[Code of Federal Regulations]
[Title 21, Volume 3]
[Revised as of April 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR172.250]
[Page 42-44]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN
SERVICES (CONTINUED)
PART 172_FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN
CONSUMPTION--Table of Contents
Subpart C_Coatings, Films and Related Substances
Sec. 172.250 Petroleum naphtha.
Petroleum naphtha may be safely used in food in accordance with the
following conditions:
(a) The additive is a mixture of liquid hydrocarbons, essentially
paraffinic and naphthenic in nature obtained from petroleum,
(b) The additive is refined to meet the following specifications
when subjected to the procedures described in this paragraph.
(1) Boiling-point range: 175 [deg]F-300 [deg]F.
(2) Nonvolatile residue: 0.002 gram per 100 milliliters maximum.
(3) Ultraviolet absorbance limits, as follows:
------------------------------------------------------------------------
Maximum
absorbance
per
Wavelength (milli-microns) centimeter
optical
pathlength
------------------------------------------------------------------------
280-289..................................................... 0.15
290-299..................................................... .13
300-359..................................................... .08
360-400..................................................... .02
------------------------------------------------------------------------
Analytical Specification for Petroleum Naphtha
general instructions
All glassware should be scrupulously cleaned to remove all organic
matter such as oil, grease, detergent residues, etc. Examine all
glassware, including stoppers and stopcocks, under ultraviolet light to
detect any residual fluorescent contamination. As a precautionary
measure, it is recommended practice to rinse all glassware with purified
isooctane immediately before use. No grease is to be used on stopcocks
or joints. Great care to avoid contamination of petroleum naphtha
samples in handling and to assure absence of any extraneous material
arising from inadequate packaging is essential. Because some of the
polynuclear hydrocarbons sought in this test are very susceptible to
photo-oxidation, the entire procedure is to be carried out under subdued
light.
apparatus
Separatory funnels. 250-milliliter, and 2,000-milliliter capacity,
equipped with tetrafluoroethylene polymer stopcocks.
Erlenmeyer flask. 125-milliliter with 24/40 standard taper neck.
Evaporation flask. 250-milliliter capacity all-glass flask equipped
with 24/40 standard taper stopper having inlet and outlet tubes to
permit passage of nitrogen across the surface of the container liquid to
be evaporated.
Condenser. 24/40 joints, fitted with drying tube, length optional.
Spectrophotometric cells. Fused quartz cells, optical path length in
the range of 5,000 centimeters 0.005 centimeter;
also for checking spectrophotometer performance only, optical path
length in the range 1,000 centimeter 0.005
centimeter. With distilled water in the cells, determine any absorbance
difference.
Spectrophotometer. Spectral range 250-400 m[micro] with spectral
slit width of 2 m[micro] or less; under instrument operating conditions
for these absorbance measurements, the spectrophotometer shall also meet
the following performance requirements:
Absorbance repeatability, 0.01 at 0.4 absorbance.
[[Page 43]]
Absorbance accuracy, \1\ 0.05 at 0.4 absorbance.
---------------------------------------------------------------------------
\1\ As determined by procedure using potassium chromate for
reference standard and described in National Bureau of Standards
Circular 484, Spectrophotometry, U.S. Department of Commerce, (1949).
The accuracy is to be determined by comparison with the standard values
at 290, 345, and 400 millimicrons. The procedure is incorporated by
reference. Copies of the material incorporated by reference are
available from the Center for Food Safety and Applied Nutrition (HFS-
200), Food and Drug Administration, 5100 Paint Branch Pkwy., College
Park, MD 20740, or available for inspection at the National Archives and
Records Administration (NARA). For information on the availability of
this material at NARA, call 202-741-6030, or go to: http://
www.archives.gov/federal--register/code--of--federal--regulations/ibr--
locations.html.
---------------------------------------------------------------------------
Wavelength repeatability, 0.2 millimicron.
Wavelength accuracy, 1.0 millimicron.
Ultraviolet lamp. Long wavelength (3400-3800A[deg]).
reagents
Isooctane (2,2,4-trimethylpentane). Use 180 milliliters in a 250-
milliliter Erlenmeyer flask, add 1 milliliter of purified n-hexadecane,
insert the head assembly, allow nitrogen gas to flow into the inlet tube
and connect the outlet tube to a solvent trap and vacuum line in such a
way as to prevent any back flow of condensate into the flask. The
contents of the flask are evaporated on a steam bath until 1 milliliter
of residue remains. Dissolve the 1 milliliter of hexadecane residue in
isooctane and make up to 25 milliliters. Determine the absorbance in a
5-centimeter path length cell compared to isooctane as reference. The
absorbance should not exceed 0.01 per centimeter path length between
280-400 m[micro]. If necessary, isooctane may be purified by passage
through a column of activated silica gel (Grade 12, Davidson Chemical
Co., Baltimore, Md., or equivalent) or by distillation.
Methyl alcohol, A.C.S. reagent grade. Use 10 milliliters and proceed
as with isooctane. The absorbance per centimeter of path length should
be 0.00 between 280-400 m[micro]. Methyl alcohol may be purified by
simple distillation or by refluxing in the presence of potassium
hydroxide (10 grams/2 liters) and zinc dust (25 grams/2 liters) for 3
hours followed by distillation.
n-Hexadecane, 99 percent olefin-free. Dilute 1.0 milliliter of n-
hexadecane to 25 milliliters with isooctane and determine the absorbance
in a 5-centimeter cell compared to isooctane as reference between 280-
400 m[micro]. The absorbance per centimeter path length shall not exceed
0.00 in this range. Purify, if necessary, by percolation through
activated silica gel or by distillation.
Sodium borohydride. 98 percent.
Water. All distilled water must be extracted with isooctane before
use. A series of three successive extracts of 1.5 liters of distilled
water with 100-milliliter portions of isooctane is satisfactory.
procedure
Determination of ultraviolet absorbance. Add a 25-milliliter aliquot
of the hydrocarbon solvent together with 1 milliliter of hexadecane to
the 125-milliliter Erlenmeyer flask. While flushing with nitrogen,
evaporate to 1 milliliter on a steam bath. Nitrogen is admitted through
a 81-milliliter outer-diameter tube, drawn out
into a 21-centimeter long and 10.5-millimeter inner-diameter capillary tip. This is
positioned so that the capillary tip extends 4 centimeters into the
flask. The nitrogen flow rate is such that the surface of the liquid is
barely disturbed. After the volume is reduced to that of the 1
milliliter of hexadecane, the flask is left on the steam bath for 10
more minutes before removing. Add 10 milliliters of purified isooctane
to the flask and reevaporate the solution to a 1-milliliter volume in
the same manner as described above, except do not heat for an added 10
minutes. Repeat this operation twice more. Let the flask cool.
Add 10 milliliters of methyl alcohol and about 0.3 gram of sodium
borohydride. (Minimize exposure of the borohydride to the atmosphere; a
measuring dipper may be used.) Immediately fit a water-cooled condenser
equipped with a 24/40 joint and with a drying tube into the flask, mix
until the sodium borohydride is dissolved, and allow to stand for 30
minutes at room temperature, with intermittent swirling. At the end of
this time, disconnect the flask and evaporate the methyl alcohol on the
steam bath under nitrogen until sodium borohydride begins to drop out of
solution. Remove the flask and let it cool.
Add 6 milliliters of isooctane to the flask and swirl to wash the
crystalline slurry. Carefully transfer the isooctane extract to a 250-
milliliter separatory funnel. Dissolve the crystals in the flask with
about 25 milliliters of distilled water and pour this also into the
separatory funnel. Adjust the water volume in the separatory funnel to
about 100 milliliters and shake for 1 minute. After separation of the
layers, draw off the aqueous layer into a second 250-milliliter
separatory funnel. Transfer the hydrocarbon layer in the first funnel to
a 25-milliliter volumetric flask.
Carefully wash the Erlenmeyer flask with an additional 6 milliliters
of isooctane, swirl, and transfer to the second separatory funnel. Shake
the funnel for 1 minute. After separation of the layers, draw off the
aqueous layer into the first separatory funnel. Transfer the
[[Page 44]]
isooctane in the second funnel to the volumetric flask. Again wash the
Erlenmeyer flask with an additional 6 milliliters of isooctane, swirl,
and transfer to the first separatory funnel. Shake the funnel for 1
minute. After separation of the layers, draw off the aqueous layer and
discard. Transfer the isooctane layer to the volumetric flask and adjust
the volume to 25 milliliters of isooctane. Mix the contents well, then
transfer to the first separatory funnel and wash twice with 50-
milliliter portions of distilled water. Discard the aqueous layers after
each wash.
Determine the ultraviolet absorbance of the isooctane extract in 5-
centimeter path length cells compared to isooctane as reference between
280-400 m[micro]. Determine a reagent blank concurrently with the
sample, using 25 milliliters of purified isooctane instead of a solvent
sample and measuring the ultraviolet absorbance of the blank between
280-400m[micro].
The reagent blank absorbance should not exceed 0.04 per centimeter
path length between 280-289 m[micro]; 0.020 between 290-359 m[micro];
and 0.010 between 360-400 m[micro].
Determination of boiling-point range. Use ASTM method D86-82,
``Standard Method for Distillation of Petroleum Products,'' which is
incorporated by reference. Copies may be obtained from the American
Society for Testing Materials, 100 Barr Harbor Dr., West Conshohocken,
Philadelphia, PA 19428-2959, or may be examined at the National Archives
and Records Administration (NARA). For information on the availability
of this material at NARA, call 202-741-6030, or go to: http://
www.archives.gov/federal--register/code--of--federal--regulations/ibr--
locations.html.
Determination of nonvolatile residue. For hydrocarbons boiling below
121 [deg]C, determine the nonvolatile residue by ASTM method D1353-78,
``Standard Test Method for Nonvolatile Matter in Volatile Solvents for
Use in Paint, Varnish, Lacquer, and Related Products;'' for those
boiling above 121 [deg]C, use ASTM method D381-80, ``Standard Test
Method for Existent Gum in Fuels by Jet Evaporation,'' which methods are
incorporated by reference. Copies may be obtained from the American
Society for Testing Materials, 100 Barr Harbor Dr., West Conshohocken,
Philadelphia, PA 19428-2959, or may be examined at the National Archives
and Records Administration (NARA). For information on the availability
of this material at NARA, call 202-741-6030, or go to: http://
www.archives.gov/federal--register/code--of--federal--regulations/ibr--
locations.html.
(c) Petroleum naphtha containing antioxidants shall meet the
specified ultraviolet absorbance limits after correction for any
absorbance due to the antioxidants. Petroleum naphtha may contain
antioxidants authorized for use in food in an amount not to exceed that
reasonably required to accomplish the intended effect or to exceed any
prescribed limitations.
(d) Petroleum naphtha is used or intended for use as a solvent in
protective coatings on fresh citrus fruit in compliance with Sec.
172.210.
[42 FR 14491, Mar. 15, 1977, as amended at 47 FR 11835, Mar. 19, 1982;
49 FR 10104, Mar. 19, 1984; 54 FR 24896, June 12, 1989]
Additives that reference this regulation: |
