass type?
Attention needs to be paid to the selection of a suitable type of glass depending on the use for the laboratory glass. Compared to soda lime glass, borosilicate glass 3.3 has a very high hydrolytic resistance (corresponds to class 1 according to ISO 719). This means that borosilicate glass is considerably more resistant to aqueous solutions and the occurrence of glass corrosion is reduced. Borosilicate glass 3.3 also has a high level of resistance to quick changes in temperature due to its very small expansion coefficients compared to soda lime glass.

What makes the quality of laboratory glass stand out?
In addition to the type of glass, the quality of the composition and the raw materials used are of decisive importance for the properties of the glass products. An even wall thickness distribution is an important criterion in order to attain a good resistance to temperature and changes in temperature as well as a high level of mechanical stability for the products. This provides protection against glass breakage and thus increases the safety in use.

Why should attention be paid to conformity to standards?
Conformity to standards is important as these set the properties and geometries for most laboratory glass products. This ensures that products can be still be obtained with the same characteristics and dimensions even after many years. In addition, characteristics which are decisive for safety such as distribution of wall thickness in beakers, for example, are given in the standards for many articles.

What is important when selecting a glass item for use?
Vor jeder Anwendung sollte die Glasoberfläche auf Beschädigungen wie Kratzer, Risse oder Ausbrüche kontrolliert werden. Insbesondere bei Arbeiten unter Druck oder hohen Temperaturen sollten nur Gefäße im einwandfreien Zustand eingesetzt werden. Beschädigte Gläser dürfen aus Sicherheitsgründen nicht verwendet werden.

b. Possible cleaning processes

What are the advantages and disadvantages of manual cleaning?

  • greater risk of injury with manual cleaning
  • quicker when there are few items to be washed, slower and less economical when there are lots of items to be washed
  • time consuming when the laboratory appliances have a complex geometry
  • flexible in terms of duration of cleaning and selection of cleaning agent

Advantages and disadvantages of cleaning in a washer/disinfector:

  • reduced breakage risk; reduced risk if injury to staffsaves staff resources
  • quicker and more economical for large quantities of items to be washed
  • inflexible in terms of duration of cleaning and selection of cleaning agent
General handling of laboratory glass

a. First steps

Does new laboratory glass have to be cleaned beforehand?
It is recommended that laboratory glass is cleaned before it is used for the first time as it is impossible to rule out contamination from dust and packing particles during transport and storage.

How should new glass be cleaned before its initial use?
As new items may be expected to be only lightly contaminated, cleaning need only take place at a low temperature with a short cycle time and with a low alkaline level.

b. Tips for storage

How can laboratory glass be stored correctly whilst saving as much space as possible?
Laboratory glass should be stored in closed cabinets or in plastic drawers in order to provide protection against dirt and grease. Contact between different glass objects must be avoided to prevent surface damage. It is best to keep laboratory glass objects in their original packaging.

c. Tips for use

How should laboratory glass be marked and with what substance so that it remains visible for as long as necessary but can be easily removed?
Laboratory glass objects are often marked with permanent markers. It must be ensured that colours that are used are relatively easy to remove again during machine cleaning. Blue colours are often easier to clean than black colours for example. The lettering can be covered with transparent adhesive film where appropriate.

What is the “compartment drier’s” optimal temperature following cleaning?
The compartment drier should ideally have a temperature of 120 °C.

How should contaminated/damaged glass be disposed of?
Borosilicate glass 3.3 should never be put in with the normal glass collection for disposal as its high melting point would cause melting problems . The user must ensure that glass is disposed of free of residues via domestic refuse or appropriately in line with the valid directives depending on possible contamination (disposal code: no. 17 02 04).

Correct use/way of working

a. How can stubborn residues be avoided?

Stubborn residues can be avoided by removing coarse residue manually before machine cleaning. In general the initial drying of soiling should be avoided. When there are very stubborn types of contamination it is recommended that the items to be cleaned are put in an immersion bath with cleaning agents before machine cleaning starts.
Autoclaving should be carried out if the biological material requires it.

b. What represents suitable disposal?

Collection containers for disposal must be appropriate to the intended content. Suitable plastic vessels have a UN number. The disposal vessels must never be closed tight during us to prevent presure build-up.

Solvent waste may contain both dissolved substances and also small amounts of deposits as the disposal containers are given directly for incineration without decanting.

Solvent waste is cost effective as many chemicals can be disposed of relatively cheaply in this way. The mixture of different reagents does however present a risk of chemical reactions which cannot be predicted. Reactive chemicals may therefore only be added to the disposal vessel in small quantities. It must also be taken into account that reactions can also be delayed if the reagents mix – for example when the disposal vessel is being transported.

Acids and alkaline solutions must be neutralised prior to disposal.

c. Which wastes/residues are separated on disposal and on what basis?

Solvent waste is disposed of separately in two categories: halogen-free and halogen-containing solvents (the background can be read in the section “Did you know…?”). Filtration and absorption masses such as e.g. chromatography films are collected in the plastic buckets provided for this purpose and passed on for disposal. Contaminated used oil from vacuum pumps is disposed of as special waste. Broken glass is collected separate to other waste in the containers provided.

d. What needs to be taken into account for bottles covered with plastic?

  • The plastic coating must be tested for resistance to the chemicals used.
  • The manufacturer’s recommened working temperature range must be taken into adhered to.
  • Glass covered with plastic must not be heated directly or with a naked flame.
  • The pressure resistance of the glass is not increased by coating.
General aspects of cleaning

a. Which resources can be used?

Abrasive material such as steel wool must not be used as these will cause surface damage to the glass. Soft sponges, cloths and brushes are suitable.

b. What requirements must a cleaning agent meet?

The selection of the correct cleaning agent is linked to the type of soiling to be removed and the framework conditions such as time, material properties and mechanical system which can be used. In addition there are also a few fundamental requirements of a cleaning agent e.g.:

  • good ability to remove dirt
  • high dirt carrying capacity
  • suitable on most surfaces
  • good rinsing properties
  • easy handling
  • not hazardous to health
  • ideally non-scenting
  • very cost effective
  • environmentally friendly

c. When would I use powder cleaners and when would I choose liquid cleaners?

  • In automated cleaning the choice is made on the basis of the construction of the machine.
  • For manual cleaning, liquid products are recommended due to the better solubility and reduced risk of abrasion to the glass.

d. Which cleaning agents are suitable for which soiling?

  • Alkaline cleaning agents: are suitable for the denaturing and removal of residues which contain protein, fat and carbohydrates
  • Acid cleaning agents: are effective against inorganic salts, lime and other carbonates.
  • Bleaching agents help with the removal of paints and with disinfection.

e. How does the water used affect the cleaning result?

The degree of water hardness (given in °d) results in the concentration of magnesium and calcium ions in the water. If water with a high degree of hardness is used for cleaning, significant residues may be deposited on the cleaned surfaces.
Reduced hardness waters produced by difference methods such as ion-exchange vary in their interactions with cleaning agents and thus the effectiveness of the cleaning system. It is therefore recommended that both the material to be cleaned and the water to be used are considered when selecting a cleaning agent.

f. How can joint grease be removed from small openings?

Pipe cleaners can be used to mechanically remove grease from glass stopcocks, for example. Pipe cleaners can, however, leave lint behind. PTFE keys or plugs can be used as an alternative to glass in many systems and do not require the use of joint greese.

Disinfection

a. In which work areas does disinfection play a role?

Disinfection plays a role in the following areas among others: microbiology, pathology, diagnostics, histology, immunology and production of cosmetics, medicines and foodstuffs..

b. When is disinfection absolutely necessary?

In all areas in which personal protection against infectious material (e.g. organisms which have been genetically modified, blood tests, pathogenic germs) or the prevention of a transfer of germs (e.g. cosmetic agents, medicines etc.) are necessary.

c. What requirements must a disinfecting agent meet?

The selection of the correct disinfecting agent is linked to the spectrum of action and the framework conditions such as time, material properties and mechanical system which can be used. In addition there are also a few fundamental requirements of a disinfecting agent e.g.:

  • adequate spectrum of action
  • effective with low concentrations
  • short reaction time
  • suitable on most surfaces
  • good wetting
  • good rinsing properties
  • ideally no scenting (has additional potential for allergies)
  • very cost effective

d. What needs to be taken into account for disinfection?

  • The shelflife given by the manufacturer must be observed and not exceeded.
  • The stability of the products must be checked regularly.
  • Gloves should be worn for protective reasons.
  • Disinfectant solutions must be applied with cold water (this means that no unnecessary steam is produced).

e. Which disinfecting agent is the right one?

Various active agents are available for disinfecting agents and these must be used according to a required area of action and application.

The degree of purity

a. What does “clean glass” actually mean?

First of all this means that the surface of the laboratory glass can be described as optically clean. Secondly, the surfaces of the laboratory glass must also be free of residues which could affect the analytical results, for example.

b. How residue-free does the glass have to be?

With automated cleaning ,the programme sequence will determine how many cleaning stages occur. Once the machine programme has been completed it can be assumed that the items cleaned have only minimal residues of process chemicals on them. For many laboratory applications this is perfectly satisfactory.

For analytical work where trace element detection is important, or critical applications such as pharmaceutical production, then even the low levels of residues on the items washed plays an important role: acceptable residue limits for cleaning and disinfecting agents must be determined following cleaning. Ideally it should not be possible to detect any residues.

c. How is freedom from residues attained?

It must be ensured that the washing machine mechanism is working correctly e.g. the rotating arms of the machine must move freely. In addition sufficient cleaning stages must be carried out for both machine and manual cleaning to remove any cleaning agents residues. The following factors also play a role here: reaction time, temperature and process chemicals.
Items with bases such as bowls, beakers etc should be placed in the carrier or basket with the opening facing downwards as a preventative measure to avoid spreading process chemicals. These vessels should be fixed in position during cleaning so that they cannot be overturned by the cleaning mechanism.

Maintenance & Quality Assurance

a. When/how often does the machine have to be given maintenance?

Regular checks must be carried out.

b. When should a laboratory glassware no longer be used?

Surface damage changes the thermal and mechanical properties of the glass. This means that glass items with cracks, impact damage, scratches, stars, chips and other visible damage should be separated and disposed of.

Documentation and Validation

a. Why is documentation of the cleaning required?

The scope of a validation is determined on the basis of regulatory guidelines in combination with the results of an internal risk analysis. The documentation of the cleaning then emerges from this scope.

b. Who has to keep records?

The operator of a facility is responsible for the documentation.

c. When is validation of the cleaning process relevant?

  • The EU GMP guidelines for human and animal medicines are binding in the pharmaceutical field on the basis of regulatory guidelines.
  • In the validation of manufacturing or cleaning processes, documented verification about suitable, applied processes/methods which reliably and consistently attain a given target are produced.

d. How does validation take place?

The minimum quality requirements for the product or the cleaning performance are determined by the person responsible for validation according to a company specific risk analysis.

Determination of worst case scenario
The parameters for the validation of cleaning processes must refer to toxicity data which are known for many chemical substances (process chemicals and medicines) e.g. NOEL (no observed effect limit), ADI (acceptable daily intake), MACO (maximum allowable carryover) and LD50 oral rat (lethal dose).

Checking of the cleaning performance with test specimens
The cleaning performance of cleaning machines installed in the laboratory can be established by means of test specimens which have been contaminated for test purposes. The test specimens must be sufficiently relevant to practice with reference to the material, the surface structure and dimensions.

Method Validation
The use of validated methods of analysis is required in the context of cleaning validation. It should be possible to carry out the method of analysis with a cost which can be justified economically on the one hand and which is sufficiently sensitive and specific to the contamination or residues on the other. Methods of analysis which are validated in line with the latest state of technology should be used. The characteristic data thus established must be recorded with particular attention being paid to standard guidelines.

Manufacturer’s Supporting Documents:
In order to support pharmaceutical customers in the implementation, the manufacturer should make relevant documents available such as e.g. a clearance certificate according to LFGB, and provision of validated methods for determining residue etc.

Sustainability/Environment

a. Why does multiple use and preparation of laboratory glass make ecological sense?

Unlike plastic articles, articles made of laboratory glass can be used for many years if used and prepared appropriately, thereby protecting the environment. Laboratory glass is also made of natural raw materials.

b. Environmental compatibility of cleaning agents – What is the best way of conserving the environment when using cleaning agents?

Sparing use of cleaning agents is a basic prerequisite for environmental conservation. Manufacturers’ dosing recommendations should be adhered to. This prevents wastage of chemicals through overdosing and repeated cleaning due to underdosing is avoided.

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