305 Laboratory Safety Rules Before beginning any type of laboratory work, it is important to understand the potential hazards in the laboratory, to be familiar with the precautions and rules, and to recognize and avoid the causes of those hazards. According to the Occupational Safety and Health Act (OSHA), “[E]ach employer has the general duty to furnish each of the employees a workplace free from recognized hazards causing or likely to cause death or serious harm.” Comprehensive safety training is essential for all labora- tory workers . 19.1 LABORATORY HAZARDS Laboratory hazards can be categorized as chemical hazards, fire hazards, and careless habits. 19.1.1 CHEMICAL HAZARDS Virtually all chemicals are toxic to some extent, and care should be taken in handling them. Chemical hazards may be minimized by the following precautions. 19.1.1.1 Cleanliness Cleanliness in the laboratory is essential: • Wash hands periodically and immediately after contact with chemicals and just before leaving the laboratory. • Never drink from laboratory glassware. • Keep work areas clean. Clean working areas before and after work. • Use clean laboratory coats and aprons. These garments are designed to protect the body from chemical spills. Dirty clothing can be a source of health hazards and contamination. 19.1.1.2 Eye Protection The eyes are especially susceptible to injury from chemicals. Breakage of glass containers of acid, bases, and other chemicals and out-of-control chemical reactions are the principal hazards. Safety glasses, goggles, or face shields should be worn during laboratory work. In the event of chemical spray in eyes, immediately flood the eyes with water using a specially designed eye-wash fountain or quick flushing with water from the nearest tap, and seek medical attention as soon as possible. 19.1.1.3 Skin Contact with Certain Chemicals Chemical burns can result from contact with strong acids or bases. Certain chemicals are absorbed through the skin. Because many chemicals absorb rapidly through the skin, prompt clean-up is im- portant. Remove contaminated clothing immediately and flush affected areas with a large quantity of water. Medical attention may be necessary, depending on the amount of chemical involved. 19 © 2002 by CRC Press LLC 306 Environmental Sampling and Analysis for Metals 19.1.1.4 Body Protection • Use laboratory coats or aprons. Laboratory coats are made from materials that provide protection against acids and bases. Laboratory aprons are not affected by ordinary corro- sive fluids or other chemicals. • Never wear open-toe shoes or sandals. This type of footwear offers little or no protection against chemical spills or broken glass. • Secure ties or scarves with fasteners. • Put long hair up and out of the way. • When handling corrosive chemicals, use protective gloves. Protective gloves are selected according to need. Asbestos gloves protect against heat, but they are not advisable for han- dling corrosive chemicals (acids or bases), because asbestos absorbs the substance and in- creases contact time and area. When working with hot objects or organic solvents, do not use rubber or plastic gloves, because they may soften and dissolve. 19.1.1.5 Ingestion of Toxic Chemicals Do not consume or store food or beverages in the laboratory. Food is easily contaminated, such as by traces of chemicals on hands. To avoid any possibility of ingesting chemical solutions while using a pipet, use a pipeting bulb and not the mouth. 19.1.1.6 Inhalation of Volatile Liquids and Gases The presence of these substances in the air (even in low concentrations) is hazardous. Acute expo- sure to extremely high concentrations in vapors (above the maximum allowable concentration) can cause unconsciousness and even death, if the person is not removed from the area and if medical at- tention is delayed. The exposure to solvent and chemical vapors can be avoided by working with such chemicals under chemical hoods and wearing protective respiratory devices. Good ventilation is es- sential to a safe laboratory. 19.1.1.6.1 Toxicity of Metallic Elements Metals with a specific gravity of greater than 5 are called heavy metals. In the metallic state they are harmless, but in the vapor state these elements and their soluble compounds are toxic. The most com- mon heavy metals are antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mer- cury (Hg), nickel (Ni), silver (Ag), and thallium (Tl). 19.1.1.6.2 Chemical Dust Fine-powder chemicals can be inhaled as dust; therefore, these chemicals should also be handled under a laboratory hood. 19.1.1.7 Chemical Spills 19.1.1.7.1 Solid, Dry Substances Spills of chemicals in this form can be swept together, brushed into a dustpan or cardboard recepta- cle, and then deposited in an appropriate waste container. 19.1.1.7.2 Acid Spills Clean up acid spills by using the appropriate spill kit and following the instructions. The material in such kits neutralizes and absorbs the acid for easy clean-up. Afterwards the area should be washed with water. Alternatively, use soda ash (Na 2 CO 3 ) or sodium bicarbonate (NaHCO 3 ) solution for neu- tralization, and then flush the area with water. © 2002 by CRC Press LLC Laboratory Safety Rules 307 Caution: When water is poured on spills of concentrated sulfuric acid (H 2 SO 4 ), tremendous heat is released (exothermic reaction) and the acid splatters. Deluge with water to dilute the acid to min- imize heat generation and splattering. 19.1.1.7.3 Alkaline Spills Alkaline spills are treated similarly to acid spills; use an alkaline spill kit. Alternatively, use a weak acid solution, such as diluted acetic acid, for neutralization. The area should then be flushed with water to a floor drain. If a mop and bucket are used, flush by replacing water frequently. Caution: Alkali solutions make the floor slippery! Clean sand can also be used to clean up alkaline spills. Throw sand over the spill and sweep up. The wet sand is then discarded. 19.1.1.7.4 Volatile Solvent Spills Volatile solvents evaporate very rapidly because of the extremely large surface area. This kind of the spill can create a fire hazard if the solvent is flammable and will invariably cause highly dangerous concentrations of fumes in the laboratory. When inhaled, these fumes cause serious injuries. They may also become explosive upon mixing with air. To clean up a small spill, wipe up the liquid with absorbent cloths or towels and discard them in an appropriate waste receptacle. If a large amount of solvent is involved in the spill, use a mop and pail. Squeeze out the mop in the pail and continue as needed. 19.1.1.7.5 Oily Substance Spills This type of spill should be cleaned up with an appropriate nonflammable volatile solvent. Pour sol- vent on an absorbent cloth, and wipe up the spilled substance. Rinse the cloth in a pail of solvent to remove all spilled material, because oily floors are slippery and dangerous. Finally, thoroughly scrub with detergent and water to remove oily residue. 19.1.1.7.6 Mercury Spills Spills are one of the most common sources of mercury vapor in laboratory air. In a spill, mercury may be distributed over a wide area, exposing a large surface area of the metal, and droplets become trapped in crevices. Unless the laboratory has adequate ventilation, mercury vapor concentration (ac- cumulated over time) may exceed the recommended limit. Vibration increases mercury vaporization. Caution: Surfaces that appear to be free of mercury will harbor microscopic droplets. To clean up mercury spills, push droplets together to form pools, and then use a suction device to pick up the mercury. If there are cervices or cracks in the floor that can trap small droplets of mer- cury that cannot be picked up, seal over the cracks with a thick covering of floor wax or an aerosol hair spray. The covering will dramatically reduce vaporization. Sulfur powder can also be used to fix mercury. Mercury spill kits are also available for proper mercury clean-up. 19.1.2 FIRE HAZARDS Fire in a chemical laboratory can be dangerous and devastating. In case of fire, stay calm and think! Sources of fires include electrical equipment, friction, mechanical sparks, flames, hot surfaces, and flammable organic compounds. Accidental ignition of volatile organic solvents is perhaps the most common source of laboratory fires. To avoid accidental spills and reduce fire hazards, keep volatile solvents in small containers and never work with a volatile solvent around an open flame. The sooner you respond to put out a fire, the easier it is to control. © 2002 by CRC Press LLC 308 Environmental Sampling and Analysis for Metals 19.1.2.1 Fire Classifications The appropriate response to a fire depends on the type of material being consumed. The use of the wrong type of firefighting equipment may increase the intensity of the fire. Fire classifications are described below. 19.1.2.1.1 Class A Fires These fires are caused by the burning of paper, wood, and textiles. Almost any type of extinguisher is satisfactory. 19.1.2.1.2 Class B Fires This type of fire is caused by the burning of oil, grease, organic solvents, and paint. Use a dry-chem- ical, liquid, CO 2 , or foam extinguisher. 19.1.2.1.3 Class C Fires This type consists of electrical fires in equipment. Do not use a water or foam extinguisher, because you may become a part of the electrical circuit and be electrocuted! Use a CO 2 or dry-chemical fire extinguisher only. 19.1.2.1.4 Class D Fires Class “D” fires are caused by sodium, potassium, magnesium, lithium, and all metal hydrides. Use a dry, soda-ash fire extinguisher, sodium chloride, or dry sand. 19.1.2.2 Fire-Fighting Responses 19.1.2.2.1 Fire in Clothing Wrap the person in a fire blanket or heavy towels. Use an emergency shower. 19.1.2.2.2 General Fires Select the proper fire extinguisher according to the type of fire. First, cool the area around the fire with the extinguisher to prevent the fire from spreading. Next, use the extinguisher at the core area of the fire. Finally, extinguish scattered remnants of the fire. 19.1.2.2.3 Electrical Fires First, disconnect the apparatus by pulling the safety switch to avoid the possibility of being electro- cuted. Then, use class C (CO 2 or dry chemical) extinguisher. 19.1.2.2.4 Poisonous Gas Fires Use an appropriate respirator, and select the proper fire extinguisher. If the fire gets beyond the con- trol of the available fire extinguisher, get out of the room immediately. Close the door to prevent drafts and gas spread. Always be certain that no one is left behind. In case of fire, immediately notify the local fire department! 19.1.3 CARELESSNESS Most laboratory accidents are caused by impulsive acts that later seem thoughtless, careless, and even reckless. Thus, always think about the possible consequences of your actions before you act. 19.1.3.1 Hazards from Falling Objects Falling objects can cause serious injuries. Do not place heavy objects on high shelves! If a heavy ob- ject must be placed on a shelf, secure it with a belt or chain. Be careful when moving heavy instru- ments and other heavy objects; use a laboratory cart whenever possible. © 2002 by CRC Press LLC Laboratory Safety Rules 309 19.1.3.2 Hazards from Falling Never climb on drums, cartons, or boxes to reach objects located on high shelves. You may be se- verely injured, and the injury can be compounded by breakage of glassware or chemical splash. Always use a safety stepladder; special locking devices ensure that the rubber-tipped legs do not move. 19.1.3.3 Transporting Large Bottles Moving large bottles and carboys is a dangerous operation because of the potential for bottle break- age and liquid spillage. Always use safety carts and safety bottle carriers when transporting large bot- tles of chemicals. Safety bottle carriers prevent shock and breakage. 19.2 SAFE HANDLING OF COMPRESSED GASES Cylinders of compressed gas can be dangerous because gases are contained under very high pressure. Always follow safety precautions when handling such cylinders. 19.2.1 GENERAL PRECAUTIONS WHEN WORKING WITH COMPRESSED GASES 19.2.1.1 General Precautions • Close off main cylinder valve when not in use. • Close needle valve or auxiliary cut-off valve in the line and the cylinder. Do not rely solely on the cylinder valve. • Replace cylinders within reasonable time periods. Corrosive gas cylinders should be re- placed every 3 months or less. • Always use gases in areas where adequate ventilation is provided. • Keep cylinders in outside storage, or use manifolds that pipe low-pressure gas into buildings. • Use the smallest cylinder that is practical for the purpose. 19.2.1.2 Safety Rules for Using Compressed Gases • Cylinder contents must be properly identified: Do not use cylinders without written con- tent identification. Do not rely on color codes for identification. Do not destroy identifi- cation tags or labels. • Protect cylinder valves. Use only cylinders equipped with protective valve caps. Leave caps in place until ready to use the gas. • Store properly. Provide specifically assigned locations for cylinder storage, preferably in a dry, fire-resistant, and well-ventilated area away from sources of ignition or heat. Outdoor storage areas should have proper drainage and be protected from direct sunlight. Secure cylinders by chains or other means to prevent accidental tipping or falling • Transport correctly. Transport cylinders by means of a suitable hand truck. Do not roll cylinders on the ground! • Do not drop. Never drop cylinders or permit them to strike each other. • Return in condition received. Close valve, and replace cylinder-valve protective cap and dust cap. Mark or label cylinder “EMPTY” or “MT.” • Prevent confusing empties with full cylinders: Store empty cylinders in an area separate from full cylinders. Connecting an empty cylinder to a pressurized system could cause contamination or violent reaction in the cylinder. © 2002 by CRC Press LLC 310 Environmental Sampling and Analysis for Metals 19.2.2 HAZARDOUS PROPERTIES OF COMPRESSED GASES The properties of a compressed gas must be well known and understood before the gas is put to use. Hazards include flammability, toxicity, and corrosivity. 19.3 STOCKROOM SAFETY RULES The laboratory stockroom should be adequate and efficiently planned for safe operation. 19.3.1 SAFETY CHECKLIST FOR STORAGE ROOMS: Room Characteristics and Organization • Wide aisles, adequate lighting, and no blind alleys; the entire complex should be orderly and clean • Adequate ventilation and emergency exhaust system • Well-marked exits, including emergency exits • Adequate fire-protection and firefighting equipment • Heavy items stored near the floor • Proper storage for glass apparatus and tubing (never projecting beyond shelf limits) • Fragile and bulky equipment secured to shelving. • Shelving fitted with ledges to prevent items from sliding or rolling off • Appropriate grouping and separation of liquids and hazardous chemicals • No waste accumulation of any kind • Safety ladders available; all laboratory personnel should be encouraged to use safety lad- ders, because they prevent accidents and save time and effort • No excessive heat, because of fire hazard • Regular housekeeping activities aimed at maintaining safe storage practices 19.3.2 CHEMICAL STORAGE Chemicals are manufactured in varying degrees of purity. Carefully select the grade of the chemical that meets the need of the work to be done. Always recheck the label of the chemical that you are using! The use of a wrong chemical can cause an explosion or ruin the analytical work. Carefully check the information on the chemical container, including name, formula, formula weight, percent impurities, analytical grade, health hazards, and safety codes. 19.3.2.1 Acids Acids should be stored in original containers in cabinets labeled “Acids” and grouped by safety color codes. Bottles with impact-resistant plastic coatings are preferred. 19.3.2.2 Flammable Solvents Store these chemicals in original containers, in cabinets labeled “Flammable.” Large quantities should be stored in metal safety cans outside of the laboratory in an area marked “Flammable Storage Area.” 19.3.2.3 Solvents Solvents should be stored in original containers in a separate cabinet labeled “Solvents” and in a well- ventilated area. © 2002 by CRC Press LLC Laboratory Safety Rules 311 19.3.2.4 Chemicals Used in Volatile Organic (VOC) Analysis These chemicals should be stored in original containers in a separate, appropriately labeled cabinet and in a well-ventilated area. No other chemicals should be stored along with them. 19.3.2.5 Storage Organization Chemicals should be stored in alphabetical order in the storage room, with records of date of arrival and date of opening affixed to each container. Store phenol and hydrogen peroxide in a refrigerator la- beled with “Chemical Storage.” The LabGuard Safety Label System on chemical bottles assists in the proper storage of chemicals. Each chemical used in the laboratory should be accompanied by a Material Safety Data Sheet (MSDS). MSDSs contain ingredients, physical and chemical characteris- tics of the substance, physical hazards, reactivity and health hazards involved, and safe handling and safety precautions. In addition, control measures to reduce harmful exposures are also listed in every MSDS. 19.4 SUMMARY OF LABORATORY SAFETY RULES 1. Safety glasses/corrective glasses should be worn at all times in the laboratory. Visitors to the laboratory must be appropriately warned and safety glasses made available to them. 2. Participation in practical jokes or “horseplay” in the laboratory is not permitted. 3. Each laboratory worker is expected to cooperate in keeping his or her working area in a neat and orderly condition and to cooperate with others in keeping the entire laboratory neat and orderly. A clean laboratory is a safe laboratory. 4. Proper techniques should be utilized when lifting, pushing, pulling, or carrying materials to prevent injuries. 5. All laboratory personnel must know the location of fire extinguishers, safety showers, eye- wash stations, and spill kits. 6. All laboratory workers must know how and when to use the equipment listed in item 5. 7. Eating, drinking, and smoking in the laboratory are never allowed. Never use laboratory containers (beakers or flasks) for drinking. 8. No food or beverages intended for human consumption are stored in refrigerators in the laboratory. 9. MSDSs must be attached to all chemicals used in the laboratory. 10. All chemicals should be clearly labeled. Do not use material from unlabeled containers. Ensure that chemicals are clearly identified before using them. 11. In the event of chemical spraying in the eyes, use the eyewash station and report the inci- dent to the laboratory supervisor. 12. Respirators must be used when working with hot acids or solvents that are handled when not under a fume hood. 13. Pouring of volatile liquids should be done only in a well-ventilated hood remote from sources of ignition. 14. Only minimum amounts of flammable liquids that are necessary for running a test should be kept on workbenches. 15. Heavy reagent containers, such as 5-gallon containers, must not be carried or placed on a shelf by one person working alone. 16. Face shields, rubber gloves, and protective rubber aprons should be used when preparing, transporting, or pouring corrosive chemicals, such as concentrated acids and bases. 17. When diluting acid with water, always add the acid to the water, stirring constantly. Never © 2002 by CRC Press LLC 312 Environmental Sampling and Analysis for Metals add water to the acid, as this produces a violent reaction. 18. When drawing liquid into a pipet, always use a suction bulb. Mouth pipeting is never allowed. 19. Pouring mercury into a sink or drain is strictly prohibited. Mercury will remain in the trap and continue to vaporize and contaminate the air. 20. In the event of an acid spill on a person, flush thoroughly with water immediately. Caution: Acid–water mixtures produce heat. Removal of clothing from the affected area while flush- ing may be important so as not to trap hot acid–water mixtures against the skin. Acids or acid–water mixtures can cause very serious burns if left in contact with skin for even a very short period of time. 21. Weak acids should be used to neutralize base spills, and weak bases should be used to neu- tralize acid spills. Such solutions should be available in the laboratory in case of emer- gency. Acid and base spill kits are also available. 22. Unsupervised or unauthorized work in the laboratory is not permitted. 23. Never wear open-toed shoes or sandals because they offer little or no protection against chemical spills and broken glassware. 24. Keep ties and scarves secured with fasteners. Do not wear medallions, pendants, or other hanging objects. 25. Tie long hair up and out of the way. 26. Asbestos gloves should be worn when handling or working with hot materials. 27. Gloves should be worn when exerting pressure is necessary to open jars, bottles, or other containers. 28. A face shield should be worn when handling a receptacle containing more than 1 liter of acid, alkali, or corrosive liquid. 29. Chemicals should never be transported, transferred, poured, or otherwise handled at a height above one’s head. 30. Any injury, regardless of how superficial, should be reported to the laboratory supervisor (or instructor in a school laboratory), and appropriate first-aid action taken. 31. A leakage check should be made on all gas lines and connections whenever a line is bro- ken and reconnected. 32. Immediately report to the laboratory supervisor any failure of exhaust fans to evacuate va- pors completely, defective electrical equipments, faulty or empty fire extinguishers, and worn or defective rubber gas-burner hoses or other gas hazards. 33. Use a stepladder provided for this purpose when reaching into high shelving. 34. Never leave operations involving explosives or flammable mixtures unattended. 35. When transporting a large quantity of bottles, do so with a basket or receptacle designed for this purpose. 36. Do not use damaged glassware. 37. Do not place glassware close to the edge of the laboratory bench; a passerby may knock it off. 38. Wear goggles or a face shield when working with a glass apparatus that is under pressure or vacuum. 39. When making a vacuum distillation, use a shield to guard to protect against explosion and fire hazard. 40. Clean up broken glass immediately and place it in containers provided for broken glass. Never dispose of broken glassware in a regular garbage container! © 2002 by CRC Press LLC 353 References Alcamo, L.E., Fundamentals of Microbiology, 4th ed., Benjamin Cummings, Menlo Park, CA, 1994. Ayers, D. et al., Environmental Science and Technology Handbook, Government Institutes, Rockville, MD, 1994. Beaty, R.D., Concepts, Instrumentation and Techniques in Atomic Absorption Spectrophotometry, Perkin Elmer, 1988. Boss, C.B. and Kenneth J. Freeden, Concepts, Instrumentation, and Techniques in Inductively Coupled Plasma Emission Spectrometry , Perkin Elmer, 1988. Brady, J.E. and Holum, J.R., Chemistry: The Study of Matter and Its Changes, John Wiley & Sons, New York, 1993. A Concise Dictionary of Chemistry, 2nd ed., Oxford University Press, Oxford, 1990. Csuros, M., Environmental Sampling and Analysis for Technicians, Lewis Publishers, Boca Raton, FL, 1994. Csuros, M., Environmental Sampling and Analysis Lab Manual, Lewis Publishers, Boca Raton, FL, 1997. Day, R.A., Jr. and Underwood, A.L., Quantitative Analysis, 6th ed., Prentice Hall, New York, 1991. Driscoll, F.G., Groundwater and Wells, 2nd ed., Johnson Division, St. Paul, MN, 1986. Ebbing, D.D., General Chemistry, 4th ed., Houghton Mifflin, Boston, 1993. Environmental Protection Agency, Handbook for Sampling and Sample Preservation of Water and Wastewater, Government Printing Office, Washington, D.C. (EPA 600/4–82–029), 1982. Environmental Protection Agency, Methods for Chemical Analysis of Water and Wastes, rev., Government Printing Office, Washington, D.C. (EPA-600/4–79–020), March 1983. Environmental Protection Agency, Standard Methods for the Examination of Water and Wastewater, 18th ed., Government Printing Office, Washington, D.C. (APHA-AWWA-WPCF), 1992. Environmental Protection Agency, Test Methods for Evaluating Solid Waste, 3rd ed., Government Printing Office, Washington, D.C. (EPA SW 846), 1986. Friedman, B., Environmental Ecology, Academic Press, New York, 1989. Fritz, J.S. and Schenk, G.H., Quantitative Analytical Chemistry, 5th ed., Allyn & Bacon, Boston, 1987. Furr, A.K., CRC Handbook of Laboratory Safety, 4th ed., CRC Press, Boca Raton, FL, 1995. Greenfield, S., Jones, I.L.I., and Berry, C.T., High pressure plasma spectroscopic emission sources, Analyst, 89, 713–720, 1964. Joesten, M.D., World of Chemistry Essentials, Saunders College, Fort Worth, TX, 1993. Keenan, J., Quality Assurance in Chemical Measurements, Lewis Publishers, Boca Raton, FL, 1988. Kenkel, J., Analytical Chemistry for Technicians, 2nd ed., Lewis Publishers, Boca Raton, FL, 1990. Malachowski, M.J. and Goldberg, A.F., Health Effects of Toxic Substances, Government Institutes, Rockville, MD, 1995. Martini, F., Fundamentals of Anatomy and Physiology, 2nd ed., Prentice Hall, New York, 1992. Sullivan, T.F.P., Environmental Law Handbook, 16th ed., Government Institutes, Rockville, MD, 2001. Wolfe, D.H., Introduction to College Chemistry, 2nd ed., McGraw-Hill, New York, 1988. © 2002 by CRC Press LLC 313 Appendix A: Operation of Mass Spectrophotometer MASS SPECTROSCOPY Mass spectroscopy is a technique used to determine relative atomic masses and the relative abundance of isotopes, in chemical composition analysis and the study of ion reactions. In a mass spectrometer, a sample (usually gaseous) is ionized and the positive ions produced are accelerated into a high-vac- uum region containing electric and magnetic fields. These fields deflect and focus the ions onto a de- tector. The fields can be varied in a controlled way so that ions of different types hit the detector. OPERATION OF MASS SPECTROPHOTOMETER 1. All the air is pumped out of the instrument. 2. The sample (gaseous vapor of liquid or solid) is fed into the ionization chamber of the spectrophotometer. 3. The sample is then exposed to a beam of rapidly moving electrons. When an accelerated electron collides with an atom and knocks another electron out of it, the atom becomes a positively charged ion. 4. The positive ions are accelerated out of the chamber by a strong electric field. Speeds at- tained by the ions depend on their masses, with light ions reaching higher speeds than heavy ones. 5. When the accelerated ions pass through a magnetic field generated by an electromagnet, their paths are bent to an extent dependent on speed and hence on mass. 6. A signal is produced when the strength of the magnetic field is just enough to bend the beam of ions so that they arrive at the detector. 7. The mass of the ion formed is then calculated based on the accelerating voltage and strength of the magnetic field used to produce the signal. The process of sample inlet system → Ionization chamber → Mass analyzer → Detector → Signal A is shown in Figures A.1 and A.2, respectively. MASS SPECTRUM The mass spectrum obtained in the spectrophotometer signal consists of a series of peaks of variable intensity to which mass/charge (m/e) values can be assigned. The mass spectrum is a plot of the de- tector signal against the magnetic field. The positions of the peaks are used to calculate the mass of accelerated ions, and the relative heights of the peaks indicate the proportions of ions of various types. For organic molecules, the mass spectrum consists of a series of peaks, one corresponding to the parent ion and the others to fragment ions produced in the ionization process. Molecule compo- sition can be identified by characteristic patterns of lines. © 2002 by CRC Press LLC [...]... (b 191 6) and Watson (b 192 8), working in the Cavendish Laboratory at Cambridge, built scale models of the double helical structure of DNA based on x-ray data from Rosalind Franklin (192 0 195 8) and Maurice H.F Wilkins (b 191 6) Knowing distances and angles between atoms, they compared the task to solving a three-dimensional jigsaw puzzle Watson, Crick, and Wilkins received the Nobel Prize in 196 2 for. .. LLC 328 Environmental Sampling and Analysis for Metals toward the base Xylem and phloem transport occurs in the opposite direction in leaves, roots, and stem, but in the same direction in fruits The latter may be responsible for significant metal accumulation in seeds and fruits METAL ACCUMULATION Supplying micronutrients (essential metals) continues to be an important issue in plant cultivation For optimal... Press LLC 332 Environmental Sampling and Analysis for Metals Szabo, L., Kevey, B., and Tolgyesi, Gy., Macroelement and microelement accumulation in the plant species of hornbeam-oak communities living on different parent material in the Mecsek mountains Bot Kozlem., 72, 1–2, 77–88, 198 5 Tanner, W and Caspari, T., Membrane transport carriers, Annu Rev Plant Physiol Plant Mol Biol 47, 595–626, 199 6 Tolgyesi,... Press LLC 336 Environmental Sampling and Analysis for Metals Although the chemical composition of the DNA molecule was known before 190 0, it was not until 195 3 that the organization of the chemical subunits was modeled by James Watson and Francis Crick Structural characteristics of this model of DNA molecules are summarized below: 1 The molecule consists of two strands with crossbars The strands twist... halogen considered to be essential for photosynthesis of higher plants.) Uncertain role: Vanadium, chromium, nickel, strontium, and aluminum Mostly toxic: Arsenic, cadmium, and lead MOST IMPORTANT METALS The most important metals in plant physiology are briefly described below 323 © 2002 by CRC Press LLC 324 Environmental Sampling and Analysis for Metals POTASSIUM Form of uptake: ion Role: enzyme activation,... Environmental Sampling and Analysis for Metals FIGURE B.1 Schematic drawing of silicon semiconductor crystal layers (From World of Chemistry, 1st ed., by M.D Joesten, D.O Johnston, J.T Netterville, J.L Wood © 199 0 Reprinted with permission of Brooks/Cole, an imprint of the Wadsworth Group, a division of Thomson Learning Fax 800 73 0-2 215.) enter the upper, normally empty conduction band of silicon and. .. agricultural practices (Salisbury and Ross, 199 2; Lea and Leegood, 199 3) © 2002 by CRC Press LLC Appendix D: Metals and Plants 327 Metals dissolved in water and available for uptake get into the vascular tissue system of the root as ions or complexes via root hairs The type of movement of substances dissolved in water can be classified as short, medium length, or long distance Short-distance metal transport... microprocessor chip, for example, can provide a machine with decision-making ability, memory for instructions, and self-adjusting controls In everyday life, we see many examples of chip applications: digital watches; microwave oven controls; hand calculators; electronic cash registers for calculating total bills, posting sales, and updating inventories; and computers in a variety of sizes and capacity SOLAR... (CrO3) in reagent-grade water, acidify with HNO3, and dilute to 1 liter (1000 mg/l) 341 © 2002 by CRC Press LLC 342 Environmental Sampling and Analysis for Metals Chromium Hexavalent (Cr6+) Dissolve 0.2829 g of pure dried potassium dichromate (K2Cr2O7) and dilute to 1000 ml with reagentgrade water (1 ml = 100 µg Cr) Cobalt (Co) Dissolve 1.000 g of cobalt metal in 20 ml of 1:1 HNO3 and dilute to 1 liter... reagent-grade water, or 4.307 g of cobaltous chloride (CoCl2.6H2O), and dissolve in reagent-grade water Add 10 ml of concentrated HNO3 and dilute to 1 liter with reagent-grade water (1000 mg/l) Copper (Cu) Dissolve 1.000 g of electrolytic copper in 5 ml of HNO3 and dilute to 1 liter with reagent-grade water (1000 mg/l) Iron (Fe) Dissolve 1.000 g of analytical-grade iron wire in 10 ml of HNO3 and reagent-grade . Matter and Its Changes, John Wiley & Sons, New York, 199 3. A Concise Dictionary of Chemistry, 2nd ed., Oxford University Press, Oxford, 199 0. Csuros, M., Environmental Sampling and Analysis for. Press LLC 310 Environmental Sampling and Analysis for Metals 19. 2.2 HAZARDOUS PROPERTIES OF COMPRESSED GASES The properties of a compressed gas must be well known and understood before the gas. LLC 318 Environmental Sampling and Analysis for Metals enter the upper, normally empty conduction band of silicon and allow the solid to conduct. This type of material is called an n-type semiconductor