A vacuum ultraviolet ion source (VUV-IS) for iodide–chemical ionization mass spectrometry: a substitute for radioactive ion sources

A new ion source (IS) utilizing vacuum ultraviolet (VUV) light is developed and characterized for use with iodide–chemical ionization mass spectrometers (I−-CIMS). The VUV-IS utilizes a compact krypton lamp that emits light at two wavelengths corresponding to energies of ∼10.030 and 10.641 eV. The VUV light photoionizes either methyl iodide (ionization potential, IP = 9.54 ± 0.02 eV) or benzene (IP = 9.24378 ± 0.00007 eV) to form cations and photoelectrons. The electrons react with methyl iodide to form I−, which serves as the reagent ion for the CIMS. The VUV-IS is characterized by measuring the sensitivity of a quadrupole CIMS (Q-CIMS) to formic acid, molecular chlorine, and nitryl chloride under a variety of flow and pressure conditions. The sensitivity of the Q-CIMS, with the VUV-IS, reached up to ∼700 Hz pptv−1, with detection limits of less than 1 pptv for a 1 min integration period. The reliability of the Q-CIMS with a VUV-IS is demonstrated with data from a month-long ground-based field campaign. The VUV-IS is further tested by operation on a high-resolution time-of-flight CIMS (TOF-CIMS). Sensitivities greater than 25 Hz pptv−1 were obtained for formic acid and molecular chlorine, which were similar to that obtained with a radioactive source. In addition, the mass spectra from sampling ambient air was cleaner with the VUV-IS on the TOF-CIMS compared to measurements using a radioactive source. These results demonstrate that the VUV lamp is a viable substitute for radioactive ion sources on I−-CIMS systems for most applications. In addition, initial tests demonstrate that the VUV-IS can be extended to other reagent ions by the use of VUV absorbers with low IPs to serve as a source of photoelectrons for high IP electron attachers, such as SF6-.

The influence of bleaching scheme technology on the content of total and bound chlorine in cellulose

Наблюдается ужесточение требований по содержанию хлора в целлюлозе для санитарно-гигиенических изделий и ряда других целей. Содержание хлора в целлюлозе зависит от применяемой схемы отбелки. В процессе отбелки с применением молекулярного хлора, диоксида хлора или гипохлорита натрия небольшая часть соединений хлора присутствует в целлюлозном волокне. На большинстве современных предприятий применяется технология ECF, где в качестве альтернативы молекулярному хлору на одной или нескольких ступенях используются диоксид хлора (ClO2) или гипохлорит натрия (NaClO). Также существует технология отбелки TCF, которая позволяет полностью отказаться от применения хлорсодержащих агентов путем использования только кислородсодержащих реагентов, таких как кислород, пероксид водорода, озон. Применение полностью бесхлорных технологий ограничено в виду высокой себестоимости продукции при сравнительных качественных характеристиках продукции. Проведен анализ образцов целлюлозы различных производителей. Определение содержания общего хлора и органически связанного хлора осуществлялось путем сжигания пробы целлюлозы при температуре от 950 до 1000 С. Анализ образцов целлюлозы российских заводов показал, что в целлюлозе, полученной с использованием схем отбелки КЩОД0ЩП1Д1ЩП2Д2К и Д0ЩОПД1ЩПД2К, содержание хлора в готовой продукции меньше всего. Это может объясняться тем, что кислородно-щелочная обработка позволяет эффективно снизить содержание лигнина. Низкое содержание последнего позволяет сократить количество используемого диоксида хлора на стадиях Д. По совокупности предъявляемых к целлюлозе свойств и экономических показателей наиболее приемлемыми являются схемы отбелки с оптимизированными расходами диоксида хлора и пероксида водорода, озона без использования молекулярного хлора (ECF-light). Они позволяют достичь низкого содержания соединений хлора в целлюлозе, близкого к технологии TCF. There is a tightening of requirements for the content of chlorine in cellulose for sanitary products and a number of other purposes. The chlorine content in cellulose depends on the bleaching scheme used. In the bleaching process using molecular chlorine, chlorine dioxide or sodium hypochlorite, a small part of the chlorine compounds is replaced on cellulose fiber. Most modern plants use ECF technology, where, as an alternative to molecular chlorine, chlorine dioxide (ClO2) or sodium hypochlorite (NaClO) is used at one or several stages. There is also TCF bleaching technology, which allows you to completely abandon the use of chlorine-containing agents by using only oxygen-containing reagents such as oxygen, hydrogen peroxide, ozone. The use of completely chlorine-free technologies is limited in view of the high cost of production with comparative qualitative characteristics of the products. Pulp samples from various manufacturers were analyzed. The determination of total chlorine and organically bound chlorine was carried out by burning a cellulose sample at a temperature of from 950 to 1000 C. Analysis of cellulose samples from Russian plants showed that in the pulp obtained using the bleaching scheme O1D0EP1D1EP2D2A and D0EOPD1EPD2A bleaching schemes, the chlorine content in the finished product is the least. This can be explained by the fact that oxygen-alkaline delignification can effectively reduce the lignin content. The low content of the latter makes it possible to reduce the amount of chlorine dioxide used in stages D. According to the combination of properties and economic indicators presented to cellulose, bleaching schemes with optimized consumption of chlorine dioxide and hydrogen peroxide, ozone without the use of molecular chlorine (ECF-light) are most acceptable. It allows to achieve a low content of chlorine compounds in cellulose, close to TCF technology.

A Vacuum Ultraviolet Ion Source (VUV-IS) for Iodide-Chemical Ionization Mass Spectrometry: A Substitute for Radioactive Ion Sources

A new ion source (IS) utilizing vacuum ultraviolet (VUV) light is developed and characterized for use with iodide-chemical ionization mass spectrometers (I−-CIMS). The VUV-IS utilizes a compact krypton lamp that emits light in two wavelength bands corresponding to energies of ~10.0 and 10.6 eV. The VUV light photoionizes either methyl iodide (ionization potential, IP = 9.54 ± 0.02 eV) or benzene (IP = 9.24378 ± 0.00007 eV) to form cations and photoelectrons. The electrons react with methyl iodide to form I− which serves as the reagent ion for the CIMS. The VUV-IS is characterized by measuring the sensitivity of a quadrupole CIMS (Q-CIMS) to formic acid, molecular chlorine, and nitryl chloride under a variety of flow and pressure conditions. The sensitivity of the Q-CIMS, with the VUV-IS, reached up to ~700 Hz pptv−1, with detection limits of less than 1 pptv for a one minute integration period. The reliability of the Q-CIMS with a VUV-IS is demonstrated with data from a month long ground-based field campaign. The VUV-IS is further tested by operation on a high resolution time-of-flight CIMS (TOF-CIMS). Sensitivities greater than 25 Hz pptv−1 were obtained for formic acid and molecular chlorine, which were similar to that obtained with a radioactive source. In addition, the mass spectra from sampling ambient air was cleaner with the VUV-IS on the TOF-CIMS compared to measurements using a radioactive source. These results demonstrate that the VUV lamp is a viable substitute for radioactive ion sources on I−-CIMS systems for most applications. In addition, the VUV-IS can likely be extended to other reagent ions, such as SF6− which are formed from high IP electron attachers, by the use of absorbers such as benzene to serve as a source of photoelectrons.

Halogenating Enzymes for Active Agent Synthesis: First Steps Are Done and Many Have to Follow

Halogens can be very important for active agents as vital parts of their binding mode, on the one hand, but are on the other hand instrumental in the synthesis of most active agents. However, the primary halogenating compound is molecular chlorine which has two major drawbacks, high energy consumption and hazardous handling. Nature bypassed molecular halogens and evolved at least six halogenating enzymes: Three kind of haloperoxidases, flavin-dependent halogenases as well as α-ketoglutarate and S-adenosylmethionine (SAM)-dependent halogenases. This review shows what is known today on these enzymes in terms of biocatalytic usage. The reader may understand this review as a plea for the usage of halogenating enzymes for fine chemical syntheses, but there are many steps to take until halogenating enzymes are reliable, flexible, and sustainable catalysts for halogenation.