SPE solid phase extraction technology
Hello, everyone, see you again. Through the content of previous issues, everyone must have understood the pretreatment analysis content such as gas phase and liquid chromatography analysis, GPC gel purification chromatography, and SPE solid phase extraction principle. Although analysis and detection technology has made great leaps in recent years, sample pretreatment is still a challenge that researchers must face.
Solid Phase Extraction (SPE for short) is a widely used and increasingly popular sample pretreatment technique developed since the mid-1970s. In the field of environmental analysis, it also provides an ideal choice for the majority of analysts. Today I summarize the main application of SPE solid phase extraction technology in water quality analysis from the following aspects.
Determination of Pesticide Residues in Water
For the detection of pesticide residues in water, weakly polar adsorption materials such as C18E and C8 are generally used, and methanol is generally used as the eluting solution. The pesticide residue content in natural water is very low, and only through reliable enrichment and concentration methods can the detection limit and quantification limit of the instrument be reached. Using Welch’s solid-phase extraction device and C18E small column, the enrichment and purification of the pesticide to be tested in the water sample can be realized. Large-volume sample loading and small-volume elution solution are used for elution, and then concentrated to constant volume for on-machine detection , the detection limit of the instrument method can be reached.
Such as: Determination of Carbaryl in Water (SL740-2016)
◆ 1. Solution preparation
➦Standard working solution: Accurately pipette 1mL of standard stock solution, dilute it with methanol and dilute to 10mL, the concentration is 10μg/mL
➦0.05% TFA aqueous solution: take 0.5mL TFA, dilute to 1L
➦TFA methanol solution: Take 0.1mL TFA and add it to methanol, and dilute to 100mL with methanol
◆ 2. Extraction steps
➦ Measure 100mL water sample (if the water sample is turbid and has impurities, filter it first to remove suspended solids), adjust the pH value of the water sample to less than 2 with dilute hydrochloric acid, and wait for purification
◆ 3. Purification steps
SPE column: Welch Welchrom® C18E Specification: 500mg/6mL
➦Activation: 6mL methanol, 6mL water, discarded
➦Sample loading: After all the purified solution is loaded, control the flow rate, not too fast. After the sample dries up, add 10mL of pure water to the sample bottle, clean the inner wall of the sample bottle, and then load the sample
➦Elution: first eluted with 10mL dichloromethane, then eluted with 8mL TFA methanol solution, drained
➦ Blow with nitrogen in a water bath at 40°C until nearly dry (leave about one drop), dilute to 1mL with methanol water, and put on the machine
Determination of organic pollutants in water
Industrial wastewater often contains organic pollutants such as petroleum, aromatic hydrocarbons, and polycyclic aromatic hydrocarbons, which are toxic to humans and organisms. The dissolved oxygen in the water is consumed during biodegradation, which deteriorates the water quality and destroys the ecological balance. For the determination of organic pollutants in water, Welch has also launched corresponding solutions.
Such as: Determination of 15 polycyclic aromatic hydrocarbons in water (HJ 478-2009)
◆ 1. Extraction steps
➦ Measure 20ml of the water sample to be tested in a 50mL centrifuge tube, add 0.2g sodium thiosulfate, 1g sodium chloride, 10mL n-hexane, ultrasonically extract for 15min, centrifuge at 6000r/min for 5min, and transfer the supernatant to another clean 50mL Centrifuge tube; add 10mL of n-hexane to the residue again, ultrasonically extract for 15min, centrifuge at 6000r/min for 5min, combine the supernatant, blow with nitrogen to about 5mL, and wait for purification.
◆ 2. Purification steps
SPE column: Welch Welchrom® Florisil PR specification: 1000mg/6mL
➦Activation: add 5mL dichloromethane and 10mL n-hexane in turn, discard
➦Sample loading: all the samples to be purified are loaded, and the effluent is collected
➦ Rinse: 5mL n-hexane, collect the effluent
➦Elution: 8mL dichloromethane/n-hexane (1/1) elution, collect the effluent
➦Concentration: Place the liquid collected in the above steps at 30°C under nitrogen blowing until nearly dry, add 3 mL of acetonitrile to the centrifuge tube, mix well, blow slowly with nitrogen to remove dichloromethane/n-hexane, and use acetonitrile to make up to volume to 2mL, pass through a 0.22μm filter membrane for liquid chromatography determination
Determination of phenolic compounds in water
At present, in the quality testing of urban water supply, the detection of phenolic compounds has been increased. There are also corresponding detection standards in surface water, groundwater, and domestic sewage (such as HJ 744-2015 Determination of phenolic compounds in water quality by gas chromatography-mass spectrometry), which can be measured by Welch SPE cartridges and solid-phase extraction devices. The small column is enriched, then concentrated, redissolved, and analyzed on the machine. Take bisphenol A as an example. Bisphenol A is everywhere, from mineral water bottles, medical equipment to food packaging materials, it can cause endocrine disorders and threaten the health of fetuses and children.
Regarding the determination of bisphenol A in drinking water, Welch also launched a corresponding solution case:
◆ 1. Extraction steps
➦Take 100mL of water directly as a sample and wait for purification. If there are obvious impurities in the water, use NY microporous filter membrane 0.45μm to filter and then purify
◆ 2. Purification steps
SPE column: Welch Welchrom® C18E Specification: 500mg/3mL
➦Activation: 10mL methanol, 10mL water (pH2.64), discard
➦Sample loading: Add 100mL water sample to the SPE column, discard
➦Elution: 10mL (V dichloromethane: V methanol) = 8:2 elution, collected in a 15mL centrifuge tube, drained
➦ After blowing dry with nitrogen blower, dilute to 1mL with methanol, and perform HPLC detection
Well, friends, the above content is my brief summary of the application of SPE solid phase extraction technology in water quality analysis, hoping to provide effective help for the majority of environmental analysts.