Polymer Additive Analysis by EI and APCI

Transcription

1 Polymer Additive Analysis by EI and APCI Kate Yu, Eric Block LC/MS Waters Corporation Introduction to polymer additive analysis by LC/MS.

2 Electron Ionization (EI) Advantages Classical spectra Library searchable Positive compound ID Relatively easy to obtain Rugged Interpretable Structural elucidation The Thermabeam interface, which is an improved form of particle beam interface, is used to generate electron ionization (EI) spectra for LC/MS. Electron ionization, due to it s high ionization energy (about 70 ev), offers a reproducible fragmentation pattern of a molecule, which can be searched against a library for positive compound identification. This type of ionization is well suited for qualitative analysis where extensive structure-informative fragmentation is highly desirable.

3 Advantages of Atmospheric Pressure Chemical Ionization (APCI) Molecular weight information Fragmentation with CID Easy to use Rugged Technique Accommodate LC flows up to 2.0 ml/min. Good sensitivity The atmospheric pressure ionization interface is now one of the most popular interfaces for the single quadrupole LC/MS. In this type of interface, two types of ionization are possible: Electrospray (ESI) and atmospheric pressure chemical ionization (APCI). Both ESI and APCI are soft ionization techniques, which allow molecular weight information to be obtained easily. In addition, they are both much more sensitive and very well suited for quantitative analysis.

4 Choice of EI and APCI P D A MS Detection Samples, Info Needed, Lab Priorities Waters TMD EI Unknown Compound ID Waters ZMD (APCI / ESI) Known Confirmation The proper choice of interface depends on the information required from the analysis. If you need to identify unknowns in your sample then EI is the proper choice. For molecular weight information and confirmation of known compounds, either APCI or ESI is best suited.

5 Goal To demonstrate how EI and APCI can complement each other in chemical analyses AcCN extract of Polypropylene as model system EI for positive ID APCI for confirmation Sensitivity and linearity evaluation of EI and APCI In this work, we chose the organic extractable from polypropylene as our model analyte to demonstrate how information separately obtained from EI and APCI can compliment each other.

6 EI Experimental Conditions Integrity MS Detector: Scan Range: 60 to 900 Da Ion Source Temp: 200 o C Nebulizer Temp: 75 o C Expansion Region Temp: 75 o C In our lab, the polypropylene was extracted with acetonitrile. 10mL of acetonitrile was added to 5 grams of polypropylene and heated to 60 C for 72 hours. The supernatant was filtered prior to analysis. The acetonitrile extracts were then analyzed by two LC/MS instruments: First, the Thermabeam interface with EI offered on the Waters Integrity System. Shown here are the instrument conditions for the Integrity mass detector.

7 APCI Experimental Conditions Platform LC Conditions: Scan Range: 80 to 1000 Da Ionization Type: APCI Negative Cone Voltage: -12 V (Regular) Cone Voltage: -40 V (CID) Probe Temperature: 400 o C Second, the Atmospheric pressure Ionization Interface with APCI (or ESI) offered on the Micromass Platform LC mass detector. Shown here are the instrument conditions for the Platform LC mass detector. PDA detection was available on both instruments.

8 LC/MS of AcCN Extract from PP Total ion chromatograms (TIC) of the extract: Comparison of EI, APCI-, and PDA EI analysis of each component: Spectrum of the unknown Chemical structure APCI analysis of each component: Spectrum of the unknown with MW information CID Spectrum of the unknown with limited fragmentation Compound identification was determined by; 1. Comparison of the three modes of detection. 2. Matching EI spectra with the Wiley library generates lead suspects. 3. Obtaining molecular weight information from APCI helps rule out wrong matches. 4. Generating limited fragmentation in API with In-Source Collision Induced Dissociation (CID) helps to confirm EI results.

9 APCI -, EI, PDA Comparison APCI - : TIC EI: TIC PDA: 210 nm Min Shown here is the comparison of three modes of detection of the polypropylene extract.

10 MS Spectra of Peak # [M-H]- APCI - : 12V 48.4 EI m/z APCI - : 40V m/z t-bu HO t-bu O O MW 436 NH O O NH m/z OH Note that two mass spec interfaces generate different mass spectra. The spectra on the left, comes from the APCI interface. The upper left corner mass spectrum was created using a cone voltage of 12 volts.the major intensity indicates the molecular ion (435 [M-H]-). Increasing the cone voltage, creating In-Source CID, generates limited fragmentation displayed in the lower left corner. The mass spectrum in the upper right corner generated by the EI interface creates library searchable spectra. Information about the chemical structure can be obtained.

11 MS Spectra of peak # EI: Unknown Spectrum EI: Library spectrum, 96% Match H 3 C (CH 2 ) 15 CH CH m/z Positive identification of this unknown compound was determined by comparing the EI mass spectrum of peak # 6 (upper spectrum) to the Wiley library and coming up with an excellent match (lower spectrum), 1-Octodecanol.

12 AcCN Extract of PP (Identification) 6 EI: TIC Minutes 1. Naugard Degradant: MW NC-4: MW Bis(methylthio)methylene-1-phenyl-1,4-methyl-4-penten-1-one: MW ,9-Di-tert-butyl-1-oxaspiro[4,5]deca-6,9-diene-2,8-dione: MW Naugard: MW Octodecene: MW Irgonox 1076: MW 530 Utilizing the both EI and APCI spectra all of the compounds detected in the polypropylene extract were identified.

13 Results of a 20-Fold Dilution TIC of APCI TIC of EI PDA at 210 nm Minutes A 20-fold dilution of the polypropylene extract was analyzed by the three detection modes. The APCI interface demonstrated the best sensitivity.

14 Conclusions Major peaks identified by EI and confirmed by APCI - Comparable chromatograms by PDA and MS Hydrocarbon component can ONLY be detected by EI APCI - exhibited better sensitivity and linearity than EI Among various analytical techniques used by people for additive analysis, LC/MS is superior. In addition to the chromatographic separation obtained with HPLC, a mass spectrometer offers sensitive and quantitative detection and positive identification of the additives.

15 Natural Products Analysis!Food Supplements, Botanical Extracts St.Johns Wort, and Red Clover!Strong Marketing Claims Limited Substantiation!Is the Marketed Compound the Active Ingredient? Questionable!Regulation by FDA Restricted by Statute Dietary Supplement & Health Education Act (DSHEA) 1994 The identification and quantitation of compounds extracted from natural products are method development challenges. Today we will discuss analytical methods developed for the analysis of St. John s Wort plant and red clover. The nutraceutical industry is growing rapidly. There are a number of natural products on the market today proclaiming health benefits with limited or no clinical trials. Scientists are questioning what is the real active ingredient in some of these natural products. Due to DSHEA, the Food and Drug Administration (FDA) has less oversight over nutraceuticals than pharmaceuticals.

16 Natural Products Analysis Quality Concerns!Quality of Botanicals varies by species, location, season, and Mother Nature!Identification and Characterization of the botanical species is subjective!few Official Methods of analysis are available!liquid Chromatography Methods utilizing Photo Diode Array and Mass Spectrometry detection are being developed Since the raw material of these natural products come from worldwide sources growing conditions differ creating variablitiy in the final product. The matrix of these botanicals are complex, making identification and characterization of the species difficult. Few validated analytical methods currently exist for nutraceuticals. However, analytical methods utilizing HPLC with PDA and MS are being developed for these natural products.

17 Natural Products Analysis Analytical Needs! Manufacturers use specific marker compounds for Quality Assurance Hypericin in St. Johns Wort Isoflavonoids in Red Clover! Method Validation for several components being conducted by: Institute for Nutraceutical Advancement American Society of Pharmacognosy Currently nutraceutical use marker compounds for quality assurance such as hypericin in St. Johns Wort and isoflavonoids in red clover. Citing the need for consistency and consumer confidence in the market place, manufactures are moving to more science and validated methods from consensus organizations. The Institute for Nutraceutical Advancement, sponsored by 30 companies, has a Method Validation Program developing HPLC-based methods. The American Society of Pharmacognosy is another organization developing methods for nutraceuticals.