Acrylic acid Detection limit

HPLC-UV is a popular technique to analyse textile dyes extracted from polyester fibres [697], acidic dyes from wool fibres [698] and basic dyes from acrylic fibres [699]. HPLC provides better sensitivity and resolution than TLC [697-699]. GE-RPLC has been used for the determination of 18 disperse dyes (e.g. Navy D-2G-133, Orange CB, Yellow D-3R and Red D-2G) extracted from polyester [700]. Compared with the traditional TLC method, HPLC offers lower detection limits, better observation of contaminant peaks, and reproducible quantitative results. HPLC has also been used to determine azo dyes [701,702]. 

CE has been used for the analysis of anionic surfactants [946,947] and can be considered as complementary to HPLC for the analysis of cationic surfactants with advantages of minimal solvent consumption, higher efficiency, easy cleaning and inexpensive replacement of columns and the ability of fast method development by changing the electrolyte composition. Also the separation of polystyrene sulfonates with polymeric additives by CE has been reported [948]. Moreover, CE has also been used for the analysis of polymeric water treatment additives, such as acrylic acid copolymer flocculants, phosphonates, low-MW acids and inorganic anions. The technique provides for analyst time-savings and has lower detection limits and improved quantification for determination of anionic polymers, compared to HPLC. 

Another successful example is the separation of a series of steroids listed in Fig. 6.11 using a monolithic capillary column prepared by redox initiated polymerization of a solution of acrylamide 4, methylene bisacrylamide 5, vinylsulfonic acid 12, and dodecyl acrylate 18 in N-methylformamide/TRIS-boric acid buffer (pH 8.2) to which polyethylene glycol) (MW 10,000) was added (overall composition 5% T, 60% C, 10% vinylsulfonic acid, 15% lauryl acrylate, 3% polyethylene glycol)). The capillary tube was first vinylized and its part beyond the detection window was coated with linear polyacrylamide to avoid band broadening. Since laser induced fluorescence was used to decrease the detection limit of the method to about 100 attomoles for neutral steroids, all of the analytes were first tagged with dansylhydrazine. Fig. 6.12 shows an... 

Separations of complex steroid mixtures were achieved recently by Que et al. [76] using both isocratic and gradient elution. Mass spectrometric detection gave femto-mole detection limits while laser-induced fluorescence of dansylated ketosteroids ranged in attomole levels (Fig. 10.16). Monolithic column packings were used with a 35 cm (25 cm packed bed) x 100 pm i.d. capillary packed with a polymer prepared from 5% T (total monomer concentration), 60% C (total crosslinker concentration), 3% polyethylene glycol, 10% vinylsulfonic acid and 15% lauryl acrylate. Details of the monolithic column preparation can be found in refs. 36,76, and 193. Similar monolithic columns can be used for the separation of bile acids [194],... 

Liquid-liquid extraction of short-chain organic acids, ketoacids, or dicarboxylic acids result in low and often unreproducible extraction yields due to the hydrophilic character of the analytes. However, some authors report reproducible results for short-chain acids at mg/1 concentrations after liquid-liquid extraction at pH 2, although extraction yields remain low. Note also that organic solvents, namely diethylether, may be contaminated with organic acids. An unusual variation in liquid-liquid extraction is the use of tri-n-octylphosphine oxide (TOPO) in methyl-tert-butylether (MtBE) to enhance extraction yields, e.g., of acrylic acid in marine waters and of organic acids in aqueous solutions obtained from air collection chambers." TOPO s very low solubility in water and its high polarity make it suitable for extraction of polar compounds. The extraction yield for acrylic acid was 40% and its detection limit after derivatization with pentafluorobenzyl bromide was estimated to be 3 nM. ... 

Betso and McLean [11] have described a differential pulse polarographic method for the determination of acrylamide and acrylic acid in polyacrylamide. A measurement of the acrylamide electrochemical reduction peak current is used to quantify the acrylamide concentration. The differential pulse polarographic technique also yields a well-defined acrylamide reduction peak at 2.0 V versus SCA (reduction potential), suitable for qualitatively detecting the presence of acrylamide. The procedure involves extraction of the acrylamide monomer from the polyacrylamide, treatment of the extracted solution on mixed resin to remove interfering cationic and anionic species, and polarographic reduction in an 80/20 v/v) methanol/water solvent with tetra-n-butylammonium hydroxide as the supporting electrolyte. The detection limit of acrylamide monomer by this technique is less than 1 ppm. 

In order to obtain quantitative results by HS-GC, the system must be calibrated. Absolute quantitation is not possible. Quantification can be done by the conventional external calibration method with liquids containing the analytes concerned in known concentrations or by means of standard addition. Pausch et al. [958] have developed an internal standard method for solid headspace analysis of residuals in polymers in order to overcome the limitations of external standardisation cfr. Chp. 4.2.2 of ref. [213a]). Use of an internal standard works quite well, as shown in case of the determination of residual hydrocarbon solvent in poly(acrylic acid) using the solid HS-GC-FID approach [959]. In the comparison made by Lattimer et al. [959] the concentrations determined by solid HS-GC exceeded those from either solution GC or extraction UV methods. Solid HS-GC-FID allows sub-ppm detection. For quantitative analysis, both in equilibrium and non-equilibrium conditions, cfr. ref. [960]. Multiple headspace extraction (MHE) has the advantage that by extracting the whole amount of the analyte, any effect of the sample matrix is eliminated the technique is normally used only for method development and validation. 

Acrylo-type compoimds, such as acrylic acid, acrylonitrile and acrolein can be present in polyacrylamides. Their unsaturated characteristics could cause them to interfere with the acrylamide analysis. Acrylic acid is electroreducible, but its anionic form, acrylate is not. A polarogram of acrylic acid and acrylamide in an 80 20 (v/v) methanol/water solution with tetra-/i-butylammonium chloride as the supporting electrolyte showed that the reduction of the associated acid occurs at ca. - 1.7 V vs SCE, 0.3 V more positive than the acrylamide reduction. The reduction peak of acrylic acid is easily resolved from acrylamide. Esters of acrylic acid are electroreducible and some, such as the alkyl esters (eg. ethyl acrylate) reduce in the same potential region as acrylamide and do constitute an interference. Acrylonitrile is also electroreducible at the same potential as acrylamide. However, the high volatility of acrylonitrile allows it to be readily purged from the analyte solution. The detection limit of acrylamide monomer by this technique is less than 1 ppm. 

Roche et al. developed a surface plasmon resonance sensor for dextromethorphan based on a molecularly imprinted beta-cyclodextrin polymer with a detection limit of 0.035 pM and a dynamic range of 0.035 pM to 6.00 mM, depending on the instrumental setup [412]. Recently Al-Mustafa etal. have reported liquid selective electrodes for dextromethorphan, based on liquid membranes or graphite electrodes coated with polymers of acrylic acid and 2-vinyl pyridine functional monomers and ethylene... 

---