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ISL MINGGU 3

MICROSCALE CHEMISTRY

Microscale Chemistry (often referred to as Small-Scale Chemistry, in

German:Chemie im Mikromaßstabde:Chemie im Mikromaßstab) is not only

an analytical method, but also a teaching method widely used at school and

at university levels, working with small quantities of chemical substances. While much of

traditional chemistry teaching centers on multi-gramme preparations, milligrammes of

substances are sufficient for Microscale Chemistry. In Universities modern and

expensive lab glass ware is used and modern methods for detection and

characterization of the produced substances are very common. In schools and in many

countries of the Southern hemisphere small-scale working takes place with low-cost and

even no-cost material. There has always been a place for small-scale working

in qualitative analysis, but the new developments can encompass much of chemistry a

student is likely to meet.

History

There are two main strands of the modern approach. One is based on the idea that

many of the experiments associated with General Chemistry (acids and bases,

oxidation and reduction, electrochemistry, etc.) can be carried out in equipment much

simpler (injection bottles, dropper bottles, syringes, wellplates, plastic pipettes) and

therefore cheaper than the traditional glassware in a laboratory, thus enabling the

expansion of the laboratory experiences of students in large classes and to introduce

laboratory work into institutions too poorly equipped for standard-type work. Pioneering

development in this area was carried out by Egerton C. Grey (1928),[1]

 Mahmoud K. El-

Marsafy (1989)[2]

 in Egypt, Stephen Thompson in the US[3]

 and others. A furtherapplication of these ideas was the devising by Bradley of the Radmaste kits

[4] in South

 Africa, designed to make effective chemical experiments possible in developing

countries in schools that lack the technical services (electricity, running water) taken for

granted in many places. The other strand is the introduction of this approach into

synthetic work, mainly in organic chemistry. Here the crucial breakthrough was

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ISL MINGGU 3

MICROSCALE CHEMISTRY IN UNDERGRADUATETEACHING LABORATORIES 

  Applicable Regulations   Overview of Procedure   Waste Minimization

Procedure   Known Limitations   Safety & Health

Precautions/PersonalProtective Equipment 

  Benefits 

  Disadvantages   Project Related Costs 

Summary: Beginning in 1989, the Universityof Michigan (U-M) Department ofChemistry began implementingmicroscale chemistry techniques inthe undergraduate teachinglaboratories. Microscale laboratoryexperiments reduce the amount of

chemicals necessary to performundergraduate chemistryexperiments to a fraction of whatwas historically used. In addition to decreasing thequantities of chemicals purchasedand amount of chemical wastegenerated, microscale techniqueshave proven to be safer and morecost effective than traditional

experiments. Applicable Regulations 40 CFR Parts 260-268. State of Michigan Act 451 Part 111. Overview of Procedure Microscale chemistry is a pollution prevention method that decreasesthe amount of chemical waste generated during laboratory

experiments. This concept was first introduced by chemistry

professors at Bowdoin College in Brunswick, Maine. Standardchemistry procedures are re-written for individual experiments andspecialized microscale equipment is utilized to perform the work. Insome cases, the amount of a particular chemical needed for anexperiment has been decreased by as much as 99 percent. The U-Mhas implemented microscale chemistry in its undergraduate inorganicand organic teaching laboratories. 

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Waste Minimization Procedure Due to the number of laboratory experiments that have beenconverted to microscale, it is not practical to detail the individualprocedures. However, the following table presents a before and aftercomparison of the amounts of chemicals used, as well as the cost of

those chemicals, for an Aldol Condensation experiment. Thesequantities represent the per student amounts.

Chemical  TraditionalQuantity

(gm or ml) TraditionalChemical

Cost Micro

Quantity(gm or

ml) 

MicroQuantityChemical

Cost Acetone  5  $0.03  0.073  <$0.01 Ethanol  60  $0.60  4.1  $0.04 Benzaldehyde  5.3  $0.81  0.212  $0.03 Sodium Hydroxide  5  $0.19  0.24  $0.01 p-Anisaldehyde  5  $0.71  0.2  $0.03 p-Chlorobenzaldehyde  5  $0.36  0.2  $0.01 3,4-Dimethoxybenzaldehyde  5  $0.77  0.2  $0.03 2-Furaldehyde  5  $0.47  0.2  $0.02 1-Naphthaldehyde  5  $1.27  0.2  $0.05 

Total Cost*  $5.21  TotalCost*  $0.23 

*All costs were obtained from the 1994/95 Aldrich catalogue. Known Limitations Due to the small quantities of materials used, it may not be possible tohave enough "product" left at the end of an experiment to run a seriesof experiments. For example, experiment #1 might have generated aproduct that was used to run experiment #2, etc. However, in thetypical teaching laboratory, the "products" typically have no value andare disposed of as waste. Safety & Health Precautions/Personal Protective Equipment

 Follow all applicable safety and health protocols and regulations asestablished by your institution.

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Benefits Microscale techniques in the laboratory: 

  Reduce chemical waste produced at the source;   Improve laboratory safety by decreasing the potential for

exposure to chemicals and reducing the potential forfire/explosion hazards; 

  Improve air quality due to the greatly reduced volumes ofsolvents and other volatile substances used; 

  Reduce laboratory costs for chemical purchase and disposal;   Reduce the time required to perform experiments due to shorter

chemical reaction times;   Decrease the amount of storage space necessary for chemicals;

and   Encourage students to think about waste minimization. 

Disadvantages To begin teaching microscale techniques in the laboratory, theinstitution must purchase microscale equipment and textbooks.However, the costs can be recovered in a relatively short period oftime due to savings realized on purchase and disposal costs of reducedquantities of chemicals. Project Related Costs The table below presents a per student comparison of traditional vs.micro chemical purchasing costs for the Chemistry 216 course at the

U-M. The experiments were performed during the 1996 springsemester. All costs were taken from the 1994/95 Aldrich catalogue. 

Experiment  TraditionalCost  Micro

Cost Acetanilide  0.46  $0.05 Adol Condensation  $5.20  $0.23 Sodium BorohydrideReduction  $0.16  $0.02 Electrophilic Aromatic

Substitution $1.01  $0.02 

Diphenylacetylene  $0.99  $0.10 Tetrapheynlcyclopentadienone  $2.11  $0.08 Total  $9.93  $0.50 

The purchasing cost of chemicals for performing microscale

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experiments is 99.5 percent less than for traditional experiments. Disposal costs for the individual experiments were not calculated.However, the quantities of chemicals used for microscale experimentsare typically less than one tenth the amount used in traditional

macroscale experiments. Disposal costs should be reflective of thissignificant decrease. 

Sumber link:

http://www.scienceinschool.org/2010/issue16/microscale 

http://www.p2000.umich.edu/chemical_waste/cw7.htm