General Rules. Before entering the laboratory, the following rules must be reviewed and understood:

Note: Many types of protective gloves are available (Perkins, 1987; NSC, 1988). Latex and natural rubber are very flexible, but they offer little resistance to organic solvents. Neoprene (or chloroprene) offers better resistance to chlorinated solvents, and nitrile (made from acrylonitrile and butadiene) is better still. Viton, however, is clearly the most protective (and most expensive), especially with PCBs, benzene, aniline. Butyl rubber is also quite good.

You should also become familiar with the laboratory shower, eye-wash, fire extinguishers and fire blanket. If you believe you may have had skin contact with a chemical or solution, immediately wash with soap and water.

Eye Wash Showers

Eye-wash Bottle Fire Extinguishers

Fire Blanket

Disposal of Chemicals. Most non-toxic solids can be discarded as normal trash. Non-toxic acids and bases can be slowly poured down the sink while flushing with large amounts of tap water. Neutral non-toxic solutions may also be poured down the sink. However, substances that are toxic, flammable, carcinogenic, or explosive must be treated as hazardous wastes. These substances are generally stored separately in glass containers for disposal by the UMass Office of Environmental Health and Safety (5-2682). Most of the chemicals used for the analysis of conventional pollutants are not considered hazardous wastes. However, many advanced or instrumental methods in environmental analysis require the use of organic solvents and halogenated organic compounds that must be disposed of as hazardous wastes.

Laboratory Notebook. It is essential that all raw data be recorded in a bound notebook at the time of data collection. Many environmental researchers use paperbound laboratory notebooks containing numbered pages with tear-out carbons. This is an excellent system, because the carbons can be stored separately so that it is unlikely that both the carbons and the original could be inadvertently lost or destroyed. If you anticipate conducting lab work for your research, you may wish to purchase a full-size lab notebook (Campus Center, University Store) for use in this course. Otherwise, a small and inexpensive bound notebook will suffice.

It is important that the laboratory notebook remain in good physical condition and legible for a long period of time. For this reason use only ball-point pens, do not use felt-tip pens or pencils. Black ink is preferred, but blue is also acceptable. Do not try to erase mistakes. Instead, draw a line through the erroneous entry and record the correct entry nearby. Write legibly, but don't be overly concerned with neatness. Pages must be used consecutively. Leaving a page or pages blank for later use is not good practice. Entries must be presented in chronological sequence and dated. Time of day should be indicated at least every 3 hours. A good practice is to reserve the first page as a periodically-updated table of contents. Avoid excess detail, so that the table of contents can completely fit on one page.

As you plan your experiments you should also think about how you will record data in the lab notebook. This will not only help to produce an organized notebook, but it may lead you to recognize a deficiency in your experimental procedure while you still have a chance to correct it. Data are often best recorded and presented in tabular form. For some repetitive procedures, standardized report forms may be most convenient. These forms should be numbered consecutively and kept in a separate notebook. Reference should be made in the laboratory notebook to the specific report form as appropriate. You should present a complete record of your experiments. All steps in a procedure should be recorded, even if they seem trivial. Very often it is the fine details which take on great importance in retrospect. Record all of your observations. Refer to standard or published procedures whenever possible. However, carefully describe any deviations you may have taken from these procedures. You should also describe any unusual aspects of the laboratory environment. For example, the smell of fresh paint, new asphalt, etc. may indicate possible sources of atmospheric contamination of laboratory solutions. (for more guidance, see Writing the Laboratory Notebook, by Kanare, ACS Publishers, 1985).

General Notes on Lab Glass. Glass is the preferred material for most laboratory purposes. It is resistant to nearly all chemicals except hydrofluoric acid. However, prolonged exposure to strong bases should also be avoided. Only the fluorocarbons are more chemically resistant. Most laboratory glassware is composed of borosilicate glass such as pyrex or kimax. This material has excellent chemical resistance, and may be heated to high temperatures without risk of breaking or significant deformation. Unfortunately, many reagent bottles are made of high sodium glass. These vessels may shatter under extremes of temperature.

Many types of glassware are equipped with ground glass joints. These allow one to assemble all-glass apparatus without the need for corks or rubber stoppers. Bottles made of high sodium glass are often fitted with low-quality ground glass stoppers. These may not seal well, and they cannot be used with the standard interchangeable joints. Borosilicate glassware will have more carefully ground surfaces. The most common joints are the conical type (cone and socket), although spherical joints may also be used. Most conical joints have the "standard taper" of 1 mm change in diameter for every 10 mm in length. Standard taper joints are designated by a two number system. For example, the common "24/40" joint has a maximum diameter of 24 mm and a ground surface length of 40 mm. These are made to be interchangeable, so that any 24/40 cone should fit any 24/40 socket.

Non-volumetric Glassware. The least expensive types of glassware are the non-volumetric pieces. For this reason, operations in the laboratory not requiring precise measurement of volume or those occurring after or prior to volume measurement are best conducted with non-volumetric glassware. Beakers and flasks may be stored either in drawers or cabinets. They are best left upside down so that their interiors are not contaminated by settling dust.

Volumetric Glassware. Volumetric glassware always contains one or more circular etched lines. When the bottom of the liquid meniscus just touches that line, the volumetric glassware is ready to either deliver the rated volume (pipets); actually contains the rated volume (flasks); or can be read to determine the precise volume delivered (burets). Volumetric glassware should be read with your eyes at the level of the meniscus, in order to avoid parallax errors. This is especially important when making buret readings.

Volumetric glassware is rated at 20oC and should always be used at or near that temperature. This is necessary, because glass expands and contracts much less than water, so that changes in temperature change the mass of water contained or delivered by volumetric glassware. Burets and pipets should be stored in drawers. Frequently used pipets may be kept upside down on the bench top in a specially designed pipet rack. Volumetric flasks should be stoppered and stored upright in wall cabinets. Volumetric glassware should be dried at room temperature. However, it need not be perfectly dry before re-use. It is a good practice to pre-rinse volumetric glassware in the liquid to be transferred, especially when the glassware is not perfectly dry. There is no need to fill the glassware with liquid, just add a small amount, swirl to wet all surfaces, and discard the rinse solution.

TABLE 11.1

Maximum Allowable Errors for Class A Volumetric Glassware

Burete Multichannel pipetter Dispensing Bottle Volumetric Pipet Pasteur Pipet

Eppendorf Pipetter Squeeze Bottle

Filter Flask Typical Filtration Apparatus Syringe filter

It is often necessary to stirr and even heat freshly prepared solutions to accelerate dissolution of solids. This is done most conveniently with the aid of a magnetic stir plate and a teflon-coated stir bar. Heat can also be used with caution. Small hot plates are common laboratory items. In some cases the functions are combined in one "hot plate stirrer". Be careful never to heat a solution in an air-tight vessel (e.g., a capped volumetric flask).

Hot plate Magnetic Stirrer

TABLE 11.2

Ring Stand Electrode

Bunsen Burner Top Loading Balance

Glassware Cleaning. For the successful analysis of environmental samples, it is imperative that glassware be scrupulously clean throughout all "crucial" steps of the analysis. Although an experienced analyst will know which steps are crucial, and where a less rigorous cleaning regimen is appropriate, the beginner will not have this advantage. Thus you are advised to always use one of the following procedures:

Water. This is the most frequently used "chemical" in the environmental laboratory. Laboratory water purification systems commonly have continuous resistivity monitors. These provide a non-specific measure of the concentration of ionic species in the product water. Theoretically pure water has a resistivity of about 18 megohms, and as the concentration of ionic species increases the resistivity decreases.

Chemical Reagents. Laboratory reagents may be purchased at a variety of chemical purities. Grades labeled "Technical" and "USP" are usually not appropriate for environmental work. Purities such as "Analytical Reagent Grade" and "ACS Grade" are acceptable. Information on the maximum concentrations of chemical impurities are often listed on the bottles. Certain types of chemically stable reagents that are commonly used as primary standards (e.g., potassium acid phthalate, arsenic trioxide) may be available as "Primary Standard Grade". These will have a very accurate assay of near 100%. High purities for specialized analysis are sometimes available, such as "Pesticide Grade", "HPLC Grade", "Spectrophotometric Grade", etc. These are more important for trace organic and inorganic analysis. Also, Aldrich Chemical Company (one of the major US supplies of specialized organic chemicals) offers a general top-of-the-line purity called "Gold Label Grade".

Reagents can become easily contaminated when used by a large number of people. Therefore, it is important that great care be exercised in handling high-purity reagents, even if some of the reagent must be wasted following each use. Solid reagents should be transferred directly from their bottle to a weighing bottle or weighing paper by carefully tilting and rotating the bottle so that a fine flow of crystals or powder is created. If a spatula must be used it should be scrupulously clean and dry. Excess reagent must be discarded. Never return excess reagent to the original bottle!

Liquid reagents are best used by pouring a slight excess into a small beaker that has been previously rinsed with the reagent. The required amount can then be pipetted from the beaker. The excess reagent should be discarded. Never return excess to the original reagent bottle, and never pipet directly from a communal liquid reagent bottle.

Table 11.3

Standard Concentrated Acids and Bases

F. WASTE DISPOSAL For a listing of acceptable waste disposal practices as UMass, refer to the brochure entitled, "Waste Management at UMass," available at the Division of Environmental Health and Safety (N-414 Morril, 5-2682). Briefly, wastes are divided into five categories, general waste, recyclable materials, chemical waste, radioactive waste, and biohazardous waste. General waste includes non-recyclable paper, glass and plastic. These can be placed in an ordinary trash recepticle. However, glass should be placed inside a "Glass Only" box lined with a plastic bag. These are available from the building custodian or EH&S. Ordinary notebook paper or bond, as well as computer paper may be recycled. These should be stored in cardboard boxes for later pick-up (call 5--0618). Most chemcial wastes may be classified as either liquid organic or aqueous. Liquid organic wastes should be stored in a glass container with a screw cap. Often an empty solvent bottle can become a recepticle for used solvent. Avoid mixing solvents and organic liquids. Waste bottles should be labeled with an EH&S "Hazardous Waste" label, tightly capped, and stored until pick-up in the bottom shelf of the vented solvent cabinet in Marcus Rm. 3N. Small liquid organic waste bottles may be stored in the back of a hood if they are used on a daily basis. Aqueous wastes not containing hazardous substances may be flushed down a drain after pH neutralization. Hazardous aqueous mixtures must be placed in a labeled bottle and stored until pick-up by EH&S.

Quantitative Transfer of Solids and Liquids. In quantitative environmental analysis it is common that solids and liquids are transferred from one vessel to another. When this is done for the preparation of standard solutions or as a preparative step in a quantitative method, accurate results depend on a complete transfer. Both solids and liquids may be transferred from one vessel (weighing dish, beaker, etc.) to a second vessel with a constricted opening (volumetric flask, erlenmeyer flask, etc.) by pouring with the aid of a funnel. The last remaining material may be transferred by a current of distilled water from a washbottle.

Preparation of Standard Solutions. Weigh the desired quantity of standard substance. For greatest accuracy, this quantity should be larger than 1 gram. Fill a volumetric flask about 1/3 full with distilled water. Then, quantitatively transfer this substance to the flask and add distilled water until it is about 2/3 full. Swirl with the cap in place until the standard is completely dissolved. Fill so that the bottom of the meniscus just touches the etched mark on the neck. Be careful not to overfill. A distilled water washbottle is especially useful at this point. Some prefer to use a disposable pasteur pipet filled from a small beaker of distilled water for better control. Finally, cap and invert 10 times to assure complete mixing. Standard solutions of less than 1 gram per liter may be prepared by a single dilution, or serial dilutions of a directly prepared concentrated (i.e., >1g/L) standard.

Very dilute standard solutions used in trace environmental analysis may require Milli-Q water rather than simple distilled water. In this case, the use of plastic washbottles may also be unacceptable (contamination from plasiticizers, etc.). The use of a disposable pasteur pipet filled with Milli-Q water is the preferred alternative.