Mass intensity

Reduce the mass intensity per unit of service of the product. 

When identifying possible areas for innovation the seven dimensions provide a useful checklisf. Is if possible to deliver the user needs through improving durability Have we paid enough attention to the potential in reducing the mass intensity ... 

Mass intensity. The idea behind focusing on the mass intensity of the product or service is dematerialisation using less physical material to produce the required service. 

Yield and other mass-related metrics such as atom economy, reaction mass efficiency and mass intensity have been examined by Constable et al with regard to their significance concerning greenness and costs. The importance of using a (product) concentration term, which can be mass intensity or mass index, is additionally emphasized by Laird et al This is in compliance with Winterton, who in his twelve more green chemistry principles demands the establishment of full mass balances. 

Some specific metrics for mass have been found to be useful and are described elsewhere. In addition to reaction mass efficiency described elsewhere and in Chapter 4, a useful metrics is Mass Intensity, defined as ... 

Mass Intensity may also be expressed as a percentage by taking the inverse and multiplying by 100. This metric is also known as mass productivity or mass efficiency and provides an indication of how much of the input mass, expressed as a percentage, is integrated into a final, saleable product (how much of what we buy ultimately produces a profit). This is perhaps valuable for its shock value and ease of interpretation, especially for non-technical business people. 

Evaluation of each step of the existing route with respect to yield, productivity, efficiency, waste generation (PMI process (product) mass intensity) and solvent use was carried out and a number of potential areas for improvement were identified as summarized below ... 

Table II. Relative mass intensities evolved from the 1 4 chloride complex at three temperatures during thermal decomposition in the mass spectrometer. Nominal temperature values are given.

A quantitative correlation between the charges under the current and mass intensity signals can be carried out as suggested by Heitbaum and Wolter [11]. The magnitude of the mass intensity response depends not only on the electrochemical properties of the system under study but also on the permeability of the electrode to the volatile products in addition to mass spectrometer parameters. A calibration of the actual experimental setup is therefore necessary. The proportionality between mass intensity (MI), and faradaic current (/) can be formulated as follows ... 

Eq. (1.1) can be written in terms of the charges Q, and QMI obtained by integration of current and mass intensity signals ... 

A flow cell-procedure was then applied. The experiment consisted of (a) adsorption of methanol (in a solution containing deuterated methanol and light hydrogen base electrolyte), (b) solution exchange with base electrolyte and (c) application of two potential steps, one of short duration to oxidize the adsorbed residue and then a second one in the negative direction to reduce the ions H+ and/or D+ formed. During this time the mass intensity signals for HD, (m/e = 3) and for COz (m/e = 44) were... 

In Fig. 2.13 the mass intensities for carbon dioxide (m/e = 44) and methyl formate (m/e = 60) during a potential scan are given. While the signal for C02 follows the current pattern in the whole potential range that for HCOOCH3 does not. This indicates the existence of parallel pathways. Methyl formate was also detected as an electrolysis product in long duration experiments [66],... 

Exchange reactions between bulk and adsorbed substances can be studied by on-line mass spectroscopy and isotope labeling. In this section the results on the interaction of methanol and carbon monoxide in solution with adsorbed methanol and carbon monoxide on platinum are reported [72], A flow cell for on-line MS measurements (Fig. 1.2) was used. 13C-labeled methanol was absorbed until the Pt surface became saturated. After solution exchange with base electrolyte a potential scan was applied. Parallel to the current-potential curve the mass intensity-potential for 13C02 was monitored. Both curves are given in Fig. 3.1a,b. A second scan was always taken to check the absence of bulk substances. 

Fig. 3.1. Current (a), and mass intensity for 13COz production (b) during the potentiodynamic oxidation of methanol adsorbate (flow cell procedure, ad = 0.2 V RHE, see text). Scan rate 10 mV/s.

Fig. 3.3. Current and mass intensity signal showing the effect of the interaction of bulk 12CO with 13C-methanol adsorbate (flow cell procedure), (a) Current due to the oxidation of methanol and CO adsorbates, (b) Mass intensity for 12C02 due to COad, (c) mass intensity for 13C02 (due to rest of adsorbed methanol.

After adsorption of methanol at 0.4 V and electrolyte exchange with base solution to eliminate bulk methanol (flow cell), a step to potentials between 0.25 V and 0.6 V was applied, then Sn(IV) or Sn(II) was added and the C02 mass intensity signal was monitored. 

The current-time response of the system during Sn(Il) addition presents the same features as the mass intensity-time curve. For comparison the i-t curve for a blank experiment (only adsorbed methanol being present, no tin addition) is also shown in Fig. 4.6a. The observed response is not simply the sum of the individual responses of Sn(II) (Fig. 4.2b) and adsorbed methanol (see dashed curve in Fig. 4.6a), to the applied potential step. 

Fig. 4.7. Current (a) and mass intensity (b) voltammograms for methanol adsorbate oxidation without tin (dashed line) and with tin (full line). Base electrolyte dotted line. The voltammograms were recorded after applying a potential step to E0, = 0.475 V during 15 min.

Upon completion of the ProteinTrawler program, the text hie contains a cumulative hst of all the protein masses that were observed upon deconvolution of the individual summed spectra. This text hie records mass, intensity, and retention time. The retention time information is held in the text hie for... 

Figure 5. Mass intensities v.v. time using Fes(MoOt)3/Mo03 at 270°. Curve numbers indicate mass. Key 40, Ar/20 30, CHsO 31, CH3OH and 18, HtO.

Figure 5. TAP mass intensity versus tine curve comparing the tine sequence of formation of nethylanine versus the diffusion of reactant oxygen.

Fig. 15.22 On-line REMPI-TOFMS (at 266 nm) analysis of roast gas while roasting 80 g Ara-bica coffee, a The full-time-mass-intensity three-dimensional plot as recorded during roasting, b A time-intensity cross-section from a at a fixed time (medium roast level). The three phenolic VOCs, phenol (m/z 94), giraiacol (m/z 124) and 4-vinylguaiacol (150 m/z), are efficiently ionised at 266 nm. In addition, firrfurylacohol (m/z 96), dihydroxybenzene (m/z 110), indol (m/z 117) and caffeine (m/z 194) were also detected. (Adapted from [203])...

The Green Chemistry Institute (GCl) Pharmaceutical Roundtable has used the Process Mass Intensity (PMl) [12], defined as the total mass used in a process divided by the mass of product (i.e. PMl = E factor -i- 1) to benchmark the environmental acceptability of processes used by its members (see the GCl website). The latter include several leading pharmaceutical companies (Eh Lilly, GlaxoSmithKline, Pfizer, Merck, AstraZeneca, Schering-Plow, and Johnson Johnson). The aim was to use this data to drive the greening of the pharmaceutical industry. We believe, however, that the E factor is to be preferred over the PMl since the ideal E factor of 0 is a better reflection of the goal of zero waste. 

Different variahons on E factor have been proposed and used in the pharma-ceuhcals industry (for example, mass intensity, mass productivity [6], and process mass intensity [21]). Each of these has the aim of greening pharmaceutical processes by highlighting the amount of material used in a process, either when... 

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