Test swab cartridge type device and method for detecting lead and cadmium

A swab is impregnated with a test reagent such that a test for a specific substance can be effected by rubbing the impregnated swab over the surface to be tested and then viewing the swab for a reagent reaction. A method for testing for a metal includes impregnating a swab with a reagent, such as, for example, a rhodizonate dye reagent when testing for lead, and rubbing the swab over a surface suspected of containing the metal. If a metal is present in the surface, a reaction with the metal produces an easily detectable color on the swab tip.

TECHNICAL FIELD 
The present invention relates to a swab and a method of using the swab in a 
test for certain chemical elements, and more particularly, the present 
invention relates to a swab for retaining test reagents, a method of using 
the same in a test for metals or other specific elements or compounds, and 
a method of making the same. 
BACKGROUND OF THE INVENTION 
Contamination of the environment has been increasing steadily for years as 
the use of metals, chemicals, pesticides, and bacterial organisms has 
increased. Even though the toxicity of various metals has been known for 
centuries, it is only recently that there has been a serious increase in 
interest in minimizing human exposure to such metals. Current public 
awareness of such pollutants and their associated hazards has created a 
consumer demand for products that are capable of determining the presence 
of unwanted and potentially dangerous materials. 
Some of the more toxic metals include lead, cadmium, mercury, barium, 
chromium and beryllium. Lead, in particular, has been subject to much 
attention due to its presence in articles or paints commonly found in the 
home. See, for example, "A Simple Direct Estimation of 
Ultramicroquantities of Lead in Drinking Water Using Sodium Rhodizonate" 
by E. Jungreis and M. Nechama, Microchemical Journal, vol. 34, pp. 219-221 
(1986); U.K. Patent Application No. 2 025 047 A; "A Simplified Method for 
Detection of Lead Contamination of Soil" by J. Preer and G. Murchison, 
Jr., Environmental Pollution (Series B), vol. 12, pp. 1-13; and "A Spot 
Test for Detection of Lead in Paint" by J. Sayre and D. Wilson, J. 
Pediatrics. vol. 46, pp. 783-785 (1970). 
As the titles of some of the prior art publications indicate, there is a 
recognized need in the industry for a simple or simplified test or method 
for determining the presence of lead. However, as will become apparent 
from the remaining descriptions of the prior art, prior to the present 
invention, an effective and simple test for lead had not been developed. 
In a popular prior art method of detecting lead in paint, sodium sulfide 
(Na.sub.2 S) is reacted with lead to form lead sulfide (PbS), a black 
precipitate. The presence of lead is thus confirmed by the appearance of 
the black precipitate, lead sulfide. This method has several 
disadvantages: (1) the sodium sulfide is potentially toxic, especially to 
young children; (2) the black precipitate is difficult to see on dark 
surfaces; (3) the sodium sulfide releases volatile hydrogen sulfide 
(H.sub.2 S), which has a noxious odor; and (4) the reagents react with 
many cations to form black precipitates and thus tends to give false 
readings on many metallic surfaces. 
Another common analytical reagent is a metal complexing agent, rhodizonic 
acid. For over forty years, rhodizonic acid and salts thereof have been 
used as analytical reagents to detect heavy metals, including lead, in 
both qualitative and quantitative analyses. The methodology for using 
rhodizonate dye is based on two types of tests: 
(1) a quantitative determination of heavy metals in solutions using a 
spectrophotometer to obtain quantitative information; and 
(2) qualitative determinations which use filter papers impregnated with the 
reagent. 
In addition, semi-quantitative information can be derived from the use of 
columns packed with silica gel impregnated with rhodizonate dye. See U.K. 
Patent Application No. 2 025 047 A. 
The Macherey-Nagel Company (Duren, Federal Republic of Germany) 
manufactures a test paper for the determination of lead under the 
trademark PLUMBTESMO. The PLUMBTESMO strips comprise a heavy filter paper 
with a reagent impregnated therein. To test for lead in a solution, a 
strip is dipped into the solution, and observed for a color change that 
indicates the presence of lead. The PLUMBTESMO strips can also be used to 
detect lead deposits in motor vehicle tailpipes. 
The instruction sheet that is distributed with the PLUMBTESMO strips 
indicates that the PLUMBTESMO strips may be used to detect the presence of 
lead on a degreased surface. However, the instruction sheet impliedly 
recognizes that the PLUMBTESMO strips are not entirely satisfactory for 
testing for the presence of lead on a surface. Specifically, the 
instruction sheet indicates that the PLUMBTESMO strip may have to be held 
firmly against a test surface for as long as fifteen minutes before an 
indication of lead develops. Clearly, for nonprofessional, household use, 
a test strip that must be held firmly for fifteen minutes is entirely 
unsatisfactory in that many users will become impatient after only a few 
minutes and will discontinue the application of the PLUMBTESMO strip 
against the test surface. That type of usage may, of course, result in 
dangerous false readings, leaving the user with the erroneous impression 
that lead is not present when in fact lead may be present. 
A further disadvantage of the PLUMBTESMO strips is that the test operator 
must directly handle the test strips, thus being unnecessarily exposed to 
chemicals. Yet another disadvantage of the PLUMBTESMO strips is that the 
strips are flat and comparatively stiff, and are thus not readily 
conformable to curved or otherwise unusually contoured surfaces, such as 
those that one is likely to encounter on moldings in older houses. 
Thus, it should be clear that the lead tests, known prior to the present 
invention, are not entirely satisfactory. 
Although not a test for lead, U.S. Pat. No. 4,707,450 discloses a 
biological specimen collection and test unit. The teachings of U.S. Pat. 
No. 4,707,450 are quite different from the present invention. In summary, 
U.S. Pat. No. 4,707,450 discloses a specimen collection device that 
utilizes a swab to collect biological specimens for testing after the swab 
has been removed from the specimen collection location. Since lead and 
other metals do not readily collect on a swab when rubbed on a 
metal-containing surface, the disclosed swab is not useful for testing for 
metals. This is especially true because the success of the disclosed swab 
depends upon the removal of a specimen from the collection site for 
subsequent testing. Because metals will not usually collect on the swab, 
the swab will not work well for metals testing. 
Thus, there is a need in the art for a test or method for determining the 
presence of toxic metals, such as lead and cadmium. While lead toxicity is 
better known, cadmium is toxic by inhalation of dust or fume and is a 
carcinogen. Cadmium plating of food and beverage containers has led to 
outbreaks of gastroenteritis or food poisoning. Other metals are just as 
toxic. Thus, a simple test for metals and other toxic substances would 
serve to protect consumers from the toxic effects caused thereby. 
SUMMARY OF THE INVENTION 
Briefly described, the present invention relates to a swab that is 
impregnated with a test reagent such that a test for a specific substance 
can be effected by rubbing the impregnated swab over the surface to be 
tested and then viewing the swab for a reagent reaction. The present 
invention also relates to a method for testing for a metal that includes 
impregnating a swab with a reagent, and rubbing the swab over a surface 
suspected of containing the metal. If the metal is present in the surface, 
a reaction with the metal produces an easily detectable color on the swab 
tip. The present invention also relates to a method of making a swab 
impregnated with a test reagent.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The test swabs of the present invention may be used to detect a variety of 
substances on a variety of surfaces depending on the reagent contained in 
the swab, including but not limited to, paint, ceramics, dust, soil, plant 
leaves, solder, bird cages, etc. The test swabs may be used to determine 
the presence of lead, cadmium, bismuth, mercury, antimony, iron, aluminum, 
selenium, copper or organophosphates. The present invention preferably 
will be used to determine the presence of metals in such surfaces. In the 
most preferred embodiments, the test swabs of the present invention are 
used to determine the presence of lead or cadmium on surfaces. 
The swabs can be made in a variety of formats as shown in the Figures, 
described below. 
Referring now in detail to the drawings, wherein like reference numerals 
refer to like elements throughout, in the embodiments of FIGS. 1 and 2, a 
swab is indicated generally by reference numeral 10. The swab 10 includes 
a stem 12 that is preferably formed from a hollow tube. The stem 12 may be 
made from glass, plastic, or any other suitable material. If plastic is 
used, the composition of the plastic is not critical. However, because 
glass is breakable and because plastic is more easily crimped, plastic is 
preferable to glass. 
In an alternative embodiment of the present invention, a solid stem may be 
used. 
At one end of the stem 12, a ball 14 of absorbent material is affixed. The 
absorbent material may be comprised of any number of materials, including: 
cotton fibers, rayon fibers, dacron fibers, monofilament polyester, 
monofilament nylon, or an open cell structure such as polyurethane foam. 
Table I lists several commercially available swabs, together with the 
source or manufacturer of each swab. 
TABLE I 
__________________________________________________________________________ 
ABSORBENT 
APPROXIMATE 
STICK STICK 
MATERIAL 
DIAMETER MATERIAL 
DIAMETER 
SOURCE 
__________________________________________________________________________ 
Cotton 0.25" Plastic 
3/16" J&J 
Cotton 0.25" Wood Solid CitMed 
Cotton 0.50" Wood Solid CitMed 
Rayon 0.25" Plastic 
3/16" CitMed 
Rayon 0.50" Plastic 
5/16" CitMed 
Dacron 0.25" Plastic 
3/16" CitMed 
Nylon Coventry 
Polyester 
0.25" Plastic 
3/16" Coventry 
Polyester/ 
cellulose Coventry 
Polyurethane Coventry 
Porous Plastic Plastic Interflo 
Foam dauber Metal Super Brush Co. 
Wool dauber 
0.75" Metal Nat'l Novelty Brush 
__________________________________________________________________________ 
Co. 
For purposes of testing for lead, the preferred reagent dye is rhodizonic 
acid. Table II lists various dyes that are acceptable, together with the 
supplier or manufacturer of each. 
TABLE II 
______________________________________ 
DYE SUPPLIER 
______________________________________ 
Rhodizonic acid, potassium salt 
Sigma Chemical Company 
Rhodizonic acid, sodium salt 
Sigma Chemical Company 
Rhodizonic acid, disodium salt 
Sigma Chemical Company 
Rhodizonic acid, disodium salt 
Eastman Kodak Company 
______________________________________ 
No major differences in purity or other analytical criteria were reported 
for similar salts. The above materials all function well in testing for 
the presence of lead, as indicated below. An activator solution, described 
below, typically will be used with the reagent dyes in carrying out 
embodiments of the present invention. 
For purposes of testing for cadmium, the preferred reagent dyes are 
4-nitronaphthalene-diazoamino-azobenzene or 
1-(4-nitrophenyl)-3-(4-phenylazophenyl)triazene. The latter dye may be 
obtained from Aldrich as Cadion. 
Other substances may be tested for using the reagents and activating 
solutions listed in Table III. 
TABLE III 
______________________________________ 
Dye (Reagent which 
Activating 
Metal Reacts with Metal 
Solution Color 
______________________________________ 
Bi Cinchonine - KI 
Dilute acid Orange 
(1%) Red 
Hg (1) Diphenylcar- 
0.2M HNO.sub.3 
Violet 
bazide (1% in 
alcohol) 
(2) Cobalt (II) 
Cobalt (II) Deep 
thiocyanate test 
acetate blue 
Sb (1) Rhodamine B 
Sb.sup.+5 Blue 
(Tetraethyl- nitrite 
rhodamine) 
(2) Phosphomolyb- 
Sb.sup.+3 Blue 
dic acid 
Fe (1) 2,2'-bipyridine 
Thioglycolic Red 
or 1,1' phenanthro- 
acid buffer 
line 
(2) 3-(2-pyridyl)-5, 
1,2,4-triazine, 
Purple 
6-bis(4-phenyl- 
sodium salt 
sulfonic acid) 
Al (1) Aurin tricar- 
NaOH Red 
boxylic acid 
(2) Quinolizarin 
Ammonia, then 
glacial HONC Red 
Se Pyrrole reagent 
0.5M iron (III) 
Green- 
chloride; H.sub.3 PO.sub.4 
Blue 
Organo- 
Phosphomolybdic 
(1) K.sub.2 S.sub.2 O.sub.8 + 
phos- acid formed with 
H.sub.2 SO.sub.4 
phates sodium molybdate 
(2) Ascorbic Blue 
Acid 
Cu (1) Quinolyl 20 g Na acetate 
reagent (0.2 g/l 
10 g K Na tartrate 
in amyl alcohol) 
3 g hydroxyl- 
ammonium Cl 
(all in 100 ml H.sub.2 O) 
(2) Dithiooxamide Dark- 
(1% in acetone) Green 
(Rubeanic acid) 
______________________________________ 
Several granular and particulate solids were tried as diluents or fillers 
for the dyes to be used in the swabs. While fillers are not required, they 
are useful to provide bulk to the dye when the dye is a solid so the dye 
can be placed in the swabs more conveniently since the dye is used in a 
small amount. No filler is needed when the dye to be used is a liquid. All 
could be used as a filler for the dyes used in the test method of the 
present invention, but some exhibited more desirable properties than 
others. The more granular and less sticky solids are preferable to use 
with automatic filling equipment, such as a Kinematics Powder Filling 
Machine, model no. 1700 equipped with a model 3015 filling gun. 
Table IV identifies several fillers and their ease of use with automatic 
filling equipment. 
TABLE IV 
______________________________________ 
FILLER RECOMMENDATION 
______________________________________ 
Alumina, acid Worked well with the machine 
and filling gun. 
Talc Worked well with the machine 
and filling gun. 
Silicic acid Formed a plug, but worked with 
the machine and filling gun. 
Glass beads Formed a plug, but worked with 
the machine and filling gun. 
Polyvinylpyrrolidone 
Not recommended for use with 
the filing equipment. 
______________________________________ 
The rhodizonate dye is unstable in an aqueous medium. As a result, 
hygroscopic fillers may retain moisture too avidly and will consequently 
contribute to inactivation of this dye. 
Table V identifies several materials capable of use as a filler for the 
dye, together with comments concerning the suitability of each material. 
TABLE V 
__________________________________________________________________________ 
BULKING AGENT APPEARANCE 
COMMENTS 
__________________________________________________________________________ 
Alumina 
WB-2, basic Loose, sandy 
Mixes well; hygroscopic, fills 
tube easily. 
WA-1, acidic Loose Mixes well; hygroscopic, fills 
tube easily. 
WN-3, neutral Loose Mixes well; hygroscopic, fills 
tube easily. 
Bentonite Particulate 
Colored powder; unsuitable for 
use. 
Cellulose 
SigmaCell 20 Loose Mixes well; fills tube easily. 
SigmaCell 50 Loose Mixes well; fills tube easily. 
Florisil Granular Mixes poorly with dye; fills 
tube easily. 
Fuller's Earth 
Large Pieces 
Particles too large to use. 
Fumed Silica Fluffy Too fluffy; mixes poorly; hard 
to use for filling. 
Glass Beads Sandy Mixes with dye poorly; fills 
tube easily. 
Gum acacia Loose Mixes well; fills tube easily. 
Mannitol Clumpy Hygroscopic, dye mixes well. 
Polyvinylpyrrolidone (PVP) 
Granular; mixes poorly; 
unsuitable for filling machine. 
Silicic acid Loose Dye does not mix well; fills 
tube easily. 
Starch 
Potato* Loose Mixes well; turns dark; does 
not fill easily. 
Wheat Loose Mixes well; does not fill tube 
easily. 
Talc Powder Mixes with dye moderately well; 
fills tube easily. 
Zeolite Fluffy Powder 
Turns blue with the dye. 
Zeolite mixture 
Fluffy Powder 
Turns blue with the dye. 
__________________________________________________________________________ 
*Potato starch is susceptible to oxidation, and turns black on reaction 
with iodine. 
Rhodizonate reacts with potato starch as iodine does. 
Accordingly, alumina (all types), talc, gum acacia, silicic acid, and 
mannitol are all suitable materials for use as a diluent with the dye. 
However, other materials in accordance with the spirit of the present 
invention may be used. 
The swabs 10 are filled through the open end 16 of the stem 12, preferably 
with automatic filling equipment, such as that described above. Once the 
desired quantity of dye and filler 20 is inserted into the swab 10, the 
end 16 of the stem 12 may be crimped as shown at 18 in FIG. 2. 
In another embodiment, the swabs are filled with a dye/filler mixture using 
a Kinematics dispensing machine to fill. Then, the solid filled swabs are 
shaken on a vibrating table to disperse the solid throughout the swab. A 
four inch wooden applicator is inserted into the swab to prevent loss of 
reagent through the open end and a drop of glue from a glue gun then is 
applied to the end of the unit. 
Automatic filling units can be designed by using a metal brace notched with 
the appropriate size holes to ensure that the swabs remain in a fixed 
position during an automatic filling operation. A conveyor belt can move 
these units under a fixed dispensing gun. After the dispensing of the 
solid reagent, the swabs can be sealed by a variety of automatic 
procedures including, melting to close, using pressure to close and 
flattening the plastic handle of the swab. 
In various tests, swabs were filled with 20, 30, 40, and 80 mg. of the dye 
and filler. In such tests, the ratios of filler to dye were varied between 
0 and 100:1. 
In use, the absorbent ball 14 of the filled swab 10 is wetted with an 
activator solution. A pH level of between about 2.0 and about 3.0 is 
preferable for the lead-rhodizonate reaction. For the lead reaction, a 
buffer generally is used as the activator solution. A pH level of 2.8 for 
the buffer is optimal for the lead-rhodizonate reaction. The wetted 
absorbent ball 14 is then rubbed onto a surface suspected of containing 
lead. If lead is present on the surface, a reaction occurs with the 
rhodizonate dye, thus causing an easily detectable deep pink color to 
appear on the absorbent ball 14 of the swab 10. The test is even sensitive 
enough to detect lead dust on a surface caused by sanding lead-containing 
paint, even after the surface had been vacuumed and washed with trisodium 
phosphate detergent. 
For the cadmium reaction, the activator solution generally will comprise 
sodium tartrate, sodium acetate, sodium citrate, potassium hydroxide or a 
mixture thereof. Additional chelating materials such as EDTA may also be 
present. The pH preferably used for the cadmium reaction is above about 8, 
more preferably above 9. The potassium hydroxide may be used to adjust the 
pH. Bases other than hydroxide, which form insoluble cadmium complexes, 
such as carbonate, might be used. When testing for cadmium, the area to be 
tested is rubbed with the swab containing the reagent and activator 
solution. If the swab becomes pink, cadmium is present. 
INTERFERENCES CAUSED BY OTHER CATIONS 
Many cations form complexes with rhodizonate. However, the specific 
conditions for optimal reaction of most cations are different from those 
required for lead. Only barium and lead form a red or deep pink complex 
under the conditions defined for the swab tests. The color formed by the 
reaction with barium is red-brown and thus to a skilled technician is 
distinguishable from the color formed during the reaction with lead. 
However, to avoid confusion, the reaction with barium can be distinguished 
from the reaction with lead with the use of sodium sulfide. A drop of 
sodium sulfide (7.5%) on top of the developed pink swab changes the swab 
to black in the presence of lead by forming lead sulfide. The precipitate 
formed by the reaction between sodium sulfide and barium is not black, 
i.e., sodium sulfide does not change to black in the presence of barium 
alone. 
The solid fill method, described above with the use of a Kinematics filling 
machine, is the manufacturing option that is best for preserving the 
stability of the dye reagent. However, alternative manufacturing protocols 
are also available. 
In an alternative method of preparation of a swab for a lead test, an 
aqueous solution of 0.01M rhodizonate (dye) is prepared. The rhodizonate 
solution may be prepared using a tartrate buffer at 2.8 pH. Although that 
pH level is the preferred level for the lead testing reaction, at that pH 
level, the rhodizonate dye is unstable and completely degrades in about 
thirty-six hours. As an alternative, the rhodizonate solution can be 
prepared using water at pH 5 or 6. At that pH level, complete degradation 
of the rhodizonate takes about ninety-six hours. 
The addition of some organic solvents may enhance the stability of the 
aqueous rhodizonate solution. For example, 10 to 20% methanol, ethanol, or 
acetone may be added. 
Within one hour of preparation of the solution, swabs are dipped in the 
solution for thirty seconds to one minute. The swabs are then rapidly 
frozen in acetone/dry ice, or liquid nitrogen, and dried by 
lyophilization. The swabs can then be used in the same manner as the swabs 
that are filled from the inside with a filling machine. The swabs can 
alternatively be dried under heat, although the temperature must be kept 
below 80.degree. C. 
In another embodiment, the swabs can be pretreated by soaking the absorbent 
material of the swabs in a tartrate buffer, pH 2.8, or any other buffer 
with a pH preferably between 2 and 3. The soaked swabs are then dried 
under heat. 
Since other cations might interfere with a test for lead, the swab can also 
be presoaked in a buffer containing EDTA for about one minute in order to 
clean other possible interfering cations from the swab prior to the test. 
The EDTA can be included in the buffer described in the preceding 
paragraph. 
In one preferred embodiment, the swab of the present invention is prepared 
as a cartridge swab. In this embodiment, a device for testing for a 
substance or metal on a surface comprises a cartridge, two compartments 
within the cartridge wherein one compartment contains a reagent that 
reacts with the metal and the other compartment contains an activating 
solution, and an absorbent ball of material mounted at one end of the 
cartridge. The reagent and activating solution are combined and mixed 
within the cartridge before the device is used. This embodiment can take 
several forms, some of which are shown in FIGS. 3-6. 
The simplest design of the cartridge swab is a system wherein two 
compartments are used. One compartment contains an activator solution and 
the other contains a dye. When testing for lead, the activator solution 
will be the buffer solution described above and the dye will be 
rhodizonate dye. When testing for cadmium, the activator solution will be 
sodium tartrate, sodium acetate, sodium citrate, potassium hydroxide or 
mixtures thereof, and the dye will be 
4-nitronaphthalene-diazoamino-azo-benzene or 
1-(4-nitrophenyl)-3-(4-phenylazophenyl)triazene. The absorbent ball 
mounted at one end of the cartridge swab may be attached when the 
cartridge swab is prepared or it may be attached when the cartridge swab 
is to be used. 
FIG. 3 shows an embodiment of a cartridge swab wherein a breakable 
cartridge 22 contains a small amount of activator solution. The breakable 
cartridge 22 is inserted into a plastic holder or cartridge 24 into which 
dry dye powder 26 plus any additives required for the test desired has 
been dispensed. The swab tip 14 generally will be placed on the cartridge 
24 before the cartridge 24 is filled with dry dye powder 26 and the 
breakable cartridge 22. When the cartridge swab is to be used, the 
breakable cartridge 22 is broken and the activator solution mixes with the 
dye powder and wets the swab tip. The swab tip then can be rubbed over the 
surface to be tested. 
FIG. 4 shows an embodiment of a cartridge swab wherein a small breakable 
cartridge 28 is prepared containing dry dye powder plus any additives 
required for the desired test. The cartridge 28 is placed inside another 
breakable cartridge 32 large enough to hold cartridge 28 and sufficient 
activating solution 34 to execute the desired test. The breakable 
cartridge is broken when the test is to be performed and the activating 
solution mixes with the dye and wets the swab tip which can be rubbed over 
the surface to be tested. 
FIG. 5 shows an embodiment of the cartridge swab wherein two breakable 
cartridges are used side by side in a larger cartridge. Breakable 
cartridges 36 and 38 will contain either activating solution or dye. The 
cartridges are broken together when the test is to be performed and the 
activating solution mixes with the dye and wets the swab tip which can be 
rubbed over the surface to be tested. 
FIG. 6 shows an embodiment of the cartridge swab wherein two breakable 
cartridges 36 and 38 are used in an end to end format inside a larger 
cartridge 40 which has a swab tip 14. The cartridges are broken together 
when the test is to be performed and the activating solution mixes with 
the dye and wets the swab tip which can be rubbed over the surface to be 
tested. 
The swab tips on the cartridge swabs can be the same type of swabs 
described above for use on the stick type swabs. 
The cartridges which are used to hold the breakable cartridges containing 
the reactants for the desired test can be nonbreakable or squeezable 
containers. For example, a squeezable cartridge similar to a toothpaste 
tube may be used. The breakable cartridges are placed inside the 
squeezable cartridge and the end is closed with a fibrous or porous swab 
tip. The swab tip optionally may have a pointed tip which breaks the 
cartridges contained within the tube. The squeezable cartridge is 
squeezed, breaking the cartridges within the squeezable cartridge and 
mixing the reagents. The reagents wet the swab tip which can then be 
rubbed over the surface to be tested. 
Although a filter paper test is not efficient for testing for lead, as 
described above, such a test may be used for other metals, such as 
cadmium. For the filter paper format, filter paper may be soaked in an 
activator solution or the activator solution can be added later. To 
conduct the test, the activator soaked filter paper is wetted with water 
and placed on the test surface for about 1 minute to overnight depending 
on the level of detection required. A drop of dye solution is placed on 
the test paper and a color change indicates the presence of the metal to 
be detected. If the activator solution is not on filter paper, it should 
be added prior to adding the drop of dye. If the dye solution is stable, 
it can be prepared in the activator solution format. When testing for 
cadmium, the activator solution and dye is as stated above. 
EXAMPLES 
TESTS TO DETERMINE PREFERRED RATIOS OF FILLER TO DYE 
Examples I through XIII 
In examples I through XIII, swabs were obtained from CitMed having an 
absorbent ball of 0.50 inch diameter made from rayon fibers. The swab stem 
was a 3/16 inch hollow plastic tube. Alumina (WA-1, acidic) was used as an 
inert diluent, and rhodizonate dye, disodium salt (from the Sigma Chemical 
Company) was used as the dye. The inert diluent was mixed with the dye in 
the ratios set forth in Table V. Table V also lists the quantity of fill 
used in the swab, together with the test results. 
In performing the above examples, the swabs, after being filled with the 
above-designated quantities of the above-designated ratios of filler and 
dye, were wetted with 1.5 ml. of 0.2M tartrate buffer, pH 2.8. The swabs 
were then rubbed on wood that had been previously painted with 0.5% 
lead-containing paint. In most instances, a positive reaction was clearly 
visible within seconds, almost always within less than one minute. A 
positive reaction is indicated by a deep pink color appearing on the 
absorbent ball of the swab. 
TABLE VI 
______________________________________ 
RATIO 
ALUMINA:DYE 
FILL(mg) REACTIVITY 
______________________________________ 
100:1 40 All positive 
100:1 80 All positive 
80:1 40 All positive 
80:1 80 All positive 
60:1 40 All positive 
60:1 80 All positive 
40:1 30 All positive 
40:1 40 All positive 
40:1 80 All positive 
20:1 40 All positive 
20:1 80 All positive 
10:1 40 50% positive - too much dye 
5:1 40 no reaction - too much dye 
______________________________________ 
Example XIV 
A mixture of alumina (acidic) and rhodizonate dye, sodium salt at a ratio 
of 40:1 was suspended in 0.2M tartrate buffer, pH 2.8. The following 
swabs: cotton, 6" plastic rod, from CitMed; rayon, 6" plastic rod, from 
CitMed; and dacron, 6" plastic rod, from CitMed, were individually dipped 
in the suspension. The dipped swabs were then rubbed on a piece of wood 
painted with a 0.5% lead-containing paint. The suspension lost activity 
rapidly, losing its ability to detect lead within one minute. It is 
interesting to note that the suspension lost activity more rapidly when 
soaked onto the swab, as in this example, than when the mixture was filled 
through the center of the swab and then wetted with the buffer. 
Example XV 
A mixture of alumina (acidic) and rhodizonate dye, sodium salt at a ratio 
of 20:1 was suspended in 0.2M tartrate buffer, pH 2.8. The following 
swabs: cotton, 6" plastic rod, from CitMed; rayon, 6" plastic rod, from 
CitMed; and dacron, 6" plastic rod, from CitMed, were individually dipped 
in the suspension. The dipped swabs were then rubbed on a piece of wood 
painted with a 0.5% lead-containing paint. The suspension decayed at a 
rate slower than the suspension used in example XIV. Activity was still 
observed after five minutes. 
Example XVI 
A mixture of mannitol and rhodizonate dye, sodium salt at a ratio of 20:1 
was suspended in 0.2M tartrate buffer, pH 2.8. The following swabs: 
cotton, 6" plastic rod, from CitMed; rayon, 6" plastic rod, from CitMed; 
and dacron, 6" plastic rod, from CitMed, were individually dipped in the 
suspension. The dipped swabs were then rubbed on a piece of wood painted 
with a 0.5% lead-containing paint. The suspension decayed at a rate slower 
than the suspension used in example XIV. Activity was still observed after 
five minutes. 
TESTS TO DETERMINE SENSITIVITY OF REAGENT 
Example XVII 
To determine the sensitivity of the test, a contoured wood molding strip 
was divided into ten different sections. Each section was painted with 
latex paint that was mixed with a different quantity of lead, ranging from 
0.1% to 1.0%. The following diagram illustrates the various ratios used: 
EQU 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8% 0.9% 1.0% 
A swab with a 0.5 inch diameter absorbent ball made from rayon fibers and a 
5/16 inch hollow plastic stem was filled with 40 mg. of alumina (WA-1, 
acidic) and rhodizonate dye, disodium salt (from the Sigma Chemical 
Company) in a 40:1 ratio. A 1.5 ml. solution of 0.2M tartrate buffer, pH 
2.8 was used as the developing agent. Within less than thirty seconds, a 
deep red color developed on the swab after rubbing the treated swab on the 
wood section painted with 0.4% lead-containing paint. Similarly treated 
swabs had equal or better results on all sections of the wood having a 
higher percentage of lead in the paint. 
TESTS TO COME RESULTS OF SWAB WITH RESULTS OF FILTER PAPER 
Example XVIII 
For comparison with the swab test set forth in example XVII above, a 
similar test was conducted using Whatman 3 mm. filter paper. A solution 
was prepared using 40 mg. of alumina (WA-1, acidic) and rhodizonate dye, 
disodium salt (from the Sigma Chemical Company) in a 40:1 ratio and a 1.5 
ml. solution of 0.2M tartrate buffer, pH 2.8. The filter paper was dipped 
into the solution, allowing the solution to completely saturate the filter 
paper. The saturated filter paper was then promptly rubbed over the wood 
painted with lead-containing paint. 
The filter papers never clearly turned pink even when used on the sections 
of wood having high concentrations of lead. Hints of pink were 
occasionally visible at the edges of the filter paper; however, 
interpretation was very difficult. The wood underneath the filter paper 
did become pink, but this pink color was only visible on the light colored 
paint, not on the dark paint. On the contoured wood surfaces it was 
difficult to make good contact between the filter paper and the contoured 
surfaces. 
Example XIX 
A swab with a 0.5 inch diameter absorbent ball made from rayon fibers and a 
5/16 inch hollow plastic stem was filled with 40 mg. of alumina (WA-1, 
acidic) and rhodizonate dye, disodium salt (from the Sigma Chemical 
Company) in a 40:1 ratio. A 1.5 ml. solution of 0.2M tartrate buffer, pH 
2.8 was used as the developing agent, i.e., the swab was prepared exactly 
as set forth in example XVII, above. This time the swab was rubbed on 
lead-glazed ceramic dishes. Within less than thirty seconds, the tip of 
the swab was obviously pink. 
Example XX 
A solution was prepared using 40 mg. of alumina (WA-1, acidic) and 
rhodizonate dye, disodium salt (from the Sigma Chemical Company) in a 40:1 
ratio and a 1.5 ml. solution of 0.2M tartrate buffer, pH 2.8. A piece of 
Whatman 3 mm. filter paper was dipped into the solution, allowing the 
solution to completely saturate the filter paper, i.e., the filter paper 
was prepared in accordance with the method set forth above in example 
XVIII. The treated filter paper was rubbed on the lead-glazed ceramic 
dishes used in example XIX. No detectable color was observed on the filter 
paper after several minutes of contact with the lead-glazed dishes. 
Example XXI 
Plain untreated swabs having a rayon fiber absorbent ball of 0.5 inch 
diameter on a 5/16 inch hollow plastic stem were soaked in a solution of 
40 mg. of alumina (WA-1, acidic) and rhodizonate dye, disodium salt (from 
the Sigma Chemical Company) in a 40:1 ratio and a 1.5 ml. solution of 0.2M 
tartrate buffer, pH 2.8, i.e., the same solution used in examples XVIII 
and XX. When the swabs were then rubbed on the lead-glazed ceramic dishes, 
a clear positive result was easy to read. 
Example XXII 
Plain untreated swabs having a rayon fiber absorbent ball of 0.5 inch 
diameter on a 5/16 inch hollow plastic stem were soaked in a solution of 
40 mg. of alumina (WA-1, acidic) and rhodizonate dye, disodium salt (from 
the Sigma Chemical Company) in a 40:1 ratio and a 1.5 ml. solution of 0.2M 
tartrate buffer, pH 2.8, i.e., the same solution used in examples XVIII, 
XX, and XXI. When the swabs were then rubbed on the wood painted with at 
least 0.4% lead-containing paint, a clear positive result was easy to 
read. 
From the results of examples XVII through XXII, it is clear that the swab 
is far superior to the filter paper for effecting a test for the presence 
of lead using rhodizonate dye. 
COMISON OF DIFFERENT TYPES OF SWABS 
Example XXIII 
A mixture of alumina (acidic) and rhodizonate dye, sodium salt at a ratio 
of 40:1 was filled into the following swabs: cotton, 6" plastic rod, from 
CitMed; rayon, 6" plastic rod, from CitMed; and dacron, 6" plastic rod, 
from CitMed. About 3/16" to 1/4" of material was filled in each swab. The 
swabs were then wetted with tartrate, sodium salt and rubbed on a wood 
board painted with a 0.5% lead-containing paint. 
There were no notable differences in color intensity among the swabs made 
of cotton, rayon, or dacron. The dacron and rayon swabs wetted well, 
whereas the first few drops of buffer beaded on the surface of the cotton. 
During the rubbing stage, the dacron swab did not hold up as well as the 
cotton and rayon swabs. 
Example XXIV 
A mixture of mannitol and rhodizonate dye, sodium salt at a ratio of 20:1 
was suspended in 0.2M tartrate buffer, pH 2.8. The following swabs: 
cotton, 6" plastic rod, from CitMed; rayon, 6" plastic rod, from CitMed; 
dacron, 6" plastic rod, from CitMed; molded foam from Coventry Mfg. Co.; 
spun foam from Coventry Mfg. Co.; and 3" cotton tipped swabs from Johnson 
& Johnson, were individually dipped in the suspension. The dipped swabs 
were then rubbed on a piece of wood painted with a 0.5% lead-containing 
paint. The foam materials did not wet well, and little or no color 
formation was observed on the material or the wood. The cotton, rayon, and 
dacron swabs had intense color on the fibers. Under a microscope it 
appeared that the fibers had been dyed. It did not appear as though a 
precipitate had been formed and trapped by the fibers. However, at high 
concentrations of lead and dye, some precipitate may form. The precipitate 
is not necessary in order to detect a reaction. 
The size of the absorbent ball on the swab also had little apparent effect 
on the test results. 
Example XXV 
A swab with a hollow stem is filled with 30 mg of a mixture of 
4-nitronaphthalene-diazoamino-azo-benzene and an inert filler, alumina in 
ratios as shown in Table VI. The swab tip is wetted with an activator 
solution containing sodium potassium tartrate, sodium acetate, sodium 
citrate at pH 8.5. The area to be tested is rubbed with the swab. If 
cadmium is present, the swab becomes pink. 
Example XXVI 
One crushable cartridge is filled with 30 mg Cadion, 
(1-(4-nitrophenyl)-3-(4-phenylazophenyl)triazene) and talc. Another 
breakable cartridge is filled with 0.5 ml activator solution which is a 
mixture of sodium tartrate, sodium acetate and sodium hydroxide. The pH of 
the activator solution is adjusted to be basic at a pH greater than 9. 
The two cartridges are placed inside a larger cartridge having a swab tip 
at one end. When ready to use, the breakable cartridges are broken and the 
unit is shaken to ensure good mixing. The swab tip is rubbed over the area 
to be tested and becomes pink if cadmium is present. 
Although only preferred embodiments are specifically illustrated and 
described herein, it will be appreciated that many modifications and 
variations of the present invention are possible in light of the above 
teachings and within the purview of the appended claims without departing 
from the spirit and intended scope of the invention. Specifically, the 
present invention is not limited to tests for the presence of lead or 
cadmium.