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ALTERNATIVE SAMPLE INTRODUCTION FOR MASS SPECTROMETRY ANALYSIS OF POLYMER SAMPLES USING ATMOSPHERIC SOLIDS ANALYSIS PROBE (ASAP)

Stephanie Harden, Michael O'Leary, and Baiba Cabovska Waters Corporation, Milford, MA

INTRODUCTION Control of the synthesis of polymeric material and formulated products containing polymeric material requires a variety of analytical techniques to assess the composition as well as their molecular weight distribution. Typically, tools such as Size Exclusion Chroma-tography and Gradient Polymer Elution Chromatography have provided analysis of the polymer profile. Additionally, spectroscopic tools such as Infrared Spectroscopy and Nuclear Magnetic Resonance Spectroscopy have been employed to provide characteristic compositional data.

An alternative approach is offered, Atmospheric pressure solids analysis probe (ASAP) — an ambient thermal desorption ionization technique for sample introduction into a mass spectrometer, for composition as well as molecular weight characterization. ASAP has been shown to provide the molecular weight as well as the mass spectra of a wide range of surfactants, oligomeric mixtures, pre-polymers, natural and synthetic oils as well as mixtures of formulated solutions of polymers literally within seconds. In addition the utilization of this technique for quality control inspection for product drift or variation is shown using comparative mapping software, MarkerLynx XS.

METHOD Samples are dissolved in suitable organic solvent at a concentration of 1 mg/mL. 1 � L of the solution is applied to the tip of a sealed capillary tube. The tube is loaded directly into the mass spectrometer source at atmospheric pressure. (Figure 1.) Heat gas allows the volatile and semi volatile material to thermally desorbs from the tip. Ions are formed due to electrical discharge and are drawn into the quadrupole for analysis.

Operating Conditions • Ion Mode API+ • APCI Cone 10 V • APCI Corona 3 mA • Source Extractor 5 V • Source RF Lens 0.1 V • Source Temperature 125 C • Probe Desolvation Temperature 500 C • Desolvation Gas Flow 500 L/Hr Nitrogen • Mass Range (m/z) 50-2048

CONCLUSIONS • Use of ASAP as an inlet for Mass Spectral

analysis of non ionic surfactants, oligomers and pre-polymers is a rapid, direct analysis.

• Utilizing a single quadrupole mass spectrometer semi quantitative analysis of formulated products is easily conducted resulting is control and inspection parameters for a wide array of products systems

• With the addition of the statistical data reduction tool, MarkerLynx XS complex MS data sets are easily evaluated.

References 1. McEwen, C.; et al, Anal. Chem. 2005, 77,7826-731. 2. Lewis, R.; Major, H.; Green, M. Waters Corporation.

720002847en. 3. Tergitol TM manufactured by the Dow Chemical Co., Midland MI.

Supplied by Spectrum Chemicals New Brunswick, NJ, USA. 4. Poly Fox® PF-151N and PF-656 OMNOVA Solutions Inc, Fairlawn,

OH, USA. 5. PEG, PPG and Triton X-100, Sigma Aldrich® 3050 Spruce St.,

St. Louis, MO, USA. 6. PEG, Acros Organics, 2440 Geel, B-2440 Belgium 7. PEG, Fisher Scientific, Fair Lawn, NJ, USA

Figure 3. Mass Spectral comparison of reference polymeric additive in formulated product.

Figure 2. ASAP mass spectra for PEG samples from three different suppliers, with molecular weight calculations.

PEG600 Supplier A

PEG400 Supplier B

PEG400 Supplier C

PEG300 Supplier B

PEG200 Supplier C

PEG600 Supplier B

PEG600 Supplier A

PEG400 Supplier B

PEG400 Supplier C

PEG300 Supplier B

PEG200 Supplier C

PEG600 Supplier B

728

676

561

573

435

341

MzCompound Supplier Mn Mw Mz+1

PEG200 C 282 315 363

PEG300 B 356 402 462

PEG400 C 479 534 603

PEG400 B 486 531 584

PEG600 B 571 636 705

PEG600 A 636 691 755728

676

561

573

435

341

MzCompound Supplier Mn Mw Mz+1

PEG200 C 282 315 363

PEG300 B 356 402 462

PEG400 C 479 534 603

PEG400 B 486 531 584

PEG600 B 571 636 705

PEG600 A 636 691 755

Figure 7. PLS-DA Comparison of reference polymer blend group A and group G (low level of one component).

Figure 8. Comparison of reference polymer blend group A and group G can be interrogated to locate the extreme data points driving the comparison.

Figure 5. PLS-DA Comparison of reference polymer blend group A-D and group E, F & G (Blends with varied concentration and polymer distribution).

Figure 1. The sample, either solid or solu-tion, is applied to the tip of a capillary tube. The tube is directly inserted into the mass spectrometer without the need for opening vacuum lock. The sample is then volati-lized by heated gas, ionized by discharge from a corona pin and drawn into the mass spectrometer for anal-ysis.

Figure 4. Individual Mass Spectral Collected using ASAP with a single quad mass spectrometer of seven separate polymer blends. Blends A-D are blends of the same three polymers each with the sample target proportions. Blend G is a blend of the three polymers with a slight change in the content of one of the polymers. Blend E & F are variations of the MW of one of the polymers in the blend.

Figure 6. Mass Spectral comparison of two formulated blends each containing the same 3 polymers. Little or no difference is noted.

Blend G

Blend A

RESULTS & DISCUSSION Mass spectral analysis of non ionic polymeric surfactants such as polyethylene glycol (PEG) is easily accomplished using the ASAP inlet yielding a rich data set, (Figure 2). The molecular weight values are calculated by standard summation algorithms using abundances and absolute mass values for each component in the mixture.

Taking the above approach further, the unique mass signature of polymeric additives provides a direct method to analyze low level polymeric additives in formulated products. In the example illustrated in Figure 3, the unique mass spectra signature of a fluorinated surfactant is used to identify and provide a semi quantitative assessment of the surfactant present in a 10% bulk polymer solution. The analysis is accomplished in less than ten minutes without the need for separation or extensive sample preparation.

In the final example a set of samples constructed of three nonionic surfactants, Triton X 100, Tergitol 15-S-7 and Polypropylene Glycol 1000 are evaluated to collect their mass spectrum using the ASAP inlet (Figure 4). It is clear that the subtle material variation and concentration variation is not easily assessed when the mass distribution is viewed. Using the data mapping tools in MarkerLynx XS the complex data sets are easily binned showing the variation in samples E, F and G as compared with the four replicate samples A through D (Figure 5). Looking at one pair of the polymer blends, a further assessment can be conducted comparing the raw MS data with that of the data mapped for comparison with the MarkerLynx XS tool (Figures 6 &7). The plot of the data points that build the comparison is shown in figure 8 with the points illustrating the greatest difference at the extremes of the plot with the mass/charge marker at 426 Daltons identified.