Advances in LC-MS Instrumentation (Journal of Chromatography Library)

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In this work we present an overview focused on the developments of liquid chromatography mass spectrometry applied to the analysis of the main classes of micropollutants in aqueous and solid environmental samples. Over the last two decades the use of LC techniques coupling with a high resolution MS to identify unknown contaminants has advanced spectacularly. This progress is mostly due to the development of new instrumentation. LC techniques have replaced gas chromatography GC as they present obvious advantages such as reduced sample pretreatment and their capacity to determine polar or thermally stabile compounds.

The combination of LC and MS offers the possibility to take advantages of both LC as a powerful and versatile separation technique and MS as a powerful and sensitive detection and identification technique.

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The intrinsic properties of these two techniques result in an extremely analytical tool useful with many application areas. There are many different LC-MS systems on the market, that present advantages and limitations according to the type of samples that must be analyzed.

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Interface designs have changed considerably and have become much more sophisticated and efficient. Since the introduction of atmospheric pressure ionization techniques API , LC-MS has played an increasingly important role in environmental analysis allowing to analyze a broad range of compounds, including nonvolatile, thermally labile, and polar species.

ESI is particularly well suited for the analysis of polar compounds whereas APCI is highly effective in the analysis of medium- and low-polarity substances. When ESI is operating in the negative ion mode of ionisation NI the sensitivity achieved in the analysis of some relevant pollutant compounds is considerably better than that of the ESI interface operating in the positive ion mode of ionisation PI and the APCI interface operating in the NI mode [ 1 , 2 ].

However, some recent studies [ 3 — 5 ] indicate that the APCI interface operating in the PI mode can furnish sensitivities comparable in many cases to that of the negative ion ESI.

Combined ion sources can be considered as an option merging the advantages and application ranges of atmospheric pressure ionization techniques, but on the other hand their sensitivity may be a compromise between both modes. For complex samples, containing many compounds, LC-MS is not enough for the unequivocal confirmation of analytes for the final identification. LC-MS 2 takes out this problem and results in a much higher degree of certainty in the identification of the unknowns.

Triple-quadrupole QqQ mass analyzers have become the most widely used analytical tool in the environmental analysis. Their application has allowed the determination of a great number of compounds, especially polar ones that were previously difficult or even impossible to analyze. When the first quadrupole of a QqQ is replaced by a double-focusing mass spectrometer, the instrument is termed a hybrid. Hybrid Qq-TOF-MS technique is the most common application in the structural characterization in the environmental analysis and allows an unequivocal confirmation of the contaminants detected.

Moreover, TOF-based mass analyzers allow to find additional nontarget organic contaminants. The elimination of false positives is possible by generating full-scan production spectra with an exact mass. Qq-LIT is considered as a very powerful tool for a rapid identification and confirmation of metabolites in different matrices because of its capability of producing additional spectral information useful for structure clarification [ 7 — 9 ]. Some papers compared a real performance of different types of modern tandem mass analyzers for particular applications, which provides valuable complementary information.

QqQ provides better linear dynamic range, higher precision, less matrix interferences, and better robustness, while LIT provides an excellent sensitivity for product ion measurements. QqQ provides at least fold higher sensitivity compared to other mass analyzers and better linear dynamic range.

Although the QqQ is more sensitive and precise, mean values obtained by all instruments are comparable. The miniaturization is an important issue considered in all fields of analytical instrumentation including both parts of LC-MS coupling. On the other hand, it requires a higher acquisition speed of mass spectrometer to obtain enough sampling points for the reliable peak integration. Modern TOF-based mass analyzers and also some ion traps are capable of reaching higher acquisition speed points for peak, what is useful to generate more sampling points per peak for a better quantification.

Examples of potential applications of these methods have been published. The composition of the mobile phase is an important factor for improving separation in LC. An acidic condition with acetonitrile-water and methanol-water mixtures with a gradient elution is among the most common approach for improved peak shape in chromatography. Modification of the mobile phase, when performed in an attempt to improve the sensitivity of MS detection, has been accomplished with acetic acid, formic acid, or ammonium acetate.

Nonvolatile additives, such as oxalic acid, should be avoided when ESI is used and trifluoroacetic TFA acid can suppress the ionization in the electrospray source. The ion suppression and matrix effects can cause severe problems with the quantification in the trace analysis.

Another important issue is the sample preparation prior to LC-MS analysis [ 20 ]. Obviously, the internal standard must be added before any sample preconcentration step. Another alternative approach for the relative quantification is the use of response factors determined from the calibration curves of pure standards and then applied for real samples [ 21 , 22 ].

The internal standard addition and response factors approach can be combined in one platform together with the well-optimized chromatographic separation. An overview of the applications of LC techniques coupled to mass spectrometry in the determination of the main classes of micropollutants in aqueous and solid environmental samples is presented. These compounds are present to very low concentrations and due to the high complexity of some environmental samples; very specific and sensitive analytical procedures are needed for their determination.

Although these compounds are not currently covered by the existing regulations, the possibility of adverse effects on humans and animals and their extensive environmental distribution has recently attracted an increasing interest. In particular, these compounds include pharmaceuticals, personal care products, flame retardants, surfactants, and plasticizers, among others. Figure 1 shows a scheme summary of the micropollutants considered in this work. Micropollutants contaminants are released into environment mainly as a result of the manufacturing processes, the disposal of unused or expired products, and the excreta, mostly through urban wastewater and many of them can further spread through the water cycle, even reaching drinking water, due to their hydrophilic character and low removal at wastewater treatment plants WWTPs and drinking water treatment plants DWTPs [ 23 — 25 ].

They can also enter into the environment due to surface-water runoffs and soil leaching after the agricultural applications of manure. Once released into the environment, micropollutants are subject to different processes, such as biodegradation and chemical and photochemical degradation, which contribute to their elimination. When these transformations take place, degradation products can differ in the environmental behaviour and toxicity.

However, they are often more persistent than their corresponding parent compounds [ 26 ]. To obtain high recoveries and minimise interference, the determination of these pollutants requires extraction and clean-up steps prior to detection. Solid phase extraction SPE is frequently used to extract these compounds from aqueous samples [ 27 ].

However, the demand to reduce the solvent volumes and avoid the use of toxic organic solvents has led to substantial efforts to adapt existing sample preparation methods to the development of new approaches. Miniaturisation has been a key factor in the search of these objectives.

Microextraction techniques allow high enrichment factors and minimise solvent consumption which avoid environmental pollution.

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The extraction of emerging pollutants from solid matrices is carried out by accelerated solvent extraction ASE pressurised liquid extraction PLE , ultrasound assisted extraction UAE , and microwave-assisted extraction MAE. These methods have been replaced to Soxhlet extraction, the classical procedure for solid matrices [ 28 — 30 ]. The listed contaminants are either known or anticipated to exist in drinking water systems and will be considered for a potential regulation.

This final CCL-3 contains chemicals and 12 microbial contaminants, and it includes three pharmaceuticals, eight hormones, and several disinfectant by-products and industrial additives [ 31 ]. The WFD provisions will be required from Member States and Associated States to establish programs to monitor the quality of water, which implies a review of human activity on the pollutants and an economic analysis of water use.

In this context, there is an urgent need for a list of emerging contaminants as possible candidates for introduction into the WFD list of priority substances. This can be amended every four years with revisions and additions of new contaminants [ 32 ]. Among new contaminants, pharmaceuticals belong to a group of an increasing interest due to their pharmacological activity and rising consumption deriving from their use in human and veterinary medicine [ 33 , 34 ]. The discharge of therapeutic agents in effluents from production facilities, hospitals and private households, improper disposal of unused drugs, and the direct discharge of veterinary medicines leads to the contamination of environmental waters, and wastewater-treatment plants are considered to be a major source [ 33 , 34 , 36 — 38 ].

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Know more than Petroleum Engineers with this book. Journal of Chromatography Library Book 72 Hardcover: Elsevier Science; 1 edition January 4, Language: Be the first to review this item Amazon Best Sellers Rank: Related Video Shorts 0 Upload your video. Try the Kindle edition and experience these great reading features: Customer reviews There are no customer reviews yet.

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English Choose a language for shopping. To get the free app, enter your mobile phone number. Would you like to tell us about a lower price? Learn more about Amazon Prime. The different LC-MS techniques available today were developed to suit specific analytical needs and the application range covered by each one is wide, but still limited. Once approaching LC-MS for a specific need, the fast technical evolution and the variegated commercial offer can induce confusion in the potential user.

The role of this book is to enlighten the state-of-the-art of LC-MS evolution through a series of contributions written by the people that brought major, recent innovations in the field. Each chapter will take into consideration the novelties, the advantages and the possible applications covered by a particular technical solution. The book will also include new analytical methods that can provide benefits using the most recent innovations in LC-MS plus a certain number of key applications.

Read more Read less. Kindle Cloud Reader Read instantly in your browser. Product details File Size: Elsevier Science; 1 edition December 5, Publication Date: December 5, Sold by: Related Video Shorts 0 Upload your video. Customer reviews There are no customer reviews yet.

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