BACKGROUND

The present invention relates generally to the field of distinguishing chemicals from one another through the use of other chemical taggants or additives, in quantities ranging from parts per million to 5% of the total sample.

In one embodiment, adding, detecting, and then removing taggant, in a certifiable fashion, requires extensive knowledge of the properties of a feedstock and of potential taggants. Spectroscopy is the preferred analytical detection technique, because it is fast and nondestructive, while still providing a detailed and definitive characterization of the chemical composition of the sample. Of the available spectroscopic options, infrared, near-infrared, ultraviolet, visible and Raman are useful choices. It is also possible to employ multiple analytical techniques on the same tagged sample.

As noted by Robinson, Skelly Frame, and Frame (2004), the primary absorption bands seen in the near-infrared (NIR) region of the electromagnetic spectrum are:

• C— H bands between 2100 and 2450 nm and between 1600 and 1800 nm

• N— H 1450 and 1550 nm and 2800 and 3000 nm

• O— H 1390 and 1450 nm and 2700 and 2900 nm

Bands for S— H, P— H, C==N. and C==0 also appear in the NIR region. Water has several distinct absorption peaks at 1400, 1890, 1700 and 2750 nm. These bands enable the determination of hydrocarbons, amines, polymers, fatty acids, proteins, water, and other compounds in a wide variety of materials.

Monoethylene glycol (MEG) is one feedstock that can be tagged using the techniques described herein. MEG is visible in the infrared (IR), near-infrared (NIR), and ultraviolet (UV) regions of the electromagnetic spectrum as follows: IR: Peaks (negative) at 3320 cm ¹ , 2880 cm ¹ , 2940 cm ¹ , 1650 cm ¹ , 1450 cm ¹ , 1100 cm ¹ , 1050 cm ¹ , 930 cm ⁴

NIR: 2100 nm peak; the 1400 nm region contains the 1st overtone of the O-H stretch in water and hydroxyl, as shown above for water and ethylene glycol. The large peak near 2100 nm is a combination of O-H and C-H in the glycol.

Notice that this pure glycol lacks an appreciable peak near 1900 nm where molecular water absorbs. Smaller peaks are seen at 1600 nm and 1720 nm.

UV: (ASTM standard E2193). Knowledge of the ultraviolet transmittance of monoethylene glycol is required to establish whether the product meets the requirements of its quality specifications. Dissolved oxygen in organic solvents, such as MEG, forms complexes that shift the solvent absorption from the vacuum ultraviolet range into the measurable UV range (near 190 to 250 nm). Monoethylene glycol has a UV absorption peak at 180 nm. For MEG-oxygen complexes, this peak is shifted to a longer wavelength, thus increasing the absorbability at 220 nm.

MEG has Raman peaks as well, at 900, 1100, 1300, 1400 cm ¹ .

SUMMARY

The current invention makes it possible to use spectroscopy to tag and then test a chemical or commodity to determine its source or type.

This represents a significant improvement over existing methods because it is rapid, convenient, inexpensive, and requires minimal labor. One current method is for the receiving company to perform tests using Carbon- 14 to prove bio-sourcing.

The field of the invention pertains to the use of sophisticated spectroscopy methods and spectral patterns to detect chemical taggants in samples. More specifically, the invention pertains to the detection of taggant in a regulated product or precursor, or "feedstock." Even more specifically, the invention pertains to the use of a spectral pattern to identify taggant in a regulated product or precursor. In a preferred embodiment, even more specifically, the invention pertains to the use of a spectral pattern in a regulated product or precursor subject to differing tax or tariff treatment based on its source or type.

The invention includes taggant or taggants, including those that are either safe additives or can be thermally removed in subsequent processing, added to a sample to distinguish source or type, for tariff, tax, chain-of-custody or regulatory purposes, using a spectrometer or other chemical analyzer, preferably portable, in a customs or other monitoring task.

In a preferred embodiment, the sample is a plastic or plastic ingredient with a biological source, and the taggant indicates that it is not subject to a particular tariff when present and subject to said tariff when absent. The alert reader will recognize that chain of custody can be affirmed through the use of the taggants as well.

Taggant selection of necessity takes into account the spectral profile of the feedstock, because otherwise the taggant' s peaks will not be detectable against the background of similar peaks in the feedstock. Continuing with the example of MEG, the candidates for taggant include isoprenes, monoterpenes, aldehydes, ketones, DMSO, acetonitrile, and essential oils, including mixtures thereof.

In the case where taggant is removed as a consequence of further feedstock processing, that removal can be facilitated by selecting the taggant or taggants from the set of chemicals that evaporate off at a temperature lower than the temperature of subsequent processing of the sample.

In the preferred embodiment, the taggant' s peaks are sufficiently detectable and the spectrometer is sufficiently powerful to enable quantification of the taggant using

spectroscopy. This in turn enables a vastly greater number of potential taggants and taggant combinations, in the sense that 2% Taggant A vs. 0.5% Taggant A become separate and distinguishable tagging options. In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described with respect to a drawing in several figures. Where possible, like elements among the figures are denoted with like reference numerals.

Fig. 1 portrays chemical taggant and feedstock.

Fig. 2 shows the addition of taggant to feedstock to created tagged feedstock .

Fig. 3 shows a sampling step in which a spectrometer tests the feedstock to determine whether it has been chemically tagged.

Fig. 4 shows the steps of a method according to the invention, including tagging feedstock, detecting taggant, and using the feedstock for creation of a product.

DETAILED DESCRIPTION

Fig. 1 shows chemical taggant 51 and feedstock 52.

Fig. 2 shows the addition of taggant 51 to created tagged feedstock 54.

Fig. 3 shows a sampling step in which a spectrometer in diffuse reflectance mode 60 sends light to the surface of the tagged feedstock 54, where certain wavelengths are absorbed and others reflected to create a characteristic spectrum 61 of the tagged feedstock 54 that distinguishes it from untagged feedstock 52. Fig. 4 shows the steps of a method according to the invention, including:

formulating a chemical taggant 51 for a feedstock 52, the taggant 51 consisting of at least one non-essential additive 53 that dissolves or disperses homogeneously in the feedstock 52, transporting the tagged feedstock 54 from a Point A 55 to a Point B 57, testing for the presence of the taggant 51 at a third location 58 between Point A 55 and Point B 57, annunciating the result of the test to a human user 59 and/or regulatory body 61, treating the feedstock 54 to eliminate the taggant 51, and making use of the resulting feedstock 60 in a further chemical or physical transformation.

Fig. 4 includes a variant in which the step of making use of the feedstock 54 in a further chemical or physical transformation eliminates the taggant 51.

Fig. 4 also includes a variant in which the step of annunciating the result of the test to a human user 59 and/or regulatory body 61 is automated to eliminate the need for human intervention.

It will thus be appreciated that a method may be carried out with respect to a feedstock, the method comprising the steps of: formulating a chemical taggant for a feedstock, the taggant consisting of at least one non-essential additive that dissolves or disperses homogeneously in the feedstock, transporting the tagged feedstock from a first geographic location to a second geographic location by way of a third geographic location, the second location non- identical to the first location and the third location non-identical to the first location and non-identical to the second location; testing for the presence of the taggant at the third location; annunciating the result of the test to a human user; treating the feedstock to eliminate the taggant; and making use of the feedstock in a further chemical or physical transformation. The step of making use of the feedstock in a further chemical or physical transformation may comprise eliminating the taggant. The step of annunciating the result of the test to a human user may be automated thereby eliminating any need for human intervention. The testing for presence of the taggant may comprise using a spectrometer or a chemical analyzer, preferably portable. The third location is may be a customs inspection location, where the first location and second location are in different countries. The feedstock may be of interest because it has a biological source rather than a fossil fuel source.

The making use of the feedstock in a further chemical or physical transformation may comprise heating the feedstock to a predetermined temperature, and the heating of the feedstock to the predetermined temperature causes the taggant to evaporate.

The taggant may be selected from the Food and Drug Administration list of materials "Generally Recognized as Safe". The taggant may be a fragrance or essence. It may be selected from the set consisting of isoprenes, monoterpenes, aldehydes, ketones, DMSO, acetonitrile, and essential oils. The taggant may be used in quantities ranging from one part per million to 5% of the total sample.

A typical application is where the further chemical or physical transformation comprises blow molding a drink bottle or forming a parison for later use in blow molding a drink bottle.

EXEMPLARY APPLICATIONS AND USES

To test a single sample for the presence of taggant, a sample is placed within the line of sight of the spectrometer. No reagents need to be added. The user presses a start button. The spectrometer scans the sample and compares the results to a set of preprocessed control samples, both those containing taggant and those containing untagged sample material.

Results are available immediately, right at the point of sample collection. In one preferred embodiment, detection employs automated sampling for multiple samples using a dispersive 785-nanometer Raman spectrometer. In another preferred embodiment, detection employs a near-infrared spectrometer. In another preferred embodiment, detection employs a FT-IR spectrometer. In another preferred embodiment, detection employs a transmission IR spectrometer.

In one preferred embodiment, chemical taggants are added to a sample to distinguish source or type, for tariff, tax, or regulatory purposes. For example, polyethylene terephthalate (PET) is made out of 32.2% (by weight) monoethylene glycol (MEG) and 67.8% (by weight) purified terephthalic acid (PTA), combined in an esterification reactor and converted to polymer in a polycondensation reactor. The MEG may be petroleum-derived or created from a biological source; biological sourcing tends to be encouraged by governments and subject to lower tariffs. Distinguishing bio-MEG from petroleum-sourced MEG, however, is chemically very difficult without the taggants described herein.

The chemical taggants are detected, using a spectrometer or other chemical analyzer, preferably portable, in a customs or other monitoring task. Specifically, a method is described for tagging a plastic such as polyethylene terephthalate (PET) or plastic ingredient such as monoethylene glycol (MEG) that has a biological source, where the taggant indicates that it is not subject to a particular tariff when present and subject to said tariff when absent.

The alert reader will appreciate that spectroscopic testing can be used to detect the taggant during production of a variety of products, including packaging, plastics, ingestible products, and industrial products.