__
ecc. PROTEIN e
A
4
PROTEIN A N D DNA
0.240 a - HISTONE
0.220 E 0.200 0 0.180
g
$
0.160
z a
0.140
g 2
0.100
m
a
0.120
0.080
LITERATURE CITED
0.060
0.040 0.020 0.025
0.050 0.075 0.100 PROTEIN GONG. ( m g / m l ) Figure 2. Color development of protamine and histone with the Folin-Lowry reagent in the presence and absence of DNA
0
prior to analysis. Gel filtration may be used to remove phenol from D Y d (6) isolated by the Kirby aqueous phenol method (41, and this process has been s h o m t o remore bases, nucleosides, nucleotides, and low molecular weight oligonucleotides (5,8). The extreme sensitivity of the FolinLowry assay to the presence of guanine and its ribo- derivatives suggests that it might also be considered as a means for following certain hydrolytic reactions in which these derivatives are released from nucleic acids as reaction products.
0.0IO
development, this depression is not sufficient to invalidate the quant,itative as1)ectb of this assay. Quantities of protamine and histone c n the order of 10 to 15 pg. per nig. of DKd may be readily detected under these 1:onditions. Dat'a obt,ained during the course of this inre,stigation suggest that the FolinLowry prot'ein assay m a r be used for determining the degree of protein cont,xmiriation during the course of D S - i
isolation and purification, assuming that the color yield of the contaminating protein be known. This situation will be encountered more frequently in the isolation of virus and phage DN.1, each with only one contaminating protein, than in the isolation of DS.1 from more complex sources. The high color yields of xanthine, hypoxanthine, guanine, riboguanine derivatives, and phenol require that these substances be removed
(1) Chou, S. C., Goldstein, -4., Biochetiz. J . 75, 109 (1960). ( 2 ) Folin, O., Ciocalteau, V , J . Bzol Chem. 73, 627 (1927). (3) Gelotte, B., .~atur~zssenschczften48, 554 (1961). ( 4 ) Kirby, K. S.,Bzochenz. J 66, 495 (1957). (5) Lowry, 0. H., Rosebrough, S. J , Farr, -4.L., Randall, R. J J . Bzol. Chem. 193,265 (1951). ( 6 ) Shepherd, G. R., Petersen, 11. F., J Chromatog. 9, 455 (1962). 17) Thomas. C. -4.. Berns. I. I , J . M o l . bid. 3. 2f7 il961,. (8) Zadrkil, S'.,Sormova, Z., Sorni, F., Collection Czech. Chem. C'ominim. 26, 2643 (1961). GEORGER . SHEPHERD PEGGY A. HOPKISS ~
Los Alamos Scientific Laboratory University of California Los Alamos, N. 19.
WORKperformed under the auspires of the U. S. Atomic Energy Commission.
Conductometric Determination of Alkalinity of Sea Water SIR: The inductii.ely coupled conductivity meter ( 2 ) is now widely used to determine the salinity of sea water. .idvantages of this approach over the conventional AgXOa titration method are its grea, speed, convenience, high accuracy, and small operator error. Furthermore, the instrument is portable, does not require a temperature-controlled bath, and does not have metallic electrodes. Recently n e have applied the inductive conductivity meter to the determination of alkalinif y of sea water. 'l'he major components responsible for the alkalinity of sea water, HC03-. (:03-2, and H2HO3-, inay be converted to H&03 and H3B03 by titration with HC1. The slight chznge in conductivity during the titration is due to the replacement of HCO3-, COa-2, and H2B03- with C1-. fr very sharp rise in conductivity occurs after the equivalence point due to the addition of both C1- and highly conductive H+. The alkalinity of sea water is directly
proportional to the amount of HC1 needed to reach the sharp equivalence point. EXPERIMENTAL
Standard I . O O N HCl is added in 0.050ml. increments, up to a maximum of 0.45 ml., to 10 100-ml. portions of a sea water sample. After mixing, the
Table
I.
relative conductivity ratio of the samples as compared to international standard sea Lvater is measured a t room temperature with an inductive salinity and conductivity meter, Model 621, Hytech Corp.. San Diego, Calif. The reference conductivity of international standard sea water. ohtainable from Standard Sea-TVater Service, Charlot-
Comparison of Two Methods of Alkalinity Determination of Sea Water
Sea water: From the Pacific, 45"h',, 128"W., Februar!. 23, 1963 Temperature of analysis: 23.0" C. Alkalinity, meq./liter _______ Depth, Salinity, pH method Conductivity Difference, Cmeters p.p.t. (1) method /o 0 2.30 32.56 2.3c 0.0 50 2.2s 32.58 2.26 0.9 100 32.96 2.28 0.9 2.30 2.31 2.32 150 33.66 0.4 200 2.33 2.33 33.88 0.0 300 2.34 2.33 0.4 33.98 400 34,04 2.36 2.37 0.4 34.18 2.41 0.4 600 2.40 2.42 800 2.42 34.30 0.0 1000 34.39 2.45 0.4 2.46
VOL. 35, NO. 10, SEPTEMBER 1963
1549
tenlund, Denmark, with a salinity value of 36.000 parts per thousand (p.p.t.) 11-as taken as 1.00000.
099400
I
I
RESULTS A N D DISCUSSION
-1plot of relative conductivity ratio meq. of HC1 added gave a sharp
cable over a ride range of salinity of st'a water. I t also appears that it would be directly applicable to the determinntion of alkalinity of fresh water by selecting HC1 more dilute than 1N as an additive.
1's.
equivalence point as shown in Figure 1. -1lthough a temperature-compensation 098600 circuit was available within the in+ strument, a temperature fluctuation of Y 2 E 098400 less than 10.1' C. was observed during the analysis. Therefore. no significant 0 98200 temperature correction was necessary to obtain the equivalence point The ml. o f I O 0 N HCI relative standard deviation obtained from 6 determinations was ~ 0 . 5 ~ ~ . Figure 1. Relatibe conductance vs. HCI added I n practice, it would he permissible to take fewer relative conductivity Sample: 100 ml. of sea w a l e r with salinity value readings to construct line5 for extrapcf 34.38 p.p.1. olating the equivalence point, thu, permitting a smaller total wiiple volume. itandnrd deliation of about 1 0 . 9 % Difference betn een their pH method I-qing gla.5 plectrode p H nieawreand our conductility method, for the nients of solution. to which a known duplicate >ample, from a tjpical hyamount of diluttl HC1 has been added drographic cait, nas found to be not -1ndereon and Robin-on ( 1 ) developd a gieater than 1% (Table I). method for the determination of alOur method n a s found to be applikalinity of sea water with a relative
ACKNOWLEDGMENT
The author- gratefully acknowledge the help of Nagdalena Catalfomo in completing a portion of the laborator), work. LITERATURE CITED
(1) .Inderson, D. H., Robinson, R. J . , I s u . EXG.CHEW: ASAL. ED. 18, 767
(1946).
( 2 ) Brown, K.L., Hamon, B. V.) Deep-Serr Research 8, 65 (1961).
I~ILH PARK O ~ I A L C o X , > sO ! LIPHAST
Department of Oceanography Oregon State University Corvallis, Ore. HARRY FRECSI) Department of Chemistry Oregon State University Corvallis, Ore. This work was supported by the Nationxl Science Foundation, GP-622.
Quinoline-8-selenol, a N e w Chelating Agent SIR:Replacement of oxygen in chelating agents by other Group VI elements can give rise to reagents which have unusual metal-stability sequenceq arid whose chelate. are often more stable ( 2 ) . This is of analytical intereqt becauv of the possibility of obtaining reagents I{ hich have unusual selectivity and which can function effectively a t low pH values. As part of our investigation of analogs of 8-quinolinol, quinoline-8selenol (selenosine) !vas prepared and its reactions with various metal ion-.i. were studied. Selenoxine, yepared by diazotization of 8-aminoquinoline and subsequent conversion with potassium seleiiocyanate folloIved by hydro brown crystalline solid ethanolic solution and a blue-yiolet chloroform solution. -1lthough. like Smercaptoquinoline, it is susceptible to atmospheric o d a t i o n . the disrlenide formed can be readily reduced with hypophosphorous acid ( 1 ) . The precipitation characteriqtics of the reagent were studied a.i a function of acidity. From 2J1 HC1 as well as from solutions of higher p H (pH 10 was the highest studied), the folloning metal ions precipitated: Cu(I), brown; Xg,
1550
0
ANALYTICAL CHEMISTRY
orange; Zn, orange; Ctl, orange; Hg(II), greenizh yellow; In, yellow; Tl(I), orange; Tl(III), yellov; Sn(II), wllow; Ph(1I) orange; Sb(III), yello^; 13, yellow; X o ( V I ) , brown-black; TT(VI), yellow; Co(II), red-brown; Rh(III), red-bronn; Pd(I1) red-brolln; and Ir(III), yellow. At pH 2 , the follon ing metal ion, al3o forrncd precipitate;: Fe(1I) and Fe(III), lirown-black: and Si(I1) violet-black. d t pH 5 , V(V) formed a yellow precipitate. Metals that n rre tested and which did not form precipitates a t any pH (up to 10) include Be. X g . Ca, Ba. Hg(I), h l . Ce(II1). Zr, -\s(III), Th, and U(V1). The e\traction of selenoxine chelates into CHC13 follows closely the precipitation behavior with pome interesting eweptions. Hg(II), Pb, l I o ( V I ) , and I r are not extracted below a pH of 2 ; Cd i.i. not evtracted belox a pH of 3 ; Tl(1) and Tl(II1) require pH values of a t least 5 to extract; F'iV) evtracts a t p H 10. The anal) tical behavior of selenoxine ii qeen from these preliminary evperiments to resemble 8-mercaptoquinoline much more closely than it does 8quinolinol. Selenoxine is a more effective reagent in strongly acid solutions
than 8-mc~rcaptoquinoline iivith which T1, Pb, Co, Kh.and Ir do not react ip 2111 HC1). I n strongly acid solut'ionn 8-quinolinol reacts only with Pd(I1). The decrease in bonding-atom electronegativity in the reagent is probably respon.sible for its failure to react wit'h several Group 111 B elements. I t should be noted that both selenosine and 8niercapto:luinoline, in contrast to hquinolinol. do not react with t h e alkalinr earth metal ions. The behavior of selenosine offers promise for the development of new analytical procedures for the separation and determination of a numbpr of mptal ions. LITERATURE CITED
(1) Bankovskis, J., Ievins, A, Luksa, E., Zhur. Obshchei Khirn. 2 8 , 2273 (1958): C. A . 53,2231a (1959). ( 2 ) Corsini, A , Fernando, Q., Freiser, H., -4s.m. CHEM.35, 1424 (1963).
EIICHI SEKIDO QUIKTC-s FERNANDO HESRYFREISER
Department of Chemistry University of Arizona Tucson, hriz. The authors gratefully acknowledge the financial assistance of the Yational Jnstitutes of Health.
