U.S. GEOLOGICAL SURVEY CIRCULAR 996 

. A Modification of the U. S. Geological Survey 

One-Sixth Order Semiquantitative 

Spectrographic Method for the 

Analysis of Geologic Materials that 

Improves Limits of Determination of some 

• Volatile to Moderately Volatile Elements 

A Modification of the U.S. 

Geological Survey One-sixth 

Order Semiquantitative 

Spectrographic Method for the 

Analysis of Geologic Materials 

that Improves Limits of 

Determination of some Volatile 

to Moderately Volatile 

Elements 

By David E. Detro and Elmo F. Cooley 

U.S. GEOLOGICAL SURVEY CIRCULAR 996 

1988 
Department of the Interior 

DONALD PAUL HODEL, Secretary 

U.S. Geological Survey 

Dallas L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Detra, D,E, 

A modification of the U.S. Geological Survey one-sixth order 

semiquantitative spectrographic method for the analysis of geologic materials 

that improves limits of determination of some volatile to moderately volatile 

elements. 

(U.S. Geological Survey circular; 996) 

Bibliography: p. 

Supt. of Docs. no.: I 19.4/2:996 

1. Spectrum analysis. 2. Geochemistry, Analytic. I. Cooley, Elmo 

F. II. Title. Ill. Series. 

QE516.3.D48 1988 551.9 87-600166 

Free on application to the Branch of Distribution, Books and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225 
CONTENTS 

Page 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Instrumentation adaptation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Modified method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Analyses and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

ILLUSTRATIONS 

Page 

FIGURE 1. Filter modification for the optical emission spectrograph . . . . . . . . . . . . . . . . . . 2 

2. Transitional transmission curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

3. Selective volatilization curves for 30 elements . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

TABLES 

Page 

TABLE 1. Lower limits of determination for unmodified and pendulum methods . . . . . . 4 

2. USGS GXR Reference Samples and USGS Glass Standards . . . . . . . . . . . . . . . 5 

3. Results from 10 replicate analyses of 30 elements of the USGS Reference 

Samples and USGS Glass Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

4. Analytical lines and sensitivities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Ill 

A MODIFICATION OF THE U.S. GEOLOGICAL SURVEY ONE-SIXTH ORDER 

SEMIQUANTITATIVE SPECTROGRAPHIC METHOD FOR THE ANALYSIS OF 

GEOLOGIC MATERIALS THAT IMPROVES LIMITS OF DETERMINATION OF 

SOME VOLATILE TO MODERATELY VOLATILE ELEMENTS 

By David E. Detro and Elmo F. Cooley 

ABSTRACT 

A modification of the one-sixth order semiquantitative emission spectrographic method for the analysis of 30 elements in 

geologic materials (Grimes and Marranzino 1968) improves the 

limits of determination of some volatile to moderately volatile 

elements. The modification uses a compound-pendulummounted filter to regulate the amount of emitted light passing 

into the spectrograph. One hundred percent transmission of 

emitted light is allowed during the initial20 seconds of the burn, 

then continually reduced to 40 percent over the next 32 seconds 

using the pendulum-mounted filter, and followed by an additional68 seconds of burn time. The reduction of light transmission during the latter part of the burn decreases spectral background and the line emission of less volatile elements commonly 

responsible for problem-causing interferences. The sensitivity 

of the method for some geochemically important trace elements 

commonly determined in mineral exploration (Ag, As, Au, Be, 

Bi, Cd, Cr, Cu, Ph, Sb, Sn, and Zn) is improved up to five-fold 

under ideal conditions without compromising precision or 

accuracy 

INTRODUCTION 

The semiquantitative emission spectrographic 

method for the analysis of 30 elements in geologic 

materials described by Grimes and Marranzino 

(1968) has been used almost exclusively by the 

U.S. Geological Survey over the last decade to provide a foundation for the assessment of mineral 

resource potential of Federal lands. A modification 

of the method increasing the sensitivity for trace 

elements provides a broader data base which will 

allow the geochemist to make more comprehensive 

geochemical interpretations without supplemental 

acid dissolution and solvent extractions of samples 

analyzed by atomic absorption spectroscopy. Data 

generated using the modification allow the 

geochemist to make interpretations with greater 

confidence at low element concentration levels. 

1 

The use of a compound-pendulum-mounted filter 

adapted to the existing instrumentation (JarrellAsh1 1.5-m optical-emission spectrograph, D.C.-

Arc) increases the sensitivity of the method for 12 

elements (Ag, As, Au, Be, Bi, Cd, Cr, Cu, Ph, Sb, 

Sn, and Zn), while the sensitivity of only one element (W) is comprised and the sensitivity for the 

remaining 17 elements is unchanged. Ideal 

operating conditions are required to obtain the 

best results. Therefore, production rates are less 

than those that can be anticipated using the 

method described by Grimes and Marranzino, 

limiting the utility of the adaption to specific 

research requiring better sensitivity 

INSTRUMENTATION ADAPTATION 

The modification uses a compound pendulummounted filter to regulate the amount of emitted 

light passing into the spectrograph. A compound 

pendulum is defined as any friction damped "real" 

pendulum having a mass distributed over its entire 

body, a calculable center of gravity. 

The pendulum used in the modification has an 

aluminum arm with an adjustable brass counterweight. The arm is attached to a Teflon hub, and 

the hub of the pendulum is mounted on a 6-in. rod 

extendiitg out from an aluminum base which is 

attached directly onto the arc stand (fig. 1). To 

maintain frictional consistency over time, a Teflon 

sleeve is placed on the rod on which the Teflon hub 

rotates. A 97 o arc of 8-in. radius is attached to the 

end of the aluminum pendulum in such a way that 

the arc extends 48.5 o on each side of the attachment point. A l-in. filter is centered on the 0 o 

1 Any use of trade names is for descriptive purposes only and does not imply 

endorsement by the USGS 
z 

0 

(j) 

IJ) 

~ IJ) 

z 

<( 

a: 

IIz 

w 

u 

a: 

w 

0... 

30 

0 

I 

I 

I 

I 

I 

I 

I 

:_Pendulum -.l"': -------~ 1 phase 1 

I (20-52 seconds) I I I 

90 100 

FIGURE 1.-Compound-pendulum-mounted filter modification 

for the optical-emission spectrograph. 

position of the arc so that the emitted light path 

is centered vertically on the filter. A series of three 

100-percent transmission ports and four 0-percent 

transmission spokes extend outward on both sides 

from the 0 ° position of the arc. This configuration 

allows for smooth, continuous filtering transition 

of emitted light. The filter is made from a section 

of exposed film (Kodak SA-1)1 providing for 40-

percent transmission of light above 270.0 

nanometers (nm). The pendulum is set in a horizontal position at the start of each burn and held in 

place by a low-voltage plunger solenoid which is 

wired to a timer and is automatically activated 20 

seconds after the arc is struck, releasing the pendulum. Listed below are the instrumentation and 

analytical parameters used in the development of 

the modification. 

Spectrograph: 1.5-m Wadsworth-mounted JarrellAsh, equipped with a 15,000 lines/in. (590 

grooves/mm) lined grating blazed for 310.0 nm 

providing for a dispersion of 5.45 angstroms/~ over a spectral range of 210.0 nm to 480.0 nm 

in the second order, slit width of 10 micrometers. 

Source: Direct-current 220 volts with maximum arc 

current of 13 amperes 

Electrodes: 

Upper: preformed- 1/8-in. diameter with 8 o 

taper (UltraCarbon 5001) 

Lower: preformed graphite 1/4-in. diameter, 

crater wall thickness of 0.04 in., crater 

diameter of 0.144 in., and crater depth of 

0.313 in. (UltraCarbon 7075) 

2 

Film: 35-mm Spectrum Analysis No. 1 (SA-l) emulsion, processed with D-19 Kodak developer for 

2.5 minutes at 20 °C, fixed for 3 minutes, rinsed 

in cold water and air dried 

Arc parameters: 

Electrode gap: 4 mm 

Exposure: 120 seconds 

0-20 seconds at 100-percent transmission 

20-52 seconds transition from 100-percent 

transmission to 40 percent transmission 

52-120 seconds at 40-percent transmission 

for wavelengths of 270.0 nm and above 

52-120 seconds at 0-percent transmission for 

wavelengths below 270.0 nm 

Current: Initial excitation of 6 amperes increased 

to 13 amperes immediately 

MODIFIED METHOD 

The method allows for 100-percent transmission 

of light for the initial 20 seconds of the burn. During these initial20 seconds, the majority of the 12 

elements (Ag, As, Au, Be, Bi, Cd, Cr, Cu, Ph, Sb, 

Sn, and Zn) are volatilized. After 20 seconds have 

elapsed, a solenoid releases the pendulum-mounted 

filter from a horizontal position, so that it swings 

freely through the light path with an average 

period of 0.80 seconds. As the volatile elements are 

consumed during the 32-second pendulum phase, 

the distillation of the elements into the arc decreases, and the refactory elements begin to volatilize more rapidly. When the pendulum has stopped, 

all emitted light is filtered to 40-percent transmittance for the remaining 68 seconds of the burn. 

During the last phase of the burn, when the 40-

percent filter is in place, the majority of the refactory elements are volatilized. Since the free-swinging compound-pendulum bob passes through the 

optical-emission light path with a decreasing 

amplitude, it provides for a transitional period of 

32 seconds in which the emitted light will be 

filtered from 100- to 40-percent transmission (fig. 

2). Therefore, the period the filter is in the light 

path increases with time as a function of the 

decreasing amplitude of the pendulum. The resulting smooth, continuous increase in filtration as 

expressed by the curve in figure 2 is aided by the 

configuration of the pendulum bob. Without the 

transmission ports and spokes on the bob extensions, the curve would be relatively flat over the 

first 20 seconds and extremely steep over the last 

10 seconds of the pendulum phase. 
Teflon hub 

• 

2 INCHES 

I 

Aluminum mounting box 

B. -Top View / 

Adjustable 

weight 

Arc stand 

Cylindrical lens 

\olenoid 

_ Optical emission 

-: path 

------- - ------ ------

40 percent filter 

A. -Front View 

C. -Side View 

FIGURE 2.-Transitional transmission curve. (Percent transmission was calculated by exposing the spectrographic film to a constant UV light source for continuous 10-second intervals. Three densimetric readings were taken for each 10-second interval and averaged.) 

The effect of the modification is an increase in 

sensitivity of the method for the 12 elements: Ag, 

As, Au, Be, Bi, Ca, Cr, Cu, Ph, Sn, and Zn by a factor of up to 5 (table 1) while the sensitivity of 

tungsten decreased as a direct response to the 

filtering process. 

DISCUSSION 

Geologic materials have complex and variable 

matrices. Refractory elements which commonly 

make up the matrices of these geologic materials 

cause difficulty in the interpretation of the resulting 

spectrum by producing line interferences on the 

volatile-element emission lines. In addition, large 

3 

changes in matrix composition of samples can cause 

changes in line intensities in the spectrum. These 

variations in composition characteristically cause 

changes in arc temperatures and the distillation 

rates of specific elements into the arc. Thus, the 

change in percent transmittance from 100 to 40 percent must be a gradual transition (fig. 2) rather 

than a single or multistep transition. This transition helps reduce the effects of matrix variations 

by providing a relatively long period of time compared to the total burn over which the change in 

transmittance takes place, and yet, it still produces 

the desired effects of increasing sensitivity of 

specific elements while maintaining a good line-tobackground ratio. 
z 

0 

i= 

~ 30 1-

z 

w 

u 

z 

0 

u 

1- 20 z 

w 

u 

a: 

w 

a.. 

w 

> 10 

w 

~ a: 

Pendulum 1 

phase -1 

(20-52 seconds) I 

I 

I 

I 

I 

I 

I 

I 

o Moderately volatile elements: Au, B, Ba, Be, 

Ca, Cr, Cu, Fe, La, Mg, Mn, Sn, Sr, V, Y 

x Refractory elements: Co, Mo, Nb, N~ Sc, Ti, W, Zr 

o~--~--~--~--~--~--6~0---L---8~0--~---,~oo--~---, 2-o~~--,~4-o--~--,~6~o--~--~--~,8o 

TIME, IN SECONDS 

FIGURE a.-Selective volatilization curves for 30 elements in GSE standard from the USGS Trace Element glass standards 

(Filter conditions: 100% transmission for 180 seconds.) 

TABLE 1.-Lower limits of determination for unmodified and 

pendulum methods 

Element 

Ag 

As 

Au 

Be 

Bi 

Cd 

Cr 

Cu 

Pb 

Sb 

Sn 

w 

Zn 

Grimes and Marranzino, 

(1968) (parts per million) 

0.5 

200 

10 

1 

10 

20 

10 

5 

10 

100 

10 

50 

200 

Filtered pendulum modification 

(parts per million) 

0.1 

50 

2 

.5 

2 

5 

2 

1 

2 

20 

5 

100 

50 

In order to better understand and effectively 

eliminate or reduce interference problems, selective volatilization rates (SVRs) have been studied 

for the 30 elements analyzed routinely in geologic 

samples. The U.S. Geological Survey Trace Element Glass Standards sample, GSE, was utilized 

because its uniform concentration range for the 

major elements is comparable to silicate matrices 

found in the natural environment. 

The SVRs of each of the selected elements in the 

standard were determined by racking the camera 

at 10-second intervals during a 180-second excita4 

tion period. The 30-element semiquantitative spec-r 

trographic method (Grimes and Marranzino, 1968) 

was used to determined the emission concentration for each element at each 10-second interval, 

and the value was recorded. From these data the 

30 elements were grouped into three subsets: 

volatile, moderately volatile, or refractory The 

emission concentrations for all elements within 

each subset were added for each 10-second interval, and the resulting values were then changed 

to relative percent concentration, which was 

rounded to the nearest whole percent. Plots of 

selective volatilization rates for the three subsets 

were calculated and are shown in figure 3. 

The visual determination of line intensity is 

accurate to within ± 30 percent of the correct value 

(Ahrens and Taylor, 1961). This accuracy is adequate for the intended purpose of the SVRs in 

demonstrating general volatilization rates of 

volatile and retractory elements. We compared 

visual determination versus densimetric readings 

for several elements and found the visual determinations were accurate within the limits set forth 

by Ahrens and Taylor (1961). 

The spectrographic conditions under which the 

SVRs in figure 3 were determined are shown in 

table 2. However, 100-percent transmission was 

used for the entire 180-second bum. It was determined from the SVRs that the most effective filtering design is one in which the pendulum phase 

ends approximately at the intersect point of the 

volatile and refractory curves. 
TABLE 2.-Description of USGS GXR Reference Samples and USGS 'IJoace-Element Glass Standards 

Geochemical Exploration Reference Samples 

Standard designation 

GXR-1 

GXR-2 

GXR-3 

GXR-4 

GXR-5 

GXR-6 

Description and source 

Jasperoid: Drum Mountains, Utah 

Soil: Park City, Utah 

Fe-Mn-W-rich Hot Spring Deposit: 

Humboldt County, Nevada 

Porphyry Copper Mill Heads: Utah 

Soil (B zone): Somerset County, Maine 

Soil (B zone): Davidson County, North Carolina 

USGS Trace-Element Glass Standards 

Standard designation Additive element concentration 

GSB 0.5 ppm 

GSC 5.0 ppm 

GSD 50 ppm 

GSE 500 ppm 

Approximate matrix composition: 

Si02 - 62% CaO - 5% 

Al 203 - 14% Na2o - 4% 

Fe2o3 - 7% K20 - 4% 

Mgo - 4% H20 - ? 

Additive elements: 

Ti B Ce Eu La 

Mn Ba Cs Gc Li 

Ag Be Co Hf Mo 

As Bi Cr In Nb 

Au Cd Cu Ir Ni 

ANALYSES AND RESULTS 

The pendulum method was used to analyze two 

different sets of reference samples with each 

analysis being replicated 10 times. The reference 

materials included the Geochemical Exploration 

Reference samples (GXR 1-6), which consist of six 

rock and soil samples representing the broad range 

5 

Pb Rh Ta w F 

Pd Sb Te y 

Pt Sc Tl Zn 

Rb Sn u Zr 

Rc Sr v Cl 

of matrices found in geologic materials, and four 

USGS 'fra.ce..Element Glass Standards synthetically 

produced by Corning Glass Works, which are composed of approximately 0.5, 5.0, 50, and 500 parts 

per million of 46 additive elements (table 2). The 

resulting reference material spectra were compared to 

spectra for the six-step prepared standards (Grimes 

and Marranzino, 1968). Results reported on table 3 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples and USGS Trace-Element 

Glass Standards 

[Results listed by element showing sample designation, range, median, mean, relative standard deviation (RSD) (reported as percent), and accepted value. Values reported 

in parts per million (ppm) except Fe, Mg, Ca, and Ti which are reported in percent. Accepted values for GXR Reference samples obtained from Gladney (1980) except 

for Nb, Sn, andY whose values were obtained from Allcott and Lakin (1978) and Ag, Au, Bi, and Cd whose values were obtained from Viets (1978). Accepted values 

for the USGS Trace-Element Glass Standards were obtained from Myers and others (1976). An L indicates the element was detected but below the level of determina· 

tion. The symbol N or < specifies the element was not detected. When an L was used in calculating the median, mean, and RSD, it was given a real value equal 

to the next lower reporting interval below the value of the lower limit of determination for that element.] 

Sample Range Median Mean RSD Accepted value 

Fe% 

GXR-1 G20 G20 G20 0.00 24.7 ± 1.8 

GXR-2 3- 5 3 3.8 25.78 1.9 ± .23 

GXR-3 20 20 20 0 18.6 ± 1.8 

GXR-4 3- 5 5 4.8 12.50 2.97 ± .43 

GXR-5 5- 7 5 5.4 14.81 3.19 ± .29 

GXR-6 7-15 10 9.3 25.47 5.58 ± .42 

GSB 5- 7 5 5.8 16.89 

GSC 2- 7 5 5.7 27.23 

GSD 5- 7 5 5.4 14.81 

GSE 3- 7 5 5.4 22.22 

Mg% 

GXR-1 .2 - .3 .3 .29 10.34 .21 ± .01 

GXR-2 1 - 2 2 1.80 18.43 .88 ± .05 

GXR-3 .7 - 2 1.5 1.52 30.41 .64 ± .05 

GXR-4 2 - 3 2 2.4 20.41 1.65 ± .05 

GXR-5 1.5 - 2 2 1.95 7.69 1.22 ± .05 

GXR-6 1 - 2 1.5 1.55 17.37 .65 ± .04 

GSB 2 - 3 3 2.9 10.34 

GSC 2 - 3 3 2.9 10.34 

GSD 3 3 3.0 0 

GSE 3 3 3.0 0 

6 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Ca% 

GXR-1 1 - 1. 5 1 1.05 14.29 .87 ± .08 

GXR-2 1 1 .97 9.28 .82 ± .04 

GXR-3 7 -10 10 9.1 15.11 14.1 ± .6 

GXR-4 1 1 1 0 .9 ± .05 

GXR-5 0 5 - .7 .5 .58 16.89 .75 ± .06 

GXR-6 .07- .15 .01 .099 20.92 .095 ± .01 

GSB 3 - 5 4 4.0 25.00 

GSC 2 - 5 3 3.5 29.28 

GSD 2 - 3 3 2.9 10.34 

GSE 3 3 3 0 

Ti% 

GXR-1 .02 -.05 .03 .033 27.27 .06 ± .005 

GXR-2 .2 -.5 .3 .34 32.75 .28 ± .03 

GXR-3 .05 -.1 .07 .071 16.00 .10 ± .02 

GXR-4 .15 -.3 .2 .21 23.33 .26 ± .03 

GXR-5 .15 -.2 .2 .195 7.69 .21 ± .03 

GXR-6 .3 -.15 .5 .48 22.44 .5 ± .04 

GSB L(.022)-.002 L(.002) .0016 12.5 .0006 

GSC L( .002) L{ .002) L( .002) 0 .0011 

GSD .005 -.01 .007 .0072 22.22 .0044 

GSE .03 -.05 .05 .048 12.50 .049 

are identified with geometric brackets whose these brackets, 1., 0.7, 0.5, 0.3, 0.2, 0.15, 0.1, etc. 

boundaries are 1.2, 0.83, 0.56, 0.38, 0.26, 0.18, 0.12, Precision and accuracy of the pendulum method 

etc., but are reported arbitrarily as midpoints of are best demonstrated in table 3, which presents 

7 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Ag 

GXR-1 30 - 50 30 38 25.78 32.6 

GXR-2 20 20 20 0 17.4 

GXR-3 N(.l) N(.l) N(.l) 0 .06 

GXR-4 2 2 2 0 3.6 

GXR-5 .5 - 1 1 .89 19.75 .82 

GXR-6 .1 - .2 .2 .19 15.79 .29 

GSB .5 - 1 .5 .55 27.20 .5 

GSC 5 5 5 0 4 

GSO 50 50 50 0 37 

GSE 500 500 500 0 380 

As 

GXR-1 300 -500 300 380 25.78 460 ± 30 

GXR-2 N(50) N(50) N(50) 0 31 ± 5 

GXR-3 2,000 2,000 2,000 0 4,000 ± 450 

GXR-4 100 100 100 0 98 ± 10 

GXR-5 N(50) N(50) N(50) 0 12 ± 3 

GXR-6 300 300 290 10.34 340 ± 30 

GSB N(50) N( 50) N(50) 0 .3 

GSC N(50) N(50) N(50) 0 6 

GSD N(50) N(50) N( 50} 0 42 

GSE 300 300 300 0 450 

the range of the 10 replicate analyses for each ele- value of that element for the particular reference 

ment, the mean value, median value, percent rela- material. A general indication of accuracy can be 

tive standard deviation (RSD), and the accepted obtained by comparing the median and mean 

8 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Au 

GXR-1 L(2) L(2) L(2) 0.00 3.7 

GXR-2 N(2) N(2) N(2) 0 .05 

GXR-3 N(2) N(2) N(2) 0 .06 

GXR-4 N(2) N(2) N(2) 0 .60 

GXR-5 N(2) N(2) N(2) 0 <.05 

GXR-6 N(2) N(2) N(2) 0 .1 

GSB N(2) N(2) N(2) 0 .1 

GSC N(2) N(2) N(2) 0 1.2 

GSD 10 10 10 0 14 

GSE 30-50 30 32 18.75 50 

B 

GXR-1 20-30 20 21 14.28 15.3 ± .5 

GXR-2 100 100 100 0 44 ± 1 

GXR-3 200 200 200 0 180 ± 20 

GXR-4 10 10 10 0 4.3 ± .4 

GXR-5 50 50 50 0 25 ± 2 

GXR-6 10-20 20 17 26.96 11 ± 1 

GSB 50 50 50 0 18 

GSC 50 50 50 0 20 

GSD 70 70 70 0 50 

GSE 500 500 500 0 500 

values from the replicate analyses to the accepted semiquantitative data that are reported as intervalues. Even though it is not acceptable to make val midpoints, a visual comparison will show 

a statistical comparison between quantitative and excellent agreement between the experimental 

9 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range 

GXR-1 700-1,000 

GXR-2 1,500-3,000 

GXR-3 5,000 

GXR-4 1,500-2,000 

GXR-5 1,500-2,000 

GXR-6 1,000-2,000 

GSB 

GSC 

GSD 

GSE 

30- 50 

20- 50 

70- 150 

500 

GXR-1 1 - 2 

GXR-2 1 - 2 

GXR-3 30 -100 

GXR-4 2 

GXR-5 .5 - 1 

GXR-6 .7 - 1 

GSB 

GSC 

GSD 

N(.5) 

5 

30 - 50 

GSE 500 

Median 

1,000 

2,000 

5,000 

1,500 

2,000 

1,500 

40 

50 

100 

500 

1.5 

1.5 

50 

2 

1 

1 

N(.5) 

5 

50 

500 

Mean 

Ba 

970 

2,050 

5,000 

1,550 

1,900 

1,550 

40 

43 

102 

500 

Be 

1.65 

1.55 

55 

2 

.84 

.97 

N(.5) 

5 

46.0 

500 

RSD 

9.28 

17.07 

0 

9.68 

10.52 

17.37 

25.00 

25.58 

17.97 

0 

19.40 

22.58 

27.27 

0 

24.51 

9.28 

0 

0 

17.39 

0 

Accepted value 

560 ± 120 

2,000 ± 400 

4,700 ± 800 

1,350 ± 330 

1,800 ± 500 

1,100 ± 300 

31 

39 

90 

500 

1.12 ± .17 

1.64 ± .09 

26 ± 1 

2.1 ± .2 

1.19 ± .16 

1.1 ± .1 

3.5 

44 

500 

values and the acceptable values. Specific attention is drawn to the test studies of Ag, Bi, Cd, Sb, 

and Zn in table 4 where the accepted value in a 

reference sample is at the stated limit of determination and the pendulum method is detecting the elements at these low levels with excellent precision. 

10 
TABLE 3.-Results from 10 replicate analyses of30elements of the USGS GXRReference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSO Accepted value 

Bi 

GXR-1 1,500-2,000 2,000 1,800 18.43 1725 

GXR-2 N(2)-L(2) L(2) .4 

GXR-3 N{2) N{2) N{2) 0 <.2 

GXR-4 20- 30 20 21 14.29 21.2 

GXR-5 N(2) N(2) N(2) 0 .4 

GXR-6 N(2) N{2) N(2) 0 .2 

GSB N{2) N(2) N(2) 0 

GSC 5 5 5 0 

GSO 50 50 50 0 

GSE 500 500 500 0 

Cd 

GXR-1 N(5) N(5) N(5) 0 3.0 

GXR-2 L(5)- 7 4 4.2 31.59 3.9 

GXR-3 N{5) N(5) N(5) 0 .4 

GXR-4 N(5) N(5) N(5) 0 .3 

GXR-5 N(5) N(5) N(5) 0 .14 

GXR-6 N(5) N(5) N(5) 0 .11 

GSB N(5) N(5) N(5) 0 

GSC 5 5 5 0 3 

GSO 50- 70 50 56.0 16.37 30 

GSE 500 500 500 0 420 

11 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample 

GXR-1 

GXR-2 

GXR-3 

GXR-4 

GXR-5 

GXR-6 

GSB 

GSC 

GSD 

GSE 

GXR-1 

GXR-2 

GXR-3 

GXR-4 

GXR-5 

GXR-6 

GSB 

GSC 

GSD 

GSE 

Range 

10 

10- 20 

30-100 

15- 20 

30- 70 

15- 50 

N(5) 

5- 10 

30- 50 

300-500 

10- 15 

50 

10- 15 

50- 70 

100 

70-100 

5- 7 

5- 10 

50 

500 

Median 

10 

15 

85 

20 

50 

17.5 

N(5) 

10 

30 

500 

10 

50 

10 

70 

100 

70 

5 

7 

50 

500 

Mean 

Co 

10 

16.5 

75 

18 

50 

22.5 

N(5) 

9.5 

38 

480 

Cr 

10.5 

50 

10.5 

68 

100 

76 

5.2 

8.3 

50 

500 

RSD 

0.00 

19.40 

35.40 

13.61 

17.89 

47.92 

0 

15.79 

25.78 

12.50 

14.29 

0 

14.29 

8.82 

0 

15.79 

11.54 

34.52 

0 

0 

Accepted value 

9.3 ± 1.1 

9 ± 2 

48 ± 5 

16 ± 2 

30 ± 5 

14 ± 3 

2 

6 

35 

450 

10 ± 2 

37 ± 10 

19 ± 1 

64 ± 10 

100 ± 5 

96 ± 10 

3 

7 

47 

490 

The precision of the method is also shown by the percent with an average of 9.85 percent. Comrelative standard deviations (RSD) in table 4. The monly acceptable RSDs for the semiquantitative 

RSDs o~~ained range in magnitude from 0 to 77 emission spectrographic method range from 10 to 

12 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Cu 

GXR-1 1,000-1,500 1,000 1,050 14.28 1,300 ± 100 

GXR-2 100- 150 150 145 10.34 69 ± 2 

GXR-3 10- 20 17.5 17 19.51 10.8 ± 0.8 

GXR-4 5,000-7,000 7,000 6,800 8.82 6,500 ± 200 

GXR-5 300- 500 300 340 23.53 360 ± 20 

GXR-6 100- 150 100 110 18.18 105 ± 12 

GSB 3- 5 5 4.2 23.33 5 

GSC 5- 10 7 7.1 15.99 9 

GSO 50- 70 50 54.0 14.81 45 

GSE 300- 500 500 480 12.50 500 

La 

GXR-1 L(20) L(20) L(20) 0 6.1 ± .3 

GXR-2 L(20) L(20) L{20) 0 25 ± 1 

GXR-3 L(20) L{20) L(20) 0 8.5 ± 1 

GXR-4 70- 100 70 82 17.92 64 ± 5 

GXR-5 50 50 50 0 18 ± 4 

GXR-6 L(20) L(20} L{20) 0 14 ± 2 

GSB L{20) L(20) L(20) 0 

GSC L{20) L(20} L(20) 0 5 

GSD 50 50 50 0 47 

GSE 500 500 500 0 550 

30 percent (Mosier, 1972). Of the 10 RSDs greater precision because of the poor background-to-line 

than 30 percent, 5 can be attributed to analyses ratios on the upper end of the spectrum where the 

of nickel and cobalt. These two elements show less nickel and cobalt lines that were used are located 

13 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Mn 

6XR-1 700-1,000 1,000 970 9.28 

6XR-2 1,000-1,500 1,500 1,300 18.84 960 ± 100 

6XR-3 65,000 65,000 65,000 0 22,300 ± 2,000 

6XR-4 150- 300 200 215 27.61 140 ± 20 

6XR-5 200- 500 300 330 35.98 280 ± 20 

6XR-6 1,000 1,000 1,000 0 1,000 ± 50 

6SB 200- 300 200 210 14.29 190 

6SC 200 200 200 0 200 

6SD 200- 300 200 210 14.29 210 

6SE 700 700 700 0 600 

Mo 

6XR-1 L{5) L(5) L(5) 0.00 10 ± 2 

6XR-2 N(5)- 10 N(5) 1.5± .5 

6XR-3 N(5)-L{5) L(5) <6 

6XR-4 200-300 300 260 18.84 310 ± 25 

6XR-5 30- 50 40 40 25.00 30 ± 4 

6XR-6 N(5)- 20 N(5) 1.7± .4 

6SB N(5) N(5) N( 5) 0 2 

6SC L(5)- 7 5 5.2 20.71 6 

6SD 50 50 50.0 0 46 

GSE 300-500 500 480 12.50 500 

14 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Nb 

GXR-1 L(20) L(20) L(20) 0 <10 

GXR-2 L(20) L(20) L(20) 0 <10 

GXR-3 L(20)- 20 20 18 13.61 <20 

GXR-4 L(20) LC20) L{20) 0 <20 

GXR-5 L(20) L(20) L(20) 0 <10 

GXR-6 L(20) L(20) L(20) 0 <10 

GSB L(20) L(20) L(20) 0 

GSC L(20) L(20) L(20) 0 5 

GSD 20 20 20 0 40 

GSE 100-150 150 145 10.34 500 

Ni 

GXR-1 20- 30 20 24 20.41 42 ± 10 

GXR-2 20- 50 20 25 36.88 18 ± 3 

GXR-3 30- 70 50 46 26.09 55 ± 5 

GXR-4 30- 70 50 46 26.09 38 ± 4 

GXR-5 50- 150 70 76 40.43 63 ± 7 

GXR-6 15- 100 20 33 77.61 22 ± 4 

GSB 10- 15 10 11.0 18.18 14 

GSC 10- 15 15 13.5 16.97 18 

GSD 50 50 50 0 55 

GSE 500 500 500 0 500 

(Ni, 341.4 nm; Co, 345.3 nm). To help improve the between the grating and the spectrum film, as 

spectrum at the high end, a glass plate, which pro- close to the film as possible. The plate was posivided an additionallO to 15 percent light filtra- tioned in such a way that it covered the wavetion below 400.0 nm, was placed in the light path lengths of light between 340.0 nm and 350.0 nm. 

15 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSO Accepted value 

Pb 

GXR-1 300- 500 400 400 25.00 670 ± 20 

GXR-2 700-1,000 1,000 880 16.70 615 ± 15 

GXR-3 10- 20 10 13 30.77 15 ± 2 

GXR-4 50- 70 70 64 14.32 

GXR-5 20 20 20 0 22 ± 2 

GXR-6 100 100 100 0 110 ± 10 

GSB 10- 15 15 14.5 10.34 13 

GSC 10- 15 15 13.5 16.97 15 

GSD 50- 70 50 56.0 16.37 52 

GSE 300- 500 500 460 17.39 500 

Sb 

GXR-1 100-150 100 105 14.29 124 ± 6 

GXR-2 50 50 50 0 48 ± 5 

GXR-3 20- 30 30 26 18.84 40 ± 3 

GXR-4 L(20)-N(20) N{20) 4.4 ± .8 

GXR-5 N{20) N(20) N{20) 0 2 ± 1 

GXR-6 N(20) N{20) N{20) 0 3.8 ± .7 

GSB N{20) N{20) N(20) 0 

GSC N{20) N{20) N{20) 0 

GSD 30 30 30 0 37 

GSE 500 500 500 0 470 

CONCLUSIONS assessment of mineral resource potential in regional geochemical exploration study areas can be imSemiquantitative analytical data for some proved by utilizing a modification to the one-sixth 

volatile to moderately volatile elements used in the order semiquantitative emission spectrographic 

16 
TABLE 3.-Results from 10 replicate analyses of30 elements of the USGS GXRReference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Sc 

GXR-1 L( 5) L(5) L{5) 0 1.7± .1 

GXR-2 7- 10 10 9.4 12.77 6.8 ± .2 

GXR-3 20- 30 20 23 19.92 18 ± 1 

GXR-4 10- 15 10 10.5 14.29 8.3 ± .4 

GXR-5 10 10 10 0 7.8 ± .4 

GXR-6 20- 50 20 26 35.25 31 ± 1 

GSB N(5) N(5) N(5) 0 

GSC N(5) N{5) N(5) 0 

GSD N(5) N(5) N(5) 0 3 

GSE 20- 30 20 22 18.18 30 

Sn 

GXR-1 50 50 50 0.00 63 

GXR-2 N(5) N(5) N(5) 0 <( 10) 

GXR-3 N( 5) N(5) N(5) 0 <(10) 

GXR-4 15- 20 15 17 14.41 <( 10) 

GXR-5 N(5) N(5) N(5) 0 <( 10) 

GXR-6 N(5) N(5) N(5) 0 <(10) 

GSB N(5) N(5) N(5) 0 .6 

GSC 5 5 5 0 5 

GSD 50 50 50 0 43 

GSE 500 500 500 0 440 

method described by Grimes and Marranzino to 40 percent over 32 seconds after the initial 20 

(1968). The modification uses a compound- seconds of the burn at 100 percent. Filtering more 

pendulum-mounted filter to provide a transitional light during the latter part of the bum improves 

change for the filtering of emitted light from 100 the sensitivity of the method for 12 trace elements 

17 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Sr 

GXR-1 500-700 700 660 12.12 280 ± 60 

GXR-2 100-150 100 105 14.29 160 ± 23 

GXR-3 1,000 1,000 1,000 0 1,140 ± 100 

GXR-4 200-300 200 210 14.29 220 ± 30 

GXR-5 100 100 100 0 120 ± 20 

GXR-6 N(100) N(lOO) N(100) 0 42 ± 9 

GSB N(100) N(100) N(100) 0 26 

GSC N(100) N(100) N(lOO) 0 27 

GSD N(100) N(100) N(100) 0 64 

GSE 500 500 500 0 500 

v 

GXR-1 70- 100 85 88 16.70 88 ± 9 

GXR-2 50- 100 70 74 19.30 57 ± 20 

GXR-3 30- 50 30 32 18.75 39 ± 10 

GXR-4 70- 100 100 97 9.28 92 ± 15 

GXR-5 50- 70 70 66 12.12 60 ± 20 

GXR-6 150- 200 200 180 13.61 180 ± 20 

GSB L(10) L(lO) L(lO) 0 2 

GSC L(10) L(10) L(10) 0 6 

GSD 50 50 50 0 45 

GSE 500 500 500 0 500 

commonly used in mineral exploration by reduc- causing interferences without compromising preciing spectral background and the line emission of sion and accuracy. Using this modification greatly 

elements commonly responsible for problem- reduces the capacity of the method in terms of 

18 
TABLE 3.-Results from 10 replicate analyses of30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSO Accepted value 

w 

GXR-1 L( 100)- 100 L ( 100) 76 15.79 

GXR-2 N(100) ~(100) N(100) 0 1.8 ± .2 

GXR-3 10,000-G10,000 10,000 10,500 14.29 10,800 ± 600 

GXR-4 N(lOO)-L(lOO) N(lOO) 28 ± 5 

GXR-5 N(100) N(lOO) N(lOO) 0 .5 ± .2 

GXR-6 N(100) N(100) N(100) 0 .88 ± .18 

GSB N(100) N(100) N(100) 0 

GSC N(100) N(100) N(100) 0 

GSO N(100) N(100) N(lOO) 0 50 

GSE 150 150 150 0 420 

y 

GXR-1 30- 70 50 48 22.44 57 ± 11 

GXR-2 15- 30 20 21.5 20.93 16 ± 1 

GXR-3 20- 30 30 26 18.84 16 ± 2 

GXR-4 10- 15 15 13 18.84 12 ± 3 

GXR-5 10- 20 15 14.5 18.57 16 ± 3 

GXR-6 15- 30 15 18 25.46 14 ± 3 

GSB N(10) N( 10) N( 10) 0 4 

GSC N( 10) N(10) N( 10) 0 8 

GSO 50 50 50 0 46 

GSE 500 500 500 0 490 

19 
TABLE 3.-Results from 10 replicate analyses of 30 elements of the USGS GXR Reference Samples 

and USGS Trace-Element Glass Standards-Continued 

Sample Range Median Mean RSD Accepted value 

Zn 

GXR-1 1s000 1s000 1s000 0 740 ± 110 

GXR-2 500-1s000 850 830 21.59 500 ± 60 

GXR-3 150- 200 200 180 13.61 220 ± 70 

GXR-4 100 100 100 0 64 ± 10 

GXR-5 50 50 50 0 50 ± 5 

GXR-6 100 100 100 0 120 ± 20 

GSB N(50) N(50) N(50) 0 3 

GSC N(50) N( 50) N(50) 0 12 

GSD 50 50 50 0 43 

GSE 500 500 500 0 500 

Zr 

GXR-1 20 20 20 0.00 66 ± 20 

GXR-2 150-300 200 225 22.77 200 ± 40 

GXR-3 30- 50 50 44 20.83 <200 

GXR-4 150-200 150 165 13.89 200 ± 40 

GXR-5 150-200 150 165 13.89 140 ± 20 

GXR-6 70-200 100 116 36.21 106 ± 8 

GSB N( 10) N( 10) N(10) 0 4 

GSC N( 10) N(10) N(10) 0 6 

GSD 50 50 50 0 48 

GSE 300-500 500 460 17.39 480 

20 
TABLE 4.-Analyticallines and sensitivities 

Element Lines used (nm) Limit of determination (ppm) 

Ag 328.068 0.1 

338.280 .5 

As 286.045 50 

278.020 50 

Au 267.595 2 

B 249.773 10 

Ba 455.404 20 

Be 313.042 .5 

Bi 312.107 2 

Cd 3221 5 

326.106 5 

Co 345.351 5 

Cr 425.435 2 

284.325 10 

Cu 327.396 1 

Fe 305.909 <50 

La 333.749 50 

Mg 278.142 <200 

Mn 293.930 10 

307.027 

Mo 317.035 5 

319.397 10 

Nb 316.340 20 

319.498 20 

Ni 341.477 5 

Pb 366.347 5 

283.307 2 

21 
TABLE 4.-Analyticallines and sensitivities-Continued 

Element Lines used (nm) 

Sb 259.806 

287.792 

Sn 317.502 

Sc 335.373 

Sr 346.446 

Ti 316.852 

v 345.344 

w 294.738 

y 324.228 

332.788 

Zn 330.259 

334.502 

Zr 327.926 

339.198 

sample throughput. However, this study should 

provide a basis for the design of an automated 

mechanism allowing for greater production. 

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Ahrens, L. H., and Taylor, J. R., 1950, Spectrochemical analysis: 

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Allcott, G. H., and Lakin, H. W., 1978, Tabulation of 

geochemical data furnished by 109 laboratories for six 

geochemical exploration reference samples: U.S. Geological 

Survey Open-File Report 78-163, 100 p. 

Gladney, E. S., 1980, Compilation of elemental concentration 

data for the United States Geological Survey's six 

geochemical exploration reference materials: Los Alamos 

Scientific Laboratory Informal Report LA-8473-MS, 18 p. 

u U.S. GOVERNMENT PRINTING OFFICE:1988-573-047/66063 

22 

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50 

20 

5 

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100 

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10 

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10 

50 

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10 

10 

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DETRA AND COOLEY-MODIFICATION OF ONE-SIXTH ORDER SEMIQUANTITATIVE SPECTROGRAPHIC ANALYSIS-U.S. G