Study on the Determination of Diphenyl Ketone-Based Light Stabilizers in Plastics Using Gas Chromatography-Mass Spectrometry

Abstract

This study systematically elaborates on the method development for qualitative and quantitative analysis of diphenyl ketone-based light stabilizers UV-0 and UV-24 in plastic products using gas chromatography-mass spectrometry (GC-MS). Through a series of studies including establishing standard curves, optimizing experimental conditions, and validating method reliability, precise detection of these two trace additives was successfully achieved. This method offers high sensitivity, good selectivity, and a wide linear range, providing reliable technical support for quality control in plastic products.

Introduction

Importance of Light Stabilizers in the Plastic Industry

Polymeric materials inevitably suffer from combined effects such as ultraviolet radiation, oxygen, and heat during outdoor use. These environmental factors can trigger photodegradation reactions like chain scission and cross-linking within polymer molecules. The manifestations include yellowing, embrittlement, cracking on material surfaces leading to significant declines in mechanical properties. Statistics show that unprotected plastic products exposed outdoors for six months may experience over 50% reduction in tensile strength.

To delay this photodegradation process, it is common practice to add light stabilizers industrially. Light stabilizers primarily function through three mechanisms: ultraviolet absorption, free radical capture, and excited state quenching. Among them, ultraviolet absorbers have become the most widely used category due to their efficient stability at moderate prices. Within numerous ultraviolet absorbers available globally—diphenyl ketones (such as UV-0 and UV-24) along with benzotriazole compounds account for approximately 65% market share due to their excellent performance regarding UV absorption capacity and thermal stability.

Technical Challenges in Quality Control In actual production processes,u00a0the addition amount of light stabilizer needs precise control; too low (<0.03%) fails to provide adequate protection while too high (>0.3%) not only increases costs but may also lead to 'anti-stabilization effect,' where excessive stabilizer molecules promote photodegradation instead.u00a0Thus,u00a0establishing accurate reliable detection methods is crucial for product quality control. However,u00a0detecting light stabilizers within plastics faces several technical challenges:u00a01) extremely low addition amounts (typically between 0.03%-0.3%);u00a02) severe interference from polymeric matrices;u00a03) structural similarities among similar types make separation difficult.Traditional spectral methods often struggle meeting these detection requirements whereas GC-MS technology emerges as an ideal solution owing its high separation efficiency coupled with elevated sensitivity.

Experimental Methods

Instrumentation & Reagents The gas chromatography-mass spectrometry system utilized herein features a DB-5MS capillary column (60m×250μm×0.25μm), known for its exceptional inertness alongside thermal stability making it particularly suitable analyzing thermally unstable compounds.The mass spectrometer employs electron impact ionization source (EI), covering scanning ranges from m/z1 .5 -109
molecular weight axis stability reaches ± .1 u/48 hours.Reagents employed include analytical grade acetone ,UV -O(2 ,4-dihydroxy diphenyl ketone,CAS No .131 -55 -5 )andUV -24(2 ,2-dihydroxy -4-methoxybenzophenone,CAS No .131 -53 -3 )standards.All standards underwent purity verification stored under dry dark conditions respectively . Standard Solution Preparation Accurately weigh appropriate quantities of both UV-O &UV –24 standards dissolve into acetone then dilute prepare concentration gradients ranging from1 ppmto100ppm solutions each concentration prepared thrice parallel assess reproducibility during preparation avoiding exposure direct sunlight employing ultrasonic assistance ensure complete dissolution.*Sample Pre-treatmentSelect PBT resin containing known amounts both UVO&U V–24 test samples.Dissolve sample via precipitation technique :accurately weigh out1 g sample add10 ml chloroform dissolve subsequently introduce40ml methanol precipitate polymers centrifuge collect supernatant filter through organic phase membrane retaining filtered liquid directly analyze by GC-MS.Method demonstrates high recovery effectively removing interferences originating matrix composition.*Instrumental Analysis Conditions *Gas chromatographic parameters: injection port temperature280℃ split ratio10:1 carrier gas pure helium flow rate set at1 mL/min.programmed heating initial temp maintained80℃for duration min increasing15℃/min until reaching final280 ℃holding period lasting10 mins.Mass spectral settings included ion source temperatures230 ℃transfer line temperature280 ℃employ full scan mode(m/z50–500)&selected ion monitoring(SIM).*Results DiscussionQualitative AnalysisUnder optimized chromatographic conditions,both UVO&U V–24 exhibited favorable separations.UV-O retention time recorded11 minutes featuring characteristic ions m/z214(molecular ion peak ),196([M-H20]+),105(base peak);whileU V–24 displayed11 minutes retention corresponding respective ions being m/z244(molecularionpeak ),226([M-H20]+),135(basepeak ).Comparisons against standard mass spectra libraries yielded matching rates exceeding94%,with molecular weights aligning theoretical values confirming CAS numbers consistent target compounds.Careful observations revealed certain additives present within PBT resin base could elute near identical retention times.Selective characteristic ions optimization ensured baseline separation preventing false positives occurrences.*Quantitative Analysis *External calibration curve established utilizing external standard approach.UV-O demonstrated strong linearity across concentrations ranging between1 ppmto100ppm yielding regression equation y=35872x+1254 R²=99%.Similarly,U V–24’slinear equation formulated y=42156x+987 correlating coefficientR²=99%.Detection limits(LOD,S/N =3 )recorded at respective levels measuring down upto200 ppmand300ppmsatisfying microanalysis criteria.In order validate accuracy conducted spiking recovery experiments introducing various levels additive into PBT samples namely adding10 ,50,and100ppmsamples resulted recoveries falling93%-102 % relative standard deviation(RSD)<5%,indicating robust precision validity methodology applied .*Actual Sample Analyses *Employing developed methodologies analyzed three setsP BTresin samples.Results indicated no detectable targets#sample ;second sample contained measured levelsofU VOamounts registering around79%(aligns closely formulation percentage).Third-sample detectedvalues registered81 %(slightly higher than intended formulation likely attributed uneven mixing or deviations observed purity standards throughout testing procedures.No notable matrix interferences emerged throughout analyses affirming specificity inherent proposed techniques .*ConclusionResearch succeeded establishing effective means detecting UVO&U V –24lightstabilizing agents based uponGC-MStechnology highlighting advantages including: u20221.High Sensitivity capable detecting parts per million scale trace additives; u20222.Good Selectivity efficiently mitigating matrix interference risks; u20223.Wide Linear Range encompassing typical concentrations encountered industry applications; u202224.Simplified operations reduced overall analysis durations suited batch processing environments.This approach proves beneficial not solely towards ensuring product quality controls yet additionally serves aging research purposes tracking consumption patterns aiding formula optimizations.Furthermore extending applicability toward other categoriesoflightstabilizing agents establishes comprehensive systems assessing diverseplasticadditives hence enhancing global competitiveness local industries!*Outlook**As regulatory frameworks tighten concerning environmental concerns alongside escalating demands placed material performances,newer challenges arise pertaining existing technologies surroundingdetection protocols associatedwithlightstabilizing agents!Future endeavors should focus investigating areas such developing more efficient pre-treatment methodologies e.g.accelerated solvent extraction,microwave-assisted extractions exploringLC-MS/MSapplications targeting challenging volatile substances implementing simultaneous assessments multiple additive formulations ultimately advancing non-target screening strategies relyinghigh-resolutionmassspectrometric approaches addressing emerging needs relatednoveladditive detections! Findings contribute valuable insights improvingqualitycontrolmechanismswithinplasticsindustry bolsteringcompetitiveadvantage domesticproducts!