Publications

SCAT Downloads: Publications

Safe Collection of Buffer Solutions

- Active Carbon V3.0 -
Author: Peter Rebehn
Source: LABORPRAXIS Issue April 2021

The underestimated cost of laboratory air

- Ventilation in laboratories -
Author: Peter Rebehn
Source: LABORPRAXIS Issue October 2020

Safety Caps: Test Report

Efficiency of SCAT Safety Caps
(2015 Safety Caps V1.0)

Safety Caps: SGS Test Report

Safety Caps test report of
SGS Institut Fresenius GmbH
(2010 Safety Caps V1.0)

Safe Collection of Buffer Solutions

In order to correctly set or fix the pH value of an eluent (it should lie between 2 and 8), alkaline (base) and/or acidic additives, i.e. „buffer“ solutions, are added to it. After the eluent has passed through the HPLC unit, it should, in the interests of safety, be collected in a suitable collecting container. Containers/canisters of a volume greater than 5 litres should, in addition, be constructed of electrically conducting material, in order to avoid any potential danger of ignition and possible resultant explosion (see the Safety Directive, TRGS 727 / 4.55). So that working personnel are protected from harmful solvent vapours, collecting containers are equipped with filters containing active carbon. The status quo: traditionally-used active carbon (used for many years now), which however is not ideal for filtering out acids and alkalis, as it often only does so insufficiently. Its adsorptional efficiency („CTC value“) is comparitively low, as is its active surface area (600 – 1,200 m2 /g). The market leader, S.C.A.T. Europe, has now developed and introduced something extremely innovative: a product where the active surface area has been increased by no less than 25%, i.e. from 1,200 m2 /g to 1,500 m2 /g. As per the ASTM D3467 Norm, the CTC adsorption value achieved by the new active carbon (meanwhile Generation 3.0) is now 90% (hitherto 70%). Especially in order to bind and remove alkaline and acidic gases, there are now two further layers of active carbon in the filters: the first contains a reactive impregnation which converts alkaline gases, by means of „chemisorption“, and then binds them as „fully reacted“ components.

The second layer also consists of a highly active carbon, this one having been optimized for binding acidic gaseous components. With these 3 layers, the Generation 3.0 exhaust filters are able to remove more gaseous components produced during HPLC work than any others available on the market. The main advantage for the user is that only a single filter type need be employed, for all applications – even when methods or solvent compositions used are altered. Three sizes are available (with lifetimes of 3, 6 and 12 months). These continue to provide for tried and trusted solutions: smaller sizes allow for more flexibility when levels of waste being produced by HPLC units are frequently changing. If, however, larger quantities are regularly being produced, correspondingly larger filters enable annual savings of up to 35%. The laboratory operator thereby achieves not only the highest possible standard of working safety and environmental protection, but also benefits from predictably high levels of efficiency, and by enjoying the associated cost savings involved – work in the laboratory is thus made „doubly“ safe.

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The underestimated Cost of Laboratory Air

Everyday work with cancer-causing or toxic materials is unavoidable in many laboratories. There exists a corresponding danger that the workers involved can become sick as a result of respiratory illnesses they might contract. An important protective measure is therefore an efficient exchange of air in the laboratory. The German Federal Institute for Occupational Safety and Medicine (BAUA) demands fundamentally that for every square metre of floor space, 25 cubic metres of air are exchanged every hour. As a result, laboratories in Germany must be equipped with correspondingly large ventilation systems. Because a human being only breathes in around half a cubic metre of air per hour, a high dilution, and therefore a correspondingly high degree of safety, is thereby provided for, even when toxic materials are being released into it. If it is possible to prove that there is no resulting increase in risk, the BAUA will also allow for a reduced - or even just a natural - level of air ventilation. This brings short-term benefits and saves thousands of Euros.

Eightfold Exchange

Standard Conventionally, the rate of air exchange is used as a measure for gauging and evaluating air exchange. It compares the amount of air entering or leaving a room (over an hour) with the volume of air space physically located there. The Air Exchange Rate (AER) is then the resulting given ratio. An AER of 8 therefore means that all the air in a room is fully exchanged some 8 times, during the space of one hour. Exactly how much air per hour and square metre that represents, is dependent upon the ceiling height of the room. If a room has a ceiling height of 3 metres - as is the case in many laboratories - it results, approximately, in an air exchange of 25m3 /m2 h, as demanded by the BAUA. Therefore, an AER of 8 (more exactly, 8.33) is often used as the general yardstick for laboratories. To clarify further: if the ceiling height is only 2 metres, the total spatial room volume of air would have to be exchanged some 12.5 times per hour, in order to achieve the required 25m3 /m2 h.

What does Laboratory Air cost?

Usually, there is of course a basic wish to keep the amount of air exchanged as low as possible, without correspondingly endangering the health of personnel. This, because the annual costs of exchanging all the air in a laboratory are quite considerable, as the following example involving a laboratory with a floor space of 120m2 , that is running around the clock, shows:

• Air Exchange Rate (AER): 25m3/m2h

• Laboratory Area: 120m2

• Daily Time for Air Exchange: 24h

• Annual Time for Air Exchange: 365d

If these 4 parameters are multiplied by each other, the result is a total overall air exchange volume of 26,280,000 m3 /year. If an average air cost of 2 Euros per 1,000m3 and year is assumed, it results in a total overall annual cost involved of 52,560 Euros - an amount which surely offers some good potential for savings!

Safe Reduced Air Exchange

But what possibilities are there to reduce the AER, yet at the same time fulfilling the technical obligations for hazardous substances, as described in TRGS 526 and as demanded by the BAUA? As mentioned before, the TRGS allows - as described under Para. 6.2.5. - for a reduction of the AER, using various methods, provided the subsequent obligatory assessment of the hazards involved still allows for „the method used to be permanently and sufficiently sustainable and effective.“ An effective method for reducing the AER is, for instance, to use hermetically sealed caps on laboratory supply bottles. Similarly effective is the use of exhaust filters on canisters at the waste collection side. By means of such simple methods, it is actually easily possible - in conjunction with an assessment of resulting safety - to reduce the AER from a factor of 8 to one of just 5, corresponding to a reduction of 38%. Taking the a.m. annual total overall costs of 52,560 Euros, this corresponds to a savings potential of some 20,000 Euros - for air exchange, there then remain substantially reduced costs of only 32,587 Euros p.a. This cost saving is of course not equivalent to the final direct cost saving involved, as the laboratory must first be equipped with the corresponding hermetically sealed caps. As an example, a laboratory with 15 HPLC units must first undertake a corresponding investment of about 10,000 Euros in the first year (see Table 1). During the following years, there will be further annual costs of some 4,650 Euros, for the required six-monthly exchange of exhaust filters and air valves. Summing everything up, however, these additional „hardware-related“ operating costs will be very much more than compensated for by thereby achieving lower and more cost-effective rates of air exchange. Overall, the annual resultant savings enjoyed every year, as of the second year, are no less than around 15,000 Euros (see Table 2). This calculation example proves that by implementing such simple measures, every laboratory can save significantly, namely some 15,000 Euros p.a. - and without having to compromise in any way on safety.

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Test Report Efficiency of SCAT Safety Caps

Problem

What happens if an HPLC user just guides the mobile phase through capillaries in „open caps“, instead of using SCAT Safety Caps?

Test chromatograms of 3 PAHs (polycyclic aromatic hydocarbons) were used for a 31-day comparison.

Procedure

All 4 bottles were filled at the beginning with the identical mixture of water + methanol = 20 + 80 (percentage by weight). Using bottle B as a reference, a chromatogram of a mixture of three PAHs (polycyclic aromatic hydrocarbons) - naphthalene, pyrene and chrysene - was acquired for comparison. After the reference chromatogram was recorded, all bottles were stored at room temperature in a fume hood, which guaranteed a gentle air flow over the top of the bottles, for 31 days.

Test Results

The test clearly revealed that unless closed solvent delivery systems - like the ones guaranteed by using the SCAT Safety Caps - are used, unreliable retention times may be encountered even after a relatively short time. As expected, bottles A and B did not show any significant changes in their weights, so no solvent vapors escaped from those two bottles. In contrast, bottles C and D showed significant and uncontrolled loss of liquid through evaporation (see chart below). After 31 days, the separation of the three PAHs was repeated under identical HPLC conditions (same HPLC system, same column, etc.) using the liquids from bottles C and D. The result was a significant prolongation of all retention times of the test compounds, which would make compound identification based on retention times impossible. Assuming a more or less linear relationship between evaporation of the mobile phase and time, it becomes clear that even after one day of using mobile phase bottles that are not tightly closed, the user can expect changes in retention times.

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