Effect of Bromide and Iodide on Chloride M ethodologies in Plasma or Serum*f

Size: px

Start display at page:

Download "Effect of Bromide and Iodide on Chloride M ethodologies in Plasma or Serum*f"

Suzan Cannon
6 years ago
Views:

1 ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 10, No. 6 Copyright 1980, Institute for Clinical Science, Inc. Effect of Bromide and Iodide on Chloride M ethodologies in Plasma or Serum*f C A TH ERIN E BAKER, P h,d., STEPH E N E. KAHN, P h.d., and EDW ARD W. BERM ES, Jr., Ph.D. Departments o f Pathology and Biochemistry and Biophysics, Loyola University Medical Center, Maywood, IL ABSTRACT T he effect of adding know n am ounts of brom ide and iodide to a plasm a pool on several m ethodologies for m easuring chloride ion has b een studied. M ethods ev alu ated w ere coulom etric, colorim etric, and ion-specific e lectrode. T hree different types of electrodes w ere evaluated in order to assess any im provem ents w hich m ight have b e e n m ade in recent years. T he older electrode m ethodology show ed an extrem ely large positive error in apparent chloride ion concentration in p resence of very sm all am ounts of brom ide and iodide. Also, th ere was a delayed return to norm al response by this electrode after exposure to brom ide or iodide. Both of these problem s have essentially b een elim inated by the n ew er electrodes w hich show responses to added brom ide or iodide w hich are sim ilar to the coulom etric and colorim etric m ethods. Introduction It is know n that brom ide and iodide can be encountered in the plasm a of certain individuals and that the presence of these h a lo g e n s can c a u se in te rfe re n c e s in chloride ion analyses. Brom ide ion is used occasionally as a hypnotic or sedative and th erapeu tic levels of 10 mm can com m only b e ex p ected. E xcessive io d id e levels can arise from various sources: adm in istratio n of inorganic io d id e or of io d in e -c o n ta in in g m e d ic a tio n s to th e open w ounds of b u rn patients. In this study, a plasm a pool was spiked w ith varying am ounts of sodium brom ide or sodium iodide. T h e chloride ion conc e n tra tio n w as th e n d e te rm in e d by coulom etric, colorim etric and ion specific electrode m ethods to determ ine the effect o f brom ide and iodide on each. T h eo retical C onsiderations * Supported in part by a NIH Research Training Grant in Clinical Chemistry 5 TOI GM f Reprint requests should be sent to Edward W. Bermes, Jr., Ph.D. T ietz4 lists the definitive m ethods for chloride ion determ ination as neutron activation analysis or coulom etry w ith an /80/ $00.90 Institute for Clinical Science, Inc.

524 BAKER, KAHN AND BERM ES am perom etric detection of th e end-point. T h e reference m ethod is titration w ith silver nitrate using am perom etric d etection of the en d point.

2 524 BAKER, KAHN AND BERM ES am perom etric detection of th e end-point. T h e reference m ethod is titration w ith silver nitrate using am perom etric d etection of the en d point. In this study, the effect of brom ide and iodide on apparent p la sm a c h lo rid e c o n c e n tra tio n w as ev a lu a ted u sin g one o f th e d efin itiv e m eth o d s (coulo m etry ), a co lo rim etric m ethod, and three ion specific electrode m ethodologies. Brom ide and iodide interferences are know n to be especially significant w hen chloride ion concentrations are m easured w ith an ion specific electrode. In order to assess im provem ents w hich have b een m ade in electrode m ethodology over the past few years, three different solid state chloride-specific electrode system s w ere evaluated for the effect of added brom ide and iodide on the apparent chloride ion concentration. B ecause chloride-specific electro d es have a selectivity coefficient for brom ide and iodide w hich is m uch greater than one, presence of small am ounts of these halogens in th e blood lead to large positive errors in apparent chloride ion con- centration.1,5 A num b er of different approaches have b e e n u sed to elim inate th ese in terfe ren c es from b ro m id e and iodide. T he solid state chloride electrode system d eveloped for the Stat/Lyte* incorporates use of a dialysis m em brane to e lim in a te p ro te in in te rfe re n c e s. T h e specim en is dialyzed into a recip ien t solution containing ethylene diam ine tetraacetic acid (E D T A ) an d m ercury (II) nitrate. T he reference electrode is a silversilver chloride w ire past w hich a solution of 0.1M KC1 flows. A liquid junction is form ed by sam ple and reference streams flowing together from opposite directions. Sam ples are run at constant ionic strength so that the instrum ent may be calibrated to read co n cen tratio n d irectly in stead of activity.3 T he Stat/Lyte is no longer in production; how ever, the C 800, a new electrolyte analyzer,* em ploys the same electrode system. T he Stat/Ion* PVA-4f also uses a solid state chloride-specific electrode and is calibrated at constant ionic strength. A double-ju nction calom el referen ce electrode is em ployed to m inim ize the effect of the changing liquid junction potential w hich may occur from sam ple to sample. T he new er chloride electrode produced f for this in stru m e n t em ploys a surface m o d ific a tio n w h ic h is p u rp o rte d to m inim ize interferences from brom ide and iodide.2 In all other aspects, this electrode is identical to earlier versions produced.! One of these older electrodes was also evaluated. M aterials TOTAL CONC. OF HALIDE IN M M O L /L (AMOUNT OF BROMIDE ADDED IN M M O L /L ) F ig u r e 1. Response of coulometric (X) and colorimetric ( ) methodologies to a plasma pool spiked with sodium bromide. (O = Theoretical response). (Numbers in parenthesis on the X-axis represent the amount of bromide added.) C oulom etric analyses w ere perform ed u sin g an A m inco$ C h lo rid e T itra to r stan d ard iz ed w ith H arleco C h lo rid e S tandard (100 mm, Cat. No ). * Technicon, Tarryton, NY. f Photo volt, New York, NY. { A m erican In stru m en t C om pany, S ilver Spring, MD. Harleco, Gibbstown, MJ.

E F F E C T O F BR AND I ON C H L O R ID E M ETHODS 5 2 5 C olorim etric analyses w ere m ade with an In s tru m e n ta tio n L ab o rato ry 446 C h lo rid e/t o ta l C 0 2 analyzer.

3 E F F E C T O F BR AND I ON C H L O R ID E M ETHODS C olorim etric analyses w ere m ade with an In s tru m e n ta tio n L ab o rato ry 446 C h lo rid e/t o ta l C 0 2 analyzer. T h e in strum ent was calibrated w ith solutions containing 100 mm and 80 mm chloride using IL Auto Cal I (Cat. No ) and Cal 2 (Cat. No ), respectively. C hloride m easurem ents by ion specific electrode w ere m ade using th ree different sy stem s. In s tru m e n ts u s e d w e re th e Stat/Lyte* and the Stat/Ion.* This latter instrum ent was eq u ip p ed w ith two differen t chloride specific electrodes for this study. T he first was an older T echnicon electrode (Cat. No. 138-B046-01) and the second was a n ew er Photovolt electrode (Cat. No ). T h e electrodes currently available for this instrum ent are sold u n d er these catalog num bers by both T echnicon an d Photovolt. T h ese electrodes are all m ade by Photovolt and are th e n ew er kind. T he n ew er and older e le c tro d e s a re, o f c o u rse, in te r changeable. M ethod A brom ide- and iodide-free plasm a pool was spiked w ith eith er N al or NaBr in v ary in g am o u n ts. A ll sam p le s w e re analyzed using the various instrum ents according to the instructions of the m anufacturers. All sam ples w ere run in duplicate on the Aminco C oulom eter and the IL 446 C hloride/t otal C 0 2 Analyzer. Results p resen ted are the m ean of the duplic a te d e te rm in a tio n s. S in ce th e ion specific electro d e m ethodologies have b een dem onstrated to b e subject to a decided carry-over effect as a result of exposu re to sm all am o u n ts o f io d id e or brom ide, the sam ples w ere run in triplicate from low to high concentration of brom ide or iodide in order to dim inish any carry-over effects of the electrode surface. Results are reported as a m ean of the triplicate values. In order to assess the recovery of the three types of chloride specific electrode w h en ex posed to h ig h concentrations o f TABLE I Linear Regression Data for Determination of Chloride in the Presence of Bromide in a Plasma Pool Method Slope r Theoretical response Coulometric Colorimetric Technicon electrode (old) Photovolt electrode (new) Stat/Lyte brom ide or iodide, a spiked pool at high concentration was run and was follow ed im m ediately by unspiked pool. T he unspiked pool was th en run in succession on the instrum ent in question until the base line chloride value had b een reachieved. R esults and D iscussion T h e c o u lo m e tric an d c o lo rim e tric m ethods both provided good lin ear response to added brom ide or iodide. In figu re 1, th e re s p o n se s o f th e s e tw o m ethodologies to added brom ide can be seen. T h e colorim etric m etho d gave re sults slightly clo ser to th eo retical or expected values for total halogen content than th e coulom etric procedure. In table I are sum m arized the slopes for th e re sponse curves o f the coulom etric and colorim etric m ethodologies to th e spiked plasm a pool as determ ined by linear regression analysis. A slope of 1.74 was obtained for the coulom etric procedure and 1.38 for the colorim etric m ethod. T he TABLE I I Linear Regression Data for Determination of Chloride in the Presence of Iodide in a Plasma Pool Method Slope r Theoretical response Coulometric Colorimetric Technicon electrode (old) Photovolt electrode (new) Stat/Lyte

4 5 2 6 BAKER, KAHN AND BERM ES T O T A L C O N C. O F H A L ID E IN M M O L / L ( A M O U N T O F B R O M ID E A D D E D IN M M O L / L ) F ig u r e 2. Response of chloride selective electrodes to a plasma pool spiked with sodium bromide. (A) Stat/Lyte; ( ) Newer Photovolt electrode; (X) Older Technicon electrode; (O = Theoretical response). (Numbers in parenthesis on the X-axis represent the amount of bromide added.) T O T A L C O N C. O F H A L ID E IN M M O L / L (A M O U N T O F IO D ID E A D D E D IN M M O L / L ) F ig u r e 3. Response of chloride selective electrodes to a plasma pool spiked with sodium iodide. (A) Stat/Lyte; ( ) N ewer Photovolt electrode; (X) O lder Technicon electrode. (O = Theoretical response). (Numbers in parenthesis on the X-axis represent the amount of iodide added.) coulom etric m ethod is thus seen to give alm ost a tw o-fold increase in ap p aren t chloride on concentration for the am ount o f b ro m id e a d d e d. T h e c o lo rim e tric m ethod is som ew hat better. In table II, the slopes for the response curves of the coulom etric and colorim etric m ethodologies to a plasm a pool spiked w ith iodide are p resen ted as determ ined by linear regression analysis. In the case of added iodide, the coulom etric response is essentially coincident w ith the theoretical lin e. T h e co lo rim eteric re sp o n se shows alm ost a two-fold change in total h alo g en co n c en tratio n com pared w ith w hat w ould b e expected from the am ount of iodide added. T he shapes of the curves are essentially the same as those for the response to brom ide as seen in figure 1. O f m ajor in te re st in perform ing this study was the determ ination of the response of the various chloride selective electrode m ethodologies to the presence of brom ide and iodide. A discussion of th e se m eth o d s and how b ro m id e and iodide interferences have b een dealt w ith by the in strum ent m anufacturers has b een g iv e n in th e s e c tio n on th e o re tic a l considerations. In figure 2, the response of the three electrodes to a plasm a pool spiked w ith sodium brom ide can be seen. T he older type of Stat/Ion electrode show ed an extrem ely high selectivity for brom ide over chloride. W hen th e brom ide concentration was 2 mm, the apparent chloride ion concentration was increased by 40 mm. T his is indicative of a 20-fold am plification. T h e surface-treated Photovolt e lectrode and the continuous flow Stat/Lyte system b o th sh o w ed ap p ro x im ately a two-fold am plification in the detection of brom ide. T his represents a considerable im provem ent over the response of the older type of electrode to added brom ide. In table I is given the linear regression analysis o f th e resp o n se of th e th ree ch lo rid e specific electro d e system s to brom ide.

5 E F F E C T O F BR AND I ON C H L O R ID E M ETH O D S 527 TABLE I I I Recovery of Chloride-selective Electrodes After Exposure to 5.0 mm Sodium Bromide in Plasma Instrument (mmol/1 Photovolt Electrode Response Cl~) Stat/Lyte Initial reading (± S.E.M.) (± S.E.M.) (unspiked pool) 84 (± 1) 83 (± 1) Spiked sample 90 (± 2) 107 (± 2) Successive readings 95 (± 1) 80 (± 2) of unspiked 84 (± 1) 82 (± 1) samples 84 <± 1) 82 (± 1) 84 (± 1) 83 (± 1) Results w h en a plasm a pool was spiked w ith iodide are sum m arized in figure 3. Again, the o ld er type o f chloride electrode show ed a m arked increase in apparent chloride ion concentration in presence of o n ly a sm all a m o u n t o f io d id e. T h e am plification of iodide ion concentration is approxim ately four-fold for this e lectrode. T he Photovolt electrode and the Stat/Lyte system offer com parable results w ith the Photovolt electrode having the closest approach to the ideal or theoretical respo nse (see tab le II). A nother problem w hich can be encounte re d w ith th e a u to m ate d analysis of chloride by an ion specific electrode is the slow ness o f th e re tu rn to a norm al response after exposure to a specim en containing eith er brom ide or iodide. In table III is sum m arized the return of two of the electrodes to norm al function after exposure to a plasm a pool containing 5 mm sodium brom ide. T he Photovolt electrode show ed an erroneously high value for chloride on the first unspiked specim en ru n im m ed iately after exposure to the brom ide. H ow ever, the second specim en show ed a return to the correct chloride read in g. T h is o ccurred ap p ro x im ately th ree m inutes after exposure to brom ide. T h e S tat/l y te system sh o w ed an im m ed iate retu rn to the correct ch lo rid e value. T he unspiked pool was analyzed approxim ately 1.5 m inutes after exposure to brom ide. In table IV are p resen ted the recovery results for the electrodes w hen exposed to 1 mm or 5 mm of sodium iodide. The S tat/l y te and th e P hotovolt electro d e show ed essentially no carry-over after exp o su re to io d id e. H ow ever, th e o ld er T echnicon electrode gave an erroneously low chloride reading for the first unspiked specim en run after exposure to the spiked specim en. T he n ew er ion specific m ethodologies (Stat/Lyte and Photo volt) have m ade considerable advances in the elim ination of interferences from brom ide and iodide w hen com pared w ith the older style of chloride specific electrode (Technicon). H ow ever, care m ust be taken w ith the n ew er Photovolt electrode. Since its im proved perform ance involves a surface m o d ificatio n, its surface m u st n o t b e TABLE IV Recovery of Chloride Selective Electrodes After Exposure to Sodium Iodide in Plasma Instrument Response (nmol/1 Cl") 1.0 m M/1 Nal 5.0 m / 1 Nal Technicon Photovolt Electrode Stat/Lyte Electrode Stat/Lyte Initial reading (± S.E.M.) (± S.E.M.) (± S.E.M.) (± S.E.M.) (unspiked pool) 101 (± 1) 80 (± 1) 84 (± 1) 84 (± 1) Spiked sample 122 (± 2) 81 (± 2) 90 (± 2) 100 (± 2) Successive readings 94 (± 1) 80 (± 1) 83 (± 1) 85 (± 1) of unspiked samples 99 (± 1) 80 (± 1) 85 (± 1) ' 85 (± 1) 100 (± 1) 81 (± 1) 84 (± 1) 83 (± 1) 101 (± 1) 80 (± 1) 84 (± 1) 83 (± 1)

6 5 2 8 BAKER, KAHN AND BERM ES cleaned by abrasion or the en d resu lt will be an electrode of the older style w ithout the surface m odification and w ith the poor response to brom ide and iodide. T he response o f th e se n e w e r electro d es ap proaches th e coulom etric an d colorim etric m ethods in th at all of th ese procedures appear to respond to total halogen in the p re sen ce of b ro m id e or io d id e in the plasma. Thus, the very large positive deviations show n by the older type of electrode have b een virtually elim inated at low b ro m id e or io d id e le v e ls an d m inim ized at high levels. R eferences 1. Ko l t h o f f, I. M. and Sa n d e r s, H. L.: Electrode potentials at crystal surfaces and at silver halide surfaces in particular. J. Amer. Chem. Soc. 59: , L e v y, G a b o R; Photovolt, New York, NY: Private communication, T e c h n ic o n M e t h o d No.: SR4-0049PJ8, released Septem ber T i e t z, N. W.: A model for a comprehensive m easurem ent system in clinical chem istry. Clin. Chem. 25: , W e n c h, R. E., L u s t g a r d e n, J. A., P a p p a s, N. J., L e v y, R. I., and Ja c k s o n, R.: Serum chloride analysis, brom ide detection and the diagnosis ofbfomism. Amer. J. Clin. Path. 65:49-57,1956. STATEMENT OF OWNERSHIP, MANAGEMENT AND CIRCULATION (Act of October 23, 1962; Section 4369, Title 39, United States Code) Date of Filing September 22, 1980 Title of Publication ANNALS O F CLINICAL AND LABORATORY SCIENCE Frequency of Issue Bimonthly Location of Known Office of Publication 230 N. Broad St., Philadelphia, PA Location of the Headquarters or General Business Offices of the Publisher Same as above Publisher Institute for Clinical Sciences, Inc. Editor F. William Sunderman, M.D., Ph.D. Managing Editor Same as above Owner Institute for Clinical Sciences, Inc. Known Bondholders, Mortgagees, and O ther Security Holders Owing or Holding 1 Percent or More of Total Amount of Bonds, Mortgages or Other Securities None Average No. Copies Each Issue During Preceding 12 Months Actual Number of Copies of Single Issue Published Nearest to Filing Date A. Total No. Copies Printed (Net Press Run) B. Paid Circulation 1. Sales Through Dealers and Carriers, Street Vendors and Counter Sales None None 2. Mail Subscriptions C. Total Paid Circulation D. Free Distribution by Mail, Carrier or O ther Means, Samples, Complimentary, and Other Free Copies None None E. Total Distribution (Sum o f C and D) F. Copies not Distributed 1. Office Use, Left-over, Unaccounted Spoiled After Printing Returns from News Agents None None G. Total (Sum o f E and F should equal net press run shown in A) I certify that the statements made by me are correct and complete F. WILLIAM SUNDERMAN, M.D., Ph.D.

C o r p o r a t e l i f e i n A n c i e n t I n d i a e x p r e s s e d i t s e l f

C H A P T E R I G E N E S I S A N D GROWTH OF G U IL D S C o r p o r a t e l i f e i n A n c i e n t I n d i a e x p r e s s e d i t s e l f i n a v a r i e t y o f f o r m s - s o c i a l, r e l i g i