A. J. Barnard, Jr. R. M. Mitchell G. E. Wolf
Report
Chemicals Division J. T. Baker Chemical Co. Phillipsburg, N.J. 08865
Good Analytical Practices in Quality Control In a real sense the concepts of good analytical practices in quality control predate by many years the present perceptions of regulatory compliance and consumerism. For more than 25 years each, the authors have been associated with the analytical challenges faced by the J. T. Baker Chemical Co. Good analytical practices have been a central concern of this company since its founding at the turn of this century. From the earliest years of the company, John Townsend Baker held that definitive labeling for chemicals should be and could be of benefit to the consumer. One outworking of that philosophy has been the provision of actual analytical values for each lot on the label, for many products, or by certificate. A further outworking has been the active participation of the technical staff throughout this century in the largely unpublicized efforts by standards groups to update industry and compendium analytical methods. The company's concern with sound analytical practices and procedures is magnified in two further ways: In recent years, J. T. Baker has offered about 3500 chemical products ranging in package sizes from milligrams to tons and tankwagons. Products include reagents and specialties for chemical, analytical, biochemical, and clinical laboratories; analytical standards; ultrapure compounds and reagents; food and prescription grade products; and synthetic drugs and intermediates manufactured under FDA guidelines. Another complication is one faced by more and more companies, namely, the need to undertake quality control at more than one location. At J. T. Baker, quality control involves four groups in as many buildings at the major plant in New Jersey, 0003-2700/78/A350-1079$01.00/0 © 1978 American Chemical Society
three groups at other locations in the United States, and laboratories associated with manufacturing operations in Mexico, Brazil, and the Netherlands. The intent is to be practical and to provide recommendations based on the long-term J. T. Baker experience with good analytical practices in quality control. Some of the observations are derivative and may be in the bag of tricks of many quality control groups. Some recommendations may be relatively new. Hopefully, all of the recommendations deserve close study.
Samples and Sampling Without a sample there can be no analysis. Without a suitable sample there should be no analysis. The analysis of inappropriate samples can be a waste of time and manpower! The establishment of adequate sampling techniques, procedures, and schedules is clearly a responsibility of the quality control organization. Where the sampling is not performed by members of that department, audits are appropriate to confirm that the established practices are being followed. Obviously, all samples should be adequately identified and placed in designated containers. Where samples do not meet the established standards for labeling and containment, they should not be accepted. The individual and department submitting them should be contacted. Two types of samples are commonly encountered: representative and extreme samples. A representative sample is intended to correspond to the average composition and properties of the related material and is the type of sample commonly analyzed in quality control. An extreme sample may
correspond to an extreme variation in the composition of the material of interest. An extreme sample, for example, is usually taken to assure the chemical and microbiological quality of water. The "critical" sample is secured not from the water treatment unit or storage tank, but rather from the most remote or the least used distribution line. A third sample type can be termed sequential or chronological samples. Such samples may be representative or extreme in nature, depending on the purposes at hand. Samples taken, for example, at stated intervals in a continuous operation may represent the composition of the material produced at, and around, that time. In a semicontinuous operation, samples may be taken at critical times, for example, when the operation is resumed after shutdowns. Analysis of those samples may reveal the "worst" situation as far as compositional variation, physical nonuniformity, or contamination. With powdered and granular materials, blenders and blender-dryers are widely used in the chemical and allied industries. In an experimental run, adequate blending conditions can often be established by sequential sampling and analysis of the samples for one or more critical parameters. In the blending of subsequent batches of the material under the conditions thus established, an economic approach is often to take three samples from the material discharged into the first and last drums and into a drum somewhere in the middle of the transfer. Depending on circumstances, the samples can be treated as extreme in nature and be separately analyzed, or a composite can be taken as representative of the total charge.
ANALYTICAL CHEMISTRY. VOL. 50, NO. 12, OCTOBER 1978 · 1079 A
Corrosives and solvents that may react with the container/closure sys tem in which they are ultimately sold present a special challenge to sampl ing and analysis. In some cases, the final lot analysis is best performed after the actual subdivision. For ex ample, the Ultrex high-purity acids are sold in sealed, preleached borosilicate ampules. For certification of each lot, sequential samples of the ampuled product are taken from the subdivi sion operation. These samples are al lowed to stand for at least five days at room temperature. By that time, any leaching of trace elements from the glass is virtually complete. The an alytical values based on analysis of those samples are representative of the acids as they are received by the customer (/). Physical Inspection and Physical Properties
Where priorities allow, in our view, once samples have reached the labora tory and have been logged, the initial efforts should be their physical exami nation and establishment of any com posite samples, as well as appropriate retention samples. In our experience, it is usually more economic to com plete the evaluation of physical prop erties before chemical analysis is un dertaken. As part of the physical inspection of powdered and granular materials, a "color" or "appearance" description must often be met, as set forth in an official compendium. It is imperative that such inspection be performed by trained observers under adequate, uniform lighting. Where doubt exists as to the acceptability of a given mate rial, reference and retained samples should be examined concurrently. Solution Color Index
In the visual assessment of the whiteness, or rather the "off-white
ness", of powdered and granular mate rials, considerable subjectivity is in volved. Where personnel disagree on the presence or absence of trace color in a material, preparation of a concen trated solution of the suspect material and reference samples may provide resolution. The solutions can be viewed directly or be compared with APHA platinum-cobalt color stan dards. Various laboratories have taken a photometric approach. The photo metric measurements can be made at one, two, or many wavelengths. At J. T. Baker, Joy (2) has formulated what he calls the Solution Color Index, which we have used to advantage. The situation existing in the ap pearance of a yellow color in the solu tion of a colorless solute is delineated in Figure 1. Increased absorption oc curs in the visible at short wave lengths, such as 420 nm, with little or no change in absorption at longer wavelengths, such as 620 nm. The in crease in the absorbance at 420 nm can be correlated with the visual ob servation of "yellowness". However, by measurement of the difference in the absorbance at the short and long wavelength, ΔΑ, partial compensation for any turbidity or pronounced light scattering is secured. To allow comparison of AA values obtained at different solution concen trations or different cell paths, the So lution Color Index (SCI) can be ap plied. This index is defined by S C I = AAX10^ cb Here ΔΑ is the difference in absorb ance of the solution of the colorless compound at the selected short and long wavelengths, c is the concentra tion of the solute in g/mL, and b is the cell path in cm. The factor 103 is se lected so that SCI values are not deci mal numbers (typically ΔΑ seldom ex ceeds 0.1 when c is 0.3-0.5 Mg/mL and b is 2-10 cm). The use of the Solution Color Index can be illustrated. In the manufacture of a colorless organic compound, on vi sual inspection of the first 11 lots, the majority of trained observers conclud ed that three of the lots had an unac ceptable, extremely faint yellow cast. The SCI values were determined for the 11 lots with the following findings: Visual appearance SCI values of lots Acceptable 16, 12, 12, 10, 6, 4, 2, 0 Unacceptable 82, 52, 52
Figure 1. Photometric increase in "yel lowness" of solution of colorless solute
On the basis of these results, the fol lowing SCI limits were adopted: ac ceptable, 0-20; borderline (for review), 20-50; unacceptable, >50. Against these guidelines, subsequent produc tion was rapidly screened, and a study initiated as to the frequency and source of the color.
1080 A · ANALYTICAL CHEMISTRY, VOL. 50, NO. 12. OCTOBER 1978
The photometric approach, typified by the Solution Color Index, can be recommended wherever the color de scription for a colorless, soluble mate rial must be quantified. Additionally, the technique can be of special value in studies of product stability and storage life. Reagents and Reagent Solutions
Reagents employed by quality con trol laboratories can be divided into solid organic and inorganic materials, mineral acids and aqueous ammonia, solvents, stock solutions, and standard solutions. Some laboratories mark each bottle of a purchased chemical with the date of receipt. This practice is probably unnecessary if excessive stocks are avoided, but may have merit for chemicals that can undergo deteriora tion or decomposition on long storage. It is noteworthy that at the present time many suppliers place advisory outdates on the labels of important re agents of limited stability, such as ether, hydrogen peroxide, and ammo nium persulfate. For organic solvents, it is reasonable to state that the grade most appropri ate to each intended use should be purchased. The cost of solvents, and reagents generally, is far less than manpower. The security gained by a performance-oriented product at a premium cost usually outweighs the risk of extra staff time for checks and reruns. Stock solutions of the reagents for frequently performed tests are re quired by most quality control labora tories. Small groups may elect to pur chase stock solutions (and standard solutions as well) from reliable ven dors. Large organizations often pre pare all or many of the solutions re quired. In our experience, the respon sibilities for the preparation of both stock and standard solutions should be assigned to one or more welltrained staff members. The solutions, so prepared, are distributed as needed to relevant benches and laboratories at the installation. Each bottle should carry a well-affixed label providing a brief description of the nature and concentration of the contained solu tion and, where important, a summary of the preparation directions. Addi tionally, the label should carry a date and identification number that allows the solution to be traced to the analyt ical record for its preparation. In our practice, the record for each stock and standard solution is entered into a single log book. A sequence number from 1 through 99 is assigned that is followed by the numeric ex pression of the date of preparation. For example, if the fourth solution in the sequence were prepared on Janu-
Table I. Frequently Used Volumetric Solutions Solute
NH4SCN EDTA, di-Na HCI >2
HCIO4 in HOAc KMn0 4 AgN0 3 NaOH Na 2 S 2 0 3 H 2 S0 4
Strength
Standardization • '
Check
0.1 Ν 0.1 M 0.1 Ν 1 Ν 0.1 Ν 0.1 Ν 0.1 Ν 0.1 Ν 0.1 Ν 1 Ν 0.1 Ν 1 Ν
0.1 Ν AgN03(Fe"') Μη (Eriochrome Black T) Na 2 C0 3 (methyl orange)
0.1 A/l 2 Bi (Xylenol Orange) 0.1 /VNaOH 1 /VNaOH 0.1 /VNa 2 S 2 0 3
As 2 0 3 (iodometry) KHP (crystal violet) Na 2 C 2 0 4 As AgCI (gravimetry) KHP (phenolphthalein) K 2 Cr 2 0 7 (iodometry) Na 2 C0 3 (methyl red)
0.1 0.1 0.1 1 0.1 1
NNa 2 S 2 0 3 Ν HCI Λ/HCI /VHCI Λ/Ι 2 Ν NaOH
* Standards NBS SRM quality, except reagent grade Mn and Bi. acid washed.
ary 5, 1977, the code number to ap pear on labels and in the log book takes the form 4010577. Additionally, for any test performed with that solu tion, the analytical record would in clude that number. In our experience, central preparation of solutions cou pled with a system of date-readable identification numbers can aid in re ducing disagreement in results by dif ferent analysts and laboratories and certainly improves traceability. Addi tionally, by date coding the age of a solution is immediately discernible.
Standards and Standard Solutions Our involvement with standards and standard solutions is far more ex tensive than most analytical groups in industry. This is not unexpected be cause of the offering by J. T. Baker of titrimetric standards, high-purity compounds provided with precision assays, ionic and volumetric concen trates, and prepared volumetric solu tions. For most titrimetric procedures, in our quality control laboratories cen trally prepared standardized solutions are employed as described above. Table I highlights some of the volu metric solutions that are commonly prepared in quantities of 5-20 gal at a time. T h e table also indicates the method of standardization. In most cases the strength is traceable to N B S Standard Reference Materials. Com monly, each batch of a standard solu tion is also compared with a batch of second solution earlier introduced, as indicated in the table. For volumetric solutions of limited stability, only suf ficient quantities are prepared for use within the assigned shelf life—usually 15 days. In precision assay work, such as is required in t h e assessment of titrimet ric standards and high-purity com pounds, we often employ weight titra tions to an instrumental endpoint. Volume-based titrations under favor able conditions and with use of repli
cates can provide a reliability ap proaching one part in one thousand. In contrast, weight titrations can pro vide precision and accuracy better than one part in five thousand. A dif ference approach is commonly prac ticed. In the simple case, to a weighed amount of the chemical to be assayed is added a reagent of unambiguous pu rity in a weighed amount either slight ly less or more than that required for equivalence. T h e small departure from stoichiometry is then measured by a volume-based titration. As the ti trant, a dilute solution of the chemical being assayed or the comparison re agent is used. Where an acid-base ti tration is involved, the end point can be based on the second difference of p H values with constant increments of titrant added. In our laboratories, weight titrations to a photometric end point have proved useful in the assess ment of high-purity EDTA and some metal salts (3). A one-weight-formal hydrochloric
acid is used in our high-purity chemi cals program for the precision titri metric assay of many acidic and basic compounds. We prefer to standardize this solution by the precision gravi metric determination of chloride as silver chloride developed by Little in our laboratories (4). Excellent agree ment is secured by this approach and the use of NBS Standard Reference Material tris and potassium biphthalate (5). T h e above discussion has centered on titrimetric standards. Many other types of standards are employed in quality control organizations. T h e best practice, in our view, is to have all standards logged by designated staff members and to have date-readable identification numbers assigned. T h e procurement and introduction of stan dards are thereby under unified con trol.
Instruments Instrumental techniques are finding ever-increasing application in quality control. Improved accuracy, increased sensitivity and selectivity, and re duced staff time are often secured. In some cases, the desired information could not be secured other than by in strumental methods. For reliable re sults, an instrument must be used by an adequately trained operator using established operating procedures. Where the performance and calibra tion of an instrument are not verified with its regular use, checks should be performed at appropriate intervals by stated procedures using stated stan dards. T h e check data are best made a part of permanent records. T h e date and initials of the staff member in volved should be entered on a log sheet maintained with the unit. The frequency of calibration and
Table II. Calibration Checks for Instruments Instrument
Calibration frequency
pH meter Melting point instruments
Hourly or daily Monthly
Specific gravity balance UV/VIS spectrophotometer
Monthly Monthly
IR spectrophotometer Liquid scintillation spectrometer Analytical balance Refractometer Spectrofluorometer Gas chromatograph
Quarterly Quarterly
1082 A · ANALYTICAL CHEMISTRY. VOL. 50, NO. 12. OCTOBER 1978
Semiannually Semiannually Semiannually Dependent on column usage
Approach taken
pH4, 7, and 10 buffers Melting point reference standards NaCI solution Absorbance: acid dichromate . and Co ammonium sulfate solutions and NBS mixed metal standards. Wavelength: holmium oxide (Hg lamp) Polyethylene standard Sealed-in glass radiation standards Check weights (see text) Glass "test piece" Fluorescence standards Resolution of test mixtures and reference samples
Table III. Some "Common" General Tests Acidity Alkalinity Ammonium Chloride (halide) Chlorinated compounds Clarity Color Heavy metals Insoluble matter
Iodine-consuming substances Iron Lead Loss on drying (or heating) Neutrality Nitrate Nitrogen compounds pH of solution Phosphate
the rigor of t h e approach taken will depend on the type of instrument, its design and model, and the reliability required. Table II summarizes our thinking as far as some common instruments used in quality control laboratories. Analytical balances, in our longheld view, should be checked a t least twice each year. For each balance we maintain a file card on which are recorded t h e purchase date, type, serial number, and vendor. Additionally, the location of t h e balance is noted, whether in quality control, research and development, plant engineering laboratories, etc. Once each year every balance is serviced by a qualified balance specialist under contract. This specialist services and checks t h e performance of each balance against NBS-certified masses and applies a sticker giving t h e service date, serial number, next service date, and his signature. Any replacement of parts or unusual repairs is noted on the file card for t h e relevant balance. Six months later a staff member examines each balance for zero point and scale deflection and makes any necessary adjustment. Additionally, the balance performance is checked against NBScertified masses. T h e findings are recorded in a log book maintained for that purpose.
Phosphorus compounds Residue after evaporation Residue after ignition (ash) Solubility Substances precipitated by NH4OH Sulfate Sulfur compounds Water
was run, and the water used was too high in chloride content. In t h e J. T . Baker staff efforts toward the characterization of highpurity compounds, we have often been able to improve t h e detection limit of many general tests by the use of larger samples than conventional or greater concentration, attention to t h e blank, and substitution of instrumental for visual detection (3,6). B. H. Campbell and L. G. Hallquist of t h e Baker staff have recently completed a restudy of determinate and indeterminate errors associated with the classical "residue on evaporation" test widely used for t h e assessment of solvents and volatile organic liquids (7). T h e findings indicate t h a t where specifications of 5 ppm or less must be met, it is imperative to perform t h e evaporation under "clean air" conditions. Evaporation of 200 g of a solvent in an open dish in a conventional fume hood can yield a residue as large as 6 mg due to t h e entry of airborne particulate matter. "Clean air" conditions for evaporations can be obtained inexpensively in any laboratory by use of the Thiers assembly (8), pictured in Figure 2. By use of 200-g samples, a dish fashioned from aluminum foil, a semimicrobalance, and t h e Thiers assembly, residue after evaporation values as low as 0.4 p p m (Mg/g) can be reported.
might use a procedure and, additionally, the laboratories of customers that utilize our methods. To meet this type of challenge many companies have adopted programs for the distribution of samples that are then analyzed by different analysts and laboratories. At J. T. Baker, we employ what we call the ARM program, where the acronym stands for analytical reference material(s). What we do is to segregate a substantial quantity of a key product and assign an ARM number. A powdered or granular material is subjected to persistent blending to assure a high degree of uniformity. Usually the material is then subdivided into convenient size samples. In some cases, material is selected that fails product specifications for one or more parameters. We have used these ARM's in various ways. We have dispatched some ARM's to all our laboratories (and in some cases to cooperating laboratories outside our company) and requested total analysis. A confidential code letter is assigned to each laboratory for that sample. Each laboratory receives a copy of the latest edition of the relevant procedures and full instructions for reporting all results. Where any detail of a procedure is not followed, this is to be reported. When the results are received, and a highly divergent value is reported by a particular laboratory, it is requested to repeat that determination. In some cases, the samples are also analyzed by more exacting referee methods, notably, for assay, and often survey emission spectrograph^ is performed. Eventually the tabulation of all results is returned to all of the cooperating laboratories with a detailed critique. This approach has been of great help in assessing the true degree of reproduc-
General Tests In most quality control laboratories a significant portion of the total analytical effort involves t h e conduct of so-called general tests. Some of t h e more common of such tests for t h e chemical industry are listed in Table III. Many of these tests are relatively uncomplicated; however, unreliable findings may be secured if t h e analyst is inadequately trained or is inattentive to t h e nuances of the written directions. For example, for t h e turbidity determination of chloride by t h e formation of insoluble silver chloride, incorrect results can often be traced to one or t h e other of two analyst shortcomings: Either beakers, tubes, and filter paper used were not rinsed to free them of trace chloride or no blank
Evaluation of Procedures and Staff Proficiency Quality control demands a harmony of procedures and people. An analytical procedure, as used, can be one drafted by t h e staff of t h e department, be present in a compendium, or be abstracted from original literature. Regardless of its origin, t h e written procedure must be followed by analysts of different degrees of experience and training and with different perceptions of small details. Where a high degree of reproducibility is sought for an analytical procedure, difficulties mount as the number of analysts and laboratories involved increase. As many as 30-60 analysts within t h e Baker organization a t six installations
Figure 2. Thiers assembly
ANALYTICAL CHEMISTRY, VOL. 50, NO. 12, OCTOBER 1978 · 1063 A
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T h e writing, editing, and distribu tion of analytical procedures within a quality control organization is a topic beyond the scope of this paper. A few remarks, however, are appropriate. Over the past quarter century, the or ientation of analysis toward analytical procedures has changed markedly. Formerly, the simple instruction " . . . and filter" was sufficient to assure ad equate performance. Today, extensive directions as to the conduct of a pre cipitation and filtration would be in cluded in a procedure. In our view this trend of ever increasing the operation al details in procedures can be offset, at least partially, by two measures: The first is persistent in-house training of analysts. T h e second is use of detailed general procedures, anno tated as necessary, for frequently used methods. In the use of a short specific procedure, the analyst unfamiliar with the operation and techniques involved is directed to the general procedure; the fully trained analyst needs only the details summarized in the specific procedure. Many compendia are pro gressively adopting this latter ap proach. Contamination Control In Trace Analysis
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With the increasing interest in the trace and ultratrace components of many products of the chemical and al lied industries, quality control organi zations are becoming involved in ul tratrace analysis, both organic and in organic. In such efforts, contamination control is a major concern. At J. T. Baker we have now completed a full decade of facing challenges in the preparation, characterization, and containment of compounds of extreme purity. Our programs were initially catalyzed by the special reagents re quired for the analysis of the Apollo lunar samples, by the international needs for standards, and by the strin
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1084 A · ANALYTICAL CHEMISTRY, VOL. 50, NO. 12, OCTOBER 1978
gent requirements of some advanced technologies. M. Zief of the Baker staff and J. Mitchell of Bell Laborato ries have recently published a mono graph directed to contamination con trol in trace analysis (9). T h a t work imparts much of the practical ap proaches t h a t have evolved in these two organizations. In this paper, the remarks will be confined to measures that can be taken to reduce or to obviate contami nation by airborne particulate matter. It should be recognized, however, t h a t the selection and purification of re agents, the cleanup of apparatus, and the selection of analytical techniques and methods are equally important topics. In our experience, it is possible to reduce the level of airborne particu lates by maintenance of a laboratory room under positive air pressure cou pled with simple filtration of air enter ing through ventilation, air condi tioning, and heating systems. A filter unit is installed over each air supply louver. This unit consists of a stainless steel holder, a plastic grid, and a pleated glass wool filter having 8 5 95% efficiency for the removal of par ticles larger than 0.5 μπι in diameter. T h e area of the filter is made substan tially larger than that of the louver; consequently, little or no back pres sure develops. T h e cost of a holder is less than $350, and the inexpensive fil ters can be readily replaced yearly, or earlier if inspection suggests this is necessary. Further improvement can be achieved by the introduction of posi tive-pressure vertical laminar-flow clean air chambers having so-called high-efficiency particulate air (HEPA) filters. Such filters can remove at least 99.97% of particles above 0.3 μπι in di ameter. By the action of a fan, air passes from the room through a prefilter, then through the HEPA filter, and finally on to the working surface. Commercial chambers of the design, providing a work area of 2 by 2 ft, can be placed on top of an existing labora tory bench and cost less than $700. Such chambers are appropriate for many analytical operations, including weighing, dissolution of samples, pre cipitation, filtrations, and solvent ex traction. For some operations where only a small opening is required, such as weighing and transfer of samples to spectrographic electrodes, clean air chambers with H E P A filters and an elongated port are appropriate and cost less than $500. For extensive work, large bench top laminar flow work stations can be in stalled; however, their costs are high er. Where the operations involve nox-
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Pharmaceuticals Analysis of Pharmaceutical Products Quality control, drug metabolism studies, prepara tive separations, and drug stability studies are impor tant separation and quantitation tasks that can be effectively com pleted by LC. CIRCLE 239 ON READER SERVICE CARD
Obtaining Kilos of Pure Compounds Pharmaceutical chemists use pre parative LC to purify enantiomer intermediates. On ly 5% of the time previously requir ed by open col umn chromatogra phy was needed.
ious or toxic fumes, use of a vertical laminar flow chamber or work station is not feasible since the fumes would be dispersed into the laboratory. The simplest approach is the use of the Thiers assembly (Figure 2) to conduct evaporations and preashings, and some wet digestions. This device is im provised from a Petri dish and a crys tallizing dish to which a side arm is at tached. By passage of a gas through a membrane filter into the side arm, the sample preparation is maintained in a clean-gas environment. Heat can be supplied from below by a hot plate and from above by infrared radiation. For more extensive work involving fumes, balanced laminar flow fume hoods can be installed. Remarks Six score and more years ago, the quality control function had its feeble beginnings in the chemical and infant pharmaceutical industries. In quality control the challenges over the years have been substantial and diverse. In recent years two phenomena are note worthy. The responsibilities of quality control departments have mush roomed, and the positioning of quality control in corporate management has become higher. The reasons are multi ple and a few can be delineated: the desire for parity or advantage in the market place; the needs for high-per formance products; the consumerism age requirement t h a t product repre sentations be met regularly and faith fully; the obligations of regulatory compliance, whether food, drug, safe
ty, transportation, or environmental protection; and finally the ever-in creasing cost of rework or salvage of unacceptable products. Mark Twain observed t h a t a rab bit's foot is not a substitute for com mon sense. T h e current scene in quali ty control does not allow rabbit's foot thinking. Common sense demands that good analytical practices be rec ognized, be adopted, and be persisted
References (1) N. A. Kershner, E. F. Joy, and A. J. Barnard, Jr., Appl. Spectrosc, 25, 542-9 (1971). (2) R. F. Joy, unpublished work. (3) A. J. Barnard, Jr., R. F. Joy, K. Little, and J. D. Brooks, Talanta, 27, 785-7 (1970). (4) Κ. Little, ibid., 18,927-9(1971). (5) K. Little, unpublished work. (6) A. J. Barnard, Jr., and E. F. Joy, Chemist {New York), 47, 24:} -8 (1970); A. J. Barnard, Jr.. "High-Purity Chemi cals—A Challenge to Practical Analysis", in "Ultrapurity: Methods and Tech niques", M. Zief and R. Speights, Eds., pp 4I3-M), Dekker, New York, 1972. (7) B. H. Campbell and L. G. Hallquist, Anal. Chem., 50, 96.'!-4 (1978). (8) R. R. Thiers, in "Methods of Biochemi cal Analysis", F. Click, Ed., Vol 5, pp 273-335, Wiley-Interscience, New York, 1967; R. E. Thiers, in "Trace Analysis", J. H. Yoe and H. J. Koch, Jr., Eds.", pp 637-66, Wiley, New York, 1957. (9) M. Zief and J. W. Mitchell, "Contami nation Control in Trace Rlement Analy sis", 262 pp, Wiley-Interscience, New York, 1976. Presented al the Eastern Analytical Symposium, New York City. Nov. 1977.
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A. J. Barnard, Jr. (right), is director for research & development, J. T. Baker Chemical Co. His long-term interests include trace analysis and the character ization of special-purity materials. G. E. Wolf (center) is manager of quality standards. In this position he focuses on analytical procedures for product con trol and represents J. T. Baker on various industry and national standards groups. R. M. Mitchell (left) is currently coordinator for G M P and environ mental affairs. His post includes responsibilities for staff training in good manu facturing, laboratory, and analytical practices.
1086 A · ANALYTICAL CHEMISTRY, VOL. 50, NO. 12, OCTOBER 1978
